Aerodynamic and thermal structures of the laminarboundary layer over a flat plate with a diffusion flame

The influence of the flame reaction on the aerodynamic and thermal structures of the laminar, two-dimensional boundary layer over a flat plate has been studied experimentally. The diffusion flame was produced by injecting fuel gas (methane or propane) from a porous plate surface into a uniform air stream flowing along the plate. The results show that acceleration of the gas stream is observed, even at the station closeto the leading flame edge located just above the edge of the porous plate. The temperature in the blue-flame zone is found to increase with the distance from this leading edge. Changes in the velocity and temperature profiles are also observed in the boundary layer upstream of the leading flame edge. The pressure distribution has been calculated using the measured velocity and temperatureprofiles. The pressure distortion on the air-stream side of the flame zone can be atributed to the rapid increase in the thickness of the laminar boundary layer with a diffusion flame. The velocity overshoot near the flame zone may be caused by this pressure distortion. It is shown that the aerodynamic structure of the boundary layer changes considerably in the presence of a diffusion flame, and that even in the laminar boundary layer over a flat plate, the pressure cannot be considered to be uniform if a diffusion flame is established in it.