The effect of fuel pretreatment on performance of pulse detonation rocket engines

For hypersonic potential-use pulse detonation rocket engines (PDREs), the detonation chamber must stand against the high intensity of waste heat by fuel active cooling which in turn preheats and promotes liquid hydrocarbon fuel to crack into lower-molecular-weight carbon alkenes. The purpose of this research was to study the beneficial effects of the fuel pretreatments on PDRE performance, which comprised preheating and adding additives. Firstly, five concentric-counter-flow heat exchangers based on active cooling were tested to investigate the effect of geometric dimension on the heating efficiency. The results showed that the optimum length and thickness of annular heat exchange section were 300. mm and 5. mm, respectively. The heating capacity of the heat exchanger based on active cooling was significant. Furthermore, the effects of heat exchanger on operation time duration of PDRE and atomization improving of liquid kerosene were then investigated. The results indicated that the operation time of PDRE were extended nearly three times and PDRE could be operated normally without fuel injector. The initiation time was a very important factor for the multi-cycle PDRE, which was the sum of ignition delay time and whole deflagration-to-detonation transition (DDT) run-up time; therefore, experiments were conducted to investigate the effects of the fuel preheating and adding additives on the detonation initiation time. The results demonstrated that with the aid of fuel preheating, the detonation initiation time for liquid kerosene was noticeably reduced and the operation time of PDRE was remarkably prolonged, a fully-developed detonation wave was achieved in the position away from igniter 8.33 times of the diameter of the detonation tube. By adding the additives to liquid kerosene, the detonation initiation time from 0.75. ms decreased to 0.34. ms and the detonability of fuel was dramatically improved.