College of Engineering & Technology Akola
COLLEGE OF ENGINEERING AND TECHNOLOGY, AKOLA
DEPARTMENT OF MECHANICAL ENGINEERING
NAME : ......
SUBJECT : ENERGY CONVERSION LAB
CLASS : SECOND YEAR MECHANICAL ENGG.
ROLL NO : ......
NAME OF THE FACULTY: ROSHAN D. BHAGAT
DESIGNATION: ASSIST. PROFESSOR
BRANCH: MECHANICAL ENGINEERING SUBJECT: EC-1LAB
SEMESTER: FOURTH ACADEMIC YEAR 2016-2017
1 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
DEPARTMENT OF MECHANICAL ENGINEERING
CERTIFICATE
This is to certify that Mr. / Miss...... has satisfactorily completed the course of experiments in ENERGY CONVERSION LAB as prescribed by the Sant Gadge Baba Amravati University in the laboratory of college for the academic year 2016-2017
Date: Signature of Teacher In charge of the Batch
Head of department Name of the candidate Registration no Roll no. Date of practical examination
2 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
INDEX
SR.NO NAME OF EXPERIMENT DATE SIGN
1 Study of water tube boiler babcock and Wilcox
2 Study of locomotive boiler
3 Study of high pressure boiler
4 Study of boiler accessories
5 Trial on boiler and heat balance sheet
6 Study of boiler mounting
7 Study and trial on steam turbine
8 Study of condenser
9 Study of condensate and air extraction pump
10 Study of steam power plant
3 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 1
Aim: Study of water tube Babcock and Wilcox water tube boiler
Apparatus: Babcock and Wilcox water tube boiler
Theory: The water tube boiler used exclusively when pressure above 10 bars and capacity in excess of 7000 kg of steam per hour is required. Babcock and Wilcox water tube boiler is an example of horizontal boiler and may be design for stationary and marine purpose.
Fig shows the Babcock and Wilcox boiler with the longitudinal drum. It consists of drum connected to a series of front end and rear end header by short riser tube. To these headers are connected a series of inclined water tubes of solid drawn mild steel. D= Drum, PG= Pressure gauge, DTH=Down take header, UTH=Up take header, ST=Superheating tube, WT=Water tube, SV= safety valve, BP=Baffle plate, MSV=Main stop valve, D=door, APP=Antipriming pipe, G=Grate, FD=Fire door, MC= Mud collector, FV= Feed valve, WLG= Water level gauge. The angle of inclination of water tube to the horizontal is 150 or more. A hand hole is provided in the header in front of each tube for cleaning and inspection of the tubes. A feed valve is provided to fill the drum and inclined tube with the water the level of which is indicated by the water level indicator. Through the fire door the fuel is supplied to grate where it is burnt. The hot gases are forced to move upward between the tubes by baffles plate provided. The water from the water from the drum flows through the inclined tubes via down take header and goes back into the shell in t e form of water and steam via uptake header. The steam gets collected in the steam space of drum. The steam then enters through the antipriming pipe and flows in the superheater tubes where it is further heated and is finally taken out through the main stop valve and supplied to the engine when needed.
4 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
At the lowest point of the boiler is provided with mud collector to remove the mud particle through a blow down cock. The entire boiler except the furnace is hung by means of metallic slings or straps of wrought iron girders supported on pillars. This arrangement enables the drum and the tube to expand or contract freely. The brickwork around the boiler encloses the furnace and the hot gases. The various mounting used in the boiler is as shown in fig. A Babcock and Wilcox water tube boiler with cross draw differs from longitudinal drum boiler in a way that how drum is place with reference to the axis of the water tube of the boiler. The longitudinal drum restricts the number of tubes that can be connected to one drum circumferentially a limits the capacity of the boiler. In case of cross drum there is no limitation of the number of connecting tubes. Applications of Babcock and Wilcox water tube boiler
Result: Thus water tube boiler is studied. Sign :......
5 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 2
Aim: study of locomotive boiler
Apparatus: model of locomotive boiler
Theory The locomotive boiler is mainly employed in locomotive through it may also be used as stationary boiler. It is compact and its capacity for steam production is quite high for its size as it can raise large quantities of steam rapidly.
The locomotive boiler consists of cylindrical barrel with a rectangular fire box at one end and a smoke box at the other end. The coal is introduced through the fire hole into the grate which is placed at the bottom of the fire box. The hot gases which are generated due to burning of the coal are deflected by an arch of fire bricks, so that walls of fire box may be heated properly. The fire box is entirely surrounded by water except for the fire hole and the ash pit which is situated below the fire box which is fitted with dampers at its front and back ends. The dampers control the flow of air to the grate. The hot gases pass from the fire box to the smoke box through a series of ire tube and then are discharged into the atmosphere through the chimney. The fire tubes are placed inside the barrel. Some of these tubes are of larger diameter and the other of the smaller diameter. The superheater tubes are placed inside the fire tube of larger diameter. The heat of the hot gases is transmitted into the water the heating surface of the fire tubes. The steam generated is collected over the water surfaces. A dome shaped chamber is known as steam dome is fitted on the upper part of the barrel, from where the steam flows through a steam pipe into the chamber. The flow of steam is regulated by means of regulator. From the chamber it passes through the superheater tube
6 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola and returns to the superheated steam chamber from which it is led to the cylinders through the pipes, one to each cylinder. In this boiler natural draught cannot be obtained because it requires a very high chimney which cannot be provided on a locomotive since it has to run on rails. Thus some artificial arrangement has to be used to produce a correct draught. As such the draught here is produced by exhaust steam from the cylinder which is discharge through the blast pipe to the chimney. When the locomotive is standing and no exhaust steam is available from the engine fresh steam from the boiler is used for the purpose. The various boiler mounting include Safety valve, pressure gauge, water level indicator, fusible plug, man hole, blow off cock and feed check valve. Advantages of locomotive boiler High steam capacity Low cost of construction Portability Low cost of installation Compact Demerits There are chances to corrosion and scale formation in the water legs due to the accumulation of sediment and the mud particle. It is difficult to clean some water space. Large flat surfaces need bracing. It cannot carry high overloads without being damaged by overheating There are practical constructional limits for pressure and capacity which do not meet requirement.
Result : Thus locomotive boiler is studied with its application. Sign:......
7 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 3
Aim: study of high pressure boiler.
Apparatus: model of lamont boiler, loeffler boiler, benson boiler.
Theory:
Lamont boiler
This boiler works on forced circulation and the circulation is maintained by centrifugal pump driven by steam turbine using steam from the boiler. For emergency an electrically driven pump may be used. Fig shows the Lamont boiler. The feed water passes through the economiser to the drum from which it is drawn to the circulation pump. The pump delivers the feed water to the tube evaporating sections which in turns send a mixture of steam and water to the drum. The steam in the drum is then drawn through the superheater. The superheated steam so obtained is then supplied to the prime mover. These boilers are built to generate 45 to 50 tonnes of superheated steam at a pressure of 130 bar and temperature of 1500퐶.
Loeffler boiler In Lamont boiler the major difficulty experienced is the deposition of salt and sediment on the inner surfaces of the water tube. The deposition reduces the heat transfer and ultimately the generating capacity of the boiler. This further increases the danger of overheating the tubes due to salt deposition as it has high thermal resistances. This difficulty is overcome by loeffler boiler by preventing the flow of water into the boiler tubes. The boiler also makes the used of forced circulation. Its novel principle is that the evaporating of feed water by means of superheated steam from the superheater, the hot gases from the furnaces being primarily used for superheating purpose. Fig shows the diagrammatical view of loeffler boiler. The high pressure feed pump draws water through the economiser and deliver it into the evaporating drum. The steam circulating pump draws saturated steam from the evaporating drum and passes it through
8 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola radiant and convective superheater where steam is heated to required temperature form the superheater about one third of superheated steam passes to the prime mover the remaining two third of steam passing through the water in the evaporating drum in order to evaporate the feed water.
The boiler can carry higher salt concentration than any other type and is more compact than indirectly heated boiler having natural circulation. These qualities fit it for land or sea transport power generation. Loeffler boiler with generating capacity of 100 tonnes/hr and operating at 140 bar. Benson boiler In lamont boiler the main difficulty experienced is the formation and attachment of bubbles on the inner surfaces of the heating tubes.
9 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
The attached bubble to the surfaces reduce the heat flow and steam generation as it offers high thermal resistance than water film. If the boiler pressure was raised to critical pressure of 225 atm. The steam and water have the same density and therefore the danger of bubble formation can be easily eliminated. The fig shows the Benson boiler. This boiler does not use any drum. The feed water after circulation through the economic tubes flows through the radiant parallel tube section to evaporate partly. The steam water mixture produced then moves to the transit section where this mixture is converted into steam. The steam is now passed through the convection superheater and finally supplied to the prime mover.
Result : Thus high pressure boiler is studied.
10 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 4
Aim : study of boiler accessories
Apparatus: Feed Pump, Injector, Economiser, Air Preheater, Superheater.
Theory Feed pump The feed pump is the pump which is used to delivered the feed water to the boiler. It is desirable that the quantity of water supplied be at least equal to that evaporated and supplied to the engine. Two type of pumps which are commonly used as feed pump are reciprocating pump and rotary pump.
The above figure shows duplex direct acting steam pump. Here there are two single steam cylinder placed side by side. Slide valves distribute the steam in each cylinder. The slide valve in each cylinder steam chest is operated by the crosshead on the piston rod of the opposite cylinder through an arrangement of rod and rocker arm. The feed pump is generally double acting. On each side of the pump plunger there are suction and discharge valve. The pump works alternately and consequently continuous flow of water is maintained. Double feed pump is commonly employed for medium size boiler.
Air preheater The function of air preheater is used to increase the temperature of air it enters the furnace. It is generally placed after the economiser so the flue gases pass through the economiser and then to the air preheater. Air preheater consist of plates or tubes with hot gases on one side and air on the other. It preheats the air to be supplied to the furnace. Preheated air accelerates the combustion and facilitates the burning of coal.
11 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Fig shows the tabular air preheater. After leaving the boiler or economiser the gaseous products of combustion travels through the inside the tube of air preheater in a direction opposite to that of air travel and transfer some of their heat to the air to be supplied to the furnace. Thus the air gets initially heated before being supplied to the furnace. The gases reverse their direction near the bottom of the air heater, and a soot hopper is fitted to the bottom of air heater casing to collect soot.
12 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Injector
The function of an injector is to feed the water into the boiler. It is commonly employed for vertical and locomotive boiler. And does not find any application in large capacity high pressure. It is also used where the space is not available for the installation of a feed pump. In injector water is delivered to boiler by steam pressure. The kinetic energy of steam is used to increase the pressure and velocity of the feed water. The fig shows an injector. It consist of a spindle P a steam cone S, a combine cone K, a delivery cone D, and handle H, with a pointer T. The spindle upper end is provided with a handle while the lower end serves the purpose of a valve. The pointer on the handle indicates the shut and open position of the valve. The lower part of the spindle has a screw which works in nut which is integral part of steam cone. The key E checks the rotation of the steam cone. With the rotation of the handle steam cone moves up or down and consequently the valve controls the steams flow through the steam cone. The steam enters through the steam pipe A, while the feed water enters through the water pipe B. The flow of water is also regulated due to sliding motion of the steam cone by its lower end. The water mixes with the steam at the combining cone where it is condensed. The mixture then passes through the delivery cone and there its kinetic energy is converted into pressure energy the final pressure must be greater than the steam pressure of boiler otherwise water will not enter into the boiler. The excess water finds its way through the overflow pipe.
Economiser An economiser is a device in which waste heat of flue gases is utilise for heating the feed water. Economiser of the two types. Independent type and integral type. Fig shows the independent type vertical tube economiser. It is employed for boilers of medium pressure
13 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola range upto 25 bar. It consist of large number of vertical cast iron pipes P which are connected with two horizontal pipes, one at the top and other at the bottom. A is the bottom pipe through which the feed water is pumped into the economiser flows to the boiler. The flue gases move around the pipes in the direction opposite to the flow of water. Consequently, heat transfer through the surface of the pipe takes place and water is therby heated. A blow of cock is provided at the back end of the vertical pipe to remove the sediments deposited in the bottom boxes. The soot of the flue gases gets deposited on the pipes reduces the effieciency of the economiser. To prevent the soot deposits, the scrappers S move up and down to keep the external surface of the pipe clean.
14 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Sugden Superheater The function of superheater is to increase the temperature of the steam above its saturation point. The superheater is very important accessory of a boiler and can be used for both on fire tube and water tube boiler. The small boilers are not commonly provided
Superheated steam has the following advantages. Steam consumption to the engine is reduce or the turbine is reduced Losses due to condensation in the cylinder and the steam pipe are reduced Erosion of turbine blade is eliminated. Efficiency of steam power plant is increased. Convection superheater makes the use of heat in flue gases where as radiant superheater is place in the furnace and wall tube receive the heat from the burning fuel through the
15 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola radiant process. The radiant type of superheater is generally used where a high amount of superheat temperature is required. Fig shows the sugden superheater installed in Lancashire boiler. It consists of two a steel header to which is attached solid drawn u tube of steel. These tubes are arranged in groups of four and one pair of the header generally carries ten of these groups or total of forty tubes. The steam from the boiler enters and leaves the headers as shown by the arrows. Fig also shows how the steam pipes may be arranged so as to pass the steam through the superheater or direct to the main steam pipe. When steam is taken from the boiler are opened.
Steam separator The steam available from the boiler may be wet dry or superheated but in many cases there will be loss of heat from it during its passage through the steam pipe from the boiler the engine tending to produce wetness. The use of wet steam in an engine or turbine is un economical beside involving some risk. Hence it is usual to endeavour to separate any water that may be present from the steam before the latter enters the engine. This is accomplished by the use of steam separator. Thus the function of steam separator is to remove the entrained water particle from the steam conveyed to the sea engine or turbine. It is installed as close to the seam engine as possible on the main steam pipe from the boiler. The fig shows the baffle plate steam separator. The steam enters the flange A and flows down. In its passage it strikes the baffles B as a result it gets deflected water particle having greater density and greater inertia fall to the bottom of the separator. The drier steam discharges through the flange C. To see the level of water collected a water gauge is provided. Water collected in the vessel is removed at interval through drain pipe D.
Result : Thus the boiler accessories are studied. Sign:......
16 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 5
Aim:- To prepare heat balance sheet for given boiler.
Heat losses in the boiler:- The efficiency of boiler is never 100 % as only a portion of heat supplied by the fuel is utilized rest of it is lost:- 1. Heat carried away by dry product of combustion. 2. Heat carried away by the steam product by the combustion of hydrogen present in fuel. 3. Heat carried away by moisture in fuel and air. 4. Heat loss due to incomplete combustion of carbon to carbon monoxide instead of carbon dioxide and thus escape of combustable matter in the flue gases and ash. 5. Heat loss due to radiation.
Method of minimizing the heat loss:- 1. The heat loss to chimney gases may be minimized by installing an economiser in between the boiler and chimney. 2. Loss of heat may be minimized by providing the boiler with an effective draught system which will ensure sufficient supply of air through the fuel in furnace. 3. Heat loss due to unburnt fuel which may fall into ash pit may be minimized by properly sizing of coal. 4. Heat loss due to moisture content in the fuel may be minimized by making the fuel dry before charging into the boiler furnace. 5. Heat loss due to external radiation may be minimized by providing effective covering of insulating material on the boiler parts which are liable to radiate heat.
Theory:- The boiler circulation are generally based upon the high calorific value of 1 kg of fuel considered as 100 %. The term for heat balanced sheet explain earlier.
Heat losses in boiler plant Following are the heat losses occurs in boiler point Heat lost due to flue gases Heat lost due to incomplete combustion Heat lost due to unburnt fuel Convection and radiation loss
Heat lost to flue gases
The flue gases contain the dry products of combustion as well as steam generated due to combustion of hydrogen in the fuel. Heat lost due to dry flue gases = 푚𝑔푐푝𝑔(푇𝑔 − 푇푎)
17 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 6
Aim: Study of Boiler Mountings
Apparatus: water level indicator, pressure gauge, safety valves, fusible plug, blow of cock, feed check valve, stop valve.
Theory: Water level indicator The function of water level indicator is used to indicate the level of water in the boiler constantly. It is also called as water gauge. Normally two water level indicators are fitted at the front end of every boiler. Where the boiler drum is situated at considerable height from the floor, the water gauge is often inclined to make the water level visible from any position. When the water being heated in the boiler transform into steam the level of water in boiler shell goes on reducing.
For the proper working of boiler, the water must be kept at safe level. If the water level falls below the safe level and the boiler goes on producing the steam without the addition of feed water, great damages like crack and leak can occur to the part of boiler which get uncovered from water. This can result in the stoppage of steam generation and boiler operation. For controlling the passage of steam water cock D and E are provided. When these cocks are opened the water stands in the glass tube at the same level as in the boiler. K is the drain cock too blows out water at interval so as not to allow any sediment to accumulate. Upper
18 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola and lower stuffing boxes are connected by a hollow metal column G. Ball J and H rest in the position shown in the normal working of the gauge. When the glass tube breaks due to rush of water in the bottom passage the ball move to dotted position and shuts of the water and steam. Then the cock D and E safely closed and broken glass tube replaced. M, N, P are R are screwed caps for internal cleaning of the passage after dismantling. L is guard glass.
Pressure gauge
The function of pressure gauge is measure the pressure exerted inside the vessel. The gauge usually mounted on the front top of the shell or drum. It is usually constructed to indicate upto double the maximum working pressure. Its dial is graduated to read its pressure in bar The figure shows the bourden pressure gauge a common type of pressure gauge used. The essential feature of this gauge is that elliptical spring tube which is made of a special quality of bronze and is solid drawn.
Dead weight safety valve Fig shows the dead weight safety valve. A is the vertical cast iron pipe through which steam pressure acts. B is the bottom flange directly connected to seating block on the boiler shell communicating to the steam space.
19 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
V is the gun metal valve and VS is the gun metal valve seat. D is another cast iron pipe for discharge of excess steam from the boiler. W are the weight in the form of cylindrical disc of cast iron. WC is the weight carrier carrying the weights W. The cover plate c covers these weights. The steam pressure acts in the upward direction and is balanced by the force of dead weights w. The total dead weight consist of sum of weight W. Weight of valve V , weight of weight carrier and weight of cover plate.
Lever safety valve It consists of lever and weight W. The valve rests on the valve seat which is screwed into the valve body the valve seat can be replaced if required. The valve body is fitted on the boiler shell. One end of the lever is hinged while at the other is suspended a weight w. The strut presses against the valve on seat against the steam pressure below the valve. The slotted level guide allows vertical movement to the lever. When the steam pressure becomes greater than normal working pressure, the valve is lifted with the lever and the weight. Consequently, steam escapes through the passages between the valve and seat and the steam pressure decreases.
Fusible plug The function of fusible plug is to protect the boiler against damages due to overheating for low water level. It is fitted on the fire box crown plate or over the combustion chamber at its appropriate place. A common form of fusible plug is as illustrated in fig. It consists of hollow gun metal body screwed into the fire box crown. The body has hexagonal flange to tighten it into the shell. A gun metal plug having a hexagonal flange is screwed into the gun metal body. There is another hollow gun metal plug separated from the metal plug by an annulus of fusible metal. The fusible metal is protected from fire by flange on the hollow gun metal plug. Under normal condition when the water level in the boiler shell is normal, the fusible plug is fully submerged inside the water. In this case the heat from fusible plug is being conducted to water which keeps the fusible metal at an almost constant temperature and below its melting point.
20 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
But when the water level falls below the fusible plug, it gets uncovered from water and is exposed to steam. The conduction form fusible plug to steam is very less as compared with that of water. Hence fusible plug becomes overheated and it melts with the result that hollow gun metal plug falls down making a hole. The steam and water being under pressure immediately rush to fire box and extinguish the fire. The fusible plug should be generally renewed after a period of about two years as they are liable to become defective over a long period of use because they are subjected to heat on one side and scale deposits on the other side.
Blow of cock
21 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
The blow of cock performs two functions it may discharge a portion of water when the boiler is in operation to blow out mud, scale or sediments periodically. It also empties the boiler when necessary for cleaning, inspection and repair. It is fitted on the boiler shell directly or to a short branch pipe at the lowest part of the water space. When more than one boiler are working and they drain in the same waste pipe line, an isolating valve is necessary to prevent the discharge one of the boiler from entering into the other. The fig shows the common type of plug. The plug p of the cock is conical and fits into the casing c which is packed with asbestos packing in grooves round the top and bottom of the plug. The shank s of the plug passes through gland and stuffing box in the cover. The plug is held down by yoke Y and two studs. A are the vertical slots for fixing the box spanner, on the top of the yoke. The plug spindle S is generally rotated by means of the box spanner. The plug p has hole. When this hole is brought in line with the casing hole by rotating the spindle s, the water flows out of it. And the water cannot flow when the solid portion of the plug is in front of casing hole.
Feed check valve The function of feed check valve is to control the supply of water to the boiler and to prevent the escaping of water from the boiler when the pump pressure is less or pump is stopped. The feed check valve is fitted in the water space of boiler slightly below the normal level of the water.
Stop valve A junction valve is a valve which is placed directly above the boiler and connected to steam pipe which carries steam to the engine. If a valve is placed in the steam pipe leading steam to the engine and placed near the engine, it is usually termed as stop valve. Junction valve and stop valve are essentially the same, the larger sizes are called junction valves and the smaller sizes are called stop valves. The function of the stop valve or junction valve is to regulate the flow of steam from one steam pipe to the other from the boiler to the steam pipe. The common type of valve is as shown in figure. It consists of valve V which is attached to the valve spindle VS.
22 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
The spindle is connected to hand wheel H and passes through a screwed portion like the nut and through a gland or stuffing box G to prevent leakage of steam. On turning the hand wheel H the spindle is raised or lowered depending upon the sense of rotation of wheel. The passage of steam flow on opening is shown by arrows.
23 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 7
Aim: Study and Trial on Steam Turbine.
Theory Steam turbine is a prime mover in which the potential energy of the steam is transformed into kinetic energy and latter in its turn is transformed into the mechanical energy of rotation of the turbine shaft. The turbine shaft directly or with the help of reduction gearing, is connected with the driven mechanism. Depending on the type of the driven mechanism a steam turbine may be utilised in most diverse fields of industry, for power generation and for transport. Transformation of potential energy of steam into the mechanical energy of rotation of the shaft is brought about by different means. Common types of steam turbine are as follows Simple impulse turbine Reaction turbine The main difference between the turbines lies in the way in which the steam is expanded while it moves through them. In the former type the steam expands in the nozzles and its pressure does not alter as it moves over the blades while in the latter type the steam expands continuously as it passes over the blades and thus there is gradual fall in the pressure during expansion. Simple impulse turbine Fig shows the simple impulse turbine diagrammatically. The top portion of the figure
24 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola exhibits a longitudinal section through the upper half of the turbine, the middle portion shows one set of nozzles which is followed by a ring of moving blades, while lower part of the diagram indicates approximately changes in pressure and velocity during the flow of steam through the turbine. The turbine is called simple impulse turbine since the expansion of the steam takes place in one set of nozzle. As the steam flows through the nozzle its pressure falls from steam chest pressure to condenser pressure due to relatively high expansion of steam in the nozzles the steam leaves the nozzles with a very high velocity. It is evident that velocity of steam leaving the moving blades is a large portion of maximum velocity of the steam when leaving the nozzles. The loss of energy due to this higher exit velocity is commonly called carry over loss.
Reaction turbine In reaction turbine there is gradual pressure drop takes place continually over the fixed and moving blade. The function of fixed blades is that they alter the direction of steam as well as allow it expand to a larger velocity. As the steam passes over the moving blades its kinetic energy is absorbed by them. Fig shows the three stage reaction turbine. The changes in pressure and velocity are also shown in fig. As the volume of steam increases at lower pressure therefore the diameter of the turbine must increase after each group of blade ring. In this turbine the pressure drop per stage is small therefore the number of stages required is much higher than an impulse turbine of same capacity.
Methods of reducing wheel or rotor speed. Velocity compounding Pressure compounding
25 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Pressure velocity compounding Reaction turbine
Velocity compounding Steam is expanded through a stationary nozzle from the boiler or inlet pressure to condenser pressure. So the pressure in the nozzle drops, the kinetic energy of the steam increases due to increase in velocity. A portion of this available energy is absorbed by a row of moving blade. The steam then passes through the second row of blades which are fixed. The function of these fixed blade is to redirect the steam without altering its velocity to the following next row moving blade where again work is done on them and steam leaves the turbine with a low velocity.
Pressure compounding Fig shows the rings of nozzle incorporated between the rings of moving blades the steam at boiler pressure enters the first set of nozzle and expands partially. The kinetic energy of steam thus obtained is absorbed by the moving blades. The steam then expand partially in the second sets of nozzle where its pressure again falls and velocity increase the kinetic energy so obtained is absorbed by the second ring of moving blades. This is the most efficient turbine since the speed ratio remains the constant but it is expensive owing to large number of stages.
26 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Pressure velocity compounding This method of compounding is the combination of two previously discussed methods. This total drop in steam pressure is divided into stages and the velocity obtained in each stage is also compounded. The rings of nozzle are fixed at the beginning of each stage and pressure remains constant during each stage
27 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 8
Aim: Study of Condenser
Theory
Steam condenser is a device or appliance in which the steam condensed and heat released by steam is absorbed by water. Classification of condenser Jet condenser Surface condenser Jet condenser In jet condenser, the exhaust steam and water comes in direct contact with each other and temperature of the condensate is same as that of cooling water leaving the condenser. The cooling water is usually sprayed into the exhaust steam to cause rapid condensation. In surface condenser exhaust steam and water do not come into direct contact with each other. The steam passes over the outer surface of tubes through which supply of water is maintained. There may be single pass or double pass. In single pass the water flows in one direction only through all tubes, while in two pass condenser water flows in one direction only through all tube, while in two pass condenser the water flows in one direction through the tubes and return through the remainder. A jet condenser is simpler and cheaper than a surface condenser. It should be installed when the cooling water is cheaply and easily available for boiler feed. A surface condenser is most commonly used because the condensate obtained is not thrown as waste but return to the boiler. Jet condenser Parallel flow Counter flow Fig shows the line sketch of the low level parallel flow condenser. The exhaust steam is entering the condenser from the top and cold water is being sprayed on its way. The baffle plate is provided in it to ensure the proper mixing of steam and cooling water. An extraction pump at the bottom discharges the condensate to the hot well from where it may be fed to the boiler if the cooling water being used is free from impurities. A separate dry pump may be incorporated to maintained proper vacuum.
28 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Low level jet condenser (counter flow) Fig shows the L,M and N are perforated trays which break up water into jets.
The steam moving upward comes in contact with water and gets condensed. The condensate and water mixture is sent to the hot well by means of extraction pump and the air is removed by an air suction pump provided at the top of the condenser.
High level jet condenser Fig shows high level counter flow jet condenser. It is also called barometric condenser. In this case the shell is placed at about 10 meter above the hot well and thus the necessity of providing an extraction pump can be obviated. However provision of own injection pump has to be made if water under pressure is not available.
29 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
It is of two types, depending upon the way in which the cooling water cools the exhaust steam. 1. Jet condenser:- In this type of condenser, the cooling water and exhaust steam come into direct contact and the temperature of condensate is the same as that of cooling water leaving the condenser. It is the three of types:- (a) Parallel flow type:- In which both exhaust steam and cooling water outer at the top of condenser and then flow in downward direction. The condensate and water are collected from the bottom. (b) Counter flow type:- Exhaust steam and cooling water outer from the opposite direction. Usually the exhaust steam at the bottom and rises up while the cooling water enters at the top and flow downward. (c) Ejector type: - The mixing of exhaust steam and cooling water takes place in a series of combining cones and K. E. of steam is utilized to assist in draining the water from the condenser into net well against the pressure of atmospheric. Parallel flow and contra flow condenser are further sub divided in two categories:- (i) Low level type:- According to the position of condensing chamber, in case of low level type the overall height of the unit is low enough type. So that the condenser may be directly placed be near the steam turbine or engine. In this type of condenser, an extraction pump is required for drawing out the condensate, cooling water and air. (ii) High level type: - High level condenser is similar to low level jet condenser except that it uses a barometric type or trail pipe for cooling the vacuum & removing the condensate & in some cases the non condensable gases. 2. Surface condenser:- The exhaust steam and the cooling water don’t come into direct contact. The steam to be condensed is made to flow over the outside of a nest of type through which the cooling water circulates. It is following types:- (a) Down flow type:- The steam enters at the top and flows down over the tube through which water is circulated. As the condensed steam floe perpendicular to the direction of flow of cooling water inside the tubes, this condenser is also called cross- surface condenser. (b) Central flow type:- In the centre of the tube nest is located the suction of air extracting pump thus resulting in the flow of steam rapidly inwards. There is better contact between
30 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola the outer surfaces of tubes and the steam due to the volute casting round the nest of the tubes. (c) Inverted type:- The steam after entering at the bottom rises up and then again flows down following a path near the outer surface of the condenser. The condensate extraction pump is providing at the bottom while the suction pipe of the air extraction pump connected to the top. (d) Evaporative condenser:- When the supply of cooling water is limited, its quantity required to condensate the steam may be greatly reduced by covering the circulating water to evaporative under small particle pressure due to heat capacity of gilled pipe it has the periods without seriously affecting the vacuum. Condenser efficiency: - Condenser efficiency is defined as the ratio of the difference between the outlet and inlet temperature of cooling water to the difference between the temperature corresponding the vacuum in the condenser and the inlet temperature of cooling water. Condenser efficiency = Rise in temperature of cooling water (temp. correspondence to vacuum) - (inlet temp. of cooling water in condenser)
31 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Practical No 9
Aim: Study of Steam Power Plant
Appraturs: layout of steam power plant
Theory A steam power plant continuously convert the energy stored in fossil fuels coal, oil natural gas or fuels like uranium thorium into the shaft work and ultimately into electricity. The working fluid is water which is sometimes in the liquid phase and some times in the vapour phase during its cycle of operation.
The energy released by burning of fuel is transferred to water in the boiler to generate steam at high pressure and temperature, which then expands in the turbine to low pressure to produce shaft work.
32 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
The steam leaving the turbine is condensed into water in the condenser where the cooling water from a river or sea circulates carrying away the heat released during condensation. The water condensate is then fed back to the boiler by the pump, and the cycle goes on repeating itself. Since the fluid is undergoing a cyclic process there will be no net change in internal energy over the cycle. And consequently the net energy transferred to the unit mass of fluid as heat during the cycle must equal the net energy transfer as work from the fluid.
Steam power plant having bulk energy converter from fuel to electricity The efficiency of the cycle thus obtained as 푊푛푒푡 휂 = 푄1 푊푇 − 푊푃 = 푄1 푄1 − 푄2 = 푄1 푄푒푐표푛표푚𝑖푠푒푟 = ℎ5 − ℎ4 푄푒푣푎푝표푟푎푡표푟 = ℎ6 − ℎ5 푄푠푢푝푒푟ℎ푒푎푡푒푟 = ℎ1 − ℎ6
The heat transfer to water in steam generator takes place in three different regimes.
33 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
Water is first heated sensibly in the economiser in the liquid phase at a certain pressure from state 4 to state 5 till it becomes saturated liquid. In the evaporator the boiler proper, there is phase change or boiling with the state changing from 5 to 6 by absorbing the latent heat of vaporization at that pressure. The saturated vapour at state 6 is further heated at constant pressure in the superheater to state 1 in the vapour or gaseous phase. For unit mass of fluid heat transfer in these three types of heat exchanger is given by
Fraction of heat transfer in economiser, air preheater, and superheater.
Result: Thus steam power plant is studied.
34 ENERGY CONVERSION-1 LAB College of Engineering & Technology Akola
QUESTIONS FOR VIVA Questions for viva- voce:- 1. Explain the construction & working of various mountings of boiler? 2. Explain the construction & function of accessories of a boiler? 3. State the location and function of safety valve in a boiler? 4. State any four salient features of low pressure boiler? 5. Give the advantage of low pressure boiler? Questions for viva-voce:- 1. Draw a neat sketch of any one fire tube boiler? 2. State any four salient features of a high pressure boiler? 3. Classify the boiler? 4. Draw a neat sketch of any one water tube boiler? 5. Give the advantage of high pressure boiler? Question for viva- voce:- 1. Define heat balance sheet? 2. Define the method of minimizing the heat loss in boiler? Questions for viva- voce:- 1. State principle of working of Reaction steam turbine? 2. Define the term stage efficiency of a turbine? 3. Define the term vacuum efficiency of a turbine? 4. What is prime mover? 5. What is compounding? Questions for viva- voce:- 1. What do you mean by steam condenser? 2. What is its function? 3. Differentiate between surface and jet condenser? 4. Define the term “condenser efficiency”? 5. What are the advantages of installing a condenser in thermal power plant? 6. State the various type of steam condenser?
To prepare heat balance sheet for given boiler data. Pressure of steam = 10 bar Steam condenser = 540 kg/h Fuel used = 65 kg/h Moisture in fuel = 2% by mass Mass of dry flue gases = 9 kg/kg of fuel Lower calorific value of fuel = 32,000 kJ/kg Temperature of the flue gases = 325° C Temperature of boiler house = 28° C Feed water temperature = 50° C Mean specific heat of flue gases = 1 kJ/kg K Dryness fraction of steam = 0.95
35 ENERGY CONVERSION-1 LAB