跨音速风洞实验段中气流的加速问题

 在跨音速实验段的加速段的设计中存在这样的矛盾,即若要流场均匀则加速段长;若希望加速段短,则会加速过快而出现过膨胀现象。目前,实验研究不能给出可供设计用的一般规律。通过分析,本文试图找出其规律。1.加速段开闭比的分布规律 喷管的扩张段和跨音速实验段的加速段均可将音速气流加速到超音速,两种加速方法从结构上看不同,但膨胀加速的机理是相同的。

ON THE ACCELERATING AIRFLOW PROBLEM IN THE TEST SECTION OF A TRANSONIC WIND TUNNEL

The accelerating airflow problem in the transonic test section with perforated wall is investigated from three aspects.(1) The axial distribution of porosity;(2) The determination of design parameters in the front of accelerating section;(3) The investigation of the region of influence.Assuming that the axial pressure drop and the cross-flow velocity in a mass-flow nozzle is equal to those in the solid wall nozzle, a formula for calculating the open-area ratio of the mass-flow nozzle can be deduced. It is found that the predicted values of the o.pen-area are consistent with those measured ones. Hence, the formula can be utilized to design the open-area ratio distribution of the mass-flow nozzle.