【作者】 吴继飞；

【导师】 范召林； 徐来武； 罗新福；

【作者基本信息】 中国空气动力研究与发展中心 ， 流体力学， 2012， 博士

【摘要】 与传统武器外挂模式相比，采用内埋式武器装载后，不仅使飞机的飞行阻力大大减小，同时还会降低其雷达反射面积，因此，武器内埋式装载已成为新一代飞行器武器装载的发展趋势。但武器内埋式装载同样带来许多新的空气动力学/气动声学问题：如舱门开启或武器投放瞬间可能产生较大的动态冲击载荷，从而影响飞行器飞行性能；对于某些几何布局的弹舱，其流场不利于武器安全分离，存在机/弹相互碰撞的危险；当武器舱暴露于高速气流中时，由流动引发的压力、密度以及速度的脉动，将在武器舱内部及周围产生强烈的气动噪声，从而引发结构振动并造成结构疲劳；处于复杂流场且快速运动的武器舱舱门可能发生振动及变形，严重时甚至存在舱门被撕裂或吹飞的危险。因此开展内埋武器舱系统气动特性研究具有重要意义。本文以静态压力测量、脉动压力测量以及网格测力等手段，在高速风洞中对内埋武器舱系统气动特性进行了较全面、深入的研究，研究内容分内埋弹舱流场稳态特性、内埋弹舱气动声学特性、内埋武器出舱段气动特性以及舱门开闭动态特性等四方面。本文研究了内埋弹舱流场稳态压力分布特性以及气动声学特性随各种参数的变化规律，并对弹舱流场演化机理以及气动噪声机制进行研究；采用了几种不同的流动控制措施对内埋弹舱流场进行控制，目的是降低弹舱流场压力梯度、抑制弹舱流场引发的强气动噪声；通过网格测力试验，得到了内埋武器出舱段的基本气动特性，在此基础上，研究了几种控制方法对内埋武器分离特性的改善效果。通过动态试验，获取了舱门开闭过程中的动态载荷，研究了舱门运动对舱内流场的影响，同时对舱门分布载荷以及集中载荷特性进行了研究。本文研究结果表明：弹舱长深比L/D、来流Ma数以及弹舱前缘边界层厚度与弹舱深度比δ/D等参数对舱内稳态压力分布影响明显，是决定弹舱流场类型的主要参数；随Ma数或δ/D增大，弹舱流场类型有向开式流动转变的趋势，而随L/D增大，弹舱流场类型逐渐演化成闭式流动。笔者认为：当L/D足够大时，弹舱前、后壁附近各有一个分离尾迹区，随L/D减小，弹舱前分离区在舱内逐渐占主导地位，而弹舱后分离区逐渐萎缩，直至被前分离区吞并，正是弹舱前、后分离尾迹区的变化导致了舱内压力分布的变化，进而使弹舱流场类型发生转变。弹舱基准流场类型不同时，采用弹舱后缘修型进行流动控制对弹舱流场稳态压力分布产生影响也不同；弹舱底部安装泄压管对平衡舱内压力梯度有一定作用；采用前缘立齿或前缘射流进行流动控制时，舱内稳态压力梯度降低，弹舱流场类型有向开式流动方向转变的趋势。本文针对弹舱流场气动声学特性方面的研究结果表明：与闭式弹舱流场相比，开式弹舱流场气动声学环境较恶劣，弹舱流场主噪声源附近总声压级可达170dB以上，声压频谱曲线上存在多个不同模态的单调声，单调声以及声压能量主要集中在St＜2.5范围内。笔者认为，弹舱前缘的剪切层在形成初期包含有多种扰动因子，在声辐射激励作用下，对应弹舱自然频率fn的扰动被放大，并形成K-H涡，弹舱后壁可看成是噪声放大器，气流在该处撞击形成强烈的压力脉动，诱发产生强气动噪声的同时并产生声辐射，声辐射传播到弹舱前缘时将对剪切层产生激励，在该激励作用下，对应弹舱自然频率的扰动因子被放大，从而再次产生K-H涡，形成弹舱流场自持振荡回路。采用边界层扰动法以及气流撞击削弱法进行流动控制后，舱内主噪声源附近总声压级强度均显著降低，声压频谱曲线上主模态单调声强度大幅削弱，弹舱流场气动声学环境明显改善；采用剪切层扰动法进行流动控制对弹舱流场气动声学特性的影响与马赫数关系密切，亚声速条件下，流动控制可导致弹舱流场气动声学环境更加恶劣，跨声速时，流动控制使弹舱流场气动声学环境明显改善；采用声传播回路阻碍法进行流动控制对弹舱流场气动声学环境改善效果不明显。本文针对舱内武器分离特性及其控制的研究结果表明：内埋武器出舱段气动特性主要受弹舱流场影响，与外挂武器相比，内埋武器分离过程中的气动力特性更为复杂，武器分离初期容易出现气动力波动，存在机/弹分离安全隐患；弹舱长深比L/D变化对内埋武器气动力特性影响明显，随L/D增大，武器模型将产生较大的抬头力矩，其横航向气动力波动加剧；弹舱后缘修型对武器模型气动力特性影响较小，弹舱底部安装泄压管可使武器出舱段气动力特性得到一定程度的改善；弹舱前缘主/被动流动控制均对武器气动力特性影响明显，武器模型纵向气动力特性均有较大程度改善，有利于机/弹分离安全。本文针对舱门开闭动态特性方面的研究结果表明：静态试验获得的舱内稳态压力数据与动态试验处理得到的压力直流量整体变化趋势一致，StD数变化对舱内压力直流量整体分布规律基本无影响。舱门关闭过程中舱内测点频谱曲线上出现能量尖峰的概率较大，StD数变化对舱内测点的脉动压力系数分布影响较明显，频谱曲线则表明随StD数增大，能量尖峰有减弱的趋势。舱门表面不同位置测点动态载荷变化规律可能存在较大差异，StD变化对舱门测点动态载荷特性影响明显，舱门关闭过程StD数对舱门测点动态载荷影响更为复杂。舱门法向力系数与铰链力矩系数变化规律一致，舱门运动可能对上述集中载荷产生明显影响，舱门开启过程可能引发较大的负向附加气动载荷，而舱门关闭过程则可能引发较强正向附加气动载荷；随Ma数增大，StD数对舱门集中载荷特性影响作用降低；超声速条件下，舱门法向力以及俯仰力矩曲线存在显著波动，舱门以较快速度运动时有利于降低该波动。更多还原

【Abstract】 Compared with the external carriage, the aircraft with internal carriage of storeshas lower drag and radar cross section, so the new generation fighter is tended todesign with internal weapons-bay. But there are also some new aerodynamic andaero-acoustic issues accompanied with the internal weapons-bay. The dynamic load isvery big during a weapon is releasing, and which may effects on the fly performance ofthe plane. The disadvantage separation characteristics of the store may result incollision with the parent aircraft. The strong noise generated by the unsteady pressure,density and velocity around the weapons-bay may result in structure vibration, fatigueand safety of the aircraft at high speed for certain weapons-bay geometries. The doorsof the weapons-bay also may vibrate, distort and even been broken when they aremoving rapidly in the complicated weapons-bay flow field. Therefore, theinvestigation on aerodynamic characteristics of internal weapons-bay system is veryimportant.In this paper, investigations on aerodynamic characteristics of internalweapons-bay system were conducted in high speed wind tunnel in detail. Steadypressure measurement, fluctuation pressure measurement and grid measurement wereapplied in the study. The study is focused on the steady flow and aero-acousticcharacteristics of the weapons-bay, weapon’s separation characteristics and thedynamic characteristics of the doors’ movement. Steady pressure distributions andacoustic characteristics vary with different parameters of the weapons-bay werestudied in this paper. The mechanism of the cavity aerodynamic and aero-acousticcharacteristics was also discussed in the paper. Some flow control methods wereconducted to reduce the weapons-bay’s pressure gradient and suppress its strongaero-acoustic noise. The separation characteristics of an internal weapon were obtainedthrough grid measurement and the effects of some flow control methods on itsseparation characteristics were also evaluated. The dynamic pressure loads during theweapons-bay doors’ opening/closing processing were measured. The effect of door’smovement on weapons-bay’s flow was studied and the distributing and average loadson weapons-bay’s doors were discussed.The study shows that the type of weapons-bay’s flow based on the cavity floorsteady pressure distribution is mainly depended on the cavity length to depth ratio(L/D), Mach number (Ma) and the scaled boundary layer thickness (δ/D). Theweapons-bay flow transfers to open flow with the increasing of Ma or δ/D, but it willdevelop from open flow to closed flow with the increasing of L/D. In the author’sopinion, separation wake exists both close to the leading and rear wall of the cavity when the L/D is big enough, and the leading separation wake becomes dominantgradually with the decrease of L/D, while the rear separation wake becomes weakerand weaker and finally merges into the leading separation wake. The cavity floorpressure distribution varies with development of the leading and rear separation wakeand the cavity flow type changes accordingly. The effect of the rear wall modificationdepends on the cavity flow type. The floor pressure balance tubes can reduce the cavityfloor pressure gradient. The leading edge vertical saw-tooth fence and blowing bothcan reduce the cavity floor pressure gradient and the cavity flow tends to become openflow.The investigations on the cavity aero-acoustic indicated that the aero-acousticenvironment for an open flow cavity is much worse than a closed flow one and themaximum sound pressure level can reach more than170dB. Several tones of differentmodes can be found in the cavity sound pressure spectra and the tones and soundpressure energy mainly appear at St<2.5. In the authors’ opinion, the K-H vortices areformed when the disturbs which exist in the forming of the cavity leading edge shearlayer coincide with cavity inherent frequencies fnare amplified by the sound radiation.The cavity rear wall may serve as an amplifier and strong aero-acoustic noise will beinduced and the sound radiation will be formed by the strong pressure fluctuationemitted from the flow hitting on the cavity rear wall. The disturbs which coincide withcavity inherent frequencies also will be amplified by the driving of the sound radiationin the cavity shear layer when it transfers to the cavity leading edge and the K-Hvortices have been induced again. Thus a self-sustained oscillation is formed in acavity. The boundary layer interruption and rear wall modification can reduce the totalsound pressure level and the main tone of the cavity significantly and its aero-acousticenvironment can be improved greatly. The effect of the shear layer interruption on thecavity aero-acoustic characteristics is different at different Ma. The cavityaero-acoustic environment can be worse when the shear layer interruption is adopted atsubsonic speed but the reverse effect can be achieved at transonic speed. A blockage tothe sound travel loop has little effect on the cavity aero-acoustic environment.The results of the internal weapon’s aerodynamic characteristics and its controlsindicated that the separation characteristic of an internal weapon is much morecomplicated than an external weapon. The unsteady forces on the store at the initialseparation stage are harmful to the store safe separation. An internal weapon’sseparation characteristics are mainly depended on the cavity length to depth ratio (L/D).The store’s positive pitching moment increases with L/D and the fluctuations of thelateral forces are also increased. The modification of the cavity rear wall has littleeffect on the store’s aerodynamic characteristics. The cavity base pressure balancetubes can improve the store’s separation characteristics. The axial aerodynamic characteristics can be improved through cavity leading edge active/passive flowcontrols and they are helpful to the store separation.The dynamic experiment of weapons-bay doors’ movement showed that theaverage pressure data compared well with the static measurement data on the cavityfloor and almost the same at different StD. More tones may appear on a certain spectrawhen the doors are closing. StDplays an important role on the cavity floor fluctuatingpressure and the peak of the tones reduced with the increasing of StD. The dynamicloads on the doors’ surface are different at different positions. The dynamic loads maychange a lot at different StD, and especially during the doors’ closing process. Themovement of the doors also has great effect on the doors’ normal force and hingemoment. The opening process may produce additional negative aerodynamic loadswhile positive aerodynamic loads may arise during the doors’ closing process. Theeffect of StDon the doors’ average loads decreases with the increasing of Mach number.Faster movement of the door can reduce its unsteady normal force and pitchingmoment at supersonic speed.更多还原