PIV Experiment Study Of Scramjet Internal Cold Flow Field

There are a lot of highly non-uniform, unsteady and complex three-dimensional flows in scramjet internal flow. Some scramjet internal flow experiments using PIV technology are conducted, in order to get a deep understanding about the physical essence of such flow phenomena and provide the experimental data for quantitative analysis about both instantaneous and time average flow, and the corresponding unsteady numerical simulations are conducted as well.This paper consists mainly of three parts. First, the advantages and necessity of PIV measurement techniques in the scramjet internal flow research are discussed after a brief description about the complex flow phenomena within the scramjet internal flow is given. And the research progress of hypersonic inlet/isolator and the supersonic combustor is summarized.Second, both PIV experiments and numerical simulations of hypersonic inlet/isolator internal flow under different working conditions with the typical isolator entrance flow are conducted. The result shows that both the location and shape of the shock train and the flow phenomenon within the isolator are unsteady and change with work condition. The flow phenomena are different in inlet/isolator under the certain and different backpressure; the unsteady non-uniform flow characteristics are obtained not only by experiment but also by numerical calculation. The phenomenon of the shock train's large scale unsteady oscillation in the flow direction within isolator is confirmed, the random and dramatic"shock wave switch"at higher backpressure is observed at the same time.Finally, a typical scramjet cavity combustor model based on the foregoing inlet/isolator mode is designed and an integrated model with the inlet/isolator model is formed. PIV and schlieren experiments and numerical simulations are conducted under the condition of actual supersonic combustor entrance flow. The results show that a serious unsteady fluctuation phenomenon of the shock train is presented within the combustor at higher backpressure coefficient which is believed to be caused by the unsteady flow from the isolator. The phenomenon related from the numerical simulation is validated by PIV and schlieren experiments, and it is shown that the distribution of the parameters on the combustor exit section is very non-uniform. Based on the above studies, the direction for the compatible design of the combustors and nozzles is pointed out, and some valuable data are provided.