加力燃烧室中声、涡和火焰相互作用的特性研究

发布时间：2018-09-05 12:08

【摘要】：不稳定燃烧与燃烧室内的多种因素有关,其中最主要的就是声(压力脉动)、涡和火焰相互作用引起的燃烧不稳定。本文以某型航空发动机加力燃烧室为研究对象,采用数值模拟方法对加力燃烧室中声、涡和火焰的相互作用的特性进行了研究,本文完成的主要内容及获得的结论如下:1.原型加力燃烧室简化和计算方法正确性验证。1)根据稳定器前马赫数相似原则,在原型加力燃烧室几何结构特点的基础上,确立一个较为简化的加力燃烧室方案;2)使用与本文相同的计算方法对模型加力燃烧室热声耦合特性进行数值模拟,并与试验结果进行对比,计算误差在10%以内。2.加力燃烧室冷态流场特性研究。首先,通过非稳态计算,分析了旋涡脱落过程和旋涡脱落对流场动态压力脉动的影响。其次,在进口处施加低、中、高频三种扰动声波,观察其对加力燃烧室内不同位置压力脉动和旋涡脱落频率的影响,得出加力燃烧室声(压力脉动)和涡的相互作用规律。研究发现:1)进口条件发生变化时,涡的脱落频率也随之变化,并且和稳定器升力的脉动频率以及涡核位置的压力脉动频率相同;2)旋涡脱落时,加力燃烧室流场压力脉动幅值在回流区达到了最大值,为进口总压的1.3%;3)随着扰动声波频率增加,旋涡脱落频率和加力燃烧室压力脉动频率先增大后减小,在20Hz时最大,压力脉动幅值先减小后增大,在20Hz时最小,即加力燃烧室中旋涡脱落造成的压力脉动对进口低频扰动最为敏感;4)随着扰动声波振幅增加,旋涡脱落频率和加力燃烧室压力脉动频率增大,压力脉动幅值减小。3.加力燃烧室热态燃烧特性研究。在加力燃烧室冷态流场计算的基础上,采用12组分10步化学反应机理,通过改变当量比、进气速度、喷嘴位置和在进口处施加扰动声波,研究加力燃烧室热态时声(压力脉动)、涡和火焰的相互作用规律。结果表明:1)随着旋涡的周期性脱落,加力燃烧室稳定器后的火焰结构呈现有规律地周期性抖动,且二者的频率相同;2)当量比、进气速度和喷嘴位置变化时,加力燃烧室的旋涡脱落频率、压力脉动和放热脉动频率三者变化趋势相同;3)贫油时当量比增加,压力脉动和放热脉动振幅增大,但当量比增大到一定值,压力脉动和放热脉动振幅反而减小。进气速度增加,压力脉动和放热脉动频率先增大后减小,振幅先减小后增大。喷嘴后移,压力脉动频率和放热脉动频率减小,压力脉动振幅和放热脉动振幅持续增大;4)压力脉动幅值沿轴向分布规律符合加力燃烧室声学通道分布规律,加力燃烧室对低频扰动声波最为敏感,热态时的加力燃烧室声场能量远远大于冷态。
[Abstract]:Unstable combustion is related to a variety of factors in the combustion chamber, the most important of which is acoustic (pressure pulsation), the combustion instability caused by the interaction of vortex and flame. In this paper, the characteristics of the interaction of sound, vortex and flame in an aero-engine afterburner are studied by numerical simulation method. The main contents and conclusions of this paper are as follows: 1. Based on the principle of similarity of Mach number in front of stabilizer and on the basis of geometric characteristics of prototype afterburner, A simplified afterburner scheme is established. Numerical simulation of the thermoacoustic coupling characteristics of the model afterburner is carried out using the same calculation method as in this paper. The calculation error is less than 10%, compared with the experimental results. Study on cold flow field of afterburner. Firstly, the effect of vortex shedding process and dynamic pressure pulsation of vortex shedding flow field is analyzed by unsteady calculation. Secondly, three kinds of disturbance sound waves, low, middle and high frequency, are applied to the inlet to observe the influence on pressure pulsation and vortex shedding frequency at different positions in the afterburner, and the interaction law between the pressure pulsation and vortex in the afterburner is obtained. It is found that when the inlet conditions change, the frequency of vortex shedding also changes, which is the same as the pulsation frequency of the lift of the stabilizer and the pressure pulsation frequency of the vortex core. The amplitude of flow field pressure pulsation in the afterburner reaches the maximum value in the reflux region, which is 1.3 / 3 of the inlet total pressure.) with the increase of the frequency of the disturbance sound wave, the vortex shedding frequency and the pressure pulsation frequency of the afterburner first increase and then decrease, and the maximum at 20Hz. The amplitude of pressure pulsation decreases first and then increases, and it is the smallest at 20Hz, that is, the pressure pulsation caused by vortex shedding in the afterburner is the most sensitive to the inlet low-frequency disturbance. The vortex shedding frequency and the pressure pulsation frequency of the afterburner increase, and the amplitude of pressure pulsation decreases by .3. Study on hot combustion characteristics of afterburner. Based on the calculation of the cold flow field in the afterburner, the chemical reaction mechanism of 12 components and 10 steps is adopted. By changing the equivalent ratio, the inlet velocity, the position of the nozzle and the disturbance sound wave at the inlet, The interaction of sound (pressure pulsation), vortex and flame in the hot state of the afterburner is studied. The results show that with the periodic shedding of the vortex, the flame structure behind the stabilizer of the afterburner appears periodic jitter regularly, and the frequency of the two is the same as that of the second) equivalent ratio, the inlet velocity and the nozzle position change. The vortex shedding frequency, pressure pulsation and exothermic pulsation frequency of the afterburner have the same changing trend. 3) the equivalent ratio of lean oil increases, the amplitude of pressure pulsation and exothermic pulsation increases, but the equivalent ratio increases to a certain value. The amplitude of pressure pulsation and exothermic pulsation decreases. With the increase of inlet velocity, the frequency of pressure pulsation and exothermic pulsation first increases and then decreases, and the amplitude decreases first and then increases. When the nozzle moves backward, the pressure pulsation frequency and exothermic pulsation frequency decrease, the pressure pulsation amplitude and exothermic pulsation amplitude increase continuously) the pressure pulsation amplitude distributes along the axial direction in accordance with the distribution law of the acoustic channel in the afterburner. The afterforce combustor is most sensitive to low-frequency disturbed acoustic waves, and the sound field energy of the afterburner in hot state is much larger than that in cold state.
【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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