基于推力矢量控制的气体二次喷射混合流场实验研究

介绍用于固体火箭发动机推力矢量控制的气体二次喷射实验装置及实验方法；研究了气体二次喷射中喷射位置、喷射角度、喷射孔形状、喷射马赫数、喷射流量等诸多参数对混合流场弓形激波的影响；并对实测的弓形激波半径与激波理论分析方法求得的激波半径进行了比较，二者激波斜率基本一致。     

次流喷射控制推力矢量喷管的流场数值模拟

为了探讨次流喷射控制二维推力矢量喷管的性能,用时间推进求解Ｎ－Ｓ方程的方法数值模拟了喷管的流场,数值格式用中心有限体积格式,借助于当地时间步长和隐式残差光顺技术加速收敛,得到了在不同二次喷流压力下推力矢量喷管内流场的变化特征。计算结果与实验结果比较有满意的一致性。研究表明,应用次流喷射控制主流流动可以实现较大的推力矢量转折,但是,二次喷流必须具有足够的压力值。     

收敛-扩张喷管中运用激波矢量控制法的计算研究

采用二阶TVD格式的有限体积法耦合RNG k-ε湍流模型和非平衡壁面函数求解二维守恒型雷诺平均N-S方程，数值模拟了运用激波矢量控制法的二维收敛一扩张喷管中的流动现象，很好的模拟出了由于次流喷射所产生的激波及上下壁面的压力分布，并将计算结果与国外的实验结果进行了对比。     

两种气动推力矢量技术的数值模拟研究

对两种收扩喷管推力矢量控制技术:激波矢量控制技术和喉部偏移控制技术,进行了流场计算和性能比较。本研究中,喷管进口至喉部几何型面固定,扩张段长度为定值,二次流喷射位置、角度保持不变,采用CFD数值模拟方法计算喷管膨胀比不同时的流场。从计算结果可以看出,喉部偏移控制技术适用于膨胀比小于1.5的收扩喷管,而激波矢量控制技术适用于膨胀比大于1.5的收扩喷管。喉部偏移控制技术的特点在于其可以限制喷管主流流量,影响主、次流流量比的主要因素为二次流与主流的总压比。     

激波诱导控制推力矢量喷管实验及数值计算

采用实验方法,通过在二元收敛-扩张喷管扩张段引入二次流喷射,开展了激波诱导控制的流体推力矢量技术研究.实验过程通过喷管上、下壁面压力测量及出口射流纹影观测,研究了主流压力、二次流喷射压力以及二次流喷嘴几何(缝或孔)对推力矢量喷管性能的影响.同时,结合数值计算方法,对各实验工况下的喷管流场进行数值模拟,获得了实验手段难以得到的流场数据和性能,对实验结果进行了辅助分析.初步研究结果表明:在给定的实验条件下,主流压力越高,喷管推力矢量角越小,同时推力系数越大;二次流压力越高,喷管推力矢量角越大,同时推力系数减小;同孔喷射相比,采用喷缝几何下的上壁面激波诱导分离点更趋于向上游移动,分离点后压升显著,射流穿透能力强,对主流的扰动强烈.      

跨音速喷管流动的数值模拟

数值方法采用的差分格式是具有高分辨率和快速稳定收敛性质的全变差衰减(TVD)格式。喷管壁面形状和反压可任意给定,对于典型轴对称与二维喷管(即壁面由收缩角为45°,扩张角为15°的两条直线用圆弧光滑连接而成。圆弧的无量纲半径等于0.625,其参考长度为喉道半宽),进行了有激波与无激波流动的数值模拟。计算结果与实验结果以及其他计算结果符合良好,此法可推广到非定常跨音速喷管流动的计算,并可用于工程中喷管设计。     

二次流喷射位置对流体推力矢量喷管气动性能影响的数值模拟

数值模拟了二次流喷射位置对基于激波控制的二维收-扩(2DCD)喷管的流体推力矢量气动性能,结果表明喷射位置对矢量角有较大影响,在喷管落压比NPR=4.5时,二次流喷射位置相对位于喷管发散段中部时,矢量角最大;在NPR≥7.2时,二次流喷射位置越靠近出口,矢量角越大.喷射位置对推力系数及流量系数的影响不大.      

锥型喷管过膨胀射流中激波后的参数研究

研究了在锥型喷管和理想喷管过膨胀射流中激波后的参数控制问题.通过采用УсковВ.Н所给出的微分动力学相容性条件,得到了激波后气动参数沿激波分布的计算方法.该方法所得到的计算结果与实验结果是一致的.这一方法可用于指导某些气动装置的设计.     

推力向量控制方案及计算

本文归纳推力向量控制的主要方案,着重介绍摆动喷管、流体二次喷射方案的计算思路和结果.摆动喷管中的流场计算要考虑导弹偏摆对所产生的惯性力的影响;所得壁面压力畸变图说明,它是一个三维流场.在摆动喷管设计中要将铰链力减至最小,流体二次喷射的侧向力通过“等效实体模型”,用爆炸波的解来计算.     

二次流喷射对喷管流场性能的影响

采用有限体积法求解二维守恒型雷诺平均N-S方程,数值模拟了单膨胀斜面喷管内外流场,研究了二次流喷射对单膨胀斜面喷管非设计状态性能的影响,给出了性能随喷射流量、喷射总压和喷射角度的变化规律。计算结果表明,在喷管下斜板尾缘进行二次流喷射可以提高喷管非设计状态性能,喷射流量和喷射角度是影响喷管性能提高的主要因素,并存在最优的喷射流量和喷射角度,喷射总压对喷管性能影响较小。     

Interaction of single-pulse laser energy with bow shock in hypersonic flow

Pressure sensing and schlieren imaging with high resolution and sensitivity are applied to the study of the interaction of single-pulse laser energy with bow shock at Mach 5. An Nd:YAG laser operated at 1.06 lm, 100 mJ pulse energy is used to break down the hypersonic flow in a shock tunnel. Three-dimensional Navier–Stokes equations are solved with an upwind scheme to simulate the interaction. The pressure at the stagnation point on the blunt body is measured and calculated to examine the pressure variation during the interaction. Schlieren imaging is used in conjunction with the calculated density gradients to examine the process of the interaction. The results show that the experimental pressure at the stagnation point on the blunt body and schlieren imaging fit well with the simulation. The pressure at the stagnation point on the blunt body will increase when the transmission shock approaches the blunt body and decrease with the formation of the rarefied wave. Bow shock is deformed during the interaction. Quasi-stationary waves are formed by high rate laser energy deposition to control the bow shock. The pressure and temperature at the stagnation point on the blunt body and the wave drag are reduced to 50%, 75% and 81% respectively according to the simulation. Schlieren imaging has provided important information for the investigation of the mechanism of the interaction.     

脉冲能量沉积对超声速射流/激波相互作用掺混的控制研究

为探究超声速射流掺混增强的有效控制方法,基于二维非稳态雷诺平均Navier-Stokes方程,研究了脉冲能量沉积对超声速射流与斜激波相互作用后增强掺混的控制机理和规律。宽度为5 mm的低密度平面射流同向完全膨胀射入马赫数为2.5的主流中,并与20°压缩斜面所产生的斜激波相互作用。在流场中引入脉冲能量沉积对射流掺混进行控制,并考虑射流马赫数、射流长度、能量沉积位置及激励频率对掺混效果的影响。对比激励流场与基础流场,结果表明:脉冲能量沉积的加入诱导射流形成大尺度涡结构,显著提高射流的掺混效果;能量沉积位置对于不同马赫数射流的掺混增强具有不同的控制效果;激励前后射流宽度的对比表明,脉冲能量沉积的无量纲激励频率在0.22附近时,可使得射流的掺混效果最佳。     

Investigation of hot jet on active control of oblique detonation waves

The hot jet injection is utilized to actively control the oblique detonation wave, such as initiating and stabilizing an oblique detonation wave at a desired position that is shorter than the length of induction zone, and adjust the height of the oblique detonation wave at the exit of combustor when the oblique detonation wave engine is working on off-design flight conditions. The fifth order Weighted Essentially Non-Oscillatory (WENO) scheme and a two-step reversible reaction mechanism of the stoichiometric H₂/Air are adopted in the simulations. With the help of hot jet injection, the transition from inert oblique shock wave to the oblique detonation wave immediately occurs near the position of hot jet injection, and consequently the length of combustor can be reduced. The angle of oblique detonation wave also decreases as the hot jet injection approaches the nose of wedge. Additionally, the height of the oblique detonation wave at the exit of combustor can be flexibly adjusted, and also depends on the injection position and the strength of the hot jet. If the velocity of the hot jet is too weak to directly trigger the overall oblique detonation wave at the position of injection, increasing the injection pressure will improve the strength of the hot jet and results in a successful transition.     

水下爆轰燃气泡形态与激波传播过程研究*(爆震专刊)

针对脉冲爆轰发动机在水下工作过程中形成的燃气射流问题,搭建了水下爆轰燃气实验系统,研究了第一个爆轰循环在水下的燃气泡发展变化过程。建立了基于气液两相双流体模型的脉冲爆轰发动机水下喷射模型,采用时-空守恒元和求解元方法,模拟了爆轰波退化为激波在水中的传播及衰减过程。研究结果表明：燃气泡前期受外界水环境阻滞作用呈现“豌豆状”形态,充分发展阶段气液交界面逐渐失稳,在达到最大尺寸后开始收缩并在中心轴线位置出现凸出的射流；水下爆轰燃气射流发展过程中同时存在脱离燃气泡的水中前导激波和管口燃气泡内的高压区两部分,水中前导激波在传播过程中压力迅速衰减至常压量级,而管口燃气泡内则一直保持较高压力；中心轴线区域气液交界面处反射激波的回传使管口附近出现回击现象,并导致前导激波波阵面上压力峰值逐渐出现在30°方向上。     

A numerical study of segmented cooling-stream injection in supersonic film cooling

The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate, and numerically investigates the effect of segmented cooling-stream injection on supersonic film cooling. The results indicate that without shock-wave impingement and with helium as the coolant, segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection, especially at larger coo...     

Trailing-edge shock loss control with self-sustaining synthetic jet in a supersonic compressor cascade

To effectively reduce the loss of strong shock wave at the trailing edge of the supersonic cascade under high backpressure, a shock wave control method based on self-sustaining synthetic jet was proposed. The self-sustaining synthetic jet was applied on the pressure side of the blade with the blow slot and the bleed slot arranged upstream and downstream of the trailing-edge shock,respectively. The flow control mechanism and effects of parameters were investigated by numerical simulation. The res...     

端壁吸/吹气对超声速压气机叶栅流场影响机理的对比研究

附面层吸/吹气是抑制流动分离、提高压气机叶片负荷的有效技术途径。针对超声速压气机叶栅内激波诱导的角区分离,分别采用多种不同的端壁吸/吹气方案对其进行流动控制,旨在探索端壁吸/吹气对激波干涉下角区分离的控制机理,并对比分析端壁吸/吹气对超声速压气机叶栅角区分离的控制效果。结果表明:在激波/端壁附面层干涉下,该超声速压气机叶栅内存在大范围的激波诱导角区分离,角区分离使得该超声速叶栅存在强三维效应,二维叶栅中的单正激波变为"斜激波+正激波"结构,叶中吸力面尾缘开式分离变为闭式分离;端壁吸气可有效抑制该超声速叶栅的角区分离,吸气后近端壁区损失系数大幅降低,最优端壁吸气缝方案的起始点与亚声速压气机叶栅相同,但端壁吸气后叶中的双激波结构变为单正激波结构,叶中流动分离增大;端壁吹气也可有效抑制角区分离,其控制效果略优于端壁吸气,其原因是吹气缝处的静压高于吸气缝,对激波的增强作用弱于端壁吸气;与端壁吸气方案不同的是,最优端壁吹气缝方案的起始点位于叶片前缘。     

煤油在超声速气流中非定常横向喷射的实验观察

本文目的是研究煤油在超声速气流中非定常横向喷射问题,并与静止和亚声速气流中的结果进行对比。改造普通油嘴并采用单次高压燃油喷射系统,得到不同延时的流场阴影照片。结果表明：在超声速气流中,射流柱破碎是由迎风面的表面波引起的,破碎点位于表面波的波谷。雾化过程过分四个区域。射流激波由近射流柱的迎风面,并在人壁反射,非定常喷射的波系演化复杂。煤油在亚声速气流中喷射,不存在射流激波,破碎点沿射流柱上移,穿透深     

导流角对激波聚焦起爆爆震的影响

为研究两级脉冲爆震发动机环形射流入口导流角对激波聚焦起爆爆震的影响,以H2/O2/N2混合气为介质,对不同导流角下激波聚焦起爆爆震的过程进行了数值模拟,并开展导流角对激波聚焦起爆爆震影响的冷态实验,共同揭示其影响规律。结果表明:导流角越大,射流碰撞压力和温度越高,碰撞时间提前,更容易起爆爆震,但激波聚焦时间在导流角大于11°时基本不变;导流角越大,凹面腔内气流振荡频率越大,凹面腔底部的动压幅值越小。      

Suppressing unsteady motion of shock wave by high-frequency plasma synthetic jet

Three Plasma Synthetic Jet Actuators (PSJA) under the high-frequency actuation are used to control the Shock Wave Boundary Layer Interaction (SWBLI), a high-speed schlieren image processing method based on spatial Fourier transform as well as snapshot proper orthogonal decomposition were used to study the control effect of high-frequency plasma synthetic jet on low-frequency unsteadiness of SWBLI. The analysis of the base flow shows that the separated shock wave actually has both large- and small-amplitude vibrations at low frequency. And the results revealed that the PSJA with an operating frequency of 2 kHz has the ability to reduce the energy of low-frequency component of shock wave motion, indicating that the 2 kHz actuation can effectively suppress low-frequency unsteadiness of the separated wave. Compared with the actuation frequency of 2 kHz, the energy of low-frequency component of the shock wave is enhanced under the 8 kHz actuation, which aggravates the low-frequency unsteady motion of the shock wave. It is likely that the actuation frequency is too high, thus the intensity of the precursor shock wave induced by PSJA becomes weaker. Additionally, as the 4 kHz actuation is applied, the pulsation of the separation region was enhanced, it is speculated that the actuation frequency is coupled with the oscillation frequency of the separation region.