Combustion instability of ethanol and n-heptane fuels under different combustor geometries

Abstract

Combustion instability has become one of the most significant challenges faced in designing modern industrial gas turbines and aero-engines. In this study, the influence of combustor structure on the combustion instability of ethanol and n-heptane is explored by adjusting the plenum length (200–550 mm) and the swirler vane angle (60° and 75°). The ethanol combustion instability maps show that the oscillation frequency increases as the equivalence ratio and plenum length decrease with the stabilization range of n-heptane being broader. The maximum pressure pulsation amplitudes of ethanol and n-heptane during combustion instabilities are close to 495 and 415 Pa, respectively. The flow field temperature measurements show that the fuel properties change the flame shape and temperature distribution in the combustor, thus potentially affecting the intensity of the oscillations. Short, compact ethanol flames and more uneven temperature distribution are more likely to lead to unstable combustion. This work provides more experimental observations on the effects of fuel properties and combustion configuration on combustion stability.