JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
LAB MANUAL Lab Name : Thermal Engineering Lab-1
Lab Code : 6ME4-24
Branch : Mechanical Engineering
Year : 3rd Year
Department of Mechanical Engineering Jaipur Engineering College and Research Center, Jaipur (Rajasthan Technical University, KOTA)
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
INDEX
S.NO CONTENTS CO PAGE NO.
1 VISION/MISION i
2. PEO ii
3. POS iii
4. COS iv
5. MAPPING OF CO & PO iv
6. SYLLABUS v
7. BOOKS vi
8 INSTRUCTIONAL METHODS vi
9 LEARNING MATERIALS vi
10 ASSESSMENT OF OUTCOMES vi
11 INSTRUCTION SHEET vii
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
LIST OF EXPERIMENTS
(RTU SYLLABUS)
Exp:- 1 Objectives :- Study of working of four stroke petrol engine and four 1 stroke diesel engine with the help of cut section models
Exp:- 2 Objectives :- Study of working of two stroke petrol and two stroke 9 diesel engine with the help of cut section models Exp:-3 Objectives :- To draw valve timing diagram for a single cylinder diesel 14 engine Exp:-4 Objectives: - Study of various types of boilers 18
Exp:-5 Objectives: - Study of various types of mountings and accessories 35
Exp:-6 Objectives: - Demonstration of steering system and measurement of 43 steering geometry angles and their impact on vehicle performance
Exp:-7 Objectives: - Study of braking system with specific reference to types of 47 braking system, master cylinder, brake shoes Exp:-8 Objectives: - Study of transmission system including clutches, gear box 54 assembly and differential
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTER
Department of Mechanical Engineering
1.VISION AND MISSION
VISION OF DEPARTMENT OF MECHANICAL ENGINEERING
The Mechanical Engineering Department strives to be recognized globally for outcome based technical knowledge and to produce quality human resource, who can manage the advance technologies and contribute to society.
MISSION OF DEPARTMENT OF MECHANICAL ENGINEERING
• To impart quality technical knowledge to the learners to make them globally competitive mechanical engineers. • To provide the learners ethical guidelines along with excellent academic environment for a long productive career. • To promote industry-institute relationship.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
2. PROGRAM EDUCATIONAL OBJECTIVES
1. To enrich students with fundamental knowledge, effective computing, problem solving and communication skills enable them to have successful career in Information Technology. 2. To enable students in acquiring Information Technology's latest tools, technologies and management principles to give them an ability to solve multidisciplinary engineering problems. 3. To impart students with ethical values and commitment towards sustainable development in collaborative mode. 4. To imbibe students with research oriented and innovative approaches which help them to identify, analyze, formulate and solve real life problems and motivates them for lifelong learning. 5. To empower students with leadership quality and team building skills that prepare them for employment, entrepreneurship and to become competent professionals to serve societies and global needs
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
3. PROGRAM OUTCOMES
1. Engineering Knowledge: Apply the knowledge of mathematics, science, engineering fundamentals, and an engineering specialization to the solution of complex engineering problems in IT. 2. Problem analysis: Identify, formulate, research literature, and analyze complex engineering problems reaching substantiated conclusions using first principles of mathematics, natural sciences, and engineering sciences in IT. 3. Design/development of solutions: Design solutions for complex engineering problems and design system components or processes that meet the specified needs with appropriate consideration for the public health and safety, and the cultural, societal, and environmental considerations using IT. 4. Conduct investigations of complex problems: Use research-based knowledge and research methods including design of experiments, analysis and interpretation of data, and synthesis of the information to provide valid conclusions using IT. 5. Modern tool usage: Create, select, and apply appropriate techniques, resources, and modern engineering and IT tools including prediction and modeling to complex engineering activities with an understanding of the limitations in IT. 6. The engineer and society: Apply reasoning informed by the contextual knowledge to assess societal, health, safety, legal and cultural issues and the consequent responsibilities relevant to the professional engineering practice using IT. 7. Environment and sustainability: Understand the impact of the professional engineering solutions in societal and environmental contexts, and demonstrate the knowledge of, and need for sustainable development in IT. 8. Ethics: Apply ethical principles and commit to professional ethics and responsibilities and norms of the engineering practice using IT. 9. Individual and team work: Function effectively as an individual, and as a member or leader in diverse teams, and in multidisciplinary settings in IT. 10. Communication: Communicate effectively on complex engineering activities with the engineering community and with society at large, such as, being able to comprehend and write effective reports and design documentation, make effective presentations, and give and receive clear instructions.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
11. Project Management and finance: Demonstrate knowledge and understanding of the engineering and management principles and apply these to one’s own work, as a member and leader in a team, to manage IT projects and in multidisciplinary environments. 12. Life –long Learning: Recognize the need for, and have the preparation and ability to engage in independent and life-long learning in the broadest context of technological changes needed in IT.
PSO-Program Specific Objectives:
PSO1.Apply the knowledge of material science, manufacturing, design and analysis to implement the various concepts of vehicle . PSO2.Apply the knowledge of 3D printing technology in design and development of prototype.
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JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
4.COURSE OUTCOMES
THERMAL ENGINEERING LAB-I [6ME4-24]
Class: VI Sem. B.Tech. Branch: Mechanical Engineering Schedule per Week Practical Hrs.: 3 Examination Time = Two (3) Hours Maximum Marks = 75 [Sessional/Mid-term (45) & End-term (30)]
On successful completion of this course the students will be able to:
CO1-To identify the working of major systems used in conventional and modern engines.
CO2-To analyze concept of thermal engineering systems and applications of thermal systems.
5. MAPPING OF COs with POs
PSO COURSE PROGRAM OUTCOMES OUTCOME 1 2 S 1 2 3 4 5 6 7 8 9 10 11 12 3 1 1 0 0 1 2 1 0 1 0 2 2 0 I 3 2 1 3 1 1 1 0 0 1 1 1 1 1 II
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
6.SYLLABUS
THERMAL ENGINEERING LAB-I [6ME4-24]
Class: VI Sem. B. Tech. Evaluation Branch: ME Examination Time=Two (3) Hours Schedule per week Maximum Marks =75 Practical Hrs: (3 Hours) [Sessional/Mid-term(45)&End-term(30)]
S.N. NAME OF EXPERIMENT 1 Study of working of four stroke petrol engine and four stroke diesel engine with the help of cut section models 2 Study of working of two stroke petrol and two stroke diesel engine with the help of cut section models 3 To draw valve timing diagram for a single cylinder diesel engine. 4 Study of various types of boilers 5 Study of various types of mountings and accessories 6 Demonstration of steering system and measurement of steering geometry angles and their impact on vehicle performance 7 Study of braking system with specific reference to types of braking system, master cylinder, brake shoes 8 Study of transmission system including clutches, gear box assembly and differential
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
6ME4-24 Thermal Engineering Lab- 1
Class: VI Sem. B.Tech. Branch: Mechanical Engineering Schedule per Week Practical Hrs.: 3 Examination Time = Two (3) Hours Maximum Marks = 75 [Sessional/Mid-term (45) & End-term (30)]
Outcomes: At the end of the course, the student will be able to:
CO1-To identify the working of major systems used in conventional and modern engines.
CO2-To analyze concept of thermal engineering systems and applications of thermal systems.
7.BOOKS:-
7.1 Text books:- Mathur & Sharma, Internal Combustion Engines, Dhanpat Rai & Sons 7.2 Reference Books:-
1.) Ganeshan, V., Internal Combustion Engine, Tata Mcgraw Hill 2.) R. Yadav, IC Engine, Central Publishing House, Allahabad 3.) John, B, Heyword, Internal Combustion Engines Fundamentals, Mcgraw Hill
8. INSTRUCTIONAL METHODS:- 8.1. Direct Instructions: I. Black board presentation 8.2. Interactive Instruction: I. Algorithms
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
8.3. Indirect Instructions: I. Problem solving 9. LEARNING MATERIALS:- 9.1. Text/Lab Manual 10. ASSESSMENT OF OUTCOMES:- 1.End term Practical exam (Conducted by RTU, KOTA) 2.Daily Lab interaction.
11. INSTRUCTIONS SHEET
We need your full support and cooperation for smooth functioning of the lab.
DO’s 1. Please switch off the Mobile/Cell phone before entering lab. 2. Arrange all the peripheral and seats before leaving the lab. 3. Keep the bag outside in the racks. 4. Enter the lab on time and leave at proper time. 5. Maintain the decorum of the lab. 6. Utilize lab hours in the corresponding experiment. 7. Laboratory uniform, shoes & safety glasses are compulsory in the lab.
DON’TS 1. Don’t bring any external material in the lab. 2. Don’t make noise in the lab. 3. Don’t bring the mobile in the lab. If extremely necessary then keep ringers off. 4. Don’t enter in the lab without permission of lab Incharge. 5. Don’t litter in the lab. 6. Don’t carry any lab equipments outside the lab. 7. Do not leave the experiments unattended while in progress.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
8. Do not crowd around the equipment’s & run inside the laboratory.
BEFORE ENTERING IN THE LAB 1. All the students are supposed to prepare the theory regarding the next experiment 2. Students are supposed to bring the practical file and the lab copy. 3. Previous practical should be written in the practical file. 4. Any student not following these instructions will be denied entry in the lab.
WHILE WORKING IN THE LAB 1. Adhere to experimental schedule as instructed by the lab incharge. 2. Take responsibility of valuable accessories. 3. Concentrate on the assigned practical . 4. If anyone caught red handed carrying any equipment of the lab, then he will have to face serious consequences.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
EXPERIMENT NO. 1
AIM : - To study working of four stroke petrol engine and four stroke diesel engine with the help of cut section models
THEORY: -
Four Stroke Petrol Engine:
The four-stroke petrol engine works on Otto cycle. The actual and ideal cycles are shown in p-v diagram.
Process 1-2:- suction stroke, air fuel mixer is drawn into the cylinder. Inlet valve remains open, exhaust valve remains closed.
Process 2-3:- compression stroke, compresses air-fuel mixer to high pressure and temperature. At the end of stroke ignition commences. During compression both valves remain closed.
Process 3-4: Addition of heat/ combustion fuel at constant volume.
Process 4-5:- expansion stroke, thus power is obtained during this stroke, the exhaust valve opens at 5.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Process 5-6:- Rejection of heat takes place at constant volume and exhaust gases are released and pressure falls.
Process 2-1:- exhaust stroke, sweeps out the burnt gases from the cylinder.
Engine structure: it consists of a cylinder block, cylinder head and a crank case.
Four strokes of petrol engine
FUEL SUPPLY & EXHAUST SYSTEM:-
The fuel comes from fuel tank then it passes through control valve and goes into the carburetor and air comes from atmosphere through air filter and it mixes with fuel as required and this air fuel mixer then goes to the cylinder. The burnt gases are exhausted to atmosphere through the silencer.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Fuel supply and exhaust system
LUBRICATION SYSTEM:-
Oil is pumped from the oil tank/sump around the engine by the unique double-ended eccentric plunger type oil pump assembly, located in the right-hand crankcase cover, just above the oil filter housing. The pump plungers are driven by a spindle, which itself is driven by the crankshaft worm gear. The oil pump features two main compartments, one at the front and one at the rear.
The rear compartment is a feed pump. This draws oil from the oil tank, pumps it through the oil filter and timing shaft and along the internally drilled crankshaft directly to the big-end bearing. Oil is then flung from the rotating flywheels, splash-lubricating the main bearings, cylinder walls, the underside of the piston and the small-end bearing. The front compartment is a scavenging pump, with a greater flow rate than the feed pump. The scavenging pump sucks oil from the sump, where it gathers after lubricating the big-end bearing, sending oil to the rockers through the external oil pipe. Under gravity, oil drains down through the push rod tubes to the timing chest. From the timing chest, oil finds its way back into the oil tank/sump through a strategically placed drilling, leaving the timing chest about ¾ full.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
COOLING SYSTEM:-
In this engine air cooling system is used as seen on the engine an extended surface area provided on the engine known as fins that takes away the engine heat to the atmospheric air that comes in contact with the engine when the vehicle is in motion.
Spark plug
Fins
Air cooling
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
PRESTARTING INSTRUCTIONS:-
When the engine is in daily use inspect it daily always before starting.
Engine oil level: inspect the oil level and add oil of proper viscosity if required.
Fuel: check the fuel supply.
Unload the engine.
STARTING AND STOPPING THE ENGINE:-
STARTING:-
Open the throttle valve to 1/3 opening. See the clutch gear shift lever or power take off lever in neutral position.Turn on the ignition switch and press the cranking lever until the engine starts using decompression lever.
After the engine start watch the oil pressure gauge. If the oil pressure does not register for about 10 seconds stop the engine and investigate.
STOPPING:-
To stop the engine, close the throttle valve and disengage the clutch.
Allow the engine to run at ideal speed for a few minutes. Close the throttle and turn off ignition.
Four Stroke DIESEL CYCLE:
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
(Ideal P-V Diagram) (Actual P-V Diagram)
Process 0-1: during the first out stroke of the piston, charge of only air is drawn in the cylinder through the inlet valve. The pressure inside the cylinder is below atmospheric. Inlet valve remains open, exhaust valve remains closed.
Process 1-2: This is in stroke of the piston both the valves are closed .the charge is to compress to clearance volume. Compression ratio ranges from 12 to 22 which cause the rise in pressure and temperature of air sufficient to self ignite the atomized fuel.
Process 2-3:- heat addition / fuel injection at constant pressure.
Process 3-4: At some point in the stroke injection of fuel stops. This point is known as cut off point. The products of combustion are now expanded producing power. both valves remains closed.
Process 4-1:- heat rejection at constant volume.
Process 1-0: The exhaust takes place due to in stroke of piston and the exhaust valve remains open.
AIR FUEL AND EXHAUST SYSTEM OF A DIESEL ENGINE:-
Air is sucked from the atmosphere and then it passes through the air filter so any impurity get collected in the filter and clean air is now allowed to enter the cylinder.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Now fuel from the fuel tank passes through the filter and then fuel is pumped by fuel pump and injector in the atomized form or spray in the cylinder at the end of compression stroke.
Air-fuel supply and exhaust system
LUBRICATION SYSTEM: -
In this system, the engine component which are subjected to very heavy load are lubricated under forced pressure, such as main bearing connecting rod bearing and camshaft bearing. The rest of the parts like cylinder liners, cans, tappets etc, are lubricated by splashed oil.
Oil is pumped from the oil tank/sump around the engine by the unique eccentric plunger type oil pump assembly. The pump plungers are driven by a spindle, which itself is driven by the crankshaft worm gear. This draws oil from the oil tank/sump, pumps it through the oil filter and timing shaft and along the internally drilled crankshaft directly to the big-end bearing. Oil is then flung from the rotating flywheels, splash-lubricating the main bearings, cylinder walls, the underside of the piston and the small-end bearing.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Lubrication System
COOLING SYSTEM: - In this engine water cooling system is used.
The cold water comes from the water well/pound and it passes through the bottom of the water jacket and it flows upward direction of the engine cylinder. While water flowing through the engine cylinder head and exhaust valve, heat is absorbed by flowing water in the jacket.
The hot water then exits from the top of the water jacket and it goes to the cooling tower and this cycle is continues.
Cooling System
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
STARTING AND STOPPING OF DIESEL ENGINE:
Follow these steps to start the engine.
1. Unload the engine through clutch (in this engine dynamometer is disengaged from the engine).
2. Check the oil level and water circuit.
3. Operate the decompression levers to open the exhaust valves and crank the engine by a lever when the flywheel stores sufficient energy.
4. Release the decompression lever such that engine completes its cycle of operation and get started and starts producing power remove the lever.
To stop the diesel engine:
1. Unload the engine.
2. Pull the rack of fuel injection pump to stop the fuel supply.
3. When no fuel is supplied no power is generated and the engine friction helps to stop the engine.
Application: 4-stroke SI & CI engine are used in automobile e.g. car, bus, suv and heavy vehicles.Four-stroke engines, on the other hand, produce more torque at lower rpm, generally providing greater equipment durability than high-revving two-stroke engines, while also providing greater fuel efficiency and lower emissions. For these reasons, four-stroke engines are ideal in applications such as motorcycles, ATVs and personal watercraft.
Expected Outcome: We have successfully done the study of working of four stroke petrol engine and four stroke diesel engine with the help of cut section models.
Comment by Student:
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Viva Questions
1. What is I.C Engine?
2. What do you mean by four stroke engine?
3. What is working of four stroke petrol engine?
4. What are the differences in petrol and diesl engine?
5. What is working of four stroke diesl engine?
6. What is the purpose of cam?
7. What is flywheel?
8. What is stroke?
9. Why clearance is provided?
10. Why piston rings are used?
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
EXPERIMENT NO. 2
AIM : - To study working of two stroke petrol and two stroke diesel engine with the help of cut section models.
THEROY: -
Two Stroke Petrol Engine:
In two stroke engine the cycle is completed in two strokes of piston (i.e. one revolution of the crank shaft) namely the compression stroke and power stroke.
The work of the inlet and exhaust stroke is done by a crankcase scavenging system while the engine piston is near the bottom dead center position.
In a 2-Stroke engine, the filling process is accompanied by the charge compressed in a crank case or by a blower. The induction of compressed charge moves out the product of combustion through exhaust ports. Therefore, no piston stroke is required. Out of these 2-strokes, one stroke is for compression of fresh charge and second for power stroke.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
The charge conducted into the crank case through the spring loaded valve when the pressure in the crank case is reduced due to upward motion of piston during the compression stroke. After the compression & ignition expansion takes place in usual way. During the expansion stroke the charge in crankcase is compressed. Near the end of the expansion stroke, the piston uncovers the exhaust ports and the cylinder pressure drops to atmosphere pressure as combustion produced leave the cylinder.
LUBRICATION SYSTEM: - In this engine mist lubrication system is employed.
This system is used for two stroke engine. Most of these engine are crank charged i.e. they employ crankcase compression and thus are not suitable for crankcase lubrication.These engines are lubricated by adding 2to3% oil in the fuel tank.
The oil and fuel mixture is induced through carburetor. The gasoline is vaporized and the oil in the form of mist goes via crankcase.
The oil which impinges on the crankcase walls lubricates the main and connecting rod bearings and rest of the oil which passes on the cylinder and scavenging periods lubricate the piston, piston rings and cylinder.
FUEL SUPPLY& EXHAUST SYSTEM: -
The fuel comes from fuel tank then it passes through control valve and goes into the carburetor and air comes from atmosphere and it passes through air filter so any impurity in the incoming air should be clean and then it mixes with the fuel and as required this air fuel mixer then goes to the cylinder.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Air-fuel supply and exhaust system
COOLING SYSTEM: -
In this engine air cooling system is used as seen on the engine an extended surface area provided on the engine known as fins that takes away the engine heat to the atmospheric air that comes in contact with the engine when the vehicle is in the motion.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Spark plug
Fins
Air cooling
PRESTARTING INSTRUCTIONS:-
When the engine is in daily use inspect it daily always before starting.
Engine oil level: inspect the oil level and add oil of proper viscosity if required.
Fuel: check the fuel supply.
Cooling system: Inspect the cooling system and add water or anti freeze as required.
Unload the engine.
STARTING AND STOPPING THE ENGINE:-
STARTING:-
Open the throttle valve to 1/3 opening. See the clutch gear shift lever or power take off lever in neutral position.
Turn on the ignition switch and press the cranking lever until the engine starts.
After the engine start watch the oil pressure gauge. If the oil pressure does not register for about 10 seconds stop the engine and investigate.
STOPPING:-
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JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
To stop the engine, close the throttle valve and disengage the clutch.
Allow the engine to run at ideal speed for a few minutes. Close the throttle and turn off ignition.
Two Stroke Diesel Engine :
In two stroke engines, the cycle is completed in one revolution of the crankshaft. In 2-stroke engine, the filling process is accomplished by the charge compressed in crankcase or by a blower. The induction of compressed charge moves out of the exhaust ports. Therefore, no piston strokes are required for these 2 operations. Two strokes are sufficient to complete the cycle one for compressing the fresh charge and other for expansion or power stroke.
1. Compression: - The air or charge is inducted into the crankcase through the spring loaded inlet valve when the pressure in crankcase is reduced due to upward motion of piston.
2. Expansion:- During this, the charge in the crankcase is compressed. At the end the piston uncovers the exhaust ports and cylinder pressure drops to the atmospheric pressure. Further movement of piston opens the transfer ports, permitting the slightest compressed charge in the crankcase to enter the engine cylinder.
Construction Details
1. Cylinder: - In it the piston makes a reciprocating process motion.
2. Piston: - It is a cylindrical component fitted into the cylinder forming the moving boundary of the combustion system. It fits into cylinder.
3. Combustion Chamber: - The space enclosed in the upper part of the cylinder, by the head and the piston top during the combustion process.
4. Inlet/ Outlet ports: - They are provided on the side of cylinder to regulate the charge coming in and out of cylinder.
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JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
5. Fuel Injector: - It injects the fuel in combustion chamber to initiate combustion process for power stroke.
6. Connecting Rod: - It interconnects crank shaft and the piston.
7. Fly Wheel: - The net torque imparted to the crankshaft during one complete cycle of operation of the engine fluctuates cow sing change in angular velocity of shaft. In order to achiever uniform torque an internal mass is attached to the output shaft & this is called as fly wheel.
Application:- Two-stroke engines are generally less expensive to build compared to four-stroke engines, and they are lighter and can produce a higher power-to-weight ratio. For these reasons, two-stroke engines are ideal in applications such as chainsaws, weed trimmers, outboard motors, off-road motorcycles and racing applications.2-stroke SI & CI engine are used in automobile e.g. two wheel vehicles.
Expected Outcome: We have successfully completed the study of two stroke petrol engine and two stroke diesel engine with the help of cut section model.
Comment by Student:
Viva Questions
1 What do you mean by two stroke engine? 2.What are the differences in 4 stroke & 2 stroke engine? 3. What is working of two stroke petrol engine? 4.What is working of two stroke diesel engine? 5. What are the differences in S.I and C.I engine? 6. How much power is produced as compare to 4 stroke? 7. Why lighter flywheel is used as compare to 4 stroke? 8. Where 2 stroke is preffered? 9. What is balancing? 10. What is transfer port?
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
EXPERIMENT NO. 3
Aim : To draw valve timing diagram for a single cylinder diesel engine.
Apparatus Required:
1. Four stroke cycle diesel engine
2. Measuring tape
3. Chalk
4. Piece of paper
Theory and Description:
The diagram which shows the position of crank of four stroke cycle engine at the beginning and at the end of suction, compression, expansion, and exhaust of the engine are called as Valve Timing Diagram.
The extreme position of the bottom of the cylinder is called “Bottom Dead Centre” [BDC].IN the case of horizontal engine, this is known as “Outer Dead Centre” [ODC]. The position of the piston at the top of the cylinder is called “Top Dead Centre” [TDC].In case of horizontal engine this is known as “Inner Dead Centre” [TDC].In case of horizontal engine this is known as “inner dead centre “[IDC]
Inlet Valve opening and closing:
In an actual engine, the inlet valve begins to open 5°C to 20 °C before the piston reaches the TDC during the end of exhaust stroke. This is necessary to ensure that the valve will be fully open when the piston reaches the TDC. If the inlet valve is allowed to close at BDC, the cylinder would receive less amount of air than its capacity and the pressure at the end of suction will be below the atmospheric pressure. To avoid this inlet valve is kept open for 25° to 40°after BDC.
Exhaust valve opening and closing:
Complete clearing of the burned gases from the cylinder is necessary to take in more air into the cylinder. To achieve this exhaust valve is opens at 35° to 45° before BDC and closes at 10° to 20° after the TCC. It is clear from the diagram, for certain period both inlet valve and exhaust
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JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
valve remains in open condition. The cranks angles for which the both valves are open are called as overlapping period. This overlapping is more than the petrol engine.
Fuel valve opening and closing:
The fuel valve opens at 10° to 15 °before TDC and closes at 15° to 20 ° after TDC . This is because better evaporation and mixing fuel.
Valve Timing Diagram:
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Formula:
Θ = S * 360°
πD Where, D=Circumference of the flywheel S= Distance of the valve opening or closing position marked on flywheel with respect to their dead centre.
Procedure :
1. Remove the cylinder head cover and identify the inlet valve, exhaust valve and piston of particular cylinder.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
2. Mark the BDC and TDC position of flywheel this is done by rotating the crank in usual direction of rotation and observe the position of the fly wheel, when the piston is moving downwards at which the piston begins to move in opposite direction. i.e. from down to upward direction. Make the mark on the flywheel with reference to fixed point on the body of the engine. That point is the BDC for that cylinder. Measure the circumference. That point is TDC and is diametrically opposite to the BDC.
3. Insert the paper in the tappet clearance of both inlet and exhaust valves
4. Slowly rotate the crank until the paper in the tappet clearance of inlet valve is gripped. Make the mark on fly wheel against fixed reference. This position represent the inlet valve open (IVO). Measure the distance from TDC and tabulate the distance.
5. Rotate the crank further, till the paper is just free to move. Make the marking on the flywheel against the fixed reference. This position represents the inlet valve close (IVC). Measure the distance from BDC and tabulate the distance.
6. Rotate the crank further, till the paper in the tappet clearance of exhaust valve is gripped. Make the marking on the flywheel against fixed reference. This position represents the exhaust valve open (EVO). Measure the distance from BDC and tabulate.
7. Then convert the measured distances into angle in degrees.
Application:Valve timing diagram is used to measure the position of valve opening and closing during the cycle.Valve opening and closing effect the entire peformance of engine. Expected Outcome: : The valve timing diagram for the given four stroke Diesel engine was drawn.
Comment by Student:
Viva Questions
1. What do you mean by the valve timing diagram of a Four stroke S.I. Engine. 2. What do you mean by the valve timing diagram of a Four stroke C.I. Engine. 3. What do you mean by the valve timing diagram of a Two stroke S.I. Engine.
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4. What do you mean by the valve timing diagram of a Two stroke C.I. Engine. 5. What are the values of intake and exhaust angle in four stroke S.I.engine? 6.What is the angle at which spark occurs? 7. When exhaust valve is open? 8. Whent exhaust valve is closed? 9. Why valve timing is necessary? 10. Which valve is big.?
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EXPERIMENT NO. 4
AIM: - To study various types of the Boilers.
Theory:-
Boiler: - A steam boiler is a closed vessel in which steam is produced from water by combustion of fuel.
Classification of Boiler: Boilers are classified on the basis of following-
1. According to contents in the Tube: a) Fire tube boiler: In fire tube boilers, the flue gases pass through the tube and water surround them.
B).Water tube boiler: In water tube boiler, water flows inside the tubes and the hot flue gases flow outside the tubes.
2. According to the pressure of steam:
A).Low pressure boiler: A boiler which generates steam at a pressure of below 80 bars is called low pressure boiler. Example-Cochran boiler, Lancashire boiler etc.
B).High pressure boiler: A boiler which generates steam at a pressure higher than 80 bar is called high pressure boiler. Example-Babcock and Wilcox boiler etc.
3. According to method of circulation of water:
A).Natural Circulation: In natural circulation boiler, circulation of water due to gravity or the circulation of water takes place by natural convection current produced by the application of heat, example-Babcock and Wilcox boiler, Lancashire boiler etc.
B).Forced Circulation: In the forced circulation boiler, circulation of water by a pump to increase the circulation. Example-Lamont boiler etc.
4. According to the Position of the furnace:
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A).Internally fired boilers: In this, the furnace is located inside the boiler shell. Example- Cochran, Locomotive and Lancashire boilers.
B).Externally fired boilers: In this, the furnace is located outside the boiler shell. Example- Babcock and Wilcox boiler etc. 5. According to the axis of shell: A).Vertical boilers: If the axis of the shell of boiler is vertical so the boiler is called as vertical boiler. B).Horizontal boilers: If the axis of the shell of boiler is horizontal so the boiler is called as Horizontal boilers.
C).Inclined boilers: If the axis of the shell of boiler is Inclined so the boiler is called as Inclined boiler. 1.Cochran Boiler: Cochran boiler is a vertical, multitubular fire tube, internally fired, natural circulation boiler.
Construction: Figure shows a Cochran boiler. It consists of a vertical cylindrical shell having a hemispherical top and furnace is also hemispherical in shape. The fire grate is arranged in the furnace and the ash pit is provided below the grate. A fire door is attached on the fire box. Adjacent to the fire box, the boiler has a combustion chamber which is lined with fire bricks. Smoke or fire tubes are provided with combustion chamber. These tubes are equal in length and arranged in a group with wide space in between them. The ends of these smoke tubes are fitted in the smoke box. The chimney is provided at the top of the smoke box for discharge of the gases to the atmosphere. The furnace is surrounded by water on all sides except at the opening for the fire door and the combustion chamber. The smoke tubes are also completely surrounded by water. Different boiler mountings and accessories are located at their proper place. Working: The hot gas produced from the burning of the fuel on the grate rises up through the flue pipe and reaches the combustion chamber. The flue gases from the combustion pass through the fire tubes and the smoke box and finally are discharged through the chimney. The flue gases during their travel from fire box to the chimney gives heat to the surrounding water to generate Steam.
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Cochran Boiler 2.Babcock and Wilcox Boiler:
Babcock and Wilcox boiler is a horizontal shell, multitubular, water tube, externally fired, natural circulation boiler.
Construction: Figure shows the details of a Babcock and Wilcox water tube boiler. It consists of a drum mounted at the top and connected by upper header and down take header. A large number of water tubes connect the uptake and down take headers. The water tubes are inclined at an angle of 5 to 15 degrees to promote water circulation. The heating surface of the unit is the outer surface of the tubes and half of the cylindrical surface of the water drum which is exposed to flue gases. Below the uptake header the furnace of the boiler is arranged. The coal is fed to the chain grate stoker through the fire door.
There is a bridge wall deflector which deflects the combustion gases upwards. Baffles are arranged across the water tubes to act as deflectors for the flue gases and to provide them with gas passes. Here, two baffles are arranged which provide three passes of the flue gases. A chimney is provided for the exit of the gases. A damper is placed at the inlet of the chimney to regulate the draught. There are superheating tubes for producing superheated steam.
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Connections are provided for other mounting and accessories.
Working: The hot combustion gases produced by burning of fuel on the grater rise upwards and are deflected by the bridge wall deflector to pass over the front portion of water tubes and drum. By this way they complete the first pass. With the provision of baffles they are deflected downwards and complete the second pass.
Again, with the provision of baffles they rise upwards and complete the third pass and finally come out through the chimney. During their travel they give heat to water and steam is formed. The flow path of the combustion gases is shown by the arrows outside the tubes. The circulation of water in the boiler is due to natural circulation set-up by convective currents (due to gravity). Feed water is supplied by a feed check valve.
The hottest water and stem rise from the tubes to the uptake header and then through the riser it enters the boiler drum. The steam vapors escape through the upper half of the drum. The cold water flows from the drum to the rear header and thus the cycle is completed. To get superheated steam, the steam accumulated in the steam space is allowed to enter into the super heater tubes which are placed above the water tubes. The flue gases passing over the flue tubes produce superheated steam. The steam thus superheated is finally supplied to the user through a steam stop valve.
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Babcock and Wilcox Boiler
3.Lancashire Boiler
Lancashire Boiler is a horizontal type and stationary fire tube boiler. Before we go further, let’s know the person who invented this boiler. Lancashire Boiler was invented in the year 1844, by William Fairbairn. But his patent was for the method of firing the furnaces alternately. Generally, flue gases pass through the fire tube. It is present inside the boiler shell or body and for this reason, it is a fire tube boiler. Lancashire Boiler is an internally fired boiler because the furnace uses to present inside the boiler. This boiler generates low-pressure steam and it is a natural circulation boiler.
Basic Principle of Lancashire Boiler:
This boiler consists of a horizontal cylindrical shell filled with water. It uses to surround by two large fire tubes. Heat exchanging is the basic working principle of this boiler. It is has a shell and tube type heat exchanging system. Generally, the flue gases pass through the fire tubes and water flows through the shell. By this way, the heat is transfer from flue gases to the water. It is a low pressure, internally fired,
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natural water circulation boiler. That’s means this boiler uses the natural current to flow the water inside the boiler during its operation.
Construction of Lancashire Boiler: Generally, this boiler consists of a large drum. Its diameter can be up to 4-6m and length can be up to 9- 10m. Normally this drum consists of two fire tube and its diameter is up to 40 percent of the diameter of the shell. For this boiler, the water drum is placed over the bricks works. Where three spaces are created between the drum and the bricks wall. First one is at the bottom and the second one is insides. When the boiler is operational, then the flue gases pass through the fire tubes and side and bottom space.
The great thing for this boiler is that water level inside the drum is always above the side channels of flue gases. For this reason, more heat can transfer to the water. But the water drum is not completely filled
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with water. Boiler water drum usually half filled with water from the bottom section of drum and the upper half space is for generated steam. Generally, the Furnace of this boiler is located at one end of fire tubes which is inside the boiler.
Then low brick is present at the grates and it makes an obstacle to unburned fuel and ash to flow in fire tubes during operation. Lancashire Boiler also consists of other necessary mountings and accessories. Those are economizer, safety valve, superheater, water gauge, pressure gauge, and some other parts. All are for the better performance of this boiler.
Working of Lancashire Boiler: For this boiler, hard fuel is burned at the grate. Like a water tube boiler, water usually pumped into the shell through the economizer. This operation is performing by a water pump. This process increases the temperature of the water before further action. Then the fire tube of this boiler is fully immersed into the water. Generally, hard fuel is fired at the grate. This is the first heating process and it produces flue gases. Then generated flue gases pass through the fire tube. This flue gas can pass from one side to another side, inside the boiler fire tube. Boiler fire tubes can transfer 80 to 90 percent of total heat to the water. Then the backward flue gases pass from the bottom passage of this boiler. By this process, heat from flue gases can transfer another 8 to 10 percent heat to water.
After this process remaining flue gases pass from the side passage of the boiler. It can transfer another 6 to 8 percent of heat to water. Brick wall creates those heat transfer channel. Brick wall also works as a heat insulator. There is some damper on each side channel to regulate the air flow. When water absorbs heat then it becomes steam. Steam stored at the top section of the shell. Then an anti priming pipe
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separates the generated steam from the water. Then a steam stop valve received generated steam for various purposes. Then this steam is transfer to the superheater if it required superheated steam for any work. There is a blow-off valve is present at the bottom section of this boiler. By this valve, we can clean mud and also drain the water.
Advantage and Disadvantages of Lancashire Boiler: It’s easy to operate this boiler and it required less maintenance. A manhole is providing with this boiler and for this reason, it is easy to clean and inspect inside the boiler. It is one of the most reliable boilers. This boiler can generate a large amount of steam and it can easily meet with the requirement of steam. This boiler is a natural water circulation boiler. This boiler has a high thermal efficiency of about 80 to 90 percent. After all those advantages it has some disadvantage. Because this boiler required more space on the floor. It also has a leakage problem. The process of steam generation required more time. This boiler cannot generate high-pressure steam when you need it.
4.Locomotive Boiler:- A locomotive boiler is a Fire Tube Boiler. It is a horizontal drum axis, multi-tubular boiler. Because this boiler has 116 general fire tube and 38 super-heated fire tube. Locomotive Boiler is an internally fired boiler. That’s means boiler furnace located inside the main boiler shell or barrel. This boiler uses solid fuel like coal. It is also a forced circulation, mobile or portable type, and medium pressure fire tube boiler. The most common use of this boiler is in railway locomotive engines and in the marine sector because of its mobility. This boiler has a high steam generation rate.
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Locomotive Boiler
Construction of Locomotive Boiler:
A Locomotive Boiler has several components. First of all, it’s shell or barrel. Generally, boiler shell diameter is about 8.5m and length is about near 4m. A Steam Dome presents at the top section of the boiler. It contains the regulator for regulating the steam produced through the steam pipe when the boiler is operational. Firing point or hole present at the rear end of the boiler. We already know that this boiler uses solid fuel in the furnace. Solid fuel is inserted and ignited into the furnace by using this hole. After that, a firebox is present inside the boiler shell where the fuel is burned and generates heat. There is a platform called Grate where solid fuel like coal is kept and burnt. It is a fire tube boiler and we already know how many fire tubes are present inside this boiler with its types. The fire tubes in which, the hot flue gases pass. When hot flue gases pass it exchange the heat with the surrounding water. There is a smoke box and it is the only way where smoke is passing through the
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air. When solid fuel burned inside the furnace it also creates some smoke. This smokes need to exhaust in the environment by the chimney.
There is a fire brick arch placed inclined over the grate. It is responsible for preventing the entry of the ash, burnt fuel, and dust particles into the fire tubes during operation. Brick arch also provides a way to the hot flue gases to travel a definite path before entering the boiler fire tubes. There is a pipe called SteamPipe. By this pipe generated steam passes through. There are two steam pipes in Locomotive Boiler. First one is the main steam passing pipe. It located between the superheater and dome. The second steam pipe is connecting the superheater exit end to the steam engine. A blast pipe is provided above the steam engine. By this pipe, the exhaust steam passes. It has an important role during boiler operation. Generally, a blast pipe is used to create the artificial draft that pushes the smoke out through the chimney. It also creates suction pressure for the hot flue gases. This suction pressure allows the hot flue gases to passes forward and it passes through the boiler fire tubes.
This boiler has a Super-Heater and it superheats the steam to the desired temperature. Steam used to superheated before it enters into the cylinder of the steam engine. Because wet steam creates is harmful to the engine. There are a superheater element pipes by which the steam travels and become superheated. The safety valve is used for safe working with steam pressure. This safety valve is responsible for the blows off steam when the pressure of generated steam is increased above the safety level or critical level. It also prevents the blasting of the boiler. There is a Regulator valve present that regulates the steam through the main steam pipe for super-heating. Now come to the final component of this boiler and it is Chimney. It is used to throw out the exhaust smoke and gases to the environment. Working of Locomotive Boiler: The locomotive boiler uses solid fuel like coal. At first, the solid fuel is inserted on the grate. Then it ignites from the fire hole. When the fuel is burning inside the fire hole, it starts to generate necessary hot
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flue gases. Then a fire brick arch provides the path to flow the hot flue gases to a definite path before it entering into the long fire tubes of this boiler. As we know it also stops entering the burnt solid fuel particles into the fire tubes during the operation of the boiler. You will find two air in damper to flow fresh air into the combustion chamber.
When hot flue gases pass through the boiler firetubes then it heats the water surrounding the fire tubes. Water becomes heated by this continuous process and water becomes saturated steam. Generated saturated steam is collected at the top. Then this saturated steam from the dome (which is present at the top of the boiler) enters into the main steam pipe through the regulator valve. After this stem steam travels through the main steam pipe and reaches to the super-heater header. Form this super-heater header steam enters into another pipe called superheater element pipes. It is the place where saturated steam becomes superheated. Then superheated steam enters into the steam pipe of the smoke box.
When saturated steam becomes superheated then it goes to the cylinder containing piston. By this superheated steam engine piston moves inside the cylinder. Piston use to connect with the wheels of the steam engine and the wheels start rotating like a locomotive train. Then the exhaust steam from the cylinder enters into the blast pipe. When you are sending steam into the cylinder then only steam will come out as exhaust gas.
Burnt gases and smoke after passing through the fire tubes of the boiler then it enters into the smoke box. Then the exhaust steam coming out from the blast pipe and it pushes the smoke out of the boiler through the chimney. Smoke from burned solid fuel cannot escape out from the boiler by its own. For this reason, an artificial draft is created by exhaust steam which coming out from the steam engine cylinder. This artificial draft also pushes the smoke out of the smoke box and creates suction pressure for the hot flue gases. There is a platform under the Grate called ash-pit where ash is stored after burning of solid fuel.
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Application of Locomotive Boiler: Locomotive boilers are mostly used in railways and marines sectors. But the efficiency of this boiler is very less. This boiler cannot work in heavy load conditions. Locomotive Boiler is also used in traction engines, in portable steam engines, steam rollers, and some other steam road vehicles. Advantage and Disadvantage of Locomotive Boiler: The best advantage if this boiler is it’s portable. Because you can take and place this boiler in any place. The price of this boiler is less and it is capable of handling fluctuating demands of steam. This boiler has a high steam generation rate. It comes with the compact in size and easy operates. 5.Lamont Boiler: Lamont boiler is the first forced convection boiler which is introduce in the year 1925. A water circulating pump is used in the boiler to circulate water inside the boiler. This pump is driven by the steam turbine which uses steam of boiler. It is used in power plant industries to generate electricity. Principle: This boiler works on basic principle of forced convection. If the water is circulate by a pump inside the tube, the heat transfer rate from gas to the water is increases. It is the basic principle of it.
Construction: This boiler is the first force circulation boiler. This boiler consist various part which are as follow.
1.Economizer:
Economizer use to preheat the water by using remaining heat of the combustion gases. It increases the boiler efficiency. The feed water first supplied to the economizer before entering to the boiler.
2.Centrifugal pump:
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The Lamont boiler is a force convection boiler. So a centrifugal pump is used to circulate water inside the boiler. This pump is driven by a steam turbine. The steam for the turbine is taken by the boiler.
3.Evaporator tube:
The evaporator tube or can say water tubes are situated at furnace wall which increase the heating surface of boiler. This is also at the up side and down side of the furnace and other equipment. The main function of these tubes to evaporate water into steam. This also cools down the furnace wall.
4.Grate:
The space in the furnace where the fuel is burn is called grate. It is bottom side of furnace.
5.Furnace:
In the Lamont boiler vertical furnace is used. The main function of Furnace is to burn the fuel.
6.Super heater:
The steam generated by the evaporator tube is saturated steam. If it directly used in steam turbine can cause the corrosion. So the saturated steam sends to the super heater where it can increase the temperature of steam.
7.Water steam separator drum:
The steam separator is situated outside from the boiler. The mixture of water and steam from the evaporator tube send to the steam separator where it separate the steam and send it to super heater. The remaining water again sends to the economizer.
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It’s main function to preheat air before entering into furnace.
Working:
Lamont boiler is a forced circulation, internally fired water tube boiler. The fuel is burn inside the boiler and the water is circulating by a centrifugal pump through evaporator tubes. The working of this boiler is as follow.
A feed pump forces the water into the economizer where the temperature of water increases. This water forced into the evaporator tube by using a centrifugal pump driven by steam turbine. Water passes 10 – 15 times into the evaporator tube. The mixture of saturated steam and water is formed inside the tube.
This mixture sends to the steam separator drum which is outside the boiler. Steam from the separator sends to the super heater, where the saturated steam converts into superheated steam. The water again sends to the economizer where it again passes by the evaporator tubes.
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The air from the air preheater enter into the furnace where fuel burn. The flue gases first heat the evaporator tube then passes by the super heater. These gases from the super heater again use to preheat the air into air preheater before exhaust into atmosphere.
This working pressure of this boiler is above 170 bar and have the steam generation capacity of about 50000 kg/hour at temperature 773 K .
Advantages of the Lamont Boiler:
1.It has a high heat transfer rate.
2.Its design is simple.
3.It can be easily started.
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4.High steam generation (about 50 tonnes per hour)
5.Can be reassembled with the natural circulation boilers.
Disadvantages of the Lamont Boiler:
Bubble formation on a surface of the tube reduces the heat transfer rate. 6.Benson boiler:
Benson boiler is also known as super critical steam generator which is developed by Mark Benson in the year 1922. This boiler can generate high pressure steam, which is further used in production of electricity and other industrial processes. It is a water tube boiler. In the early stage water tube boiler used to generate steam at the pressure up to 10MPa, which is known as sub critical boiler.
Principle:
The Benson boiler is a water tube boiler, works on the basic principle of critical pressure of water. The critical pressure is the pressure at which the liquid and gas phase are at equilibrium. The water enters in the boiler at just above the critical pressure so it suddenly convert into steam without generating air bubbles. No air water separator drum is required. It also takes less fuel to generate steam. This is the basic principle of Benson boiler.
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Main parts:
It consist a great large tube. The water enter into the tube from one end and steam exit from other end. No water steam separator drum is used in this boiler. This boiler consist six basic component.
1.Feed pump
Benson boiler is the forced pumped water tube boiler. The water is enter into the boiler at critical pressure A feed pump is used to pump the water into boiler.
2.Air preheated
In this boiler air is preheated from before entering into combustion chamber. It increase the efficiency of boiler.
3.Economizer:
Water from the feed pump enter into the tube which first passes from economizer which used the combustion gases to preheat the water which also increase efficiency of boiler.
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4.Radiant Evaporator:
The water from the economizer further passes to the radiant evaporator, which use radiant heat transfer method to transfer heat from combustion chamber to the water. This section is near the combustion chamber. 5.Convective Evaporator:
In the convective chamber, convection is used to transfer heat from the flue gases to the water. The water is completely evaporate in this chamber. 6.Convective Super heater:
This is the last chamber of boiler. The steam passes from this chamber, which increase the temperature of steam and this super-heated steam taken out for the industrial work.
Working:
As we discussed this boiler works on the basic principle of critical pressure. The water is pumped at above the critical pressure into boiler tube. This water tube first passes through the economizer, which increase the temperature of water. This hot water further passes from the radiant evaporator where water is evaporate by radiant heat transfer. After that the water and steam passes through the convective evaporate where water is completely convert into steam. The water pressure is critical pressure so the water convert into steam directly without actual boiling. The steam is further heat up and this super-heated high pressure steam is taken out to rotate the turbine
Advantage: 1. The Benson boiler does not use water-steam separator drum, which reduce the total cost of boiler. 2. This boiler can transport easily from one station to another 3. It is economical and have higher efficiency. 4. This boiler can use over the pressure above 350 bar without changing the evaporator. 5. This can be start easily and can reach its maximum load capacity within 10 minutes.
7.Velox Boiler: velox boiler is a forced circulation water tube boiler. It is mostly used in gas turbine. In this boiler, the velocity of flue gases is greater than the velocity of sound, which causes more heat
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transfer from gas to the water, which increases the steam generation rate. Due to this, it is most important boiler.
Principle:
When the velocity of the gas is greater than the speed of sound, its heat transfer rate is also increases. So more heat is transfer from gas to water as compare when the heat transfer at the subsonic speed. This is the basic principle of of it. This boiler can increase the heat transfer rate or can say steam generation rate without increasing boiler size. This is why; Velox boiler is most successful boiler in the gas turbine industries.
Construction:
Velox boiler is a water tube forced circulation boiler. It has a gas turbine driven air compressor, which compresses the air. This compressed air enters into the vertical combustion chamber, as result, high rate of heat release from the fuel, which increases the flue gases velocity up to the sound velocity. This is a force circulation boiler, so pump is used to circulate water inside the boiler. This boiler also consist water and fire tube to maintain the flow of gas and water inside the boiler. This boiler also consists other necessary mounting and accessories like economizer, super heater, blow off valve, safety valve etc.
Working:
The air is compressed by air compressor driven by gas a turbine driven. This compressed air passes from the combustion chamber, where more heat release by the fuel which increase the velocity of the flue gases up to sound velocity. From the bottom of combustion chamber, this flue gases pass from the fire tubes. These fire tubes surrounded by the evaporator water tubes. The water from the economizer passes from the evaporator tube force by a circulating pump. This water passes 15 – 20 time from the evaporator tube at very high speed. Due to this high speed circulation, heat is transfer from the gases to the water at very high rate. The mixture of water and steam is formed which further passes from the water and steam separator.
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The steam from the steam separator passes to the super heater and further for process work. The remaining water in the steam separator again passes from the evaporator tube. The flue gases from the fire tubes send to the super heater tubes, where it increases the steam temperature. The gas from the super heater sends to the turbine where it rotates the gas turbine and then passes from the economizer. Advantages: 1. This boiler has high heat transfer rate. 2. It has great flexibility. 3. it is compact in design. 4. It is easy to control. It is fully automatic. 5. It has great thermal efficiency of about 90 – 95%.
Application: The steam generated by steam boilers is used for driving various type of steam turbines which further drives various types of pumps compressors, generators etc.Steam generated by boiler is used in the process of a chemical plant it has various uses like heating or
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for various chemical reactions where steam is used as feed.
Expected Outcome: We have successfully completed the study of various types of boilers.
Comment by Student:
Viva Questions
1. What is the function of a Boiler? 2.What is the life of a power plant? 3.What is safety requirement for boiler, in India? 4.What are the materials used for boiler pressure parts? 5.What are the materials used for boiler structures? 6.What is the material used for boiler foundation? 7.What are the types of bolted connections used for boiler structures? 8.Why steel is used for boiler pressure parts? 9.What is the purpose of refractory? 10.What is the purpose of refractory retainers? 11.Why water quality is control of in boilers? 12.Why rockers are used for boiler hanger supports?
EXPERIMENT NO. 5
AIM: - To study various types of mountings & accessories
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APPARATUS USED: - Model of Mounting & accessories in boiler.
THEORY: - For efficient operation and maintenance of safety, the boiler equipped with two categories of components and elements. First categories include the fittings which are primarily indicated for the safety of the boiler and for complete control of the process of steam generation. These units are called mountings. The mounting from an integral part of the boiler and are mounted on the body of the boiler itself. The following mountings are usually installed on the boiler. 1. Two safety valve 2. Two water level indicators 3. Pressure gauge 4. Fusible plug 5. Steam stop valve 6. Feed check valve 7. Blow- of cock 8. Man and mud hole Second categories include the components which are installed to increase the efficiency of the steam power plants and help in the proper working of the boiler unit. These fitting are called boiler accessories. The following accessories are given below. 1. Air pre-heater 2. Economizer 3. Super heater 4. Feed pump and 5. Injector
FUNCTION, LOCATION AND WORKING OF MOUNTINGS AND ACCESSORIES:-
(A) SAFETY VALVE: - The function of the safety valve is to permit the steam in the boiler to escape to atmosphere when pressure in the steam space in the boiler. The safety valve operates in the principle that a valve is pressed against its seat through some agency such as strut, screw or spring by external weight or force. When the steam force due to boiler pressure acting under the valve exceeds the external force, the valve gets lifted off its seat and some of the steam rushes out until normal pressure is restored again. The commonly used safety valves are given below:- i) Dead weight safety valve ii) Lever safety valve iii) Spring loaded safety valve iv) High steam- low water safety valve
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Safety Valve
(B) WATER LEVEL INDICATOR:- The function of the water level indicator is to ascertain constantly and exactly the level of water in the boiler shell. It is fitted in the front of the boiler from where it is easily visible to the operator.The unit consists of a strong glass tube whose ends pass through stuffing boxes consists of heat resisting rubber packing to prevent leakage steam and water. The flanges are bolted to front end plate of the boiler, the upper flange being fitted to the steam space and the lower to water space in the boiler. There are two cocks namely steam cock and water cock which communicate the boiler shell spaces to the gauge glass tube. When the handle of the cocks are vertical, they are in operation and the water level in the tube corresponds to water level in the shell. A red mark on the glass tube indicates the safe water level.
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(C) FUSIBLE PLUG: - The function of the fusible plug is to extinguish the fire in the event of the boiler shell falling below a certain specified limit. We know that when the water on heating transforms into steam, the level of water in the boiler falls down. If the water is not replenished and the steam generation continues then the parts, which have been uncovered by water uncovered by water may get overheated and subsequently are melted. To safeguard against this eventuality we use fusible plug. The fusible plug is inserted at the box crown or over the combustion chamber at the lowest permissible water level
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Fusible Plug
(D) PRESSURE GAUGE: - Each boiler has to be provided with a pressure gauge, which records the pressure at which the steam is being generated in the boiler. The gauge is usually mounted at the front top of the boiler shell or drum. The gauge has to be clearly visible to the attendant so that he can easily record the pressure reading.
(E) BLOW OFF COCK: - The blow of cock serves to drain out the water from the boiler periodically for any one of the following reasons:-
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(1) To discharge mud, scale and other impurities which settle down at the bottom of the boiler. (2) To empty the boiler for internal cleaning and inspection. (3) To lower the water level rapidly if the level becomes too high.
The unit is fitted at the lowest portion of the boiler. It may be mounted directly to the boiler shell or through a boiler elbow pipe, which is fitted to the boiler shell.
(F) FEED CHECK VALVE: - The feed check valve has the following two functions to perform:- 1. To allow the feed water to pass into the boiler. 2. To prevent the back flow of water from the boiler in the events of the failure of the feed pump.
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(G) STOP VALVE: - The function of the steam stop valve is to shut off or regulate the flow of steam from the boiler to the steam pipe or from the steam pipe to the engine. When used for the former purpose, it is called junction valve. Usually the junction valve means a regulating valve of larger size and a stop valve refers to a regulating valve of smaller size. The junction valve is mounted on the highest part of the steam space of the boiler and is connected to the steam pipe, which carries the steam to the engine.
Stop Valve (H) MAN HOLES: - These are door to allow men to enter inside the boiler for the inspection and repair.
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Man Hole (I) AIR PRE HEATER: - Air heater or air pre-heater is waste heat recovery device in which the air on its way to the furnace is raised in temperature by utilizing the heat of the exhaust gases. Air pre-heater are classified into the following two categories. • Recuperative Air heater • Regenerative Air heater
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Air Pre Heater
(J) ECONOMISER: - The economizer is a device, which serves to recover some of the heat being carried by exhaust flue gasses. The heat thus recovered is utilized in raised temperature in feed water being supplied to the boiler. If the water at rose and thus there is a saving in the consumption of fuel. The economizer unit is installed in the path of the flue gasses between the boiler and the chimney.
Economizer
(K) STEAM SUPER HEATER: - The steam generated by a simple boiler in generally wet or at the most dry saturated. Steam super heater is a surface heat exchanger in which the wet steam is first dried at the same temperature and pressure and then raised to temperature above the saturation temperature at constant pressure. Heat of flue gasses utilized in super heating the steam and as the super heater is placed in the path of the flue gasses. Since superheating result in the increased efficiency and economy of the steam plant.
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(L) FEED WATER EQUIPMENT: - The pressure inside a steaming boiler is high and so the feed water has to be raised in pressure before its entry can be affected in the boiler. Feed pump is a device which raised the pressure of water and forces it into the boiler.
Application: Mounting and accessories of boilers are used for safety,regulating and performance purpose.These devices can also be used in other equipments for same purpose.
Expected Outcome: We have successfully completed the working and function of mountings & accessories in boiler.
Comment by Student:
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Viva Questions
1.What is the function of the economizer? 2.What are the functions of steam drum? 3.What is the function of super-heater? 4.Why large boilers are top supported? 5.Why steel structures (avoiding concrete) are used for boiler structures?
6. Briefly explain the Boiler mounting, and name its classifications?
7. What is a valve? 8.Discuss the function of Safety, Stop, and Feed check valves?
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JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
EXPERIMENT NO. 6
AIM: - Demonstration of steering system and measurement of steering geometry angles and their impact on vehicle performance.
THEORY :
Function of Steering System
The function of a steering system is to convert the rotary movement of the steering wheel in driver’s hand into the angular turn of the front wheels on road. Additionally, the steering system should provide mechanical advantage over front wheel steering knuckles, offering driver an easy turning of front wheels with minimum effort in any desired direction. When the driver turns the steering wheel, the front and sometimes the rear wheels move and the car turns the corner! From the drivers point of view it is that simple, but many more things have to be taken into consideration. For example –The effect of road surface irregularities
Tyre behaviour under cornering stress,An efficient mechanical system to give easy turning of the steering wheel, Driver fell must be maintained, No (or very little) difference between empty and fully loaded,The effect of accelerating or braking when the wheels are turned. The front wheels should have a natural tendency to return to the straight ahead position also its function is to control of front wheel (sometimes rear wheel) direction. it maintain correct amount of effort needed to turn the wheels. It absorb most of the shock going to the steering wheel as the tire hits holes and bumps in the road and allow for suspension action.
Terminology
The Steering Wheel – The Bit the driver holds on to! It also incorporates the Air Bag.
Steering Column – The shaft connecting the steering wheel to the steering box or steering rack.
Steering Rack – A combination of a small gear and a toothed rack. This changes the rotation of the steering wheel into a back and forth movement of the rack which in turn moves the road wheels.
Steering Box – This does a similar job to the rack but needs extra linkages and rods to connect it to the road wheels. Mostly used on old cars, but still is in use on larger vehicles.
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Track rod/Tie rod – A rod to connect the left and right steered wheels. The steering rack is also the track rod.
Track rod end – A ball joint to allow steering and suspension movement.
Ball joint/Swivel joint – Part of the suspension, but these are joints which allow the steered wheels to left and right.
PAS – (Power assisted steering) An engine driven pump or electric motor, provides extra force to help the driver turn the steering.
Tracking – toe in or toe out setting for the steered wheels
Ackerman Principle :
Ackermann stated the principle that when a vehicle travels in a curved path, its wheels should describe circles around the same centre. A wheel which follows a markedly different path will slide to some extent, this would cause excessive tyre wear. The steering mechanism is designed to insure that when the vehicle turns left or right, the inner wheel is turned through a larger angle to prevent tyre wear.
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Turning Radius (Ackerman Principle) :
When turning, the inner wheels must turn on a tighter radius than the outer, this helps avoid unnecessary tyre wear. The steering system is designed to compensate for the different radiuses.
Front Wheel Tracking – A steering adjustment which is used to insure that the steered wheels are pointing straight ahead when the vehicle is moving
Toe-in - The wheels point inward, toward each other. This setting is critical for tyre wear. A small amount of Toe-in helps compensate for the effect of rear-wheel drive
Toe-out - The wheels point away from each other. A small amount of Toe-out is normal on front-wheel drive vehicles.
Zero “toe” effect is required when the vehicle is moving. This helps reduce tyre wear (scuffing or feathering).
Steering Shafts and Columns :
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Nearly all steering systems use a steering column or shaft to link the driver (steering wheel) to the steering rack or gear/box. Flexible coupling isolates steering wheel from road shocks. Universal joints allow steering shaft angles to change. Most steering columns are designed with a collapsible section that helps prevent forces generated in a collision being transferred to the driver. Bottom of steering column normally has a master spline where it mounts onto the steering rack-and-pinion or steering gear/box
Steering System Parts:
Steering Wheel :used by the driver to rotate a steering shaft that passes through the steering column.
Steering Shaft :Transfers turning motion from the steering wheel to the steering gearbox.
Steering Gearbox) :changes turning motion into a straight line motion to the left or right.Steering gear box ratios range from 15:1 to 24:1 (with 15:1, the worm gear turns 15 times to turn the selector shaft once
Wheel Geometry Fundamentals :
Correct wheel alignment allows vehicle to run straight on the highway,little steering effort and minimal tire wear.
Five wheel alignment angles : Toe,Camber,Caster,Steering axis inclination (SAI),Turning radius
Toe : Comparison of distances between fronts and rears of a pair of tires.This angle most responsible for tire wear
Toe-in: tires closer together at the front
Toe-out: tires further apart at the front
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Causes of incorrect toe: Improper adjustment,Bent steering linkage,Change in caster or camber adjustment,Looseness in steering linkage due to wear
Camber : inward or outward tilt of tire at top and adjustable on most vehicles
Positive camber: tire tilts out
Negative camber: tire tilts in
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Caster: forward or rearward tilt of the spindle support arm
Positive caster: top tilted to the rear Lead point in front of true vertical
Negative caster: steering axis tilts forward.
Application:Steering system and steering geometry of vehicle provide the directional stability, alignment,balancing of vehicle .Also provide the comfortness to the drive.
Expected Outcome: We have successfully completed the demonstration of steering system and measurement of steering geometry angles and their impact on vehicle performance.
Comment by Student:
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Viva Questions
1. The component that connects the steering rack to the knuckles is
2.Incorrect steering axis inclination (S.A.I.) causes. 3.Positive camber is used to compensate for wheels tilting inward due to the weight of the vehicle.
4.The effect of having excess camb
5.What is toe-in and its effect on steering.
6.What is the effect of camber on tyre wear.
7.What is the effect of slip angle on cornering force.
8.What is inflation pressure.
9.Define turning radius and its significance.
10.Define steering gear ratio and why it is necessary.
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JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
EXPERIMENT NO. 7
AIM: - Study of braking system with specific reference to types of braking system, master cylinder , brake shoes.
THEORY :
Brakes
A brake is a device by means of which artificial resistance is applied on to a moving machine member in order to retard or stop the motion of the member or machine.
Types of Brakes
Different types of brakes are used in different applications based on the working principle used brakes can be classified as mechanical brakes, hydraulic brakes, electrical (eddy current) magneticand electro-magnetic types.Mechanical Brakes :Mechanical brakes are invariably based on the frictional resistance principles. In mechanical brakes artificial resistances created using frictional contact between the moving member and a stationary member, to retard or stop the motion of the moving member.
Constructional details, working principles and operation of the Hydraulic and Pneumatic Brake systems:
Hydraulic brake system :
The Hydraulic brake system is a braking system which uses brake fluid usually includes ethylene glycol, to transmit pressure from the controlling unit, which is usually near the driver, to the actual brake mechanism, which is near the wheel of the vehicle. The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of Brake pedal or Brake lever Pushrod, also called an actuating rod Reinforced hydraulic lines. Rotor or a brake disc or a drum attached to a wheel Master cylinder assembly includes: Piston assembly is made up of one or two pistons, a return spring, a series of gaskets or O-rings and fluid reservoir.
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Brake caliper assembly usually includes: One or two hollow aluminum or chrome plated steel pistons called caliper pistons and set of thermally conductive brake pads.A glycol ether based brake fluid regularly loads the system or some other fluids are also used to control the transfer of force or power between the brake lever and the wheel. The automobiles generally use disc brakes on the front wheels and drum brakes on the rear wheels. The disc brakes have good stopping performance and are usually safer and more efficient than drum brakes. Many two wheel automobiles design uses a drum brake for the rear wheel.
Hydraulic- Brake
In Hydraulic brake system when the brake pedal or brake lever is pressed, a pushrod applies force on the piston in the master cylinder causing fluid from the brake fluid tank
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to run into a pressure chamber through a balancing port which results in increase in the pressure of whole hydraulic system. This forces fluid through the hydraulic lines to one or more calipers where it works upon one or two extra caliper pistons protected by one or more seated O-rings which prevent the escape of any fluid from around the piston.
The brake caliper piston then applies force to the brake pads. This causes them to be pushed against the rotating rotor, and the friction between pads and rotor causes a braking torque to be generated, slowing the vehicle. Heat created from this friction is dispersed through vents and channels in rotor and through the pads themselves which are made of particular heat tolerant materials like kevlar, sintered glass.The consequent discharge of the brake pedal or brake lever lets the spring(s) within the master cylinder assembly to return that assembly piston(s) back into position. This reduces the hydraulic pressure on the caliper lets the brake piston in the caliper assembly to slide back in to its lodging and the brake pads to discharge the rotor. If there is any leak in the system, at no point does any of the brake fluid enter or leave.
In hydraulic brake the brake pedal is called as brake pedal or brake lever. One end of the hydraulic brake is connected to the frame of the vehicle, the other end is connected to the foot pad of the lever and a pushrod extends from a point along its length. The rod either widens to the master cylinder brakes or to the power brakes. The master cylinder is separated as two parts in cars, each of which force a separate hydraulic circuit. Every part provides force to one circuit. A front/rear split brake system utilizes one master cylinder part to pressure the front caliper pistons and the other part to pressure the rear caliper pistons.
Pneumatic or Air Brake System
It is the brake system used in automobiles such as buses, trailers, trucks, and semitrailers. The Compressed Air Brake System is a different air brake used in trucks which contains a standard disc or drum brake using compressed air instead of hydraulic fluid. The compressed air brake system works by drawing clean air from the environment, compressing it, and hold it in high pressure tanks at around 120 PSI. Whenever the air is needed for braking, this air is directed to the functioning cylinders on brakes to activate the braking hardware and slow the vehicle. Air brakes use compressed air to increase braking forces.
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Air Brake
Design and Function:
The Compressed air brake system is separated into control system and supply system. The supply system compresses, stores and provides high pressure air to the control system and also to other air operated secondary truck systems such as gearbox shift control, clutch pedal air assistance servo, etc., Control system: The control system is separated into two service brake circuits. They are the parking brake circuit and the trailer brake circuit. This two brake circuits is again separated into front and rear wheel circuits which gets compressed air from their individual tanks for more protection in case of air leak.
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The service brakes are applied by brake pedal air valve which controls both circuits. The parking brake is the air controlled spring brake which is applied by spring force in the spring brake cylinder and released by compressed air through the hand control valve. The trailer brake consists of a direct two line system the supply line which is marked red and the separate control or service line which is marked blue. The supply line gets air from the main mover park brake air tank through a park brake relay valve and the control line is regulated through the trailer brake relay valve. The working signals for the relay are offered by the prime mover brake pedal air valve, trailer service brake hand control and Prime Mover Park brake hand control.
Constructional details, working principles and operation of the Drum Brake System
Drum brakes consist of a backing plate, brake shoes, brake drum, wheel cylinder, return springs and an automatic or self-adjusting system. When you apply the brakes, brake fluid is forced under pressure into the wheel cylinder, which in turn pushes the brake shoes into contact with the machined surface on the inside of the drum. When the pressure is released, return springs pull the shoes back to their rest position. As the brake linings wear, the shoes must travel a greater distance to reach the drum. When the distance reaches a certain point, a self-adjusting mechanism automatically reacts by adjusting the rest position of the shoes so that they are closer to the drum.
Brake Shoes: Like the disk pads, brake shoes consist of a steel shoe with the friction material or lining riveted or bonded to it.
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Backing Plate: The backing plate is that holds everything together. It attaches to the axle and forms a solid surface for the wheel cylinder, brake shoes and assorted hardware.
Brake Drum: Brake drums are made of iron and have a machined surface on the inside where the shoes make contact. Just as with disk rotors, brake drums will show signs of wear as the brake linings seat themselves against the machined surface of the drum.'
Wheel Cylinder: The wheel cylinder consists of a cylinder that has two pistons, one on each side. Each piston has a rubber seal and a shaft that connects the piston with a brake shoe. When brake pressure is applied, the pistons are forced out pushing the shoes into contact with the drum. Wheel cylinders must be rebuilt or replaced if they show signs of leaking.
Return Springs: Return springs pull the brake shoes back to their rest position after the pressure is released from the wheel cylinder. If the springs are weak and do not return the shoes all the way, it will cause premature lining wear because the linings will remain in contact with the drum.
Self Adjusting System: The parts of a self adjusting system should be clean and move freely to insure that the brakes maintain their adjustment over the life of the linings. If the self adjusters stop working, you will notice that you will have to step down further and further on the brake pedal before you feel the brakes begin to engage. Disk brakes are self adjusting by nature and do not require any type of mechanism.
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Constructional details, working principles and operation of the Disk Brake System
The disk brake is the best brake we have found so far. Disk brakes are used to stop everything from cars to locomotives and jumbo jets. Disk brakes wear longer, are less affected by water, are self adjusting, self cleaning, less prone to grabbing or pulling and stop better than any other system around. The main components of a disk brake are the Brake Pads, Rotor, Caliper and Caliper Support.
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Brake Pads: There are two brake pads on each caliper. They are constructed of a metal "shoe" with the lining riveted or bonded to it. The pads are mounted in the caliper, one on each side of the rotor. Brake linings used to be made primarily of asbestos because of its heat absorbing properties and quiet operation; however, due to health risks, asbestos has been outlawed, so new materials are now being used.
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Rotor: The disk rotor is made of iron with highly machined surfaces where the brake pads contact it. Just as the brake pads wear out over time, the rotor also undergoes some wear, usually in the form of ridges and groves where the brake pad rubs against it.
Application : Shoe/drum brakes are good for static friction, disc brakes are better at dynamic friction and do dissipate braking energy more efficiently. All modern cars have at least disc brakes on the front while the rears are drum brakes, a lot of newer cars however make use of disc brakes all round as discs are generally more efficient, no modern car have drums on all four wheels these days.
Expected Outcome: We have successfully completed the study of braking system with specific reference to types of braking system, master cylinder , brake shoes.
Comment by Student:
Viva Questions
1.Which symptom is caused as a result of brake disc run out ?
2.The condition that causes vapour locking in a brake system is
3.The operation of removing trapped air from the hydraulic braking system is known as
4.Define brake fading,
5.What is the object of servomechanism.
6.Differentiate between drum and disc brake.
7.What is the meaning of vehicle braking efficiency.
8.Define brake squeaking and brake binding.
9.What is meant by power brakes and servo brakes. 10.What are the effect of air in hydraulic braking system.
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JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
EXPERIMENT NO. 8
AIM: - To study Transmission system including clutches, gear box assembly and differential.
THEORY :
The most common transmission systems that have been used for the automotive industry are manual transmission, automatic transmission (transaxle), semi-automatic transmission, and continuously variable transmission (CVT). Automobile or automotive transmission system consists of various devices that help in transmitting power from the engine through the drive shaft to the live axle of an automobile. Gears, brakes, clutch, fluid drive and other auto transmission parts work together for transforming the speed ratio between the engine and wheels of a vehicle.
Transmission is the mechanism which is used to transfer the power developed by engine to the wheels of an automobile.The transmission system of an automobile includes clutch, gear box, propeller shaft axle and wheels, etc.The term ‘Transmission’ is used for a device which is located between clutch and propeller shaft. It may be a gear box, an over drive or a torque converter, etc.
CLUTCH
Clutch is used to engage or disengage the engine to the transmission or gear box. When the clutch is in engaged position, the engine power or rotary motion of engine crankshaft is transmitted to gear box and then to wheels. When clutch is disengaged, the engine power does not reach to gear box (and to wheels) although engine is running.
Clutch is also used to allow shifting or changing of gears when vehicle is running. For shifting gears, clutch is first disengaged then gear is shifted and then clutch is engaged. Clutch has to be disengaged to stop the vehicle and also at the time of idling.
PRINCIPLE OF CLUTCH
It operates on the principle of friction. When two surfaces are brought in contact and are held against each other due to friction between them, they can be used to transmit power. If one is
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rotated, then other also rotates. One surface is connected to engine and other to the transmission system of automobile.
Thus, clutch is nothing but a combination of two friction surfaces.
MAIN PARTS OF A CLUTCH
It consists of a driving member, a driven member, andan operating member.Driving member has a flywheel which is mounted on the engine crankshaft. A disc is bolted to flywheel which is known as pressure plate or driving disc.The driven member is a disc called clutch plate. This plate can slide freely to and fro on the clutch shaft.The operating member consists of a pedal or lever which can be pressed to disengaged the driving and driven plate.
TYPES OF CLUTCH
Some types of clutches used in vehicles are given below :
1. Friction Clutch
It may be (i) single plate clutch, (ii) multiplate clutch, or (iii) cone clutch.
Multiplate clutch can be either wet or dry. A wet clutch is operated in an oil batch whereas a dry clutch does not use oil.
2. Centrifugal clutch.
3. Semicentrifugal clutch.
4. Hydraulic clutch.
5.Positive clutch.
6. Vacuum clutch.
7 Electromagnetic clutch.
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SINGLE PLATE CLUTCH (DISC CLUTCH)
A disc clutch consists of a clutch plate attached to a splined hub which is free to slide axially on splines cut on the driven shaft. The clutch plate is made of steel and has a ring of friction lining on each side. The engine shaft supports a rigidly fixed flywheel. A spring-loaded pressure plate presses the clutch plate firmly against the flywheel when the clutch is engaged. When disengaged, the springs press against a cover attached to the flywheel. Thus, both the flywheel and the pressure plate rotate with the input shaft. The movement of the clutch pedal is transferred to the pressure plate through a thrust bearing. Figure 1.1 shows the pressure plate pulled back by the release levers and the friction linings on the clutch plate are no longer in contact with the pressure plate or the flywheel. The flywheel rotates without driving the clutch plate and thus, the driven shaft. When the foot is taken off the clutch pedal, the pressure on the thrust bearing is released.
As a result, the springs become free to move the pressure plate to bring it in contact with the clutch plate. The clutch plate slides on the splined hub and is tightly gripped between the pressure plate and the flywheel.
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Disc Clutch
The friction between the linings on the clutch plate, and the flywheel on one side and the pressure plate on the other, cause the clutch plate and hence, the driven shaft to rotate. In case the resisting torque on the driven shaft exceeds the torque at the clutch, clutch slip will occur.
Multi-plate Clutch
In a multi-plate clutch, the number of frictional linings and the metal plates is increased which increases the capacity of the clutch to transmit torque. Figure 1.2 shows a simplified diagram of a multi-plate clutch.
The friction rings are splined on their outer circumference and engage with corresponding splines on the flywheel. They are free to slide axially. The friction material thus, rotates with the flywheel and the engine shaft. The number of friction rings depends upon the torque to be transmitted. The driven shaft also supports discs on the splines which rotate with the driven shaft and can slide axially. If the actuating force on the pedal is re-moved, a spring presses the discs into contact with the friction rings and the torque is transmitted between the engine shaft and the
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driven shaft. If n is the total number of plates both on the driving and the driven members, the number of active surfaces will be n – 1.
Multi-plate Clutch
FUNCTION OF GEAR BOX
An automobile is able to provide varying speed and torque through its gear box. Various functions of a gear box are listed below :
(a) To provide high torque at the time of starting, vehicle acceleration, climbing up a hill.
(b) To provide more than forward speeds by providing more than one gear ratios. In modern cars, five forward gears and reverse gear is provided. For given engine speed, higher speed can be obtained by running in higher (4th and 5th) gears.
(c) Gear box provides a reverse gear for driving the vehicle in reverse direction.
TYPES OF GEAR BOXES
(a) Selective type gear boxes :
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(i)Sliding mesh gear box
(ii)Constant mesh gear box
(iii)Synchromesh gear box
(b)Progressive type gear box
(c) Epicyclic type gear box
Constant Mesh Gear Box
Synchromesh gear box (Four Speed Range)
Most modern manual-transmission vehicles are fitted with a synchronized gear box or synchromesh. Transmission gears are always in mesh and rotating, but gears on one shaft can freely rotate or be locked to the shaft. The locking mechanism for a ge ar consists of a collar (or dog collar) on the shaft which is able to slide sideways so that teeth (or dogs) on its inner surface bridge two circular rings with teeth on their outer circumference: one attached to the gear, one to the shaft. When the rings are bridged by the collar, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission. The gearshift lever manipulates the collars using a set of linkages, so arranged so that one collar may be permitted to lock only one gear at any one time; when "shifting gears", the locking collar from one gear is disengaged before that of another is engaged. One collar often serves for two gears; sliding in one direction selects one transmission speed, in the other direction selects another.
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Speed gearbox
In a synchromesh gearbox, to correctly match the speed of the gear to that of the shaft as the gear is engaged the collar initially applies a force to a cone-shaped brass clutch attached to the gear, which brings the speeds to match prior to the collar locking into place. The collar is prevented from bridging the locking rings when the speeds are mismatched by synchro rings. The synchro ring rotates slightly due to the frictional torque from the cone clutch. In this position, the dog clutch is prevented from engaging. The brass clutch ring gradually causes parts to spin at the same speed. When they do spin the same speed, there is no more torque from the cone clutch and the dog clutch is allowed to fall in to engagement. With continuing sophistication of mechanical development, fully synchromesh transmissions with three speeds, then four, and then five, became universal.
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Synchromesh Gear Box
Construction, Working Principle and Operation of Synchromesh –Four Speed Range
If the teeth, the so-called dog teeth, make contact with the gear, but the two parts are spinning at different speeds, the teeth will fail to engage and a loud grinding sound will be heard as they clatter together. For this reason, a modern dog clutch in an automobile has a synchronizer mechanism or synchromesh, which consists of a cone clutch and blocking ring. Before the teeth can engage, the cone clutch engages first which brings the selector and gear to the same speed using friction. Moreover, until synchronization occurs, the teeth are prevented from making contact, because further motion of the selector is prevented by a blocker (or baulk) ring. When synchronization occurs, friction on the blocker ring is relieved and it twists slightly, bringing into alignment certain grooves and notches that allow further passage of the selector which brings the teeth together.
Synchromesh Concept
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Constructional details, Working Principles and Operation of Differentials, Drive Axles and Four Wheel Drive Line :
In four wheel drive line vehicles, differentials are fitted to both front and rear axle assemblies. When a two-wheel drive range is selected, the drive is transferred through the rear final drive and the differential gears to the rear axle shafts and road wheels.
Wheel Drive Differential Axle Line
The differential gears allow the rear wheels to rotate at different speeds when the vehicle is turning, while continuing to transmit an equal turning effort to each wheel. When four-wheel drive is engaged, the drive is transmitted through both front and rear axle assemblies, and differential action occurs in both. However, in a turn, side-swiveling of the front wheels for steering makes the front wheels travel a greater distance than the rear wheels. This causes a difference in the rotational speeds of the front and rear wheels.
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Since there is also a difference between inner and outer wheels, each axle shaft now turns at a different speed. Differences in speed can also arise from differences in tread wear between front and rear, or in tire inflation pressures. Since front and rear propeller shafts are locked together at the transfer case, the difference in speed cannot be absorbed in the transmission, and the transmission drive line can be subjected to torsional stress.
Application:Transmission system provide the various speeds and torque to vehicle according to requirement.Transmission system is not only used in automobile but also in almost all industries e.g. lathe m/c,material handling etc.We can also see the use of gears in many domestic things.
Expected Outcome: We have successfully completed the study of transmission system including clutches, gear box assembly and differential.
Comment by Student:
JAIPUR ENGINEERING COLLEGE AND RESEARCH CENTRE
JECRC Campus, Shri Ram Ki Nangal, Via-Vatika, Jaipur
Viva Questions
1.A clutch is usually designed to transmit maximum torque which is
2.what is principle of freewheel clutch
3.what is the work of planet gears in differential.
4.Why the clutch plates are generally perforated.
5.What is meant by free play in a clutch.
6.What is common clutch facing material.
7. What is meant by riding the clutch pedal.
8.Where and why use is made of multiplate clutches.
9.Differentiate between dry and wet friction clutches.
10.How the working of clutch is affected by axial force,coefficient of friction and friction area.