Exam Details
| Subject | Thermal Engineering | |
| Paper | ||
| Exam / Course | Diploma in Mechanical Engineering (DMEVI)& B.Tech. MECHANICAL ENGINEERING 1-4 (BTMEVI) | |
| Department | School of Engineering & Technology (SOET) | |
| Organization | indira gandhi national open university | |
| Position | ||
| Exam Date | June, 2015 | |
| City, State | new delhi, |
Question Paper
1. Prove that the work done/k.g of air in a compressor is given by
W=RT1
where rp= pressure ratio.
Symbols carry usual meaning.
2. Explain the scavenging process in two-stroke SI engine. What do you understand by blow-down process Why is it necessary What is the difference between the blow-down used in 2-stroke and 4-stroke engines
3. The following data relates to a performance test of a single-acting 14 cm x 10 cm reciprocating compressor.
Suction pressure 1 bar
Suction temperature 20°C
Discharge pressure 6 bar
Discharge temperature 180°C
Speed of compressor =1200rpm
Shaft power 6·25 kW
Mass of air delivered =1·7 kg/min
Calculate the following:
The actual volumetric efficiency
The indicated power
The isothermal efficiency
The mechanical efficiency
The overall isothermal efficiency
4. How are the fuels for SI engines rated Explain the effect of octane number on the performance of SI engine.
5. An 8-cylinder, 4-stroke SI engine develops 16·25 kW brake power when tested on 4000 rpm. The compression ratio of the engine is 7. The testing is carried out for 10 minutes and fuel consumption during testing period is 4·5 kg. Take C.V. of fuel used 45000 kJ/kg. The air passing through the carburettor has 20°C temperature and 1·03 bar pressure. Air measured is 5·45 kg/min. The diameter and stroke both are equal to 8·5 cm.
Determine the following:
bmep
bsfc
The brake thermal and volumemetric efficiency
Air -fuel ratio
6. Explain the construction and working of anyone type of fuel injection pump. illustrate your answer with suitable sketches.
7. What is the function of carburettor In an SI engine, Briefly explain with a neat sketch the operation of a simple flat type carburettOr.
8. Explain the working of a battery ignition system with the help of a neat sketch. What are the main disadvantages of a battery ignition system? How can these be overcome?
9. A 6-cylinder, 4-stroke petrol engine of cylinder bore 89 mm, stroke 101·6 mm has a volume compression ratio of 7 1. The relative efficiency is when the petrol .consumption is 0·218 kg/hp hr. Estimate
the calorific value of petrol
corresponding petrol consumption in kg/hr
Given that the indicated mean effective pressure is 8·4 and speed is 2500 rpm.
10. The following readings were taken during the test of a single-cylinder four-stroke oil engine
Cylinder diameter =250 mm
Stroke length =400 mm
Gross mep bar
Pumping mep =0·5 bar
Engine speed =250 rpm
Net load on the brake =1080 N
Effective diameter of the brake =1.5 m
Fuel used per hour 10 kg
Calorific value of fuel =44300 kJ/kg
Calculate the following:
Indicated power
Brake power
Mechanical efficiency
Indicated thermal efficiency
W=RT1
where rp= pressure ratio.
Symbols carry usual meaning.
2. Explain the scavenging process in two-stroke SI engine. What do you understand by blow-down process Why is it necessary What is the difference between the blow-down used in 2-stroke and 4-stroke engines
3. The following data relates to a performance test of a single-acting 14 cm x 10 cm reciprocating compressor.
Suction pressure 1 bar
Suction temperature 20°C
Discharge pressure 6 bar
Discharge temperature 180°C
Speed of compressor =1200rpm
Shaft power 6·25 kW
Mass of air delivered =1·7 kg/min
Calculate the following:
The actual volumetric efficiency
The indicated power
The isothermal efficiency
The mechanical efficiency
The overall isothermal efficiency
4. How are the fuels for SI engines rated Explain the effect of octane number on the performance of SI engine.
5. An 8-cylinder, 4-stroke SI engine develops 16·25 kW brake power when tested on 4000 rpm. The compression ratio of the engine is 7. The testing is carried out for 10 minutes and fuel consumption during testing period is 4·5 kg. Take C.V. of fuel used 45000 kJ/kg. The air passing through the carburettor has 20°C temperature and 1·03 bar pressure. Air measured is 5·45 kg/min. The diameter and stroke both are equal to 8·5 cm.
Determine the following:
bmep
bsfc
The brake thermal and volumemetric efficiency
Air -fuel ratio
6. Explain the construction and working of anyone type of fuel injection pump. illustrate your answer with suitable sketches.
7. What is the function of carburettor In an SI engine, Briefly explain with a neat sketch the operation of a simple flat type carburettOr.
8. Explain the working of a battery ignition system with the help of a neat sketch. What are the main disadvantages of a battery ignition system? How can these be overcome?
9. A 6-cylinder, 4-stroke petrol engine of cylinder bore 89 mm, stroke 101·6 mm has a volume compression ratio of 7 1. The relative efficiency is when the petrol .consumption is 0·218 kg/hp hr. Estimate
the calorific value of petrol
corresponding petrol consumption in kg/hr
Given that the indicated mean effective pressure is 8·4 and speed is 2500 rpm.
10. The following readings were taken during the test of a single-cylinder four-stroke oil engine
Cylinder diameter =250 mm
Stroke length =400 mm
Gross mep bar
Pumping mep =0·5 bar
Engine speed =250 rpm
Net load on the brake =1080 N
Effective diameter of the brake =1.5 m
Fuel used per hour 10 kg
Calorific value of fuel =44300 kJ/kg
Calculate the following:
Indicated power
Brake power
Mechanical efficiency
Indicated thermal efficiency
Other Question Papers
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- Advanced Dynamics Of Machine
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- Refrigeration And Air Conditioning
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- Thermofluid Engineering
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