Numerical investigation of flame propagation in pulse detonation engine with variation of obstacle clearance

The objective of present research work is to investigate the combustion flame acceleration and performance of pulse detonation engine (PDE). The PDE tube consisting of obstacles of varying gap with fixed blockage ratio is analyzed in the current study. The three-dimensional reactive Navier–Stokes equation along with realizable k–ε turbulence model is used to simulate the combustion phenomena of hydrogen–air mixture. The one-step irreversible chemical kinetics model analyzes detailed mechanism of exothermic reaction. The propagation of flame and deflagration-to-detonation transition (DDT) run-up length is based on normal propagating regime. As the gap between combustor inner surface and obstacle outer diameter increases, the propagating area near the combustor axis reduces. Therefore, loss of momentum of turbulence combustion particle and unburnt fuel particles (voids) are increased at the wake of obstacle due to the increase in gap (or reduction in obstacle outer diameter), which results reduction in detonation wave velocity and detonation total pressure. However, DDT flame run-up length increases with lower temperature along the axis of PDE combustor. The thrust force generated by PDE combustor also gets reduced as the obstacle diameter is reduced.