Experimental study on flow and ignition-light-round characteristics of a triple-dome evaporative tube combustor

In this paper, three different evaporative tube configurations are presented, each of which is used to construct a triple-dome evaporative tube combustor. An optical test platform for these combustors is also built. Flow field experiments were conducted for each combustor configuration under varying pressure drops. Particle Image Velocimetry (PIV) was used to measure the cross-sections within the combustor flow field that significantly impact the ignition-light-round processes. The ignition-light-round boundaries for each configuration were determined separately under different pressure drops. Furthermore, high-speed imaging equipment was employed to record the dynamic development of the flame during these processes, providing further insight into the intrinsic relationship between the combustor flow and ignition-light-round performance. This also revealed the influence of the combustor pressure drop and evaporative tube structure on the flow field and ignition flame behavior. The experimental results indicate that the pressure drop in the combustor has a minimal effect on the overall flow field structure. However, an increase in airflow leads to greater turbulence within the combustor. Although the Fuel-to-Air Ratio (FAR) remains constant, this increase in turbulence significantly improves the mixing of fuel and gas, which in turn expands the ignition and light-round boundaries. The impact on ignition and flame time, however, is less pronounced. On the other hand, changes to the evaporative tube structure have a much more significant effect on the flow field. Specifically, increasing the outlet diameter causes the flow field near the head to form an expansion vortex, which enhances heat and mass transfer during the ignition process, thus accelerating ignition more effectively. Additionally, introducing small holes at the evaporative tube outlet reduces the axial flow velocity near the outlet and significantly increases the outlet airflow angle. This modification facilitates better flame propagation between the evaporative tubes, further accelerating the light-round process.