Study on the start-up coupling and interaction characteristics of parallel pulse combustors based on flame visualization

• Study explores pressure signals, flame dynamics, and coupling mechanisms in parallel pulsating combustors across operational phases. • Unstable to stable pulsating combustion transition: Pressure and flame synchronize at 79.0 Hz. • Findings guide parallel pulsating combustor design, boosting efficiency and stability. Pulse combustion technology, recognized for its high efficiency and low emissions, has attracted considerable attention in the aerospace, aviation, and energy sectors. To resolve the conflict between increasing thermal power and maintaining structural integrity in single pulse combustors, this study proposes a parallel pulse combustor structure. The paper systematically explores the pressure signal characteristics, flame dynamics, and their coupling mechanisms during the startup excitation, transition, and stable pulse combustion phases, and investigates the dynamic formation of coupled flames. The results indicate that during startup, pressure amplitudes remain low with independent frequencies, while flame evolution exhibits non-periodic behavior. Incomplete combustion produces orange flames accompanied by frequent yet irregular coupling events. In the transition phase, the pressure signals become periodic, with increased amplitude and stronger coupling between the two chambers. Flame excitation becomes concentrated during the negative pressure phase, combustion efficiency improves, and a cooperative coupling mechanism emerges. In the stable pulse combustion phase, despite timing differences in valve opening events, the opening durations and flow-reversal points achieve synchronization. Coupled flames driven by pressure differences occur at both positive and negative pressure phases, and frequency synchronization between chambers (stabilized at 79.0 Hz) proves critical for maintaining coupling stability. This study provides essential theoretical support for the design and optimization of parallel pulse combustors.