单孔射流与主流相互作用时的流动和传热的实验研究

On Mechanism of Interaction between Mainstream and Jet around a Single Hole to Help Improve Film Cooling Effectiveness

在回流式传热风洞中，在速度比分别为０．３、１．０和２．０的条件下，对流向倾角分别为３０°、６０°和９０°的单孔气膜冷却射流与主流相互作用的速度和温度分布特征进行了详细的实验研究，并首次测量了锥形喷孔射流下游的温度和冷却效率的分布。总结出射流同主流相互作用下形成的速度边界层的等值线具有三种基本的分布形态，观察到纵向耦合涡的发展和变化趋势。孔形是决定气膜冷却效率的关键参数之一，锥顶角为３０°的锥形出口的喷孔较圆孔具有更宽的侧向覆盖区域，即使在高速比下其射流核心仍能较好地贴附在壁面上，因而具有较圆孔高得多的冷却效率。

This was a preliminary experimental study supported by RollsRoyce Inc., London, U.K. We found for the first time that shape of the hole was very influential on film cooling effectiveness. In Fig.1, we changed the end portion of the cylindrical hole to become a conical one that was bounded by OA and OB. The top curves in Figs.8(a) and 8(b) show the big increase in filmcooling effectiveness achievable with this change. To gain indepth understanding, we performed a number of experiments with streamwise angles of the jet hole taken as 30°, 60°, and 90° and with blowing ratios taken as 0.3, 1.0, and 2.0. Three basic forms of the longitudinal velocity contours in the boundary layer downstream of hole exit were found (Figs.2a through 2c). Fig.3 shows the vortex distributions we found and Fig.5 shows the contour lines of streamwise vorticity we found. For the first time, the profiles of temperature dowmstream of a conicalhole jet were measured. Compared with cylindricalhole jet, the lateral covered region of a conical jet (30° angle) became much wider so that the film cooling effectiveness was much greater than was the case with cylindrical hole.