宽马赫数运行冲压发动机的热力性能优化分析

发布时间：2018-06-28 22:01

本文选题：宽马赫数运行 + 冲压发动机　；参考：《哈尔滨工业大学》2016年硕士论文

【摘要】：宽马赫数运行是未来超燃冲压发动机发展的必然需求。超燃冲压发动机在低马赫数下受到不起动边界的限制,在飞行马赫数较高时又受到燃烧室的材料的最大可承受温度和气体高温解离的限制;在低马赫数加速阶段要求冲压发动机具有足够大的推力,在巡航阶段需要提高发动机的经济性,因此研究如何使得冲压发动机能够在宽马赫数范围内高效运行十分必要。针对超燃冲压发动机宽马赫数运行的需求,研究了宽马赫数运行的冲压发动机的热力学循环适用边界,对超燃冲压发动机施加热堵塞边界和温限边界的约束,获得了用进气道的压缩温升比和燃烧室的加热比所表征的超燃冲压发动机的进气道和燃烧室配合的最大工作边界,而亚燃冲压发动机仅受到温度边界的限制。在这两种约束下超燃冲压发动机具有最大的循环有效功,且存在于最大的运行边界上:在马赫数较低时,主要受到热堵塞边界的约束,此时超燃冲压发动机的循环有效功较小,而进气道压缩至接近滞止状态的亚燃冲压发动机的性能较好些;随着马赫数的增加,超燃冲压发动机同时受到两种边界的约束,马赫数再增大时,发动机只受到温限边界的约束,此时由于温限边界的存在导致了发动机的最大循环有效功有限,为保证燃烧室安全运行,难以增加燃油当量比获得更大的循环有效功,此时需要借助等静温加热过程将压缩和燃烧过程的温升解耦。最佳的工作模式为低马赫数时采用亚燃,马赫数达到一定程度后,采用超燃,且超燃状态下为进一步增大发动机的循环有效功和推力,需要借助等马赫数和等静温等过程相配合。对采用支板-凹腔稳燃的固定几何冲压发动机进行了实验和仿真研究,发现飞行马赫数和燃油分对冲压发动机的运行边界影响很大。支板位置越靠近隔离段入口,即燃烧的起始位置越靠前,冲压发动机越容易出现不起动现象。来流马赫数越低,越容易出现不起动现象,燃烧室所能容纳的加热量有限,燃油当量比较小,燃油应当向燃烧室下游分配。对采用“等-扩-等”构型的冲压发动机进行了性能评估,建立了冲压发动机的集总参数的性能评估模型,发现对于固定几何的冲压发动机,在设计点工作时,可在大的燃油当量比范围内工作,飞行马赫数较小时,受约束于不起动边界,冲压发动机的最大燃油当量比随着马赫数的降低而减小。冲压发动机的燃烧室的扩张比越大,燃烧室所能容纳的热量越多,冲压发动机所能正常工作的范围越大,但是相同的燃油当量比和马赫数下,燃烧室的扩张比越小,冲压发动机的性能越好。欲保证冲压发动机能够在宽马赫数范围内高性能工作,要求冲压发动机的扩张比可调,冲压发动机的扩张比时刻保持能够正常工作的最小扩张比。对于宽马赫数运行的冲压发动机,等动压飞行时,需要解决低马赫数下的推力低谷以及保证在低马赫数段加速过程具有足够的有效推力和高马赫数巡航时的经济性问题。可以通过增大低马赫数下隔离段以及燃烧室的面积的方式,来增大冲压发动机的进气道和尾喷管的通流能力,增大空气流量以补足推力。为保证加速性能,需要提高冲压发动机的燃烧效率并在加速过程中不断减小冲压发动机的燃烧室的扩张比,并增大尾喷管的膨胀比,保证发动机的推力最大。巡航阶段需要根据飞行阻力调整逐渐减小燃油当量比和油气比,在保证推力足够的情况下,通过控制系统将燃油当量比和油气比调整到所允许的最小值,增大飞行航程。设计了一个能够在马赫数2~7之间运行的变几何冲压发动机,加速过程中,燃烧室扩张比减小,尾喷管的膨胀比增大,能够满足宽马赫数运行的要求。
[Abstract]:The wide Maher number operation is the inevitable development of the future scramjet. The scramjet is limited by the non starting boundary under the low Maher number, and is restricted by the maximum acceptable temperature of the combustor and the high temperature dissociation of the gas at the higher flight Maher number; the ramjet is required at the low Maher number acceleration stage. With enough thrust, it is necessary to improve the economy of the engine in the cruise phase, so it is necessary to study how to make the ramjet run efficiently in the wide Maher range. In view of the needs of the wide Maher number operation of the scramjet, the thermodynamic cycle applicable boundary of the ramjet with wide Maher number transport is studied. The maximum working boundary of the scramjet inlet and combustion chamber characterized by the compression temperature rise ratio of the inlet and the heating ratio of the combustor is obtained by applying the constraints on the boundary and temperature limit of the scramjet, which is characterized by the compression temperature rise ratio of the intake port and the heating ratio of the combustor, while the subcombustion ramjet is limited by the temperature boundary only. Under these two constraints, The combustible ramjet has the largest circulating effective work, and exists on the maximum operating boundary. At the lower Maher number, the heat blockage boundary is the main constraint. At this time, the circulating effective work of the scramjet is smaller, and the performance of the subcombustible ramjet which is compressed to the state of hysteresis is better; with the Maher number. At the same time, the scramjet is constrained by two kinds of boundary. When the Maher number is increased again, the engine is restricted by the limit of the temperature limit. At this time, the existence of the temperature limit leads to the maximum effective work of the engine. In order to ensure the safe operation of the combustion chamber, it is difficult to increase the efficiency of the fuel equivalent ratio. The temperature rise of compression and combustion process should be decoupled with the help of isostatic heating process. The best working mode is to use sub combustion for low Maher number. After the Maher number reaches a certain degree, the burning is used, and the engine's cycle effective work and thrust can be further increased under the condition of the super burning. It is necessary to cooperate with the other processes such as the Maher number and the isostatic temperature. The experimental and simulation study of a fixed geometric ramjet using a supporting plate and concave cavity is carried out. It is found that the flight Maher number and the fuel fraction have a great influence on the running boundary of the ramjet. The closer the position of the supporting plate is to the entrance of the isolation section, the more easy the starting position of the burning is, the more easy the starting is to appear. To flow Maher The lower the number, the less starting, the combustion chamber can hold a limited amount of heating, the fuel equivalent is smaller, the fuel should be allocated to the downstream of the combustor. The performance evaluation of the ramjet using "equal expansion" configuration is evaluated, the performance evaluation model of the lumped parameter of the ramjet is established, and the fixed geometry is found. The ramjet, when working at the design point, can work within a large fuel equivalent ratio range, the flight Maher number is smaller, the maximum fuel equivalent ratio of the ramjet decreases with the decrease of the Maher number. The greater the expansion ratio of the ramjet combustor, the more heat the combustor can hold, the more punching. The larger the range of the engine can work, the larger the fuel equivalent ratio and the Maher number, the smaller the expansion ratio of the combustor, the better the performance of the ramjet. To ensure the high performance of the ramjet in the wide range of Maher numbers, the expansion ratio of the ramjet is adjustable and the expansion ratio of the ramjet is kept at the moment. The minimum dilatation ratio that can work normally. For a ramjet running with a wide Maher number, equal dynamic pressure is needed to solve the low Maher number of thrust valleys and to ensure that the economy of sufficient effective thrust and high Maher number cruising in the low Maher number acceleration process can be solved by increasing the low Maher number of isolation segments by increasing the number of low Maher numbers. And the area of the combustor to increase the flow capacity of the inlet and tail nozzle of the ramjet and increase the air flow to make up the thrust. In order to ensure acceleration, the combustion efficiency of the ramjet is improved and the expansion ratio of the ramjet combustion chamber is continuously reduced and the expansion ratio of the tail nozzle is increased during the acceleration process. Ensure the maximum thrust of the engine. The cruise phase needs to gradually reduce the fuel equivalent ratio and the oil / gas ratio according to the flight resistance adjustment. When the thrust is sufficient, the fuel equivalent ratio and the oil and gas ratio are adjusted to the allowable minimum, and the flight range is increased. A change can be set up between the Maher number 2~7. During the acceleration process, the expansion ratio of the combustion chamber decreases, and the expansion ratio of the nozzle increases, which can meet the requirement of wide Maher number operation.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK401

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