Research On The Vibration Characteristics Of Plate And Its Influence On Supersonic Mixing

The paper is based on the research background of efficient mixing of fuel and air in the combustion chamber of Rocket-Based Combined Cycle(RBCC)engine.Nanoparticle-based Planar Laser Scattering(NPLS),Particle Image Velocimetry(PIV),laser vibrometer and Large Eddy Simulation(LES)are employed to investigate the vibration characteristics of cavity plate under different ratio of length to depth,and the influence of cavity plate on supersonic mixing layer is analyzed.The first six modes of cavity plate with varied configuration and the change rule of the modal frequency of each mode are obtained by modal analysis.The introduction of the cavity can change the natural frequency of the plate,and the first four natural frequencies of the plate with a length to depth of 13 are significantly improved.The vibration characteristics of plates under supersonic inflow are analyzed via experimental method.The results show that the vibration energy is concentrated on the first two orders of the natural frequency of the plate,and prove that the first two modes of the plate contribute most to the vibration type.In addition,the self-sustained oscillation of the cavity is investigated from two aspects: the fluid passing through the cavity and the feedback mechanism of the cavity.The basic flow field structure of 1mm flat plate,5mm flat plate and 5mm cavity plate are analyzed intuitively via NPLS.The flow field characteristics between the cavity plate and the flat plate as well as the cavities under different ratio of length to depth are compared.The time evolution characteristics of supersonic mixing layer flow field are analyzed by cross frame technique.The thickness of mixing layer and the growth rate of mixing layer are extracted via PIV experimental data.the growth rate of mixing layer increases obviously after the introduction of the cavity,but decreases with the increase of the ratio of length to depth of the cavity.In addition,on the basis of NPLS experiment,an experimental method of self-sustained oscillation of plate with NPLS is proposed,in which the influence of the position of the plate vibration on supersonic mixing layer flow field is investigated.It is discovered that the supersonic mixing layer flow field is more violent when the vibration position of the plate is relatively up.