Study on Energy Balance at the Operating Points of Staged Combustion Cycle LRE

In the present research, liquid rocket engine (LRE) balancing was performed at the design and the off-design points to confirm the characteristics for a 9-tonf staged combustion cycle LRE whose propellant consists of LOx/kerosene. When an LRE is designed, basic specifications, such as combustion pressure and O / F ratio, are predetermined and the corresponding balancing values are decided. Nevertheless, an engine may run over a nominal point in actual operation. Thrust control valve (THCV) and O / F ratio control valve (OFCV) are activated to adjust the engine status in real operation whenever an engine runs out of the design point. The engine power balancing requires thermophysical properties of the LOx and the kerosene for the combustion process and those were adopted from the CEA, which is an open-source code written by NASA. Also, MATLAB was employed and symbolic generation and numeric calculation was proposed to help set up the governing system and to reduce computational load. The off-design points were suggested to be set at ± 7%, ± 5%, ± 3% variance range from the nominal combustion pressure and the O / F ratio. It has been derived from the results that the required power of the pump was greatest at OD3 while least at OD1. If the combustion pressure is higher than DP, the THCV pressure difference should be set lower than DP. If the O / F ratio is higher than DP, the OFCV pressure difference should be set higher than DP. When the combustion pressure is over 100 bar, the TIT is over 700 K. It should be taken carefully in this section for turbine safety.