【作者】 孙鹏；

【导师】 冯国泰；

【作者基本信息】 哈尔滨工业大学 ， 动力机械及工程， 2007， 博士

【摘要】 回顾燃气涡轮发动机问世以来近60年的发展历史,在二十世纪六十年代中期主要重视的是发动机性能的好坏,追求高的性能指标,而对进气畸变的影响未引起足够的重视。这种情况在早期的亚音速、小机动飞行条件下是可以的。但随着飞机飞行速度、高度的不断提高,机动性的不断增加,以及导弹武器的使用,畸变的影响越来越突出,实践中暴露出来的问题也越来越严重。进入21世纪,飞机发动机向着非常规机动性和超音速机动性的方向发展。叶轮机械无一例外必须在非均匀进口条件下工作。这就使得压气机的效率和压比比均匀进气条件有所降低,更重要的是进口气流的不均匀会加剧内部流场的非定常现象,从而使压气机气动稳定性下降,使之提前失速。因此,深入的研究进口气流参数的非均匀性和内部流场的非定常性对进一步提高叶轮机械的性能有着非常重要的意义。本文以某型跨音风扇作为研究对象,首先对原型风扇设计工况数值模拟结果与实验结果进行了对比与分析。在本文计算条件下,三维非定常数值模拟得到的风扇效率曲线在趋势上与实验曲线匹配的较好。数值模拟结果在最高效率点附近与实验值最接近。计算工况越接近喘振点,数值模拟的误差越大。湍流模型的误差和较大的数值粘性是造成偏差的主要原因。对数值模拟与实验结果的进一步验证表明,本文使用的数值模拟方法可以满足定性研究风扇流场的要求。通过研究不同畸变度和畸变角时总压畸变对风扇流场进出口参数的影响,较系统的给出了多种畸变条件下总压畸变经风扇的传递情况,并详细分析了畸变流场对风扇进出口参数的影响。分析表明:周向总压畸变使进口流场参数分布发生改变:在畸变与非畸变区的交界处有周向侧流产生,使进口的静压、气流轴向速度、气流角变得不均匀,从而改变了风扇的进口流场。总压畸变经风扇传递的同时引起总温畸变。通过对多种进口畸变条件下的风扇流场进行求解,提出刻画畸变区内转子旋转的“四阶段”模型。即动叶旋转一周主要经历进入畸变区、畸变区内运动、退出畸变区、非畸变区运动四个阶段。动叶在各阶段中受畸变流场的影响完全不同。畸变度和畸变角较大时,进口总压畸变对风扇流场的影响显著。本文采用更细致的网格对畸变度0.1,单畸变区90 o进口条件下的风扇流场进行了三维数值模拟。给出均匀和进口畸变条件下风扇的特性曲线。选取最高效率点作为研究对象,详细分析了进口畸变对风扇内部流场的影响。分析发现,进口总压畸变使风扇性能明显下降。畸变流场对动叶和静叶的影响沿径向存在很大差异。根部区域,动叶损失小,而静叶损失大。顶部则相反。不同周向位置畸变流场对动叶的影响不同。对于动叶,文中对不同周向位置、不同叶高处动叶内的流场进行了分析,给出相对畸变区不同周向位置处动叶内流场的变化规律。尤其对叶顶附近激波结构、强度、位置的变化进行了详细的分析。对于静叶,文中重点分析了畸变区内静叶的流场。结果表明,静叶根部存在大范围的分离,使畸变区内的静叶流道产生严重堵塞。从而影响到相邻叶栅内的流动状况,使流道内产生较强的激波。证实了动叶对不均匀流场的响应存在一定滞后:动叶在旋转过程中,当进口条件发生变化时,上游流体在动叶内传递需要一定时间才能影响到整个流道。最高损失点并不是在畸变区内,而是在动叶离开畸变区向远畸变区运动的过程中。相应的,转子最高效率(低损失)位置并不在远畸变区,而是位于动叶再次进入畸变区的位置。在原型的基础上构造了五种不同的静叶弯叶片方案对风扇流场进行求解。结果显示,静叶弯曲能有效提高抗畸变能力。在同样畸变度条件下,静叶采用弯叶片可以提高效率,可以提高风扇的流动稳定性。但是弯曲方式不同对风扇流场的改善方式也存在差异:静叶根部弯曲对动叶和静叶流场都有改善作用;两端弯曲对动叶的改善作用较大。本文将静叶弯曲对畸变流场的影响分为两个方向:一是大幅改善动叶流场,静叶栅效率却有所下降或改变不大;二是动叶效率改变不大,而对静叶流场的改善程度较大。流场的周向不均匀使畸变区静叶流道内产生严重分离。利用正弯叶栅产生的径向压力梯度,可以增加畸变区内静叶根部和中径区域的密流,从而在一定程度上抑制或减小分离的范围,能够改善畸变区内静叶以及上游动叶流场。但是静叶弯叶片的使用具有两面性。研究发现,两端大弯角的静叶能够较大程度提高动叶效率,使动叶内流动更稳定,同时能够提高静叶抗畸变能力,但是却使静叶栅效率下降;根部弯曲的静叶能够较大程度提高静叶栅效率,但是抗分离能力相对较低,同时对动叶改善相对较小。更多还原

【Abstract】 The main attention upon turbomachinery is performance improvement in 1960s, with little attention on stability decline induced by inlet distortion. But, as the increase of airplane flying speed and height and the enhancement of maneuverability, the impact on aeroengine by inlet distortion is more and more prominent. In the 21st century, aeroengine needs more unconventionally maneuverable and more supersonic flexible so that engine operates under distorted inlet condition, which deteriorates its performance, makes stability decline, even induces stall. The requirement to further increase performance and improve reliability in modern turbomachinery has motivated designers to better understand unsteady and inlet distortion effects in aeroengine flow field. So, deeply and systematically study of inlet distortion in a transonic fan is carried out in this paper.3D full-annulus unsteady numerical simulation and experiment results of a transonic fan are compared and analyzed. According to the computational condition applied in this dissertation, at the max efficiency point and near chock point, the results are very closely. But at the near stall point the results don’t match very well. It is analyzed and found that turbulence model error and larger numerical viscosity are the causes for such deviation. The further verification to simulation and experiment results shows that the numerical simulation method used in this dissertation can meet the requirements of qualitative flow field study in this transonic fan.With simulation of different distortion intensity and angles effects on the fan performance, distortion transformation forms of different inlet boundary condtions are given systematically. And parameters of inlet and outlet are analyzed in detail. It is found that circumferential total pressure distortion can change the distribution of inlet variables. There is circumferential flow at the border of distortion. Inlet static pressure, axial velocity and velocity angle are influenced and become non-uniform. An analysis model for rotor analysis in one revolution named“four phases model”is demonstrated. The model divided one revolution into four main phases according to the characteristic of rotor at different time slices. In each phase, the effects induced by distortion flow field on rotor are different.The effects on the fan flow field are more serious when distortion intensity is stronger and angle is biger. With the study of distortion intensity 0.1 and distortion angle 90 o,the fan performances with uniform and distorted inlet are given. The comparision of them shows inlet total pressure distortion reduces fan performance heavely. The max efficiency operation point is choosed and analyzed in detail. It is found that the effects on rotor and stator are very different at different spans and circumferential positons. In rotor, flow field variables at different spans and circumferential positons are analyzed in detail. Variation regularity of flow parameters when rotor rotates one revolution are decribed clearly. Especially, the variation of shock intencity and position at rotor casing area is analyzed in detail. In stator, the flow field in distorted region is analyzed. Results show large scope separation exists at stator hub. The separation makes these passages choked seriously. And the flow velocity in the next passages is supersonic.The reponse to inlet of rotor distortion having a lag is determined. In one revolution, it will take some time for inlet boundary to affect the full passage. The max loss point is not in the distorted region, but in the phase during rotor rotating from distorted region to remote distorted region. Accordingly, the max efficiency point is in the distorted region.The performance of fan with distorted inlet can be affected by varying the stator bow angle. Five stator bow angles are established in this dissertation. Results show that bowed stator can improve the fan performance effectively. Bow at hub can improve rotor and stator flow field, but bow at two sides has better effects on rotor. Use of positive bowed stator can constrain separation or reduce the scope and improve the stator flow field. But it has two faces. It is found that big bow angle at two sides can improve the rotor flow field and increase the rotor efficiency. And it can constrain the separation in distorted region better and enhance the anti-distortion capability of stator. But it reduces the stator efficiency. Bow angle at hub can increase the stator efficiency effectively. But its anti-distortion capability is low. And it has few good effects on rotor. So, there is an inner complex relation among bow angle, anti-distortion capability and stator efficiency.更多还原