Thermal response of a turbulent premixed flame to the imposed inlet oscillating velocity

Abstract

Thermal response is known as thermal behavior of an unstable combustor. Such investigation, which has not been found in the literature, is important in terms of safety and prevention of the structural failure. In this study, the thermal response of a combustor with an inlet excitation is numerically investigated. Due to the geometry shape, two recirculating zones are found. Any change in the amplitude and frequency can affect these recirculation zones. At low fixed frequencies (below 50 Hz) and with a change in the amplitude, these two recirculation zones have no important influence on the heat release. Thus, at the low frequencies, excitation amplitude has no considerable effect on flame transfer function. For both adiabatic and convective cases, at fixed frequency, when amplitude increases, mass flow rate from cold to hot gases increases and this makes a reduction in the maximum temperature. Further, at a contestant amplitude, with increasing the frequency, the maximum temperature reduces, with a higher reduction for convective case. The physical interpretation of observed changes is sought in the relation between hydrodynamic and thermal field, relative length of combustor respect to the acoustic wavelength and so on.