离心喷嘴燃油流动特性研究

发布时间：2018-05-31 14:41

本文选题：离心喷嘴 + 几何参数　；参考：《南京航空航天大学》2016年硕士论文

【摘要】：离心喷嘴广泛应用于航空发动机燃烧室中,是将液态燃油破碎成油雾滴的装置,直接影响火焰稳定、燃烧效率、污染物排放等燃烧室性能。影响离心喷嘴性能的因素很多,其中喷嘴内部流动特性是关键因素之一。本文即以此为对象,开展了离心喷嘴内部流动特性和燃油雾化性能的研究。首先进行了数值计算研究,通过计算方法研究,获得了基于VOF隐式解的计算方法,并应用此计算方法计算了一种典型离心喷嘴,获得了不同供油压差、旋流室长度、旋流室直径、喷口长度、喷口直径、旋流槽进口面积、旋流室收敛角下离心喷嘴的流场,得到了各参数变化下离心喷嘴内流特性与雾化性能变化的规律。此外,对放大尺寸的离心喷嘴进行了计算,验证了算法的准确性并发现在高雷诺数下,离心喷嘴的流动特征基本不变。由于测试技术的限制,试验研究基于本文所设计的大尺寸透明离心喷嘴,研究主要包括离心喷嘴旋流室内切向速度,轴向速度,流量特性,雾化锥角,液膜厚度,雾化粒径。结果表明:(1)在旋流室内,切向速度沿半径呈指数分布且分布沿轴向基本一致。而对于轴向速度,在旋流室内半径较大处,流动几乎滞止,随着半径的降低,轴向速度突然产生一个阶跃并保持稳定至空气涡半径处。这说明工质主要从半径较小的空气涡处流向喷口。在试验参数范围内,根据各几何参数对切向速度的影响总结了旋流室内切向速度公式。(2)获得当Ap/Dsdo在0.38至1.05,Ds/do在3至7.5,Ls/Ds在0.57至1.33,lo/do在0.17至1,流量系数、液膜厚度、雾化锥角、SMD关于各无量纲参数的变化规律,并总结了流量系数与雾化锥角的无量纲经验公式。(3)压差对离心喷嘴流量系数几乎无影响。随着压差的增大,液膜厚度降低,雾化锥角增大并在达到最大锥角后趋于不变,离心喷嘴内切向速度与轴向速度增大。数值计算与试验结果存在误差,但规律基本一致。试验的结果将对深入了解燃油雾化机理和性能变化的规律,具有重要理论和应用价值。
[Abstract]:Centrifugal nozzle is widely used in the combustion chamber of aero-engine. It is a device to break liquid fuel into droplets, which directly affects the performance of combustion chamber such as flame stability, combustion efficiency, pollutant emission and so on. There are many factors affecting the performance of centrifugal nozzles, among which the internal flow characteristics of centrifugal nozzles are one of the key factors. In this paper, the internal flow characteristics and fuel atomization performance of centrifugal nozzle are studied. First of all, the numerical calculation is carried out, and the calculation method based on the implicit solution of VOF is obtained, and a typical centrifugal nozzle is calculated by using this method. The different oil supply pressure difference and the length of swirl chamber are obtained. The flow field of centrifugal nozzle under swirl chamber diameter, nozzle length, nozzle diameter, swirl groove inlet area and convergent angle of swirl chamber is obtained. In addition, the accuracy of the algorithm is verified by the calculation of the centrifugal nozzle with enlarged size, and it is found that the flow characteristics of the centrifugal nozzle are basically unchanged at high Reynolds number. Due to the limitation of testing technology, the experimental research is based on the large size transparent centrifugal nozzle designed in this paper. The research mainly includes tangential velocity, axial velocity, flow characteristic, atomization cone angle, liquid film thickness and atomization particle size. The results show that the tangential velocity distributes exponentially along the radius in the swirl chamber and is basically consistent with the axial distribution. For axial velocity, the flow is almost stagnant where the radius of the swirl chamber is large. With the decrease of radius, the axial velocity suddenly produces a step and remains stable to the radius of the air vortex. This indicates that the working fluid mainly flows from the air vortex with small radius to the nozzle. In the range of test parameters, the tangential velocity formula of swirl chamber is summarized according to the influence of geometric parameters on tangential velocity.) when Ap/Dsdo is between 0.38 and 1.05g Dsrdo between 3 and 7.5 L / s, the flow coefficient and liquid film thickness are 0.17 to 1. The variation of dimensionless parameters in SMD of atomization cone angle is studied. The dimensionless empirical formula of flow coefficient and atomization cone angle is summarized. The pressure difference has little effect on the flow coefficient of centrifugal nozzle. With the increase of pressure difference, the thickness of liquid film decreases, the atomization cone angle increases and the maximum cone angle is reached, and the tangential velocity and axial velocity increase in the centrifugal nozzle. There is an error between the numerical calculation and the experimental results, but the law is basically consistent. The experimental results will be of great theoretical and practical value for further understanding the mechanism of fuel atomization and the law of performance change.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：V231.2

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