机匣处理抽吸环槽位置对离心压气机性能影响

在高转速下跨声速离心压气机往往暴露出流量范围过窄的问题,难以满足变工况增压柴油机对宽广流量范围的需求。通过数值分析研究了抽吸环槽子午轴向位置对压气机性能的影响。结果表明,压气机对开槽位置比较敏感,在高转速下只有适当的开槽位置才能有效带走堆积在分流叶片前缘上游附近的低能流体,最大程度改善其内部流动,拓宽其流量范围。采用优化后的机匣处理结构后,压气机的稳定工作范围由11.86%拓宽到15.83%。     

离心压气机机匣处理与导叶轮缘放气的扩稳机理分析及比较

采用数值模拟方法对导叶轮缘放气、进气回流及周向槽机匣处理扩大离心压气机稳定工作范围进行研究,并与实壁机匣离心压气机特性进行对比,分析三种处理方式扩大压气机稳定工作范围的机理。结果表明,导叶顶部吸力面分离流动和间隙泄漏流相互作用导致压气机失速。导叶轮缘放气将吸力面分离流动产生的低能流团吸除,减弱了顶部通道堵塞。进气回流给顶部进气添加负预旋,减小了顶部来流攻角,能抑制吸力面流动分离。周向槽机匣处理减弱了顶部间隙泄漏向叶轮进口的回流。三种处理方式都能减弱顶部通道堵塞、推迟压气机失速发生,而进气回流和导叶轮缘放气具有较大的扩稳能力。     

离心压气机机匣处理多工况性能预测与分析

机匣处理作为一种高效、经济的扩稳技术,越来越多的被用以提高压气机的稳定工作裕度。为了研究机匣处理对离心压气机多工况性能的影响,本文对3种进气回流机匣结构的压气机模型和无机匣处理的实壁压气机模型分别进行了数值仿真分析。数值计算结果与最优模型的试验结果吻合较好,比较准确的预测了喘振边界的位置,验证了计算方法的可靠性。结果表明,只有结构合理的进气回流机匣处理才能在各个转速下均显著扩大压气机小流量的稳定工作范围,其中机匣处理的开槽位置和前置导流挡板对其性能有着重要影响。     

Stall inception and warning in a single-stage transonic axial compressor with axial skewed slot casing treatment

Characteristic changes in the stall inception in a single-stage transonic axial compressor with an axial skewed slot casing treatment were investigated experimentally. A rotating stall occurred intermittently in a compressor with an axial skewed slot, whereas spike-type rotating stalls occurred in the case of smooth casing. The axial skewed slot suppressed stall cell growth and increased the operating range. A mild surge, the frequency of which is the Helmholtz frequency of the compressor system, occurred with the rotating stall. The irregularity in the pressure signals at the slot bottom increased decreasing flow rate. An autocorrelation-based stall warning method was applied to the measured pressure signals. Results estimate and warn against the stall margin in a compressor with an axial skewed slot.     

基于CFD的离心压缩机整级性能优化设计

本文采用CFD技术研究离心压缩机整级性能优化设计方法.首先用一元理论进行初始设计,应用全三维流场分析的方法分析叶轮、扩压器以及回流器叶片参数变化对压缩机性能的影响.在此基础上,对主要几何参数进行了优化设计.研究结果表明;通过在压缩机运行过程中调节扩压器叶片的角度,可以使压缩机的最大效率和工况范围均得到改善.对于本模型的压缩机,效率可提高3％以上.优化设计后压缩机整级气动性能得到明显改善.     

十级高压压气机气动方案设计的优化

对HARIKA程序进行改进,创新性地修正了效率模型并引入Koch失速静压升系数模型,采用E3十级高压压气机气动特性试验数据验证此改进HARIKA程序,结果表明改进HARIKA程序对压气机100%转速失速边界的预估精度达到了99%。采用NSGA-II多目标遗传算法进行气动方案设计优化,优化后的方案与初始方案相比设计点的总效率提高了3.4%,喘振裕度提高了6%;通过调节进口导叶和前五级静子叶片的安装角,使得优化方案在非设计转速下的特性也得到了提高。     

Experimental and Computational Analysis of the Unstable Flow Structure in a Centrifugal Compressor with a Vaneless Diffuse

The unstable flow phenomena in compressors, such as stall and surge, are closely related to the e ciency and the operating region. It is indispensable to capture the unstable flow structure in compressors and understand the mechanism of flow instability at low flow rates. Cooperated with the manufacturer, an industrial centrifugal compressor with a vaneless di user is tested by its performance test rig and our multi-phase dynamic measurement system. Many dynamic pressure transducers are circumferentially mounted on the casing surface at seven radial locations, spanning the impeller region and the di user inlet region. The pressure fields from the design condition to surge are measured in details. Based on the multi-phase dynamic signals, the original location of stall occurring can be determined. Meanwhile, the information of the unstable flow structure is obtained, such as the circumferential mode and the propagating speed of stall cells. To get more details of the vortex structure, an unsteady simulation of this tested compressor is carried out. The computational result is well matched with the experimental result and further illustrates how the unstable flow structure in the impeller region gradually a ects the stability of the total machine at low flow rates. The dynamic mode decomposition(DMD) method is applied to get the specific flow pattern corresponding to the stall frequency. Both experimental and computational analysis show that the flow structure at a particular radial location in the impeller region has a great impact on the stall and surge. Some di erences between the computational and experimental result are also discussed. Through these two main analytical methods, an insight into the unstable flow structure in an industrial compressor is gained. The result also plays a crucial role in the guidance of the compressor stabilization techniques.     

改变进气通道结构提高离心压缩机进口导叶调节性能

改变离心压缩机的进气通道结构,以提高其进口导叶的调节性能。根据对预旋、阻力影响因素的定性分析,提出了增加导叶尾缘处当量预旋半径的改进思路。基于该思路设计了6种改进方案,并通过数值模拟对各方案的改进效果以及改进思路的合理性进行了验证。     

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。     

抽吸孔数目对孔式机匣处理方式效果的影响

试验与数值计算表明,孔式机匣处理方式可以有效扩大半开式离心压气机的稳定工作范围并且在大部分工作范围内不会显著降低压气机的效率.数值计算结果同时表明,抽吸孔数目改变对采用孔式机匣处理方式的压气机整体性能影响不大,受影响相对比较明显的性能参数是堵塞裕度.对于抽吸孔总数为48、64及80三种情况,抽吸孔数目增加时,压气机的失...     

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.     

Numerical study on near-stall flow unsteadiness in an axial compressor with casing treatment

Time-accurate numerical calculations were performed to investigate unsteady flow features in a low-speed axial compressor. The test compressor has axial skewed slots over the rotor tip region as casing treatment to improve the stall margin. The calculated data are in good agreement with the measured data. This paper reports the effect of casing treatment and flow unsteadiness on the rotor near stall by examining the flows in the smooth wall and casing treatment cases. The axial skewed slot can remove the blockage induced by the tip clearance leakage flow by removing and injecting the flow near the tip. However, for the casing treatment case, blockage is induced near the hub because the hub-corner stall is caused by a decrease in the axial momentum in this region. The tip leakage flow has inherent unsteadiness in the smooth wall case caused by the relatively large tip clearance, whereas the hub-corner stall has unsteadiness in the casing treatment case. The two types of unsteadiness have functions in inducing stall inception. Furthermore, axial slots of different sizes were tested to examine the effect of slot geometry on rotor flow stability. The change in flow structure related to the stall inception was subject to flow injection through the recirculation in the slots.     

轴流压缩机周向槽处理机匣的试验分析

用亚音单级轴流压缩机试验台的孤立转子,进行了自行设计的周向槽机匣的试验,根据试验数据,对比分析了周向槽处理机匣和实壁机匣的总性能曲线,并详细地剖析了近失速时两种机匣的基元性能曲线,对结构简单的处理机匣的扩稳机理进行了分析。     

离心压缩机喘振特性及喷射扩稳研究

以某单级离心压缩机为研究对象,搭建工况动态特性实时监测系统,通过控制排气调节阀的开度展开喘振实验研究,在此基础上,设计和实现离心压缩机的主动控制喷射扩稳,通过小孔喷射高速气流实现喘振裕度的提升.研究表明:出口压力脉动幅度大大高于进口压力脉动,进气管道流动进入深度喘振的起始时刻要落后于排气管道进入深度喘振的起始时刻;机匣...     

Study on flow fields in high specific speed centrifugal compressor with unpinched vaneless diffuser

Performance of centrifugal compressors strongly depends on their internal flow fields. CFD has become indispensable tool for getting the information about flow fields in centrifugal compressors. CFD codes are usually validated by some representative data or compared with calculated results by other CFD codes, in order to ensure their accuracies. However, learning their accuracies for all types of centrifugal compressor’s specifications requires continuous works that compare experimental data obtained in developmental processes of various types of centrifugal compressors with CFD results. A prediction of a performance and a flow field of a centrifugal compressor by CFD is relatively accurate when the impact of separation and secondary flow on that flow field is weak, i.e. near design condition. Centrifugal compressors are deemed to have a wide operating range alongside high efficiencies at design points. Hence the prediction accuracy of CFD at off design conditions, where the impacts of separation and secondary flow on the flow field are strong, is critical for the design of the centrifugal compressors. This study therefore investigated the prediction accuracy of CFD using a centrifugal compressor whose geometry was intentionally changed to have a distorted flow field over a whole operating range, i.e. from choke to surge.     

周向槽机匣处理的数值研究及扩稳机理分析

结合周向槽机匣处理试验结果,采用全三维的数值方法对带周向槽机匣处理的亚音速轴流压气机内部流动进行研究。试验与数值结果均表明周向槽机匣处理能扩大压气机的稳定工作范围,同时略微地降低压气机效率。在两个转速下,数值模拟结果与试验结果符合良好。通过详细地分析压气机叶顶流场表明实体壁机匣时,触发该压气机失速的主要原因是间隙泄漏涡涡核破碎,使得叶顶通道堵塞程度严重。采取周向槽机匣处理能降低产生叶尖泄漏运动的驱动力,有效地削弱了间隙泄漏流造成的负面影响。与此同时,周向槽具有抽吸或吹除机匣端壁区低相对总压流体的能力,使低能气团在叶顶通道堆积的范围大为缩小,提高了叶顶通道内的流通能力。     

周向槽和阶梯槽在提高轴流压气机稳定工作裕度中的综合利用

在验证了计算模型的可靠性后,针对西北工业大学某轴流压气机转子的失速类型,进行了周向槽机匣、阶梯槽机匣,以及两者组合结构的扩稳效果的数值模拟.结果表明,周向槽结构在叶片通道前端可起到对叶顶泄漏涡的控制作用,而在叶片通道尾端效果不大.阶梯槽结构在叶片通道后端则能利用流向压差起到扩稳作用.采用叶片通道前部为周向槽,尾部为阶梯槽的组合机匣结构能在效率损失较小的情况下,对类似的压气机起到较理想的扩稳效果.     

Initial selection of groove location combination for multi-groove casing treatments

Stall margin improvement (SMI) curve is a function of a single groove location for a low-speed axial compressor and is investigated numerically and experimentally in this paper. SMI curve illustrates that good grooves are located in a fairly wide region approximately from 30% C_ax to 80% C_ax aft of the rotor leading edge. The narrow region that contains bad grooves is near 20% C_ax aft of the rotor leading edge. The initial selection of groove location combination for multi-groove casing treatments is proposed based on the SMI and efficiency improvement data generated by a series of single-groove and multi-groove casing treatments. The grooves should be set in the “wide region” of the SMI curve. The grooves located near the “narrow region” and the rotor trailing edge should be avoided. The “narrow region” can be identified by the axial momentum distribution of the tip leakage flow or the circumferentially averaged axial shear stress on the casing using the simulation results of the smooth casing at the near-stall point.

     

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。     

叶顶间隙形态对离心压缩机整级气动性能的影响

对某离心压缩机模型级6种不同的叶顶间隙形态的流场进行了数值模拟,分析了叶顶间隙形态对离心压缩机模型级整级气动性能的影响,详细分析了不同间隙形态内部的流动结构。研究结果表明:由于叶顶间隙的存在,在整个工况范围内级压比,多变效率,能量头相比无间隙时都有较大幅度下降,特别在大流量区下降更加明显,而且不同的间隙形态对级性能的影响也不同,与无间隙相比间隙1在设计工况点压比下降1.77%,多变效率下降0.65%,能量头下降3.08%,间隙4在设计工况点压比下降4.38%,多变效率下降2.41%,能量头下降7.08%,而间隙2,3,5,6的间隙值在间隙1和间隙4之间,其整级气动性能也介于间隙1和间隙4之间,其中间隙3和间隙5的整级气动性能要优于间隙2和间隙6。