Numerical investigations of different liner lengths of axial film cooling for a rotating detonation engine

Abstract

This study numerically investigates the axial slot film cooling of a stochiometric hydron/air rotating detonation engine. The essential flow characteristics are analyzed, and application prospects are explored. An annular liner is positioned at the inlet of the engine, partitioning the combustion chamber into a cooling passage and a combustion channel. Air is injected through the cooling channel to establish a protective low-temperature film along the outer wall. The thermal performance of three different liner lengths is evaluated, with all configurations achieving an average cooling effectiveness above 0.4 near the engine outlet. However, challenges arise from increased temperature due to deflagrations in the boundary layer and the disruption of cooling film by detonation products. Comparative evaluation of the three liner lengths indicates that a more extended liner enhances cooling effectiveness by mitigating the blocking effect. With the shortest and medium liners, the average cooling effectiveness decreases to 0.93 and 0.98, respectively, at 0.01 m upstream from the exit of the cooling channel. In contrast, the most extended liner maintains cooling effectiveness near unity. Despite a slight increase in instability of the longest liner, all configurations achieve a specific impulse exceeding 5800 s and a pressure gain over 0.25. The differences in propulsive performance among the liners are negligible, with the medium-length liner displaying a 0.30 % and 0.69 % higher average thrust compared to the shortest and longest liners, respectively. Based on these results, a liner exceeding the height of the detonation wave is finally recommended, offering a balance between propulsive performance and cooling effectiveness.