火箭模态下高频爆震波的稳定产生与失效机制研究

In a pulse detonation engine, high-frequency detonations are beneficial to enhance the propulsive performance and reduce the unsteady characteristics. Previous studies indicate that high-frequency detonations can be obtained under either the simplified doubled-frequency scheme or the valveless scheme without the purge process. However, more reactive oxidizers are often utilized in rocket mode which makes it more difficult to produce high-frequency detonations. The situation is that both the two operating schemes are easier to be affected by the purge process and the boundary conditions, but the specific mechanisms are still not clarified. This study aims to investigate the primary factors which influence the production of high-frequency detonations, e.g., the purge process in the simplified doubled-frequency scheme and boundary conditions and mixture components under the valveless scheme without the purge process. It is hoped that the length to diameter ratio of the buffer zone and its critical value can be obtained when the simplified doubled-frequency scheme is adopted, which will reveal the criteria of how to produce high-frequency detonations. Moreover, the effects of boundary conditions and mixture components on the generation of detonations are expected to be clarified, which will be helpful for understanding the transition from steady generation of detonations to failures. In a word, the results of this study will provide theoretical foundations for taming these two methods to produce high-frequency detonations.

脉冲爆震发动机中，高频爆震波的产生有利于提高推进性能并降低其非稳态工作特性。研究表明，简化的电磁阀倍频和无阀、无隔离两种新型工作方式下，均可获得高频爆震波。然而，火箭模态工作时，氧化剂通常较为活泼，不利于爆震波的稳定产生。上述两种工作方式更易受到隔离过程、边界条件等因素的影响，且具体作用机制尚不明晰。本项目拟分别围绕有阀时的隔离过程、无阀时的边界条件和反应物组分等影响高频爆震波稳定产生的主要因素开展研究，给出有阀时隔离区长径比和临界值，揭示高频爆震波稳定产生的判定准则；基于点火过程可视化，明晰边界条件、反应物组分对高频爆震波产生的具体影响，阐明无阀时高频爆震波由稳定产生向失效演变的具体机制，为掌握两种高频爆震波产生方法提供理论支撑和参考。

提高爆震波的产生频率有利于提高脉冲爆震发动机的推进性能并降低其非稳态工作特性，但以火箭模态工作时，由于氧化剂较为活泼，在高频工况下极易发生爆震波产生失效。鉴于高频间歇式供给的要求，世界范围内实现高频爆震的工作方式主要包括机械阀门和无阀两种形式。研究表明，简化的电磁阀倍频和无阀、无隔离两种新型高频工作方式下，虽可获得高频爆震波，但也容易发生爆震波失效。本项目围绕上述两种工作方式开展了系统探索，研究了隔离过程、边界条件、反应物组分等不同因素对高频爆震波稳定产生的影响，揭示了高频爆震波的稳定产生和失效机制。. 简化的电磁阀倍频工作方式下，通过开展隔离过程对高频爆震波产生影响的研究，明确了爆震波由稳定产生向失效迁移的隔离区临界长径比；通过电磁阀对控制信号的响应和回爆波向上游的回传的研究，发现高频工作时并未形成理想隔离区，该工作方式下的高频爆震波产生机制与无阀模式是统一的，并可拓展到传统电磁阀和部分旋转阀控制模式，首次统一了各种有阀和无阀控制模式下的高频爆震波产生方式。. 无阀、无隔离工作方式下，研究了边界条件和反应物组分等因素对高频爆震波稳定产生的影响，阐明了该工作方式下可稳定产生高频爆震波的氧化剂浓度边界。通过点火过程的可视化，发现不合理的头部结构产生的回流区会导致非正常点火，阐明了突扩头部布局下高频爆震波产生失效的本质原因；基于改进头部结构设计，提出了爆震波高频稳定产生方法，将高频爆震波的稳定产生时间提高到无热防护措施时的极限水平，揭示了渐扩头部布局下高频爆震波的稳定产生向失效迁移的潜在演变机制。. 本项目取得的研究结果，为加深对高频爆震波产生的理解提供了实验数据和理论支撑，对发展长时间稳定工作的脉冲爆震动力装置具有重要的参考价值，对推动爆震燃烧的技术应用具有积极的科学意义。