【作者】 潘丞雄；

【导师】 张靖周；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2013， 博士

【摘要】 武装直升机是以反坦克为主、兼顾对地火力支援和空战的武器平台，可作超低空机动飞行或悬停，正是由于其良好的机动性能，在小规模的局部冲突、小型化的局部战争以及国际反恐行动中将发挥越来越重要的作用。随着可见光、红外、微波和毫米波等各种探测和制导技术的不断应用，武装直升机在现代高科技战场环境中的生存力将受到越来越严重的威胁，其中，红外制导武器被认为对武装直升机构成最致命的威胁。其一，红外探测和制导方式具有无源特点，随着红外探测和制导水平的提高，基于红外特征信号的探测、制导系统更具备抗干扰和破坏能力；其二，红外辐射特征是装备热动力推进系统的武装直升机所固有的信号特征，随着涡轴发动机排气温度的升高，使得武装直升机的红外辐射特征更为强烈。因此，开展直升机红外辐射特征分析与抑制技术研究对提高武装直升机红外隐身能力具有重要的意义。本文的主要研究内容包含三个方面：在直升机红外辐射特征分析中，机身蒙皮和排气尾流的温度场对红外辐射特性的影响十分重要。由于直升机蒙皮的温度分布取决于蒙皮与机身内部热部件、以及蒙皮与环境之间的传热过程，影响其温度分布的因素十分复杂，譬如旋翼下洗气流、发动机舱的辐射换热、蒙皮与外部气流之间的对流换热、机身表面的太阳辐照等；同时，发动机排气喷流的流场也受到旋翼下洗气流的直接影响。因此要准确预测直升机表面的温度分布，必须耦合求解排气系统内部和旋翼下洗气流的流动与传热以及燃气与壁面、固壁之间的辐射换热、太阳辐射等过程。对此，本文结合直升机旋翼空气动力学理论，建立了旋翼下洗气流模型，获得了旋翼下洗流场的速度分布，利用用户模块(UDF)导入Fluent软件作为旋翼下洗气流的边界条件；同时，在直升机机身表面温度场建模中建立了太阳辐照模型。在此基础上，计算了直升机悬停状态下的流场，得到了排气系统的流场和温度场，同时对直升机蒙皮温度场及影响因素进行分析，对排气温度、蒙皮发射率和太阳辐射对直升机红外辐射强度的影响进行了分析。引射-混合器是红外抑制器的核心部件，为了减小发动机重量，提高气流掺混性能，短突扩波瓣存在较大的应用前景，但是波瓣扩张角过大会造成附面层流动的脱体从而削弱波瓣混合器的混合效果，同时还会增加流动损失，为此，本文开展了短突扩波瓣型混合器的流动分析研究，获得了流动分离与波瓣扩张角的关系，研究了在波瓣波峰处开设通气狭缝以及斜切对波瓣喷管的引射效果的影响，并揭示了其在引射型混合器和强迫型混合器中应用的差异及其物理机制；同时考虑到双级引射-混合器是一个值得探索的结构方案，为此，本文开展了双级引射-混合器的引射特性研究，揭示了混合管在敞开进口和受限进口方式下的气动特征差异。随着红外探测和制导技术的不断发展，红外成像探测和制导技术的应用，飞行器红外隐身与反隐身已呈现出在3~5m波段和8~14m波段范围的对抗趋势，而且多模复合制导技术的发展将对武装直升机8~14m红外隐身提出越来越高的要求。为此，本文针对与机身结构一体化设计的红外抑制器冷热气流引射掺混特性、热部件壁面强化冷却、隔热等技术手段进行数值模拟和模型试验研究；同时针对常规布局的红外抑制器，本文研究了直升机发动机舱通风冷却、加设辐射遮挡罩、排气管尾缘延伸遮挡以及敷设隔热层等方案对发动机舱舱表面温度分布以及整机红外辐射特性的影响，提出了一种可大幅降低直升机红外辐射特性的初步改进方案。更多还原

【Abstract】 Helicopters are platforms of battlefield force transferring and anti-tank missions. They also playimportant roles in air to ground fire covering and short distance air to air fights. Due to their highmaneuverability, helicopters are of increasing importance in local conflicts and counter terrorismmilitary actions in recent decades. Owing to their low-flying height and hovering-attitude, thehelicopters are subjected to serious threats from radio, infrared, visual, and aural detection andtracking. Among these threats, infrared detection and tracking is regarded as more crucial for thesurvivability of helicopter. Firstly, passive detection and tracking by infrared signature seekingmissiles is tactically superior to the active, for comparable detection range. The infrared seekers haveexploited techniques to passively acquire and intercept airborne targets, by detecting their infraredemitting energy. The rapid advances in processor and detector array technology have led to enhancedsensitivity, low noise, multi-spectral, and smart detection capabilities. On the other hand, the ratio ofpower to weight for the turbo-shaft engines mainly been equipped in the helicopters increasestremendously, the maximum temperature under the thermodynamic cycle of aero-engine boosts,resulting in the helicopter infrared signature augment intensively. Consequently, infrared signaturesuppression and analysis is an important issue associated with helicopter susceptibility.The present paper focusing on three aspects:It is known that the temperature distributions on the helicopter fuselage skin and in the exhaustplume have a direct impact on the modeling of helicopter infrared signature. Because the temperaturedistribution on fuselage skin is governed by heat transfer between skin and inner hot elements as wellas skin and outer surrounding, there are many factors affecting the temperature distribution, such asthe rotor downwash, heat radiation from engine casting, convective heat transfer between skin andcold air, solar irradiance on the skin, etc. On the other hand, the exhaust plume temperaturedistribution is seriously affected by the rotor downwash flow owing to the mixing action. To preciselysimulate temperature distribution on the helicopter airframe and in the exhaust plume, the effects ofrotor downwash and solar irradiance must be taken into consideration considered in three-dimensionalflow and heat transfer calculation in a coupled mode. In the present paper, rotor propelleraerodynamics is introduced to model rotor downwash velocity distribution. The modeled downwash isthen added into numerical process through user defined function (UDF) as the boundary condition for rotor plane. Solar radiation including direct and diffusive radiative heat flux is also modeled in thenumerical simulation process. Based on the present modeling method, the exhaust flowfield andhelicopter skin temperature are analyzed. The roles of exhaust temperature, skin emissivity, solarradiation heat flux in helicopter infrared radiation characteristics are revealed.Mixer-ejector is the key part of an infrared suppressor. Firstly, to minimize the engine weight andenhance mixing between primary and secondary flow, short lobed nozzle with a large lobed angle is apromising setup in future application. But once the lobed angle is too large, there will be boundarylayer detachment near the lobed wall thus produces flow separation in the lobed mixer-ejector andbrings in more pressure loss. In the present paper, a short lobed mixer-ejector with a large lobed angleis researched. The relationship between lobed angle and flow separation is revealed. Ventilation andscarfying treatments are then introduced on the lobed nozzle to suppress separation bubble, enhancemixing and pressure recovery. The difference of those treatments on lobed wall in both ejected andforced secondary flow boundary conditions are revealed. Secondary, considering that double-stagedmixer-ejector is a promising configuration the ejector development, a double-staged mixer-ejector isstudied in this thesis. The aero-dynamical difference between confined secondary flow and opensecondary flow inlet modes on double-staged mixer-ejector is illustrated.As the infrared detection and guidance technology development, infrared stealth and anti-stealthin both3~5m and8~14m wavebands are confronting each other for a helicopter in real battlefield.Detectors with both3~5m and8~14m wavebands detection and guidance capabilities have madehelicopter’s stealth requirements even higher. In the present paper, a numerical and experimental studyon the infrared suppressor integrating the exhaust system with the tail part of a helicopter has beenperformed to investigate the effects of ambient air pumping-mixing, radiative heat sheltering and rotordownwash on reducing the exhaust system temperature and diminishing the target infrared signature.And for the common engine exhaust system, some methods for suppressing infrared radiation areinvestigated, including nacelle ventilation, radiative shelter, heat resistance layer and mxing ductcovering. A preliminary optimum configuration for suppressing helicopter infrared signature ispresented.更多还原