A Study on Non-Steady Combustion : 1st Report, On the Fluctuation of the Entropy Mode

Abstract

In the flow field accompanying combustion, there exist three kinds of fluctuating modes such as pressure, entropy and vorticity types. Then, it can be regarded that the self driving sources of combustion oscillation originate from the mutual transforming rate and the mutual coupling processes among these three modes. However, if we restrict the oscillations to axial types only, the vorticity mode can be excluded. Among the former two modes, this report deals with the fluctuations which belong to the entropy mode. In the first place, experimental equations of steady heat release rate and temperature state are proposed. In the second place, expressions of non-steady state concentration, heat release rate and temperature are derived theoretically. As a separate subject, it was examined how and to what degree the decreasing process of entropy mode would be affected by frequency, heat conductivity, over-all heat transfer coefficient and flow velocity. The obtained results show that the temperature oscillations decrease slowly, which has been considered to be dissipated immediately behind the heat source.