3 1 ii mid thermal engg questions [pls vist our blog sres11jemeches]

1 3-1 II MID Thermal Engg - II QUESTIONS

THERAMAL ENGINEERING-II (DESCRIPTIVE) & Bits

B MECHANICAL III-ISEM.TEC

1.A) Classify the steam condesers.

B) State briefly explain the sources and effect of air leakage into a condeser

2.A)comparison between impulse turbine and reaction turbine.

B)A 50% reaction turbine( with symmetrical velocity triangles) running at 400 r.p.m. has the exit angle of the blades as 20o and the velocity of steam relative to the blades at the exit is 1.35 times the mean blade speed. The steam flow rate is 8.33 kg/sec and at a particular stage the specific volume is 1.381 m3/kg calculate for this stage

1) A suitable blade height, assumingg the rotor mean diameter 12 times the blade height,

2) The diagram work.

3.A)Describe the bypass turbojet engine.when thise type of engine is used.

B)what are the field applications of pulse jet engines?

4.A)Difference between closed cycle and open cycle gas turbine plant.

B)Define effectiveness of a regenerator.

5.Find the required air-fuel ratio in a gas turbine whose turbine and compressor efficiencies are 85% and 80% respectively. Maximum cycle temperature is 875oc. the working fluid can be taken as air (cp=1 kj/kg k, adiabatic index=1.4 ) which enters the compressor at 1 bar and 27oc. the pressure ratio is 4. The fuel

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used has calorific value of 42000 kj/kg. there is a loss of 10 % of calorific value in the combution chamber.

THERAMAL ENGINEERING-II (OBJECTIVE)

B MECHANICAL III-ISEM.TEC

1. In case of reaction steam turbine [ ]

A) There is enthalpy drop both in fixed and moving blades

B) There is enthalpy drop only in fixed blades

C) There is enthalpy drop only in moving blades D) None of the above

2. Reheat factor in steam turbines depends on [ ]

A) Exit pressure only B) stage efficiency only

C) initial pressure and temperature only D) all of the above

3. In shell and tube surface condenser [ ]

A) cooling water passes through tubes and steam surrounds them

B) steam passes through tubes and cooling water surrounds them

C) steam and cooling water mix D) all of the above

4. Edward’s air pump [ ]



A) Removes air and also vapour from condenser B) Removes only air from condenser

C) Removes only un-condensed vapour from condenser

D) Removes air along with vapour and also the condensed water from condenser

5. For a gas turbine the pressure ratio is in the range [ ]

A) 2 to 3 B) 3 to 5 C) 16 to 18 D) 18 to 22

6. For Parson’s reaction steam turbine, degree of reaction is [ ]

A) 75% B) 100% C) 50% D)60%

7. In a reaction turbine, when the degree of reaction is zero, then there is [ ]

A) No heat drop in the moving blades B) No heat drop in the fixed blades

C) Maximum heat drop in the moving blades D) Maximum heat drop in the fixed blades

8. In jet type condensers [ ]

A) cooling water passes through tubes and steam surrounds them

B) steam passes through tubes and cooling water surrounds them

C) steam and cooling water mix D) steam and cooling water donot mix

9. The work ratio of closed cycle gas turbine plant depends upon [ ]

A) Pressure ratio of the cycle and specific heat ratio



B) Temperature ratio of the cycle and specific heat ratio

C) Pressure ratio, Temperature ratio and specific heat ratio

D) Only on pressure ratio

10. For a jet propulsion unit, ideally the compressor work and turbine work are [ ]

A) Equal B) unequal C) not related to each other D) unpredictable

11. The maximum efficiency for Parson’s reaction turbine is given by (in terms of ‘α’) ___________.

[ ]

A)cos2 α B)sin2 α C) 2cos2α/1+cos2α D) NONE12. The ratio of actual vacuum to the ideal vacuum in a condenser is called ______________.

[ ]

A)vaccume efficiency B) Diagram efficiency

C)thermal efficiency D)None

13. A closed cycle gas turbine works on _______________ cycle. [ ]

A)carnot cycle B) Braton/joules cycle C)Diesel cycle D)None

14. The gas turbine cycle with regenerator improves _________________. [ ]

A) diagram efficiency B) vacuum efficiency

C) Thermal efficiency D)none

15. Degree of reaction as referred to steam turbine is defined as (in terms of Δhm & Δhf) _________.

[ ]



A) (Δhm )/ (Δhm + Δhf) B) Δhm + Δhf

C) (Δhm + Δhf)/ (Δhm ) D)none

16. In a two stage gas turbine plant, with inter cooling and reheating work ratio___________ but thermal efficiency________ [ ]

A ) constant , improves B)improves, constant

C) Improves, improves D) improves, decreases

17. In a closed cycle gas turbine, the air is compressed________ [ ]

A) Adiabatically B) Isentropically C) ReversiblyD)None

18. A closed cycle gas turbine gives ________efficiency as compared to open cycle gas turbine.

[ ]

A) Lower B) same C) Higher D) not change

19. High air-fuel ratio in gas turbines _________exhaust temperature [ ]

A) Reduces B) Same C) More D) Zero

20. The thermal efficiency of a gas turbine cycle with ideal regenerative heat exchanger is ________ work ratio.

[ ]

A) Same B) Equal to C) higher D)none


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