This set of Rocket Propulsion Multiple Choice Questions & Answers (MCQs) focuses on “Turbopumps”.
1. Which of the following is the term used to denote a turbine with one or more pumps?
a) Turboshaft
b) Turbopump
c) Turboprop
d) Turbojet
View Answer
Explanation: Turbopump is an arrangement with a turbine and one or more pumps. An alternative to turbopump would be the gas pressure feed system. Both of them have varying applications and are employed depending upon the scenario under consideration, e.g. a long-duration mission to the outer space or a missile within the earth’s atmosphere.
2. Main purpose of a turbopump is to ____________
a) decrease the temperature of flowing propellant
b) increase the temperature of flowing propellant
c) decrease the pressure of flowing propellant
d) increase the pressure of flowing propellant
View Answer
Explanation: A turbopump helps in the increase of pressure of the flowing propellants. To initiate the flow of propellants from their storage tanks to the combustion chamber, the propellants must traverse a path of favorable pressure gradient.
3. The propellant enters the pump through __________
a) duct
b) pipe
c) injector
d) inducer
View Answer
Explanation: Inducer can be thought of as a special impeller where the pressure of the propellant is raised by a small amount, typically 5-10% of the total pressure rise. The propellants enter through this inducer to reach the impeller.
4. Majority of the kinetic energy imparted by the impeller to the flow is converted to ___________ in diffuser.
a) potential energy
b) hydrostatic pressure
c) frictional losses
d) internal energy
View Answer
Explanation: It is converted to hydrostatic pressure in the diffuser. Part of this conversion will also take place in the volute.
5. The bearings and shaft seals are cooled using ____________
a) part of the propellant flow
b) radiation cooling
c) part of the Exhaust Flow from the nozzle
d) lubricants
View Answer
Explanation: Parts of the propellant flow is used for cooling of bearings and shaft seals. The heat absorbed by the propellants make it more energetic which can be later used during the combustion and expansion processes in the thrust chamber.
6. A geared turbopump has ___________ efficiency for the turbine and ____________ efficiency for the pump.
a) lower; lower
b) lower; higher
c) higher; lower
d) higher; higher
View Answer
Explanation: Because of the gear system, the two-stage turbine speed is higher than the shaft speed of the pumps and turbine is smaller. It will lead to higher turbine efficiency and higher pump efficiency.
7. Which of these will lead to lower reliability from design perspective of turbopumps?
a) Lower efficiency and higher mass
b) Higher efficiency and lower mass
c) Higher efficiency and higher mass
d) Lower efficiency and lower mass
View Answer
Explanation: From the design perspective, the reliability of a turbopump with higher efficiency and lower mass will be low. The reason is that by selecting such stringent criteria for efficiency and mass acts as restricted design margins.
8. The total propellant flow at the pump outlet is ____________ the flow in combustion chamber and the discharge pressure is __________ chamber pressure plus the other insignificant pressure losses in the system.
a) more than; less than
b) more than; more than
c) less than; more than
d) equal to; equal to
View Answer
Explanation: Mass flow rate remains constant. Hence the total propellant flow will be the same for the pump outlet as well as in the combustion chamber. Favorable pressure difference should be present for the flow to take place. The chamber pressure will be different from the nozzle pressure, but the discharge pressure is kept to be the same as the chamber pressure.
9. If the densities of the propellants are very different from one another, the pump head raise is ___________ for the lower-density propellant compared to higher-density propellant.
a) higher
b) lower
c) equal for both the propellants
d) 0
View Answer
Explanation: Pump head refers to the difference between discharge and suction head of the pump. It is measured in meters or feet. It is much higher for the lower density propellant if the propellant combination used in an engine has a noticeable difference in their densities.
10. ____________ is limited by the possibility of excessive cavitation.
a) Maximum shaft speed
b) Minimum shaft speed
c) Maximum pump gear ratio
d) Minimum pump gear ratio
View Answer
Explanation: Maximum shaft speed is a key pump parameter. It is restricted by the need to avoid excessive cavitation.
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