Long time operations of the valveless scheme to produce high frequency detonations without the purge process

High frequency operation is necessary in pulse detonation devices to improve the required performance. The valveless scheme is able to produce high frequency detonations and has a great advantage in reducing the hardware complexity. However, long time operation is a big challenge for this scheme when eliminating the purge process. Long time operations have been carried out in this study to verify the stability of such a scheme. The results indicate that long duration detonations can be produced employing an appropriately designed detonation tube although pre-ignitions still appear when the wall temperature exceeds the ignition point of the fuel and oxidizer mixture. Furthermore, damages of the spark plug and the projected spiral are observed after long time operations and, therefore, comprehensive cooling should be considered for long duration operations.