【作者】 王惠；

【导师】 范志刚；

【作者基本信息】 哈尔滨工业大学 ， 光学工程， 2021， 博士

【摘要】 在气动热环境中,当带有红外制导装置的飞行器高速飞行时,其前方的光学头罩温度迅速提升。由于受热不均匀,光学头罩的温度和折射率为非均匀分布。当一束平行光束通过折射率呈非均匀分布的流场和光学头罩时,其传播方向发生改变,增加了附加的相位。被探测器接收到的目标图像出现模糊、抖动、和像偏移。这种现象被称为气动光传输效应。同时气动加热的光学头罩发出强烈的红外辐射光束。红外辐射光束通过红外导引头后方的光学系统被探测器所接收,在探测器上对目标信号造成背景噪声干扰。光学头罩发出的红外辐射强烈时,探测器将达到饱和,目标图像信息被红外噪声淹没。这种现象被称为气动热辐射效应。气动光传输效应和气动热辐射效应统称为气动光学效应。气动光学效应影响红外导引头对目标的探测、识别、跟踪的能力,严重制约着导引头的制导精度。本文重点研究了光学头罩的气动光传输效应和气动热辐射效应的机理和建模仿真方法、建立了光学头罩的综合性能评价函数用于设计优化头罩的外形、构建了流场和光学侧窗的联合光传输数学计算模型去校正气动光学效应,主要研究内容包括:气动热环境下光学头罩的三维折射率场研究。根据空气动力学理论,利用有限元方法建立外流场的有限元计算模型。利用该计算模型仿真模拟飞行器高速飞行时,光学头罩外部流场真实的气动热环境,计算得到了流场的温度场、压强场、以及热流密度场分布。根据传热学以及结构力学理论,建立光学头罩的热分析有限元计算数学模型。利用该模型计算了气动热环境下,光学头罩的三维温度场分布,以及形变场分布规律。根据晶体的热光效应原理,光学头罩的折射率场分布可由温度场计算得到。光学头罩的光传输效应以及热辐射效应研究。在非均匀折射率场分布的光学介质中,通过仿真分析比较了三种光线追迹算法的追迹精度。建立了光学头罩的气动光传输效应和气动热辐射效应的数学计算模型,仿真得到了光学头罩的气动光学效应对高速飞行器成像质量的影响规律。光学头罩的气动光学效应影响因素研究。以共形光学头罩为研究对象,以空气动力学性能、成像质量以及辐射噪声为评价准则,计算了光学头罩的结构参数以及飞行工况对气动光学效应的影响规律。与传统的半球形光学头罩相比,在相同工况下共形头罩具有更好的空气动力学性能,然而受气动光学效应影响,共形头罩的失真图像更加模糊。通过增加光学头罩的厚度可以减小光学头罩的温度,进而提高受气动光传输效应和气动热辐射效应影响综合影响下高速飞行器的成像质量。为校正气动光学效应提供了一种新的方法。以归一化的阻力系数、波像差和辐照度随光学头罩的二次项系数的变化规律为依据建立光学头罩的综合性能评价函数,为光学头罩的选型和优化提供了一种新的依据。获得了飞行参数对气动光学效应的影响规律,为合理规划光学头罩成像制导路径提供了依据。流场和光学侧窗联合气动光传输效应研究。切向喷流冷却是一种常用的降低光学侧窗温度的方法。当制冷气体喷射时,流场的结构以及光学侧窗的温度分布将变的更加复杂。建立了适用于流场和任意形状的光学侧窗的联合气动光传输效应数学模型,对该计算模型进行了精度验证。通过建立的数学模型,仿真计算了采用喷流制冷校正气动光学效应后,高速飞行器的成像质量。结果表明气动热辐射效应与光学侧窗的温度有关,喷流制冷可以有效的降低光学侧窗的温度,从而减弱气动热辐射效应对成像质量的影响。而气动光传输效应与光线传播的光程差有关。喷射的制冷气体可能导致流场和光学侧窗的折射率梯度增大,光线通过流场和光学侧窗后光程差增大,进而导致气动光传输效应对成像质量的影响增强,图像退化更加严重。更多还原

【Abstract】 In the aerodynamic thermal environment,the temperature of an optical dome rises rapidly when an aircraft with infrared guidance device is flying at high speed.Due to the uneven heating,the temperature and refractive index of the optical dome is unevenly.When the parallel beam passes through the flow field and optical dome with the non-uniform refractive index distribution,its propagation direction will change and additional phase will be added.The target image received by the detector appears blur,jitter and image offset.This phenomenon is known as aero-optical transmission effect.Meanwhile,infrared radiation rays will be emitted from the aerodynamic heated optical dome.The infrared radiation rays are received by the detector behind the optical dome,causing background noise interference to the target signal on the detector.When the infrared radiation from the optical dome is strong,the detector will reach saturation and the target image will be submerged by infrared noise.This phenomenon is known as aero-thermal radiation effect.Aero-optical transmission effect and aero-thermal radiation effect are collectively referred to as aero-optical effect.The aero-optical effect affects the ability of the infrared seeker to detect,identify and track the target,and restricts the guidance accuracy of the seeker seriously.The thesis focuses on the theory and simulation method of aero-optical transmission effect and aero-thermal radiation effect of optical dome.The comprehensive performance evaluation function of the optical dome is established to optimize its shape.Under the film cooling condition,the combined optical transmission model of the flow field and the optical window is established to correct the aero-optical effect,the main research contents include:Research on three dimensional refractive index field of optical dome in aero-thermal environment.According to the theory of aerodynamics,the finite element model of the flow field is established by adopting the finite element method.The real aerodynamic thermal environment of the flow field outside the optical window is simulated.The temperature field,pressure field and heat flux field distribution of the flow field is calculated.According to the theory of heat transfer and structural mechanics,the thermal and structure coupling finite element model of optical dome is established.The three-dimensional temperature field distribution and deformation distribution of the optical dome in the aero-thermal environment is calculated.According to the principle of thermo-optic effect,the refractive index distribution can be calculated from the temperature distribution of an optical dome.Research on the aero-optical transmission effect and the aero-thermal radiation effect of the optical dome.The tracking accuracy of three ray tracing algorithms(Taylor series expansion method,three order Runge-Kutta method and four order Runge-Kutta method)is compared in optical media with non-uniform refractive index field distribution.The mathematical models of aero-optical transmission effect and the aero-thermal radiation effect of an optical dome is established respectively.The evaluation indexes of image quality degradation under the combined influence of the aero-optical transmission effect and the aero-thermal radiation effect are obtained.Research on the influence of flight parameters and structural parameters of an optical dome on aero-optical effect.Taking the conformal dome as the research object,and taking aerodynamic force,aerodynamic heat,optical image quality evaluation index and irradiance distribution as evaluation criteria,the influence of structural parameters of an optical dome and flight conditions on aero-optical effect is calculated.Compared with the traditional hemispherical optical dome,the conformal dome has better aerodynamic performance under the same flight conditions.However,the distortion image of the conformal dome is more blurred due to the influence of aero-optical effect.By increasing the thickness of the optical dome,its temperature can be reduced.Thus the imaging quality of the high-speed aircraft under the comprehensive influence of the aero-optical transmission effect and the aero-thermal radiation effect is improved.It provides a new kind of method to correct aero-optical effects.Based on the variation of normalized drag coefficient,wavefront aberration and irradiance with the quadratic term constant of an optical dome,the comprehensive performance evaluation function of the optical dome is established,which provides a new method for the design and optimization of optical dome.The influence law of the flight parameters on aero-optical effect is obtained,which provides the basis for reasonably planning imaging guidance path of optical dome.Research on combined aero-optical effect of the flow field and the optical window.Tangential film cooling is one of frequently-used methods to reduce the temperature of optical window.When the cooling gas is ejected,the structure of the flow field and the temperature distribution of the optical window will become more complex.The mathematical model of optical transmission effect combining flow field with optical side window is established,and the accuracy of the model is verified.This mathematical model is suitable for optical side window of arbitrary shape.The influence of aero-optical effect on image quality is calculated.The results show that the aerodynamic thermal radiation effect is related to the temperature of the optical window,and film cooling can effectively reduce the temperature of the optical window,so as to weaken the influence of aerodynamic thermal radiation effect on the image quality.The aero-optical transmission effect is related to the optical path of rays propagation.The ejected cooling gas may increase the refractive index gradient of the flow field and the optical window,and increase the optical path difference when the rays passes through the flow field and optical window,resulting in the influence of aero-optical transmission effect on the image quality enhancing,thus the image becoming more blurred.更多还原