Effects of rising angle on upstream blades and intermediate turbine duct

With the improvement of requirement, design and manufacture technology, aero-engines for the future are characterized by further reduction in fuel consumption, cost, but increment in propulsion efficiency, which leads to ultra-high bypass ratio. The intermediate turbine duct (ITD), which connects the high pressure turbine (HPT) with the low pressure turbine (LPT), has a critical impact on the overall performances of such future engines. Therefore, it becomes more and more urgent to master the design technique of aggressive, even super-aggressive ITDs. Over the last years, a lot of research works about the flow mechanism in the diffuser ducts were carried out. Many achievements were reported, but further investigation should be performed. With the aid of numerical method, this paper focuses on the change of performance and flow field of ITD, as well as nearby turbines, brought by rising angle (RA). Eight ITDs with the same area ratio and length, but different RAs ranges from 8 degrees to 45 degrees, are compared.According to the investigation, flow field, especially outlet Ma of swirl blade is influenced by RA under potential effect, which is advisable for designers to modify HPT rotor blades after changing ITD. In addition to that, low velocity area moves towards upstream until the first bend as RA increases, while pressure loss distribution at S2 stream surface shows that hub boundary layer is more sensitive to RA, and casing layer keeps almost constant. On the other hand, the overall total pressure loss could keep nearly equivalent among different RA cases, which implies the importance of optimization.     

Numerical investigation of the effects of ITD length on low pressure nozzle

The advantage of high efficiency,low SFC (Specific Fuel Consumption),ultra-high bypass ratio turbofan engine attracts more and more attention in modem commercial engine.The intermediate turbine duct (ITD),which connects high pressure turbine (HPT) with low pressure turbine (LPT),has a critical impact on the overall performance of turbine by guiding flow coming from HPT to LPT without too much loss.Therefore,it becomes more and more urgent to master the technique of designing aggressive,even super-aggressive ITD.Much more concerns have been concentrated on the duct.However,in order to further improve turbine,LPT nozzle is arranged into ITD to shorten low pressure axle.With such design concept,it is obvious that LPT nozzle flow field is easily influenced by upstream duct structure,but receives much less interests on the contrary.In this paper,numerical method is used to investigate the effects of length of ITD with upstream swirl blades on LPT nozzle.Nine models with the same swirl and nozzle blades,while the length of ITD is the only parameter to be changed,will be discussed.Finally,several conclusions and advices for designers are summarized.After changing axial length of ducts,inlet and outlet flow field of nozzle differs,correspondingly.On the other hand,the shearing stress on nozzle blade (suction and pressure) surface presents individual feature under various inlet flow.In addition to that,"Clocking-like effect" is described in this paper,which will contribute much to the pressure loss and should be paid enough attention.     

Influence of Reynolds Number on the Unsteady Aerodynamics of Integrated Aggressive Intermediate Turbine Duct

The ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine due to advantages of high efficiency and low Specific Fuel Consumption (SFC). One of the characteristics of ultra-high bypass ratio turbofan is the intermediate turbine duct which guides the flow leaving high pressure turbine (HPT) to low pressure turbine (LPT) at a larger diameter, and this kind of design will lead to aggressive intermediate turbine duct (AITD) design concept. Thus, it is important to design the AITD without any severe loss. From the unsteady flow’s point of view, in actual operating conditions, the incoming wake generated by HPT is unsteady which will take influence on boundary layer’s transition within the ITD and LPT. In this paper, the three-dimensional unsteady aerodynamics of an AITD taken from a real engine is studied. The results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX (RANS simulation with transitional model), are critically evaluated against experimental data. After validation of the numerical model, the physical mechanisms inside the flow channel are analyzed, with an aim to quantify the sensitivities of different Reynolds number effect on both the ITD and LPT nozzle. Some general physical mechanisms can be recognized in the unsteady environment. It is recognized that wake characteristics plays a crucial role on the loss within both the ITD and LPT nozzle section, determining both time-averaged and time-resolved characteristics of the flow field. Meanwhile, particular attention needs to be paid to the unsteady effect on the boundary layer of LPT nozzle’s suction side surface.     

变几何低压涡轮级多工况气动性能研究

为明确变几何低压涡轮级在多转角工况下气动性能变化情况,通过RANS方法并结合SST湍流模型,研究了可调导叶转角分别为-6°,-3°,0°,3°和6°条件下低压涡轮级的气动性能变化。结果表明：可调导叶旋转角度的变化会明显改变导叶叶顶及动叶通道内的流动情况,角度变大会增加涡轮级流量,并使导叶叶顶处负荷后移,上端区二次流强度增加,叶顶泄漏情况减弱,还会减小动叶进口相对气流角,使动叶压力面出现明显分离;角度变小对低压涡轮级流场的影响与之相反。当导叶转角从-6°变化到+3°时,涡轮级等熵滞止效率提升了约6.7%;当导叶转角从+3°变化到+6°时,涡轮级效率却下降了约0.19%。     

Numerical study of combining steady Vortex Generator Jets and Deflected Trailing edge to reduce the blade numbers of low pressure turbine stage

A flow control system that combined steady Vortex Generator Jets and Deflected Trailing-edge (VGJs-DT) to decrease the low pressure turbine (LPT) blade numbers was presented. The effects of VGJs-DT on energy loss and flow of low solidity low pressure turbine (LSLPT) cascades were studied. VGJs-DT was found to decrease the energy loss of LSLPT cascade and increase the flow turning angle. VGJs-DT decreased the solidity by 12.5% without a significant increase in energy loss. VGJs-DT was more effective than steady VGJs. VGJs-DT decreased the energy loss and increased the flow angle of the LSLPT cascade with steady VGJs. VGJs-DT can use 50% less mass flow than steady VGJs to inhibit the flow separation in the LSLPT cascade. The deflected trailing edge enhanced the ability of steady VGJs to resist flow separation. Overall, VGJs-DT can be used to control flow separation in LPT cascade and reduce the blade numbers of low pressure turbine stage.     

Effects of nozzle-strut integrated design concepton on the subsonic turbine stage flowfield

In order to shorten aero-engine axial length,substituting the traditional long chord thick strut design accompanied with the traditional low pressure（LP） stage nozzle,LP turbine is integrated with intermediate turbine duct（ITD）.In the current paper,five vanes of the first stage LP turbine nozzle is replaced with loaded struts for supporting the engine shaft,and providing oil pipes circumferentially which fulfilled the areo-engine structure requirement.However,their bulky geometric size represents a more effective obstacle to flow from high pressure（HP） turbine rotor.These five struts give obvious influence for not only the LP turbine nozzle but also the flowfield within the ITD,and hence cause higher loss.Numerical investigation has been undertaken to observe the influence of the Nozzle-Strut integrated design concept on the flowfield within the ITD and the nearby nozzle blades.According to the computational results,three main conclusions are finally obtained.Firstly,a noticeable low speed area is formed near the strut＇s leading edge,which is no doubt caused by the potential flow effects.Secondly,more severe radial migration of boundary layer flow adjacent to the strut＇s pressure side have been found near the nozzle＇s trailing edge.Such boundary layer migration is obvious,especially close to the shroud domain.Meanwhile,radial pressure gradient aggravates this phenomenon.Thirdly,velocity distribution along the strut＇s pressure side on nozzle＇s suction surface differs,which means loading variation of the nozzle.And it will no doubt cause nonuniform flowfield faced by the downstream rotor blade.     

非定常脉冲爆震来流下涡轮气动特征仿真研究

脉冲爆震涡轮发动机是未来涡轮发动机的一种有潜力的发展方向。为了厘清具有强非定常性的脉冲爆震来流下涡轮的气动性能及流动特征,为脉冲爆震涡轮发动机涡轮的设计提供技术支撑,采用非定常进口总压与总温边界条件对某单级燃气涡轮开展了瞬态数值仿真计算分析。研究结果表明：由于进口来流的强非定常性,涡轮内部流动在爆震周期的前段时间并未完全建立起流动平衡,故进出口的流量不守恒;焓降功率与扭矩功率、焓降效率与扭矩效率不相等;在一个爆震周期内,动叶进口气流攻角的变化幅度达到40°,出口绝对气流角的变化幅度达到50°。在一个爆震周期中,只有约1/4的时间段涡轮的气动状态接近设计点,故一个爆震周期中涡轮的综合功率较低。     

基于CFD仿真的柴油机中冷器流动均匀性优化

基于某船用柴油机1D热力学模型提供的计算边界条件,采用3D CFD对该柴油机匹配的中冷器的瞬态流动及换热过程进行仿真模拟,计算分析中冷器入口截面的速度均匀性以及前进气箱压力损失。结果表明:中冷器入口截面的速度均匀性系数未完全达到设计目标。对中冷器前进气箱的结构进行优化设计,优化后的中冷器入口截面的速度均匀性系数有所提高,满足设计要求,同时中冷器前进气箱的压力损失处于较低水平。     

涡轮叶片蜂巢式冷却结构减阻能力数值研究

先进航空发动机中高耐温能力涡轮叶片通常要以增加冷却系统的流动阻力来提高冷却效果,但由此导致的二次流系统损失增大可能会引起整机性能的下降。为解决该问题,研究了先进涡轮叶片中典型层板冷却结构的内部流动损失产生机理,并针对性地提出两种(进/出气孔平行式和交叉式)低流动阻力的类蜂巢式冷却结构。基于三维数值仿真方法研究了其流动特点和损失特性,并揭示了该结构可以显著减小通道内气流转折角度、抑制旋涡产生和避免多股气流对撞的减阻强化机理。通过与典型层板结构的对比分析,初步验证了在相同的结构无量纲参数和流量下,两类蜂巢式冷却结构的总压损失分别可降低65~66%和67~69%,在高推重比航空发动机涡轮叶片冷却设计上具有较好的应用前景。     

Evaluation and analysis of evaporation cooling on thermodynamic and pressure characteristics of intake air in a precooled turbine engine

The precooled turbine engine is applied to overcome the limitation of Mach number due to high temperature inlet air. This paper aims to investigate the effect of water injection cooling on the high-temperature intake air. Then, the theory evaluation and Eulerian-Lagrangian multiphase flow method are conducted to explore the thermodynamic process and resistance characteristics of the pre-cooling section built-in even spray apparatus with a drag reduction. Results show that larger amount of the injection flow rate at higher Mach number will deteriorate total pressure loss and flow field uniformity. Evaporation cooling can decrease flow loss by 9.4%–60.7%. Within 27 ms, total-temperature drop is in 14–144 K range with a low total-pressure drop coefficient of 0.56%–1.29%. Especially, mass flow will increase by 1.15%–18.50%. Thus, water injection cooling is conducive to a higher acceleration, as well as for improving the thermodynamics characteristics of inlet air for a turbine engine at a high Mach number.     

基于正交试验的低速机增压器涡轮排气壳性能优化研究

为提升船用低速机涡轮增压器性能,对增压器涡轮排气壳底部流道结构进行参数化,设计并开展了以效率为优化目标的四因素三水平正交试验优化设计和增压器整机性能试验。首先,采用CFD数值模拟方法对不同参数组合的涡轮气动性能进行了计算,然后对涡轮排气壳底部流道结构参数开展了灵敏度分析,同时针对不同参数组结构开展了内部流场对比分析,明确结构因素对流动的影响机理;在此基础上对优化后方案开展了涡轮特性分析,最后在低速双燃料机平台上开展增压器整机试验验证。分析研究表明：在涡轮进气壳、喷嘴环和涡轮叶片等通流部件结构不变的前提下,涡轮排气壳排气方向轴向长度对涡轮整级效率的影响最大,优化后效率明显提升,设计点总压损失系数降低0.3874,静压恢复系数提升0.537,总静效率提升1.85%,其余工况总静效率最大提升2.4%。试验结果表明：优化后涡轮增压器整机效率在主机燃油模式和燃气模式下的全工况范围内效率均有提升,最大提升幅度分别达到1.4%和2.1%,涡轮性能和增压器整机性能改善明显。     

9E燃气轮机进气滤网更换周期经济测算实例分析

以广东某调峰9E燃气轮机发电机组为例,通过进气滤网实际运行压损大数据分析,得出进气滤网在运行过程中压损上升趋势,并通过对大数据的数据筛选、相关边界条件的规定建立简单进气滤网更换周期经济测算模型,得出进气滤网最经济更换周期,为更换进气滤网周期提供理论依据,实现燃气轮机进气滤网更换精细化管理。     

可调二级增压柴油机旁通阀特性和调节规律的试验

对柴油机应用可调二级增压系统进行了全工况的试验研究.结果表明,涡轮旁通阀可以对增压压力进行调节进而影响柴油机的性能.可调二级增压系统可以增大柴油机中低转速的增压压力,改善碳烟排放;当循环供油量增加后还可以提高中低速时的外特性转矩.中低转速中高负荷时,两级增压会提高进气量改善燃烧,明显地提高了燃油经济性.中高速时,进气量的提高没有明显地改善燃烧的效果,反而造成泵气损失增大,基于经济性考虑应开启涡轮旁通阀,与此同时为避免节流效应压气机旁通阀也应开启将高压级增压器完全旁通,旁通后由于复杂的进排气管增加了流动损失使得油耗略有升高.     

Numerical study of improving aerodynamic performance of low solidity LPT cascade through increasing trailing edge thickness

This paper presents a new idea to reduce the solidity of low-pressure turbine (LPT) blade cascades, while remain the structural integrity of LPT blade. Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness (TET). The solidity of the LPT cascade blade can be reduced by about 12.5% through increasing the TET of the blade without a significant drop in energy efficiency. For the low solidity LPT cascade, increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by 1.86% for Reynolds number (Re) of 25,000 and freestream turbulence intensities (FSTI) of 2.35%. The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented. The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.     

发动机氧涡轮喷嘴叶栅气动特性的试验研究

对一个用于大推力液体火箭发动机氧涡轮泵的复速级涡轮的喷嘴叶栅进行了试验研究，以考察喷嘴叶栅的气动特性，验证喷嘴叶栅的气体设计。该复速级喷嘴叶栅采用先进的后加载流动控制技术，以减弱叶机的二次流损失，对喷嘴叶栅进行了四个进气口流角，三个出口等熵马赫数条件下的平面叶栅吹风试验，测取了型面压力分布，出口气流角以及叶栅损失等重要气动特性参数，试验研究表明氧涡轮的喷嘴叶栅的设计是成功的，具有良好的气动特性，可以有效地应用于液体火箭发动机的涡轮中，本研究也为该类喷雾叶栅的设计提供了有用的实验数据和指导意义的结论。     

F级改进型联合循环主蒸汽系统压损研究及优化

为了给燃气轮机联合循环工程提高蒸汽循环效率提供借鉴经验和优化方法,依托已投产F级改进型燃气轮机联合循环工程,采用GTpro软件平台,分析了该机组高压主蒸汽进汽压力对联合循环热力性能的影响,并计算得到此系统压损使机组出力的降幅随着高压主蒸汽进汽压力的提高而减小。通过深入研究高压主蒸汽流量测量作用和方法,借鉴常规燃煤火电超超临界汽轮机主蒸汽流量的间接测量技术,优化主蒸汽系统并取消流量计,从而提高机组效率,增加收益。     

A method for the determination of turbulence intensity by means of a fast response pressure probe and its application in a LP turbine

This paper describes the measurements and the post-processing procedure adopted for the determination of the turbulence intensity in a low pressure turbine (LPT) by means of a single sensor fast response aerodynamic pressure probe. The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put into the adjustment of all relevant model parameters. Blade count ratio, airfoil aspect ratio, reduced massflow, reduced speed, inlet turbulence intensity and Reynolds numbers were chosen to reproduce the full scale LP turbine. Measurements were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The total pressure random fluctuations are obtained by selectively filtering, in the frequency domain, the deterministic unsteadiness due to the rotor blades and coherent structures. The turbulence intensity is derived from the inverse Fourier transform and the correlations between total pressure and velocity fluctuations. The determination of the turbulence intensity allows the discussion of the interaction processes between the stator and rotor for engine-representative operating conditions of the turbine.     

Performance of vertical axis water turbine with eye-shaped baffle for pico hydropower

A series of inline pico hydropower systems, which could be used in confined space, especially for water distribution networks (WDNs), was designed and investigated. The turbine with an eye-shaped vertical water baffle was developed to evaluate the hydraulic performance. A three-dimensional dynamic mesh was employed and the inlet velocity was considered as the inlet boundary condition, whereas the outlet boundary was set as the outflow. Then, numerical simulations were conducted and the standard k-ε turbulence model was found to be the best capable of predicting flow features through the comparison with the experimental results. The effects of the opening diameter of the water baffle and installation angle of the rotor on the flow field in the turbine were investigated. The results suggested that the water baffle opening at d = 30 mm and the rotor at a 52° angle could achieve the highest efficiency of 5.93%. The proper eye-shaped baffle not only accelerates the fluid flow and generates positive hydrodynamic torque, but also eliminates the flow separation. The scheme proposed in this paper can be exploited for practical applications in the water pipelines at various conditions and power requirements.     

湿蒸汽非均质高速凝结流动的数值研究

基于冠状成核机理,建立了湿蒸汽两相非均质凝结流动数值模型,对缩放喷管、汽轮机叶栅和汽轮机级内湿蒸汽两相非均质凝结流动进行了数值模拟．结果表明：与自发凝结相比,非均质凝结流动中杂质颗粒改变了凝结过程;杂质颗粒减小了喷管中凝结激波强度,改变了汽轮机叶栅中的压力分布,降低了蒸汽过冷度,减少了不平衡热力学损失;在汽轮机级内,非均质凝结流动的动、静叶进、出口汽流角接近过热蒸汽流动的动、静叶进、出口汽流角,其动叶前压力高于过热蒸汽的动叶前压力,但级反动度偏离过热蒸汽流动数值．     

带有冷气掺混的三级透平气动性能数值研究

借助NUMECA数值仿真软件,以某型燃气轮机的三级透平作为计算模型,对其在冷却气体掺混前后的流场进行了数值模拟。考虑到工质物性的影响,采用了变比热高温燃气作为计算工质。同时,针对燃气轮机透平进口的变工况问题,选取不同的透平进口总压值进行数值计算。结果表明,冷却气体的加入使得级损失增大,每列叶片流道出口速度或相对速度减小,下游叶片进口气流角减小;在三级透平冷气掺混时改变进口总压值,每列叶片流道的进口气流角几乎不变,除第三级动叶的激波损失与尾迹损失增大外,其余叶片流道的能量损失变化不明显。