三维收缩段设计问题

结合西北工业大学低速风洞的设计研究了矩形截面三维收缩段设计问题。用差分方法和贴体坐标对收缩段的不可压势流场进行了数值计算。选择三种常用的收缩曲线进行比较设计,对设计准则进行了校核,并给出收缩殴流动特性。通过优化的双三次曲线优于其他曲线。最后对三维收缩段设计问题提出一些看法。

DESIGN PROBLEMS OF THREE-DIMENSIONAL CONTRACTIONS

The numerical analysis of the incompressible flow in rectangular contractions is performed, by using a finite-difference method and body-fitted coordinates. Three types of commonly used wall contours are chosen and compared, i.e. contour with Witozinsky curve, 5th power curve and match cubic curves respectively. Two design criteria have been generally used for axisymmetric contractions, i.e., (1) no separation on nozzle walls, (2) non uniformity at exit cross section lower than 2%. These criteria are revised and applied to three-dimensional contractions to compare the performance of the above mentioned three types of contours. It is found that the contour with matched cubic curves, when optimized, gives the most satisfactory results, while the contour with Witozinsky curue gives the worst results because of serious adverse pressure gradient near the entrance. Some problems of three -dimensional contraction design are also discussed. The cross section similarity is usually considered as a requirement in three- dimensional contraction design practice. The author's numerical investigation shows, however, that this requirement is of no real value.