Studies on the valveless scheme to produce high-frequency detonations with different purge methods |
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| Institution: | 1. Shaanxi Key Laboratory of Thermal Sciences in Aeroengine System, Northwestern Polytechnical University, Xi''an 710129, P R China;2. School of Power and Energy, Northwestern Polytechnical University, Xi''an 710129, P R China;1. Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, China;2. SKLTCS, CAPT, BIC-ESAT, College of Engineering, Peking University, Beijing 100871, China;1. School of Aerospace Engineering, Georgia Institute of Technology, 270 Ferst Dr, Atlanta, GA 30332, United States;2. GE Research, 1 Research Cir, Niskayuna, NY 12309, United States;1. Department of Mechanical Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, ON, K1N6N5, Canada;2. Department of Chemistry and Chemical Engineering, Royal Military College of Canada, 11 Crerar Cres., Kingston, ON K7K7B4, Canada;1. Department of Mechanical Engineering, University of Ottawa, Ottawa, ON K1N6N5, Canada;2. now at the National Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing 210094, China;1. Department of Mechanical, Industrial and Aerospace Engineering, Concordia University, Montreal, Quebec, H3G 1M8, Canada;2. Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven, 5600 MB, the Netherlands;3. Eindhoven Institute of Renewable Energy Systems, Eindhoven University of Technology, Eindhoven, 5600 MB, the Netherlands |
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| Abstract: | Producing high-frequency detonations is an important topic for pulse detonations which has received considerable attentions. The valveless scheme has been verified to be able to obtain high-frequency detonations more than 100 Hz. This work has been conducted to investigate the possibility to achieve a higher detonation frequency and clarify the limits of stable operations preliminarily for the valveless scheme with different purge methods. Oxygen, ethylene, and nitrogen or liquid water are utilized as oxidizer, fuel, and purge medium in the experiments while two injection configurations are employed. The maximum detonation frequencies of 180 Hz and 330 Hz have been achieved in stable operations for two different injection configurations when nitrogen is used as the purge gas. The ceiling frequency for stable detonations is 300 Hz if nitrogen is replaced by liquid water, which indicates that water vapor is capable to create an efficient buffer zone to ensure stable operations. The results imply that the injection configuration also has a great impact on the ceiling stable detonation frequency. Three operating modes have been observed in this study, i.e., a stable detonation mode, an unstable detonation mode, and a deflagration mode. In the unstable mode, failure of detonation initiation occurs frequently and one interesting phenomenon is that the detonation frequency is reduced by half exactly when insufficient filling happens. The supply pressure ratios of oxidizer to fuel and purge to fuel are obtained for different operating modes when the purge method is changed. Furthermore, the equivalence ratios have been also studied for different operating modes which reveals that the range will change when different purge methods and injection configurations are employed. According to the equivalence ratio and the mass flow rates, an equivalent volume fraction of oxygen is defined and its range for the stable detonation mode is clarified. |
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