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喷注流强分布对高频纵向燃烧不稳定抑制效果研究

汪广旭1,谭永华2,庄逢辰3,陈建华1,杨宝娥4,洪流1   

  1. 1. 西安航天动力研究所
    2.
    3. 航天工程大学
    4. 西安航天动力研究所 液体火箭发动机技术重点实验室
  • 收稿日期:2021-06-25 修回日期:2021-09-27 出版日期:2021-10-09 发布日期:2021-10-09
  • 通讯作者: 汪广旭
  • 基金资助:
    装备预研重点实验室基金

Research on suppression effect of injection intensity distribution on high frequency longitudinal combustion instability

  • Received:2021-06-25 Revised:2021-09-27 Online:2021-10-09 Published:2021-10-09

摘要: 径向喷注流强分布被用在现役多个型号的常温自燃推进剂液体火箭发动机中,是这些发动机除声学阻尼装置以外最重要的燃烧不稳定工程抑制措施,但此类发动机仍然存在一定的燃烧不稳定风险,因此,仍需要对其抑制效果开展深入研究。采用独立喷注器思路,设计了采用撞击式喷注器的自燃推进剂模型燃烧室,在模型燃烧室内激发高频纵向燃烧不稳定的基础上,进一步开展了不同喷注流强分布方案下的高频纵向燃烧不稳定实验,并对喷注流强分布的抑制效果进行了分析和讨论。研究表明:对于液滴蒸发作为速率控制过程的情况,提高“驼峰区”流强分布能够改善模型燃烧室的高频纵向稳定性,但改善效果与燃烧特征长度的变化相对燃烧室长度的大小有关。相对于短燃烧室工况,长燃烧室工况下,由喷注流强分布引起的燃烧特征长度改变相对燃烧室长度的幅度降低,相应流强分布的抑制效果降低;相对于低室压工况,高室压下推进剂液滴蒸发过程加快,推进剂掺混效率提高,通过高流强区较大初始液滴粒径控制燃烧分布的效果被弱化,相应流强分布的抑制效果降低。各喷注器在高室压、长燃烧室工况下均激发了较大幅值振荡,且振幅分布与是否提高“驼峰区”流强无关。

关键词: 自燃推进剂, 液体火箭发动机, 喷注流强分布, 燃烧不稳定性, 抑制效果

Abstract: Radial Injection intensity distribution has been adopt in many liquid rocket engines using storable hypergolic propellants, which has been one of the most important suppression methodsof combustion instability in engineer for these engines, except for acoustic damping devices. However, these engines still confront with some risk of combustion instability, which means that deep study on its suppression effect is still necessary. With the idea of independent injector, a model combustion chamber with impingement injectors of hypergolic propellant was designed and experimental study on high frequency longitudinal combustion instability of different injection intensity distribution was conducted. It is indicated that, for the case that droplet evaporation act as the rate controled process, enhancing injection intensity of the ‘hump zone’ are able to improve the high frequency longitudinal combusiton stability, whereas the improvement effect is depend on the relative result of the variation of combustion characteristic length and chamber length. Compare with the short case, in the case with long combustion chamber, the relative result of the variation of combusiton characteristic length due to the change of injection intensity distribution and combusiton chamber length will be smaller, and the correspond suppression effect will be weakened. Compare with the lower pressure case, evaporation of propellant droplets will accerate in high pressure case and mixture efficiency will be improved. which means that the way to control combustion distribution through much bigger droplets in high intensity zone will be weakened and suppresion effect will be reduced at the same time. For the case with high chamber pressure and long chamber length, high amplitude pressure oscillation is excited for each injector, and distribution of amplitudes has no relation with the injcetion intensity in hump zone.

Key words: hypergolic propellant, liquid rocket engine, injection intensity distribution, combustion instability, suppression effect