高转速径向进气离心压气机流场特性分析

以数值模拟的方式对某小型离心压气机内部三维流场进行了详细的研究,得到相应的特性曲线与主要的参数分布。计算结果的分析表明,在设计点其结果与设计值基本吻合;在堵塞状态时径向扩压器和轴向扩压器中都存在不同程度的分离,尤其是轴向扩压器中分离现象更为严重,这些都造成了不同程度的气流损失,导致了效率的降低;数值计算结果对进一步改进此类压气机设计有一定参考价值。     

压气机进气弯管流场的计算与分析

运用先进的CAD建模技术和计算流体力学分析手段对两种压气机进气弯管进行了三维气动计算分析 ,得到了弯管内的速度、压力等分布 ,计算得出了两种进气弯管的压力损失和进气效率。从气动力学角度分析了影响弯管效率的因素 ,并通过对计算结果的分析比较指出了设计优化的方向.     

进气回流机匣处理离心压气机的扩稳机理

车用增压器的离心压气机在高转速下,往往暴露出流量过窄的问题.通过数值分析,对实壁机匣离心压气机模型高转速下的失速机理进行了研究,结果发现,转速下叶顶区域的流动变为跨音速流动,小流量下槽道激波前移至分流叶片之前,由于采用了长短叶片导致该处叶片稠度较小,间隙泄漏气流跨过激波后扰动迅速扩大,并诱发大量低能流体的堆积,促使压气机过早失稳.同时,对具有扩稳能力的进气回流机匣处理模型也进行了数值模拟,并与试验数据进行了对比验证,结果表明,布置在激波过后的回流槽能有效带走堆积在导风轮尾部附近的低能流体,减少了泄漏二次流对主流的扰动程度,使得气流以较小的攻角流过短叶片前缘,大大改善了叶轮内部流场.     

离心压气机弯管进口畸变非定常特性

采用数值模拟计算的方法研究了90°弯管对涡轮增压器装配的离心压气机进口流场产生的畸变,比较了两种不同轴向位置弯管所致的进口畸变对压气机性能的影响,并对压气机内部的三维非定常流动进行了频域分析.结果表明,弯管畸变对离心压气机性能的恶化程度与弯管所在位置有关,距离叶轮进口较远的弯管影响较大.畸变引起压气机性能在大流量时有明显降低,在小流量时性能恶化程度较小.弯管畸变导致叶轮进口前的压力脉动增强,大流量时改变了叶轮流道上游和叶顶间隙内的压力频谱结构,显著提高了转子基频的扰动强度.同时畸变也造成了叶片振动和蜗壳舌部噪声的恶化,在小流量工况下的作用更加明显.     

双离心压气机共用单一进气歧管致进口流场畸变的仿真分析

针对V型发动机的共用单一管路对置离心压气机进口流场畸变特性进行了研究,通过台架试验测试了初始压气机性能,完成了仿真模型的标定。在此基础上分析了压气机进口流场的变化特征,分析结果表明:共用单一管路对压气机特性影响明显,造成了两侧压气机堵塞流量的降低,在大流量工况区域效率明显下降,右侧压气机恶化程度要明显高于左侧。原因在于受安装位置空间限制,喉口处畸变扩展与进口周向畸变叠加效应使得右侧压气机在周向和叶高方向的畸变程度均高于左侧压气机。进口的畸变效应会一直持续至压气机叶轮内部,使压气机性能变差。     

叶片后弯角对车用离心压气机性能的影响

对比分析了6种不同转速下压气机性能的试验与仿真结果.在验证了ANSYS CFX软件用于压气机性能模拟分析中的可靠性后,采用数值模拟方法对3种不同叶片后弯角的叶轮进行了性能计算,得到了相关转速下的压气机特性曲线.仿真结果表明:在不改变压气机出口静压时,在一定的叶片出口角范围内,叶片后弯角的增加使两条特性曲线均向小流量方向偏移,但近喘振点边界得到了拓展,使得压气机的流量范围变得更宽;在小流量区域内,叶片后弯角的增大能够改善压气机内部流动状况,提高叶轮工作效率;而在大流量区域内,较大的叶片后弯角会使叶轮的流通特性降低,叶轮的工作效率反而会降低;适当增加叶片后弯角可以增大压气机工作范围,使压气机效率和流道内的流动均得到提高和改善.     

离心压气机级效率优化

提出了一个考虑多种几何和流体动力学约束条件的离心压气机级效率优化方法,叙述了优化问题的模型。计算结果表明本方法是有效且实用的。     

超临界氦气离心压气机流场分析

设计了一个包含离心叶轮、扩压器和回流器的单级超临界氦气离心压气机,并采用数值模拟方法对设计结果进行了三维数值模拟分析。通过对总特性、叶表压力分布、展向参数分布以及三维流场的分析,得到了高负荷超临界氦气离心压气机各部件内部的典型复杂流动特点。研究结果表明：相比常规工质,超临界氦气离心压气机单级压比较低,但叶轮与扩压器的负荷和级效率较高,且超临界氦气整体流动为亚音流,只在叶片前缘局部出现超音区。     

离心压气机特性曲线形成机理分析

性能曲线是评价压气机性能的重要指标,对其变化趋势及形成机理的研究具有重要意义。本文对一广泛使用的离心压气机进行全三维CFD模拟,对压气机特性曲线,特别是最高效率点之后的压比特性曲线的若干特点进行分析研究,并总结出形成这些现象的流动机理,为研究者进一步理解压气机的流动特点,从而为指导设计出更高性能的压气机奠定了基础。     

离心压气机特性曲线形成机理分析

性能曲线是评价压气机性能的重要指标,对其变化趋势及形成机理的研究具有重要意义.本文对一广泛使用的离心压气机进行全三维CFD模拟,对压气机特性曲线,特别是最高效率点之后的压比特性曲线的若干特点进行分析研究,并总结出形成这些现象的流动机理,为研究者进一步理解压气机的流动特点,从而为指导设计出更高性能的压气机莫定了基础.     

Hyperbolically Shaped Centrifugal Compressor

Starting from the classical centrifugal compressor, cone shaped in meridional cross section, two modifications are considered on the basis of results from 2D and 3D flow models. The first modification is the change of the meridional cross section to hyperbolically shaped channel. The second modification, proposed on the basis of 2D axisymmetric solution, concerns the shape of blading. On the strength of this solution the blades are formed as 3D shaped blades, coinciding with the recent tendency in 3D designs. Two aims were considered for the change of meridional compressor shape. The first was to remove the separation zone which appears as the flow turns from axial to radial direction. The second aim is to uniformize the flow at exit of impeller. These two goals were considered within the frame of 2D axisymmetric model. Replacing the cone shaped compressor by a hyperbolically shaped one, the separation at the corner was removed. The disc and shroud shape of the compressor was chosen in the way which sat     

Effects of measuring positions on the measured aerodynamic performance of a centrifugal compressor

This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software. By arranging virtual probes at different positions in both inlet and outlet planes, the aerodynamic performance of the centrifugal compressor is measured and compared with each other. Then effects of measuring positions on measurement results are discussed. The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe. The inlet total pressure data can be accurate when they are measured using a 3-point rake. The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake. Increasing tangential measuring positions at the outlet is effective to improve the test accuracy. When the outlet total pressure and total temperature are respectively measured at 3 tangential positions, the data can be almost accurate.     

Effects of bending-torsional duct-induced swirl distortion on aerodynamic performance of a centrifugal compressor

A turbocharger compressor working in commercial vehicles,especially in some passenger cars,often works together with some pipes with complicated geometry as an air intake system,due to limit of available space in internal combustion engine compartments.These pipes may generate various distortions of physical parameters of the air at the inlet of the compressor and therefore the compressor aerodynamic performance deteriorates.Sometimes,the turbocharging engine fails to work at some operation points.This paper investigates the effects of various swirl distortions induced by different bending-torsional intake ducts on the aerodynamic performance of a turbocharger compressor by both 3D numerical simulations and experimental measurements.It was found that at the outlet of the pipes the different inlet ducts can generate different swirl distortions,twin vortices and bulk-like vortices with different rotating directions.Among them,the bulk-like vortices not only affect seriously the pressure distribution in the impeller domain,but also significantly deteriorate the compressor performance,especially at high flow rate region.And the rotating direction of the bulk-like vortices is also closely associated with the efficiency penalty.Besides the efficiency,the transient flow rate through a single impeller channel,or the asymmetric mass flow crossing the whole impeller,can be influenced by two disturbances.One is from the upstream bending-torsional ducts;other one is from the downstream volute.     

Effects of Diffuser Vane Geometry on Interaction Noise Generated from a Centrifugal Compressor

The characteristics of interaction tone noise radiated from a centrifugal compressor with a vaned diffuser are discussed by experiments, including visualization techniques using the oil-film method. Research attention is paid to the leading edge geometries of the diffuser vanes that are deeply related to the generation mechanism of the interaction tone noise. The compressor-radiated noise can be reduced by several decibels by setting some clearances in both the hub and shroud surfaces of the diffuser wall along with some decline in the pressure-rise coefficient. Since the decline turned out to be caused by the flow impingement and also by the secondary flow within the diffuser passages, several new types of diffuser vane geometries which do not detract from both the performance and noise level are developed and utilized for the experiments. The presented diffuser vane geometries will offer a few basic guidelines for the diffuser vane design.     

Effects of tapered diffuser vane on the flow field and noise of a centrifugal compressor

The effects of a three-dimensional tapered diffuser vane on the flow field and noise radiated from a centrifugalcompressor are investigated by both CFD analyses and experiments.Tapered diffuser vanes are very useful notonly for the reduction of the interaction tone noise but also for the improvement of the pressure recovery charac-teristics within the diffuser passage.By using tapered diffuser vanes,the interaction area between the impel-ler-discharge flow and diffuser vanes becomes small,and then the noise level of the discrete tone can be reducedremarkably as a result.Furthermore,by utilizing the visualization technique of vortical structures based on theCFD results,the scale of vortex shedding leaving from the leading edge of the diffuser vanes is found to be con-tracted and a tendency for the turbulence level to decrease is observed.This may be the cause of the attenuation ofbroadband noise components.The secondary flow,which is considered to be an obstruction of diffuser pressurerecovery,can also be suppressed by the tapered diffuser vanes,and the pressure decrease observed in the throatpart of the diffuser passage is further reducible.     

Design and Prototyping of Micro Centrifugal Compressor

In order to establish the design methodology of ultra micro centrifugal compressor, which is the most important component of ultra micro gas turbine unit, a 10 times of the final target size model was designed, prototyped and tested. The problems to be solved for downsizing were examined and 2-dimensional impeller was chosen as the first model due to its productivity. The conventional ID prediction method, CFD and the inverse design were attempted. The prototyped compressor was driven by using a turbocharger and the performance characteristics were measured.     

小型离心式压气机的湿压缩特性研究

从工程热力学和传热传质学基本原理出发,给出了理想湿压缩的定义,研究了湿压缩对压气机性能的影响,并把计算结果与实验进行对比,得出可以通过湿压缩来减少压缩功以改善燃气轮机的性能,为湿压缩技术的可实现性提供了依据。     

Dynamic centrifugal compressor model for system simulation

A dynamic model of a centrifugal compressor capable of system simulation in the virtual test bed (VTB) computational environment is presented. The model is based on first principles, i.e. the dynamic performance including the losses is determined from the compressor geometry and not from the experimentally determined characteristic performance curves. In this study, the compressor losses, such as incidence and friction losses, etc., are mathematically modeled for developing compressor characteristics. For easy implementation in the VTB platform, the non-linear governing equations are discretized in resistive companion (RC) form. The developed simulation model can be applied to virtually any centrifugal compressor. By interfacing with a composite system, such as a Brayton cycle gas turbine, or a fuel cell, the compressor dynamic performance can be evaluated. The surge line for the compressor can also be determined from the simulation results. Furthermore, the model presented here provides a valuable tool for evaluating the system performance as a function of various operating parameters.     

Optimized efficiency axial-flow compressor

A preliminary design efficiency-optimization of an axial-flow compressor, using one-dimensional flow theory, is studied in this paper. A model for the optimum design of a compressor stage, assuming a fixed distribution of axial velocities, is presented. The absolute inlet and exit angles of the rotor are taken as design variables. Analytical relations between the isentropic efficiency and the flow coefficient, the work coefficient, the flow angles and the degree of reaction of the compressor stage are obtained. The results are universal and can be extended to the optimal design of a multi-stage compressor. Numerical examples are provided to illustrate the effects of various parameters on the optimal performance of the compressor stage.     

Optimal ratio of bend channel in centrifugal compressor

A numerical investigation on the flow in a bend channel by coupling the impeller with the vaneless diffuser in a centrifugal compressor with different r/b ratios (bend radius r to bend channel width b) is presented. The jet-wake effect of the impeller outlet is considered and flow pattern in the bend channel and the performance of the centrifugal compressor stage are investigated. The results indicate that there is an optimal r/b ratio for increasing the stage efficiency to the highest for a specific compressor stage. The change in r/b ratio significantly affects the flow angle of the bend channel outlet. The prime reason for the total pressure loss in the bend channel is the wall friction in the bend channel.