Investigation on the influence of nozzle configuration on performance of a 2-stage PDE

In order to investigate the influence of nozzle configuration on detonation initiation in a two-stage pulse detonation engine, detonation initiation processes using hydrogen-air mixture were simulated with different structural forms of nozzle including converging nozzle, converging-diverging nozzle, and diverging nozzle. A finite volume method with unstructured meshes refined moving self-adaptation and realizable k-ε turbulence model in software FLUENT were employed in the simulation. The non-equilibrium wall functions were used near wall and the PISO algorithm was employed in the calculation. Then the thrust and impulse performance of the two-stage pulse detonation engine with different structural forms of nozzle were calculated. Through comparative analysis of the thrust and impulse performance among the reflector, the nozzle, and the 2-stage PDE at different points during the detonation procedure the simulation results indicate that the thrust and impulse produced by the reflector is the major source of the total thrust and impulse produced by the 2-stage PDE, and the three nozzles have different influence on the two-stage pulse detonation engine. Take example for impulse, the converging nozzle is conducive to increasing the impulse of the reflector, but there is bigger negative nozzle impulse produced by itself at the same time, so the total impulse produced by the 2-stage PDE is smaller. And the convergent section of the converging-diverging nozzle is also in favor of smaller increase in the impulse of the reflector, but the negative nozzle impulse produced by itself at the same time offsets the positive nozzle impulse produced by the divergent section of the converging-diverging nozzle, as a result, the total impulse produced by the converging-diverging nozzle and the 2-stage PDE are both smaller. While the diverging nozzle hardly helps the increase in the reflector impulse, there is bigger positive nozzle impulse produced by itself, so the total impulse produced by the 2-stage PDE is bigger. With comprehensive consideration of various factors, the 2-stage PDE with the diverging nozzle is the best one. Therefore, compromise between reflector impulse and nozzle impulse is needed to select an appropriate nozzle configuration for this 2-stage PDE.