Influence Of Coke Formation From Aviation Kerosene During Steam Reforming Reaction On Flow And Heat Transfer In The Microchannel

The traditional engine cooling method is no longer applicable with the high speed aircraft,then regenerative cooling technology has been favored by researchers because of its many advantages.However,when the hydrocarbon fuel is subjected to endothermic cracking reaction in the cooling channel,it often deposits and cokes on the inner wall of the channel,which not only affects the cooling effect but also causes other hazards.Therefore,this paper takes aviation kerosene RP-3 as the research object,uses commercial CFD software and combined with chemical reaction kinetics models to study the influence of coke formation from aviation kerosene during steam catalytic reforming reaction on flow and heat transfer in the microchannel.The steam catalytic reforming process of aviation kerosene RP-3 in the microchannel was simulated by using a two-dimensional grid model.The change of temperature distribution,velocity distribution,fuel conversion rate and the yield of products in the microchannel were analyzed.The results show that the temperature decrease degree decreases,the fluid velocity slows down,the fuel conversion rate decreases,the carbon deposition production increases at first and then remains stable,the CH₄,H₂ and CO production decreases and the C₂H₄,C₂H₆ and C₃H₆ production increases with the increase of the thickness of carbon deposits.A modified model was used to simulate the steam catalytic reforming reaction process in microchannel with thermal resistance.The results show that the chemical heat absorption of the model with a carbon layer increases rapidly at first and then decreases rapidly after the carbon layer appears.With different models of carbon deposition layer thickness,the value of considering thermal resistance model should be less than without considering thermal resistance model with the data of speed,temperature,fuel conversion rate,carbon deposition and product yield,and the difference of the two values are decreased with the increase of the thickness of carbon deposits.Meanwhile,the model considering thermal resistance in the front section of the channel has a larger temperature gradient in the radial direction than the model without thermal resistance.The steam catalytic reforming reaction of aviation kerosene RP-3 in microchannel was simulated with different water content and different inlet flow rates.The results show that fuel conversion rate and carbon deposition decreases,temperature decrease degree decreases,fluid velocity increases and the yield of CH₄,H₂,CO,C₂H₄,C₂H₆ and C₃H₆production decreases with the increase of inlet flow rate.The increase of initial water content can increase the fuel conversion rate,decrease the amount of carbon deposition,decrease the degree of temperature,increase the fluid velocity,increase the amount of CH₄,H₂ and CO,and decrease the amount of C₂H₄,C₂H₆ and C₃H₆.Surface roughness was introduced to study the steam catalytic reforming reaction process in the microchannel with different relative roughness and different rough element spacing.The results show that the heat transfer effect is firstly enhanced and then deteriorated,and the high speed zone in the middle part is gradually extended downward with the increase of the relative roughness.A swirling flow appears in the lower part,and with the relative roughness increases,the range of influence of the swirling flow also increases.With the increase of rough element spacing,the upper fluid temperature distribution occurs fluctuates,then the region temperature distribution between the two rough elements is high on the sides and low in the middle,it also tends to the right wall.The high-speed area gradually expands downward,the swirl appears in the lower area then it is gradually shifted to the left wall with the pressure of the incoming flow from the upper area.The swirl is constantly strengthen and its influence range is expanded,which is conducive to the heat transfer between the fluid and the wall in the local area.