Study on convective heat transfer coefficient around a circular jet ejected into a supersonic flow

Abstract

The secondary jet injection into a supersonic cross flow can be observed in various situations such as a thrust vector control of a rocket and fuel injection of a scramjet engine, etc. The secondary jet in a supersonic flow acts as blocking body to the approaching cross flow although it is a fluid. When the blocking body exists in a supersonic flow, a complex structure of shock waves is produced. Many investigations have been conducted about the blocking bodies in a supersonic flow. Schuricht and Roberts[3] took surface temperature images using a TLC (Thermochromic Liquid Crystal) thermography to calculate the convective heat transfer coefficient. Yu[4] has measured the heat transfer coefficient around a protuberant cylinder body in supersonic flow by using a infra-red camera. There are some papers published about the pressure distribution around secondary injection hole in supersonic flow. Everett[5] has measured the pressure distribution around the circular secondary injection hole using PSP (Pressure Sensitive Paint), which show that the maximum pressure appeared on the side of injection hole. Huang[6] reported the crescent shape dimple around secondary injection hole which is installed at Titan IV SRM nozzle. Huang concluded that the high pressure and heat transfer cause the ablation around secondary injection. Although there are lots of studies on flow field and heat transfer about the cylindrical body and fin, there is little information about the heat transfer around a secondary jet. In this study, the convective heat transfer coefficient was measured around a circular secondary jet ejected into the supersonic flow field. The wall temperature measurement around the injection nozzle was conducted using an infra-red camera. A constant heat flux was applied to the wall around the secondary nozzle. For the different jet to freestream momentum ratio, the stagnation pressure of the secondary injection was controlled. The measured temperature is used to calculate the convective heat transfer coefficient. The comparison of the heat transfer coefficient distribution and the pressure distribution which is measured by Everett[5] was made in the center line.