Experimental and numerical investigation on oscillatory combustion characteristics of an integrated flameholder

Abstract

Integrated flameholders are widely used in advanced afterburner. Oscillatory combustion can be easily caused by the complex flow field and non-uniform fuel distribution in advanced afterburner with integrated flameholders. Therefore, the oscillatory combustion characteristics under uniform and non-uniform fuel distribution downstream of integrated flameholder is investigated by using an experimental method with numerical simulation. The results show that oscillatory combustion is more likely to occur under the condition of non-uniform fuel distribution. When oscillatory combustion occurs, the main frequency is approximately 33.99 Hz and the flame variations can be divided into three phases: re-ignition phase, instability pre-transmission phase and extinction phase. Furthermore, three combustion states are observed at equivalence ratio Φ varied between 0.2 and 0.85: steady combustion, quasi-periodic oscillatory combustion and limit-cycle oscillatory combustion. Limit-cycle oscillatory combustion exhibits a relatively simple proper orthogonal decomposition structure and a longer axial motion wavelength than quasi-periodic oscillatory combustion. Notably, during oscillatory combustion, the pressure and heat release rate pulsations are roughly in the same frequency and phase, which shows that the oscillatory combustion is mainly caused by thermoacoustic interaction. These results provide guidance for further investigations of oscillatory combustion in advanced afterburner with integrated flameholders and development measures for its suppression.