Investigations On The Reciprocity Between Large-scale Structures And Combustion Of Supersonic Reacting Mixing Layer

Supersonic reacting mixing layer is the typical flow structure in Scramjet. Experimental and numerical investigations of the progress of reacting and non-reacting mixing layer are combined,which are focused on the factors that affect the large-scale structures.In order to know the basic flow structure of the supersonic planar mixing layer,NPLS and PIV experiments are launched to get the fine structure. Different from the turbulent development of supersonic p lanar mixing layer with thin thickness,the development of supersonic planar mixing layer with limited thickness is rapidly. The large-scale structures of mixing layer that possess the characters of quick movement and slow changes transmit to downriver at invariable speed. The transverse results show that the mixing layer is strip of right and d im and possess 3D characteristics. According to the PIV velocity fields,the movement of flow is the main movement of mixing layer. At the same time, the flow and transverse velocity fluctuate can explain the eddy movement perfectly because of their periodicity character. Results show that the higher the pressure of the high speed side,the thicker the mixing layer is. The development of mixing layer is restrained when the pressure of lower speed side is higher.To make up the weakness of experiment, numerical simulation was used to investigate the supersonic planar mixing layer that in the same condition of the experiment. In order to investigate the discipline of the development of large-scale eddy of non-reacting mixing layer,LES was used to simulate the effect of the clapboard thickness, the pressure-nonmatching extent,temperature and compress. Adopt the momentum thickness as the standard to estimate the mixing degree. The results suggest that: the momentum thickness goes higher with an increase of the clapboard thickness and the thicker the clapboard is,the faster and larger the eddy is. The non- matching pressure extent has an effect on the mixing,the trend is same as the experimental condition. The higher the pressure of the high speed side,the thicker the mixing layer is and the larger the eddy is. But the momentum thickness goes contract to the increasing temperature. In the structure of the paper,the momentum thickness and mixing increase and eddy-structure develop fast with the increasing of convective Mach number. The effect of the development of large-eddy can be thought as the function of pressure fluctuate and wave. To investigate the relationship between the twice,FFT was used to reconcile the numbers of pressure fluctuate. The results show that given a plot of frequency-power spectral density we can estimate the eddy scale passing the point during a period.To investigate of the factors that affect the development of large eddy of reacting mixing layer,the model of H2 and air was used. Based on the mixing efficiency,the trend of combustion and mixing in supersonic reacting mixing layer is consistent with non-reacting mixing layer. But of course,there are some differences. When the pressure of lower velocity side is higher,the mixing layer and combustion effect in the down river is higher than the matched condition. The trend of compress has non-linear to the mixing efficiency. Totally,the large-scale structure controls the mixing and combustion progress. With the heat release of chemical reacting and combustion,the rolling up ability of the vortex becomes weak and the compress is increase which lead the mixing layer thicker. Upon the results,mixing enhancement methods are needed. After using the cavity and staggered structure,the mixing efficiency is increasing apparently and the combustion effect is better.