# [TE] ME 204 THERMAL ENGINEERING S4 KTU MODEL QUESTION PAPERS FOR KTU STUDENTS [SECOND YEAR]

__APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY__**THERMAL ENGINEERING S4 KTU**

**QUESTION PAPERS**

__Part A__

__Answer any three full questions__The pressure in the boilers and main is 20 bar. The temperature of steam from a boiler with a super heater is

350°C and temperature of the steam in the main is 250°C.

Determine the quality of steam supplied by the other boiler. Take Specific heat of superheated steam as 2.25 kJ/kg.

5 marks

1b.Explain the characteristic features of a fire tube boiler. How it is different from a water tube boiler? 5 marks

2a.Explain velocity compounded impulse steam turbine showing pressure and velocity variations along the axis.

Why does a two row Curtis stage most often used as the first stage in large steam turbines? 5 marks

2b.What do you understand by reheat factor and condition line? Why reheat factor is greater than unity? 5 marks

3.Steam is the working fluid in an ideal Rankine cycle with superheat and reheat.

Steam enters the first-stage turbine at 8.0 MPa, 4800C, and expands to 0.7 MPa.

It is then reheated to 4400C before entering the second-stage turbine, where it expands to the condenser pressure of 0.008 MPa.

The net power output is 100 MW. Determine(a) the thermal efficiency of the cycle, (b) the mass flow rate of steam, in kg/h, (c) the rate of heat transfer from the condensing steam as it passes through the condenser, in MW. 10 marks

4.The velocity of steam entering simple impulse turbine is 1000 m/s and the nozzle angle is 200.

The mean peripheral velocity of the blades is 400 m/s and

the blades are symmetrical. If the steam enters the blades without shock, what will be the blade angles?

Neglecting friction effects on the blades, calculate

tangential force on the blades and the diagram power for a mass flow of 0.75 kg/s.

Also estimate axial thrust and diagram efficiency.

10 marks

__Part B__

__Answer any three full questions__

5b.“Supercharging is more preferred in C.I. Engines than S.I. Engines”.

Comment on the above statement. 5 marks

6a.List out required characteristics of a C.I. Engine fuels. How C.I. engine fuels are rated? 5 marks

6b.A twin cylinder two stroke engine has a swept volume of 150 cm3. The maximum power output is 19 kW at 11000 rpm, brake specific fuel consumption (bsfc) is 0.11 kg/MJ and air-fuel ratio is 12.

If ambient test conditions were 300C and 1 atmosphere, and the fuel has calorific value of 44 MJ/kg, calculate brake mean effective pressure and overall efficiency. 5 marks

7.Two engines are operating on Otto and Diesel cycles with following data:

Maximum temperature = 1500 K, Exhaust temperature = 700 K, Assume ambient conditions are 1 bar and 300 K.

Determine their air standard efficiencies and comment on your results. 10 marks

8.In a test of 4 cylinder 4 stroke engine 75 mm bore and 100 mm stroke engine, the following results were obtained at full throttle at a particular constant speed and with fixed setting of fuel supply of 6 kg/h.

B.P with all cylinder working = 15.60 kW

B.P with cylinder no.1 cut out = 11.10 kW

B.P with cylinder no.1 cut out = 11.03 kW

B.P with cylinder no.1 cut out = 10.88 kW

B.P with cylinder no.1 cut out = 10.66 kW

If the calorific value of fuel is 83600kJ/kg and clearance volume is 0.0001 m3, calculate: (i) Mechanical efficiency (ii) Indicated thermal efficiency (iii) Air standard efficiency.

10 marks

__Part C__

__Answer any four full questions__

9b.Explain various stages of combustion in C.I. Engines with a sketch of pressure vs crank angle diagram. 7 marks

10a.Describe the effects of knocking in S.I. Engines. 3 marks

10b.What are the design considerations for combustion chambers for SI Engine?

Describe different types of S.I. Engine combustion chambers with diagrams. 7 marks

11a.How do you account the performance of biogas as an alternative fuel for C.I. Engines? 3 marks

11b.What is meant by ‘Euro-Norms’? Explain different methods for controlling pollutant emission from I.C Engines?

7 marks

12a.“The back work ratio of a gas turbine plant is relatively higher than that of a steam power plant”.

How do you evaluate the above statement? 3 marks

12b.Determine the pressure ratio across the compressor of an ideal Brayton cycle for the maximum net work output per unit of mass flow if the state at the compressor inlet and the temperature at the turbine inlet are fixed.

Use a cold air-standard analysis and ignore kinetic and potential energy effects. 7 marks

13a.Discuss the effect of intercooling and reheating on a gas turbine performance. 3 marks

13b.Consider an open cycle constant pressure gas turbine. Air enters the compressor at 1 bar and 300K.

Air pressure after compression is 4 bar. Take isentropic

efficiencies of both compressor and turbine to be 85% .The air-fuel ratios used is 80:1.

If the flow rate of air is 2.5 kg/s, find the power output and thermal efficiency of the cycle. Tale Cp =1 kJ/kgK and Î³ =1.4 for air and gases.

Calorific value of fuel used = 42000 kJ/kg. 7 marks

14a.Give a short note on merits and demerits of gas turbine plant compared to internal combustion engines. 3 marks

14b.In an air standard Brayton cycle the minimum and maximum temperature are 300 K and 1200 K, respectively.

The pressure ratio is that which maximizes the net work developed by the cycle per unit mass of air flow.

Calculate the compressor and turbine work, each in kJ/kg air, and thermal efficiency of the cycle. 7 marks

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