脉动喷气发动机工作过程数值模拟

【作者】 张帆；

【导师】 武晓松；

【作者基本信息】 南京理工大学 ， 航空宇航推进理论与工程， 2009， 硕士

【摘要】 脉动喷气发动机是一种结构简单、较为理想的低成本推力装置,它利用非稳态燃烧产生间歇性推力,并在初次启动后具有自吸气特点。本论文通过编制特征线程序和商业软件的模拟,研究了脉动喷气发动机的工作特性,对于有效建立脉动喷气发动机具有指导意义。本文利用特征线方法对脉动喷气发动机的性能进行理论预估,即在x-t平面建立燃烧波在发动机内传播过程的物理模型,联立求解一维非定常的连续方程、动量方程和能量方程所组成的双曲型偏微分方程,得到有限差分网格的数值解,考虑管道内不连续的面积变化、壁面摩擦、传热过程和热量添加的影响,考虑熵的变化和沿特征线的传播,模拟发动机内排气过程和多循环的工作。使用MATLAB7.0软件编制程序,得到发动机燃烧室、进气道、尾管内的压力、速度-时间曲线,得到指定点的粒子轨迹,通过应用推力模型、频率模型得到发动机推力和频率。利用本文编制的特征线程序研究了100cm、53.6cm和21.3cm三种脉动喷气发动机的物理模型,对发动机性能进行理论预估,分析发动机的工作过程和流场状态。同时,采用计算流体力学软件CFX11.0对53.6cm脉动喷气发动机内三维反应流场多循环的工作过程进行数值模拟,分析了不同进气道直径对发动机频率的影响,计算结果表明该型发动机频率随其直径的增大而增大。通过以上研究表明,特征线方法在脉动喷气发动机数值计算中较为合理,可以正确地模拟无阀式脉动发动机的工作过程。同时,使用CFX软件成功模拟出发动机的多循环工作过程,为脉动喷气发动机的机理研究提供了重要的补充手段。更多还原

【Abstract】 Pulsejet is becoming an ideal low cost propulsion device due to the simplest form. Such engines produce intermittent thrusts depending on unsteady combustion and act self-sustained function. This thesis deals with computer program and commercial software to study the performance of pulsejet.It is possible to predict the academic evaluation of the pulsejet performance using the method of characteristics. The thesis establishes physical model of combustion wave propagating through the engine in the x-t plane, and manipulates one-dimensional unsteady hyperbolic partial equation combined with continuity equation, momentum equation and energy equation to obtain finite diffusion grids numerical solutions, considering the incorporation of area discontinuity, wall fiction, heat transfer and heat addition, as well as the incorporation of entropy variation and the propagation along path lines. Exhausting gas process and multi-cycles working process are stimulated respectively. MATLAB software is an optimal implement to compile the computer program, and therefore the pressure、velocity variation with time in the inlet、combustion chamber and tailpipe are required.It also investigates three kinds of physical models with regard to 100cm、53.6cm and 21.3cm pulsejets, predicts the performance and analyzes the working process. Correspondingly, apply with CFX11.0 commercial software package to the tree-dimensional numerical simulation of. interior flow in the pulsejet and build up multi-cycles working process to compute a kind of pulsejet with respect to 53.6cm. The result is coincident with the previous method of characteristics. Finally, this paper analyzes the engine performance of different inlet diameters. It is showed that the frequency increases accompanying with the increasing of inlet diameter.From the above analysis, it can be concluded that method of characteristics has been developed for a better implement in the computer program of pulsejet, which can be used to stimulate the working process of valveless pulsejet. At the same time, CFX software can also be used to stimulate the multi-cycles working processes. Both of them are the important complemental methodologies for the research of pulsejet theory.更多还原