串列叶栅和叶片弯曲对角区失速和叶尖泄漏流的耦合作用

为了提高压气机叶栅的气动性能,本文针对高负荷串列叶栅进行数值模拟,研究了叶片正弯和串列叶栅对角区失速和叶尖泄漏流的耦合作用.结果表明,在串列叶栅前叶排存在比较严重的角区失速,叶片正弯能有效控制高负荷串列叶栅中的角区失速,在最优工况叶栅总损失降低了37.6％.串列叶栅中只有"前排叶片弯曲"的方案能取得与"两排叶片都弯曲"...     

基于Daubechies小波的压气机失速分析及预测

压气机旋转失速一直是航空发动机研究中的重要问题,准确分析压气机的失速状态特征,及时预测失速发生的时间对于航空发动机的研究至关重要.应用Daubechies小波对压气机动态压力信号进行分析,得出信号的低频系数,并利用方差分析对旋转失速进行预测,结果表明能有效预测压气机失速状态.     

叶片断裂破坏与气动非定常脉动的关联分析

在离心压气机实际的工况运行中,流量通常在一个区间内变化,如果流量超出稳定工作范围,在叶轮流道中可能会引起旋转失速甚至喘振等非稳定性流动现象,极易引发叶片的疲劳断裂[1].本文基于某型压气机在实际运行中发生叶片叶顶断裂事故,利用CFD软件NUMECA进行数值计算分析,主要从气动方面分析其在各个流量下的流动情况.从非定常流动特征方面深入分析其破坏机理.结果表明在一定的流量下,流场中的压力脉动非常强烈,极有可能引发叶片的疲劳破坏.本研究为压缩机叶片的疲劳破坏机理力学分析提供了可靠的理论依据和坚实的数据基础.     

打磨修理对跨声速压气机性能的影响研究

为了控制航空发动机压气机叶片损伤继续发展,通常采用孔探打磨进行修理。为研究其带来的影响,选取跨声速压气机Rotor37为研究对象,构建了不同叶高的叶片前缘打磨修理模型,采用数值模拟方法,研究了打磨修理对跨声速压气机气动性能的影响,结果表明:叶片前缘打磨修理使压气机整体性能下降,压比减小,效率降低,使堵塞点流量减小,而对失速流量点基本没有影响;不同叶高的打磨修理中心对压气机气动性能影响趋势一致影响幅度相当,但打磨叶高的不同造成压气机内部流场变化;叶片前缘打磨后,打磨处激波前马赫数增加,激波强度增大,影响效果随着叶高的增加而增加;压气机进口因为叶片打磨而造成相对动能在叶片打磨处附近降低。     

高速离心压气机变工况模拟及叶轮叶片优化研究

离心压气机作为增压器核心部件,对增压器性能有决定性影响.利用CFD模拟软件ANSyS-Fluent,以某型涡轮增压器核心部件—压气机为研究对象,进行了设计转速下的变工况数值模拟,得到了不同质量流量下离心压气机的内流场数据,通过与实验数据进行对比,验证了仿真模拟的正确性.在额定工况下,对后弯叶轮叶片出口段沿旋转方向不同倾...     

某重型燃气轮机压气机动叶弯曲变形故障分析

针对国内某热电厂首次发生的燃气轮机压气机第二级动叶顶部弯曲变形故障,从压气机进出口压力、叶片通道温度、排气温度、进口导叶(IGV)阀开度、轴承振动、余热锅炉出口烟气流量等多个监测参数入手,多参数协同分析可能造成故障的原因。在燃气轮机运行过程中,压气机出现进口静压增大0.001 2 MPa,出口压力减小0.078 2 MPa,叶片通道温度增大14.09℃,排气温度增大6.12℃,2^#轴承振动增大10.69 μm,余热锅炉出口烟气流量减少了0.25×10⁶ Nm³/s等异常现象。揭示了轴流式压气机第二级动叶叶顶弯曲变形机理,判断动叶叶顶局部弯曲与压气机旋转失速现象密切相关。若出现压气机进口压力增大,压气机出口压力减小,叶片通道温度及排气温度升高,轴承振动增大,余热锅炉出口烟气流量减小等参数的异常变化,可初步判断压气机发生旋转失速。     

轴流压气机进气旋流畸变实验与仿真研究

为深入分析旋流畸变问题,发现叶片式旋流畸变发生器产生旋流流场的机理和旋流畸变对压气机稳定性的影响机制,本文开展了旋流畸变发生器与压气机的耦合数值仿真。分析计算结果,认为叶尖脱落涡的叠加效应是产生旋流的主要机理,旋流结构对转子叶尖区域的扰流作用是造成转子提前失速的重要原因。建立了S弯进气道仿真模型,通过对S弯进气道与高亚声速压气机进行耦合仿真计算,研究了S弯进气道出口旋流流场的形成机制,初步探讨了S弯进气道出口旋流流场对压气机稳定性的影响。S弯进气道出口形成的对涡结构靠近压气机机匣,这种局部的涡结构会影响部分转子叶片叶顶区域的流动结构,从而导致压气机失速边界右移。     

燃气轮机旋转失速机理及防范对策

燃气轮机在工业领域发挥着重要的作用。随压气机向着高平均级压比、高效率和高喘振裕度方向的发展,简单叶片失速及旋转失速成为压气机不得不考虑的问题,其中,旋转失速不仅影响机器的稳定工作范围和运行可靠性,还可导致灾难性事故。因此,本文对燃气轮机常见失速机理及防范对策进行了分析,可为燃气轮机及压气机的进一步改进提供技术支持。     

亚音速离心叶轮分流叶片前缘掠形性能分析

在保证叶轮其它参数不变的情况下,设计了7种不同分流叶片前缘掠角,分别为-15°、-10°、-5°、0°、5°、10°、15°,利用ANSYS CFX软件对其进行数值模拟,并对数值方法进行实验验证,来分析分流叶片前缘掠对亚音速离心压气机气动性能的影响;研究结果表明:相比不掠而言,分流叶片前缘后掠使效率、压比降低,失速裕度和稳定工作裕度增加,分流叶片前缘前掠使效率、压比增加,失速裕度和稳定工作裕度减小;后掠增大堵塞流量,加大其叶片上载荷,而前掠减小堵塞流量和其叶片上载荷,并随角度的改变而相应的发生改变。     

大型风力发电机叶片在三维旋转状态下的气动特性分析

为了更准确地研究风力发电机在三维旋转状态下的动态失速特性,分析其气动性能,建立风力机叶片和轮毂的三维气动模型,采用计算流体力学方法,对叶片在三维旋转状态下的气动特性进行了模拟,得到叶片周围流场分布状况。分析结果表明相对于无旋转状态,三维旋转状态下,叶片表面气流有沿叶展方向的运动,改变了叶片表面压力分布,致使气流流动分离延迟,导致叶片出现失速延迟的现象,提高了叶片从风中获得能量的能力。     

Inlet Recirculation Influence to the Flow Structure of Centrifugal Impeller

Inlet recirculation is proved as an effective way for centrifugal compressor surge margin extension,and is successively used in some engineering applications.Unfortunately its working mechanism is still not being well understood,which leads to redesigning of inlet recirculation mostly by experience.Also,most study about inlet recirculation is steady to date.It is necessary to study surge margin extension mechanism about inlet recirculation.To expose the mechanism in detail,steady and unsteady numerical simulations were performed on a centrifugal compressor with and without inlet recirculation.The results showed that,with inlet recirculation,the inlet axial velocity is augmented,relative Mach number around blade tip leading edge area is significantly reduced and so is the flow angle.As the flow angle decreased,the incidence angle reduced which greatly improves the flow field inside the impeller.Moreover,inlet recirculation changes the blade loading around blade tip and restrains the flow separation on the blade suction side at the leading edge area.The unsteady results of static pressure around blade surface,entropy at inlet crossflow section and vorticity distributions at near tip span surface indicated that,at near stall condition,strong fluctuation exists in the vicinity of tip area due to the interaction between tip leakage flow and core flow.By inlet recirculation these strong flow fluctuations are eliminated so the flow stability is greatly enhanced.All these improvements mentioned above are the reason for inlet recirculation delays compressor stall.This research reveals the surge margin extension reason of inlet recirculation from an unsteady flow viewpoint and provides important reference for inlet recirculation structure design.     

自循环机匣处理对离心压气机气动性能影响分析

对比分析了带实壁机匣与带处理机匣的压气机模型在多工况下的气动性能,结果表明,在不同转速下,处理机匣结构都具有不同程度的扩稳作用,但同时也造成绝热效率有所降低,而且峰值效率损失随着转速增大而加剧;处理机匣前后槽口与叶顶通道形成的回流运动可有效地削弱激波与间隙泄漏流的强度以及二者的相互作用,有利于改善叶轮通道的气体流通性。     

EXPERIMENTAL INVESTIGATION OF ROTATING STALL FOR A LOW-SPEED CENTRIFUGAL COMPRESSOR

Unsteady flows and rotating stall of a low-speed centrifugal compressor are investigated by measuring vaneless diffuser wall static pressure fluctuation and internal flow fields at different small flow fluxes. During the experiment, firstly the real time static pressure fluctuations on the vaneless diffuser shroud at different circumferential and radial position were acquired by high-frequency dynamic pressure transducers. Discrete Fourier transformation analysis and cross-correlation analysis were applied to the experimental results to ascertain the rotating stall beginning operation conditions and stall cells numbers and rotating speed. Secondly, the vaneless diffuser inlet flow angle distribution along diffuser width direction was acquired by single hotwire, which was compared with SENOO＇s analysis results. At last, the internal flow fields of the centrifugal compressor were investigated with a particle image velocimetry （PIV） system at different small flow fluxes. The flow field development of vaneless diffuser and blade flow passage are given at rotating stall conditions. The experiments enrich the understanding of rotating stall flow phenomenon of the low-speed centrifugal compressor and provide full experiment data for designing high performance centrifugal compressor.     

高速离心压缩机旋转失速的全流场数值模拟

使用商业计算流体动力学(Computational fluid dynamics,CFD)计算软件CFX求解三维雷诺平均的Navier-Stokes方程组,结合出口气腔模型对某带无叶扩压器的离心压缩机的旋转失速现象进行数值模拟。为了准确地模拟小流量下的失速流动现象,在CFD计算中采用包括蜗壳在内的全场网格。首先使用定常计算得到该离心压缩机的稳态性能曲线,并和试验测量值进行比较。然后引入出口气腔模型,模拟离心压缩机内的旋转失速流动。在小流量下模拟得到离心压缩机内部流场的非定常流动现象。分析气腔模型不同参数对失速流动的影响,气腔体积越大,计算得到的失速频率越低。     

非设计工况下带分流叶片半开式离心叶轮内部流动特性数值研究（英文）

In order to investigate the complex flow characteristics inside an unshrouded centrifugal impeller with splitter blades at off-design conditions, and analyze its influence on pump operation stability, a numerical simulation study was carried on using the curvature-corrected SST-CC turbulence model; the head and efficiency accorded with experimental results. The pressure fluctuation, unsteady radial force and velocity were analyzed quantitatively and the numerical results indicate this: the peak to peak value of pressure fluctuation in the impeller channel gradually increases in the flow direction and at 0.49 Qn, the slope of peak to peak value to normalized impeller channel behind the splitter blade is 8.57 times greater than that before the splitter blade. The greater the flow rate deviates from the design condition, the larger the peak to peak value of the pressure fluctuation and radial force; in particular at 0.27 Qn, the maximum radial force is 194.29% greater than that of the design condition. When the operating flow rate is smaller than0.83 Qn, the stall occurs and the stall vortex could block the impeller discharge; as the flow rate decreases further, the pressure amplitude at rotational frequency gradually increases in the impeller channel and the prevailing frequency changes from the blade passage frequency(BPF) to the rotating stall frequency in the diffuser. The tip leakage vortex(TLV) is generated in the tip region and rotated move downstream in the impeller flow channel, and the backflows appear on the blade suction side and in the tip and the tongue regions; the smaller the flow rate, the more serious the TLV and backflow phenomenon. The rotating stall causes uneven flow in the impeller channel, increasing the pressure fluctuation and the radial force, and resulting in an imbalance of the impeller rotation.     

LP compressor blade vibration characteristics at starting conditions of a 100 MW heavy-duty gas turbine

In this paper are presented the blade vibration characteristics at the starting conditions of the low pressure multistage axial compressor of heavy-duty 100 MW gas turbine. Vibration data have been collected through strain gauges during aerodynamic tests of the model compressor. The influences of operating modes at the starting conditions are investigated upon the compressor blade vibrations. The exciting mechanisms and features of blade vibrations are investigated at the surge, rotating stall, and buffeting flutter. The influences of operating modes upon blade dynamic stresses are investigated for the first and second stages. It is shown that a high dynamic stress peak of 120 MPa can occur in the first stage blades due to resonances with stall cell excitations or with inlet strut wake excitations at the stalled conditions.     

轴流压气机叶顶端区流场周向传播特征及其预测

以低速单转子轴流压气机为对象,采用全圆周计算模型,以叶顶泄漏流周期性非定常波动为切入点,通过相对坐标系和绝对坐标系下信号数据的坐标变换、快速傅里叶变换和滤波分析,分析叶顶端区非定常波动特征沿叶片弦长的调频特性,研究占主导地位的非定常波动频率成分沿圆周方向的传播特征,得到占主导地位频率成分的调频关系和周向传播特征在压气机节流过程中的演变规律,揭示出近失速工况附近机匣壁面压力自相关系数降低的流体力学原因。结果表明,由叶顶泄漏流周期性非定常波动主导的叶顶端区流场特征是失速先兆信号分析和预测的流场依据。参考系、探针监测位置和分析方法的选取对分析结果有着重要影响,对同一流动现象可获得不同侧面的多样性表现特征。所得结果一方面为计算和试验数据的对比分析提供参考,另一方面也为不同流动特征的统一流体力学机理解释提供指导。