燃料温度对正癸烷裂解气扩散火焰推举影响研究OA

The combustion characteristics of jet fuel high-temperature pyrolysis products are directly related to the combustion efficiency and operational safety of scramjet engines.The flame lift-off phenomenon,as a key feature in diffusion combustion,significantly impacts combustion stability and pollutant emissions.As a typical surrogate component of jet fuel,n-decane is studied in this paper through experimental and theoretical analysis,focusing on the combustion characteristics of the thermal cracking products at temperatures ranging from 500℃to 850℃by coupling an electric heating flow tube reactor and a jet-in-hot-coflow burner.The non-reactive mixing process of single-component ethylene and two-component n-decane/ethylene was studied using numerical simulations.The calculation results show that,with increasing fuel temperature,the en-hanced pyrolysis reaction—rather than the rise in sensible enthalpy—governs the change in the local equiva-lence ratio distribution.The observation results of jet-in-hot-coflow flames indicate that as the fuel tempera-ture increases,the lift-off height of the flame monotonically decreases,and the corresponding delay time of the premixed combustion gradually shortens.Furthermore,the zero-dimensional ignition delay time calcu-lated based on the combustion reaction mechanism of n-decane and ethylene is much longer than the delay time of ignition after fuel-air contact in the experiment.Therefore,using stable species to replace the compo-sition of the high-temperature pyrolysis fuel may seriously underestimate it reactivity.This study provides ex-perimental support for clarifying the inherent mechanisms governing the coupled process of high-temperature fuel pyrolysis and combustion,and also offers a theoretical basis for the optimal design of engine combustors.