激波风洞中高超声速进气道起动特性及其检测方法研究

The ability to accurately predict the hypersonic inlet starting characteristics is still lacking. The hypersonic inlet starting characteristics, testing methods and the involved flow features are studied in the present project. Simultaneous high speed schlieren imaging and surface pressure measurements are applied to capture the unsteady flows of hypersonic inlet in a shock tunnel. The mechanisms of the hypersonic inlet starting characteristics are discussed with a combination of experiments and Computational Fluid Dynamics. Through this research, advanced numerical method and analytical model will be proposed to thoroughly study the unsteady waves in the nozzle starting process of the shock tunnel. Then the unsteady waves will be reasonably simplified to establish the mechanisms of the inlet pulse-starting in the shock tunnel. Moreover, some new testing methods of inlet self-starting ability will be developed by suppressing the inlet pulse-starting characteristics in the shock tunnel, such as increasing the initial pressure of the test chamber, presetting a light-weight obstacle, using a fast-response gas injection technique to choke the inlet. The key factors and the flow features of each testing method will be obtained. The capability of shock tunnels will be extended to investigate various flows in the hypersonic inlet which is essential for us to understand the physical mechanisms of hypersonic inlet starting characteristics and to predict inlet un-starting. The present research is meaningful not only to the scientific community but also to the engineering applications.

针对高超声速进气道起动特性准确和全面预报上仍然面临挑战，本项目以进气道起动特性、检测方法及流场波系结构为主要关注点，以激波风洞为实验平台，高速纹影拍摄同步壁面压强测量为主要观测技术，并结合数值模拟，通过细致分析并合理简化激波风洞喷管非定常起动过程的波系结构，获得喷管起动波系影响进气道脉冲起动的规律。在此基础上，合理地抑制或利用进气道脉冲起动，发展升高实验段初始压强、预先设置轻质堵块、快速响应的喷流技术等多种实验方法，从多个方面检测进气道的起动特性，获得多种检测方法的影响因素和流动机理，评价其检测结果的可靠性。力求在进气道脉冲起动机理方面获得新的认识，在进气道起动特性检测方法上取得新的突破，为拓展激波风洞在高超声速进气道研究领域的应用潜力和空间，提供基础性的概念、理论和技术支持。本项目对于揭示进气道起动/不起动的流动机理、预报进气道不起动，具有重要的学术价值和工程应用意义。

针对激波风洞与常规风洞中高超声速进气道起动特性的差异，以及在激波风洞短暂的实验时间内如何检测进气道自起动能力的问题，首先，通过数值模拟结合实验，揭示了激波风洞喷管起动波系影响进气道脉冲起动的机理，提出了简化喷管起动波系的“解耦”模拟方法，能够较为快捷和可靠地评估激波风洞中高超声速进气道的脉冲起动能力，推进了对激波风洞中进气道起动现象的认识，协调了与常规风洞的差异；在此基础上，验证了升高激波风洞实验段初始舱压检测进气道自起动能力的实验方法。然后，通过动网格数值模拟分析以及采用导轨约束堵块做准一维滑动的激波风洞实验，阐明了预先设置轻质堵块检测进气道自起动能力的流动机理及其主要影响因素，保障了堵块移动方式的重复性；依据堵块在检测过程起始阶段近似做匀加速运动所建立的堵块运动模型，能够合理预估堵块的堵塞时间，用于指导激波风洞实验选择合适的堵块。最后，通过设计并调节隔离段横向喷流的时序，在进气道起动后开启喷流，额外增加流量导致壅塞产生激波串，激波串的前传运动受到进气道及隔离段内背景波系的影响，及时关闭喷流使得进气道经历起动-不起动-再起动过程，能够用于检测其自起动能力；而预先开启喷流能够在不影响激波风洞喷管正常起动的情况下，造成进气道不起动，也可以用于检测进气道的自起动能力。本项目建立并掌握了升高实验段初始压强、预先设置轻质滑动堵块和隔离段横向喷流三种应用于激波风洞中高超声速进气道起动特性的快捷检测方法；在激波风洞实验条件允许的情况下，建议采用隔离段横向喷流检测方法，在一次实验中，不仅能够评估进气道的自起动能力，获得进气道起动时的实验数据，还能观测隔离段反压前传过程、喘振特性。本项目掌握的流动规律以及积累的实验方法和经验，拓展了激波风洞在高超声速进气道研究领域的应用潜力和空间，可以为高焓脉冲风洞中开展大尺度进气道起动性能实验，提供有价值的参考。