固体燃料超燃冲压发动机燃烧室工作过程理论与实验研究

发布时间：2018-08-12 10:03

【摘要】：本文在固体燃料超燃冲压发动机燃烧室内流场二维计算结果的基础上，简化并提出了一种准一维计算方法。将常见的燃面退移速率计算方法耦合到准一维方程中，该方程考虑了燃烧室面积变化、摩擦、加质和加热。燃面退移速率是流场内温度、压力、密度和燃烧室直径的函数，而流动方程中加质源项又是燃面退移速率的函数，这样就能做到燃面退移速率和内流场参数的同步计算。将前一时刻的燃面退移速率加上燃烧室直径得出下一时刻的燃烧室直径，得出下一时刻燃烧室的边界条件，从而将固体燃料燃烧室内非定常的流动、燃烧和燃面退移问题通过每一时刻的定常计算求解。通过对比，计算结果与实验数据符合的较好，证明了计算模型的合理性。为固体燃料超燃冲压发动机燃烧室的设计和分析提供了一种简单、快速和灵活的数值方法。尔后从固体燃料燃烧室的特点和超声速燃烧流动的基本规律出发，提出了固体燃料超燃冲压发动机燃烧室设计的基本理论，这个理论包括燃烧室满足自点火和火焰稳定性条件，燃料质量流量和空气质量流量满足适当的比例，减小总压损失等。并根据准一维计算程序，提出一种燃烧室的准一维设计方法。同时将燃烧室内的燃烧流动进一步简化为等截面和变截面加热管流，提出了一种更加简便快速的燃烧室工程设计方法。设计并制造了一个小型直连式试车台，核心部件空气加热器以甲烷为原料，具有启动迅速、工作稳定、污染物少等优点。通过实验验证了燃烧室自点火和火焰稳定性条件，获得了燃烧室不同时刻的燃面退移速率和平均燃面退移速率，发现燃面退移速率最大值出现在凹腔和等直段的连接部以及等直段和扩张段的连接部。然后将实验和数值计算相结合讨论了燃烧室工作过程中燃烧室结构和其他相关参数的变化规律。发现在燃烧室在工作过程中，凹腔慢慢变大、变深，但凹腔的主体形状不会发生较大的改变，能够一直起到稳定火焰的作用。等直段后端慢慢消失和扩张段连为一体，扩张段扩张比逐渐减小。凹腔内部的燃面退移速率较小，且沿着轴线逐渐增大。在等直段和扩张段连接处尖角消失之前，燃面退移速率在等直段内出现先减小后增大，尖角消失之后，燃面退移速率沿轴线逐渐减小。扩张段内燃面退移速率沿轴线逐渐减小。不同时刻，同一位置的燃面退移速率随着燃烧室的工作过程逐渐减小。但由于燃面的增大，燃空比在燃烧工作过程中相对稳定。由于燃烧室内腔的增大，内流场马赫数在燃烧室工作过程中逐渐增大，导致气流的总压损失增大，做功能力下降，发动机的推力会下降。研究了燃烧室入口和进气道出口气流参数的匹配问题。在飞行条件一定的前提下，提高燃烧室入口总压，提高燃烧室入口总温，降低燃烧室入口马赫数，能增大燃面退移速率从而减小燃烧室的长度，同时能提高发动机的比推力。通过敏感性分析发现，总温的燃烧室的性能影响最大。探讨了凹腔尺寸对燃烧室性能的影响。在燃烧效率一定的条件下，增大凹腔出口和燃烧室入口的相对直径，会增大燃烧室内流场马赫数，增大总压损失，减小燃面退移速率，增大燃烧室的长度，减小发动机的比推力。然而增大凹腔的深度和长度并不会对燃烧室的性能产生较大的影响。最后研究了燃烧室在非设计状态下的性能变化规律。对于设计定型的燃烧室，随着飞行马赫数的增大，发动机的比推力先增大后减小，在设计点处最大，，比冲逐渐减小；随着飞行高度的增大，发动机的比推力也先增大后减小，在设计点处最大，比冲小幅增大。
[Abstract]:On the basis of the two-dimensional calculation results of the flow field in a solid fuel scramjet combustor, a quasi-one-dimensional calculation method is simplified and proposed in this paper. The common methods for calculating the burning surface regression rate are coupled into a quasi-one-dimensional equation, which takes into account the variation of the combustor area, friction, mass addition and heating. The burning surface regression rate is the flow field. The internal temperature, pressure, density and chamber diameter are functions of the burning surface regression rate in the flow equation, so that the burning surface regression rate and the internal flow field parameters can be calculated simultaneously. The boundary conditions of the combustor can be used to solve the unsteady flow, combustion and surface regression problems in the solid fuel combustor through the steady calculation at each moment. It provides a simple, fast and flexible numerical method.
Then, based on the characteristics of solid fuel combustor and the basic law of supersonic combustion flow, a basic theory for the design of solid fuel scramjet combustor is proposed. The theory includes that the combustor satisfies the conditions of self-ignition and flame stability, the mass flow rate of fuel and the mass flow rate of air satisfies an appropriate proportion, and the total pressure is reduced. According to the quasi-one-dimensional calculation program, a quasi-one-dimensional design method of combustion chamber is proposed, and the combustion flow in combustion chamber is further simplified as a heating pipe flow with constant cross-section and variable cross-section.
A small direct-connected test rig was designed and manufactured. The core component of the air heater is methane. It has the advantages of rapid start-up, stable operation and less pollutants. The maximum rate of burning surface regression occurs at the joint of the cavity and the equal straight section and the connection of the equal straight section and the expansion section. The back end of the straight section disappears slowly and the expansion section is connected with each other, and the expansion ratio of the expansion section decreases gradually. After the tip angle disappears, the burning surface regression rate decreases along the axis. At different times, the burning surface regression rate at the same position decreases with the working process of the combustor. With the increase of chamber, the Mach number of internal flow field increases gradually during the combustion chamber operation, which leads to the increase of total pressure loss of air flow and the decrease of engine thrust.
The matching problem of air flow parameters at the inlet and inlet outlet of a combustor is studied. Under certain flight conditions, the total pressure at the inlet of the combustor is increased, the total temperature at the inlet of the combustor is increased, the Mach number at the inlet of the combustor is decreased, the burning surface retreat rate is increased, the length of the combustor is reduced, and the specific thrust of the engine is increased. It is found that the total temperature has the greatest influence on the performance of the combustor.The effect of cavity size on the performance of the combustor is discussed.Under certain combustion efficiency conditions,increasing the relative diameter of the cavity outlet and the combustor inlet will increase the Mach number of the flow field in the combustor,increase the total pressure loss,reduce the rate of burning surface retreat and increase the length of the combustor. However, increasing the depth and length of the cavity does not affect the performance of the combustor. Finally, the performance variation of the combustor in the off-design state is studied. With the increase of flight altitude, the specific thrust of the engine increases first and then decreases, and the specific impulse increases slightly at the design point.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：V435

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