Heat balance evaluation of double-base solid propellant combustion using thermography and laser heating on a burning surface

A new method is proposed using laser heating and thermography for estimating the heat transfer balance for burning solid propellant: heat production rate on burning surface Q˙s, heat flux from burning surface to solid phase Λp, and heat flux rate from flame to burning surface Hf. Hf is determined from the correlation between burning rate and power density of laser heating on burning surface; Λp is evaluated using the burning surface temperature measured with thermography. Double-base propellant is tested in a combustion chamber having a laser-introducing window, and is irradiated with an 808-nm laser at laser power densities ranging from 0.3 to 0.8 W/mm2 with a back-pressure range from 0.02 to 0.60 MPa. The proposed method shows heat flux from burning surface to burning surface Hf of 1.7 W/mm2, heat production rate on burning surface Q˙s of 4.9 W/mm2, and heat flux from burning surface to solid phase Λp of 6.6 W/mm2 at a back pressure of 0.60 MPa. Laser power attenuation due to the flame is determined to evaluate the influence of laser power attenuation on the estimation of heat flux rate from flame to burning surface. The experiment shows that errors originating from laser power attenuation due to the flame are below 18%.