Design and Assembly of IC Engine ABSTRACT

This thesis is about designing a new method to increase engines efficiency. The method used in this study is variable compression ratio (VCR) engines, where the compression ratio of the engine can be changed according to driving conditions. A mechanism of VCR is designed and simulated. The motion analysis is used to analyze the VCR mechanism and engines component behavior under different compression ratio. Solid works simulation software is used to perform the motion analysis. The data of stress distribution, deformation of engines component and factor of safety (FOS) from the simulation are used to determine whether the components are safe to operate at compression ratio higher than the original. Yamaha FZ150i engine has been chosen as the baseline engine design. The engine are disassembled and modeled in solid works in order to perform the simulation. The engine is simulated at 2000 rpm and the compression ratio are varies between 8:1 and 18:1. The result from of the simulation indicates that the compression ratio can safely be increased up to 12:1 with the original engines component specifications. If higher compression ratio wanted to be used, the specification of the engines component (piston and connecting rod) needed to be changed .However, since the Factor of safety (FOS) value of the components is critical at certain compression ratio, the fatigue and thermal analysis is purposed to be carried out in order to obtain more accurate result. CHAPTER 1

INTRODUCTION

1.1 Introduction This chapter gives a short description of the project background including the approaches taken to achieve the objective of study. This chapter then introduces objectives, scopes, problem statement and the importance of this study on the design of a variable compression ratio engine.

1.2 Project Background

The prime mover in the world today is the Internal Combustion (IC) engine. The development and improvement of the internal combustion engines since Nicolaus August Otto and Rudolf Diesel has continued until today and will continue long into the future. The environmental impact of the IC engine, due to its large numbers, is unacceptable. The advanced engine control and exhaust after treatment of the conventional IC engines have decreased the regulated emissions of Nitrous Oxide (NOx), CO, Hydrocarbon (HC), and particulates, to very low levels. However, the main greenhouse gas, Carbon Dioxide (CO ), 2 from IC engines is and will continue to be a problem in the future. The global heating of the world is directly connected to the increasing in CO emissions 2 emitted to the atmosphere by human activities. In order to decrease CO 2 emission from IC engines running on fossil fuel, the fuel consumption must be reduces, hence, we need more fuel efficient IC engines. The needs to reduce automotive fuel consumption and CO 2 emissions is leading to the introduction of various new technologies like Hybrid technologies for the gasoline engine as its fights for market share with the diesel. Today, the variable compression ratio (VCR) engines have not reached the market, despites patents and experiments dating back over decades. A variable compression ratio (VCR) engine is able to operate at a different compression ratios depending on the performance needs. The VCR engine is optimized for the full range of driving conditions, such as acceleration, speed, and load. At low power levels, the VCR engine operates at high compression to capture fuel efficiency benefits, while at high power levels, it operates at low compression levels to prevent knock. This project will focus on designing the mechanism of VCR and identify the challenge in designing it. There are several methods of VCR, we will compare and find out the best method to be used as the final design of our VCR mechanism. The design will then be tested and analyzed. 1.3 Problem Statement The usage of fossil fuel in internal combustion (IC) engine has lead to the emission of hazardous green house gases that cause a significant damage to our world and the spiking prices of fossil fuel will become a burden to the people because it is used widely throughout the world. The IC engine used today has low efficiency, making the energy in every drop of fuel is not fully utilized.

In order to increase engine efficiency, a high compression ratio must be used to increase the performance of gaseous fuel. VCR technologies enable the compression ratio to be change thus increasing the engines efficiency. The variable compression ratio (VCR) engine technology can be the solution to these problems. However, it is truly a challenge to design the simplest but effective mechanism of VCR as various factors and aspect of the engine must be considered. 1.4 Project Objective

The objectives of the project are to: 1. To design the mechanism of variable compression ratio (VCR) for single cylinder four-stroke engine. 2. To simulate the mechanism of variable compression ratio (VCR) for single cylinder four-stroke engine.

1.5 Scope of Project

In order to achieve the objectives of this project, the scopes are list as below: 1. The design of the VCR mechanism is based on six cylinder four-stroke engine (150 cc) 2. Minimize the modification on existing engine component

3. The study try to identify the simplest technique of VCR engine which can be attain manually.

4. The design will be analyzed using motion analysis.

5. The VCR engine is design solely for the purpose laboratory testing (it will be used to study the effect of different CR on gaseous fuel) 1.6 Project Flow Chart

START

Reassign FYP project title

Disassemble the engine of Yamaha FZ 150i for

Gather information for

Design and modeling of VCR mechanism by using Solidworks

Motion analysis of mechanism by using

Satisfy? NO YES END

Figure 1.1: Project flow chart Figure 1.2 Model of a four stroke six cylinder Development modeling. Internal combustion engines efficiency is less than 40%. Most of the energy generated by burning the fuel in the combustion chamber is lost in water cooling and exhaust Figure 2, below, shows a typical energy split in internal combustion engines.

Fig. 1.3 Energy split in engines.

In 2006, Bruce Crower managed to develop the first six stroke engine. Using a modified single-cylinder diesel engine Crower converted it to use gasoline, and then machined the necessary parts to create the world’s only six-stroke engine. The engine works through harnessing wasted heat energy created by the fuel combustion to add other two-strokes to the engine cycle. After the combustion stage water is injected into the super-heated cylinder and a steam form forcing the piston back down and in turn cools the engine. The result is normal levels of power using much less fuel and no need for an external cooling system.

There are two methods when operating six stroke engines, the first method by completely finished the exhaust stoke then inject the water. The second method is by trapping and recompression of some of the exhaust from the fourth piston stroke, followed by a water injection and expansion of the resulting steam/exhaust mixture, Figure 2 shows the six stroke engine cycle.

Fig. 2. The six-stroke engine cycle Conklin and Szybist [3] made a theoretical thermodynamics analysis to this six stroke engine with the second method, to calculate the effect of this new arrangement on mean effective pressure. The result from their analysis is shown in Figure 3.

Fig1.4 Mean effective pressure.

An increase in mean effective pressure with the increase of amount of water injected and also with more delaying of exhaust valve cam closing.

The starting of six stroke engine was a problem as reported by Andrew De Jong ET. Al. Instead of conventional starter a DC motor was used to start the engine. In this step of the project an experimental test will be done to a single cylinder four stroke internal combustion engine to convert it to six stroke engines just to be sure that the engine can run with six stroke cycles smoothly.

ENGINE MODIFICATION

To make six-stroke engine from conventional four-stroke engine, a few modifications must be done to specific parts on the conventional engine to be sure that the new engine with six-stroke will run successfully. A Mitsubishi single cylinder spark ignition engine was used to apply these modifications on it. These modifications are: Crankshaft to Camshaft Ratio Modification

In conventional four stroke engine, the gear at crankshaft must rotate 720ο while the camshaft rotates 360ο to complete one cycle. For six-stroke engine, the gear at the crankshaft must rotate 1080ο to rotate the camshaft 360ο and complete one cycle. Hence their corresponding gear ratio is 3:1. Shows the previous gear at regular engine running in four stroke engines at ratio 2:1 and the new gears to work with six stroke engines.

The Four Stroke Engine

The sound of a Harley-Davidson® motorcycle is highly recognizable and unmistakable. But what causes that significant sound?

The heart of a Harley-Davidson motorcycle is the engine. Harley-Davidson motorcycles are powered by an internal combustion engine. This means the engine burns fuel inside.

There are four strokes or stages in the engine cycle. The four strokes of the cycle are intake, compression, ignition, and exhaust. Bike lingo for this is: suck, squeeze, bang and blow. Each 180 degree turn of fly-wheel is one event stroke. The flywheel must make two revolutions to complete one power cycle of the motor. Crank shaft has 18 teeth and the cam shaft gear has 54 teeth. The type of gear is helical gear because it is suitable for high-speed, high power application and quite at high speed rotation.

Fig. 4. Crankshaft and camshaft modification. Camshaft Modification

In the six stroke engine the 360 degree of the cam has been divided into 60 degree among the six-strokes. The exhaust cam has 2 lobes to open the exhaust valve at fourth stroke (first exhaust stroke) and at the sixth stroke to push out the steam. Figure 5 shows the new cams and the new camshaft.

Fig. 5. Cams and Camshaft. Cam follower modification

The bottom shape of regular follower has the flat pattern, which is suitable with the normal camshaft for four stroke engine. When reducing the duration of valve opening from 9000 to only 600 0 the shape of the follower must be changed from flat to roller or spherical shape. In this case a spherical shape is chosen as seen in Figure 6.

Fig. 6. Flat and spherical followers.

TESTING THE ENGINE

After applying these modifications on the engine, a test was carried out to be sure that the engine can run smoothly with six strokes instead of four stroke cycles. The same starter coupled with the engine was used to start the engine. After two or three attempts the engine was running smoothly with six stroke cycles. It has been long known that one of the best ways to monitor the health of an Internal Combustion Engine is to analyze the combustion pressure cycle curves of the individual cylinders [10]. The combustion pressure curve gives information on all phases of the combustion cycle. The cycle by cycle and cylinder-by-cylinder pressure wave-form knowledge is very important information that could have several applications both for engine control and diagnosis. Many researchers have been developed methodologies for the estimation of torques acting on the shaft in order to enhance a new class engine control systems aimed at the optimal management of the engine torque. There are a number of probes designed to allow access to cylinder combustion pressure cycle data. They are however subject to fouling by the byproducts of the combustion process. This fouling leads to calibration errors and the attendant additional maintenance requirements, which may be unacceptable for systems that cannot tolerate significant downtime or operational costs. The effects of poor combustion in one cylinder will cause a change in the angular velocity curve at the point where the affected cylinder has compression rise (near cylinder firing) and in the crankshaft oscillations related to that firing strength. Since many faults can be shown to have a unique effect on the combustion pressure curve and each unique combustion pressure curve will have an effect on the speed of the crankshaft. Different methods are devised to detect misfire in cylinder of operating engine as in [8, 9] are by analyzing the variation of the measured crankshaft’s speed [8], misfire detection using analysis of instantaneous engine exhaust gas pressure, by measurement and analysis of the ionization signal in the combustion chamber, by measurement and analysis of torque, by analysis of combustion chamber pressure, optical method and by combination of these methods. A good overview of the current state of the art was presented in [9]. It is commonly in application in currently manufactured motor vehicles equipped with OBD II system. Order domain methods are suitable for steady-state operating conditions when all the factors that influence the crankshaft’s speed variation may be considered as periodic functions of time (crank angle). In this case, the dynamic behavior of the crankshaft can be described as in [7], if an accurate dynamic model of the crankshaft is available, the calculations are in close agreement with the measurement. All these methods involve a large amount of calculation to detect and identify faulty cylinders. In [6, 7] a simplified approach for detecting power imbalance is suggested by using harmonic torque analysis with effect of engine harmonic orders. A pertinent correlation between the angular motion of the crankshaft and the gas- pressure torque of each cylinder may be developed using the lumped-mass torsional dynamic model of the crankshaft [1]. This model has been extensively used with very good results to predict and control torsional vibrations [6]. Techniques proposed in [10] for detecting misfire require a pressure sensor mounted directly in the combustion chamber. This necessitates maintenance and design considerations that may be unacceptable especially on legacy systems. The art describes a non-invasive technique developed for monitoring combustion pressure cycle related faults. In this work a simple but advanced method of detecting misfire for working medium-speed diesel engine [SL90-SL8800TA] is proposed. A method proposed in [6,7] is used for identification of the cylinder that contributes less to the current torsional vibration level of the crankshaft by using combustion pressure variation in operating medium-speed diesel engine of Kirloskar oil Engine Ltd Pune-03.

2. Problem Formulation The problem studying in this work is to detect cylinder imbalance in operating medium-speed six cylinder diesel engines by using combustion pressure variation and correlating this combustion pressure variation with engine harmonic torque and speed by harmonic order. 3. Crankshaft Dynamics & Harmonic Order

An internal combustion reciprocating engine produces its instantaneous torques, and the resultant mean output torque, as a result of the instantaneous gas pressures acting on each piston throughout the cycle. The actual gas pressures will depend on a number of factors such as whether the engine inhales its charge at atmospheric pressure or at a higher value due to its being pressure-charged, the actual compression ratio used, and the injection advance used at a particular speed and load for a diesel engine.

For a given set of engine conditions a diagram can be obtained giving the variation of the gas pressure within the cylinder against crank angle throughout the whole cycle. This is repeated every 360 crank degrees for a two cycle engine, or 720º (two revolutions) in the case of a four-cycle engine. Since the direction in which the load due to the gas pressure within the cylinder acts on the crank arm varies as the crankshaft rotates, the gas load at any angle must be multiplied by the effective crank radius at that angle. The instantaneous gas torque at any crank angle can be calculated by Eq.1 by considering the in-cylinder pressure (p), piston area (A), piston velocity (V) at angle (θ),

Figure 1. Typical diesel engines single-cylinder instantaneous tangential pressure (torque) curve & its harmonics components tangential pressure curve for four strokes DI diesel engine. Such a periodically repeating curve may be harmonically analyzed by Fourier’s analysis and represented by a constant and a series of harmonically (sinusoidal) varying curves of different amplitudes and phase occurring once, twice, three times, etc. in one complete engine cycle. This is shown for the first three components of the cycle. Since it is convenient to relate these harmonics to the engine speed it is usual to refer to the number of complete harmonic cycles occurring one crank revolution and to refer to them as the order numbers of the harmonics.

For the four cycle diagram shown the 1 ,2, 3, 4, etc. harmonic cycles occur during two crankshaft revolutions, so that when referred to a crankshaft revolution these become respectively the ½, 1, 1½, 2, etc. harmonic orders. In the case of two- cycle engines the order numbers and the harmonics of the cycle are always integers of the same value, as one, engine cycle occurs every crank revolution. It will be noticed that the values of harmonic gas torque components increase with load. There are indications that variations occur with changes in compression ratio and injection advance, as well as with the load.

4. The Harmonic Structure of the Engine Torque & Speed The torque produced by a cylinder has two components, the gas pressure torque (GPT) and the reciprocating inertia torque (RIT). The GPT depends, almost exclusively, on the engine load and could vary from cylinder to cylinder even under steady-state operating conditions. The RIT depends only on engine speed and is fairly uniform for all cylinders of a multi cylinder engine. Under steady-state operating conditions, the total torque (Ti) corresponding to a given cylinder i, may be considered a periodic function of time (crank angle) and expressed as a Fourier series. The Eq.2 expresses the total GPT of a four stroke DI Diesel engine: In this expression, represents the mean value of the GPT, and are the cosine and sine terms of the order k = j/2 of the harmonic components of the total cylinder torque, θ is the crank angle, and K the highest number of harmonic components, necessary to represent the gas pressure torque. While the harmonic components of the GPT have both sine and cosine terms, the harmonic components of the RIT have only integer- order sine terms. Considering a lumped -mass model of the crankshaft and linear equations for the angular motion, the crankshaft’s speed variation during an engine cycle may be quite accurately predicted by superposing the responses of its natural modes to each harmonic component of the total engine torque. The frequencies of the lower harmonic orders are usually far enough from the natural frequencies of the shafting and, for these frequencies, the influence of the higher modes becomes negligible. For a low-frequency excitation, the motion of the shafting is determined mainly by the rigid-body mode. In this case, under the action of a harmonically varying torque,and the corresponding angular speed variation will be

The reciprocating masses. Eq. (4) shows that the kth order harmonic component of the crankshaft’s speed lags the corresponding harmonic term of the engine torque by π/2. This equation may be used to correlate the amplitudes and phases of the lower harmonic components of the resultant torque and of the of measured crankshaft speed. 5. Engine Model Figure 2 illustrates a complete mass-elastic model of a four stroke six cylinder inline diesel engine system. There is a flywheel on the engine shaft to even the rotational speed of the engine shaft. The rectangles in Fig.2 represent masses with link rotating in relation to the shafts. For example, the mass of the piston/crank mechanism of each cylinder is illustrated by rectangles. Dampings are represented by the box/plate symbol and stiffness of shafts is represented by spring symbol. In Fig. 2 J1,… J7 are the inertia of the each cylinder & pulley, k1,… k8 are the stiffness and c1,…c6 are the viscous damping’s respectively. Figure 2. Mass-elastic model of a four stroke six cylinder inline diesel engine. TABLE 1 Engine Basic Data

Engine Type Inline, Four stroke, DI

No. of Cylinder 6

Direction of rotation Anticlockwise

Firing Order 1-5-3-6-2-4

Power output @ 1500rpm 309 H.P

Cylinder Pressure 165 bar

Cylinder Diameter 118 mm

Piston Stroke 135 mm

Compression Ratio 15.5 Mass Elastic Data As per drawing

The frequency and amplitude analysis is carried out by computerized Holzer method for natural frequencies (120.2183Hz 249.2183Hz, and 1183.33Hz). Normal modes shapes are shown in Figure 3.

F=1148vpm F=2379vpm F=9377vpm 1

0

Amplit ude‐1 0 1 2 3 4 5 6 7 8 ‐2 Mass no.

Figure 3. Normal mode shape curves

A phase vector diagram as shown in Figure 4 is drawn for the given engine to analyze the minor and major critical harmonic orders in torsional vibration analysis. It is seen that the sixth orders are the major critical orders of excitation. The corresponding critical speeds of engine operation are; = 1148/6 = 191.330 rpm = 2379/6 = 396.500 rpm =11300/6=1883 .33 rpm Since the sixth order excitation of 3-node vibration mode falls within the operating range of 750 to 2200 rpm, hence the forced vibration analysis is required for this excitation frequency only.

Figure 4. Phase vector diagram 7. Experimental Investigation Extensive experiments were conducted on a four-stroke six cylinder direct injection diesel engine (Kirloskar SL90-SL8800TA). The engine was operated at constant speed and different loads. . To simulate a misfire cylinder, the nut connecting the high-pressure fuel line to the corresponding element of the injection pump was completely unscrewed and cut off was introduced in the fuel supply of the cylinder. By varying the tightness of the high-pressure fuel line, it was possible to reduce gradually the amount of fuel injected into the cylinder from the rated value to zero, to simulate a wide range of malfunctions up to a complete misfire.

The pressures were measured in all cylinders by flush mounted piezoelectric pressure transducers. The mean indicated pressure (MIP) and the gas pressure torque (GPT) of each cylinder were calculated from the pressure traces. The GPT and the measured speed were subjected to a Discrete Fourier Transform (DFT) to determine the amplitudes and phases of their harmonic components stated as above.

The results of the application of this technique to given DI diesel engine are graphically shown in Figure 5 & 6. Figure 5 shows an actual pressure curve generated by the sensor on all six cylinders when engine was working under normal condition. 7.1. Method for Detecting Misfire in Working Engine

It is observed that when the cylinders are uniformly contributing to the total engine torque, the first three harmonic orders (K=½, 1, 1½) play an insignificant role in the frequency spectrum of the total gas-pressure torque and, consequently, appear with a very low contribution in the frequency spectrum of the crankshaft’s speed. If the frequency spectrum of the crankshaft’s speed corresponding to uniform cylinders operation is compared to the spectrum corresponding to a misfired cylinder, one may see that the major difference is produced by the amplitudes of the first three harmonic orders [6]. As far as the cylinders operate uniformly, these amplitudes are maintained under a certain limit. Once a cylinder starts to reduce its contribution, the amplitudes of the first three harmonic orders start increasing. These amplitudes may be used to determine the degree by which a cylinder reduces its contribution to the total gas pressure torque. The identification of the faulty cylinder may be achieved by analyzing the phases of the lowest three harmonic orders. (a) is drawn by reconstructing the pressure traces of the six cylinders in a sequence corresponding to the firing order (1-5-3-6-2-4) with cylinder 6 is disconnected. (B, c, d) shows the lowest three harmonic orders of the measured speed, respecting the measured amplitudes and phases. It is seen that, only for the expansion stroke of cylinder 6 all three harmonic curves have, simultaneously, a negative slope. In the phase angle diagrams as of these orders, the vector corresponding to the harmonic component of the measured speed is also represented. One may see that, for each of the three considered orders, the vectors are pointing toward the group of cylinders that produce less work. The cylinder that is identified three times among the less productive cylinders is the misfired one. Figure 6. ( a) Actual Cylinder Pressure Curve (Cylinder 5 cut-off (b) ½ order (c) 1 order (c)1½ order Based on this observation, the following method may be developed. 1.The phase-angle diagrams as shown in Fig.7, considering the firing order of the engine, are drawn for the lowest three harmonic orders placing in the top dead center (TDC) the cylinder that fires at 0º in the considered cycle. 2.On these phase angle diagrams, the corresponding vectors of the measured speed are represented in a system of co-ordinate axes. 3.The cylinders toward which the vectors are pointing are the less contributors and receive a ‘‘-’’ mark. If there are cylinders that receive a ‘‘-’’ mark for all three harmonic orders, they are clearly identified as less contributors to the engine total output. This procedure is presented in Table 2 for the case shown in Figure 7. 4.This method is able to identify a faulty cylinder as soon as its contribution dropped below 20 % with respect to the contribution of the other cylinders.

Figure 7. Detection of a misfire from the phases of the lowest harmonic orders ½, 1, and 1½, of the crankshaft’s speed Features and advantages

Piston failure CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

Literature review is a body of text that aims to review the critical points of current knowledge and or scientific methodological approaches on the topic related to the study. In this chapter, literature will give information about the background knowledge in internal combustion engine field and other technologies that being used as references to generate idea to conduct this study. 2.2 Background of Internal Combustion (IC) Engine

An engine is a device which transforms the chemical energy of the fuel into thermal energy and uses this energy to produce mechanical work (Crouse and Anglin 2005). The engine is also called ‘heat engine’ because they normally convert thermal energy into mechanical work. When the fuel burns with the presence of air, a large amount of energy is release. The released energy was then converted to useful work by a heat engine with the help of a working fluid. The heat engines can be classified into two groups: a) External Combustion Engine (EC engines) b) Internal Combustion Engines (IC engines)

In EC engine, the combustion process will take place outside the cylinder. The heat energy released from the fuel was used to raise the high-pressure steam in a boiler from water. In this case, steam is a working fluid which enters the cylinder of a steam engine to perform mechanical work. The product of combustion of fuel do not enter the engine’s cylinder, thus they do not form the working fluid.

The examples of EC engine are the steam turbine in a steam power plant, Sterling engines and a closed cycle gas turbine plant. Here, normally the air act as the working substance which completes the thermodynamics cycle and the product of the combustion process do not enter the turbine. The steam turbine is the most popular EC engine used for large electric power generation. In IC engine, the combustion process of the fuel can either take place inside the engine’s cylinder or the products of the combustion process enter the cylinder as a working fluid. In reciprocating engines having a cylinder and piston, the combustion process of fuel will take place inside the cylinder and this type of engine may be called intermittent internal combustion engines. In an open cycle gas turbine plant, the product of the combustion of fuel enters the gas turbine and work is obtained in the form of rotation of the turbine shaft. This type of turbine is an example of a continuous IC engine. The intermittent IC engines are the most popular because of their use in theprime transportation in motor vehicles, and reciprocating engines are the typically used one. The reciprocating engine mechanism consists of piston which moves in a cylinder and forms a movable gas-tight seal. Through connecting rod and a crankshaft arrangement, the reciprocating motion of a piston is converted to rotary motion of a crankshaft. The main advantage of IC engines over EC engines are: a) Greater mechanical efficiency b) Higher power output per unit weight because of the absence of auxiliary units like boiler, condenser and feed pump c) Lower initial cost d) Higher brake thermal efficiency because only small fraction of heat energy of the fuel is dissipated to the cooling system

The advantages of IC engine accrue from the fact that they work at an average temperature which is much below the maximum temperature of the working fluid in the cycle. The disadvantages of the IC engines over EC engines are: a) The IC engines cannot use solid fuel which is cheaper. b) The IC engines are not self-starting whereas the EC engines have high starting torque c) The intermittent IC engines have reciprocating parts, thus they are susceptible to vibration problems 2.2.1 Classification of IC Engines There are different types of IC engines that can be classified on the following Basis (Gupta, 2006): Thermodynamics cycle

 Constant volume heat supplied or Otto cycle

 Constant pressure heat supplied or Diesel cycle

 Partly constant volume and partly constant pressure heat supplied or Dual cycle

 Joule or Brayton cycle working cycle

 Four-stroke cycle naturally aspirated, supercharge and turbocharged

 Two-stroke cycle naturally aspirated, supercharge and turbocharged Types of fuel • Light oil engines using kerosene or petrol.

• Heavy oil engines using diesel or mineral oils.

• Gas engines using gaseous fuels like natural gas, liquefied petroleum gas (LPG) and hydrogen. • Bi-fuel engines. In these engines the gas is used as the basic fuel and the liquid fuel is used for starting the engine. Method of ignition • Spark ignition (SI) used in conventional petrol engines • Compression ignition (CI) used in conventional diesel engines • Pilot injection of fuel oil in gas engines Method of fuel supply • Fuel supply through carburettor. In petrol engine, the fuel is mixed with air in the carburettor and the charge enters into the cylinders during the suction stroke. • Multi-point port injection (MPI), used in modern spark-ignition (SI) engine. • Single point throttle body injection. This method is also applied to SI engine. • Fuel injection at high pressure into the engine cylinder. Used in diesel engines or compression-ignition (CI) engine Type of cooling • Water cooled engine. The cylinder walls are cooled by circulating water in the jacket surrounding the cylinder • Air cooled engines, the atmospheric air blows over the hot surfaces. Common vehicle with this type of cooling is motor cycles and scooters Number of cylinder • Single cylinder. This engine gives one power stroke per crank revolution (2-stroke) and two revolutions (4-stroke). The torque pulses are widely spaced, and engine vibration and smoothness are significant problems. Used in small engine application where engine size is more important. • Multi-cylinder. This engines spread out the displacement volume amongst multiple cylinder. Increased frequency of power stroke produces smoother torque characteristic and the engines balance is better than single cylinder. Basic engine design • Reciprocating engine, subdivided by the arrangement of cylinders, for example, in-line engines, V-engines, opposed cylinder engines, opposed piston engines and radial engines • Rotary engines (wankel engines)

2.2.2 Principle Operation of IC Engine The action or event in the spark-ignition engine can be divided into four parts, or the piston strokes (Crouse and Anglin 2005). Those parts are intake, compression, power, and exhaust. Each stroke is the movement of the piston from Bottom Dead Centre (BDC) to Top Dead Centre (TDC) or from TDC to BDC. Is a four-stroke cycle engine, one complete cycle of event in the engine cylinder requires two complete revolution of the crankshaft.

Figure 2.1: The strokes of engine

a) Intake Stroke

During the intake stroke of a spark-ignition engine, the intake valve is open and the piston is moving downward. This movement will create a partial vacuum above the piston. Atmospheric pressure forces air-fuel mixture to flow through the intake port and into the cylinder. The fuel system supplies the mixture like carburettor or injector (Crouse and Anglin 2005). As the piston passes through the BDC, the intake valve closes. This seal off the upper end of the cylinder. b) Compression Stroke After the piston passes BDC, it starts moving up. Both valves are closed. The upwards moving piston compresses the air-fuel mixture into a smaller space between top of the piston and the cylinder head. This space is the combustion chamber. In typical spark-ignition engines, the mixture is compressed into one-eight or less of its original volume (Crouse and Anglin 2005). The amount that the mixture is compressed is called the compression ratio (CR). This is the ratio between the original volume (before being compress) and the compressed volume in the combustion chamber. If the mixture is compressed to one-eight of its original volume, then the compression ratio is 8:1. c) Power/Expansion Stroke As the piston move nears TDC at the end of the compression stroke, an electric spark jumps the gap at the spark plug. The heat from the spark ignites the compressed the air-fuel mixture. It burns rapidly, producing a high temperature. This high temperature cause very high pressure which pushes down the top of the piston. The connecting rod carries the force to the crankshaft, which turns to move the drive wheels. Power is obtain during this stroke. d) Exhaust Stroke As the piston approaches BDC on the power stroke, the exhaust valve will open. After passing through BDC, the piston move up again and the burn gases escape through the open exhaust port. As the piston approached TDC, the intake valve will open. When the piston passes through TDC and starts moving down again, the exhaust valve will close and another intake stroke will begin. The whole cycle will repeat again continuously in all cylinder for as long as the engine running. 2.2.3 Four-Stroke and Two-Stroke Engines In four-stroke cycle SI engine, the cycle of operation is completed in four- strokes of the piston or in two revolution of the crankshaft. Therefore crank angle (CA) of 720° is required to complete the cycle (Gupta, 2006). The individual stroke of the cycle is:

 Intake or suction stroke  Compression stroke  Expansion or power stroke  Exhaust stroke

Since each cylinder of a four-stroke engine completes all the operations in two engine revolution, for one complete cycle, there is only one power stroke while the crankshaft makes two revolutions (Gupta, 2006). In two-stroke engine, all the processes are the same, but there are only two stroke involved. Those two strokes of the cycle are completed once during each revolution of the crankshaft. Since there is only one power stroke per revolution of the crankshaft, the power output of a two-stroke engine will be twice that of a four-stroke engine with the same displacement (Gupta, 2006).

Stroke 1: Air fuel mixture is introduced into the cylinder and then compressed, combustion initiated at the end of the stroke Stroke 2: combustion products expand doing work and then exhausted

In these engines, the crankcase is sealed and the piston’s outward motion is used to pressurize the air-fuel mixture in the crankcase, as shown in figure 2.2. Instead of having valves (intake and exhaust), they are replaced by the opening on the lower portion of the cylinder (Cengel and Boles, 2007). Two-stroke engines are generally less efficient than their four-stroke counterparts because of the incomplete expulsion of the exhaust gases and there are some fresh air-fuel mixture escaping along with exhaust gases (Cengel and Boles, 2007). However, they are relatively simple and inexpensive. They also have high power-to-weight and power-to-volume ratios (Cengel and Boles, 2007). Those facts make them suitable for application requiring small size and weight such as motorcycle, chain saw and lawn mowers.

Figure 2.2: Two-stroke SI engine

Source: Cengel and Boles, 2007. 2.2.4 Comparison of Four-Stroke and six –stroke Engines

Table 2.1: Comparison of four-stroke and six-stroke engines

Four-stroke engine six –stroke engine - one power stroke obtain in - one power stroke obtain per every two revolution revolution of the crankshaft (the of the crankshaft (the cycle complete cycle is in completed in two revolution of the one revolution of the crankshaft) crankshaft) - The turning movement of the - The movement of the shaft is shaft is more uniform, hence non-uniform because only one lighter flywheel can be used. power stroke obtain in two revolution of crankshaft, hence heavier fly is needed to rotate the - The power produce for the same size shaft uniformly of - The power produce for the same size of the engine is less and for the same power the engine is more and for the same output, the engine is bigger in size power output, the engine is smaller in - It have valves and valve size mechanism - it has ports. Some engine are equipped with exhaust valve or - higher initial cost because heavy reed valve weight - Lower initial cost because it is and valve mechanism lighter and have no valve mechanism Piston requirements:

1. Rigidly to withstand high pressure.

2. Lightness to reduce the weight of the reciprocating masses and so enable higher engine speeds.

3. Good heat conductivity to reduce the risk of detonation so allowing higher compression ratio.

4. Silence in operation.

5. Material having low expansion and provision to allow for different expansion rates of Cast iron cylinder block and aluminum piston.

6. Correctly formed skirt to give uniform bearing under working conditions.

Classification of pistons:

Considering the multitude of engine types and the largely different operating requirements for many applications, a great number of piston types are developed and in use today.

The most important piston types and their primary field of application shall be described as follows:

 Pistons for automotive gasoline engines (4-stroke cycles).

 Pistons for automotive diesel engines.

 Pistons for commercial vehicle diesel engines.

 Pistons for locomotive, stationary and ship diesel engines.

 Pistons for motor sports. Pistons for automotive gasoline engines:

In 2-cycle engines, mono-metal pistons of either window or full-skirt type are the standard. Dictated by the production process, forged pistons are mono- metal pistons in every case. Aluminum materials for pistons satisfy many requirements demanded of modern pistons. The low density allows low weight and reduced mass forces of the reciprocating piston. High heat conductivity results in an acceptable temperature level, and the good strength characteristics at elevated temperatures are favorable for deformation and cracking resistance.

The Autothermik piston has found worldwide application in automotive gasoline engines. With the application of hydrodynamic, form of the piston skirt, the adaptability to the requirements of modern engines results in Hydrothermik piston. Further development to Hydrothermik piston is Autothermik piston, where the heat flow from the piston top to the skirt is not interrupted since, for strength reasons, the slots in the oil ring groove were eliminated. Hydrothermik piston and Autothermik pistons are predominantly used in high-powered automotive gasoline engines. Pistons for automotive diesel engines:

Automotive diesel engines that work according to the pre- chamber, swirl chamber, or direct injection principle, operate under higher combustion gas pressures and temperatures. Load application for the first ring groove with regard to pressure and impact wear is higher than in pistons for gasoline engines. Using hypereutectic alloys featuring higher silicon content in the aluminum silicon alloy, the wear resistance can be increased and the heat expansion reduced for naturally aspirated engines, thus making smaller installation clearances possible. Thus, forged hypereutectic mono-metal pistons found widespread application in automotive diesel engines.

Pistons for commercial vehicle diesel engines:

Today, the standard design for truck diesel engines is the ring carrier piston. These pistons are produced by the gravity permanent mold casting process. The pistons are generally made of eutectic aluminum-silicon alloys. The Autothermatik piston was also used in air-cooled diesel engines, which were subjected to frequent cyclic load operation. Pistons for locomotive, stationary and ship diesel engines:

Relatively low cyclic load conditions in stationary power plants, ship propulsion units, commuter rail cars and locomotive engines made the application of aluminum full-skirt pistons possible over many years.

With these pistons, the top and ring belt area is laid out rigidly and offers adequate cross-sections for heat flow. Such pistons with ring carriers and cooling coil or ring-shaped cooling galleries are either cast, or the forged piston body and the cast ring band, including the ring carrier and the cooling gallery, are welded together using the electron beam process.

Pistons for motor sports:

Motor sports demand and promote technical progress. Maximum wear and tear tests during motor sports yield practical results over and above the load limits of designs and materials.

The maximum power output required during motor sports stipulates lightweight high-speed engines with correspondingly high combustion pressures. For the piston, this means high strength properties and minimum weight.

Main Components of Pistons:

Fig: the important components of Piston are shown in figure. The most essential areas of the piston are the piston top, the ring belt including the top land, the pin support and the skir, The Piston top is part of the combustion chamber. In gasoline engines, it can be flat, raised or recessed. In diesel engines, the combustion chamber bowl is usually located in the piston top. The ring belt area usually consists of three ring grooves to accept the piston rings, whose function is to seal against gas and oil peaks. Ring lands are located between the ring grooves. The land above the first piston ring is called the top l The Pin support constitutes the bearing for the piston pin in the piston. It is one of the most highly loaded zones of the pist The Piston skirt, which more or less wraps around the lower part of the piston, takes up the side loads and ensures straight guidance of the piston.

Fig Location of piston in 4 stroke and 6 stroke engine

Today almost all manufacturers of four cylinder engines for automobiles produce the inline-four layout, with Subaru's flat-four being a notable exception, and so four cylinder is synonymous with and a more widely used term than inline-four. The inline-four is the most common engine configuration in modern cars, while the V6 is the second most popular. In the late 2000s, with auto manufacturers making efforts to increase fuel efficiency and reduce emissions, due to the high price of oil and the economic recession, the proportion of new vehicles with four cylinder engines (largely of the inline-four type) has risen from 30 percent to 47 percent between 2005 and 2008, particularly in mid-size vehicles where a decreasing number of buyers have chosen the V6 performance option. Usually found in four- and six-cylinder configurations, the straight engine, or inline engine is an internal combustion engine with all cylinders aligned in one row, with no offset.

A straight engine is considerably easier to build than an otherwise equivalent horizontally opposed or V-engine, because both the cylinder bank and crankshaft can be milled from a single metal casting, and it requires fewer cylinder heads and camshafts. In-line engines are also smaller in overall physical dimensions than designs such as the radial, and can be mounted in any direction. Straight configurations are simpler than their V-shaped counterparts. They have a support bearing between each piston as compared to "flat and V" engines which have support bearings between every two pistons. Although six-cylinder engines are inherently balanced, the four- cylinder models are inherently off balance and rough, unlike 90 degree V fours and horizontally opposed 'boxer' 4 cylinders.

An even-firing inline-four engine is in primary balance because the pistons are moving in pairs, and one pair of pistons is always moving up at the same time as the other pair is moving down. However, piston acceleration and deceleration are greater in the top half of the crankshaft rotation than in the bottom half, because the connecting rods are not infinitely long, resulting in a non sinusoidal motion. As a result, two pistons are always accelerating faster in one direction, while the other two are accelerating more slowly in the other direction, which leads to a secondary dynamic imbalance that causes an up-and- down vibration at twice crankshaft speed. This imbalance is tolerable in a small, low-displacement, low-power configuration, but the vibrations get worse with increasing size and power.

The reason for the piston's higher speed during the 180° rotation from mid-stroke through top-dead-centre, and back to mid-stroke, is that the minor contribution to the piston's up/down movement from the connecting rod's change of angle here has the same direction as the major contribution to the piston's up/down movement from the up/down movement of the crank pin. By contrast, during the 180° rotation from mid-stroke through bottom- dead-centre and back to mid-stroke, the minor contribution to the piston's up/down movement from the connecting rod's change of angle has the opposite direction of the major contribution to the piston's up/down movement from the up/down movement of the crank pin. Four cylinder engines also have a smoothness problem in that the power strokes of the pistons do not overlap. With four cylinders and four strokes to complete in the four-stroke cycle, each piston must complete its power stroke and come to a complete stop before the next piston can start a new power stroke, resulting in a pause between each power stroke and a pulsating delivery of power. In engines with more cylinders, the power strokes overlap, which gives them a smoother delivery of power and less vibration than a four can achieve. As a result, six- and eight- cylinder engines are generally used in more luxurious and expensive cars when a straight engine is mounted at an angle from the vertical it is called a slant engine. Chrysler's Slant 6 was used in many models in the 1960s and 1970s. Honda also often mounts its straight-4 and straight-5 engines at a slant, as on the Honda S2000 and Acura Vigor. SAAB first used an inline-4 tilted at 45 degrees for the Saab 99, but later versions of the engine were less tilted. Two main factors have led to the recent decline of the straight-6 in automotive applications. First, Lanch ester balance shafts, an old idea reintroduced by Mitsubishi in the 1980s to overcome the natural imbalance of the straight-4 engine and rapidly adopted by many other manufacturers, have made both straight-4 and V6-engine smoother- running; the greater smoothness of the straight-6 layout is no longer such an advantage. Second, fuel consumption became more important, as cars became smaller and more space-efficient. The engine bay of a modern small or medium car, typically designed for a straight-4, often does not have room for a straight-6, but can fit a V6 with only minor modifications. Straight-6 engines are used in some models from BMW, Ford Australia, Chevrolet, GMC, Toyota, Suzuki and Volvo Cars.

Main components of the engine Piston is one of the main parts in the engine. Its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a connecting rod. Since the piston is the main reciprocating part of an engine, its movement creates an imbalance. This imbalance generally manifests itself as a vibration, which causes the engine to be perceivably harsh. The friction between the walls of the cylinder and the piston rings eventually results in wear, reducing the effective life of the mechanism. The sound generated by a reciprocating engine can be intolerable and as a result, many reciprocating engines rely on heavy noise suppression equipment to diminish droning and loudness. To transmit the energy of the piston to the crank, the piston is connected to a connecting rod which is in turn connected to the crank. Because the linear movement of the piston must be converted to a rotational movement of the crank, mechanical loss is experienced as a consequence. Overall, this leads to a decrease in the overall efficiency of the combustion process. The motion of the crank shaft is not smooth, since energy supplied by the piston is not continuous and it is impulsive in nature. To address this, manufacturers fit heavy flywheels which supply constant inertia to the crank. Balance shafts are also fitted to some engines, and diminish the instability generated by the pistons movement. To supply the fuel and remove the exhaust fumes from the cylinder there is a need for valves and camshafts. During opening and closing of the valves, mechanical noise and vibrations may be encountered

Pistons are commonly made of a cast aluminum alloy for excellent and lightweight thermal conductivity. Thermal conductivity is the ability of a material to conduct and transfer heat. Aluminum expands when heated and proper clearance must be provided to maintain free piston movement in the cylinder bore. Insufficient clearance can cause the piston to seize in the cylinder. Excessive clearance can cause a loss of compression and an increase in piston noise. Piston features include the piston head, piston pin bore, piston pin, skirt, ring grooves, ring lands, and piston rings. The piston head is the top surface (closest to the cylinder head) of the piston which is subjected to tremendous forces and heat during normal engine operation. A piston pin bore is a through hole in the side of the piston perpendicular to piston travel that receives the piston pin. A piston pin is a hollow shaft that connects the small end of the connecting rod to the piston. The skirt of a piston is the portion of the piston closest to the crankshaft that helps align the piston as it moves in the cylinder bore. Some skirts have profiles cut into them to reduce piston mass and to provide clearance for the rotating crankshaft counterweights. Chapter -3 Analysis

Cylinder simulation part

ANALYSIS OF CRANKSHAFT - CAST

CONCLUSIO