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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,低速区靠近扩压器盖侧,高速区靠近扩压器盘侧;宽无叶扩压器的旋转失速与扩压器出口回流区有关,出口处回流区逐渐向扩压器内部发展,导致核心流发生畸变,最终导致旋转失速的发生。 相似文献
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无叶扩压器是离心压气机重要部件,也是涡轮增压器上应用最多的扩压器类型,详细研究其内部流场,掌握流动损失产生的机理,对于提升扩压器性能及抑制其失速的发生具有重要意义。本研究利用商用CFD软件NUMECA对离心压气机无叶扩压器进行了数值模拟,并对无叶扩压器收缩段和平行段内的流动分别进行分析,探讨了它们各自流动的特点,为进一步深入研究无叶扩压器流动,提升其性能奠定基础。 相似文献
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针对某型柴油机增压器压气机,基于整级全通道数值模拟和正交试验设计方法,研究了自循环机匣处理实现高亚声速压气机扩稳增效的潜力。结果表明:自循环机匣能够在提高设计点气动性能的前提下推迟失稳,但会牺牲堵塞流量。压气机的失稳和堵塞流量分别与叶片前缘及叶片扩压器中的堵塞程度相关。小流量侧自循环机匣通过抽吸叶轮叶顶附近低能流体,缓解堵塞,推迟失稳。但在大流量侧自循环机匣的喷射效应会增大扩压器进口攻角,加剧扩压器叶片流动分离,减小堵塞流量。抽吸效应与喷射效应强度均取决于抽吸槽的位置和宽度,压气机稳定性和堵塞流量与抽吸槽参数的变化基本呈负相关。自循环机匣对气动性能的影响包含两方面:在抽吸槽前,经回流槽流出的流体与主流的掺混及其产生的进口畸变将带来额外的效率和压比损失,适当减小回流槽角度可以降低该损失;在抽吸槽下游,得益于抽吸效应对叶顶流动状态的改善,压气机抽吸槽附近及下游高熵区减小,做功能力增强,气动损失大幅降低。在上述两方面共同影响下,压气机设计点气动性能最终得以提高。 相似文献
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将分析湍流拟序结构中的本征正交分解技术运用到离心压气机无叶扩压器的流动稳定性分析中,并将其与Galerkin投影法相结合建立了无叶扩压器内部流场的降阶模型。使用本征正交分解技术提取无叶扩压器在某来流入口角下非定常流场的主要流动模态,将流动控制方程通过Galerkin方法投影至由有限阶本征正交模态所组成的空间上,得到无叶扩压器流动稳定性降阶模型。计算结果表明:该模型可用于判断不同来流入口角下的扩压器流动稳定性,并将降阶模型的计算结果与流场数值模拟结果和线性稳定性预测结果进行对比,验证了此降阶方法的合理性。 相似文献
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为了研究离心压气机扩压器异常叶片对于失速现象的诱发效果,以带有叶扩压器的高速离心压气机为研究对象,通过整体或局部改变扩压器叶片安装角,开展非定常数值模拟研究并与实验结果对比验证,研究叶片安装角改变对离心压气机性能、动态特性以及失速机理的影响规律。研究表明:整体负方向旋转叶片安装角会促使扩压器更加不稳定,旋转角度从-5°到5°,最高效率点对应的质量流量逐渐增大。其中安装角偏转+5°扩压器叶片前缘靠近轮缘壁面发生流动分离,诱使无叶区间产生回流;而偏转-5°扩压器轮毂附近的流动分离主要发生在尾缘,造成扩压器叶片吸力面附近产生大范围回流。单个叶片安装角发生较大偏转(大于10°)时,扩压器比叶轮更早进入失速状态,且失速的机制可能会随着安装角偏移的增大发生改变。 相似文献
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Three vaned diffusers, designed to have high negative incidence (-8°) at the design operating point, are studied experimentally. The overall performance (efficiency and pressure ratio) are measured at three rotational speeds, and flow angles before and after the diffuser are measured at the design rotational speed and with three mass flow rates. The results are compared to corresponding results of the original vaneless diffuser design. Attention is paid to the performance at lower mass flows than the design mass flow. The results show that it is possible to improve the performance at mass flows lower than the design mass flow with a vaned diffuser designed with high negative incidence. However, with the vaned diffusers, the compressor still stalls at higher mass flow rates than with the vaneless one. The flow angle distributions after the diffuser are more uniform with the vaned diffusers. 相似文献
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This study focuses on the vaneless diffuser of a centrifugal compressor.The examined stage consists of an un-shrouded impeller,a parallel wall vaneless diffuser and a volute.The walls of the diffuser were movable allowingdifferent pinch configurations to be investigated.The baseline geometry had no pinch i.e.the height of the dif-fuser was equal to the height of the impeller flow channel plus the axial running clearance.The work consists ofboth numerical and experimental parts.Quasi-steady, turbulent,fully 3D numerical simulations were conducted.The inlet cone,rotor and diffuser were modelled.Six different configurations were studied.The height of thepinch was altered and the pinch made to different walls was tested.Two of the numerically studied cases werealso experimentally investigated.The overall performance of the compressor,the circumferential static and totalpressure and the spanwise total pressure distribution before and after the diffuser were measured.The numericaland experimental studies showed that the pinch improved the efficiency of the compressor. 相似文献
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Numerical analysis is conducted for the 3-dimensional impeller and vaneless diffuser of a small centrifugal com- pressor. The influence of impeller tip clearance on the flow field of the impeller is investigated. Detailed investigation on the leaking flow across the tip clearance of the impeller shows that the leaking flow rate is higher near the exit of the impeller than that near the inlet of the impeller. Based on this phenomenon, a new partially shrouded impeller is designed. The impeller is shrouded near the exit of the impeller. Numerical results show that the secondary flow region becomes smaller at the exit of the impeller. Better performance is achieved than that with the unshrouded impeller. 相似文献
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V. Moënne-Loccoz I. Trébinjac E. Benichou S. Goguey B. Paoletti P. Laucher 《热科学学报(英文版)》2017,26(4):289-296
The present paper gives the experimental results obtained in a centrifugal compressor stage designed and built by SAFRAN Helicopter Engines.The compressor is composed of inlet guide vanes,a backswept splittered unshrouded impeller,a splittered vaned radial diffuser and axial outlet guide vanes.Previous numerical simulations revealed a particular S-shape pressure rise characteristic at partial rotation speed and predicted an alternate flow pattern in the vaned radial diffuser at low mass flow rate.This alternate flow pattern involves two adjacent vane passages.One passage exhibits very low momentum and a low pressure recovery,whereas the adjacent passage has very high momentum in the passage inlet and diffuses efficiently.Experimental measurements confirm the S-shape of the pressure rise characteristic even if the stability limit experimentally occurs at higher mass flow than numerically predicted.At low mass flow the alternate stall pattern is confirmed thanks to the data obtained by high-frequency pressure sensors.As the compressor is throttled the path to instability has been registered and a first scenario of the surge inception is given.The compressor first experiences a steady alternate stall in the diffuser.As the mass flow decreases,the alternate stall amplifies and triggers the mild surge in the vaned diffuser.An unsteady behavior results from the interaction of the alternate stall and the mild surge.Finally,when the pressure gradient becomes too strong,the alternate stall blows away and the compressor enters into deep surge. 相似文献