1. The formation of vapour cavities is called _____
a) Static pressure drop
b) Cavitation
c) Isentropic expansion
d) Emulsion
Explanation: The formation of vapour cavities is called cavitation. It is formed due to the presence of small free liquids with different zones. These zones consists of different layers of forces acting on them.
2.What is the degree of reaction denoted as?
a) D
b) R
c) r
d) d
Explanation: Degree of reaction is defined as the ratio of the static pressure drop in the rotor to the static pressure drop in the stage. It can also be defined in the same way for enthalpy in different stages. It is denoted by the letter ‘R’
3. Voids are created due to______
a) Reaction ratio
b) Pressure ratio
c) Liquid free layers
d) Volumetric layers
Explanation: Voids in a turbine or pump is created due to the presence of liquid free layers. It is formed due to the presence of small free liquids with different zones. These zones consists of different layers of forces acting on them.
4. Cavitation usually occurs due to the changes in ________
a) Pressure
b) Temperature
c) Volume
d) Heat
Explanation: Cavitation usually occurs due to the changes in pressure. The pressure change is so rapid that it leads to formation of liquid free layers or cavities that start to affect the overall performance.
5.Degree of reactions are most commonly used in________
a) Turbomachinery
b) Pressure drag
c) Aerodynamics
d) Automobiles
Explanation: Degree of reaction is most commonly used in turbomachinery. Degree of reaction is defined as the ratio of the static pressure drop in the rotor to the static pressure drop in the stage. It can also be defined in the same way for enthalpy in different stages. It is denoted by the letter ‘R’.
6.At high pressure, the voids can generate ______
a) Drag force
b) Mass density
c) Shock waves
d) Flow speed
Explanation: At high pressure, the voids can generate shock waves. Cavitation usually occurs due to the changes in pressure. The pressure change is so rapid that it leads to formation of liquid free layers or cavities that start to affect the overall performance.
7. Voids that implode near metal surface develops a_______
a) Drag force
b) Cyclic stress
c) Shock waves
d) Flow speed
Explanation: Voids that implode near metal surface develops a cyclic stress. This happens mainly due to repeated implosion of voids. Thus, option ‘b’ is correct.
8.In case of gas turbines and compressors, degree of reaction is ________
a) Static pressure drop in rotor/ static pressure drop in stage
b) Static pressure drop in stage/ static pressure drop in rotor
c) Isentropic enthalpy drop in rotor/ isentropic enthalpy drop in stage
d) Static temperature drop in stage/ static temperature drop in rotor
Explanation: Degree of reaction in terms of gas turbines and compressors is defined as the ratio of isentropic enthalpic drop that is developed in the rotor such as the moving blades to that of the isentropic heat drop in the fixed blades.
9. Non- inertial cavitation is the one in which a bubble of fluid is forced to oscillate.
a) True
b) False
Explanation: Non- inertial cavitation is the one in which a bubble of fluid is forced to oscillate. It oscillates in a different size or shape due to some form of energy called the acoustic field.
10.The efficiency of the vane is given by_________
a) 1-V22/ V12
b) 1-(V22/ V12)
c) V22/ V12
d) 1- V12
Explanation: In a velocity triangle at the inlet and the outlet, the control volume is moving with a uniform velocity. Therefore, the momentum theorem of the control volume is at a steady flow. Thus, the efficiency of the vane is given by 1-(V22/ V12).