1. Which among the following is an important parameter to avoid cavitation?
a) Tail race length
b) Head race length
c) Height of draft tube
d) Pump
Explanation: Cavitation in a draft tube occurs when pressure drop takes place. The absolute pressure falls below the saturated vapour pressure of the water for the given temperature. Height of the draft tube is an important parameter to avoid cavitation.
2.The draft tube is situated in the _______
a) Inlet
b) Outlet
c) Tank
d) Nozzle
Explanation: The simple elbow draft tube is placed close to the inlet of the turbine. It consists of an extended elbow type tube. It is mainly used in the Kaplan turbine. It is placed close to the tail race of the turbine.
3. Which equation is applied to determine the flow?
a) Newtons equation
b) Rutherford’s equation
c) Bernoulli’s equation
d) Faradays equation
Explanation: Bernoulli’s equation is used to determine the flow of the fluid from inlet to the outlet. It also helps in avoiding cavitation. Cavitation in a draft tube occurs when pressure drop takes place.
4. Height of the draft tube is denoted by _____
a) H
b) h
c) z
d) x
Explanation: Height of the draft tube is denoted by ‘z’. It is equated to z2, which is attached at the outlet of the turbine. Thus, the universal symbol to denote height of the draft tube is ‘z’.
5. Draft tube allows turbine to be placed above the tail race.
a) True
b) False
Explanation: The draft tube helps to cut down the cost of excavation. The draft tube is placed close to the tail race. The turbine pressure head is increased by decreasing the velocity at the draft tube. Draft tube allows turbine to be placed above the tail race.
6. Specific speed is denoted by ________
a) N
b) n
c) Ns
d) S
Explanation: Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.
7. Specific speeds are used in pumps to determine ________
a) Temperature
b) Reaction speed
c) Suction specific speed
d) Wheel speed
Explanation: Specific speeds are used in pumps to determine. Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.
8. The tube at the exit of the nozzle increases the _______
a) Temperature
b) Pressure
c) Volume of the flow
d) Density of flow
Explanation: The draft tube at the exit of the nozzle increases the pressure in the fluid. It increases it at the expense of its velocity. This means that the turbine can reduce its pressure without fear of back flow to the tail race
9. Specific speed is used to characterize _______
a) Turbomachinery speed
b) Flow speed
c) Energy flow
d) Heat generated
Explanation: Specific speed is used to characterize Turbomachinery speed. Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.
10. Specific speed predicts the shape of a/an _________
a) Pump
b) Density head
c) Impeller
d) Motor
Explanation: Specific speed predicts the shape of an impeller. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.