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Q17. A volume of 0.05 m³ of a perfect gas for which R = 0.297 kJ/kgK and C_p = 1.04 kJ/kg K is compressed reversibly in a cylinder according to the law pV^l.33 = constant and then cooled at constant pressure. The initial temperature is 27℃ and the final pressure is 8.5 times the initial pressure. The final volume is 0.007 m³.

(a) Sketch the processes on p-V and T-S diagrams, (4)

(b) Determine EACH of the following:

(i) the temperature after compression; (2)

(ii) the final temperature; (2)

(iii) the net heat transfer per kg; (5)

(iv) the net change in specific entropy. (3)

Q20. (a) Describe how the Morse Test is used co estimate the indicated power of a multi- cylinder engine. (4)
(b) Slate ONE reason why the Morse Test may be less accurate than using engine indicators. (2)

(c) A four cylinder two-stroke CI engine is run under test at a steady speed of 450 rev/min and delivers a brake torque of 12 kNm. The following measurements were then made with the engine running at 450 rev/min:
fuel shut off from cylinder No. 1     brake torque = 8.5 kNm
fuel shut off from cylinder No. 2     brake torque = 8.3 kNm
fuel shut off from cylinder No. 3     brake torque = 8.4 kNm
fuel shut off from cylinder No. 4     brake torque = 8.7 kNm
Determine EACH of the following:
(i) the brake power; (2)
(ii) the indicated power; (3)
(iii) the bore and stroke of each cylinder, given that the stroke/bore ratio is 1.2 and the indicated mean effective pressure in cylinder No. 1 is 7.6 bar. (5)

Q19. The mass analysis of a fuel is: carbon 80%; hydrogen 17%; sulphur 2.1%; water 3%. (remainder ash).

Determine EACH of the following:

(a) The theoretical air/fuel ratio by mass; (6)

(b) The volumetric analysis of the dry products (i.e excluding H₂O and soluble SO₂) when the fuel is burned completely in 25% excess air; (6)

(c) The dew point temperature of the combustion products if the total pressure is 1.01 bar.(4)

Note:  Atomic mass relationships: H = 1; C = 12; O = 16; N = 14; S = 32

Air contains 21% oxygen by volume and 23.3% oxygen by mass.

Q5. A gas turbine plant operates on the ideal air standard Joule cycle. The maximum temperature and pressure are 1200 K and 6 bar respectively. The minimum temperature and pressure are 300 K and 1 bar respectively.
The turbine exhaust passes through a heat exchanger and supplies heat to an ideal Rankine cycle steam plant which operates between pressures of 40 bar and 0.1 bar. The steam leaves the heat exchanger dry and saturated. The exhaust gas leaves the heat exchanger at the saturation temperature of the evaporating steam. Feed pump work in the Rankine cycle plant may be disregarded.
Determine EACH of the following:

(a) the mass of steam per kg of air; (6)

(b) the thermal efficiency of the combined plant. (10)

Note:  For air, γ = 1.4 and c_P = 1.005 kJ/kg K.

Q7. (a) Define the term degree of reaction relating to a turbine stage. (2)

(b) In a 50% reaction turbine stage the steam leaves the fixed blades with a velocity of 300 m/s. The blade ring diameter is 0.8 m and the speed of rotation is 6000 rev/min. The blade angle is 72°

Determine EACH of the following:

(i) The blade outlet angle; (5)

(ii) The blade work per kg; (3)

(iii) The diagram efficiency. (6)

Q1. (a) Explain the term choked flow with reference to a convergent nozzle. (4)

(b) Air leaks from a large pressure vessel to the surroundings which are at a pressure of 1.00 bar. The passage through which the air leaks may be considered as a convergent nozzle with exit area 0.5 mm², and the flow within the passage may be assumed isentropic. The temperature in the vessel may be assumed constant at 28°C.

Determine the mass flow rate when the pressure in the vessel is:

(i) 2.5 bar; (6)

(ii) 1.5 bar. (6)

Note: For air, g = 1.4 and R = 0.287 kJ/kg K

p_c = p_o × [2/(γ + 1)]^γ/γ-1; a = √γRT