Research On Mixture Ratio Measurement Of Kerosene Alternative Fuel Using PLIF Technology

Kerosene is one of the commonly used fuels for aerospace engines,which as a liquid hydrocarbon fuel,needs to be injected,atomized,vaporized,mixed,ignited and burned during engine operation.The mixing process is very important,and the partial equivalence ratio of kerosene/air(oxygen)determines whether the engine can successfully ignite and burn efficiently.Therefore,it is necessary to be able to measure time-space local equivalence ratio of the air/kerosene mixture in the combustor in order to provide basic data for the design of new injection technology and provide measurement methods for performance evaluation of new injection technology.This paper will use optical diagnostic technology—Plane Laser Induced Fluorescence(PLIF)technology to quantitatively measure the distribution characteristics of equivalence ratio in the premixed flow field.The fluorescent substances in kerosene are mainly 1,2,4-trimethylbenzene,naphthalene,1-methylnaphthalene,1,3-dimethylnaphthalene.By comparing the physical and chemical properties of these four substances,Since the fluorescence of 1,3-dimethylnaphthalene is insensitive to temperature which meets the tracer requirements of this experiment,1,3-dimethylnaphthalene was selected as a tracer.Compared with the physical and chemical properties of common alkane and domestic kerosene,n-undecane was selected as an alternative fuel for kerosene.According to the PLIF fluorescence expression of kerosene,the factors affecting the fluorescence intensity of kerosene are analyzed,the expression of fluorescence intensity is simplified,and an experimental scheme for quantitatively measuring the distribution equivalence ratio of air/kerosene mixture is proposed.In addition,according to the experimental scheme,using the kerosene evaporation premixing system,a quantitative ratio of the alternative fuel equivalence ratio is achieved.Kerosene fluorescence signal intensity calibration experiments are the basis for quantitative measurement of the alternative fuel equivalence ratio.The fluorescence lifetime of 1,3-dimethylnaphthalene was measured to be 6.8ns.Through the experiment,the influence of ambient gas,temperature and mixing ratio on the fluorescence signal of 1,3-dimethylnaphthalene was obtained,and the functions between the fluorescence intensity and temperature and the equivalence ratio was obtained.Experiment on quantitative measurement of gas flow equivalence ratio distribution characteristics of heated premixed injection fields at atmospheric pressure was conducted.The spray fields were measured quantitatively at different temperatures,different equivalence ratios and different flow velocities.The PLIF images were inverted based on the fluorescence signal calibration experiment results,and the distribution equivalence ratio image of the spray field was obtained.With the increase of gas flow velocity,the spray field gradually changes from laminar flow to turbulent flow,and the distribution equivalence ratio of spray field becomes more complicated.The experimental results were obtained that repeated average measurement accuracy is 7.63%,single measurement accuracy is better than 14.45%.