Investigation Of Flow And Heat Transfer Instability And Thermal Cracking Of Supercritical Pressure Hydrocarbon Fuel

As the core part of hypersonic vehicle,supersonic combustion ramjet is an important part of the aircraft design process.Based on the regenerative cooling technology of scramjet,this paper carried out experimental research on the instability and thermal cracking of supercritical hydrocarbon fuel.In this paper,the experimental study of vertical pipe is carried out for the instability of hydrocarbon fuel under supercritical pressure in the cross critical temperature region.There are two types of instability,namely the thermal acoustic oscillation caused by acoustic resonance and the helmholtz oscillation caused by density wave.With the increase of heat flux,the supercritical pressure flow experience after stability-shock state transitions,the law of the heat flux for turbulence has an important influence,when the closer it gets to the pseudocritical temperature fluid temperature at the outlet,the oscillation amplitude,the greater the cycle,the more obvious,the shock when the wall temperature and fluid temperature distribution relationship has great influence to the strength of the shock.Inlet temperature,in addition,working medium flow direction and velocity of working medium and the experimental pressure have obvious influence on the strength of the shock,and at the same time experiments draw the supercritical pressure distribution trend of hydrocarbon fuels stability domain.In this paper,the experimental study on the inhibitory instability of the supercritical pressure hydrocarbon fuel was carried out,and the influence of the steel spiral wire on the turbulence intensity was studied.The experimental results show that different lengths of spiral wires in different parts of the vertical pipe can significantly shorten the range of oscillation.The insertion of spiral wire in the whole pipeline can completely eliminate the occurrence of the system oscillation,while the local insertion of spiral wire will show different effects with the different insertion position.At the same time,the comprehensive heat transfer performance considering the flow resistance in different spiral wire conditions is calculated,and the results show that the integrated heat transfer performance of spiral wire is optimized in the whole tube.The pyrolysis experiment of high cracking rate in vertical pipeline is carried out for domestic new engineering fuel.The product of high temperature thermal cracking are mainly methane,ethane,ethylene and other gas phase product and olefins,aromatics and other liquid products,different product and has obvious linear relationship between cracking rate,pressure,flow factors for cracking rate has a significant impact.At the same time,the total package chemical reaction model suitable for the high cracking rate is fitted.