Turbopump
A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpose of a turbopump is to produce a high-pressure fluid for feeding a combustion chamber or other use. While other use cases exist, they are most commonly found in liquid rocket engines.
There are two common types of pumps used in turbopumps: a centrifugal pump, where the pumping is done by throwing fluid outward at high speed, or an axial-flow pump, where alternating rotating and static blades progressively raise the pressure of a fluid.
Axial-flow pumps have small diameters but give relatively modest pressure increases. Although multiple compression stages are needed, axial flow pumps work well with low-density fluids. Centrifugal pumps are far more powerful for high-density fluids but require large diameters for low-density fluids.
History
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Rocket_engine_A4_V2.jpg/170px-Rocket_engine_A4_V2.jpg)
Early development
High-pressure pumps for larger missiles had been discussed by rocket pioneers such as
Development from 1947 to 1949
The principal engineer for turbopump development at Aerojet was George Bosco. During the second half of 1947, Bosco and his group learned about the pump work of others and made preliminary design studies. Aerojet representatives visited Ohio State University where Florant was working on hydrogen pumps, and consulted Dietrich Singelmann, a German pump expert at Wright Field. Bosco subsequently used Singelmann's data in designing Aerojet's first hydrogen pump.[4]
By mid-1948, Aerojet had selected centrifugal pumps for both liquid hydrogen and liquid oxygen. They obtained some German radial-vane pumps from the Navy and tested them during the second half of the year.[4]
By the end of 1948, Aerojet had designed, built, and tested a liquid hydrogen pump (15 cm diameter). Initially, it used
After 1949
The
Centrifugal turbopumps
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fe/Centrifugal_2.png/220px-Centrifugal_2.png)
Most turbopumps are centrifugal - the fluid enters the pump near the axis and the rotor accelerates the fluid to high speed. The fluid then passes through a
Axial turbopumps
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/ca/Axial_compressor.gif/220px-Axial_compressor.gif)
Axial turbopumps also exist. In this case the axle essentially has propellers attached to the shaft, and the fluid is forced by these parallel with the main axis of the pump. Generally, axial pumps tend to give much lower pressures than centrifugal pumps, and a few bars is not uncommon. Their advantage is a much higher volumetric flowrate. For this reason they are common for pumping liquid hydrogen in rocket engines, because of its much lower density than other propellants which usually use centrifugal pump designs. Axial pumps are also commonly used as "inducers" for centrifugal pumps, which raise the inlet pressure of the centrifugal pump enough to prevent excessive cavitation from occurring therein.
Complexities of centrifugal turbopumps
Turbopumps have a reputation for being extremely hard to design to get optimal performance. Whereas a well engineered and debugged pump can manage 70–90% efficiency, figures less than half that are not uncommon. Low efficiency may be acceptable in some applications, but in rocketry this is a severe problem. Turbopumps in rockets are important and problematic enough that launch vehicles using one have been caustically described as a "turbopump with a rocket attached"–up to 55% of the total cost has been ascribed to this area.[7]
Common problems include:
- excessive flow from the high-pressure rim back to the low-pressure inlet along the gap between the casing of the pump and the rotor,
- excessive recirculation of the fluid at inlet,
- excessive vortexing of the fluid as it leaves the casing of the pump,
- damaging cavitation to impeller blade surfaces in low-pressure zones.
In addition, the precise shape of the rotor itself is critical.
Driving turbopumps
One of such cases are
Ramjet motors are also usually fitted with turbopumps, the turbine being driven either directly by external freestream ram air or internally by airflow diverted from combustor entry. In both cases the turbine exhaust stream is dumped overboard.
See also
- Turboexpander
- Gas-generator cycle
- Staged combustion cycle
- Expander cycle
- Components of jet engines
References
- ^ ISBN 0-674-77650-X.
- ISBN 1-894959-00-0. Archived from the originalon 2012-03-04.
- ^ Dornberger, Walter (1954) [1952]. Der Schuss ins Weltall / V-2. US translation from German. Esslingan; New York: Bechtle Verlag (German); Viking Press (English). p. 17.
- ^ a b c "Liquid Hydrogen as a Propulsion Fuel, 1945-1959". NASA. Archived from the original on 2017-12-25. Retrieved 2017-07-12.
- ISBN 0-201-14659-2
- ^ Brügge, Norbert. "Electron Propulsion". B14643.de. Archived from the original on 26 January 2018. Retrieved 20 September 2016.
- ^ Wu, Yulin, et al. Vibration of hydraulic machinery. Berlin: Springer, 2013.
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
- Book of Rocket Propulsion
- M. L. "Joe" Stangeland (Summer 1988). "Turbopumps for Liquid Rocket Engines". Threshold – Engineering Journal of Power Technology. Rocketdyne. Archived from the original on 2009-09-24.