Turbopump

A turbopump can refer to either of two types of pump.

Turbomolecular pumps are also called turbopumps and are used to obtain high vacuum.

Another type of turbopump is a pump in which the fluid is moved by the blades of a high-speed turbine. Turbopumps are used with rocket engines to provide pressure for the fuel and oxidizer to be injected into the combustion chamber. In general, a turbopump is used when it is infeasible to use a pressure-fed engine, which requires much stronger tanks to hold the fuel and oxidizer. This article describes only that type of pump.

Early Development

The initial breakthrough for turbopumps used in rocket motors occurred under Dr. Walter Thiel, during the development of the V2 in Germany. Prior to Dr. Thiel's work, pressurized tanks had been used. With the breakthrough in going with turbopumps, the power of the rocket motors was increased by an order of magnitude, and rocket motors became practical for lifting heavy loads.

Development from 1947 to 1949

The principal engineer for turbopump development was George Bosco. This was a new field for Aerojet, and 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. [51] Bosco subsequently used Singelmann's data in designing Aerojet's first hydrogen pump.

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.

By the end of 1948, Aerojet had designed, built, and tested a liquid hydrogen pump (15 cm diameter). Initially, it used ball bearings that were run clean and dry, because the low temperature made conventional lubrication impractical. The pump was first operated at low speeds to allow its parts to cool down to operating temperature. When temperature gauges showed that liquid hydrogen had reached the pump, an attempt was made to accelerate from 5000 to 35 000 revolutions per minute. The pump failed and examination of the pieces pointed to a failure of the bearing, as well as the impeller. After some testing, super-precision bearings, lubricated by oil that was atomized and directed by a stream of gaseous nitrogen, were used. On the next run, the bearings worked satisfactorily but the stresses were too great for the brazed impeller and it flew apart. A new one was made by milling from a solid block of aluminum. Time was running out, as the contract had less than six months to go. The next two runs with the new pump were a great disappointment; the instruments showed no significant flow or pressure rise. The problem was traced to the exit diffuser of the pump, which was too small and insufficiently cooled during the cool-down cycle so that it limited the flow. This was corrected by adding vent holes in the pump housing; the vents were opened during cool down and closed when the pump was cold. With this fix, two additional runs were made in March 1949 and both were successful. Flow rate and pressure were found to be in approximate agreement with theoretical predictions. The maximum pressure was 26 atmospheres and the flow was 0.25 kilogram per second.

External link

• Turbopumps for Liquid Rocket Engines (http://www.engineeringatboeing.com/articles/turbopump.jsp) – From Rocketdyne's Engineering Journal of Power Technology