ME2301 Thermal Engineering B.E Question Bank : valliammai.co.in

Name of the College : Valliammai Engineering College
Subject : Thermal Engineering
Subject Code : ME2301
Website : valliammai.co.in
Document Type : Question Bank
Department : Mechanical Engineering
Semester : V
Degree : B.E

Question Bank : https://www.pdfquestion.in/uploads/valliammai.co.in/2833-ME2301-Thermal%20Engineering.pdf

Valliammai Thermal Engineering Question Paper

UNIT I

GAS POWER CYCLES
Part-A
1. What is thermodynamic cycle?
2. List out the assumptions made for the analysis of thermodynamic air cycles.
3. Sketch the Otto cycle on P-V and T-S planes and name all the processes.
4. Define air standard cycle efficiency of an Otto Cycle.

Related : Valliammai Engineering College ME2302 Dynamics of Machinery B.E Question Bank : www.pdfquestion.in/2834.html

5. How does the change in compression ratio affect the air standard efficiency of an ideal Otto cycle?
6. Define MEP as applied to gas power cycles. What is its significance?
7. Write the expression for MEP for an Otto cycle in terms of compression ratio and other parameters.
8. In an Otto cycle, pressure ratio during compression is 11. Calculate the air standard cycle efficiency.
9. A Carnot cycle works between the temperatures 300K and 700K. Find the maximum work possible per kg of air.
10. Sketch the Diesel cycle on P-V and T-S planes and mention the four thermodynamic processes involved.

11. A Diesel engine has a compression ratio of 14 and cut-off takes place at 6% of the stroke. Find the air standard efficiency.
12. Draw the actual p-v diagram for four stroke SI Engine.
13. Define air standard cycle efficiency of a diesel Cycle.
14. Name the factors that affect the air standard efficiency of diesel cycle.
15. Define the terms compression ratio and cutoff ratio.
16. What is the effect of cut-off ratio on the efficiency of diesel cycle when the compression ratio is kept constant?
17. Sketch the Dual cycle on P-V and T-S planes and mention the various processes.
18. Sketch the PV & TS diagram for Otto cycle and Diesel cycle and Dual cycle for the same compression ratio and heat rejection, compare the efficiency.
19. For the same compression ratio and heat supplied, state the order of decreasing air standard efficiency of Otto, Diesel and Dual cycles.
20. Sketch the Brayton cycle (Limited pressure cycle) on P-V and T-S planes and mention the various processes.

Part-B
Otto Cycle:
1. Derive an expression for air standard efficiency of an Otto cycle. Obtain an expression for mean effective pressure of an Otto cycle.
2. In an engine working on constant volume cycle, the pressure, temperature and volume at the beginning of the cycle are 1.2 bar, 35oC and 0.5 m3 respectively. At the end of compression stroke, the pressure is 12 bar. 315 kJ of heat is added per kg of gas during constant volume heating process. Calculate the pressure, temperature and volume at all points. Also find the air standard efficiency of the cycle.
3. A six cylinder petrol engine has a compression ratio of 5 :1. The clearance volume of each cylinder is 110CC. It operates on the four stroke constant volume cycle and the indicated efficiency ratio referred to air standard efficiency is 0.56. At the speed of 2400 rpm, it consumes 10kg of fuel per hour. The calorific value of fuel is 44000KJ/kg. Determine the average indicated mean effective pressure.

Diesel Cycle:
4. Derive an expression for mean effective pressure of a Diesel cycle in terms of pressure ratio, cutoff ratio and compression ratio.
5. An air standard Diesel cycle has a compression ratio of 12 and cutoff takes place at 6% of the stroke. Calculate the air standard efficiency of the cycle.
6. 1kg of air is taken through a diesel cycle. Initially the air is at 25oC and 1 bar. The compression ratio is 14 and the heat added is 1850KJ. Calculate the ideal cycle efficiency and the mean effective pressure.

Dual Cycle:
7. In a dual cycle the air is compressed isentropically to 1/14th of its initial volume. At the end of compression heat is added at constant volume till its pressure increases to twice the pressure at the end of compression. Then heat is added at constant pressure till its volume increases to twice the volume after compression. Find the efficiency of the cycle.
8. In engine working on Dual cycle, the temperature and pressure at the beginning of cycle are 90oC and one bar. The compression ratio is 9. The maximum pressure is limited to 68bar and total heat supplied per kg of air is 1750kJ. Determine air standard efficiency and mean effective pressure.

Brayton Cycle:
9. Derive an expression for air standard efficiency of a Brayton cycle in terms of pressure ratio and compression ratio. Also prove that the pressure ratio for maximum work is a function of limiting temperature ratio.
10. The extreme of pressure and temperature in an open circuit constant pressure gas turbine plant are 1 bar, 5.25bar and 25oC and 560oC respectively. The isentropic efficiency of the turbine is 88% and that of the compressor is 84%. Determine the efficiency of the plant.

UNIT II

INTERNAL COMBUSTION ENGINES
Part-A
1. Write any two major differences between ‘SI engine’ and ‘CI engine’.
2. Compare two stroke and four stroke engines.
3. Why diesel engines are more efficient than petrol engines?
4. Which is better efficient two stroke or four stroke engines? Why?
5. What is the function of camshaft and crankshaft?
6. What is the function of pushrod and rocker arm?
7. What are the functions of piston rings?
8. Name the basic thermodynamic cycles of two types of internal combustion reciprocating engines.
9. What is meant by highest useful compression ratio?
10. Why compression ratio of a petrol engine is low while diesel engines have high compression ratio?
11. Compare the thermal efficiency of petrol engines with diesel engines. Give reasons.
12. Why the actual cycle efficiency is much lower than the air-standard cycle efficiency? List and explain the major losses in an actual engine.
13. State the air-fuel ratio requirements of SI engine under various operating conditions.
14. Differentiate between ideal and actual valve timing diagram of a petrol engine.
15. Draw port-timing diagram of petrol engine.
16. What is scavenging in IC engines?
17. What is the function of a carburettor? What is carburetion?
18. Why a choke is used in carburettor and what is meant by automatic chocking?
19. What are the limitations of simple carburettor?
20. During peak power operation, why petrol engine requires rich mixture?

Part-B
1. (a) Explain any four types of classification of internal combustion engines.
(b) Draw the valve timing diagram for a 4 stroke SI Engine.
2. (a) Explain any four types of classification of Internal Combustion engines.
(b) With a neat sketch explain any one type of ignition system.
3. Explain the working of 4-stroke cycle Diesel engine. Draw theoretical and actual valve-timing diagram for the engine. Explain the reasons for the difference.
4. Explain why cooling is necessary in I.C. engine. With neat sketches describe the working of water cooling system used for multi-cylinder engine. Why should a pump and thermostat be provided in the cooling system of an engine?
5. Explain with neat sketches the method of lubrication of the following parts of the I.C. Engines. (i) Piston and cylinder (ii) Crank-pin and Gudgeon pin (iii) Cam-shaft.
6. (i) Explain with neat sketch Air Cooling of Engines. (ii) Explain any one lubrication system adopted in multi cylinder SI engines.
7. Explain the principle of Magneto ignition system. Enumerate its advantages and disadvantages?
8.(a) What are the various factors influencing the flame speed in SI Engines?
(b) Explain the combustion phenomenon in SI Engines.
9. (a) What is the purpose of cooling an I.C. Engine? (b) What are the ill effects of improper cooling?
(c) With neat sketches, describe how a fuel injection pump supplies fuel to a diesel engine for different load conditions.
(d) Explain the normal combustion and knocking in a diesel engine with pressure-crank angle diagram
10. (i) Explain the function of a fuel injection pump with a simple sketch. (8)
(ii) What are the advantages and disadvantages of Magneto ignition system over Batter ignition system? (8)