Jawaharlal Nehru Technological University Hyderabad B. Tech III THERMAL ENGINEERING – I Previous Question Paper (August/September - 2024 - R16)

State importance of ignition systems in IC engines and list out the different methods employed.

Differentiate air standard cycles and vapour power cycles.

Define the use of anti-knock additives. Give a few examples.

A gas engine has a swept volume of 300 cm³ and a clearance volume of 25 cm³. Its volumetric efficiency is 0.875 and its mechanical efficiency is 0.90. What is the volume of the mixture taken in per stroke?

How does the cylinder pressure measurement contribute to engine performance evaluation?

State the significance of clearance volume in reciprocating compressor performance.

How does the design of the vane mechanism contribute to its performance?

Define the pressure coefficient and adiabatic coefficient of centrifugal compressors.

Define the unit of refrigeration. How is it calculated, and what does it represent?

List out the key requirements for an air conditioning system to operate effectively and efficiently.

Compare the 4-stroke and 2-stroke engines.

Describe the significance of valve and port timing diagrams in optimizing the performance of IC engines.

Determine the percentage of excess air in a combustion process where 50 kg of methane (CH₄) is burned with 200% excess air. Calculate the mass of dry flue gas produced assuming complete combustion.

Calculate the adiabatic flame temperature for the complete combustion of methane (CH₄) with air at standard conditions. Assume complete combustion and air contains 21% oxygen by volume.

Compare I and F-type combustion chambers.

Discuss the importance of flame speed and effects of engine variables over the flame speed.

Explain the four different phases of combustion in CI engines.

Describe Diesel fuel requirements and fuel rating.

A four stroke four-cylinder diesel engine running at 300 rpm produces 250 kW of brake power. The cylinder dimensions are 30 cm bore and 25 cm stroke. Fuel consumption rate is 1 kg/min while air fuel ratio is 10. The average indicated mean effective pressure is 0.8 MPa. Determine brake thermal efficiency of engine. The calorific value of fuel is 43 MJ/kg. The ambient conditions are 1.013 bar, 27ºC.

Explain the following: (i) Mechanical efficiency, (ii) Indicated thermal efficiency, (iii) Mean effective pressure.

Derive an expression for optimum intermediate pressure of the multistage compression with perfect intercooling.

A two-stage compressor takes in 2.82 m³ of air per minute at a pressure of 1.05 bar and temperature of 22°C. It delivers air at 8.44 bar. The compression is carried out in each cylinder according to the law pv^1.2 = constant. The air is cooled to its initial temperature in intercooler. By neglecting clearance, determine the minimum power required to drive the compressor.

A Roots blower rotary compressor has an inlet temperature of 300 K and an outlet temperature of 350 K. If the compressor has an efficiency of 0.75, calculate the actual work done by the compressor for a volume displacement of 0.02 m³ per revolution.

A centrifugal compressor with an impeller diameter of 0.5 meters is operating with an inlet velocity of 50 m/s and an outlet velocity of 150 m/s. If the blade angles at the inlet and outlet are 30 degrees and 20 degrees respectively, calculate the degree of reaction. Also, determine the power required to drive the compressor if the mass flow rate is 10 kg/s.

Describe the construction and working principle of axial flow compressors.

An axial flow compressor has an inlet velocity of 100 m/s and an outlet velocity of 200 m/s. If the blade angle at the inlet is 30 degrees and at the outlet is 20 degrees, calculate the degree of reaction.

Explain the working of a vapour absorption refrigeration system with suitable schematic layout.

A vapour compressor refrigerator works between the temperature limits of -10 ºC and 45 ºC. The working fluid (methyl chloride) is just dry saturated at the entry of the compressor, and after the compression it acquires a temperature of 45 ºC. Determine the COP of the refrigerator. Take data: Saturation temp -10 ºC, Enthalpy L: 45.4, V: 460.7, Entropy L: 0.183, V: 1.167; 45 ºC, Enthalpy L: 133.0, V: 483.6, Entropy L: 0.485, V: 1.587.

Explain the working of a split air-conditioner with a suitable diagram.

A theatre of 1200 seating capacity is to be air-conditioned for summer conditions. Outdoor = 30 ºC DBT and 55% RH; Indoor = 20 ºC DBT and 60% RH. Amount of air supplied = 0.25 m³/min/person. Find the sensible heat factor and latent heat factor.