Dynamic Characteristics of Ion Concentration Distribution for Combustion Instability With Different Injection Schemes

Abstract

The performance of aerospace vehicles directly depends on the operation of large combustion propulsion devices. Combustion instability has long been an inevitable and challenging problem in the development of large combustion propulsion devices. In this study, the dynamic characteristics of combustion instability under different injection schemes in a Helmholtz pulse combustor were investigated experimentally. The ion concentration signals at different locations in the combustor were acquired to characterize the dynamic process of unsteady combustion with different injection parameters. The flow field characteristics and reactant components distribution of the dual jet flame were simulated numerically. The results indicate that injection schemes with a large fuel injection angle ϕ and nozzle hole spacing are not conducive to combustion stability. A large fuel injection angle ϕ and nozzle-hole spacing L can prevent fuel jet convergence, thus dividing the central flame front into two parts: one is located near the nozzle outlet with fuel-rich combustion, and the other is close to the combustor wall with fuel-lean combustion. The fuel-rich state can more easily stimulate combustion instability than the fuel-lean state. Compared with the original converging jet, the newly established fuel-rich combustion region increases the occurrence of combustion instability. Nevertheless, the excessive fuel injection angle ϕ and nozzle-hole spacing L may result in the peak of the combustion heat release preceding the pressure oscillation, which is not conducive to combustion instability.