Research On Combustion Mechanism Of Gasoline Surrogate Fuel And Measurement Of Laminar Flame Speed

The development of chemical kinetic model for multi-component gasoline surrogate fuels with high versatility,good applicability and small scales of mechanisms,is crucial to numerical simulation researches on combustion process and pollution generation.In this paper,by means of experimental measurement,numerical simulation and theory analysis,the chemical mechanism and laminar flame characteristics of gasoline surrogate fuels have been studied.Firstly,the experimental systems of constant volume combustion bomb for measuring laminar flame speed have been designed and built.The designed premixed gas initial pressure is as high as 3MPa,while the initial temperature is as high as 530 K.The experimental systems have advantages of high reliability and good stability.Moreover,the range of equivalence ratios has been extended from 0.6 to 1.5.Secondly,using constant volume combustion bomb experiment,under the initial conditions of pressure 0.1 MPa and 0.3MPa,temperature 400 K and 450 K,equivalence ratios 0.6-1.5,the laminar flame speeds and Markstein lengths of five C7-C8 gasoline representative components have been measured.Most of the experimental data have not been measured in current literatures.Moreover,the laminar flame speeds and flame stability of different hydrocarbon fuels with same carbon number have been studied.Thirdly,A chemical kinetic model for ignition and oxidation of gasoline surrogate fuels composed of n-heptane,iso-octane,toluene,ethanol and diisobutylene has been developed.The mechanism consists of 89 species and 355 elementary reactions,which is much smaller than the current models.The sufficient validated results show that the present mechanism has a wider applicability,versatility and rationality.Fourthly,based on the mechanism of gasoline surrogate fuels,a chemical mechanism for polycyclic aromatic hydrocarbon formation of the gasoline surrogate fuels.This kinetic model consists 107 species and 418 elementary reactions.The kinetic model has small scales,is suitable for gasoline and sufficiently validated.Then,using the present kinetic model coupled with detailed soot computing method,the characteristics of soot formation in premixed flame for the five gasoline representative components have been studied.The results show that aromatic hydrocarbon can easily generate soot,while ethonal cannot.And alkene can generate soot more easily than alkane.Moreover,the paths of soot formation for five components have been presented,which can explain the above results well.Finally,adopting the present kinetic model,the combustion characteristics for several gasoline surrogate fuel models have been studied.The analysis shows that OH radical is critical to ignition process.With high initial temperature,the ignition times of different surrogate models present similarity,while with low initial temperature it shows difference.H radical has important influence on burning velocity,and determines the laminar flame speeds of the surrogate models.The value of toluene and diisobutylene mole fraction determines the amount of PAHs and soot emissions.