Flow field research in the side exit holes of an active cooling system with staggered jet array impingement

The compound internal cooling constructions based on impingement cooling were utilized broadly in the thermal protection of high temperature components. The air after impingement could enter other chambers as coolant supply through connected holes, which formed impingement jets, swirl flow or film cooling. Thus the understanding of flow characteristics and discharge coefficient distribution of these holes were important for the design of the internal coolant structures. An enlarged trapezoidal chamber with impingement jets, cross flow and film cooling was built up. Flow visualization was performed using a straight five-hole probe to gain the flow characteristics in the side exit holes, and the discharge coefficients of the side exit holes were also measured. Important results of the research include: The flow in the side exit holes were uneven. The air was constrained to windward wall and separation regions of low velocity flow were found in the outlet. Cross flow had significant influence on the flow structures and mass flow distribution of the side exit holes. The separation regions were enlarged and reverse flow emerged in the holes with the enhancing of cross flow, the discharge coeffecient and mass flow were decreased rapidly consequently. The impingement angle had little effect on the flow characteristics of the holes when there was no cross flow in the passage. Larger impingement angle tended to increase the flow loss and enhance reverse flow in the holes once cross flow was formed in the passage. The flow of film cooling holes has no evident influences on the flow structures and discharge coefficients of the side exit holes.