长圆形出口喷嘴射流特性的实验研究

EXPERIMENTAL STUDY ON JET FEATURES OF THE NOZZLE WITH ELLIPTICAL EXIT

在研究矩形出口喷嘴射流的基础上,对长圆形出口喷嘴的射流特性进行了室内实验研究.结果表明.长圆形喷嘴射流在短轴剖面上的扩散角比在长轴剖面上大.随喷距的增大.其横向截面将逐渐变为圆形.长圆形喷嘴的流量系数大于同样结构特征的矩形喷嘴,其射流的轴心动压力衰减以及横向动压力梯度分布规律与矩形喷嘴射流相似.随喷距增加.长圆形喷嘴的轴心动压力衰减比矩形喷嘴衰减慢.在钻头上使用的长圆形喷嘴的最佳无因次喷距应在无因次等速核长度L_1和最大轴心动压力衰减梯度所在的无因次喷距L_(max)之间.

Anexperimental study on jet features of the nozzle with elliptical exit was made in laboratory. The results show that there was a larger spread angle in the short-axis section than in the long-axis section for the jet. With increase of jet distance, the cross-section of the jet changed into a circle gradually. The nozzle had a larger discharge coefficient than rectangular nozzle with the same structures of flow channel as the elliptical nozzle. The jet of the nozzle with elliptical exit was similar to the rectangular nozzle jet in centerline dynamic pressure attenuation in the axial direction, and distributions of dynamic pressure and dynamic pressure gradient in the cross-section. As jet distance increased, the centerline dynamic pressure of the jet attenuated is less than rectangular nozzle. The better effects of cleaning and cooling will be achieved by replacing rectangular nozzles with the elliptical nozzles on rock bit in improving bit hydraulics. The recommended reasonable dismensionless jet distance of the nozzle on rock bit was between dismensionless length (L1) of potential core and dismensionless jet distance Lmax, where the gradient of centerline dynamic pressure attenuation was the largest.