An Experimental Study on Flame Puffing of a Swirl Partially Premixed Combustion under Varying Mass Flow Rate of Primary Air

Abstract

It is of practical significance to understand the flame puffing behavior under varying mass flow rate of primary air ṁpri. An experiment was conducted to study the impact of ṁpri on flame puffing in a swirl partially premixed combustor, the puffing behavior of six significant flame properties was examined. The results showed that almost every spectrum had two fundamental frequencies, which is different from the single-peak spectrum of non-swirl flame. The flame heat-release rate, flame area, and flame equivalent width had identical dominant frequency and sub-dominant frequency, both decreased with the increasing of ṁpri. It was attributed to the decreased overall flame temperature caused by the improved mixing of fuel and primary air. All measured frequencies were in the range of 3–14 Hz, but the predicted frequencies from the theoretical models based on non-swirl flame were larger than the measured. This indicates the puffing frequency of swirl flame was much more sensitive to the variation in ṁpri than the frequency of non-swirl flame. Moreover, the amplitude of flame length was the smallest in all properties, with the most weakened oscillating intensity. While the amplitude of the flame area and flame equivalent width were the largest, with the strongest oscillation level. Consequently, the flame puffing is mainly attributed to the oscillation in width direction.

Keywords

• flame puffing
• swirl partially premixed flame
• puffing dynamics
• puffing frequency and amplitude
• effect of primary air mass flow rate