考虑轮缘密封射流与主流相互作用的透平级气热性能研究进展

燃气轮机二次空气系统的冷却气体通过轮缘密封阻止主流燃气入侵,同时冷却气体通过轮缘密封射流进入主流流道并与主流掺混。轮缘密封射流与主流相互作用对透平级的气动性能和传热冷却特性具有重要影响。本文综述了考虑轮缘密封射流作用下透平级气动性能的实验和数值研究进展,阐明了轮缘密封射流改变端区二次流涡系结构的作用机制;介绍了轮缘密封射流对叶栅端区传热冷却性能影响的研究现状;给出了轮缘密封结构设计对提高透平级气热性能的研究成果;简要回顾了高负荷透平叶栅非轴对称端壁设计理论和进展,重点讨论了轮缘密封射流对非轴对称端壁透平级气热性能的影响特性。论文总结了考虑轮缘密封射流与主流相互作用的透平级气热性能研究结论,展望了轮缘密封射流作用下透平级气热性能需要深化的重点研究方向。     

多级轴流透平通流三维气动优化研究

燃气轮机单机功率的增大使得透平级负荷不断增加,从而对通流部分的气动造型提出了更高的要求.采用包括弯叶片和非轴对称端壁的三维通流造型系统对某两级高压透平进行了优化设计研究.优化结果表明,使用弯叶片或非轴对称端壁造型,能够改善流道内部压力分布,抑制二次流的发展,提高透平效率,分别使透平整机绝热效率提高0.37％和0.17％;而同时采用二者进行联合优化时,整机绝热效率提高了0.48％.     

轴流透平机械通流部分泄漏流动及控制技术研究进展

综述了轴流透平机械通流部分泄漏流动及控制技术的研究进展,首先详细介绍了轴流透平机械特别是汽轮机通流部分的泄漏流动特性及其对通流效率的影响,接着介绍了透平机械动叶顶部间隙泄漏流动特性及其对透平级气动性能的影响的研究,讨论了考虑间隙泄漏流动对某四级工业汽轮机气动性能的影响,研究了某汽轮机高压缸平衡孔对透平级气动性能的影响及其作用机制。论文简介了透平机械流动控制技术及其研究进展,最后给出了对透平机械泄漏流动及控制技术的研究展望。     

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。     

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...     

透平机械高负荷叶片和大焓降级的研究进展

高负荷叶片和大焓降级的设计和应用可以有效地减少透平机械通流部分的级数和叶片只数,从而在保证气动效率和安全可靠条件下,有效地降低产品的开发设计制造成本,提高透平机械产品的竞争力.对透平机械高负荷叶片的研发和应用现状进行了综述,详细介绍了高负荷叶片的气动设计和气动性能的影响因素.结合燃气轮机大焓降级的特点,综述了高负荷叶片和大焓降级的型线设计和性能研究以及在汽轮机通流设计中的应用.论文最后对高负荷叶片和大焓降级在汽轮机通流设计中的应用前景和工作重点进行了展望.     

基于NURBS曲线的离心透平叶型设计

针对离心透平的环列叶栅叶型,采用四段三次NURBS曲线(非均匀有理B样条曲线),分别对前缘圆弧、尾缘圆弧、叶背、叶盆进行参数化表达,环列叶栅叶型的设计自由度为14个,可灵活进行局部调整。采用高精度流场模拟方法,基于优选法,获得气动性能较高的设计参数。结果表明上述方法简单易行,优选出的离心透平级设计工况及变工况气动性能都得到了显著提升,与已有文献相比,单排静叶总压损失系数降低18.85%,整级轮周效率提高4.08%,动叶叶片数也减少17个。     

表面粗糙度对透平叶片气动特性的影响研究

叶片为透平的核心部件,其气动性能直接影响透平的整体效率,叶片表面粗糙度的水平会影响透平级压力,导致叶型损失发生变化。应用数值模拟技术对某冲动式和反动式机组各4级透平级进行分析,考虑反动度、载荷分布以及旋转等多种因素,研究表面粗糙度变化对透平叶片气动性能的影响。CFD数值研究表明:叶型损失变化曲线的斜率随透平叶片表面粗糙度的增大逐渐变小;不同反动度的透平叶片受叶片表面粗糙度的影响存在差异,冲动式叶片相对反动式叶片受到的影响更为明显;吸力面上的粗糙度对气动性能的影响明显大于压力面粗糙度的影响,这种影响作用在反动度提高后相应变弱。研究成果可为透平叶片设计和加工提供参考。     

轴向掠对涡轮静叶栅气动性能的影响

选用涡轮静叶栅作为原型叶片,通过对原型叶栅改变轴向掠角和掠高,构造不同掠型的叶片,研究轴向掠对涡轮静叶栅气动性能的影响.改型计算的掠角包括前后掠10°和30°,掠高包括10%和30%叶片高度,用CFD数值仿真软件对轴向掠叶栅的气动性能进行模拟.结果表明;与原型叶片比较,静叶栅轴向前掠增大了低能流体在端壁角区的集聚,增加了端壁横向二次流,引起损失增大,而叶展中部的损失减小;静叶栅轴向后掠减小了低能流体在端壁的堆积,减小了端壁二次流,低能流体被卷入到主流区内,减小了端壁损失,而增大了主流区的损失.     

具有静止顶部间隙透平叶栅气动特性的实验研究

对具有静止顶部间隙的常规透平直叶栅和透平正弯叶栅的流道和间隙进行了测量，得到流道及间隙内的详细参数。结果表明：顶部间隙的存在对叶栅的气动性能有较大影响，使叶栅上半翼损失明显增高，叶片正弯曲减小了叶顶后的横向压力梯度，削弱了泄漏流与端壁横流及二者的相互作用，降低了叶栅的流动损失，明显改善了叶栅的出口流场。     

端壁收缩对环形叶栅气动性能影响的数值研究

采用数值计算软件Numeca模拟了汽轮机低展弦比端壁收缩喷嘴中气动性能和二次流涡系的发展,并与相同边界条件下的平直端壁喷嘴比较,得到了端壁收缩对流场性能的影响.结果表明:在端壁收缩喷嘴中,较大的进口面积使得马蹄涡发展较弱,顶部区域显著的后加载特性更进一步抑制了顶部通道涡的发展,因此通道涡尤其是上通道涡的尺度和损失均较小.同时,顶部收缩导致了顶部气流出气角增大和根部出气角减小,虽然变化幅度不大,但是气流角沿叶高的分布更加均匀,对下排叶栅内的流动更加有利.另外还计算了不同高度收缩比喷嘴流动,给出了高度收缩比对叶栅流动的影响.     

Measurements of net change in heat flux as a result of leakage and steps on the contoured endwall of a gas turbine first stage nozzle

The first stage vane section of a modern gas turbine engine is assembled with a gap between the combustor and the vane platform and gaps on the platform. To prevent ingression, leakage flow is provided through each gap. In this paper, the measured net effects on endwall heat flux rates due to certain changes in the gap regions are presented. The geometry has axial contouring of the cooled endwall and several step configurations for each gap. The steps reflect assembly or differential thermal growth misalignment. Various leakage rates are applied through each gap to allow assessment of the change in heat flux rates with changes in leakage rate. Thus, the results presented herein show how the gaps, steps, and leakage rates alter the endwall cooling that can be achieved with leakage flow. The results are given as the net surface heat flux change. They are computed from heat transfer coefficient and adiabatic wall temperature distributions of comparison cases and those of a nominal case. Generally, changes in heat transfer coefficients due to gaps, steps, or increased leakage are observed to be partially offset with changes in film cooling effectiveness values such that the heat flux changes are mild. Nevertheless, elevated leakage at the transition section gap reduces heat flux at the leading edge of the platform and a fore step at the transition section gap increases heat transfer rates at the leading edge of the platform. Also, steps at the slashface gap change endwall heat flux immediately downstream of the slashface gap.     

冲角和孔排间距对端壁气膜冷却效率的影响

燃气轮机在变工况运转时透平叶栅和级的特性对燃机总体性能影响极大,而叶栅端壁气膜冷却效率是关键因素。为了提高端壁气膜冷却效率,通过优化气膜孔间距排列的方法,在叶栅端壁20%、50%、90%轴向弦长处和距前缘-10%轴向弦长端壁处布置单排带复合角度的圆柱形气膜冷却孔,运用CFD(计算流体动力学)方法对冲角(10°、0°、-10°)在不同吹风比(1、1.5、2)条件下端壁气膜冷却效率进行对比分析。结果表明:采用气膜孔非等距排列方式能有效缓解因横向压力梯度变化引起的马蹄涡在压力侧的阻隔作用,压力侧冷却效率较高;高吹风比的冷却射流会出现抛射冷却,能有效抑制冷却射流脱离壁面,壁面平均冷却效率提高;主流正冲角有利于提高端壁吸力侧气膜冷却效率,压力侧变化不大。     

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。     

Numerical investigation of a high-subsonic axial-flow compressor rotor with non-axisymmetric hub endwall

The major source of loss in modem compressors is the secondary loss. Non-axisymmetric endwall profile contouring is now a well established design methodology in axial flow turbines. However, flow development in axial compressors is differ from turbines, the effects of non-axisymmetric endwall to axial compressors requires flow analysis in detail. This paper presents both experimental and numerical data to deal with the application of a non-axisymmetric hub endwall in a high-subsonic axial-flow compressor. The aims of the experiment here were to make sure the numerically obtained flow fields is the physical mechanism responsible for the improvement in efficiency, due to the non-axisymmetric hub endwall. The computational results were first compared with avail- able measured data of axisymmetric hub endwall. The results agreed well with the experimental data for estima- tion of the global performance. The coupled flow of the compressor rotor with non-axisymmetric hub endwall was simulated by a state-of-the-art multi-block flow solver. The non-axisymmetric hub endwall was designed for a subsonic compressor rotor with the help of sine and cosine functions. This type of non-axisymmetric hub end- wall was found to have a significant improvement in efficiency of 0.45% approximately and a slightly increase for the total pressure ratio. The fundamental mechanisms of non-axisymmetric hub endwall and their effects on the subsonic axial-flow compressor endwall flow field were analyzed in detail. It is concluded that the non-axisymmetric endwall profiling, though not optimum, can mitigate the secondary flow in the vicinity of the hub endwall, resulting in the improvement of aerodynamic performance of the compressor rotor.     

Measurements and modeling of the flow and heat transfer in a contoured vane-endwall passage

Numerical simulations and laboratory measurements are obtained of the flow field and heat transfer in a linear cascade of turbine vanes, with and without secondary air injection through three discrete angled slots upstream of each vane. The hub endwall is axially profiled while the tip endwall is flat, with the hub endwall the focus of heat transfer investigation. Experimental measurements are compared to predictions of the steady-state flow obtained from solution of the Reynolds-averaged Navier–Stokes equations. Surface heat transfer characteristics predicted in the simulations are similar to measured values, with the most significant differences occurring in the cooling effectiveness.     

汽轮机调节级动叶栅大负冲角工况下的三维分离流动研究

对大功率汽轮机组提出的承担调峰任务的要求使得调节级小展弦比动叶栅非设计工况下的二次流与分离流特性受到关注。采用经试验考核的计算方法对一展弦比为0．344的动叶栅在冲角条件下的三维分离流场进行数值模拟，得到了详细的叶栅二次流与分离流的流动图谱，并给出了气流的三维分离模式。计算结果表明：在大负冲角条件下，三维分离流动显著改变了叶栅二次流结构及出口气流参数沿叶高的分布规律。叶栅出口气流在下端壁附近发生明显的欠偏转现象，同时叶栅下部的损失急剧增加，流动的总损失比设计工况增大2倍，二次流损失增大4倍。图10参5     

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).     

端壁不同角度喷射冷气对前缘喷射冷气重型燃气轮机涡轮流场的影响

本文采用中心差分格式和多区网格技术,对地面发电用燃气轮机第一级涡轮前缘喷射冷气的静叶栅的端壁喷射冷气流场进行了全三维N-S方程数值求解.分析了在端壁不同角度冷气喷射条件下,端壁冷却效率、温度场的分布规律,以及不同角度冷气喷射对叶片端壁区域流场的影响.结果表明,端壁冷气喷射角度的变化对端壁冷却效果影响较大,在小角度冷气喷...