高压涡轮采用非轴对称端壁的研究

以某型高压涡轮第二级静叶为研究对象,对四种非轴对称端壁造型状况下涡轮叶栅的流动状况进行数值模拟,研究非轴对称端壁造型技术在高压涡轮中对流动产生的影响。将非轴对称端壁与轴对称端壁的计算结果对比分析,结果表明：在该型涡轮设计工况下,非轴对称端壁的应用可以明显减弱端壁处的横向压力梯度,降低出口截面处的绝对螺旋度,减少主流与二次流之间的掺混,同时使得出口气流角沿叶高分布更加均匀,改善下游动叶入口的气动条件。     

A Simple Method of Flow Field Diagnosis in Multistage Axial Flow Compressors

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Investigation of non-axisymmetric endwall contouring in a compressor cascade

The current paper presents experimental and computational results to assess the effectiveness of non-axisymmetric endwall contouring in a compressor linear cascade. The endwall was designed by an endwall design optimization platform at 0° incidence(design condition). The optimization method is based on a genetic algorithm. The design objective was to minimize the total pressure losses. The experiments were carried out in a compressor cascade at a low-speed test facility with a Mach number of 0.15. Four nominal inlet flow angles were chosen to test the performance of non-axisymmetric Contoured Endwall(CEW). A five-hole pressure probe with a head diameter of 2 mm was used to traverse the downstream flow fields of the flat-endwall(FEW) and CEW cascades.Both the measured and predicted results indicated that the implementation of CEW results in smaller corner stall,and reduction of total pressure losses. The CEW gets 15.6% total pressure loss coefficient reduction at design condition, and 22.6% at off-design condition(+7° incidence). And the mechanism of the improvement of CEW based on both measured and calculated results is that the adverse pressure gradient(APG) has been reduced through the groove configuration near the leading edge(LE) of the suction surface(SS).     

透平叶栅非轴对称端壁优化目标比较

基于双控制曲线和改进的Kriging代理模型建立了非轴对称端壁优化设计系统.以Durham叶栅的端壁优化为例,研究不同优化目标对优化结果的影响.研究表明:在通道涡形成段减小横向压力梯度可以有效抑制通道涡强度,进而减小流动损失;在通道涡发展段减小横向压力梯度有助于降低主流区二次流损失,但端区损失明显增大;增加横向压力梯度...     

最近十年叶轮机械最优设计的一些进展

本文介绍了最近十年中径、轴流式燃气透平和蒸汽透平、压气机、通风机、叶轮泵和水轮机等叶轮机械热(水)力性能和结构最优设计方面的一些进展,并给出了丰富的文献目录。     

Experimental Investigation of the Three—Dimensional Flow in an Annular Compressor Cascade at Large Incidence

This paper presents a detailed experimental investigation concerning the influence of blade loading (incidence)on the three-dimensional flow in an annular compressor cascade.The data are acquired at four incidence anglesunder low Mach number and low Reynolds number conditions.Experimental techniquss include the oil-filmvisualization on the profile and the endwall surfaces,the laser-sheet visualization of the flow field inside theblade passage,and the measurement by radial-circumferential traveress using a seven-hole probe.The behaviorand nature of the three-dimensional flow with severe separations inside the blade passage and at the exit areobtained.The distributions of the total pressure loss,static pressure,velocity and outflow angle are also given.These results are valuable for establishing the physical model of the three-dimensional complex flow in axialcompressors and for examining the computational procedures.     

向心涡轮可调导向叶栅内流动损失机理的分析

通过对向心涡轮可调导向叶栅三维流场数值模拟,分析在不同叶片安装角下,可调叶片表面静压系数和出口总压损失系数的变化规律。导叶安装角从21°增加到44°,通流面积调节范围为50%～116%设计通流面积。结果表明:叶栅开度减小时,叶片的气动负荷增加,总压损失增加。与设计工况相比,导叶关小15°总压损失增加了1倍多。叶栅端部间隙增加了导向叶栅的流动损失,间隙增加2%,损失增加1.5%,端部损失范围从20%叶高增加到40%叶高。叶栅开度减小,端部损失与叶型损失的变化较小,而间隙损失无论是数量还是占总压损失的比重都明显增加,是非设计工况下总压损失增加的主要原因。     

Experimental and numerical investigation on compressor cascade flows with tip clearance at a low Reynolds number condition

High flow rate aeroengines typically employ axial flow compressors,where aerodynamic loss is predominantly due to secondary flow features such as tip leakage and corner vortices.In very high altitude missions,turbomachinery operates at low density ambient atmosphere,and the recent trend toward more compact engine core inevitably leads to the reduction of blade size,which in turn increases the relative height of the blade tip clearance.Low Reynolds number flowfield as a result of these two factors amplifies the relative importance of secondary flow effects.This paper focuses on the behavior of tip leakage flow,investigating by use of both experimental and numerical approaches.In order to understand the complex secondary flow behavior,cascade tests are usually conducted using intrusive probes to determine the loss.However relatively few experimental studies are published on tip leakage flows which take into account the interaction between a rotating blade row and its casing wall.Hence a new linear cascade facility has been designed with a moving belt casing in order to reproduce more realistic flowfield as encountered by a rotating compressor row.Numerical simulations were also performed to aid in the understanding of the complex flow features.The experimental results indicate a significant difference in the flowfield when the moving belt casing is present.The numerical simulations reveal that the leakage vortex is pulled by the shearing motion of the endwall toward the pressure side of the adjacent blade.The results highlight the importance of casing wall relative motion in analyzing leakage flow effects.     

基于试验数据的轴流压气机喘振边界经验预估方法

从压气机特性计算统计法的基本思想出发,对多台轴流压气机喘振试验数据进行了整理分析,总结了同类型压气机喘振边界上参数变化的一般规律,在此基础上,将压气机设计转速下的喘振参数与其非设计转速下的喘振参数进行相互关联,提出了一种基于试验数据的轴流压气机喘振边界经验预估方法.通过与试验结果的详细对比.表明本文所建立的经验方法能够...     

非轴对称端壁抑制叶栅二次流分离的实验研究

应用热线测量和颗粒图像测速(PIV)技术,测量平端壁叶栅(FEW)和非轴对称端壁叶栅(CEW)的二次流动。基于叶栅内的涡结构和剪切应力,分析非轴对称端壁降低二次流损失的流动机理。实验结果表明:二次流在叶片吸力面的边界层分离导致壁面涡与主流流体的剪切掺混,这是叶栅二次流损失的主要来源;非轴对称端壁通过降低端壁横向压力梯度推迟二次流分离的发生,使壁面涡与主流区产生剪切掺混的范围缩小,并使端壁二次流的流向速度提高、壁面涡的强度降低,在上述两方面作用下叶栅内的剪切应力减小,叶栅二次流损失降低。     

An Experimental Study on 3—D Flow in an Annular Cascade of High Turning Angle Turbine Blades

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Investigation of endwall flow behavior with plasma flow control on a highly loaded compressor cascade

To discover the flow behavior in the endwall region and mechanism of plasma flow control on a highly loaded compressor cascade, distributions of static pressure coefficient, total pressure loss coefficient and streamline pattern were investigated. Results show that cross flow from the pressure surface to neighboring suction surface exists under pitch-wise pressure gradient. The deflected endwall boundary layer flow interacts with the incoming flow, and then both of them leave off the endwall in the form of a span-wise vortex. Effect of angle of attack on static pressure is greater than that of free stream velocity. The distinct variations of total pressure loss with endwall actuations are mainly located within the outer verge of a triangular area with high total pressure loss. Effect of pitch-wise actuation on separated flows is much better than that of stream-wise actuation, and both enhance with the increase of angle of attack and actuation strength. An efficient method for plasma flow control in the endwall region is the increase of actuation strength, such as adjusting discharge voltage or changing plasma power supply.     

Turbine endwall film cooling with combustor-turbine interface gap leakage flow: Effect of incidence angle

This paper is focused on the film cooling performance of combustor-turbine leakage flow at off-design condition. The influence of incidence angle on film cooling effectiveness on first-stage vane endwall with combustor-turbine interface slot is studied. A baseline slot configuration is tested in a low speed four-blade cascade comprising a large-scale model of the GE-E³Nozzle Guide Vane (NGV). The slot has a forward expansion angle of 30 deg. to the endwall surface. The Reynolds number based on the axial chord and inlet velocity of the free-stream flow is 3.5 × 10⁵ and the testing is done in a four-blade cascade with low Mach number condition (0.1 at the inlet). The blowing ratio of the coolant through the interface gap varies from M = 0.1 to M = 0.3, while the blowing ratio varies from M = 0.7 to M = 1.3 for the endwall film cooling holes. The film-cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique. The results show that with an increasing blowing ratio the film-cooling effectiveness increases on the endwall. As the incidence angle varies from i = +10 deg. to i = ?10 deg., at low blowing ratio, the averaged film-cooling effectiveness changes slightly near the leading edge suction side area. The case of i = +10 deg. has better film-cooling performance at the downstream part of this region where the axial chord is between 0.15 and 0.25. However, the disadvantage of positive incidence appears when the blowing ratio increases, especially at the upstream part of near suction side region where the axial chord is between 0 and 0.15. On the main passage endwall surface, as the incidence angle changes from i = +10 deg. to i = ?10 deg., the averaged film-cooling effectiveness changes slightly and the negative incidence appears to be more effective for the downstream part film cooling of the endwall surface where the axial chord is between 0.6 and 0.8.     

Influence of non-axisymmetric terms on circumferentially averaged method in fan/compressor

The governing equations are derived by circumferentially averaging the three-dimensional(3D) Navier-Stokes equations,which are solved using a time marching finite volume approach.Both Euler throughflow model and Navier-Stokes(N-S) throughflow model are employed to investigate the performance and flow fields of a highly loaded transonic single-stage fan ATS-2 and a four-stage fan.The results are compared with the experimental and three-dimensional computational results.It shows that the throughflow models can provide reasonable performance characteristics and N-S throughflow model gives better predictions in endwall regions.A throughflow computation n in which all the non-axisymmetric terms are included has been performed at off-design condition and the radial distributions of the flow field can be well described.     

中等折转角涡轮直叶栅端壁流场结构和涡系效应的分析

应用商用软件Fine/Turbo对一中等折转角涡轮直叶栅的流场进行了数值模拟,清晰地捕捉到了叶栅端壁处叶片前缘的马蹄涡及其吸、压力面分支,对马蹄涡的吸、压力面分支的相互作用过程和通道涡的发生发展过程给出了较为清晰的描述,获得了较为详细的叶栅端壁处二次流流动结构。通过对叶栅流道中各个近似垂直于流动方向的截面上的总压分布图的分析,揭示了在上述各个截面上端壁区域流动损失产生的机理。     

Power and efficiency optimization for combined Brayton and inverse Brayton cycles

A thermodynamic model for open combined Brayton and inverse Brayton cycles is established considering the pressure drops of the working fluid along the flow processes and the size constraints of the real power plant using finite time thermodynamics in this paper. There are 11 flow resistances encountered by the gas stream for the combined Brayton and inverse Brayton cycles. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, combustion inlet and outlet, turbine outlet of the top cycle, turbine outlet of the bottom cycle, heat exchanger inlet, and compressor inlet of the bottom cycle. These resistances control the air flow rate and the net power output. The relative pressure drops associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle. The analytical formulae about the relations between power output, thermal conversion efficiency, and the compressor pressure ratio of the top cycle are derived with the 11 pressure drop losses in the intake, compression, combustion, expansion, and flow process in the piping, the heat transfer loss to the ambient, the irreversible compression and expansion losses in the compressors and the turbines, and the irreversible combustion loss in the combustion chamber. The performance of the model cycle is optimized by adjusting the compressor inlet pressure of the bottom cycle, the air mass flow rate and the distribution of pressure losses along the flow path. It is shown that the power output has a maximum with respect to the compressor inlet pressure of the bottom cycle, the air mass flow rate or any of the overall pressure drops, and the maximized power output has an additional maximum with respect to the compressor pressure ratio of the top cycle. When the optimization is performed with the constraints of a fixed fuel flow rate and the power plant size, the power output and efficiency can be maximized again by properly allocating the fixed overall flow area among the compressor inlet of the top cycle and the turbine outlet of the bottom cycle.     

Experimental investigation of the influence of blade height and blade number on the performance of low head axial flow turbines

Investigations regarding the influence of design parameters in low head axial flow turbines like blade profiles, blade height and blade number for micro-hydro application continue to be inadequate, even though there is a need and potential for the application of such turbines. This inadequacy provides a good ground to make a detailed experimental study to characterize these influences.The paper presents a holistic theoretical model that attempts to bring out a functionality of the internal performance parameters of the runner and attempts to establish a physical relationship between the two design parameters (blade height and blade number) and the performance parameters.The experimental results on 3 runners showed that with an increase in the number of blades, the efficiency of the runner dropped drastically due to the change in direction of the relative flow vector at the runner exit, which decreased the net rotational momentum and increased the axial flow velocity. The decrease of blade height on the other hand decreased the overall runner loss coefficient quite drastically but this could not result in major performance gains.The study concluded that the influence of blade number is more dominating compared to that of the blade height and that choice of blade number should be carefully made. On the hydraulic level, the study found interesting effects like the slip phenomenon and loss mechanisms within the runner. The paper also looks into the possible errors within the theoretical model developed and the extent of their influence on the conclusions. The paper suggests more experimental studies to separately study the effects of blade number and blade height. It further makes a strong case to initiate a computational work to validate all the experimental findings, fill the gaps in the theoretical model and use it as an optimization and standardization tool for axial flow turbines in the specialized application of micro-hydro.     

Exergy analysis of cryogenic air separation

An exergy analysis is performed to analyse the possibilities of fuel saving in the cryogenic distillation process, which is the main method of air separation. It is shown that more than half of the exergy loss takes place in the liquefaction unit and almost one-third in the air compression unit. Minor exergy losses are taking place in the distillation unit and the main heat exchanger. The major cause of exergy loss is the use of compressors and to a lesser extent the use of turbines. Especially, the relatively low rational efficiency of the turbines operating in the cryogenic region is striking. Improvements are suggested which save one-fourth of the exergy loss. For more substantial reductions of the exergy losses in air separation alternative processes have to be used or developed.     

不同参数端壁翼刀控制二次流机理的实验研究

不同周向和轴向位置的压气机叶栅上安装1／2轴向弦长翼刀的叶栅出口流场测量结果表明,两种方案的叶栅总损失随翼刀周向位置变化的总体趋势是翼刀靠近压力面时叶栅总损失降低。翼刀安装在流道前半部的最佳周向位置是距离吸力面60％相对节距处;安装在流道后半部的翼刀最佳周向位置是距离吸力面80％相对节距处。通过对比初步探讨了翼刀减小二次流损失的机理：一方面通过降低流道内端壁附面层内横向压力梯度,减弱低能流体向吸力面／壁角区的堆积;另一方面是通过产生的反向翼刀涡限制马蹄涡的压力面分支发展,从而减小通道涡的尺寸和强度。     

Experimental Study of Endwall and Tip Clearance Flows in a Two—Dimensional Turbine Rotor Blade Cascade—Effect of Incidence Angle

IntroductionA ttirbomachinery rotor must have a slhall hilt finite clearance relative to its surrounding casing. Theflow, which leaks thlough this fililte gap, has a surprisingly large effect on the aerodynamics of the flow.The loss produced due to the tip clearance is an.unavoidable loss. The presence of tip clearance ajtersthe endwall flow siglilflcaotly. The normal secondaryflow interacts with the leakage fluid ajs it easts fromthe suction surface. The leakage fluid rolls into whatis known…