碳氢燃料在波纹管内的超临界裂解传热特性

Supercritical Heat Transfer Characteristics of Hydrocarbon Fuel with Pyrolysis in Corrugated Tubes

为了探究波纹型冷却通道在碳氢燃料发动机再生冷却系统中的适用性,基于一步总包反应机理,建立了同时考虑碳氢燃料流动传热、裂解吸热与固体导热的耦合算法,在此基础上对超临界压力下正癸烷在波纹管内的流动传热和裂解吸热现象展开数值研究。通过与光滑管进行对比,分析了波纹结构对管内热量传递、组分输运和裂解反应吸热的影响,进一步研究了不同壁面热流下的裂解传热特性。研究表明:波纹管可以显著提升燃料的换热能力,平均对流换热系数最高可提升40%;波纹管内的速度波动使流场内温度和组分浓度在径向的分布更加均匀,同时降低了正癸烷的裂解吸热率和平均裂解转化率;壁面热流在0.8MW/m2～1.0MW/m2变化时,正癸烷裂解吸热率和综合换热性能随热流的增加而增加。

In order to investigate the feasibility of corrugated cooling channel for regenerative cooling system of hydrocarbon-fueled engine,a numerical method considering convective heat transfer,endothermic pyrolytic reaction,and heat conduction in solid region simultaneously was developed based on a one-step thermal cracking mechanism.Based on this,a numerical investigation on turbulent heat transfer of n-decane flowing inside corrugated tubes with endothermic pyrolysis at supercritical pressure was conducted.The effects of corrugated tube structures on heat transfer,species transport and endothermic pyrolysis were analyzed through comparison with smooth tube.Moreover,the influence of wall heat fluxes was further studied.Results reveal that corrugated tubes can significantly improve the heat transfer ability,and the averaged convective heat transfer coefficient increase by up to 40%.The velocity fluctuations induced by corrugation lead to more uniform distribution of temperature and species concentration in radial direction.It can also reduce the pyrolytic heat-absorbing rate and averaged fuel conversion.With the increasing wall heat fluxes ranging from 0.8 MW/m2 to 1.0 MW/m2,the overall thermal performance and pyrolytic heat-absorbing rate are improved.