基于一类改进谐波小波的离心风机旋转失速特征分析

通过对谐波小波频谱边缘突变点应用Hanning窗进行光滑处理，改善了谐波小波的时域衰减特性，并给出实现算法。通过对离心风机旋转失速的试验研究，应用改进的谐波小波时频等高线图对不同测量部位的动态压力信号进行时频分析，得出在不同导流器开度下离心风机不同的特征和弱失速区域的能量间歇现象，风机最高效率线与失速边界线比较接近，并且在导流器小开度下会出现交叉，说明弱失速区域应引起运行、维修人员足够重视。图10参8     

基于谐波小波变换的4_73风机压力侧失速特性分析

在对离心风机压力侧失速的形成机理定性分析的基础上,通过对4-73风机的实验研究,发现4-73风机存在压力侧失速现象,并采用谐波小波变换对于压力侧失速的时频特性进行了分析。在分析中,对于时域定位能力较差的正交谐波小波进行频域光滑处理,在旋转失速的分析中引入非正交谐波小波变换,分析结果证明了谐波小波变换对于离心风机旋转失速特性分析的有效性。     

基于SDP与图像匹配的离心风机失速实时检测

为了及时、准确地对离心风机旋转失速进行检测,提出了一种基于对称点模式(SDP)分析与图像匹配相结合的方法.在G4-73No.8D离心风机实验台上进行旋转失速渐进过程实验,采集机壳内壁气体动态压力信号,对该压力信号进行SDP变换,建立风机正常运行和失速状态下的SDP模板图;选取风机80个采样点内的动态压力信号进行SDP变换,并与模板图进行图像匹配,每隔16个采样点进行一次,直至风机由正常运行到完全失速.通过小波变换方法离线检测实验信号失速起始点,以验证本方法的准确性.结果表明:该方法可在0.35s内准确检测到弱失速起始点,在0.05s内准确检测到强失速起始点.     

预防双馈风机调频期间失速的功率轨迹预设策略

为解决双馈风机阶跃惯性控制过程中易导致频率二次跌落和分机失速的问题,在斜坡形阶跃惯性控制方法基础上考虑风机有效旋转动能,建立转速减速阶段增发功率、加速阶段降低功率与线性下降阶段时间的数学关系,计算风机有功功率线性下降阶段不引起风机失速的最大持续时间,对功率轨迹线性下降阶段时间加以约束,使风机具有与斜坡形阶跃惯性控制相同频率支撑效果,同时防止风机失速、减少二次频率跌落。利用EMTP-RV平台对不同扰动大小、渗透率、风速情形进行仿真,验证了所提方法的有效性。     

离心压气机宽无叶扩压器旋转失速的数值研究

无叶扩压器作为离心压气机的重要部件,研究其内部旋转失速的诱发过程及机理对离心压气机无叶扩压器旋转失速的主动控制具有重要意义.利用ANSYS平台对离心压气机建模并对其旋转失速过程进行非稳态数值模拟.结果表明:离心压气机无叶扩压器旋转失速是随着流量的逐渐减小建立起来的,失速工况点位于性能曲线的负斜率区;无叶扩压器内部,低速...     

电站轴流风机旋转失速工况下的叶轮静力特性研究

基于Realizable k-ε湍流模型对某电站轴流风机旋转失速工况下的流场进行了数值模拟,并基于有限元分析方法结合流固耦合理论,利用Ansys软件对旋转失速工况下的风机叶轮进行流固耦合研究.结果表明:风机进入旋转失速状态后,叶轮内存在一个与叶轮旋转方向相同的失速团;叶轮的等效应力分布主要受离心力载荷的影响,旋转失速对叶轮等效应力分布的影响较小,叶轮的最大等效应力小于材料的屈服强度,未达到屈服状态;气动力载荷对叶轮的总变形量有显著影响,旋转失速发生后,失速团中心所在区域的总变形量最大,较设计工况下增大了72.2%.     

离心压气机无叶扩压器旋转失速诱发的能量损失机制研究

利用ANSYS软件分别对带宽、窄无叶扩压器的离心压气机进行数值模拟,研究了在旋转失速诱发过程中离心压气机无叶扩压器的流场分布及能量损失机制.研究表明,窄无叶扩压器失速诱发时盘盖侧边界层发生局部回流并在叶高方向向内延伸,而宽无叶扩压器失速与扭曲的核心流和回流混合密切相关.随着流量的减小,扩压器内能量损失逐渐增加,旋转失速...     

宁海电厂引风机失速分析

通过对风机失速机理的分析,结合电厂生产实际和事故处理案例,对国产风机的运行性能作一剖析．提出了风机失速的原因、处理方法,对电厂风机的失速事故处理有一定的借鉴意义。     

轴流风机失速预警及保护逻辑研究

轴流风机失速过程是风机运行状态快速变化的过程,运行人员大多时候来不及处理,机组已发生RB、跳闸等事故。选取并列运行的2台轴流风机电流偏差、电流变化率、炉膛负压及一次风母管压力等作为风机失速的表征量,在轴流风机发生失速先兆时发出预警,在轴流风机发生失速时,快速形成失速判据,并通过热工逻辑形成联锁保护措施,旨在减轻运行人员运行压力的同时进一步提高机组运行安全可靠性。     

压缩机旋转失速发展传播的计算分析

针对实际运行过程中某型压缩机首级叶轮叶片断裂的问题,利用CFD软件Numeca搭建一个基于完整真实的三维几何结构的离心压缩机内部流场数值分析平台,选用实际运行工况进行计算,发现由于进气室和进气导叶的设计存在一定的问题,导致首级叶轮前的流场畸变,从而诱发压缩机首级叶轮失速;通过进行非定长流动计算,动态模拟了旋转失速的发展传播过程,得到了比较真实的旋转失速的压力脉动情况,为该机组产品的叶轮叶片断裂问题的研究找到一个突破口,并为进一步研究分析提供了充足的数据资料.     

Numerical simulation of rotating stall in a centrifugal compressor with vaned diffuser

This paper reports a numerical study on the process from normal operating conditions to rotating stall in a cen-trifugal compressor with vaned diffuser.The purpose is to better understand the flow characteristics near stallpoint under the interactions between centrifugal impeller and vaned diffuser.Numerical results show that undercertain conditions just preceding stall point the tip leakage vortex begins to fluctuate at roughly half of the bladepassing frequency.This phenomenon is similar to rotating instability in axial compressors.With the flow rate re-duced further the impeller stalls and five stall cells propagating at a frequency of 85 percent of impeller rotationspeed are found.     

Natures of rotating stall cell in a diagonal flow fan

In order to clarify the natures of a rotating stall cell, the experimental investigation was carried out in a high specific-speed diagonal flow fan. The pressure field on the casing wall and the velocity fields at the rotor inlet and outlet were measured under rotating stall condition with a fast response pressure transducer and a single slant hot-wire probe, respectively. The data were processed using the "Double Phase-Locked Averaging (DPLA)" technique, which enabled to obtain the unsteady flow field with a rotating stall cell in the relative co-ordinate system fixed to the rotor. As a result, the structure and behavior of the rotating stall cell in a high specific-speed diagonal flow fan were shown.     

Experimental Investigations of Micro Air Injection to Control Rotating Stall

Steady discrete micro air injection at the tip region in front of the first compressor rotor has been proved to be aneffective method to delay the inception of rotating stall in a low speed axial compressor.Considering the practicalapplication a new type of micro injector was designed and described in this paper,which was imbedded in thecasing and could be moved along the chord.In order to verify its feasibility to other cases,such as high subsonicaxial compressor or centrifugal compressor,some other cases have been studied.Experimental results of the samelow speed axial compressor showed that the new injector could possess many other advantages besides success-fully stabilizing the compressor.Experiments performed on a high subsonic axial compressor confirmed the ef-fectiveness of micro air injection when the relative velocity at the blade tip is high subsonic.Meanwhile in orderto explore its feasibility in centrifugal compressor,a similar micro injector was designed and tested on a lowspeed centrifugal compressor with vaned diffuser.The injected mass flow was a bit larger than that used in axialcompressors and the results showed micro injection could also delay the onset of rotating stall in the centrifugalcompressor.     

Features of Rotating Stall Cell in a Diagonal Flow Fan（in Case of Mid-loading Rotor）

The structure and behavior of rotating stall cell were experimentally clarified in a diagonal flow fan. The specific-speed of the fan was 1140 (r/min, m3/min, m), and the total pressure-rise coefficient at design flow-rate was 0.345. The static pressure on outer casing wall and the total pressure at rotor inlet and outlet were measured using a high response pressure transducer. The measured data were processed by the use of DPLA technique, and the structure and behavior of rotating stall cell were obtained. As a result, the stall cell extent for circumferential and spanwise direction and the pressure distributions inside stall cell were clarified. The details of stall cell propagation were also shown.     

Dynamical System Analysis of Unsteady Phenomena inCentrifugal Compressor

INTRODUCTI0NUnsteadyphenomenaappearedinacentrifugalcompressorsystematlowflowratearecharacterizedbysurgeandrotatingstall.Thesurgeisknowntocauseoscillationswithlargeamplitudeofthefiowrateandthepressurerisethrough0utacompressorsys-tem.Ontheotherhand,ther0tatingstallcauseslocalflowoscillationsandappearsinsomepartsofacompressor,suchastheinducer,theimpellerandthediffuser-Sincetheydeterioratethecompressorperfor-manceands0metimesleadtothesystembreakd0wn,itisimportanttoknowthephysicalmechanismsofth…     

Stall inception process and prospects for active hub-flap control in three-stage axial flow compressor

The possibility to apply the active hub-flap control method, which is a proven rotating stall control method for a single-stage compressor, to a 3-stage axial compressor is experimentally discussed, where complex rotating stall inception processes are observed. The research compressor is a 3-stage one and could change the stagger angle settings for rotor blades and stator vanes. Sixteen rotor blade/stator vane configuration patterns were tested by changing stagger angle for the stator vanes. By measurement of surface-pressure fluctuation, stall inception proc- esses are investigated and the measured pressure fluctuation data is used as a predictive signal for rotating stall. The experimental results show that the stall detection system applied to active hub-flap control in a single-stage compressor could be usefully applied to that in a 3-stage compressor with a more complex stall inception process.     

Numerical Simulation of Active Suppression of Rotating Stallin Axial Compression Systems

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