The Effects of Wall Temperature on Flame Structure During Flame Quenching 940683

The effect of wall temperature on single surface flame quenching and flame structure of an atmospheric premixed methane-air flame was studied. The luminous region of a laminar flame was located at an angle of 45 degrees to a temperature- controlled surface. C₂ laser-induced fluorescence was used as an indicator of flame position while Raman spectroscopy was used to determine gas temperature profiles near the surface. These measurements were conducted for wall positions (vertical distance from the surface) ranging from 50 mm to 1.0 mm and wall temperatures ranging from 150 °C to 600 °C.

C₂ laser-induced fluorescence measurements indicated flame position is affected by the presence of a surface and the surface temperature. Larger C₂ fluorescence intensity values were observed for higher wall temperatures at all distances from the surface. At a position of 50 mm from the surface, the C₂ fluorescence intensity for a wall temperature of 600 °C was 2.5 times the C₂ fluorescence intensity for a wall temperature of 250 °C at the same location. A single surface flame quenching distance, based on C₂ fluorescence measurements, was determined. It was found to be a non-linear function of wall temperature. The flame quenching distance varied approximately linearly with wall temperatures ranging from 150 °C to 450 °C, but showed a non-linear variation for wall temperatures ranging from 450 °C to 600 °C.

Pulsed spontaneous Raman spectroscopy of nitrogen was used to measure the gas temperature profiles near the wall. These measurements showed that a wall temperature of 600 °C resulted in higher gas temperatures for wall positions less than 280 mm from the surface compared to gas temperatures at the same locations at a wall temperature of 250 °C. However, for distances far from the wall (> 350 μm), the gas temperature at sampled locations was approximately 100 °C lower for a wall temperature of 600 °C compared to a wall temperature of 250 °C.