Jianling Li

Experimental Investigations on Detonation Initiation in a Kerosene-Oxygen Pulse Detonation Rocket Engine

A series of experiments was carried out on a pulse detonation rocket engine (PDRE) running on a liquid kerosene-oxygen mixture to investigate the indirect detonation initiation. The experiments investigating the effect of Shchelkin spiral on the deflagration-to-detonation transition (DDT) process demonstrated that all spirals were able to enhance flame acceleration to some extent, but successful DDT was achieved only when the length of spiral was increased to six times of the inner diameter of detonation tube (6D). For the model with the spiral length of 6D, the DDT run-up distance was about 0.5 m (10D) and the sum of ignition delay and DDT run-up time was around 0.6 ms, which only occupied 0.6% of the whole cycle (100 ms). It implied that ignition delay and DDT run-up time were not the key factors of limiting the increase of frequency in a kerosene/oxygen PDRE. In addition, an experiment on detonation initiation by a flame jet through an orifice plate was successfully conducted on the multi-cycle PDRE. For detonation tubes with the orifice plate mounted 10 cm and 20 cm away from the thrust wall, the DDT run-up distance obtained was approximately 0.30 m (6D) and 0.2 m (4D). Compared with the spiral configuration, the DDT run-up distance was shortened by 40% and 60% in the two cases, respectively. The results implied that a rapid initiation of detonation could be achieved in a shorter distance with the approach of the flame jet ignition.

Numerical Investigation on Multi-cycle Operation of Pulse Detonation Rocket Engine

In order to investigate the multi-cycle operation process of pulse detonation rocket engine (PDRE), estimate the propulsion performance and obtain the regulation of the control parameters for performance optimization, a one-dimensional unsteady performance analysis model of PDRE is established and a CFD code is developed. The AUSM scheme and the third-order TVD Runge-Kutta method are used for spatial and temporal discretization, respectively. Chemical kinetics is modelled by a one-progress-variable scheme. The stiffness is dealt with by using the Strang-splitting method and fully implicit method. Through the simulation of the PDRE utilizing stoichiometric hydrogen/oxygen as the detonative mixture and nitrogen as purge gas, it can be found that the flow field in the detonation tube is much more complicated in multi-cycle operation due to the coupling of each cycle, compared with in single-cycle operation. The effects of the duty cycle of the filling period on flow characteristics and propulsion performance are also investigated here. As the duty cycle of the filling period decreases, the average thrust reduces too, but all filled mixture based specific impulse and detonative mixture based specific impulse increase. However, if the duty cycle of filling is too small, the gas temperature at the exit of PDRE will significantly increase. The results suggest that appropriately reducing the valve duty cycle of filling to decrease detonative mixture filling length can improve the propulsion performance and make PDRE run in an economical way.

Experimental Investigations on Detonability Limits of Pulse Detonation Rocket Engine

The duty cycle for C|0H19/oxygen injection and time sequence for injection, mixing and ignition to produce two-phase, fully-developed detonations are investigated in a pulse detonation rocket engine (PDRE) model. The The PDRE test model is 25mm in inner diameter and 1.1m long. The solenoid valves are employed to control intermittent supplies of propellants and purge gas. The spark igniter has ignition energy of around 50mJ. The solenoid valves and igniter are controlled by a control system. Under some given supply conditions, the detonability limits in terms of injection duty cycle and the controlling method are obtained. From fundamental analysis, these factors influence the operation of PDRE essentially by appropriate equivalence ratio and mixing. The experimental results show that to gain reliable detonations, first of all, the injection duty cycles for Ci0H]g and oxygen should ensure sufficient filling and then the injection time phases and duty cycles should be kept as close as possible to attain effective mixing.