MATCH-MODE METHOD AND ITS NUMERICAL SIMULATION FOR ROTOR-STATOR INTERACTION SOURCE MODES AND PROPAGATION MODES IN AN ANNULAR DUCT WITH MULTI-TREATMENTS

The suppressing design of the engine nacelle in an aircraft can benefit from the development of the prediction system for the sound fields in engine ducts which includes the prediction of the source generation and that of sound propagation in ducts. First, the acoustic match mode principle between the source modes of rotor stator interaction noise and the propagation modes is presented in this paper. Second, by utilizing this principle, the theoretical prediction method for rotor stator interaction noise generation and its propagation and attenuation in an annular duct with multi treatments is developed. That means that the prediction of sound propagation and attenuation in the segmented ducts might no longer completely depend on the in duct mode measurements, and the investigation on the sound propagation and attenuation in ducts can be accomplished not only by acoustic mode measurement, but also by making use of the source prediction to determine the source modes excited by rotor stator interaction. The effects of fan speed, blade/vane numbers, axial spacing between rotor and stator on the in duct sound attenuation and generated sound power level before and after ducts (also including the sound power level of blade passing frequency and its harmonics at the inlet of ducts) have been numerically calculated by using this prediction method. The reliability of this prediction method is verified by reasonable agreement between the predicted results with measured results in references. By analyzing the results of calculating cases, some reference criteria are provided for the engineering design of the suppressing engine nacelle.

Interaction tonal noise generated by contra-rotating open rotors

Fast and accurate prediction of sound radiation of Contra-Rotating Open Rotors(CRORs)is an essential element of design methods of low-noise open rotor propulsion systems.In the present work,a previous frequency-domain model is extended to predict CROR noise.It builds explicitly the relationship between harmonic loadings and corresponding tonal noise,by which the influential parameters to noise generation can be clearly understood.The real distribu-tions of steady and unsteady blade loadings are calculated by the Nonlinear Harmonic(NLH)method.In the present hybrid approach,both the CFD and acoustic modules are solved in the fre-quency domain.To assess the accuracy of the developed method,the loading noise of a CROR is calculated and compared against results by using the time-domain FW-H module of NUMECA.The predicted sound directivities by the two methods are in good agreements.The present acoustic model in the frequency domain is proven to be accurate and have high efficiency in far-field noise prediction and data processing.Furthermore,the characteristics of the CROR interaction tonal noise are analyzed and discussed.

Numerical simulation of unsteady interaction of centrifugal impeller with its diffuser using Lagrangian discrete vortex method

In this study, an advanced Lagrangian vortex- boundary element method is applied to simulate the unsteady impeller-diffuser interactions in a diffuser pump not only for design but also for off-design considerations. In velocity calculations based on the Biot-Savart law we do not have to grid large portions of the flow field and the calculation points are concentrated in the regions where vorticity is present. Lagrangian representation of the evolving vorticity field is well suited to moving boundaries. An integral pressure equation shows that the pressure distribution can be estimated directly from the instantaneous velocity and vorticity field. The numerical results are compared with the experimental data and the comparisons show that the method used in this study can provide us insight into the complicated unsteady impeller-diffuser interaction phenomena in a diffuser pump.

抽水蓄能机组动静干涉与相位共振诱发振动故障机理及抑制方法研究

动静干涉与相位共振故障直接影响抽水蓄能电站水泵水轮机安全与稳定运行。本文以某水泵水轮机为对象,系统研究了由动静干涉产生的水力激振模式,并对其进行相位共振风险评估。通过实例计算分析了张河湾与黑麋峰抽水蓄能水泵水轮机由动静干涉引起厂房振动影响因素。同时,通过统计国内部分抽水蓄能电站水力参数,计算了动静干涉水力激振模式与相位共振风险系数RF,并提出相应预控措施。为其他大型抽水蓄能电站的振动问题提供参考,并为即将大规模建设的抽蓄电站安全稳定性提供积极借鉴意义。

基于CFD的多级轴流风机动静干涉及激励特性研究

为了探究多级轴流风机的动静干涉及激励特性,分析每级叶轮不同相位排布对风机气动性能和流场激励的影响,对五级一体化轴流风机模型进行数值模拟。分别改变每级叶轮的相位排布角度为0°、2°、4°、6°,获得轴流风机内部流场和性能参数以及每级叶轮受力情况。结果表明:随着排布角度增大,叶轮对流体挤压增大,后半段流场流动恶化,效率约下降2.1%。每级叶轮受力的主要特征频率为叶频(fBPF)及其倍频,且幅值随频率增加而快速减小。同时,排布角度对每级叶轮受力的影响也体现在流场性能和流体能量上,越稳定的流场,其特征频率越集中且振幅较高。

基于定转子槽结构协同优化的交流牵引电机电磁降噪优化设计方法

针对交流牵引电机存在电磁噪声较大的问题,提出一种基于定转子槽结构协同优化的交流牵引电机电磁降噪优化设计方法。分析了交流牵引电机电磁噪声的产生机理,阐述了在电机定转子槽底部开槽降噪的基本原理与具体设计方法,并对开槽位置与槽口尺寸进行了参数优化研究。最后对降噪效果进行了仿真验证,同时与传统降噪方法进行了对比分析,结果表明采用所提电磁降噪优化设计方法对交流牵引电机定转子槽结构进行优化处理后,在保证其效率有所增加的情况下,电磁噪声得到了显著下降,因而取得了较好的降噪效果。

长短叶片转轮动静干涉引起的水力激振模态数值分析

本文以5个长叶片和5个短叶片转轮(活动导叶数为16)为例,通过数值计算,分析了长短叶片转轮的动静干涉引起的水力激振模态问题。结果表明,长短叶片转轮动静干涉引起的水力激振模态比较复杂。在无叶区,水力激振模态“节径”数为相应倍频数,如5倍转频对应5“节径”等;在双叶栅区,激振力模态既有长(短)叶片数的特征(如15倍转频的模态的节径数为1),又有叶片总数的特征(如20倍转频的节径数为4,且模态旋转方向与转轮旋转方向相同)。本文的研究为长短叶片转轮的水泵水轮机的结构避振提供了新的方向。

宁海抽水蓄能电站机组相位共振风险评估

通过研究诱发相位共振的相关因素,消除抽水蓄能电站机组相位共振,提高抽蓄机组的运行稳定性,利用归纳分析法,从基础模型选择及模型试验对比结果、无叶区宽度比较、不同转轮叶片数与活动导叶数配比的水压脉动频率及优缺点、相位共振风险因子分析及业绩比较等几方面评估了宁海抽水蓄能电站机组由于动静干涉引起的相位共振风险。研究结果表明:宁海抽水蓄能电站基础模型选择合适,优化后模型各项稳定性指标优于基础模型;无叶区D_(0)/D_(1)=1.23属于国内抽蓄电站较高水平;10+16的转轮叶片数与活动导叶数配比合理,水压脉动频率较低;较低波速下相位共振风险因子高于国内工程经验值,但低于国外工程统计值。研究成果说明宁海抽水蓄能电站机组水力开发选型合理先进,发生相位共振风险较低,评估过程可为后续新建抽水蓄能电站评估提供一定参考和借鉴。

Numerical Simulation of Sand Erosion Phenomena in Rotor/Stator Interaction of Compressor

Sand erosion is a phenomenon where solid particles impinging to a wall cause serious mechanical damages to the wall surface. This phenomenon is a typical gas-particle two-phase turbulent flow and a multi-physics problem where the flow field, particle trajectory and wall deformation interact with each other. On the other hand, aircraft engines operating in a particulate environment are subjected to the performance and lifetime deterioration due to sand erosion. Especially, the compressor of the aircraft engines is severely damaged. The flow fields of the compressor have strongly three dimensional and unsteady natures. In order to estimate the deterioration due to sand erosion, the sand erosion simulation for a compressor is required under the consideration of the rotor-stator interaction. In the present study, we apply our three dimensional sand erosion prediction code to a single stage axial flow compressor. We numerically investigate the change of the flow field, the particle trajectories, and the eroded wall shape in the compressor, to clarify the effects of sand erosion in the compressor.

Unsteady Rotor-Stator Interaction in High Speed Compressor and Turbine Stages

The blade row interaction can alter the time-mean flow and therefore be of interest for aerodynamic design analysis. Whereas results within low subsonic turbomachines are quite numerous in the literature, there have been far fewer works which give results of blade row interaction within high speed cases. Two cases are related in this paper. First, the effects of an incoming wake on the rotor flow field of a transonic compressor are analyzed. The blade row interaction proved to be positive regarding the total pressure ratio, but negative regarding the losses. The second case concerns a transonic turbine. Particular emphasis is placed on the assessment of the deterministic correlations included in the Averaged Passage Equation System.

Experimental Analysis of the Rotor Stator Interaction Within a High Pressure Centrifugal Compressor

An analysis of the experimental results obtained by laser two focus anemometry in the rotor-stator inter-row region of a high-speed high-pressure centrifugal compressor is presented with the aim of quantifying the unsteady effects of the rotor-stator interaction. Two complementary methods are used. First, the results are analyzed in terms of the time-averaging procedure developed by Adamczyk. The purely time dependent correlations of the velocity components are quantified. They show that the unsteady interaction is mainly due to the splitter wake-vane interaction. Then, it is shown that the rotor-stator interaction produces spatial harmonics which are identified as spinning modes by means of Fourier series.

Laser Measurements in High Speed Compressors for Rotor-Stator Interaction Analysis

This paper deals with the experimental quantification of the unsteady effects of the interactions between rotor and stator rows in high speed compressors. Due to the fact that the levels of the periodic fluctuations arising from the unsteady interaction may be low compared with the random fluctuations arising from the measurement uncertainties, it is crucial to minimize the errors inherent to the used technique. The first part of the paper concentrates on technical details relative to the experimental process. The second part is devoted to the data post-processing. Two tools for analysing the rotor-stator interactions are presented. The first tool is based on a decomposition of the flow field which was initially introduced to solve numerical problems when attempting to calculate the flow field in a multi-row configuration. The second tool is based on a spectral analysis of the signal, that qualifies the interaction in a sense of circumferential spinning lobes. Experimental results obtained within both an axial and a centrifugal high speed compressors are used to illustrate the data processing. In both cases, the effects of the unsteady interaction are quantified.

Numerical Simulation of Rotor-stator Interactions in a Transonic Compressor Stage

A numerical method is developed for the simulation of rotor\|stator interactions in a compessor or turbine stage. This method solves quasi\|three\|dimensional Navier\|Stokes equations by an implicit high\|resolution finite volume approach.A fully conservative method is designed to compute the inviscid and viscous fluxes at the interface of rotor and stator grids. Numerical results of rotor\|stator interactions in a transonic compressor stage are presented. The mechanism of rotor\|stator interactions in this compressor stage is discussed in terms of the computational results.

An Extraction of the Dominant Rotor-Stator Interaction Modes by the Use of Proper Orthogonal Decomposition (POD)

The Proper Orthogonal Decomposition method is applied to the instantaneous velocity field within the rotor-stator inter-row region of a high-speed high-pressure centrifugal compressor. The processed data come from experiments and numerical simulations. In comparison with a Fourier transform, the POD gives the best modal approximation for both initial fields, in terms of the energy expressed on any given number of modes to be taken into account： to reach 98% of the total energy of the velocity field, the required number of POD modes is around nine times smaller than the number of Fourier harmonics. The individual POD modes are given and show that the unsteady rotor-stator interaction is already present in the very first modes.

Unsteady Flow Variability Driven by Rotor-stator Interaction at Rotor Exit

Numerical investigation of the unsteady flow variability driven by rotorstator interaction in a transonic axial compressor is performed. Two models with close and far axial gap between rotor and stator rows are studied in the simulation. Particular attention is attached to the analysis of mechanisms involved in driving rotor wake oscillation, rotor wake skewing and flow angle fluctuation at rotor exit. The results show that smaller axial gap is favorable to enhance the interaction in the region between two adjacent rows, and the fluctuation of the static pressure difference between two sides of rotor wake is improved by potential field from down stator, which is the driving force for rotor wake oscillation. The interaction between rotor and stator is weakened by increasing axial distance, rotor wake shifts to suction side of rotor blade with 5%-10% of rotor pitch, the absolute value of flow angle at rotor exit is less than that in the case of close interspace for every time step, and the fluctuation amplitude is also decreased.

基于定转子齿开槽的开关磁阻电机振动噪声抑制

振动噪声的抑制是近年来开关磁阻电机研究的热门领域。根据麦克斯韦张量法理论分析了径向磁拉力减小的原理,通过在定子齿顶、转子齿两侧同时开矩形槽,增大了定转子间气隙长度的同时又将一部分沿径向方向的磁通密度改变为切向方向,减小了径向磁拉力,达到抑制电磁振动的目的。利用参数化扫描的方法,对开关磁阻电机的开槽参数进行了优化,得出开槽尺寸,并对比分析开槽前后电机的径向磁拉力。运用Ansys Workbench模块分别对定转子齿开槽前后的电机定子进行模态、谐响应以及噪声分析,得到其模态固有频率、模态参与因子、振动响应频率以及声压频谱。分析结果表明:该方法有效减小了开关磁阻电机的径向磁拉力,改善了开关磁阻电机的振动和噪声。

旋翼桨-涡干扰噪声特性风洞试验研究

在中国航空工业空气动力研究院FL–10风洞中开展了旋翼桨–涡干扰噪声传播特性试验,对BO–105主旋翼40%缩比模型中等前飞速度爬升、平飞、斜下降状态的气动噪声进行了测量。首先采用Heyson洞壁干扰修正方法确定风洞试验时的旋翼下滑角,通过气流内测量阵列移动获得了桨盘平面下方完整的噪声辐射场,然后对不同飞行状态下的桨–涡干扰噪声传播特性进行了分析,得到了典型状态的声压–时间历程、频谱和声压级云图。结果表明:旋翼斜下降飞行状态出现了明显的桨–涡干扰噪声,干扰较强时桨叶前行侧和后行侧都会产生桨–涡干扰噪声,且其传播具有明显的方向性,即前行侧指向桨盘上游和桨盘下方,后行侧指向桨盘下游。

泵喷定子襟翼作动对转子非定常力抑制方法数值研究

[目的]转子非定常力是泵喷推进器轴系振动的主要激励源,其产生机理和抑制机理受转−定子干扰流动的影响,需研究其抑制方法。[方法]在泵喷推进器定子后缘引入襟翼结构,利用襟翼作动产生二次流动,改变转子入流条件,调控转−定子干扰流动,达到抑制转子非定常力的目的。以具有前置定子襟翼的Suboff全附体艇后泵喷推进器为研究对象,采用基于SST k–ω湍流模型的URANS方法和动网格技术建立可实现定子襟翼作动的数值模型。针对转子非定常力转子叶频分量的抑制,给出定子襟翼作动规律的表达式。[结果]结果显示,在襟翼作动最优控制下,泵喷的水动力性能变化不超过1%,转子轴向非定常力在转子叶频处下降了83.35%,单个转子叶片轴向非定常力在转子叶频处降低了81.80%;襟翼作动对定子尾迹与转子入流速度的调控是抑制转子非定常力的机理。[结论]研究表明,最优控制下的定子襟翼作动能够在保持水动力性能的同时使转子非定常力特征线谱得到显著抑制,可为泵喷推进器的叶频等线谱控制提供一种新的思路。

新型分段定子开关磁阻电机转矩增强和径向力减小的分析研究

开关磁阻电机由于结构简单和启动转矩大等优点应用于许多领域,然而与永磁电机相比,其表现出较低的密度转矩和较大的振动噪声。文中提出一种新型分段定子开关磁阻电机,并在每个定子块两侧增设永磁体,构成分段定子混合励磁开关磁阻电机。首先介绍了拓扑结构和原理,磁路等效法证明了永磁体对气隙磁通加强作用,同时通过有限元仿真得出永磁体对转矩密度的影响并得出优化永磁体厚度。其次建立外转子齿顶开槽模型分析径向力减小的原理,同时对不同槽口宽度和深度模型仿真分析,得到优化尺寸。最后仿真表明,分段定子混合励磁开关磁阻电机的平均转矩提高了34.2%,转矩脉动下降了19.3%,定转子重叠区间的径向力波降低了12.5%,有效降低了径向力,改善了振动噪声。

叶片出口梯形切割对离心泵蜗壳流激噪声影响的研究

为探究叶片出口梯形切割对离心泵蜗壳流激噪声的影响,以一台比转速为66的单级单吸离心泵为对象,通过定义切割宽度系数δ与径向高度系数γ,设计了9种切割方案。基于RNG k-ε湍流模型对离心泵进行全三维非定常数值模拟,在此基础上采用边界元法(boundary element method,BEM)计算内场噪声,采用结构有限元法(finite element method,FEM)耦合声学边界元方法计算外场流激噪声;分析不同切割方案下离心泵水力特性和噪声幅射特性,经试验方法验证数值计算的准确性。研究表明:动静干涉是离心泵蜗壳流激噪声产生的主要原因,合理的叶片出口梯形切割能使离心泵水力性能基本稳定的同时有效降低动静干涉强度及蜗壳流激噪声水平;声学性能最优切割方案,叶频处的进、出口监测点声压级分别下降13%和7.5%,外场噪声监测点声压级下降2.4%。