【作者】 毛明明；

【导师】 王仲奇； 宋彦萍；

【作者基本信息】 哈尔滨工业大学 ， 动力机械及工程， 2008， 博士

【摘要】 压气机是航空涡轮发动机的关键部件之一,高推重比的发展方向对它提出了更高的要求。压气机部件的发展目标是以更少的级数达到更高的增压比,具有大的单位迎风面积流量、更高的效率和稳定工作裕度,同时具有更轻的重量和更少的零件数目。在压气机的设计中不断地出现新的技术难题需要研究解决,因此高负荷压气机的气动设计一直是航空发动机发展过程中所面临的挑战之一。弯、掠叶片技术是以全三维分析为基础的叶片设计,综合考虑弯、掠、扭的作用。采用掠形设计尤其是前掠叶片可以降低转子叶尖激波强度,通过弯曲叶片设计则可以改善端区流动,减小端壁损失,使叶片形状与流动更加适应,从而提高负荷能力和性能。弯、掠叶片技术作为控制端壁二次流和激波的重要手段,已经在压气机和风扇的提高效率和扩稳方面获得广泛应用。然而由于实验条件的限制,人们对弯掠叶片的作用机理认识不够全面,得到的结果也并不完全统一,因此对弯掠叶片在不同工况条件下的作用机理需要进一步探讨。基于这种认识,本论文对跨声速压气机动叶进行了详细的机理研究,并对非定常条件下动叶弯、掠后对尾迹输运、下游静叶静压的非定常扰动等影响进行了深入的分析。鉴于以往研究中前掠和正弯对压气机的失速裕度以及端壁流动的有利影响,对跨声动叶进分别行了详细的前掠和正弯的参数化研究,详细分析了弯/掠高、弯/掠角两个设计自由度对气动性能的影响。结果表明弯/掠叶片总效率都得到提高,而且较大的弯/掠高和弯/掠角更有利于叶顶性能的改善,对叶顶激波有更强的控制作用,但同时使动叶中部损失增加,尤其是弯/掠角的变化更容易加剧动叶中部性能的恶化。因此最终动叶改型设计采用大的弯/掠高和适当的弯/掠角。根据参数化研究结果得到利用正弯、前掠结合改善端壁流动,同时通过叶型重新设计控制中部损失的改型设计思想与原则,并据此对该跨声轴流压气机动叶进行了重新设计。设计思路是采用大的弯/掠高和适当的弯/掠角先对动叶进行弯掠结合改型,再通过减小弦长和增大转折角的方法重新设计动叶中部的三个截面叶型,从而削弱中部激波强度和分离损失。最终改型得到的弯掠动叶使得跨声压气机级的最大效率提高3%,同时失速裕度也由18%增加到了26%,小流量工况下压比也有所提高,总性能获得显著改善。在此设计中,中部叶型的优化设计是使弯掠叶片能够扬长避短,使总性能获得大幅提高的关键。现代叶轮机械的发展,在气动性能和可靠性方面提出了更高的要求,原先建立在相对简化的定常流动假设下的研究方法和设计手段已不能满足对叶轮机械更高性能指标的要求,因此深入的理解和研究流动的非定常效应有着非常重要的意义。鉴于目前叶片弯、掠在非定常条件下对邻近叶栅内流动状况、级效率影响的实验与数值研究还不多见,对动叶弯、掠后对级非定常流动的影响进行了数值研究。非定常计算条件下与原压气机相比,具有弯、掠动叶的压气机的效率和压比的波动规律的相位发生改变,这与弯、掠动叶出口处尾迹和势流的相位发生改变有关。在计算周期内的每个瞬时,弯、掠动叶压气机的效率仍然比原压气机大幅提高,并且波动幅值明显减小,这是因为弯、掠动叶降低了动叶出口上、下端壁的损失,从而增加了下游静叶径向进口条件的均匀性。非定常计算得到的弯、掠动叶压气机与原压气机的压比平均值变化不大,波动范围与效率相比也很小。由于三种弯、掠动叶出口尾迹的两端以及叶顶泄漏涡和根部分离区的脉动强度降低,而尾迹中部的脉动强度增加,这使得弯掠动叶下游的静叶前缘在两端部与原型压气机静叶相比受静压扰动的幅值明显减小,中部所受扰动则有所加剧,这使得静叶前缘非定常负荷的径向分布趋向均匀,更有利于叶片前缘强度的保证。除前缘以外的叶片表面范围内,三种弯、掠动叶下游的静叶叶片顶部静压脉动强度明显降低,而中部和根部的静压脉动没有明显变化,这是因为弯、掠动叶尾迹和根部高损失流体在下游静叶流道的传播中,与主流间的粘性掺混作用以及尾迹亏损的恢复作用使其脉动强度迅速降低,同时在静叶流道内径向压力梯度的作用下动叶尾迹内的低能流体倾向于向根部迁移,导致静叶流道中部和根部的流场在向下游的传播中迅速的趋于均匀。弯、掠动叶降低了对下游静叶气动负荷的非定常扰动,使静叶各气动负荷参数的波动幅值显著降低,尤其是气动力矩的波动幅值下降的最多。由于动叶弯掠后动、静叶所受到的非定常干扰都明显减轻,动、静叶频谱图中1倍频的幅值都明显减小。更多还原

【Abstract】 As one of the essential components of an aero-turbine engine, the compressor is developed reaching higher pressure ratio with less stages, larger mass flow at unit up-wind area, higher efficiency, larger stall margin and less weight and component amount to meet the demand of larger thrust-weight ratio of the engine. New technique problems appear continually in the compressor design process, thus the aerodynamic design of high-load compressor is always a challenge in the development of aeroengine.On the base of 3-D analysis, blade bowing and sweeping technique is to design blade considering the combined effects of bowing, sweeping and twisting. The sweeping technique, especially forward sweeping one has been employed to weaken tip shock of rotor. And the bowing technique has been applied to improve endwall flow condition, reduce endwall flow loss, and make the blade geometry more adaptive to the flow, consequently to increase work ability and performance of the blade. As important means to control endwall secondary flow and shock wave, blade bowing and sweeping technology have been widely applied in compressors and fans to achieve higher efficiency and larger stall margin. However due to the deficiency of experiment, the knowledge of acting mechanism of bowed and swept rotor is still limited. Thus detailed parametric researches on such mechanism of bowed and swept rotor in a transonic compressor are carried out, and the effects of rotor bowing and sweeping on the wake transportation, the pressure fluctuation at downstream stator surface, the interaction of rotor and stator, and stage performance are detailedly analysed.Since studies have shown that forward sweep and positively bow are able to increase stall margin and improve endwall flow of compressor, parametric researches on forward sweep and positively bow applied in a transonic rotor are done, and the effects of two parameters, bow/sweep height and bow/sweep angle, on the performance are detailedly analyzed. Results show that the efficiency is improved with both design techniques. It’s also shown that larger bow/sweep height or bow/sweep angle, which is profitable to tip flow condition, is harmful to mid performance, and such adverse effect is more evident when increasing bow/sweep angle. Hence a large bow/sweep height and a moderate bow/sweep angle are adopted in the final rotor modification.Based on the achievement of parametric researches, a principle for rotor modification is obtained. The principle includes large bow/sweep height, moderate bow/sweep angle, and redesigning three sections at rotor central part by reducing chord length and increasing turning angle to weaken shock intensity and decrease separation loss there. The modified rotor with such principle is with increased efficiency by 3%, improved stall margin form 18% to 26%, and higher pressure ratio at small mass flow condition. Therefore, an obvious compressor compressor performance is obtained. The successful modification also proves the essential role of mid sections optimum design on applying bow/sweep technique in rotor design to improve compressor performance.The development of nowadays turbomachine put forward increasing requirement of high aerodynamic performance and reliability, which challenges the traditional design and research technique on the basis of simplified steady flow assumption, thus advanced technique is in developing. The advanced technique, otherwise, relates to detailed research and deep understanding of unsteady effect. In the present paper, numerical simulations on the effects of the bowed and swept rotor on the unsteady flow field in a single stage axial compressor are carried out. Compared to the baseline, the phases of the time-dependent stage efficiency and total pressure ratio fluctuation wave are shifted as a result of the phase shift of the rotor wake and the potential flow in the compressor with bowed or swept rotors. The stage efficiency is remarkably increased and the fluctuation amplitude is evidently reduced because the curved rotor lowers the endwall loss and increases the radial uniformity of the inlet boundary condition of the downstream stator.In comparison with the baseline, in the curved rotor stage, the amplitude of the static pressure fluctuation decreases at the two endwalls, but increases at mid-span near the leading edge of the stator. The radial distribution of the unsteady blade loading is more uniform, which is beneficial for guaranteeing the intensity of the blade leading edge. Downstream the curved rotor, except for the stator leading edge area, the amplitude of the static pressure fluctuation decreases in the tip region of stator surface, but undergoes no obvious changes in the middle and at the hub. This is ascribed to that, in the curved rotor stage, the dissipation of the rotor wake at mid-span is slower than that at the two endwalls, and the rotor wake moves towards the hub under the influence of radial pressure gradient during the downstream migration.Bowed and swept rotors reduce the unsteady disturbance on the aerodynamic loads of downstream stator, so as to decrease the fluctuation amplitude of aerodynamic loads parameters, especially that of aerodynamic moments. And the amplitude of 1.BPF falls obviously in the frequency spectrum of aerodynamic loads of rotor and stator, due to lightened unsteady rotor/stator interaction.更多还原