机载离心式制冷压缩机叶轮级流动仿真研究

离心式制冷压缩机对机载蒸汽压缩制冷系统有重要影响;大流量离心制冷压缩机的运行效率远大于小流量压缩机效率,针对现有的双级小流量离心制冷压缩机,通过实验测试和CFD仿真,对制冷剂R134a在泵式叶轮内的流动进行了分析。结果表明:在所测试参数条件下,叶轮进口靠近压力面处的制冷工质出现明显的二次流现象,气体流动出现盖面分离,叶轮内部损失较大;改变叶轮叶片出口安装角可提高效率及压比;针对不同叶轮叶片数的仿真计算对比,可确定在所设计模型中最佳叶片数。     

不同加载形式对离心压缩机性能的影响

设计了一款小流量离心式压缩机,通过改变叶片角得到三种不同加载形式的压缩机转子叶轮,同时装配相同的无叶扩压器。利用数值模拟方法研究了不同加载形式对压缩机性能的影响规律。研究表明,采用后加载的负荷分布形式设计的叶轮具有最高的压比,前加载形式叶轮具有最高的效率;后加载形式叶轮的叶顶泄漏损失和叶型损失均最小,前加载形式最大,中加载形式介于两者之间。     

变流量工况下小型离心压气机多目标优化设计

为提高离心压气机变流量工况下的性能,基于三维流场分析研究了离心压气机叶片几何参数对其变工况气动性能的影响规律;基于相关性分析建立了降阶的优化设 计变量空间,采用拉丁超立方试验设计、Kriging模型和NSGA-Ⅱ算法进行了离心压气机叶轮变流量工况多目标优化。优化后,叶轮设计流量的压比提高6.43%,效率提高3.99%;小流量时压比提高5.62%,效率提高3.52%;内部流动损失减少,喘振流量减小2.7%,阻塞流量增加6.85%,稳定工作范围得到扩宽。     

轴流压缩机与离心压缩机特点比较表

比较项目轴流式离心式适用流量范围 (m3/min)>1000<1300适用压比中低压比高中压比效率89%~91%普通叶轮小于80%三元流叶轮83%左右调节方式静叶可调或转速可调进口节流调节或转速可调调节范围 调节范围宽,适应高炉各不同工况点调节范围很有限,难以满足不同工况需否放风一不需要放风需放风调节稳定性风量风压波动小风量风压波动大噪音较低较高经济性高(能耗小)低(能耗大)轴流压缩机与离心压缩机特点比较表     

基于CFD和多目标算法的离心叶轮参数优化

为了研究叶片出口安装角和叶片数对叶轮气动性能优化的影响,对某离心压缩机叶轮建立理论数值模型,利用多目标遗传算法对模型寻优。对优化的结果圆整处理后进行参数化建模,并通过CFD叶轮在设计工况点压缩比提高3.57%,等熵效率提高0.79%,叶轮整体情况得到改善,可为离心压缩机叶轮的优化设计提供参考。     

叶轮损失模型对离心压缩机性能预测的影响

针对目前离心压缩机损失模型的差异性,在总结离心压缩机叶轮损失模型的基础上,提出在计算各截面参数时采用多变系数替换绝热指数的方法.并利用MATLAB编写程序计算压缩机在不同流量和不同转速下的压比和效率.通过和单级离心压缩机性能实验数值比较,分析叶轮损失模型对压缩机性能的影响,得出了采用简化的叶轮损失模型对压缩机效率影响较大而对压比影响较小的结论.     

长叶片扩压器稠度对气动性能影响研究

以某离心压缩机为研究对象,通过改变长叶片扩压器的叶片数和叶片弦长2种方式对叶片稠度进行改变,利用数值模拟方法,以最大效率和稳定工作范围为判断依据,结合特性曲线,针对长叶片扩压器稠度的变化范围,分析了长叶片稠度的改变对离心压缩机气动性能的影响。得出如下结论:针对长叶片扩压器,不同于传统对扩压器最优稠度的选择,扩压器的稠度值在1.203 3附近时离心压缩机能达到较高的等熵效率和压比,同时具有较宽的稳定工作范围。     

叶片载荷分布对小流量离心叶轮性能影响研究

应用五次Bezier多项式来控制环量沿离心叶轮叶片的子午流线的分布方法,分别设计了将载荷集中于叶片前部、中部及尾部三种载荷分布方式的叶轮,并应用三维数值模拟研究了不同载荷分布方式对小流量系数离心叶轮性能的影响。研究结果表明:叶片载荷集中在前部的叶轮性能优于集中在中部及尾部的叶轮,其内部流动损失最小;当将载荷集中在前部时,叶轮效率曲线朝大流量区域移动,将载荷集中在叶片尾部时,叶轮效率曲线会朝小流量区域移动,且载荷集中在叶片前部的叶轮压比高于载荷集中在叶片中部及尾部的叶轮。载荷集中在叶片前部的叶轮熵增最低,其叶轮出口速度比载荷集中于叶片尾部和载荷集中于叶片中部的叶轮出口速度分布更均匀,流动损失更小。     

离心压缩机大流量三元流叶轮的试验研究

本文对多级离心压缩机用的大流量三元叶轮的轮毂比大,相对宽度大,进口马赫数高,又要求轴向尺寸小的气动特点。论述了给定载荷的叶片设计方法和最佳叶片载荷分布型状;在无粘准三元设计计算中如何采用熵梯度使叶轮进口和出口流场计算与实际粘性流动相符合等问题。     

基于数据挖掘方法的压缩机二元叶轮优化研究

以离心压缩机后弯叶轮叶片进口宽度、出口宽度、进口安装角和出口安装角作为设计变量;质量流量、等熵效率和能量头作为性能参数。通过拉丁抽样选取40个样本点,分别在NUMECA软件中计算。采用数据挖掘的方法对计算结果进行分析,得到设计变量对性能参数的影响关系,并确定最优设计参数。结果显示,在流量一定的情况下,对比原始模型及优化模型,二元叶轮的等熵效率提升3.84%,压比提高1.58%。     

高压比离心压缩机叶轮的优化设计

设计了一种空气工质高压比离心式压缩机三元叶轮,并对其流场进行了分析。在此基础上,对此压缩机叶轮的主要几何参数进行了进一步优化设计,并分析了其对压缩机性能的影响。     

Robust design optimization method for centrifugal impellers under surface roughness uncertainties due to blade fouling

Blade fouling has been proved to be a great threat to compressor performance in operating stage. The current researches on fouling-induced performance degradations of centrifugal compressors are based mainly on simplified roughness models without taking into account the realistic factors such as spatial non-uniformity and randomness of the fouling-induced surface roughness. Moreover, little attention has been paid to the robust design optimization of centrifugal compressor impellers with considerations of blade fouling. In this paper, a multi-objective robust design optimization method is developed for centrifugal impellers under surface roughness uncertainties due to blade fouling. A three-dimensional surface roughness map is proposed to describe the nonuniformity and randomness of realistic fouling accumulations on blades. To lower computational cost in robust design optimization, the support vector regression (SVR) metamodel is combined with the Monte Carlo simulation (MCS) method to conduct the uncertainty analysis of fouled impeller performance. The analyzed results show that the critical fouled region associated with impeller performance degradations lies at the leading edge of blade tip. The SVR metamodel has been proved to be an efficient and accurate means in the detection of impeller performance variations caused by roughness uncertainties. After design optimization, the robust optimal design is found to be more efficient and less sensitive to fouling uncertainties while maintaining good impeller performance in the clean condition. This research proposes a systematic design optimization method for centrifugal compressors with considerations of blade fouling, providing a practical guidance to the design of advanced centrifugal compressors.     

Fluid-structure interaction analysis and lifetime estimation of a natural gas pipeline centrifugal compressor under near-choke and near-surge conditions

Up to present, there have been no studies concerning the application of fluid-structure interaction(FSI) analysis to the lifetime estimation of multi-stage centrifugal compressors under dangerous unsteady aerodynamic excitations. In this paper, computational fluid dynamics(CFD) simulations of a three-stage natural gas pipeline centrifugal compressor are performed under near-choke and near-surge conditions, and the unsteady aerodynamic pressure acting on impeller blades are obtained. Then computational structural dynamics(CSD) analysis is conducted through a one-way coupling FSI model to predict alternating stresses in impeller blades. Finally, the compressor lifetime is estimated using the nominal stress approach. The FSI results show that the impellers of latter stages suffer larger fluctuation stresses but smaller mean stresses than those at preceding stages under near-choke and near-surge conditions. The most dangerous position in the compressor is found to be located near the leading edge of the last-stage impeller blade. Compressor lifetime estimation shows that the investigated compressor can run up to 102.7 h under the near-choke condition and 200.2 h under the near-surge condition. This study is expected to provide a scientific guidance for the operation safety of natural gas pipeline centrifugal compressors.     

叶片前缘载荷分布对大流量系数离心压缩机叶轮性能的影响

本文主要针对大流量系数模型级的叶轮叶片载荷分布进行研究,通过改变叶片前缘载荷(叶片0~20%无量纲中弧线长)分布来设计不同形式叶轮,并进行了数值模拟分析,通过对流场的分析和性能曲线的对比,研究叶片前缘载荷对叶轮性能的影响,研究发现不同的载荷分布形式使得压缩机的性能曲线也有不同程度的左右偏移,叶轮内部流场也有较大差别,分析结果可为大流量系数模型级叶轮结构的优化设计与性能提高提供理论依据,同时为大流量系数压缩机的开发提供参考。     

离心压缩机叶片前缘形状对强度计算的影响

以某大型离心式压缩机的闭式叶轮为研究对象,在研究叶片前缘形状对叶轮性能的影响过程中,利用CAD软件Solidworks对3个闭式叶轮进行三维实体造型,并运用有限元软件ANSYS进行数值模拟计算.主要对比研究了钝形、圆形和椭圆形前缘对叶轮强度的影响.数值计算的结果表明:叶片前缘几何形状对离心压缩机的结构强度具有影响.     

离心压缩机叶轮分流叶片对性能的影响

某离心压缩机三元流叶轮由于在入口处无加工空间,因此改为带有分流叶片的叶轮。为了验证改造后的叶轮是否满足设计参数以及和原始叶轮的异同,采用了数值方法对原始叶轮和改造后的叶轮进行了数值分析。结果表明,两种均满足设计要求,并且改造后的叶轮性能要好于原始叶轮。这是由于原始叶轮在入口处的相对马赫数较大,因此所引起的摩擦损失也略大。     

叶片梯度角对压气机叶轮固有频率的影响规律

增压器叶轮固有频率分布对其可靠性寿命起至关重要的作用.为获取压气机叶轮几何尺寸对叶轮固有频率的影响规律,提出了与叶片厚度和叶片悬臂长度相关的叶片梯度角概念,采用Con-cepts NREC软件进行叶轮系列化设计,结合ANSYS有限元分析软件进行叶轮固有频率及强度模拟计算,并通过叶轮模态测试系统进行了8个代表性尺寸的铣削...     

离心压缩机叶轮主动再制造设计和时机调控方法

针对目前再制造中零部件经常出现的“滞后再制造”或“提前再制造”问题,提出了离心压缩机叶轮主动再制造设计和时机调控方法。选取关键零部件特征结构,结合疲劳寿命理论和叶轮设计基础,建立结构与服役性能的映射模型,实现关键零部件的主动再制造设计。通过优化特征结构参数,改变零部件服役寿命和再制造临界点,并与产品综合性能劣化拐点相匹配,完成零部件主动再制造时机调控。以PCL8L型叶轮为例,基于构建的叶轮特征结构(出口安放角、入口安放角和后缘厚度)与寿命之间的量化关系模型,在当前定期维护需求下,通过理论计算和仿真分析,验证了主动再制造设计和时机调控方法的可行性。     

EXPERIMENTAL STUDY ON HIGH-SPEED CENTRIFUGAL PUMPS WITH DIFFERENT IMPELLERS

The experimental study is carried out on high-speed centrifugal pumps with three different impellers. The experimental results and analysis show that high-speed centrifugal pumps with a closed complex impeller can achieve thehighest efficiency and the lowest head coefficient followed by those with half-open impeller and open-impeller, and canobtain much easily stable head-capacity characrastic curve, while those with a half-open complex impeller can't. Thecharacteristic curve with a open impeller is almost constant horizontal line before dropping sharply. The results also showthat the axial clearance between pump casing and impeller can influence greatly on the performance of centrifugal pumps.     

Assessment of fatigue life of remanufactured impeller based on FEA

Predicting the fatigue life of remanufactured centrifugal compressor impellers is a critical problem. In this paper, the S-N curve data were obtained by combining experimentation and theory deduction. The load spectrum was compiled by the rain-flow counting method based on the comprehensive consideration of the centrifugal force, residual stress, and aerodynamic loads in the repair region. A fatigue life simulation model was built, and fatigue life was analyzed based on the fatigue cumulative damage rule. Although incapable of providing a high-precision prediction, the simulation results were useful for the analysis of fatigue life impact factors and fatigue fracture areas. Results showed that the load amplitude greatly affected fatigue life, the impeller was protected from running at over-speed, and the predicted fatigue life was satisfied within the next service cycle safely at the rated speed.