Experiment of the effect of mixture filling rate on flame acceleration and DDT transition characteristics
To investigate the effect of fuel/oxidizer mixture filling rate on the flame acceleration and deflagration-to-detonation transition(DDT)in a pulse detonation engine,an experimental study was conducted with ethylene taken as fuel and oxygen-rich air of 40％oxygen volume fraction as the oxidizer.Fully developed detonation waves were successfully obtained using different combustion chamber configurations,different ignition positions,and different numbers of obstacles at the mixture filling speeds of 0,2.5,5.7,8.9 m/s,and 14.1 m/s.The results showed that the greater filling speed of the mixture indicated the faster flame development for the ability to detonate under working conditions.The deflagration to detonation transition time can be reduced to 38.9％of the filling speed of 0 m/s when the filling speed was 8.9 m/s.Meanwhile,the number of obstacles required for DDT can be reduced to 2 pairs from 3 pairs.Shortening the DDT section and the ignition section length but increasing the mixture fill rate still allowed to successfully organize the detonation,providing some guidance for optimizing the combustion chamber configuration of pulse detonation engines,and reducing the engine length and weight for improving propulsion performance.
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