Research On The Research Octane Number Of Alcohol Gasoline Substitute Mixture And Construction Of Knocking Combustion Mechanism

Knocking combustion is widely recognized as a major constraint on the performance of gasoline engines.Ethanol,with its high octane number and good anti-knock performance,can withstand higher compression ratios,enabling the engine to produce more power.Therefore,adding a certain percentage of ethanol to gasoline fuel to improve the anti-knock performance of fuel is an important way to suppress the knock of gasoline engines.Therefore,in-depth study of the physical and chemical properties of ethanol gasoline blended fuel is of great significance in suppressing gasoline engine knock and improving fuel economy.This paper firstly qualitatively and quantitatively explores the change of the octane number(RON)of the research method of ethanol-containing gasoline substitute mixtures by changing the content of ethanol in different gasoline substitute mixtures.It was found that the addition of ethanol played a significant role in increasing the RON value of PRF,TRF and TRF / DIB mixed fuels.In addition,the potential individual interactions between the individual components of ethanol were studied to gain a deeper understanding of the relevant mixing properties.It can be seen that for the RON value,there is a synergistic effect between n-heptane and ethanol,and an antagonistic effect exists between ethanol and toluene.Most notably,as the ethanol content increases,the change in the RON value of a mixture of ethanol and isooctane is more specific.When the volume fraction of ethanol is increased to 20%,the RON value of the mixture exceeds the RON value of pure ethanol until it reaches a peak at 40% ethanol content,and then the RON value decreases.Therefore,this indicates that there is both synergy and antagonism between ethanol and isooctane.Detailed information on the mixing characteristics of these fuels has not been found in many previous studies of ethanol-PRF fuels.This change in the RON value of the mixed fuel was not observed especially at lower ethanol content.Secondly,in this paper,two mathematical models for predicting RON values are constructed using the surface response method and BP neural network,which can greatly save the high experimental cost brought by the determination of gasoline octane number.After verification,both mathematical models have relatively good prediction accuracy.Finally,a chemical reaction kinetic model of a five-component gasoline substitute mixture suitable for knocking combustion is constructed in this paper.The first is the selection,modification and simplification of the ethanol mechanism.The experimental data under low temperature and high pressure conditions were used to verify the existing different ethanol mechanisms,so that the more suitable ethanol mechanism for detonation combustion was selected as the Mittal mechanism composed of 113 components and 710 element reactions.The simulation results of the mechanism in the high temperature region agree well with the experimental values,but there are large errors in the experimental results in the low temperature region.Then,the temperature sensitivity analysis was used to select the elementary reactions R16,R17 and R366 which have a large effect on low temperature ignition and a small effect on high temperature ignition.The result of the modified mechanism simulation is less different from the experimental value,which has a better prediction effect.The detailed ethanol mechanism was simplified into a simplified chemical kinetics mechanism consisting of34 components and 58 elementary reactions by reaction rate analysis.After verification,t was found that under different pressure conditions,the ignition delay time predicted by the simplified mechanism has the same trend as the experimental value,the relative error is small,and the agreement is good.Next,the simplified ethanol mechanism is coupled with the chemical kinetic model of the quaternary gasoline substitute mixture of isooctane,n-heptane,toluene,and diisobutylene,which has a wide range of temperature,pressure,and concentration.A chemical reaction kinetic model of a five-membered gasoline substitute mixture suitable for detonation combustion,consisting of isooctane,n-heptane,toluene,diisobutylene and ethanol,was constructed.The machine is composed of 120 components and 241 elementary reactions.Finally,through the comparison of simulation calculations and experimental data,it is found that the five-element mechanism in this paper can accurately describe the ignition characteristics of multivariate gasoline substitute mixtures.