Dependence Of PDE Performance On Nozzle-shape And Fuel-filling Rate

A grid adaptive finite volume method combined with kinetic chemical reaction model was developed to simulate the flow field of detonation wave propagating through a divergent channel. The investigation was focused on the performance of pulse detonation engine depending on the nozzle shape and the partial-fuel fill in the chamber. It was found that the impulse of the straight detonation tube with a hydrogen-air mixture achieves its maximum at a certain filling rate. On the other hand, as to the nozzles with a larger divergent angle, the impulse increases with increase fuel filling rate, although in most case the specific impulse increases with decreasing fuel-filling rate. The specific impulse can be obviously improved with properly designed nozzle shape and fuel filling rate. The main conclusions are summarized as follows:(1) When the detonation wave in hydrogen-air mixture encounters the interface of combustible mixture-air in straight tube, a reflected shock will be generated, which causes pressure increase on the thrust wall. As a result, the impulse of the straight detonation tube achieves its maximum at a certain filling rate, which differs from the case of ethylene-oxygen mixture as fuel, whose impulse increases with the increase in fuel filling rate. On the other hand, the specific impulse increases with the decrease in fuel filling rate.(2) 15° and 45° nozzles were chosen as representations of no-straight channels to simulate the flow fields under three nozzle-filling conditions, namely full-filled, half-filled and none-filled. It was found that the impulse provided by the end wall of tubes are dominant for 15° nozzle, so it's performance is similar to the case of 0° nozzles. However, the impulse of 45° nozzle is mainly provided by the nozzle. The variations of the filling conditions in the nozzle cause little change in the fraction of the impulse provided with thrust wall.(3) 45° nozzles overwhelm 15° ones in the impulse and the specific impulse under all filling conditions, which means the area on which pressure can act is one of the key factors of pulse detonation engine efficiency.