【作者】 赵运生；

【导师】 胡骏；

【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】 气动稳定性已经成为当代航空发动机重要的战术和技术指标。设计良好的航空发动机，除了实现高性能和高可靠性之外，还要求在整个飞行包线范围内都必须有足够的可用稳定裕度。为此，在发动机研制周期的各个阶段，都需要进行气动稳定性分析，确保其可用稳定裕度大于总需用稳定裕度。影响发动机气动稳定性的因素有很多，外部因素主要有压力畸变、温度畸变、平面波、冲击波和雷诺数等，内部因素主要有加/减速、接通/断开加力、功率提取与附加引气、生产/装配偏差、部件老化、控制容差等。在发动机研制初始阶段，原则上不可能获得各种因素对气动稳定性影响的试验数据；整个研制过程中进行全飞行包线范围的试验成本也太高；对于地面或高空台设施不能进行的试验，也需要利用数值计算来代替。因此，气动稳定性分析中的数值计算方法受到了高度关注并被广泛的应用。为提升数值计算方法在航空发动机气动稳定性分析中的功能和适用范围，在分析各项降稳因子对发动机气动稳定性影响的机理基础上，建立和发展了相应的数学模型和求解方法，构建了功能完善的适用于发动机方案设计阶段和工程设计阶段的气动稳定性分析平台，并以某涡扇发动机为例，开展了全飞行包线范围的气动稳定性综合评估。本文的主要研究内容和结论可概括如下：（1）对发动机不同研制阶段的气动稳定性分析内容进行概括总结，分析了各项降稳因子对发动机气动稳定性影响的机理并进行合理归类；依据某涡扇发动机的技术任务，并参照国军标GJB/Z224-2005的评估要求，在飞行包线内确定了6个需要评估的典型状态和对应的降稳因子；利用补偿各个降稳因子的局部需用稳定裕度的统计规范值来预估发动机的总需用稳定裕度，完成了方案设计阶段的气动稳定性分析。（2）以部件匹配方法为基础，根据控制规律、限制参数和共同工作方程，建立了航空发动机稳态模型，并采用Newton-Raphson方法进行迭代求解；获得了典型状态下风扇和高压压气机的可用稳定裕度；通过将雷诺数修正模型、功率提取、附加引气模型、部件老化模型嵌入到稳态模型中，建立了可以分析雷诺数、功率提取、附加引气、部件老化对发动机气动稳定性影响的数学模型。计算结果表明，发动机处于高空小表速状态时受雷诺数和功率提取的影响最大，此时风扇和高压压气机的稳定裕度均下降明显；附加引气在一定程度上可以增加发动机的稳定裕度；部件老化对发动机稳定裕度的影响不可忽略。（3）通过分析动态过程中发动机转速、流量、压力、能量存在的不平衡现象，在发动机稳态模型的基础上，增加主燃烧室、混合室及加力燃烧室、外涵通道的容积效应和高低压转子动力学方程，建立了可以分析加/减速、接通/断开加力等降稳因子对发动机气动稳定性影响的动态过程数学模型，并采用时间推进的欧拉方法进行求解，得到了加速过程、减速过程、接通加力过程和断开加力过程对发动机稳定裕度的影响。计算结果表明，加速过程中，和风扇相比，高压压气机加速线更趋于靠近稳定边界；减速过程中，风扇和高压压气机受稳定边界的限制均较小，只有在低转速段时的风扇稳定裕度和稳态相比有少许的下降；接通/断开加力过程中，高压压气机的稳定裕度基本不变，而风扇的稳定裕度波动较大。（4）通过将平行压气机模型扩展为“平行发动机”模型，并采用二维、无粘的欧拉方程进行描述，建立了分析进气畸变对发动机气动稳定性影响的数学模型，并采用四阶Runge-Kutta方法进行求解。计算得到了冲击波、动态温升和动态压力畸变下影响下发动机内部的参数变化，并对本文提出的基于“临界压力梯度”的失稳判据进行验证；和现有失稳判据相比，本文提出的失稳判据适应性更强；通过计算发动机流道中的畸变传递曲线，评估了发动机部件对畸变的衰减能力，其中风扇和高压压气机对畸变的衰减能力最强；计算得到了典型状态下发动机的临界畸变值、畸变敏感系数和补偿进气畸变所需要的局部需用稳定裕度。（5）作为研究成果的集中体现，基于VC++软件，编制了具有自主知识产权的航空发动机气动稳定性分析系统。该系统下集成了构建多种类型发动机所需的标准模型，允许用户选用标准模型来组成目标发动机进行分析。该系统功能全面，可以定量的分析气动稳定性评定规范中规定的各项降稳因子对发动机稳定裕度的影响程度，适用于发动机方案设计阶段和工程设计阶段的气动稳定性分析研究。该分析系统具有友好的界面和可扩展性，有利于气动稳定性分析方法的广泛应用和不断发展。（6）针对某涡扇发动机，利用所建立的分析系统，完成了工程设计阶段全飞行包线范围内的气动稳定性综合评估。结果表明，在所评估的状态中，高空小表速状态下风扇和高压压气机的总需用稳定裕度最大；在所有降稳因子中，补偿进气畸变的局部需用稳定裕度最高；在高空小表速状态下，雷诺数是影响发动机气动稳定性的重要因素之一。更多还原

【Abstract】 Aerodynamic stability has become an important tactical and technical index of the aero-engine inmodern time.A well-designed aero-engine must has the sufficient available stability margin in theflight envelop, addition required to achieve good performance and high reliability. For this reason，theaerodynamic stability of aircraft engines must be analyzed in every stage of the developmentcycle.There are many factors affect the aerodynamic stability,pressure distortion,temperaturedistortion,blast wave and Reynolds number are the main external disturbancefactors;acceleration/deceleration, afterburner’s turn on/off, power extraction and additionalair-bleeding, component deterioration, production deviation, production/assembly variation, controltolerance are the main internal disturbance factors.In the initial stage of engine’s research anddevelopment, In principle, it is impossible to obtain the experimental data of the influence of variousdisturbance factors on the engine, and the full flight envelope tests cost too much. For the experimentwhich could not be taken on the ground or altitude test facilities should be replace by the numericalcalculation.Therefore, the numerical calculation method in the aerodynamic stability analysis attractsa high attention and is used widely.In order to improve the functionality and scope of numerical calculation in the aero-engineaerodynamic stability analysis, based on the mechanism analysis how the disturbance factors affectthe engine’s aerodynamic stability, the corresponding mathematical models and solution methodswere established and developed, and an analysis platform with comprehensive functions wasconstructed, which is applicable to the scheme design stage and engineering design stage. Taking aturbofan engine for example, the aerodynamic stability in full flight envelope was evaluatedcomprehensive. The main contents and conclusions in this paper can be summarized as follows：（1）The aerodynamic stability analysis contents in different stages of development of theengine’s research and development were summed up, how the disturbance factors affect the engine’saerodynamic stability were analyzed and the rational classification for factors were made.Based on atechnical task of a turbofan engine and with reference to the military standard GJB/Z224-2005,6typical states were identified in the flight envelope. Using the statistical normative value of thedisturbance factor’s local required stability margin, the total required stability margins were estimatedand the aerodynamic stability analysis in engine’s scheme design stage were finished.（2）Based on the component-matching method, in accordance with the regulation law and limit parameters, the steady-state mathematical model was established, and Newton-Raphson iterationmethod was used to solve the common equation, so the available stability margin of fan and highpressure compressor under typical states could be obtain. By embedding the Reynolds numbercorrection model, power extracted and additional air-bleeding model and component aging correctionmodel in the steady-state mathematical model, the mathematical model which could evaluate theReynolds number, power extraction, additional air-bleeding, component deterioration were built.Results show that, Reynolds number and power extraction have a greatest impact when the engineworks at the high altitude small table speed state, and the stability margins of fan and high pressurecompressor drop significantly; to some extent, additional air-bleeding would increase the stabilitymargin; The effects of the component deterioration on the stability margin would not be ignored.（3）By analyzing the imbalance of speed, flow mass, pressure and energy in the aero-enginedynamic process, based on steady-state model, the dynamic equations of the main combustion, themixing chamber combined the afterburner, and the bypass, high and low pressure rotor were increased,so the dynamic process mathematical model which can be used to analyze the disturbance factors,such as acceleration/deceleration, afterburner turn on/off, and the time-marching Euler method wereused to solve. Results show that, in the acceleration process, compared with the fan, the work line ofhigh pressure compressor tends to stability boundary more; in the deceleration process, the fan andhigh pressure compressor are not limited too much to the stability boundary, only the stabilitymargin declines little compared with steady-state when the fan’s speed is low; in the process ofafterburner turn on/off, the high pressure compressor stability margin almost keep constant, while thefan’s stability margin fluctuate significantly.（4）The parallel compressor model were extended to the parallel engine model, which weredescribed by two-dimensional integral inviscid Euler equations,the calculation model for analyzinghow the inlet distortions effect the aero-engine aerodynamic stability, and four-order Range-Kuttamethod were used to solve the equations.The changes of engine internal parameters were calculatedwhen the blast wave, dynamic temperature rise and dynamic pressure distortion work in the engineinlet; the instability criterion which is based on "critical pressure gradient”was verified, comparedwith existing instability criterion, the criterion suggested by this paper has the best adaptability; Bycalculating the distortion transfer curves along the engine flow path, the components of the enginedistortion attenuation capability were evaluated, wherein the fan and high pressure compressor werestrongest;Under typical states, the critical distortion index, distortion sensitivity coefficients and localrequired stability margins compensated to the inlet distortion were also obtained. （5）As the concentrated expression of the research, based on VC++program, an aero-engineaerodynamic stability analysis system was designed and built. The standard models used to constructmultitypes of engines were integrated in this system, and the target engine would be made up by thestandard models. This system is fully functional, and could be used to quantitatively analyse how thedisturbance factors affect the engine’s aerodynamic stability, which were specified by the assessmentguidelines. This system is applicable to the scheme design stage and engineering design stage. Thissystem also has friendly interfaces and is extensible, and is propitious to the widely used andcontinuing development of aerodynamic stability analysis method.（6）For a turbofan engine, using this system, comprehensive assessment of aerodynamicstability in the full flight envelope were completed. Resuls show that, under all evaluating states, theoverall required stability margins of fan and high pressure compressor are the largest, when the engineworks on the the hight-altitude and small-speed state; During all the disturbance factors, the localrequired stability margin for inlet distortion is largest；The Reynolds number is one of the mostimportant factor to the aerodynamic stability the engine works on the the hight-altitude andsmall-speed state.更多还原