SUPPRESSION OF UNSTABLE FLOW IN CENTRIFUGAL BLOWERS BY THREE-DIMENSIONAL SEPARATION CONTROL

三维分离控制抑制离心风机不稳定流动

基本信息

批准号：
10650183
负责人：
ISHIDA Masahiro
金额：
$ 2.3万
依托单位：
NAGASAKI UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10650183/
关键词：
CENTRIFUGAL BLOWER UNSTABLE FLOW 3-D SEPARATION DIFFUSER STALL INDUCER STALL STALL MARGIN WALL ROUGHNESS CONTROL INLET RECIRCULATION 人工循環流形成

项目摘要

In most low specific speed type centrifugal impellers having backward leaning blade, the unstable flow such as rotating stall occurs in the vaneless diffuser and it is caused by the 3-D boundary layer separation mainly on the hub side wall not on the shroud side wall. On the other hand, in most high specific speed type open shrouded centrifugal impellers with radial blade, the unstable flow is caused by the flow separation in the inducer due to the excessive deceleration of relative velocity. The objective of this study is to suppress the unstable flow in each type of centrifugal blower without deteriorating blower characteristics.By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1%. This is based on the fact that the local reverse flow occurs firstly in the hub side in most centrifugal blowers with the backswept blade impeller. … More The 3-D boundary layer calculation shows that the increase in wall shear component normal to the main-flow direction decreases markedly the skewed angle of the 3-D boundary layer, and results in suppression of the 3-D separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R=1.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the 3-D boundary layer, supports the adverse pressure gradient.A ring groove arrangement was proposed to suppress unstable flow in a centrifugal blower with the radial blade impeller. The ring groove arrangement connects the impeller inlet upstream and the inducer throat tip, and forms an inlet recirculation through a bypass for the two regions. The inlet recirculation at small flow rates results in a decrease in the flow rate of unstab1e flow inception. An up to 8% improvement in surge margin was obtained by the ring groove arrangement at a small expense of the delivery pressure drop. A 3-D turbulent flow calculation was conducted to investigate effect s of the inlet recirculation on the main through-flow and unstable flow suppression in the impeller. The calculated results were compared with the experimental ones. It is found that the critical flow incidence is about 7.4 degrees for separation bubble formation at the blade leading edge, and the surge suppression is mainly due to decrease in flow incidence at the impeller leading based on the inlet recirculation flow. Less

在大多数具有后倾叶片的低比转速型离心叶轮中，无叶扩压器中会出现旋转失速等不稳定流动，这是由主要在轮毂侧壁上而不是在护罩侧壁上的3D边界层分离引起的。另一方面，在大多数具有径向叶片的高比转速型开式带冠离心叶轮中，由于相对速度的过度减速而导致诱导轮中的流动分离，从而导致流动不稳定。研究的目的是在不恶化鼓风机特性的情况下抑制每种类型的离心鼓风机中的不稳定流动。通过将完全粗糙的壁局部定位在无叶扩压器中的轮毂侧扩压器壁上，旋转失速开始时的流量减少了42%小于 1% 的小压降是基于以下事实：在大多数带有后掠叶片叶轮的离心式鼓风机中，局部逆流首先发生在轮毂侧。边界层计算表明，垂直于主流方向的壁面剪切分量的增加显着减小了3-D边界层的倾斜角，从而抑制了3-D分离。从理论上也阐明了扩散器。位于 R=1.2 下游的粗糙壁几乎不会损害压力恢复，因为 3-D 边界层斜角减小导致径向动量变化增加，支持逆压力梯度。环形槽布置提出了抑制带有径向叶片叶轮的离心式鼓风机中的不稳定流动，环槽布置连接叶轮上游入口和导流器喉部尖端，并通过旁路形成两个区域的入口再循环。通过环槽布置，以很小的输送压降 A 为代价，使不稳定流动开始时的流量降低了 8%。进行三维湍流计算，研究入口再循环对叶轮内主通流和不稳定流动抑制的影响，将计算结果与实验结果进行比较，发现临界流动发生率约为。叶片前缘处分离气泡形成的角度为7.4度，喘振抑制主要是由于入口再循环流的基础上叶轮前缘处的流动入射角减小。