分体滑动导叶可调涡轮激波与载荷波动机制

针对某柴油机用可调涡轮在低速工况下的低效强激波特征,提出并设计了一种分体滑动导叶,并在10%、40%和100% 3个典型开度下进行了定常/非定常数值计算。结果表明：分体滑动导叶在小开度下可实现对间隙泄漏流动的有效抑制,大幅度提高涡轮效率;在10%开度下,分体滑动导叶提高了涡轮10%的峰值效率,同时涡轮效率在40%和全开工况下也有不同程度的提高。此外,通过合理设计转静间距,分体滑动导叶尾缘激波被大幅度削弱。导叶间隙泄漏流和尾缘激波的抑制可有效弱化转子定子干涉强度,降低下游转子叶片表面载荷波动幅值,提高转子叶片的可靠性。     

对转涡轮低压转子叶片的流固耦合数值分析

采用对转涡轮设计能提高航空涡轮发动机性能,其中无导叶方案是发展趋势之一。在无导叶对转涡轮中,低压转子叶片受到较大的高压转子出口气流激励。基于ANSYS/CFX软件,采用流固耦合数值分析方法对低压涡轮转子叶片进行了分析,得到了高压涡轮转子叶片尾流作用下的低压涡轮转子叶片振动的应力和变形变化规律。叶片温度对振动应力和位移的平均值、幅值和周期的影响较大,叶片材料密度对振动周期产生明显的影响,高低压转叶轴向间距的选择应兼顾涡轮效率等因素。     

Turbine operation with nonsteady flow-analysis and experiments

The paper describes a theoretical and experimental study of the internal flows in single-stage, axial-flow pulse turbine. In the theoretical analysis, based on the method of characteristics, special attention was given to the boundary condition governing the flow from the nozzles into the rotor blades under off-design conditions. The analysis showed a momentum exchange occurring across the nozzle-rotor boundary, leading to entropy generation in the rotor passages, and corresponding energy dissipation.

Experiments conducted on a test turbine, in which turbine internal work was calculated from speed change data, showed remarkably high performance figures. A comparison of predicted performance with test measurements showed good agreement in the range of turbine speeds for which the analysis was written. It was concluded that substantial improvements in pulse turbine performance through design changes involving nozzle and rotor blades are not to be expected.     

Numerical predictions of roughness effects on the performance degradation of an axial-turbine stage

This paper describes a numerical investigation on the performance deteriorations of a low speed, single-stage axial turbine due to use of rough blades. Numerical calculations have been carried out with a commercial CFD code, CFX-Tascflow, by using a modified wall function to implement rough surfaces on the stator vane and rotor blade. To assess the stage performance variations corresponding to 5 equivalent sand-grain roughness heights from a transitionally rough regime to a fully rough regime, stage work coefficient and total to static efficiency were chosen. Numerical results showed that both work coefficient and stage efficiency reduced as roughness height increased. Higher surface roughness induced higher blade loading both on the stator and rotor which in turn resulted in higher deviation angles and corresponding work coefficient reductions. Although, deviation angle changes were small, a simple sensitivity analysis suggested that their contributions on work coefficient reductions were substantial. Higher profile loss coefficients were predicted by higher roughness heights, especially on the suction surface of the stator and rotor. Furthermore sensitivity analysis similar to the above, suggested that additional profile loss generations due to roughness were accountable for efficiency reductions.     

动静干涉下低压涡轮非定常气动载荷研究

为研究动静干涉下轴向间距和尾缘锯齿结构对低压涡轮叶片非定常气动载荷的控制作用,对高效节能发动机(energy efficient engine,简称E3)低压涡轮最后一级的内部流场进行了数值仿真,研究了不同轴向间距和静叶尾缘锯齿结构两种情况下,下游动叶表面非定常气动载荷的变化规律。研究发现：增大轴向间距可以加强尾迹与主流的掺混,消除气流不均匀性,削弱下游动叶表面的非定常气动载荷;静叶采用尾缘锯齿结构不仅可以加强尾迹与主流的掺混,同时还会改变尾缘处的涡结构,对下游动叶前缘产生破坏性干涉效应,使其最大载荷波动降低约30%,减少静叶尾迹速度亏损75.7 m/s,还能适当提升涡轮的流通能力和时均效率。与采用直尾缘静叶的模型相比,采用锯齿尾缘静叶不仅能大幅度地改善涡轮的转静干涉效应和气动性能,还能在不影响涡轮效率的前提下,将涡轮轴向间距缩短10%。     

Design, fabrication, and testing of a MEMS microturbine

This paper describes the design, fabrication, and testing of a microturbine developed at Seoul National University Here, the term “microturbine” refers to a radial turbine with a diameter on the order of a centimeter Such devices can be used to transmit power for various systems The turbine is designed using a commercial CFD code, and it has a design flow coefficient of 0 238 and work coefficient of 0 542 It has 31 stator blades and 24 totor blades A hydrodynamic journal bearing and hydrostatic thrust bearings counteract radial and axial forces on the rotor The test turbine consists of a stack of five wafers and is fabricated by MEMS technology, using photolithography, DRIE, and bonding processes The first, second, fourth, and fifth layers contain plumbing, and hydrostatic axial thrust bearings for the turbine The third wafer contains the turbine’s stator, rotor, and hydrodynamic journal bearings Furthermore, a turbine test facility containing a flow control system and instrumentation has been designed and constructed In performance tests, a maximum rotation speed of 11,400 rpm and flow rate of 16,000 seem have been achieved     

用于电动汽车上双滑板压缩机的泄漏损失研究

研究了运用在电动汽车空调系统中的双滑板压缩机的泄漏损失。采用等截面摩擦喷管模型计算了双滑板压缩机中转子与转缸间隙处的径向间隙泄漏,同时计算了滑板侧的轴向泄漏。作为对比,计算了相同工况以及相同的转缸和转子尺寸下单滑板压缩机的泄漏损失。通过对比发现:在相同的尺寸和运行工况下,双滑板压缩机的泄漏损失要高于单滑板压缩机,但是双滑板压缩机的理论吸气容积要高于单滑板压缩机,二者的相对容积泄漏损失率几乎相等。因而相对于单滑板压缩机,双滑板压缩机结构上的变化是可以忽略的。考虑到双滑板压缩机具有更高的工作容积和机械效率,可以推断其更适合用于电动汽车的空调系统上。     

采用伊斯卡刀具高效率加工涡轮增压器

<正>当前,缩减发动机尺寸是汽车行业的重头戏,德国的本地汽车制造商以及来自韩国和日本的汽车制造商均跟随此趋势。虽然V6发动机与直列六缸发动机至今还在大量生产,但通过采用涡轮增压技术,大幅削减气缸容量的发动机可凭借优异的性能与自然吸气式发动机相媲美。从2014赛季开始,F1赛事中的赛车也开始采用涡轮增压发动机。工程师们开发出1.61     

高炉煤气余压发电透平机转子叶片的断裂分析

为分析研究透平机转子叶片的损坏机理,提高叶片使用可靠性,依据高炉煤气余压、余热发电透平机转子叶片的结构设计、加工工艺、叶片的测频、使用工况等条件,对该装置的转子-轴承系统的临界转速、振动特性进行了分析。通过计算分析,转子系统的振动特性符合有关旋转机械转子系统整体振动的设计规范;叶片的静态应力水平符合所用材料的许用应力;叶片的固有频率与工作时的激励频率有足够的避开量。分析结果为该设备的失效原因提供了理论根据,提高了设备日常维护工作的有效性。     

某型发动机涡轮导向叶片故障探讨

针对某型发动机涡轮导向叶片故障作进行了详细的分析，并推测了产生的原因，并据此提出了改进的设想和使用维护中应注意的问题。     

Response and flow characteristics of a dual-rotor turbine flowmeter

The technical problems of flow measurement in hypersonic flight could be mitigated through dual-rotor turbine flowmeters (DRT-FMs). In this study, a visual experiment platform was designed to reproduce the flow of a 1.3 cm diameter DRT-FM. A mathematical model considering two rotors was developed to perform a parameterised study and evaluate the rotor responses. Further, the entire flow passage was numerically simulated through an added automatic iterative rotor-dynamic calculation based on the angular momentum balance theory. According to the experimental results, the response range of the rotational speeds was divided into three stages: unresponsive, unstable, and stable. The downstream rotor responded at a lower flow rate, increasing the measurement range of the rotor turbine flowmeter. Considering the region of linear increase in the rotor speed in stable state under different flow media, tip clearances, and number of blades, the mathematical results indicated that the downstream rotor exhibited a compensation effect of the rotational speed on the calculation of rotational speed at the current flow rate conditions, which mitigates the measurement instability of the upstream rotor. Through the simulations, the rotation speed difference of the two rotors resulted in a slight periodic disturbance to the downstream rotor, which was alleviated after flowing through the spacer and could be ignored. Moreover, the high vorticity regions appeared around the rotors and areas of abrupt structural changes in the flow passage; the distribution gradually extended as the vorticity decreased. The present study provides an understanding of the DRT-FM and some recommendations to improve its characteristics.     

高压涡轮导向器前支撑质量流量测量研究

试验测量总是伴随有误差的产生,这里对音速喷管在航空发动机高压涡轮内部导向器流量测量系统进行分析,主要介绍误差来源、误差分配理论分析方法及其在实际仪器选择上的应用.以高压涡轮内部导向器前支撑流量测量为例,在给定测量系统总误差条件下,提出一种可行的误差分配方案.该方案满足精度要求,成本低.     

Investigations on the effect of guide vane thickness and solidity on shock and unsteady flow characteristic of VNT

In this work, the influence of thickness and solidity of guide vane on the unsteady flow of a radial inflow turbine with variable nozzle has been numerical     

Blade number effect for a ducted wind turbine

Ducted wind turbine with multiple blades installed was believed to have a good wind power energy conversion effect. However, little information was available on how to design a good ducted wind turbine. In this paper the effects of blade number on a ducted wind turbine performance is studied. Numerical studies using CFD method to simulate the wind turbine performance were adopted. The duct is a converging-diverging nozzle with the turbine blades located at the throat. A rated output of a 1-kW turbine is adopted as the baseline design. It was found that the blade geometry, stagger angle, and number of blades have different duct blockage effects, and do affect the turbine performance (specifically the power coefficient and torque coefficient, etc.). The fewer number of blades has higher through flow speed, while the larger number of blades provides larger torque. The best power coefficient lies in between the two extremes. The appropriate number of blades is important to match the generator performance curve for optimal overall performance and efficiency. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju Korea, October 16–19, 2007.     

Fast-response total pressure probe for turbomachinery application

To evaluate the accurate performance and characteristics of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotating blades. This paper presents the development of a fast-response total pressure probe for the measurement of the total pressure field at the exit of blades. The result of measurement in a one-stage axial turbine is also presented. The fast-response total pressure probe is fabricated by installing a fast-response pressure sensor in the cylindrical head of the probe. In terms of simplicity of the measurement system and data reduction method, this method is more competitive over established methods that use more than four sensors. The probe is applied to the one-stage axial turbine in order to measure the instantaneous total pressure downstream of rotor blades. The measured instantaneous signal is decomposed to obtain the blade-to-blade pressure distribution. The pressure distribution due to blade passing is clearly captured. Due to the loss generation in the casing region, the total pressure and its amplitude of fluctuation by the blade passing are lower in the shroud and hub region than in mid-span. The total pressure distribution at the exit of the rotor blade is found to be slightly different from blade to blade due to the geometric difference and the different relative positions of the rotor blades and stator vanes. The developed probe successfully measures the accurate total pressure distribution at the rotor exit, and allows the evaluation of the loss distribution and the accurate performance of turbomachinery.     

汽轮机再热后级内颗粒冲蚀特性

汽轮机再热后级内叶片受到固体颗粒冲蚀,严重影响着汽轮机的安全经济运行。以某超临界汽轮机再热后第1+1/2级(第一级与相邻级的喷嘴)扭叶片为研究对象,通过拉格朗日法模拟不同粒径颗粒三维运动轨迹,并采用Finnie冲蚀模型,研究不同动静轴向间隙及不同负荷下颗粒对叶片的冲蚀特性。结果表明,由于动叶高速旋转,颗粒撞击到动叶时会获得与主流方向相反的速度,进而又反弹回静叶。较大粒径颗粒在动静叶片轴向间隙内"反复反弹"是造成再热后级内冲蚀的主要原因。适当增大动静轴向间隙可以有效地减少反弹回静叶的颗粒数量。当动静轴向间隙为5 mm时,反弹回静叶的颗粒为10%,轴向间隙增大为8 mm时,没有颗粒反弹回静叶。当机组负荷降低时,固体颗粒撞击叶片后的反弹角增大、反弹回静叶的数量增多,颗粒在动叶和下级静叶轴向间隙内反弹后,只有极少颗粒能够流出下级静叶。     

1.5级涡轮动叶的非轴对称端壁造型数值研究

为探究端壁造型对涡轮动叶气动性能及流场特性的影响,分析非轴对称端壁造型对涡轮转子叶片的压差作用,开展基于非轴对称端壁造型的理论研究,提出一种涡轮动叶轮毂上凸、下凹的造型方案,研究非轴对称端壁造型对涡轮流场二次流损失的影响。数值模拟分析表明：非轴对称端壁造型对减小横向压差具有重要作用,在动叶轮毂鞍点处进行非轴对称端壁造型,比在通道内造型效果更好;涡轮动叶下端壁不同区间造型可有效降低涡轮动叶通道内的二次流流动损失,使用非轴对称端壁造型方法可有效地减小动叶出口总压损失系数0.132 2%。     

径向水平井自进式旋转射流钻头流场特性分析

为解决径向水平井钻进过程中破岩效率和自进能力的问题,设计了一种自进式旋转射流钻头。运用数值模拟方法,采用RNG k-ε湍流模型对所设计射流钻头的内外流场进行了三维流动特性分析,并分析了射流钻头结构参数对喷嘴流场特性的影响规律,进一步优化了自进式旋转射流钻头。结果表明,自进式旋转射流喷嘴外流场的轴心速度在喷嘴中心线上的速度最大,随着径向半径的增大,轴向速度迅速减小;切向速度沿喷嘴径向呈现出经典的"N"形分布,有利于增大射流破碎岩石的深度和破碎面积;径向速度呈轴对称分布,存在明显的漫流层,有助于岩屑的脱离;自进式旋转射流钻头导向叶轮的螺距和导叶数量,对射流速度有着重要的影响;喷嘴直径对射流流场特性的影响较大。经过优化,得到射流钻头的叶轮螺距16mm,导叶数为2,喷嘴直径为1mm。     

High-efficiency approach for fabricating MTE rotor by micro-EDM and micro-extrusion

Micro-gas turbine engine（MTE） rotor is an important indicator of its property, therefore, the manufacturing technology of the microminiature rotor has become a hot area of research at home and abroad. At present, the main manufacturing technologies of the MTE rotor are directed forming fabrication technologies. However, these technologies have a series of problems, such as complex processing technology high manufacturing cost, and low processing efficiency, and so on. This paper takes advantage of micro electric discharge machining（micro-EDM） in the field of microminiature molds manufacturing, organizes many processing technologies of micro-EDM reasonably to improve processing accuracy, presents an integrated micro-EDM technology and its process flow to fabricate MTE rotor die, and conducts a series of experiments to verify efficiency of this integrated micro-EDM. The experiments results show that the MTE rotor die has sharp outline and ensure the good consistency of MTE rotor blades. Meanwhile, the MTE rotor die is applied to micro extrusion equipment, and technologies of micro-EDM and micro forming machining are combined based on the idea of the molds manufacturing, so the MTE rotor with higher aspect ratio and better consistency of blades can be manufactured efficiently. This research presents an integrated micro-EDM technology and its process flow, which promotes the practical process of MTE effectively.     

Combined effects of channel curvature and rotor configuration on the performance of two-stage viscous micropumps

The combined effects of channel curvature and rotor configuration on the performance of two-stage viscous micropumps were studied numerically. The Navier-Stokes equations were simulated to investigate the performance of two-stage micropumps. The performance of two-stage micropumps was studied in terms of the dimensionless mass flow rate and dimensionless driving power. Four different rotor configurations were designed by changing placement of two rotors inside a microchannel: Two aligned and two staggered configurations. The aligned rotor configuration of type 1 is to place the two rotors along the convex wall, while type 2 is to place them along the concave wall. Numerical results show that the rotor configuration plays a significant role in the performance of two-stage micropumps. The channel curvature acts in a different way according to the rotor configuration. The mass flow rate of aligned rotor configuration of type 1 is greatly improved by the channel curvature, while it diminishes the mass flow rate of type 2. The maximum mass flow rate for the aligned rotor configuration of type 1 is obtained when the two rotors are placed at the junction of the circular and straight sections of the channel. The performance of staggered configurations is negligibly affected by the channel curvature. This characteristics is found due to rotation direction of the rotors. As the two rotors rotate in the opposite direction for the staggered configurations, the flow characteristics in the circular section is little affected by the channel curvature. The circumferential distance between the two rotors can be optimized in terms of the mass flow rate. The optimal value of the circumferential distance is about L = 1.4 for the staggered rotor configurations, and it is almost independent of the channel curvature. As the channel height increases, the circumferential distance becomes less significant for the staggered rotor configurations while it becomes significant for the aligned rotor configurations.