Regulation Mechanism of Microribs on Heat Transfer Process of Cracking Reactive Flow With Strong Thermal Stratification

Abstract

Microrib is regarded as an efficient method to regulate the heat transfer and thermal cracking of hydrocarbon fuel in regenerative cooling channels of advanced aero-engines. In order to explore the regulation mechanism of microribs on heat transfer of endothermic hydrocarbon fuel with thermal cracking in the unilateral heated channels, a three-dimensional simulation model including a 22-step cracking mechanism was built and experimentally tested. Besides, a macroscopic approach based on time scale analysis is proposed to estimate effects of obstacles on turbulence and thermal cracking. The studies demonstrated that due to unilateral heating, the regulation of microribs on heat transfer and thermal cracking is nonuniform in the channel, relating to local turbulence intensity and fluid properties. Particularly, the thermal cracking of fuel responses more slowly than turbulence when meeting obstacles. In this case, the regulation of microribs on the heat transfer characteristics of cracking hydrocarbon fuel is dominated by the direct perturbation of microribs on flow momentum, not through promoting chemical absorption of thermal cracking by microribs. Furthermore, higher fuel conversion and higher fluid temperature both assist the promotion of microribs on thermal cracking to a limited extent but has little effect on the acceleration of microribs on local turbulent flow.