System performance tests and start transient analysis of a liquid rocket engine turbopump

This article describes a series of development tests of a turbopump, which can be applied to a gas generator cycle rocket engine with liquid oxygen and kerosene propellants. A turbine drives both an oxidizer pump and a fuel pump in the turbopump assembly. In the tests, liquid oxygen and kerosene are supplied to the oxidizer pump and the fuel pump, respectively, while either cold hydrogen gas or hot gas from the gas generator is supplied to the turbine. The turbopump is operated reliably at both on-design and off-design conditions, meeting all the performance requirements. The test results are compared with those of the turbopump component tests, where model fluids are used, that is, water for the oxidizer pump and the fuel pump, and cold air for the turbine. The turbopump tests results agree well with the turbopump component test results. The speed buildup of the turbopump at start period is calculated when pressurized gas is used to initially spin the turbine. A differential equation which represents the torque balance between the turbine and the pumps is solved. The calculation shows a good agreement with the test result. When the mechanical loss of the turbopump is considered, a better estimation is obtained.