【作者】 刘雷；

【导师】 陈浮；

【作者基本信息】 哈尔滨工业大学 ， 动力机械及工程， 2015， 博士

【摘要】 自上世纪中叶以来,随着人类对航空飞行器尤其是导弹和军用飞机生存能力要求的不断提高,S弯进气道因其隐身性好、结构紧凑、便于维修等诸多优点,受到国内外学者广泛关注并被逐渐投入使用。然而,其出口畸变通常较大,对工作其后的气动部件极为不利。因此,深入研究该类进气道内部流动特性、出口畸变形成机理以及对后续部件气动性能、流场结构影响,对于改善其后气流流动乃至提高整个发动机气动性能、拓展其应用范围都具有重要意义。目前,有关S弯进气道的研究大多单独针对进气道,而将S弯进气道与其后风扇或压气机作为整体研究的相对较少。为此,本文首先针对某小型涡扇发动机风扇级,设计一半埋入式S弯进气道并对其进行几何结构优化。鉴于结构优化对进气道内部流动改善幅度有限,进一步对优化后进气道进行了吹、吸气流动控制研究。分析发现,吹气位置变化显著影响吹气控制效果,气流分离点之前吹气后分离起始位置后移,分离区域内吹气,则在分离点与吹气点之间出现小范围气流分离,吹气点之后分离气流重新附着。第1弯底部吹气可抑制“对涡”雏形生成和流动分离发生,为最佳吹气位置。为避免吹出的气流与进气道内主流发生掺混,吹气量不宜过大,吹气角需尽量保证吹出的气流始终位于附面层内。喉部吸气既可使其后较大范围的流场受益,又可较好地抑制“对涡”雏形形成和流动分离发生,为最佳吸气位置。吸气角的选择需综合考虑附面层内气流方向、主流方向以及附面层厚度。优选出最佳吹、吸气方案的基础上,将两者组合实施吹吸气组合流动控制,发现其效果并非单独吹气和单独吸气时对应效果的简单叠加,该方案下进气道气动性能提高幅度最大。考虑到进气道出口畸变严重,对风扇级不利,分别将优化和流动控制前后进气道与风扇级对接作为一个整体进行了一体化数值研究。结果表明进气道出口是否接风扇级,对其数值研究结果影响较大,尤其是对进气道出口周向总压畸变和旋流畸变的影响。进气道出口畸变作用下,风扇级气动性能显著下降,进气道优化后风扇稳定工作范围略有增加。进气道内施加流动控制后风扇性能得到进一步提升。其中,吸气时对应改善幅度最小,效率最大值增加约0.57%。吹气时效率最大值增加约2.26%,该点对应增压比增加约1.20%。吹吸气组合流动控制之后,改善幅度最为明显,效率最大值、最大增压比分别增加约2.70%和3.13%。受动叶旋转影响,进气道出口截面底部低能流体在发展至风扇动叶入口的过程中所占面积逐渐减小,至动叶入口覆盖底部约三个流道;进入风扇后,畸变流体始终覆盖多个流道,相对于其它均匀流道,这些流道内气流总压和速度较小。优化和流动控制后,畸变流体所覆盖流道数量减小,且畸变流道内的总压和气流速度都稍有增强;在入口气流攻角改变和下游逆压梯度的综合作用下,静叶吸力面上出现严重的气流分离。但分离现象主要发生在50%叶高以下位置,且优化和流动控制之后分离现象有所减弱。最后,基于上述研究,以风扇级静叶内高能气流作为进气道内吹气流动控制气源,进行了带引气管路的风扇级入口畸变控制研究。结果表明引气管路自身结构以及安装位置、角度、引气量、所引气流品质等对引气控制效果影响较大。轮毂位置引气后,静叶畸变流道内低能流体被部分吸除,吸除的气流在进气道内吹出后进气道内流动状态略有改善,风扇整体性能得到提高。机匣位置引气时,风扇级的稳定工作范围明显增加,当风扇工作点靠近喘振边界时,引气控制起到显著积极作用,而靠近设计点或者堵塞边界时引气反而会导致风扇级气动性能下降。引气系统采用类似于放气活门一样的工作方式工作时,不仅能保证风扇级稳定工作范围增加,还能维持其最高效率点附近整体特性。更多还原

【Abstract】 As we know, along with the demand of missile and military aircraft survivability increases since the middle of last century, the S-shaped inlet receive widespread attention thanks to their simple structure, small frontal area and favorable stealthy performance. However, the inlet distortion which is harmful to the rear aerodynamic components is usually serious, especially the half flush-mounted and the submerged S-shaped inlet with large boundary layer ingestion. So the deep study of the internal flow characteristic, the exit distortion formation mechanism of S-shaped inlet and its impact on subsequent components’ aerodynamic performance and flow field, is of great significance to expand the S-shaped inlet application scope, to improve the flow field structure, and even to enhance the whole engine’s dynamic performance. Now most of design philosophies tend to treat the S-shaped inlet as an isolated component, and few work taking it and the rear compressor as a whole has been reported.In this paper, for giving a real exit boundary, and also for investigating the impact of S-shaped air intake exit distortion on the rear fan stage performance as well as its evolution process in the rear components, a half flush-mounted airintake has been designed first for the fan-stage of an small turbofan engine. In view of improvement of the airintake aerodynamic performance is limited after optimization, further study of airintake internal flow control such as blowing or suction has been conducted. Due to high energy fluid injected into, the ability of low-energy fluid in the boundary layer to overcome inverse pressure gradient increases, the separation point moves backward if the high energy fluid is injected before the original separation point. More injected mass flow, more move back quantity until the flow separation disappeared at last. While blowing in the original separation region, small scale flow separation only appears in the region between the original separation point and the blowing location, and the separated flow that behind the blowing location reattached again. The location selected for blowing has significant influence on the final effect. Blowing at the first curved bottom can inhibit the generation of the vortex embryonic as well as the flow separation, so undoubtedly the 1st bend that just before the separation point is the best blowing location. For avoiding the high-energy air from pipes mix with mainstream in the airintake, the blowing mass flow should not be too large, and little blowing angle should be selected for ensuring the blown fluid is always in the boundary layer. When suction proceeds at the throat location, a wide range of backward flow field will be profited, simultaneously, formation of the vortex embryo and the flow separation can be restrained. Considering this two aspects, throat is the optimal suction location. And the suction angle design need to consider the boundary layer fluid movement direction, the mainstream movement direction and the boundary layer thickness. Combinational flow control effect is not the simple superposition of the single blowing control effect and the single suction control effect, but is the largest one among the three.Taking into account the airintake exit distortion is serious and very detrimental to the fan stage. Numerical investigation of the whole structure of the airintake that before and after optimization or flow control and the fan-stage has been conducted, for investigating the impact of S-shaped air intake exit distortion on the rear fan stage performance as well as its evolution process in the rear components. Giving a real exit boundary or not has significant impact on the airintake numerical simulation results, especially to the circumferential total pressure distor tion and the swirl distortion. The total pressure ratio as well as the efficiency of the fan stage decreases dramatically due to substantial boundary layer ingesting, after optimization, the stable operation range is extended significantly. With flow contr ol, the overall performance of the fan-stage further improves significantly. The maximum isentropic efficiency of the fan-stage increase about 0.57% with suction control while increase about 2.26% with blowing control. As to the combinational flow control, the maximum isentropic efficiency and the maximum total pressure ratio of the fan-stage increase about 2.70% and 3.13% respectively. Under effect of rotating rotor, the significant low energy region at bottom of the inlet exit decreases ceaselessly when it developing backward to front-edge of the rotor blade, moreover, the high-energy fluid mixes with the low-energy fluid. This phenomenon always exists no matter the optimization or the suction control proceeded or not, while disappears under the best blowing scheme or the combination scheme. The distorted low energy fluid covers several blade passages when it goes through the fan-stage. The relative total pressure and velocity of the fluid in these distorted blade passages is obviously less than that in other passages, which has a little increase after optimization or flow control. Meanwhile, after airintake optimization and internal flow control, the region covered by this distorted fluid has a little decrease. Serious flow separation occurs in the stator blade suction sides. But this flow separation mainly occurs at 50% stator blade span and below, and weakens after optimization or flow control has been carried out.Finally, based on the above study, the flow control with bleeding pipe as flow control device and high energy fluid in the stator cascade as bleeding air source has been researched. Bleeding pipe structure, installation position and angle are all very crucial to the flow control effect. More bleeding mass flow does not mean better, and quality of the bleeding air jet is the key. After bleed air from the stator hub for blowing control, the whole performance of the fan-stage improves a lot when it works under the condition that between the maximum efficiency point and the stall margin, due to the low energy fluid in the stator cascade being partly sucked and then blowing in the airintake to improve the airintake exit air quality. The stable operation range extends significantly as bleed air conducted at the stator shroud and the bleed air pipe diameter equal to each other. The control effect of this scheme is much better when the fan-stage working near the surge margin than when it working at the maximum efficiency point or near the blocking margin. So, if the bleed air system can work like a bleed valve rather than always in work state, the stable operation range as well as its aerodynamic performance improves substantially.更多还原