JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II THERMAL ENGINEERING - I Previous Question Paper (February - 2024 - R15)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Define: (i) stroke volume (ii) clearance volume.
Answer
(i) Stroke volume (also known as swept volume) is the volume displaced by the piston as it moves between the top dead center (TDC) and the bottom dead center (BDC). It is calculated as the product of the cross-sectional area of the cylinder bore and the length of the stroke.
(ii) Clearance volume is the minimum volume remaining in the cylinder when the piston reaches the top dead center (TDC). It includes the volume of the combustion chamber and the space between the cylinder head and the piston crown at TDC.
What are the advantages of liquid cooling system?
Answer
The liquid cooling system offers several advantages over air cooling for internal combustion engines:
- Uniform Cooling: Liquid cooling allows for more uniform temperature distribution around the cylinder block and head, which reduces thermal stresses and prevents localized hot spots.
- Compact Design: Because liquid jackets can be integrated into the engine block and head, the overall engine design can be more compact, and the radiator can be placed away from the engine, providing greater flexibility in vehicle layout.
- Quieter Operation: The presence of the water jacket around the cylinder acts as a sound insulator, effectively dampening the combustion noise and resulting in quieter engine operation compared to air-cooled engines with external cooling fins.
Define abnormal combustion.
Answer
Sign in to view the complete answer paper.
Explain the stages of combustion in SI engines.
Answer
Sign in to view the complete answer paper.
What are the various methods for measurement of friction
Answer
Sign in to view the complete answer paper.
Write the effects of engine overheating and engine under cooling.
Answer
Sign in to view the complete answer paper.
Define slip and slip factor and pressure coefficient.
Answer
Sign in to view the complete answer paper.
What do you mean by positive displacement compressor?
Answer
Sign in to view the complete answer paper.
Explain the advantages of open cycle gas turbine.
Answer
Sign in to view the complete answer paper.
What is ozone depletion and global warming?
Answer
Sign in to view the complete answer paper.
Part B
Explain the actual valve timing diagram of a four stroke SI engine and compare with ideal valve timing diagram.
Answer
Sign in to view the complete answer paper.
Describe the working of pressure feed lubrication system with a neat sketch.
Answer
Sign in to view the complete answer paper.
Explain and discuss the phenomenon of diesel knock in CI engines and compare the same with detonation in SI engines.
Answer
Sign in to view the complete answer paper.
What is delay period and discuss the factors that affect the delay period.
Answer
Sign in to view the complete answer paper.
What is the role of anti-knocking agents in internal combustion engine? Explain the anti-knocking agents used in CI and SI engines.
Answer
Sign in to view the complete answer paper.
Why Morse test is not suitable for single cylinder engine? Describe the method of finding friction power using Morse test.
Answer
Sign in to view the complete answer paper.
An engine is used on a job requiring 110 kW B.P., the mechanical efficiency of the engine is 80 % and the engine used 50 kg fuel per hour under the conditions of operation. A design improvement is made which reduces the engine friction by 5 kW. Assuming the indicated thermal efficiency remains the same, how many kg of fuel per hour will be saved.
Answer
Sign in to view the complete answer paper.
Explain the method of conducting retardation test in internal combustion engine and compare this method with Willian’s line method.
Answer
Sign in to view the complete answer paper.
With the help of a neat sketches, explain the working of centrifugal air compressor clearly discussing how the pressure changes take place in impeller and diffuser.
Answer
Sign in to view the complete answer paper.
Draw the schematic diagram vane compressor and explain working.
Answer
Sign in to view the complete answer paper.
What is the function of impeller and diffuser in a centrifugal compressor?
Answer
Sign in to view the complete answer paper.
Explain why now a days axial flow compressors are largely used for aviation gas turbines.
Answer
Sign in to view the complete answer paper.
What are the desirable properties of an ideal refrigerant? Explain.
Answer
Sign in to view the complete answer paper.
A Bell-Coleman refrigerator works between 4 bar and 1 bar pressure limits. After compression, the cooling water reduces the air temperature to 17°C. What is the lowest temperature produced by the ideal machine? Compare the coefficient of performance of this machine with that of the ideal Carnot cycle machine working between the same pressure limits, the temperature at the beginning of compression being -13°C.
Answer
Sign in to view the complete answer paper.
A R-12 vapour compression system has saturated suction temperature of -5°C and saturated discharge temperature of 40°C. The refrigerant vapour is dry-saturated at the suction of compressor and becomes superheated after compression. For one ton of refrigeration capacity, Calculate a) Refrigerating effect b) mass flow rate c) Power and d) COP of the system.
Answer
Sign in to view the complete answer paper.