TE Lab Manual 2011

THERMAL ENGINEERING LAB MANUAL

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CONTENTS SL No

TITLE

PAGE NO

Introduction

Preparation for laboratory session

Laboratory policies 1.

2.

3. 4.

5.

6.

7.

8.

9.

10.

11.

Study of IC Engines

.

Valve Timing Diagram of a Single Cylinder Four Stroke C I Engine Port Timing Diagram of a Single Cylinder Two Stroke C I Engine

Performance Test on 4-stroke Diesel Engine.

Morse Test on Multi cylinder Petrol Engine.

Retardation Test to find Frictional Power of a Diesel Engine

Study of Steam Boilers and Turbines.

Determination of Viscosity using Red Wood Viscometer.

Determination of Flash Point and Fire Point.

Performance test on Reciprocating Air Compressor Performance test on Centrifugal Blower

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THERMAL ENGINEERING LAB MANUAL

INTRODUCTION

OBJECTIVES The objectives of the 080120029 THERMAL ENGINEERING LABORATORY course are: 1. To teach you how to do the experimental work expected from modern engineering professionals. 2. To demonstrate to you physical concepts that you are learning in thermal engineering course. The experiments are not necessarily limited to material you have learned in class. Some of the experiments are designed to make you think and introduce new concepts and ideas that are beyond traditional classroom instruction. 3. To stimulate your curiosity and imagination. Hopefully, the course will give you a sense of measuring and discovering nature, and will introduce you to the excitement of research. 4. To give you experience with modern instrumentation, real time data processing and graphical display of results. 5. To train you in team work. 6. To enhance your communication and writing skills. Great emphasis is put on the quality and appearance of the laboratory reports.

COURSE STRUCTURE 080120029 Thermal Engineering Laboratory course consists of 8-10 laboratory sessions. You will work in groups, typically of 7, and prepare reports for laboratory experiments.

TIME AND PLACE The lab period for each group will be set during the thermal engineering theory class. The laboratory is located on the same floor as the Lathe machine shop. The lab for each experiment will be noted on the master schedule. You will be able to perform the experiments only during the scheduled times. However, students will have additional access to the laboratory to use the hardwares

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and prepare for their next experiment. This access is only during normal work hours - Monday through Friday, 8:30 a.m. to 4:00 p.m.

BOOKS AND MANUALS The primary text for this course is this manual. The material specific to each experiment is also kept near the experimental set-up; consult with the Lab assistants if you need it.

LABORATORY REPORTS You will submit a report for each experiment that you perform. All reports will be graded on the technical content as well as the writing and presentation. The deadline for submitting rough and final drafts are decided by lab in charge. These deadlines are not changeable. Technical report submission will be an important factor in your future career. It is an avenue for communicating your ideas to your superiors and colleagues. The opinion that your superiors form of you will depend heavily on the quality of such reports. You should make a considerable effort to master the technique of report writing. The laboratory exercise grade will be based on: 1. The quality of preparation for the laboratory session. This may include a short verbal or written quiz before or during each experiment. 2. Attendance and performance in the laboratory. 3. Quality of the report: This will be based on the technical content as well as the quality of presentation and technical writing. Late assignments will result in lower grades.

PREPARATION FOR THE LABORATORY SESSION Before coming to the laboratory: 1. Read carefully and understand the description of the experiment in the lab manual. You may go to the lab at an earlier date to look at the experimental facility and understand it better. Consult the appropriate references to be completely familiar with the concepts and hardware. At the beginning of the class, if the instructor or the lab assistant finds that a student is not adequately prepared; they will be graded zero for that experiment and not be allowed to take it.

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2. Rough record must be prepared and brought to the lab. You will not be allowed to write the record during the laboratory period. 3. Bring necessary material needed to perform the required preliminary analysis. It is a good idea to do sample calculations and as much of the analysis as possible during the session. Lab assistant’s help will be available. Errors in the procedure may thus be easily detected and rectified. 4. Check with one of the lab assistants one week before the experiment to make sure that you have the handout for that experiment and all the apparatus. After the laboratory session 1. Clean up your work area. 2. Check with the lab assistants or technician before you leave. 3. Make sure you understand what kind of report is to be prepared and when it is due. 4. Do sample calculations and some preliminary work to verify that the experiment was successful. Make-ups and Late work Students must participate in all laboratory exercises as scheduled. They must obtain permission from the instructor for absence, which would be granted only under justifiable circumstances. In such an event, a student must make arrangements for a make-up laboratory, which will be scheduled when laboratory time is available.

LABORATORY POLICIES 1. Food items are not allowed in the laboratory at any time. 2. Do not sit or place anything on instrument benches. 3. The teaching assistants and staff are concerned about your safety and for the equipment in the laboratory. Follow their instructions. If you have any doubt about the way to operate some equipment, do not guess. Read the instructions carefully and if still in doubt, ask the staff for assistance. 4. Organizing laboratory experiments requires the help of laboratory technicians and staff. Be punctual. If you come late to the laboratory, you may be asked to leave. Remember that some of the sessions include short tests before the experiment and no make-ups will be given.

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AN OVERVIEW OF RECIPROCATING ENGINES Despite its simplicity, the reciprocating engine (basically a piston-cylinder device) is one of the rare inventions that has proved to be very versatile and to have a wide range of applications. It is the powerhouse of the vast majority of automobiles, trucks, light aircraft, ships, and electric power generators, as well as many other devices. The basic components of a reciprocating engine are shown in Fig. The piston reciprocates in the cylinder between two fixed positions called the top dead center (TDC)the position of the piston when it forms the smallest volume in the cylinder and the bottom dead center (BDC)the position of the piston when it forms the largest volume in the cylinder. The distance between the TDC and the BDC is the largest distance that the piston can travel in one direction, and it is called the stroke of the engine.

The diameter of the piston is called the bore. The air or air—fuel mixture is drawn into the cylinder through the intake valve, and the combustion products are expelled from the cylinder through the exhaust valve. The minimum volume formed in the cylinder when the piston is at TDC is called the clearance volume. The volume displaced by the piston as it moves between TDC and BDC is called the displacement volume. The ratio of the maximum volume formed in the cylinder to the minimum (clearance) volume is called the compression ratio r of the engine. Another term frequently used in conjunction with reciprocating engines is the mean effective pressure (MEP). It is a fictitious pressure that, if it acted on the piston during the entire power stroke, would produce the same amount of net work as that produced during the actual cycle.

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Reciprocating engines are classified as spark-ignition (SI) engines or compression-ignition (CI) engines, depending on how the combustion process in the cylinder is initiated. In SI engines, the combustion of the air—fuel mixture is initiated by a spark plug. In CI engines, the air—fuel mixture is self-ignited as a result of compressing the mixture above its self-ignition temperature. In the next two sections, we discuss the Otto and Diesel cycles, which are the ideal cycles for the SI and CI reciprocating engines, respectively.

Displacement Volume

Clearance Volume

OTTO CYCLE: THE IDEAL CYCLE FOR SPARK-IGNITION ENGINES In most spark-ignition engines, the piston executes four complete strokes (two mechanical cycles) within the cylinder, and the crankshaft completes two revolutions for each thermodynamic cycle. These engines are called four-stroke internal combustion engines. Initially, both the intake and the exhaust valves are closed, and the piston is at its lowest position (BDC). During the compression stroke, the piston moves upward, compressing the air—fuel mixture. Shortly before the piston reaches its highest position (TDC), the spark plug fires and the mixture ignites, increasing the pressure and temperature of the system. The high-pressure gases force the piston down, which in turn forces the crankshaft to rotate, producing a useful work output during the expansion or power stroke. At the end of this stroke, the piston is at its lowest position (the completion of the first mechanical cycle), and the cylinder is filled with combustion products. Now

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the piston moves upward one more time, purging the exhaust gases through the exhaust valve (the exhaust stroke), and down a second time, drawing in fresh air—fuel mixture through the intake valve (the intake stroke). Notice that the pressure in the cylinder is slightly above the atmospheric value during the exhaust stroke and slightly below during the intake stroke.

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In two-stroke engines, all four functions described above are executed in just two strokes: the power stroke and the compression stroke. In these engines, the crankcase is sealed, and the outward motion of the piston is used to slightly pressurize the air—fuel mixture in the crankcase, as shown in Fig. Also, the intake and exhaust valves are replaced by openings in the lower portion of the cylinder wall. During the latter part of the power stroke, the piston uncovers first the exhaust port, allowing the exhaust gases to be partially expelled, and then the intake port, allowing the fresh air—fuel mixture to rush in and drive most of the remaining exhaust gases out of the cylinder. This mixture is then compressed as the piston moves upward during the compression stroke and is subsequently ignited by a spark plug.

DIESEL CYCLE: THE IDEAL CYCLE FOR COMPRESSION-IGNITION ENGINES

The Diesel cycle is the ideal cycle for CI reciprocating engines. The CI engine, first proposed by Rudolph Diesel in the 1890s, is very similar to the SI engine discussed in the last section, differing mainly in the method of initiating combustion. In spark-ignition engines (also known as gasoline engines), the air—fuel mixture is compressed to a temperature that is below the autoignition temperature of the fuel, and the combustion process is initiated by firing a spark plug. In CI engines (also known as diesel engines), the air is compressed to a temperature that is above the autoignition temperature of the fuel, and combustion starts on contact as the fuel is injected into this hot air. Therefore, the spark plug and carburetor are replaced by a fuel injector in diesel engines.

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The two-stroke engines are generally less efficient than their four-stroke counterparts because of the incomplete expulsion of the exhaust gases and the partial expulsion of the fresh air—fuel mixture with the exhaust gases. However, they are relatively simple and inexpensive, and they have high power-to-weight and power-to-volume ratios, which make them suitable for applications requiring small size and weight such as for motorcycles, chain saws, and lawn mowers. Advances in several technologies such as direct fuel injection, stratified charge combustion, and electronic controls brought about a renewed interest in two-stroke engines that can offer high performance and fuel economy while satisfying the stringent emission requirements. For a given weight and displacement, a well-designed two-stroke engine can provide significantly more power than its four-stroke counterpart because two-stroke engines produce power on every engine revolution instead of every other one.

In the new two-stroke engines, the highly atomized fuel spray that is injected into the combustion chamber toward the end of the compression stroke burns much more completely. The fuel is sprayed after the exhaust valve is closed, which prevents unburned fuel from being ejected into the atmosphere. With stratified combustion, the flame that is initiated by igniting a small amount of the rich fuel—air mixture near the spark plug propagates through the combustion chamber filled with a much leaner mixture, and this results in much cleaner combustion. Also, the advances in electronics have made it possible to ensure the optimum operation under varying engine load and speed conditions.

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REVIEW QUESTIONS

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

What do the terms TDC and BDC stand for? What is clearance volume? What is piston stroke? What is piston displacement in an engine? What is compression ratio? What is mean effective pressure? Define IP and BP and their units. What do you understand by the term ―Engine Torque‖? How is it measured? Differentiate between power and torque. What is the difference between SI and CI engine? What is the difference between IC and EC engines? How is fuel ignited in diesel engine? What compression ratios are usually used in CI engines? What is the approximate cranking compression pressure in an automotive diesel engine? What is ignition temperature of diesel fuel? What determines the power developed in a given diesel engine? What limits the amount of fuel injected in a diesel engine? State the approximate maximum air fuel ratio employed in diesel engine? State the reasons for higher volumetric efficiency of diesel engines compared to petrol engines? Which is more efficient out of petrol or diesel engine? Out of petrol and diesel engines, which has usually more reliable fuel supply system? Why a diesel engine is also called CI engine? What is approximately the consumption of fuel in a diesel engine as compared to that in an equivalent petrol engine? Out of petrol and diesel engines, which involves less risk of catching fire? Why? Which is more costly: petrol or diesel engine? What is the function of flywheel in an engine? What is dual cycle? Where is it used? What is square engine? What is radial engine? How will any change in stroke length affect the power output?

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PORT TIMING DIAGRAM OF A SINGLE CYLINDER FOUR STROKE COMPRESSION IGNITION ENGINE

Exp No : Date

:

AIM:

To determine the opening and closing of the inlet and exhaust ports in a two stroke SI engine and draw the port timing diagram.

APPARATUS / EQUIPMENTS / INSTRUMENTS REQUIRED: 1. Four stroke diesel engine test Rig 2. Chalk 3. Measuring tape 4. String ENGINE SPECIFICATIONS:

BRIEF THEORY OF THE EXPERIMENT:

The port timing diagram gives an idea about how various operations are taking place in an engine cycle.

The two stroke engines have inlet and transfer ports

to transfer the combustible air fuel mixture and an exhaust port to transfer exhaust gas after

combustion. The sequence of events such as opening and closing of ports are controlled by the movements of piston as it moves from TDC to BDC and vice versa. As the cycle of operation is completed in two strokes, one power stroke is obtained for every crankshaft

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revolution. Two operations are performed for each stroke both above the piston (in the cylinder) and below the piston (crank case). When compression is going on top side of the piston, the charge enters to the crank case through inlet port. During the downward motion, power stroke takes place in the cylinder and at the same time, charge in the crank case is compressed and taken to the cylinder through the transfer port. During this period exhaust port is also opened and the fresh charge drives away the exhaust which is known scavenging. As the timing plays major role in exhaust and transfer of the charge, it is important to study the events in detail. The pictorial representation of the timing enables us to know the duration and instants of opening and closing of all the ports. Since one cycle is completed in one revolution i.e. 360 degrees of crank revolution, various positions are shown in a single circle of suitable diameter.

PROCEDURE 1. Mark the direction of rotation of the flywheel. Always rotate only in clockwise direction when viewing in front of the flywheel. 2. Mark the Bottom Dead Center (BDC) position on the flywheel with the reference point when the piston reaches the lowermost position during rotation of the flywheel. 3. Mark the Top Dead Center (TDC) position on the flywheel with the reference point when the piston reaches the top most position during the rotation of flywheel. 4. Mark the IPO, IPC, EPO, EPC, TPO, and TPC on the flywheel observing the following conditions. 5. Inlet port open (IPO) when the bottom edge of the piston skirt just opens the lower most part of the inlet port during its upward movement. 6. Inlet port close (IPC) when the bottom edge of the piston fully reaches the lower most part of the inlet port during its downward movement. 7. Transfer port open (TPO) when the top edge of the piston just open the top most part of the transfer port during its downward movement. 8. Transfer port close (TPC) when the top edge of the piston fully reaches the upper most part of the transfer port during its upward movement 9. Exhaust port open (EPO) when the top edge of the piston just opens the top most part of the exhaust port during its downward movement. 10. Exhaust port close (EPC) when the top edge of the piston fully reaches the upper most part of the exhaust port during its upward movement 11. Measure the circumferential distance of the above events either from TDC or from BDC whichever is nearer and calculate their respective angles. 12. Draw a circle and mark the angles.

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RESULT AND DISCUSSIONS: The given two-stroke petrol engine is studied and the Port timing diagram is drawn for the present set of values.

REVIEW QUESTIONS: 1. What is the difference between valves and ports? 2. How does the opening and closing of ports happen in two stroke engines? 3. What is the use of transfer port? 4. What do you mean by scavenging? 5. What are the problems associated with two stroke engines? 6. What are the advantages of two stroke engines? 7. How are two stroke engines lubricated? Give the name. 8. Define compression ratio. Give the range of compression ratio for petrol and diesel engines. 9. What are the functions of inlet and exhaust manifolds? 10. Where is inlet manifold mounted on engine?

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THERMAL ENGINEERING LAB MANUAL OBSERVATION TABLE: Circumference of flywheel (L) =

mm

Before TDC EVENT

mm

deg

After TDC mm

deg

Before BDC mm

deg

After BDC mm

deg

IPO IPC EPO EPC TPO TPC

FORMULA:

Where, L - Distance from nearest dead center in mm X- Circumference of the Flywheel in mm

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VALVE TIMING DIAGRAM OF A SINGLE CYLINDER FOUR STROKE COMPRESSION IGNITION ENGINE Exp No : Date

:

AIM:

To determine the opening and closing of the inlet and exhaust valves in a four stroke diesel engine and draw the valve timing diagram.

APPARATUS / EQUIPMENTS / INSTRUMENTS REQUIRED: 5. Four stroke diesel engine test Rig 6. Chalk 7. Measuring tape 8. String ENGINE SPECIFICATIONS:

BRIEF THEORY OF THE EXPERIMENT:

The valve timing diagram gives an idea about how various operations are taking place in an engine cycle. The four stroke diesel engines have inlet valve to supply air inside the cylinder during suction stroke and an exhaust valve to transfer exhaust gas after combustion to the atmosphere. The fuel is injected directly inside the cylinder with the help of a fuel injector. The sequence of events such as opening and closing of valves which are performed by camfollower-rocker arm mechanism in relation to the movements of the piston as it moves from

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TDC to BDC and vice versa. As the cycle of operation is completed in four strokes, one power stroke is obtained for every two revolution of the crankshaft.

The suction, compression, power and exhaust processes are expected to complete in the respective individual strokes. Valves do not open or close exactly at the two dead centers in order to transfer the intake charge and the exhaust gas effectively. The timing is set in such a way that the inlet valve opens before TDC and closes after BDC and the exhaust valve opens before BDC and closes after TDC. Since one cycle is completed in two revolutions i.e 720 degrees of crank rotations, various events are shown by drawing spirals of suitable diameters. As the timing plays major role in transfer of the charge, which reflects on the engine performance, it is important to study these events in detail.

PROCEDURE: 1. The inlet and exhaust valves are identified. 2. The direction of rotation of the fly wheel has to be ascertained by observing the correct sequence of opening and closing of valves. 3. The fixed reference point is selected near the fly wheel periphery. 4. The circumference of flywheel is measured using a string and tape. 5. The piston is moved to the top position by rotating the flywheel in the correct direction (clockwise) and a marking is made on the fly wheel against a reference point. This is the top dead center (TDC). 6. Another mark is made on the flywheel at 1800 from the TDC and this is the bottom dead center (BDC) 7. The fly wheel is rotated slowly in the same direction and the opening and closing of the inlet valve are marked on the fly wheel as IVO and IVC. 8. The timing at spark occurrence is also measured by looking into the opening of Cylinder block. 9. Similarly the opening and closing of the exhaust valve are also marked on the flywheel as EVO and EVC. 10. Circumferential distances between the various markings are measured with respect to the nearest dead center and the lengths are converted into suitable angle (θ) and tabulated. 11. The valve timing diagram is drawn. 12. The duration in degrees for which both the valves remain open is noted as the angle of valves overlap.

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RESULT AND DISCUSSION

The given four stroke compression ignition engine is studied and the valve timing diagram is drawn for the present set of values.

REVIEW QUESTIONS:

1. How the valves are different from ports? 2. What are the advantages of four stroke engines over two stroke engines? 3. Why four stroke engines are more fuel efficient than two stroke engines? 4. Explain the lubrication system of four stroke engines. 5. What do you mean by valve overlap? What are their effects in SI engines? 6. How the cylinder numbers assigned in multi-cylinder I.C. engines? 7. Give firing order for a four and six cylinder engines. 8. Explain how the correct direction of rotation is found before starting the valve timing experiment. 9. How do you identify an engine is working on two stroke or four stroke principle? 10. How do you identify whether it is petrol or diesel engine?

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FORMULA:

Where, L - Distance from nearest dead center in mm X- Circumference of the Flywheel in mm

OBSERVATIONS: Before TDC

After TDC

Before TDC

After TDC

EVENT mm

deg

mm

deg

mm

deg

mm

deg

IVO IVC FIB FIC EVO EVC

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PERFORMANCE TEST ON SINGLE CYLINDER FOUR STROKE DIESEL ENGINE Exp No : Date

:

AIM To perform a load test on the given engine and to draw the performance characteristic curves.

APPARATUS REQUIRED 1. The engine test rig 2. Stop-watch 3. Hand tachometer

SPECIFICATIONS Make

:

Kirloskar

BHP

:

5.0

Speed

:

1500 rpm

No. of Cylinders

:

1

Bore

:

80 mm

Stroke

:

110 mm

Method of loading

:

rope brake dynamometer

Method of starting

:

hand start

Method of cooling

:

Water cooled

BRIEF THEORY OF THE EXPERIMENT

A load test on an engine provides information regarding the performance characteristics of the engine. Engine performance varies with both load on the engine as well as the engine speed. However the stationary engine used in this experiment operate at a constant speed. The performance characteristics of such engines are obtained by varying the load on the engine.

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EXPERIMENTAL SETUP

The compact and simple engine test rig consisting of a four stroke single cylinder, water cooled, constant speed diesel engine coupled to an alternator by flexible coupling. The engine is started by hand cranking using the handle by employing the decompression lever. The engine is loaded using electrical lighting load bank. The loading arrangement consists of a set of lamps and switches on the panel board. A voltmeter and an ammeter are used to record the load on the alternator. A burette is connected with the fuel tank through a control valve for fuel flow measurement. Provision is made to circulate water continuously through the engine jacket.

PRECAUTIONS 1. The engine should be checked for no load condition. 2. The cooling water inlet for engine should be opened. 3. The level of fuel in the fuel tank should be checked. 4. The lubrication oil level is to be checked before starting the engine.

STARTING THE ENGINE 1. Keep the decompression lever in the vertical position 2. Insert the starting handle in the shaft and rotate it 3. When the flywheel picks up speed bring the decompression lever into horizontal position and remove the handle immediately. 4. Now the engine will pick up.

STOPPING THE ENGINE Cut off the fuel supply by keeping the fuel governor lever in the other extreme position.

PROCEDURE 1. Start the engine at no load and allow idling for some time till the engine warm up. 2. Note down the time taken for 10cc of fuel consumption using stopwatch and fuel measuring burette. 3. After taking the readings open the fuel line to fill burette and supply fuel to run the engine from the fuel tank again. 4. Now load the engine gradually to the desired valve. This may be done by switching on three lamps in the columns. 5. Allow the engine to run at this load for some time in order to reach steady state

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condition and note down the time taken for 10 cc of fuel consumption. 6. Note down the voltmeter and ammeter readings for the above conditions. 7. Repeat the experiment by switch ON additional lamps. 8. Ensure that the lamp loads are distributed equally among all the 3 phases. 9. Release the load by switch OFF the lamps slowly one by one and stop the engine. 10. Tabulate the readings as shown and calculate the result.

GRAPHS: 1. B.P. Vs T.F.C. 2. B.P. Vs S.F.C. 3. B.P. Vs Mechanical efficiency 4. B.P. Vs Brake Thermal efficiency

RESULT: Load test on the given engine is performed and performance characteristic curves are drawn. From the graph drawn between B.P and T.F.C, friction power is calculated by Willian’s line method.

REVIEW QUESTIONS

1. How to start and stop the CI engine? 2. What is the purpose of a decompression lever? 3. How the speed of the engine is maintained constant at all loads? 4. What is the function of a governor in a constant speed engine? Where it is normally located? 5. What is normal fuel injection pressure in a C I. engine? 6. What is the speed ratio between a cam shaft and a crank shaft? 7. What is the type of dynamometer employed? 8. Give reasons for valve timing greater than 180º? 9. What is the type of cooling employed in your engine? 10. How do you ensure the lubrication pump is effective?

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THERMAL ENGINEERING LAB MANUAL DETERMINATION OF MAXIMUM LOAD:

√ CALCULATIONS: (

1.

)

Where, X – Quantity of fuel consumed in cc (Burette reading) Specific gravity of fuel X = 2.

gm/cc (

) (

)

√

A 3. Specific fuel consumption (S.F.C)

4. Frictional Power (F.P.) From the graph drawn between brake power and total fuel consumption, the frictional power is found by extrapolation method. Frictional Power (F.P.) 5. Indicated power (I.P.)

= =

kW

Brake power + Frictional power =

6.

KW

⁄

7. Brake thermal efficiency

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Sl. No.

No. of Lamps

% of Load

Voltmeter Reading

Ammeter Reading

(%)

(Volts)

(Amps)

Time for ‘x’ cc of fuel consumption (sec) Trial T1

Trial T2

% of Load

B.P.

T.F.C.

S.F.C

F.P.

I.P

Mech. Efficiency

(%)

(kW)

(kg/hr)

(kg/kw.hr)

(kW)

(kW)

(%)

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Trial Tavg

Brake Thermal Efficiency (%)

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HEAT BALANCE TEST ON SINGLE CYLINDER FOUR STROKE COMPRESSION IGNITION ENGINE Exp No : Date

:

AIM: To perform a heat balance test on the given single cylinder four stroke C.I engine and to prepare the heat balance sheet at various loads.

APPARATUS REQUIRED: 1. C.I. Engine coupled to a three-phase alternator with lamp load. 2. Air tank with air flow meter 3. Burette for fuel flow measurement 4. Rotameter for water flow measurement 5. Stop watch. 6. Ammeter 7. Voltmeter 8. Thermometers. SPECIFICATIONS: Make

:

Kirloskar

BHP

:

5.0

Speed

:

1500 rpm

No. of Cylinders

:

1

Bore

:

80 mm

Stroke

:

110 mm

Method of loading

:

rope brake dynamometer

Method of starting

:

hand start

Method of cooling

:

Water cooled

BRIEF THEORY OF THE EXPERIMENT

From the law of conservation of energy, the total energy entering the engine in various ways in a given time must be equal to the energy leaving the engine during the same time, neglecting other form energy such as the enthalpy of air and fuel. The energy input to the

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engine is essentially the heat released in the engine cylinder by the combustion of the fuel. The heat input is partly converted into useful work output, partly carried away by exhaust gases, partly carried away by cooling water circulated and the direct radiation to the surroundings. In a heat balance test all these values are calculated and converted to percentage with respect to the input and are presented in a chart at various loads.

EXPERIMENTAL SETUP:

The compact and simple engine test rig consisting of a four stroke single cylinder, water cooled, constant speed diesel engine coupled to a three phase alternator by a flexible coupling. The engine

is started by hand cranking using

the handle by employing

the

decompression lever. The engine is loaded using electrical lighting load bank. The loading arrangement consists of a set of lamps and switches on the panel board. A voltmeter and an ammeter are used to record the load on the alternator.

Air from atmosphere enters the inlet manifold through the air box. An orifice meter connected with an inclined manometer is used for air flow measurement. A digital temperature indicator is used to measure temperature of exhaust gas. A burette is connected with the fuel tank through a control valve for fuel flow measurement. Provision is made to circulate water continuously through the engine jacket. Rotameter is provided to measure the flow rate of cooling water. Thermometers are provided to measure the temperature of cooling water passing through the jacket.

PRECAUTIONS: 1. The engine should be checked for no load condition. 2. The cooling water inlet for engine should be opened. 3. The level of fuel in the fuel tank should be checked. 4. The lubrication oil level is to be checked before starting the engine.

STARTING THE ENGINE: 1. Keep the decompression lever in the vertical position 2. Insert the starting handle in the shaft and rotate it 3. When the flywheel picks up speed bring the decompression lever into horizontal position and remove the handle immediately.

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THERMAL ENGINEERING LAB MANUAL 4. Now the engine will pick up. STOPPING THE ENGINE: Cut off the fuel supply by keeping the fuel governor lever in the other extreme position. (For Diesel Engine) PROCEDURE: 11. Start the engine at no load and allow idling for some time till the engine warm up. 12. Note down the time taken for 10cc of fuel consumption using stopwatch and fuel measuring burette. 13. After taking the readings open the fuel line to fill burette and supply fuel to run the engine from the fuel tank again.

14. Now load the engine gradually to the desired valve. This may be done by switching on three lamps in the columns. 15. Allow the engine to run at this load for some time in order to reach steady state condition and note down the time taken for 10 cc of fuel consumption. 16. Note down the voltmeter and ammeter readings for the above conditions. 17. Repeat the experiment by switch ON additional lamps. 18. Ensure that the lamp loads are distributed equally among all the 3 phases. 19. Release the load by switch OFF the lamps slowly one by one and stop the engine. 20. Tabulate the readings as shown and calculate the result.

GRAPH: A graph is drawn by taking load in kW (No. of lamps) along X-axis and cumulative efficiency in Y-axis for various heat loss.

RESULT: The heat balance test is conducted in the given diesel engine to draw up the heat balance sheet at various loads and the graph is drawn.

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REVIEW QUESTIONS:

1. What is the significance of heat balance sheet? 2. How does useful work differ from actual work? For what kind of systems are these two identical? 3. What are unaccounted losses? 4. Name four physical quantities that are conserved and two quantities that are not conserved during a process 5. Express mathematically energy balance of control volume. 6. What is the second-law efficiency? How does it differ from the first-law efficiency? 7. Can a system have a higher second-law efficiency than the first-law efficiency during a process? Give examples. 8. What are the different mechanisms for transferring energy to or from a control volume? 9. What is flow energy? Do fluids at rest possess any flow energy? 10. What are different efficiencies associated with IC engines?

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CALCULATIONS (

1.

)

Where, X – Quantity of fuel consumed in cc (Burette reading) Specific gravity of fuel X = (

2.

gm/cc

) (

)

√

A

3. Heat Input (HI)

4. % of Heat used for useful work output

5. Brake thermal efficiency

6. Heat lost through cooling water = Mw × Cpw × (T2 -T1) kW

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(

)

(

)

7. Heat lost through exhaust gases = Mg × Cpg × (Tg - Ta) (Air consumption method) Where, Mg = ma + mf Mass flow rate of air ma = Manometer (H) × 0.8826 × 10-3 × ρair (kg/s) (Note: Manometer position: mid-inclined)

Where, Patm – atmospheric pressure (N/m2 ) R

– gas constant, 287 J/kg.K

Tatm – atmospheric temperature Notations used: Tg - Exhaust gas temperature Ta - Room Temperature Cpg - Specific heat for exhaust gas = 1.005 kJ/kg.K ρw - Density of water = 1000 kg/m3 ρa - Density of air at room temperature = 1.293 kg/m3

(

)

( = Heat input –

8. Unaccounted heat losses

(

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)

(

) (

)

(

)

(

)

)

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HEAT BALANCE SHEET:

HEAT OUTPUT LOAD

HEAT INPUT

(kW) (kW)

%

Department of Mechanical Engineering

Cumulative Efficiency

CAUSES

(kW)

%

(%)

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MORSE TEST ON MULTI CYLINDER PETROL ENGINE

Exp No Date

: :

AIM: To perform the Morse test on the given multi cylinder petrol engine and to determine the efficiency at the given load. APPARATUS REQUIRED: 1. Multi Cylinder Petrol Engine Test Rig 2. Tachometer 3. Stop watch PROCEDURE: 1. Before starting the engine keep the fuel cut off level in ON position. 2. Start the engine using starter motor. 3. Allow the engine to run at no load for about 10 minutes to warm up and attain steady state condition. 4. Load the engine to the required level. 5. When the engine is loaded to the required load adjust the throttle to maintain the speed of the engine at its rated rpm. 6. Allow few minutes for the engine attains steady state condition and note down the load when all the cylinders are developing power. 7. Cut off cylinder no.1 by lifting the cutoff switch no.1 8. Bring the engine again to rated speed by adjusting the load on brake drum and not by adjusting the load on brake drum and not by adjusting the throttle and note down the corresponding load on the engine. 9. Similarly cut off the cylinder.2,3,4 and repeat the above procedure to find the load on the engine for cylinder. 10. Remove the load from the engine and stop the engine by switching off the ignition switch.

RESULT: Thus the Morse test on Multi Cylinder petrol Engine is done the following observations are made.

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32

REVIEW QUESTION 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

When a car gets older will its compression ratio decrease? What about MEP? What is the working principle of a tachometer? What is indicated power? What is brake power? What is indicated mean effective pressure? What is BMEP? What is the relation between MEP and Swept volume? What are different losses in IC engines? How will you define mechanical efficiency of an engine define? What is brake thermal efficiency?

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THERMAL ENGINEERING LAB MANUAL Calculations Brake power: (

)

Where, N Tn

= Speed in rpm = Torque in Nm

Indicated power when:

Total Indicated Power = IP1 +IP2+IP3+IP4 kW

Total Frictional power loss when all cylinders are working (FPn)

= IPn + BPn kW

(

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)

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FLASH AND FIRE POINT TEST BY CLEAVE LAND OPEN CUP APPARATUS Expt No Date

: :

AIM: To find the flash and fire point of the given fuel / oil by cleave land open cup apparatus.

APPARATUS REQUIRED: 1. Open cup apparatus 2. Thermometer 3. Sample of fuel / oil 4. Splinter sticks

DESCRIPTION OF THE EQUIPMENT: This apparatus consists of a cylindrical cup of standard size. It is held in place in the metallic holder that is placed on a wire gauge and is heated by means of an electric heater housed inside the metallic holder. A provision is made on the top edge of the cup to hold the thermometer in position. A standard filling mark has been scribed on the inner side of the cup and the sample oil is filled up to this mark. This apparatus is more accurate than Pensky Marton’s closed cup and it gives sufficiently proclaimed accurate result for most of the practical purposes.

PROCEDURE: 1. Fill the cleaned open cup with the given sample of oil up to the standard filling mark of the cup. 2. Insert the thermometer in the holder on the top edge of the cup. Make sure that the bulb of the thermometer is immersed in the oil and should not touch the metallic part. 3. Heat the sample of fuel / oil by means of an electric heater so that the sample of oil gives out vapour at the rate of 10°C per minute. 4. When the oil gives out vapours, start to introducing the glowing splinter ( the flame should not touch the oil ) and watch for any flash with flickering sound. 5. Blow out or expel the burnt vapour before introducing the next glowing splinter. This ensures that always fresh vapours alone are left over the surface of the oil and the test is carried out accurately.

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6. Continue the process of heating and placing the glowing splinter at every ten degree of rise in temperature from the first flash till you hear the peak flickering sound and note the corresponding temperature as the flash point. 7. Continue the heating further after retaining the flash point and watch the fire point, which is noted when the body of the oil vapour ignites and continue to burn at least for five seconds. 8. Repeat the test twice or thrice with fresh sample of the same oil until the results are equal. 9. Tabulate the observations.

RESULT: The flash and fire point test is carried out and the following oil / fuel properties are found. The flash point of the given sample fuel / oil is

=

The fire point of the given sample fuel / oil is

=

REVIEW QUESTIONS 1. What is meant by auto ignition temperature? 2. What is the difference between flash point and auto ignition temperature? 3. What is the difference between flash point and fire point? 4. What is the significance of fire and flash points? 5. What are the causes of incomplete combustion? 6. What is enthalpy of combustion? How does it differ from the enthalpy of reaction? 7. What is enthalpy of formation? How does it differ from the enthalpy of combustion? 8. What are the higher and the lower heating values of a fuel? How do they differ? How is the heating value of a fuel related to the enthalpy of combustion of that fuel? 9. What is the nature of enthalpy values for endothermic, exothermic and equilibrium process? 10. Is there any relation between boiling point of a liquid with its flash point?

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OBSERVATION TABLE:

Sl.No.

Temperature

Observations

( °C ) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

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TEMPERATURE DEPENDENCE OF VISCOSITY OF LUBRICATING OIL BY REDWOOD VISCOMETER Expt No

:

Date

:

AIM: To determine the kinematic viscosity of a given oil at different temperatures using capillary viscometer.

APPARATUS REQUIRED: 

Capillary viscometer



Constant temperature water bath



Stop watch.

BRIEF THEORY OF THE EXPERIMENT: Viscosity is a measure of the resistance of a fluid which is being deformed by shear stress. Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction All real fluids (except superfluids) have some resistance to stress and therefore are viscous, but a fluid which has no resistance to shear stress is known as an ideal fluid or inviscid fluid. A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used.

These instruments are used for determining the viscosity of all oils, expressed in Redwood Seconds at the temp. of test. Both the types of viscometers, Redwood no. 1 and Redwood no. 2, electrical heating models are available. The viscometers consists of a heavily silver plated brass oil cup with a precision stainless steel jet assembled in a chromium plated both fitted with a heating tube or heating element and drain cock. The bath and cup assembly is mounted on a stand with leveling feet. Redwood no.1 viscometer is used for all oils having viscosity not more than 2000 sec at the test temperature. Redwood no.2 viscometer, is used for those oils, the viscosity of which exceeds 2000 sec.

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PROCEDURE: 1. Take the required amount of oil sample. 2. Pass the sample through the filter in order to remove the dust particles and store it in a glass bottle. 3. Select a suitable capillary viscometer and clean with suitable solvent. 4. Transfer 15ml of filtered oil sample into the reservoir through the filling tube. 5. Hang the viscometer into the constant temperature bath. 6. Apply vacuum to the venting tube for filling oil to the reference level vessel, the capillary tube, the measuring sphere and the pre run sphere. 7. Discontinue suction in order to open the venting tube. 8. Measure the flow time from upper timing mark to lower timing mark. 9. Calculate the kinematic viscosity using the formula.

CALCULATIONS (

1.

)

⁄

Where , = density of given oil = a constant T= temperature ( )

2.

⁄

Where , A and B are constant T= time taken to collect 50 ml in seconds 3.

( )

RESULT: The kinematic viscosity of the given sample oil is =

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INFERENCE: Viscosity decreases with increase in temperature. The curves obtained follow almost a linear pattern with slight decrease in slope with increase in temperature (i.e. rate of decrease of viscosity with temperature). Both the viscosity and rate of decrease of viscosity with temperature (i.e. slope) were very high for cotton seed oil as compared to diesel oil.

REVIEW QUESTIONS

1. What is turbulent viscosity? 2. What is meant by hydrodynamic boundary layer? 3. How is coefficient of viscosity defined? 4. What is dynamic viscosity? 5. What is the effect of temperature on viscosity on liquids? What about gases? 6. What is the difference between adhesive and cohesive force? 7. What is meant by no slip condition 8. What is meant by Newtonian fluids? 9. What is rheology? 10. What is the physical significance of Nusselt number?

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OBSERVATION TABLE:

Oil Sample:

Sl. No.

Viscometer type: Temperature

Time

Viscosity

(oC)

(Sec)

(Centistokes)

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PERFORMANCE TEST ON RECIPROCATING AIR COMPRESSOR

Expt No

:

Date

:

AIM: To conduct a performance test on the two stage reciprocating air compressor and todetermine the volumetric efficiency and isothermal efficiencies at various delivery pressures.

APPARATUS REQUIRED: 1. Reciprocating air compressor test rig. 2. Manometer 3. Tachometer

SPECIFICATIONS: Power

:

Type

: Two stage reciprocating

Cooling Medium

:

Air Capacity

:

Maximum Pressure

:

Speed

:

BRIEF THEORY OF THE EXPERIMENT:

The two stage reciprocating compressor consists of a cylinder, piston, inlet and exit valves which is powered by a motor. Air is sucked from atmosphere and compressed in the first cylinder (Low pressure) and passed to the second cylinder (High pressure) through an inter cooler. In the second cylinder, air is compressed to high pressure and stored in the air tank.

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During the downward motion of the piston, the pressure inside the cylinder drops below the atmospheric pressure and the inlet valve is opened due to the pressure difference. Air enters into the cylinder till the piston reaches the bottom dead center and as the piston starts moving upwards, the inlet valve is closed and the pressure starts increasing continuously until the pressure inside the cylinder above the pressure of the delivery side which is connected to the receiver tank. Then the delivery valve opens and air is delivered to the air tank till the TDC is reached. At the end of the delivery stroke a small volume of high pressure air is left in the clearance volume. Air at high pressure in the clearance volume starts expanding as the piston starts moving downwards up to the atmospheric pressure and falls below as piston moves downward. Thus the cycle is repeated. The suction, compression and delivery of air take place in two strokes / one revolution of the crank

PRECAUTIONS: 1. The orifice should never be closed so as to prevent the manometer fluid being sucked in to the tank. 2. At the end of the experiment the outlet valve of the reservoir should be opened as the compressor is to be started against at low pressures so as to prevent excess strain on the piston.

EXPERIMENTAL SETUP: The two-stage air compressor consists of two cylinders of ―v‖ type. The compressor is driven by an AC motor.

Air is first sucked into the low pressure (LP) cylinder and it is

compressed and delivered at some intermediate pressure. The compressed air is then cooled in the intercooler and the same is then sucked by the high pressure (HP) cylinder. Compressed air is the finally discharged to the receiver tank. An orifice plate is mounted on one side of the air tank and which is connected with a manometer for the measurement of air flow rate.

One side of the air tank is attached with a

flexible rubber sheet to prevent damage due to pulsating air flow. A pressure gauge is mounted on the air tank to measure the air tank pressure. The tank pressure can be regulated by adjusting the delivery valve. A pressure switch is mounted on the air tank to switch off the motor power

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supply automatically when the pressure inside the tank raises to the higher limit and to avoids explosion.

PROCEDURE: 1. The manometer is checked for water level in the limbs. 2. The delivery valve in the receiver tank is closed. 3. The compressor is started and allowed to build up pressure in the receiver tank. 4. Open and adjust the outlet valve slowly to maintain the receiver tank pressure constant. 5. The dynamometer is adjusted so that the circular balance reads zero when the points at the motor pedestal coincide. This can be done by operating the hand wheel. 6. Note down the readings as per the observation table. 7. Repeat the experiment for various delivery pressures. This can be done by closing the delivery valve and running the compressor to build up higher pressure. Ensure the tank pressure is maintained constant by adjusting the outlet valve before taking the readings. 8. Tabulate the values and calculate the volumetric efficiency and isothermal efficiency.

GRAPH: 1. Gauge pressure Vs Volumetric efficiency 2. Gauge pressure Vs Isothermal efficiency

RESULT: The performance test on the given air compressor test rig is conducted and the volumetric and isothermal efficiencies are determined at various delivery pressures and the characteristic curves are drawn.

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REVIEW QUESTIONS

1. What is the physical significance of enthalpy? 2. Make an energy balance over the air compressor test rig. 3. Write an expression for the time rate of change of the energy content of the CV selected over the air compressor test rig 4. What is the reason for increase in isothermal efficiency with gauge pressure? 5. What is the reason for decrease in volumetric efficiency with gauge pressure? 6. Consider an air compressor operating steadily. How would you compare the volume flow rates of the air at the compressor inlet and exit? 7. Will the temperature of air rise as it is compressed by an adiabatic compressor? Why? 8. Somebody proposes the following system to cool a house in the summer: Compress the regular outdoor air, let it cool back to the outdoor temperature, pass it through a turbine, and discharge the cold air leaving the turbine into the house. From a thermodynamic point of view, is the proposed system sound?

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OBSERVATION TABLE:

Manometer Reading Delivery pressure Sl.No

(kgf /cm2)

Speed

(mm)

Torque h1

h2

h1- h2

Motor

Comp.

kg.m

SPECIMEN CALCULATION: 1. Air head causing the flow

h1, h2

= Manometer reading, mm

ρw

= Density of water = 1000kg/m3

ρair

3 = Density of air, kg/m

Where,

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Pa= Atmospheric pressure R= Gas constant for air = 0.287 KJ/Kg.K T= Room temperature K (

)

2. Actual volume of air compressed )

√(

(

)

Cd = Coefficient of discharge = A = area of orifice

= ( /4) d

d = diameter of orifice

=

2

3. Actual volume of air compressed at NTP ( Va

= Actual volume of air compressed

TNTP

= 273 K

TRTP

= 273 + Room temperature in K

)

4. Theoretical volume of air compressed (

)

Where, D = Diameter of cylinder = L = Stroke length = Nc= Speed of the compressor

5. Volumetric Efficiency

6. Isothermal Power ( )

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THERMAL ENGINEERING LAB MANUAL r = Compression ratio

Pa

= Atmospheric pressure N/m2 (1.01325 x 105 N/m2)

Pg = Pressure in the tank N/m2 (Pressure gauge reading x 105) 7. Input power (

)

Where, I.P.

= Input Power

Nm

= Motor speed rpm

T

= Torque on the motor Kg.m =

8. Isothermal Efficiency

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