Influence of blowing ratio on double-wall cooling characteristics under the condition of high-temperature flue gas

Abstract

Double-wall cooling has been extensively investigated due to its exceptional cooling performance. However, most previous studies on the cooling characteristics of double-wall geometry have been conducted under non-reacting conditions, neglecting the influence of high-temperature flue gas radiation. In this paper, an experiment investigation was carried out to evaluate the impact of blowing ratio <italic>M</italic> and coolant-to-gas temperature ratio on the cooling characteristics of effusion/impingement cooling at reacting flow conditions. The experiments were performed at atmospheric pressure with flame temperatures of 1,800 and 1,900 K respectively. Flue gas temperature was measured by S-type thermocouples, while an infrared camera and N-type thermocouples were employed for the gas-side wall surface temperature distribution measurements. The results demonstrate that the laterally averaged cooling effectiveness of the effusion/impingement cooling system increases with the increase of <italic>M</italic>. However, beyond a blowing ratio of 5.1, further increments in <italic>M</italic> do not significantly affect the cooling effectiveness. Moreover, it is observed that the laterally averaged cooling effectiveness gradually improves along the flow direction but at a reduced rate. Additionally, no significant changes in cooling effectiveness are observed after <italic>X</italic>/<italic>D</italic> > 50. Furthermore, when considering a blowing ratio of 4, higher coolant temperatures result in higher cooling effectiveness compared to lower coolant temperatures.