发动机燃烧产生并经喷管加速形成超音速的喷焰，高温高压的喷焰会向空间辐射出 强烈的红外能量，这种喷焰的红外信号特征被广泛应用于火箭动力目标的探测、跟踪及识别。在稠密大气层内，燃气射流与大气相互掺混形成复燃效应，是一种高温湍流的多组分、多粒径耦合化学反应的两相流；在稀薄过渡流及高真空区，燃气射流呈现“羽流状”的多组分热力学非平衡的两相流动形态；跨流域的发动机喷焰/羽流，燃气的高温振-转跃迁而发射出特定波段的光辐射，稀疏粒子群的吸收、发射和散射效应，对其辐射的定量描述具有很强的工程意义。

本文以连续流域的发动机两相喷焰、稀薄流域的发动机两相羽流以及跨流域发动机非定常工作状态下的动态喷焰/羽流为研究对象，旨在建立一系列发动机喷焰/羽流涉及的从稠密连续流到稀薄自由分子流，从化学非平衡到热力学非平衡，从定常到非定常的流动与辐射计算模型与工具，并通过文献数据校验分析模型算法的适用性，研究了不同状态下发动机喷焰/羽流流动及辐射的演变过程。论文主要工作可以概括为如下四个方面：

（1）基于纳维尔-斯托克斯方程的多组分流动控制方程，引入多步详细化学反应机理模型描述多组分间的复燃效应，发展了适用于可压缩的稠密大气环境下气-固两相流能量方程，结合质量、动量方程，建立多组分燃气-多粒径的颗粒群的高温化学反应效应下喷焰流动计算模型；建立结合NASA-SP-3080数据库的多组分燃气的统计谱带方法，计算燃气的辐射物性参数，以稀疏粒子群描述喷焰的高温颗粒物，采用米散射方法描述多粒径的固体颗粒群吸收、发射和散射效应，结合视在光线法描述多组分、多粒径气-固两相喷焰的辐射传输效应。数值分析了不同化学反应机理对喷焰流动的影响，并校验了双向耦合气-固两相喷焰流动与辐射模型的正确性，数值研究了不同海拔高度下发动机两相喷焰流动与辐射变化规律，发展了一套基于正侧向辐射光谱数据快速解析计算其它视向角下数据方法，研究了发动机喷焰的红外辐射强度随视向角变化规律，为发动机喷焰红外辐射特性的工程应用提供了一种新的高效算法。

（2）发展了喷管内部及出口附近的二阶滑移边界的纳维尔-斯托克斯方程描述方法，建立轴对称多组分分子的直接模拟卡洛算法，在算法中计算多原子和双原子分子的平动能、转动能和振动能转化实现对非平衡羽流流动的准确计算，引入随机轨道颗粒模型计算多粒径离散相颗粒物流动特征，具备对喷管出口以及近过渡流、远场稀薄流的大尺度、非平衡两相羽流模拟能力；在此基础上，改进发展了多组分、两相的高真空羽流预估模型。利用文献数据校验了相关模型的适用性，数值研究了发动机总温、总压，自由来流密度、速度四个核心参数对稀薄环境下羽流流动的影响规律，发现利用分离波线结合自由来流激波线和射流激波线即可实现羽流无量纲化描述；数值研究了稀薄环境下多组分气-固两相羽流流动特征。

（3）在统计窄谱带模型及辐射传输过程中引入稀薄环境下燃气急剧膨胀致非平衡、组分分离效应直接蒙特卡洛描述，建立大尺度计算域内多组分分子的多温描述，修订燃气组分的光学厚度表征方法，推导了多组分非平衡温度及多粒径颗粒物温度状态下的辐射传输方程，发展了一套适用于稀薄环境下发动机羽流红外辐射计算代码，利用文献数据校验了模型的有效性，高空燃气羽流的稠密区，发展模型与统计谱带模型基本吻合，在稀薄效应显著的区域，如激波层区、羽流下游远场区等，本模型典型波段区间误差达40%。在此基础上，数值研究了发动机总温、总压，自由来流密度、速度四个核心参数对稀薄环境下羽流辐射的影响规律以及气-固两相羽流辐射特征。

（4）建立瞬态的稠密大气层内发动机多组分喷焰流动模型及瞬态的稀薄环境下发动机多组分羽流流动模型，数值研究了发动机喷管出口至形成稳定喷焰/羽流演变过程中动态的流动与辐射；针对发动机喷管出口的状态参数波动，数值研究了出口温度、出口压强以及出口流量恒定等状态下波动导致的发动机喷焰流动与辐射的波动与变化规律，研究了出口参数正态波动对应喷焰辐射波动规律；结合对数值算法、绕流场解析方法以及运动学方程提出了一种兼具流动仿真和辐射计算的方法，仿真分析了发动机级间分离过程计算中时间步长对时变分离间距的影响，证明此方法可以有效计算分离过程的运动，研究发现了发动机级间分离过程中红外辐射的增强效应。

The supersonic plume is formed by the combustion chamber and accelerated by the nozzle. The high temperature and pressure plume will radiate strong energy to the space. The infrared signal charcateristics of this plume are widely used in the detection, tracking and identification of rocket-powered targets. In the dense atmosphere, the jet and the ambient gas are mixed with each other to form a re-combustion effect, which is a two-phase flow of high temperature turbulent multi-component and multi-particle size coupled chemical reactions; In the lean transition flow and high vacuum region, the jet presents a "plume-like" multi-component thermodynamically non-equilibrium two-phase flow pattern; Under the condition of cross-flight domain, the plume of the rocket motor, the high temperature vibration-rotation transition of the gas emits radiation in a specific band, the absorption, emission and scattering effects of the sparse particle group, the quantitative description of its radiation has strong engineering significance.

The research objectives of this paper include the two-phase plume in continuous flow domain, the two-phase plume in lean flow domain, and unsteady effect of rocket motor plume in cross-flight domain. It aims to establish a series of computational models and tools for flow and radiation from dense continuous flow to thin free molecular flow, from chemical non-equilibrium to thermodynamic non-equilibrium, and from steady to unsteady flow in the rocket motor plume. The applicability of the model algorithm is verified and analyzed by the literature data, and the evolution process of the plume flow and radiation of the engine under different conditions is studied. The main work of this paper can be summarized into the following four aspects:

(1) A multi-component flow governing equation based on the Navier-Stokes equations, a multi-step detailed chemical reaction mechanism model is introduced to describe the afterburning effect between the multi-components, and a gas-solid two-phase system suitable for compressible dense atmosphere is developed. The phase flow energy equation, combined with the mass and momentum equations, establishes the calculation model of the plume flow under the high temperature chemical reaction effect of the multi-component gas and the multi-particle size particle group; establishes the statistics of the multi-component gas combined with the NASA-SP-3080 database The spectral band method calculates the radiative physical parameters of the gas, describes the high-temperature particles of the plume with the sparse particle group, uses the Mie scattering method to describe the absorption, emission and scattering effects of the solid particle group with multiple particle sizes, and combines the apparent ray method to describe the multi-component , Radiation transfer effect of multi-particle gas-solid two-phase plume. The effects of different chemical reaction mechanisms on the plume flow were numerically analyzed, and the correctness of the two-way coupled gas-solid two-phase plume flow and radiation model was verified. The two-phase plume flow and radiation of the engine at different altitudes were numerically studied. According to the changing law, a set of methods for fast analytical calculation of data at other viewing angles based on the positive and lateral radiation spectrum data were developed, and the variation law of the infrared radiation intensity of the engine plume with the viewing angle was studied. A new efficient algorithm is provided for the engineering application of the infrared radiation characteristics of engine plumes.

(2) The Navier-Stokes equations describing the second-order slip boundary inside the nozzle and near the outlet are developed. The Direct Simulation Monte Carlo algorithm for axisymmetric multicomponent molecules is established, and the translational energy, rotational energy and vibrational energy conversion of polyatomic and diatomic molecules are calculated in the algorithm to achieve accurate calculation of non-equilibrium plume flow. The random orbit particle model is introduced to calculate the flow characteristics of multi-diameter discrete-phase particles. It has the ability to simulate large-scale, non-equilibrium two-phase plumes at the nozzle outlet, near transitional flow, and far-field rarefied flow. On this basis, a multi-component, two-phase high-vacuum plume prediction model is improved and developed. The applicability of the relevant models was verified using literature data. The effects of four core parameters of engine total temperature, total pressure, free flow density and velocity on the plume flow in a rarefied environment were numerically studied. It is found that the dimensionless description of the plume can be achieved by combining the free-flowing shock line and the jet shock line with the separation wave line. The flow characteristics of a multicomponent gas-solid two-phase plume in a rarefied environment are numerically investigated.

(3) The non-equilibrium and component separation effects caused by the rapid expansion of gas in a rarefied environment are introduced into the statistical narrow-band model and the radiative transfer process. The Direct Simulation Monte Carlo description is used to establish a multi-temperature description of multi-component molecules in a large-scale computational domain. The optical thickness characterization method of gas components is revised, and the radiative transfer equations for multi-component non-equilibrium temperature and multi-size particle temperature state are deduced. A set of codes for calculating infrared radiation of engine plumes in rarefied environments is developed. The validity of the model is verified using literature data. In the dense area of the high-altitude gas plume, the development model is basically consistent with the statistical band model. In the area with significant rarefaction effect, such as the shock layer area and the far-field area downstream of the plume, the error in the typical band interval of this model is 40%. On this basis, the effects of the four core parameters of engine total temperature, total pressure, free flow density and velocity on the plume radiation in a rarefied environment and the characteristics of the gas-solid two-phase plume radiation were numerically studied.

(4) A transient multi-component plume flow model of an engine in a dense atmosphere and a transient multi-component plume flow model of an engine in a lean environment are established. The dynamic flow and radiation during the evolution from the engine nozzle outlet to the formation of a stable jet/plume are numerically investigated. Aiming at the fluctuation of the state parameters of the nozzle outlet of the engine, the fluctuation and variation of the plume flow and radiation of the engine caused by the fluctuation of the outlet temperature, the outlet pressure and the outlet flow rate are numerically studied. The normal fluctuation of the outlet parameter corresponds to the fluctuation law of the plume radiation. Combining the logarithmic algorithm, the analytical method of the surrounding flow field and the kinematic equation, a method combining flow simulation and radiation calculation is proposed. The effect of the time step on the time-varying separation distance in the calculation of the separation process between the engine stages is simulated and analyzed, and it is proved that this method can effectively calculate the motion of the separation process.