An experimental study on CH4/O2 continuously rotating detonation wave in a hollow combustion chamber

CH4/O-2 continuously rotating detonation waves (CRDWs) have been experimentally achieved in a special model with a hollow combustion chamber rather than a typical cylindrical annular chamber. Experiments were conducted at atmospheric backpressure and under various injection conditions (different mass flow rates of CH4/O-2 gaseous mixture). The injection conditions, together with the time domain and frequency domain characteristics of the high frequency pressure, have been analyzed. A high speed camera was employed to roughly record the reaction zone structure. Results show that for the given test mode working with lower mass flow rates - 38 g s(-1) CH4 and 131.7 g s(-1) O-2 (leading to an equivalence ratio of 1.154), CRDWs occurred but were not stably propagating. In contrast, stably propagated CRDWs were observed in a four-wave mode when mass flow rates were increased to 36.1 g s(-1) CH4 and 217.2 g s(-1) O-2 (leading to an equivalence ratio of 0.665). The corresponding average frequency and average velocity of the CRDWs were 19.251 kHz and 1512 m s(-1), respectively. FFT and STFT discussions on the high-frequency pressure history of CRDWs validated the stability of rotating detonation waves in the hollow chamber. This study further verified the feasibility of triggering the CRDW in a unique hollow combustion chamber through annular injection distribution. Injecting enough combustible mixture is the essential condition for sustaining a stable CRDW. (C) 2014 Elsevier Inc. All rights reserved.