Numerical study on the influence of turbulence on the pyrolysis of hydrocarbon fuel in mini-channel

•A layer distribution of reaction rate with great gradient is formed near wall.•Relative rate of reaction rate and mixing presents multi-scale in radial direction.•Pyrolysis is controlled by mixing near wall but by chemical kinetics in core flow.•Increase in turbulent intensity enhances utilization of chemical absorption capacity. The turbulent heat convection with pyrolysis is very complicated and occurs in cooling system of hypersonic aircraft with hydrocarbon fuel as the coolant. Since the mixing controlled by turbulence directly affects the reaction and leads to variations in both conversion and selectivity, a 2D numerical model was established to study the influences of turbulence on the pyrolysis of hydrocarbon fuel in mini-channel. The numerical results indicated that the turbulence enhanced the heat and mass transfer in core flow. And turbulence became weak as closing to the wall, which leads to a layer distribution of reaction rate with great gradient forming near the wall. So the distribution of the reaction rate in core flow is more uniform compared with that near the wall. According to analyze the radial distribution of relative rate of that between reaction rate and mixing, the result showed that relative rate presented multi-scale in radial direction under the influence of turbulence. In addition, the increase in turbulent intensity was beneficial to the increase in uniformity of radial distribution of conversion, which was helpful to enhance the utilization level of chemical absorption capacity of fuel.