科研之友
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摘要
A series of combustion tests was performed with a polymethylmethacrylate/gaseous oxygen combination to understand the effect of the interaction between preexisting shedding vortices and the additional vortices induced by disks displaced in the prechamber on the nonlinear combustion process. Experimental results showed a peculiar pressure drop of about 10 psi in a certain test condition. This pressure drop can be better understood by the DC shift reported in solid rocket combustion with opposite sign (pressure jumps up in the DC shift). Compressible study was conducted for the flow in a circular duct with a blowing wall to understand the dynamic role of shedding vortices. Large eddy simulation analysis illustrated many interesting flow features, including the existence of periodic oscillatory flow near the surface. The oscillatory flow characterized by the negative velocity is a direct consequence of shedding vortices, and this will lead to the local enhancement of heat flux. Thus, the plausible scenario for the negative DC shift is the phase cancellation of oscillatory flow motion preexisting in the surface region. If the disturbance generated in the prechamber is out of phase with that of the vortices produced by the blowing wall, it eventually leads to a sudden pressure drop.
