Compressors, Gas Turbines and Jet Engines - Set 09

Practice Test: Question Set - 09

1. In n₁ and n₂ are the indices of compression for the first and second stage of compression, then the ratio of work-done on the first and second stages (W₁/W₂) with perfect intercooling is given by
    (A) W₁/W₂ = n₂(n₁ - 1)/n₁(n₂ - 1)
    (B) W₁/W₂ = n₁(n₂ - 1)/n₂(n₁ - 1)
    (C) W₁/W₂ = n₁/n₂
    (D) W₁/W₂ = n₂/n₁

2. For supplying intermittent small quantity of air at high pressure, following compressor is best suited
    (A) Centrifugal
    (B) Reciprocating
    (C) Axial
    (D) Screw

3. The absolute pressure of air at the outlet of a compressor is called
    (A) Back pressure
    (B) Critical pressure
    (C) Discharge pressure
    (D) None of these

4. For minimum work in multistage compression, assuming same index of compression in all stages
    (A) Work done in first stage should be more
    (B) Work done in subsequent stages should increase
    (C) Work done in subsequent stages should decrease
    (D) Work done in all stages should be equal

5. The volume of air delivered in a medium capacity air compressor per unit time is
    (A) 0.1 to 1.2 m³/s
    (B) 0.15 to 5 m³/s
    (C) Above 5 m³/s
    (D) None of these

6. For a two stage compressor, if index of compression for higher stage is greater than index of compression for lower stage, then the optimum pressure as compared to ideal case will
    (A) Increase
    (B) Decrease
    (C) Remain unaffected
    (D) Other factors control it

7. Which one of the following is the effect of blade shape on performance of a centrifugal compressor?
    (A) Backward curved blades has poor efficiency
    (B) Backward curved blades lead to stable performance
    (C) Forward curved blades has higher efficiency
    (D) Forward curved blades produce lower pressure ratio

8. Diffuser in a compressor is used to
    (A) Increase velocity
    (B) Make the flow streamline
    (C) Convert pressure energy into kinetic energy
    (D) Convert kinetic energy into pressure energy

9. A closed cycle gas turbine consists of a
    (A) Compressor
    (B) Heating chamber
    (C) Cooling chamber
    (D) All of these

10. The ratio of isentropic work to Euler’s work is known as
    (A) Compressor efficiency
    (B) Isentropic efficiency
    (C) Euler's efficiency
    (D) Pressure coefficient

11. The mass of gas turbine per kW developed is about ________ as that of an I.C. engine.
    (A) Same
    (B) One-half
    (C) One fourth
    (D) One sixth

12. The thermodynamic efficiency of rotary compressor is based on
    (A) Isothermal compression
    (B) Adiabatic compression
    (C) Isentropic compression
    (D) Polytropic compression

13. The type of rotary compressor used in aeroplanes, is of
    (A) Centrifugal type
    (B) Axial flow type
    (C) Radial flow type
    (D) None of these

14. Phenomenon of choking in compressor means
    (A) No flow of air
    (B) Fixed mass flow rate regardless of pressure ratio
    (C) Reducing mass flow rate with increase in pressure ratio
    (D) Increased inclination of chord with air steam

15. The assumption made in two stage compression with inter-cooler is that
    (A) There is no pressure drop in the inter-cooler
    (B) The compression in both the cylinders is polytropic
    (C) The suction and delivery of air takes place at constant pressure
    (D) All of the above

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Compressors, Gas Turbines and Jet Engines:
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