端壁采用孔式抽吸对扩压叶栅气动性能的影响

为明晰孔式附面层抽吸技术对压气机叶栅气动性能的作用效果,实验研究了在端壁不同位置设置抽吸孔时对大折转角扩压叶栅壁面流谱、出口二次流及损失的影响。研究结果表明,端壁抽吸改变了原型叶栅内部流场结构,角区分离起始点前进行附面层吸除可有效延缓通道涡的形成,降低叶栅损失;分离起始点之后角区分离已经充分发展的位置不宜布置抽吸孔;相比较抽吸槽,采用抽吸孔可以通过更少的抽吸量达到相同程度地对叶栅流动性能的改善。      

端壁附面层抽吸对大转角扩压叶栅旋涡影响的实验研究

为探明附面层抽吸技术对压气机叶栅气动性能的影响及其与栅内旋涡结构的关联,通过十个横截面的实验测量结果研究了高负荷压气机叶栅抽吸端壁附面层前后的主要旋涡结构以其对应损失的演变过程。研究对象为矩形低速扩压叶栅,来流马赫数约为0.23。研究结果表明,端壁附面层的变化对叶栅端区的主要旋涡发展过程影响显著。在原型方案中,壁面涡、尾缘脱落涡的演变过程对应着较高的流动损失,通道涡自身产生的损失较小,主要起到向远离端壁的方向输运低能流体的作用;在流向槽吸气方案中,壁面涡和尾缘脱落涡因端壁附面层径向迁移及角区分离受到抑制而被明显削弱;而来流附面层抽吸方案则最为有效地控制了通道涡的演变过程。      

基于主/被动联合控制技术设计的高负荷扩压叶栅内部流场结构研究

为进一步优化设计工作做准备,以基于主/被动联合控制技术设计的高负荷扩压叶栅作为研究对象,在进口为高亚声速的条件下,利用数值模拟的方法,详细研究了冲角变化对扩压叶栅壁面流谱以及气动损失的影响。结果表明,负冲角下,后列叶栅内部存在较大尺度的角区分离流动,构成叶栅损失的主要来源;随着冲角增加,流经串列叶栅近端壁处缝隙流道内流体的相对动量增强,后列叶栅角区分离流动受到抑制,端区二次流动损失降低,+3°冲角下,上、下20%叶展区域内总压损失分别降低了4.4%、6.8%,但前列叶栅叶型分离流动加剧,主流区损失增加;合理协调端壁附面层抽吸技术与串列叶栅技术的应用是提升高负荷扩压叶栅全工况气动性能的关键。     

槽道射流及端壁抽吸对角区分离的组合控制研究

为优化叶片吸力面流动分离结构,探究对于角区分离更好的流动控制方法,以一大弯角扩压静子叶栅为研究对象,对叶片进行全叶高槽道结构处理,并在其基础上于槽道出口前进行端壁抽吸槽结构处理。在来流马赫数为0.7,来流攻角为-8°～6°工况下,对原型叶栅、全叶高开槽叶栅及组合流动控制叶栅进行性能计算及对比。结果表明：全叶高开槽方案能有效消除叶片吸力面叶中附面层分离,抑制角区分离,减小原型叶栅的总压损失,提高扩压能力。对比全叶高开槽方案,组合流动控制方案能更有效地抑制端壁二次流于槽道出口前在吸力面上的发展,进一步消除角区分离,优化近端壁区流场。因此,端壁抽吸加全叶高槽道射流的组合流动控制方案对于宽来流攻角范围具有更强的适应性,从而更有效地减小原型叶栅的总压损失,拓宽其可用攻角范围,提高叶栅的扩压能力。     

高负荷扩压叶栅中附面层吸除技术实验研究

通过分析某高负荷压气机叶栅内部的流动状况,确定了端壁开槽吸气以及端壁与吸力面同时开槽吸气两种附面层吸除方案,并在低亚声速条件下进行了风洞吹风实验。结果表明,附面层吸除是一种提高高负荷压气机叶栅气动性能的有效措施,通过吸走附面层流体可以改善壁面附近流动状况,角区分离减弱,流道内高损失区范围减小。随着吸气量的增加,改善压气机叶栅性能的效果越显著。吸气方案不同,其作用机理也不一样。     

下端壁流向槽抽吸对高负荷扇形扩压叶栅性能影响的数值研究

为探究附面层抽吸对亚声速高负荷扇形扩压叶栅气动性能和流场结构的影响,利用数值方法对叶栅进行了下端壁流向槽附面层抽吸的研究。对比原型和各抽吸方案发现:下端壁附面层的抽吸可以有效抑制下角区低能流体的分离及回流,降低下角区总压损失并提升叶栅近端壁区域的扩压能力,但上角区分离会略有加剧。当抽吸质量流量为原型叶栅质量流量的0.50%时,抽吸槽起始于角区分离点下游附近的抽吸方案(EW2)效果最佳,叶栅整体总压损失降低27.65%,静压比提升8.69%。     

高负荷压气机叶栅等离子体流动控制数值仿真与拓扑分析

为揭示叶栅等离子体流动控制的影响规律与作用机理,对等离子体气动激励前后高负荷压气机叶栅内部流动和拓扑结构进行了对比研究。结果表明:等离子体气动激励抑制叶栅流动分离的作用效果最明显的区域位于总压损失区域与主流区域的边界上;不同等离子体气动激励布局,对固壁面拓扑结构以及奇点总数的影响规律不同;吸力面流向激励通过增强附面层流体抵抗逆压梯度的能力,可以改善叶栅中间叶高流动特性;端壁横向激励通过抑制横向流动,抑制角区流动分离能力较强,并改变叶片展向的负荷分布;组合激励结合了吸力面流向激励和端壁横向激励的作用优势,因而提高叶栅气动性能、降低流动损失的效果最好。      

附面层抽吸对高负荷扩压叶栅气动性能影响的实验研究(英文)

对某大转角压气机叶栅进行了实验研究,以验证应用附面层吸气技术改善高负荷叶栅气动性能的效果。测量流场,并进行了流场显示。结果表明基于本文采用的附面层抽吸方式,各吸气方案下中径处的损失减小最为显著。只有在附面层已经分离但是还未远离避免的位置进行抽吸,端壁损失才明显地减小。随着吸气量增加和吸气位置后移,改善的程度增加,总压损失降低幅度最高达16.5%。附面层抽吸位置对总压损失的影响比抽吸量大。     

端壁抽吸控制下攻角对压气机叶栅叶尖泄漏流动的影响

为减少叶尖泄漏损失并改善由泄漏涡造成的叶尖流道堵塞,对端壁流向开槽抽吸方案对扩压叶栅叶尖泄漏流动的控制效果进行了数值模拟研究,重点分析了来流攻角对流动控制效果的影响。结果表明:端壁抽吸方案通过直接影响叶尖泄漏流的发展,减弱泄漏涡强度,减小了泄漏损失;抽吸对负攻角和小攻角下叶栅流场的影响范围仅局限于叶尖区域。但在大的正攻角下,抽吸使得低叶展区域的附面层分离提前,且叶背分离涡脱落位置升高至约70%叶高处,端壁抽吸对叶栅的整体影响由泄漏损失降低和分离损失增大综合决定。抽吸量为07%时,抽吸后叶栅总体总压损失系数分别在-8°、0°和+4°攻角下降低约90%、108%和68%,而在+8°攻角下增大约57%。     

端壁抽吸位置对大转角扩压叶栅流场及负荷的影响

实验研究了低速条件下在端壁近吸力面处进行附面层吸除对某大转角扩压叶栅性能的影响.对叶栅出口截面参数和叶片型面静压进行了测量,并在叶片表面及端壁进行了墨迹流动显示.结果表明,端壁抽吸主要影响了吸力面/端壁角区,重新分配叶片根部负荷.在角区未发生分离的位置开始抽吸可有效推迟叶栅内的角区分离,降低损失,改善叶栅端区流动;而在角区已经发生分离的弦向位置开槽吸气则引起了局部回流,恶化了流场,增加了低能流体的掺混和气动损失.     

从科技论文的特点看科技论文的选题

本文论述了科技文的特点及选师原则。在特点方面主要就科技论文的科学性,创造性,理论性进行了阐述,在选题方面科技论文选题的客观需要与主条件进行阐述,旨在揭示科技论文的特点与课题选择之间的关系,从而了解其特点,并据此选题,写出符合要求的科技论文。     

某任务计算机调试设备配套软件的设计与实现

简介了任务计算机调试设备配套软件在任务计算机仿真环境中的重要作用 ,对该软件设计方法和流程进行了详细的说明 ,主要介绍了VC ++6 .0环境下串行通信和显示控制软件的设计技术 ,并讨论了如何提高应用程序性能的途径。     

Analysis of a redshifted plasma flow over a sunspot

The ultraviolet spectrum of a redshifted plasma flow appearing over a sunspot observed during the first flight of the High Resolution Telescope Spectrograph (HRTS I) is analysed, and interpreted as a radiatively cooling plasma. For most of the lines emitted from this plasma, the assumption of ionization equilibrium during the cooling is good. However for He II (and other ions with a single electron outside of closed shells), this is not the case. Integrating differential equations for the various ionization fractions of helium and the temperature allows an approximate determination of the abundance of helium relative to other elements whose lines appear in the spectrum of the plasma flow.     

Effect of a transverse plasma jet on a shock wave induced by a ramp

We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2 mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found: the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation(IDDES) method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets.     

Oscillations of a viscous liquid in a cylindrical container

The natural damped frequencies of a viscous liquid in a circular cylindrical container are obtained for slipping and anchored contact line at the container wall r = a. In addition the response to translational forced excitation has been determined. The results may also be applied to viscous liquid in a micro-gravity environment, as long as the contact angle of the liquid surface to the cylindrical container wall is in the vicinity of π/2, indicating, that the free liquid surface equilibrium position remains a plane surface. It could be found that there exists in contrast to frictionless liquid a small filling range, in which the liquid performs only an aperiodic motion. The adherence condition at the side wall was replaced by the somewhat weaker condition of an anchored contact line.     

Impact of a cavitation bubble on a wall

Impulse action of a cavitation bubble on a rigid wall is studied depending on the distance between them. We determine the distances at which the periphery pressure maximums on a wall are preserved as well as the distances at which these maximums exceed the water hammer pressure.     

Flow about a jet source with a deflector

We suggest a method to solve one of the model problems of aerohydrodynamics, namely, a problem of a flow about a point source, from which a fluid with density and total pressure, different from the corresponding values in the incoming flow enters. The calculations are carried out for various values of the determining parameter; and the data are compared with the known results. We revealed the advantages of the suggested method in comparison with the known ones.     

Solving a radiation problem with forward speed using a lifting surface method with a Green''s function

The progress of seakeeping computations requires development of computating codes for unsteady flows around a ship or its elements. In this paper, we present a method of calculation concerning waves radiated by an oscillating surface-piercing flat plate with forward speed, with a yaw angle. By use of Green's third identity, the problem is transformed into the resolution of a Fredholm integral equation of the first kind by a panel method using Green's function. The Green's diffraction-radiation function with forward speed is used. Its numerical values are calculated by an adaptative integration procedure to reduce the computation time. The present method permits determination of the pressure jump distribution across the plate, the total forces and moments. The results obtained are compared with other numerical methods in hydrodynamics and in aerodynamics, and with experimental data obtained in a water tank.     

Relativistic Energy-Momentum of a Body with a Finite Volume

The problem of energy-momentum in a body with a finite volume has been causing confusion in the theory of relativity, especially in relativistic thermodynamics. Its correct understanding has been given since the early years of relativity, however, erroneous misunderstandings are still found in papers and textbooks to this date. The present paper introduces a simple paradox to demonstrate the problem, and gives a brief review on a way to handle the energy-momentum correctly.     

The intersection of a Loxodrome with a great circle

The intersections of a loxodrome (rhumb line) and a great circle are of interest for some navigational problems, but a closed-form solution cannot be formulated. An algorithm is given for computing approximations to any desired degree of accuracy using Newton's method. By using the equatorial angle φ as an independent variable all solutions can be found rapidly using the modest computational capabilities of a personal computer