轴流式风机三维设计中的损失模型与子午形状分析

ANALYSIS OF LOSS MODEL AND MERIDIONAL FORM IN THE THREE-DIMENSIONAL DESIGN OF AXIAL FLOW FANS

一、前言 本文在文献[1,2]基础上,提出了按二次对数曲线分布修正Howell损失模型,建立了级的效率与工作轮出口轮毂比等解析关系;按锥面叶栅最大许可的当量出口气流角确定工作轮进口轮毂比,从而为轴流式风机三维设计提供了最佳的通流部分子午形状。

When we study the three-dimensional design series of axial flow fans,the first problem that lies before us is how to determine precisely the loss model and the meridional form. In the aerodynamical design of axial flow turbocompressor, usually we have adopted Howell loss model. This model fully utilizes the experimental data of the plane cascades and provides us a useful, simple and accurate method of design. But Howell model doesn't cosider the actual effect of the three dimensional flow. In fact,in the Howell loss model,the losses of element stage cascade,including the profile loss, secondary loss and annulus loss, were distributed av-eragely to the arbitrary sections in the blade length. Apparently, it doesn't correspond to the real flow. In order to remedy the defect of Howell model, this paper puts forward a new loss model which considers the three dimensional flow effect and corrects the distributions of the secondary loss and annulus loss in the blade length. Based on the new model,this paper also has developed the new method which is used to determine optimum meridional form of impeller in accordance with optimum condition of d2 and βu. Experiments show that the theoretical analysis tallies with the test results.