Numerical investigation of pyrolysis coking characteristics of supercritical hydrocarbon fuels in sinusoidal cooling channels

Abstract

Carbon deposits in the high-temperature cooling channels of aero engines can lead to severe heat transfer deterioration. So it is significant to reduce the amount of carbon deposit and thus improve the safety of aero-engine operation. In this paper, a two-dimensional axisymmetric CFD model with coupled pyrolysis and coking reactions is developed, and the unsteady formation of carbon is directly simulated by the dynamic mesh technique. The pyrolysis, coking, flow and heat transfer characteristics of supercritical n-decane in smooth and sinusoidal channels during heated for 20 min were studied comparatively. The results show that the coking mass in the sinusoidal channel is basically maintained at 66% of the smooth channel, and the coking layer thickness was relatively declined by 20 μm, which is attributed to the lower precursor concentration and wall temperature in the sinusoidal channel. Specifically, due to a thinner boundary layer and a larger heat transfer area, the maximum difference in fuel conversion rate is 24.4%, with a maximum increase in Nu of 70 and a relative decrease in wall temperature of 85 K. Besides, the flow characteristics are mainly reflected in a significant increase in turbulence at the expense a pressure drop of 15.74 kPa.