LAUSR

Abstract This paper presents the results of an experimental and theoretical study of the transient chilldown of liquid rocket engine using passive recirculation approach. Multiple terrestrial tests are conducted with LOX recirculation system, and thermal and flow data are measured under different prelaunch operations including propellant loading, parking, replenishing and tank pressurization. A numerical model is developed and well validated to help examine the performance dependency upon parameters such as LOX subcooling, ullage pressure, liquid level and reflux pattern. The results show that accompanied by flow pattern transition instabilities, LOX pump is chilled to around 100 K, mainly through film boiling, and meets the predetermined thermal requirements of rocket engine. The recirculation stabilizes at an average of 0.89 kg/s over parking stage. Subcooled replenishing dramatically reduces the flow rate by more than 50% but meanwhile leads to a 9 K decrease in the LOX pump temperature, while saturated scheme slightly enhances the recirculation rate but increases the hardware tempeture. Flow excursion occurs during tank pressurization and in top-reflux condition the flow rate nosedives to 0.1 kg/s, much severer than bottom-reflux condition.