无阀式脉冲爆震火箭发动机运行稳定性实验

Experiment on operation stability of valveless pulse detonation rocket engine

以无阀模式运行时,脉冲爆震火箭发动机可达到更高的运行频率,但容易出现连续燃烧、点火不成功以及运行频率与点火频率不一致等运行不稳定问题。为探索供给条件对运行稳定性的影响,采用乙烯为燃料、富氧空气为氧化剂,开展了实验研究,分析了氧化剂中氧气体积分数对运行稳定性的影响。结果表明,采用氧气体积分数分别为40%和66%的氧化剂时,当量比范围分别为1.2~1.7和0.8~2.3时才能产生稳定的爆震波;采用氧气体积分数66%的氧化剂时,可获得稳定爆震波的当量比范围较宽;稳定产生爆震波时,爆震管封闭端附近的压力振荡会向供给通道的上游传播,造成通道内介质的流动振荡,振荡频率与运行频率呈倍数关系;爆震波不稳定产生条件下,供给通道内的流动振荡表现为无规律的低频振荡,该振荡加剧了无阀无隔离模式运行的不稳定,故有必要在供给通道内加装压力反传抑制装置。

Despite the ability of the valveless scheme to produce high frequency detonations,the problems leading to unsteady operations such as deflagration,ignition failure,and discrepancy in frequencies of operation and ignition are not clear.To study the influence of supply conditions on steady operations of the pulse detonation rocket engine,experiments have been conducted based on the valveless mode.Ethylene and oxygen-enriched air have been utilized as fuel and oxidizer,respectively.Influence of the oxygen volume fraction on the operation stability has also been analyzed.The results indicate that steady detonations are available only when the equivalence ratio is within a proper range,i.e.,1.2-1.7 and 0.8-2.3,when the oxygen volume fractions of 40% and 66% are used,respectively.The range of the equivalence ratio increases for producing detonation when the oxidizer with the volume fraction of 66%is used.In addition,pressure oscillations near the closed end of the detonation tube will propagate upwards to the supply passages when fully-developed detonations are produced,and thus flow oscillations,with a frequency times of the detonation frequency,will be induced inside the supply passages.However,the flow oscillations appear disorderly if steady detonations are not obtained in the detonation tube.Since the disorderly flow oscillations inside the supply passages will further influence the operation stability,measures to control them should be considered.