This set of Hydraulic Machines Multiple Choice Questions & Answers (MCQs) focuses on “Types of Draft Tube”.
1. Draft tube is also called_______
a) Straight divergent tube
b) Simple elbow tube
c) Thermal tube
d) Elbow tube with varying cross section
View Answer
Explanation: Draft tube is one of the most commonly used in the Kaplan turbine. It works as an outlet at the Kaplan turbine. Draft tube is also called straight divergent tube.
2. A draft tube helps in converting kinetic energy into________
a) Electrical work
b) Mechanical work
c) Chemical work
d) Thermal work
View Answer
Explanation: Turbine extracts energy and converts it into useful work. Turbine is a vortex related device. It means turbulence. Steam turbine converts energy into mechanical work by extracting thermal energy from pressurized steam.
3. Most common application of the draft tube is ______
a) Rotor
b) Motor
c) Pump
d) Filter
View Answer
Explanation: Most common application of the draft tube is different types of pumps. It plays an important role in the putlet of the pump and the turbine.
4. Draft tube consists of conical diffuser with angles of______
a) 10 deg
b) 20 deg
c) 30 deg
d) 40 deg
View Answer
Explanation: Draft tube consists of conical diffuser with angles of 10 degrees with respect to its position, Draft tubes are situated in the outlet of the turbine.
5. What is the purpose of a Draft tube?
a) To prevent flow separation
b) To avoid Pressure drag
c) To prevent rejection of heat
d) To increase efficiency
View Answer
Explanation: Draft tube in a turbine and pumps helps to prevent flow separation in order to increase the turbine efficiency and increase its performance.
6. What is the maximum value of efficiency in a draft tube?
a) 100
b) 50
c) 90
d) 40
View Answer
Explanation: The maximum value of efficiency in a draft tube is 90 percent. It cannot exceed more than 90 percent because of the heat losses due to flow of fluid.
7. The simple elbow draft tube is placed close to the_______
a) Head race
b) Tail race
c) Tank
d) Nozzle
View Answer
Explanation: The simple elbow draft tube is placed close to the tail race. 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.
8. Turbine that consists of draft tubes is called as__________
a) Impulse turbine
b) Curtis turbine
c) Rateau turbine
d) Reaction turbine
View Answer
Explanation: A turbine that consists of draft tubes is called as a reaction turbine. Reaction turbines make maximum use of the draft tubes for improving its performance characteristics.
9. Which of the following is a 50 percent reaction turbine?
a) Parsons turbine
b) Curtis turbine
c) Rateau turbine
d) Pelton wheel
View Answer
Explanation: A turbine that consists of moving nozzles which are alternating with the fixed nozzles is called as a reaction turbine. When the steam hits the nozzle, the pressure is decreased and the temperature is increased. It is also called as Parson’s turbine.
10. The simple elbow draft tube helps to cut down the cost of excavation.
a) True
b) False
View Answer
Explanation: The simple elbow draft tube helps to cut down the cost of excavation. The simple elbow draft tube is placed close to the tail race. 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.
11. The exit diameter for a simple elbow draft tube should be________
a) Large
b) Small
c) Very small
d) Same
View Answer
Explanation: The exit diameter for a simple elbow draft tube should be large as possible. It helps to cut down the cutdown the cost and recover the kinetic energy at the outlet of runner. The simple elbow draft tube is placed close to the tail race.
12. Properties that do not affect a draft tube is _______
a) Pressure
b) Temperature
c) Pressure velocity
d) Velocity
View Answer
Explanation: Temperature does not affect the performance of the draft tube. With increase and decrease of temperature of fluid in a draft tube, the draft tube remains the same.
13. The other name for elbow with varying cross section tube is called_____
a) Pressure tube
b) Bent draft tube
c) Velocity tube
d) Sink tube
View Answer
Explanation: The other name for elbow with varying cross section tube is called bent draft tube. It is so called because only the bent part is of varying cross section. Thus, the answer is bent draft tube.
14. What is the efficiency of the simple elbow type draft tube?
a) 10
b) 30
c) 60
d) 90
View Answer
Explanation: The efficiency of the simple elbow type draft tube is 60 percent. The exit diameter for a simple elbow draft tube should be large as possible. It helps to cut down the cutdown the cost and recover the kinetic energy at the outlet of runner. The simple elbow draft tube is placed close to the tail race.
15. The horizontal portion of the draft tube is usually bent to prevent entry of air from the exit end.
a) True
b) False
View Answer
Explanation: The horizontal portion of the draft tube is usually bent to prevent entry of air from the exit end. This might lead to a mixing up of gases. In order to avoid this, it is important to avoid air entry from exit.
Sanfoundry Global Education & Learning Series – Hydraulic Machines.
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