离心风机蜗壳流场的烟线法显示及基于变分原理的数值计算

离心风机蜗壳设计的优劣将直接影响风机的效率。本文介绍了用烟线法显示离心风机蜗壳内部流场的实验装置、实验方法和结果,并提供了两组实验照片。一组是在风机进口条件相同转速不同时拍摄的。另一组是在风机转速相同流量不同时拍摄的。对照片显示的蜗壳流场进行了分析。本文还介绍了基于变分原理的数值计算。根据泛函的极值必要条件,对离心风机蜗壳流道中的流场求解,并以变域变分的方法求解叶轮与蜗壳之间的分流流线的位置。最后将实验结果与计算结果进行了比较,两者相符。本文提供的方法可对蜗壳设计的优劣作出判断,并可对蜗壳进行优化设计。

FLOW VISUALIZATION IN SCROLL CENTRIFUGAL FAN USING SMOKE-WIRE METHOD AND NUMERICAL CALCULATION BASED ON THE VARIATIONAL PRINCIPLES

A centrifugal fan mainly consists of a suction section,an impeller and a scroll.Great attention has been paid to the study ofthe impeller,but little to the study of the scroll.In fact,in order toobtain a type of centrifugal fan with high efficiency,it is very impor-tant to understand the flow pattern in the scroll and to design a goodscroll matching a high efficiency blade.In persent paper,an experimental apparatus and method are usedto visualize the flow field in scroll of centrifugal fan using smoke-wiretechnique.Two experiments on flow visualization in the scroll havebeen done(1)at the different rotational speed but the same initialinlet conditions,(2)at the same rotational speed but the different dis-charges.Besides that,based on the variational principles with variabledomain established,the variational finite element calculating solutionsof 2-D inviscid flow field, especially of the branch streamline in aradial fan's scroll are given.In this paper,smoke flow visualizing photographs of internal flowof the scroll are analysed and compared with the results of the calcula-tion.It is found that the two results are in good agreement with eachother. With the conclusion,the well-or-ill internal fiow of the fansscroll can be wholly judged.And the methods given in this paper will leadto the attempt of optimizing the shape of fan's scroll.