高超声速激波风洞研究进展

回顾了高超声速激波风洞的研制与发展,并依据高超声速实验研究对地面实验模拟技术的要求,分别介绍了应用轻气体、自由活塞和爆轰驱动技术研制的主要激波风洞的性能、特点和存在问题.重点介绍了爆轰驱动高焓激波风洞的3种主要运行模式:反向、正向爆轰驱动与双爆轰驱动. 根据这些运行模式的工作原理,分析了应用这些驱动技术产生的高温、高压气源的特点,探讨了不同驱动技术可能影响激波风洞性能的关键问题与解决方法.目前发展的激波风洞已经能够用于开展马赫数3$\sim$30的高超声速流动的试验模拟研究,但是试验气流的品质还不能满足高超声速科技研究的需求.为了获得可靠的实验结果, 通过不断改进、完善、提高激波风洞的性能,尽可能复现高超声速飞行条件是今后主要的研究方向.      

自由活塞压缩管ALE方法数值模拟

当前国际上实现高焓气体流动的实验手段之一是自由活塞驱动类脉冲设备,包括自由活塞激波风洞和自由活塞膨胀管.采用自由活塞压缩管作为激波风洞和膨胀管的驱动段时,其驱动能力在很大程度上决定了该类设备的性能.本文采用计算流体力学中任意拉格朗日——欧拉方法(arbitrary Lagrangian Eulerian)数值模拟了压缩管内部的自由活塞运动和气体流动特征.采用移动网格技术来适应活塞运动边界,耦合求解网格运动和气体流动过程,并通过双时间步长方法进行流体运动的时间积分.为了满足几何守恒律(geometric conservation law),对移动网格的法向矢量和表面面积计算进行了修正.不同时刻的活塞位置试验测量结果及欧拉方法预测结果,以及基于简单波理论获得的运动活塞底部气体压力、活塞速度与活塞位置都与当前的ALE方法十分一致.该工作为下一步数值模拟自由活塞激波风洞和自由活塞膨胀管中包括压缩管、激波管和喷管等不同部位的耦合流动提供了基础.      

长试验时间爆轰驱动激波风洞技术研究

地面试验是先进高超声速飞行器研制的主要手段之一,获得满足高超声速气动实验研究的长时间高焓气流是发展激波风洞技术的关键难题之一.依据反向爆轰驱动方法,针对满足超燃试验有效时间的要求,讨论了爆轰驱动激波风洞运行缝合条件匹配、喷管起动激波干扰控制和激波管末端激波边界层相互作用等因素对激波风洞试验时间的制约及其相应的解决方法.应用这些延长试验时间的激波风洞创新技术,成功研制了基于反向爆轰驱动方法的超大型激波风洞,试验时间长达100ms,并有复现高超声速飞行条件的流动模拟能力.      

高超声速点泉流场中的气动力

高超声速点泉流场是一种典型的非均匀来流流场。很多高速高焓地面实验设备,如具有锥型喷管的激波管风洞、炮风洞、电弧风洞等,其流场均具有高超声速球型膨胀的点泉流动特征。某些外部绕流也是如此。我们要用简便而正确的解析方法确定这种非均匀来流中物体的气动力,分析非均匀来流对压力分布及各种气动特性的影响。已有的一些     

高超声速喷管设计理论与方法

在高超声速飞行技术领域, 特别是涉及到高焓气体流动的研究, 高超声速风洞试验仍然是目前最可靠的研究手段. 风洞流场的品质是高超声速风洞研发最重要的一项性能指标, 其取决于喷管设计采用的理论与方法, 也是风洞设计最关注的一项核心技术. 针对二维轴对称型面喷管设计, 本文首先综述了传统高超声速喷管设计的主要理论和常用方法, 它们在高超声速喷管设计中曾经发挥了重要作用, 包括理论方法, 近似方法和基于两者的修正方法. 然后, 考虑高温气体效应, 分析了高焓喷管设计时面临的困难与问题, 从流动介质物性变化、高温边界层发展和非平衡过程效应三方面, 综述了国内外在高超声速高焓喷管设计方面的研究进展. 最后, 对于高焓喷管的设计理论和方法的发展作了展望, 期望对于推动我国高超声速高焓喷管设计技术的发展提供一些有意义的启示.      

高超声速飞行复现风洞理论与方法

针对高超声速飞行伴随的热化学反应流动,本文回顾了郭永怀先生的科研理念和学科布局,综述了他亲手成立的高温气动团队在高超声速飞行风洞实验模拟理论与方法方面的研究进展.高温气体的迅速产生与迅速应用是一种理想的风洞运行方法,而激波管就是这样一种实验装备.论文首先介绍了激波管技术的基本理论与方程,指出将其用于高超声速流动实验模拟时所具有的独特优势.然后讨论了应用激波风洞复现需要的高超声速飞行状态的可行性、基本方程和需要解决的关键问题.针对这些关键问题,进一步介绍了如何应用爆轰现象研发激波风洞驱动技术的理论,并给出了基于爆轰驱动方法的技术发展和工程应用验证.最后,论文介绍了爆轰驱动激波风洞的界面匹配条件,该条件奠定了长实验时间激波风洞运行基础,是其他驱动方法尝试解决而没能完全解决的难题.高温气动团队关于高超声速飞行复现风洞的理论与技术研究,实现了郭永怀先生的战略规划,成就了国际领先的高超声速热化学反应流动研究平台.      

高超声速飞行复现风洞理论与方法

针对高超声速飞行伴随的热化学反应流动,本文回顾了郭永怀先生的科研理念和学科布局,综述了他亲手成立的高温气动团队在高超声速飞行风洞实验模拟理论与方法方面的研究进展.高温气体的迅速产生与迅速应用是一种理想的风洞运行方法,而激波管就是这样一种实验装备.论文首先介绍了激波管技术的基本理论与方程,指出将其用于高超声速流动实验模拟时所具有的独特优势.然后讨论了应用激波风洞复现需要的高超声速飞行状态的可行性、基本方程和需要解决的关键问题.针对这些关键问题,进一步介绍了如何应用爆轰现象研发激波风洞驱动技术的理论,并给出了基于爆轰驱动方法的技术发展和工程应用验证.最后,论文介绍了爆轰驱动激波风洞的界面匹配条件,该条件奠定了长实验时间激波风洞运行基础,是其他驱动方法尝试解决而没能完全解决的难题.高温气动团队关于高超声速飞行复现风洞的理论与技术研究,实现了郭永怀先生的战略规划,成就了国际领先的高超声速热化学反应流动研究平台.     

高焓湍流边界层壁面摩阻产生机制分析

高超飞行器在中低空以极高马赫数飞行时,飞行器表面会遇到湍流与高温非平衡效应耦合作用的新问题.这种高焓湍流边界层壁面摩阻产生机制是新型高超声速飞行器所关注的基础科学问题,厘清此产生机制可以为减阻方法的设计提供指导,具有重要的工程实用价值.本文选取高超声速飞行时楔形体头部斜激波后的高焓流动状态,开展了考虑高温非平衡效应的湍...     

高超声速高焓边界层稳定性与转捩研究进展

边界层由层流向湍流的转捩是高超声速飞行器设计面临的重大空气动力学问题. 随着飞行速域与空域的不断拓展, 高超声速高焓边界层中的高温气体效应会使得量热完全气体假设失效, 从而深刻影响流动转捩过程. 相关研究涉及多个学科, 是典型的多物理场耦合问题. 近年来, 随着相关飞行器技术的快速发展, 高超声速高焓边界层转捩问题的重要性越来越得到体现, 相关研究已成为国际上的热点领域. 本文综述相关研究进展, 首先介绍目前常用的高温气体物理模型, 尤其关注热化学非平衡模型, 并介绍激波捕捉、激波装配和边界层方程解等常用的高焓流动求解方法, 以及相关风洞和飞行试验技术的进展. 然后综述高温气体效应对转捩过程中的感受性、模态增长、瞬态增长和非线性作用等的影响的相关研究, 其中流向不稳定性中出现较大增长率的第三模态和超声速模态引起了广泛的研究兴趣. 最后进行总结, 并对未来发展略作展望.      

基于深度学习技术的激波风洞智能测力系统研究

高焓条件气动力测量试验对高超声速飞行器气动外形设计和优化起决定性作用. 通常采用脉冲风洞(如激波风洞)产生高温、高压驱动气体以模拟高超声速高焓试验气流. 在脉冲风洞对高超飞行器模型进行测力试验时, 测力天平输出信号结果无法摆脱惯性载荷的干扰影响, 其导致的测力模型低频振动问题基本无法通过滤波彻底解决, 尤其对试验时间只有几毫秒的情况, 六分量测力天平的结构设计研究受到了极大挑战. 因此, 对实现短试验时间条件高性能测力的深入研究发现, 天平动态校准凸显重要性和必要性. 本研究提出一种新的基于人工智能深度学习技术的单矢量动态自校准方法和智能测力系统概念, 并应用于目前激波风洞测力试验中. 该动校方法的最主要特点之一是对整体测力系统的校准, 而非仅仅针对天平, 并且保证校准的测力系统即为风洞试验对象, 确保校准与应用的一致性. 在测试评估中, 测试样本和风洞试验验证均得到了较为理想的效果, 大幅度低频振动干扰基本被消除, 脉冲风洞测力的精度和可靠性得到了大幅提高.      

An experimental investigation of hypervelocity flow in a conical nozzle

The flow in a conical nozzle is examined experimentally for a range of hypervelocity conditions in a free-piston shock tunnel. The pitot pressure levels compare reasonably well with an inviscid numerical prediction which includes a correction for the growth of the nozzle wall boundary layer. The size of the nozzle wall boundary layer seems to be well predicted by semi-empirical expressions developed for perfect gas flows, as do data from other free-piston shock tunnels.     

PLIF thermometry in shock tunnel flows using a Raman-shifted tunable excimer laser

Planar laser-induced fluorescence is performed in a free-piston shock tunnel by using a Raman-shifted tunable excimer laser to excite nitric oxide molecules in the flow. Two different flowfields are examined to test the difficulties associated with applying the technique to shock tunnels: the bluff body flow produced by a 25 mm diameter cylinder; and the oblique shock and expansion fan produced by a 35° half-angle wedge. For the cylinder, the maximum flow enthalpy was limited to 4.1 MJ kg due to high flow luminosity which is produced by metallic contaminants in the flow. A reflective filter is used to reduce the influence of flow luminosity making these measurements feasible. Freestream temperature measurements are in excellent agreement with those predicted from numerical flow calculations. Large uncertainties were observed for the high-temperature post-shock results. Several higher enthalpy shots (14 MJ kg) were also performed with the wedge and showed an insignificant amount of contaminant emission. Received 5 June 1996 / Accepted 8 February 1998     

Turbulent spots in boundary layers in a free-piston shock-tunnel flow

In this paper, experiments to detect turbulent spots in the transitional boundary layers, formed on a flat plate in a free-piston shock tunnel flow, are reported. Experiments indicate that thin-film heat-transfer gauges are suitable for identifying turbulent-spot activity and can be used to identify parameters such as the convection rate of spots and the intermittency of turbulence.     

Mass spectrometric measurements of driver gas arrival in the T4 free-piston shock-tunnel

Available test time is an important issue for ground-based flow research, particularly for impulse facilities such as shock tunnels, where test times of the order of several ms are typical. The early contamination of the test flow by the driver gas in such tunnels restricts the test time. This paper reports measurements of the driver gas arrival time in the test section of the T4 free-piston shock-tunnel over the total enthalpy range 3–17 MJ/kg, using a time-of-flight mass spectrometer. The results confirm measurements made by previous investigators using a choked duct driver gas detector at these conditions, and extend the range of previous mass spectrometer measurements to that of 3–20 MJ/kg. Comparisons of the contamination behaviour of various piston-driven reflected shock tunnels are also made. PACS 07.75.th; 47.40.-x     

Modelling the complete operation of a free-piston shock tunnel for a low enthalpy condition

Only a limited number of free-stream flow properties can be measured in hypersonic impulse facilities at the nozzle exit. This poses challenges for experimenters when subsequently analysing experimental data obtained from these facilities. Typically in a reflected shock tunnel, a simple analysis that requires small amounts of computational resources is used to calculate quasi-steady gas properties. This simple analysis requires initial fill conditions and experimental measurements in analytical calculations of each major flow process, using forward coupling with minor corrections to include processes that are not directly modeled. However, this simplistic approach leads to an unknown level of discrepancy to the true flow properties. To explore the simple modelling techniques accuracy, this paper details the use of transient one and two-dimensional numerical simulations of a complete facility to obtain more refined free-stream flow properties from a free-piston reflected shock tunnel operating at low-enthalpy conditions. These calculations were verified by comparison to experimental data obtained from the facility. For the condition and facility investigated, the test conditions at nozzle exit produced with the simple modelling technique agree with the time and space averaged results from the complete facility calculations to within the accuracy of the experimental measurements.     

Measurement techniques in high-enthalpy hypersonic facilities

Interest in hypersonic aerodynamic braking and aerospace planes has led to the development of new high-enthalpy hypersonic test facilities. This paper describes available techniques and future developments for making measurements in these facilities. Emphasis is on instrumentation for use with short-duration flows in free-piston shock tunnels. Issues of free-stream calibration, surface measurements on models, flow visualization, laser diagnostics, and accuracy are addressed, with references made to representative experimental studies. The paper concludes with a summary of future research needs.     

Gaseous detonation driver for a shock tunnel

The concept of a shock tunnel with gaseous detonation driver is discussed. A detonation driver presents an alternative to a free-piston driver because comparable values of high enthalpy can be attained, however, without the fast movement of a heavy piston. Wave diagrams, pressure and temperature distributions are presented. Finally, first experimental results are given.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Dynamic calibration of force balances for impulse hypersonic facilities

This paper analyzes different techniques for the calibration of force balances for use in short-duration impulse hypersonic facilities such as shock tunnels. The background to how deconvolution can be used to infer aerodynamic forces on models in impulse hypersonic wind tunnels is presented along with the theory behind the different calibration techniques. Four calibration techniques are applied to a single-component stress-wave force balance. Experiments in the T4 shock tunnel using the balance demonstrate the suitability of the different calibrations for force measurements in an impulse facility. Cross checks between the calibration techniques are used to check their ranges of validity. It is shown that the impulse response derived from tests in which the model and force balance are suspended from a fine wire and the wire cut agree well with impulse responses derived from calibrations made using an impact hammer. The suitability of the balance for measuring dynamic forces is demonstrated by showing that the drag force on a model follows the history of Pitot pressure in the test section in the tunnel shots.Received: 17 May 2002, Accepted: 11 December 2002, Published online: 6 March 2003PACS: 47.40.Ki, 47.80.+v, 07.10.Pz