It is very important to know the heat flux to a wall in order to understand the unsteady heat transfer in the combustion chamber. In this study, a fuel-air mixture was ignited at the center of a ...constant-volume vessel and the heat flux was determined from change of the temperature distribution in the boundary layer near the wall of the end gas side by analysing the interference image. The value of the heat flux was compared to that from a thin surface coaxial thermocouple with high response. It was found that before the flame arrives at the wall, the heat transfer is smaller than the thermal radiation from the flame, and the temperature of unburned gas changes nearly adiabatically. After the flame reaches the wall, the heat flux due to the temperature gradient becomes larger than that from the thermal radiation.
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