Studies On Reaction Mechanism And Anharmonic Effect Correction Of Small Molecules/biofuels In Wide Range Temperature

In internal combustion engines, combustion infact is a process of chemical reaction.Rate constant, one of the most important parameters of chemical reaction kinetics, is an important scientific basis in combustion chemistry. As to the toxic substances, especially NOx and Halon, produced in the combustion, can not be ignored in the field of ship building and voyage transportation business. In addition, the anharmonic effect is growing more and more important on the unimolecular dissociations. Therefore, it is essential to study processes related to the kinetics of chemical reaction in combustion of fuel and do research on reaction mechanism of combustion processes involving in fuels,NOx and Halon for the purpose of improving the efficiency of internal combustion engine,reducing pollutant emissions and seeking more environment friendly alternative fuel.In this thesis firstly simulates three kinds of important biofuel, i.e. n-butanol, methyl butyrate and biodiesel, burning in the low-speed-two-stroke HCCI with different speeds,through which some important data within the reactor, such as the relationships between crank angle and these following data that temperature, pressure, mole fraction C, mole fraction CO, the mole fraction NO, the mole fraction NO2 and the mole fraction N2O can be obtained. And comparing with the pressure of the bench test for Diesel cycle, the results of the two cycles are similar. According to the pressure value of the bench test, the temperature of the Diesel cycle is compared with that of the HCCI simulated. The results are similar and the temperature is explained in the HCCI cycle by the reaction mechanism.In addition, those related reaction processes are analyzed. The research on related reaction mechanism contributes to analyzing the formation and transformation of NOx. This paper also simulates different amounts of methane and mixing n-butanol or methyl butyrate with methane in 50% of the case respectively, through which some important data within the reactor, such as the relationships between crank angle and these following data that the mole fraction NO, the mole fraction NO2 can be obtained. In addition, The effect of CH4 on the formation of NOx are analyzed. Due to the calculation of the first two chapters,it is found that there are some defects in the dynamics data used in simulation, according to the transition state theory (TST) and the Rice-Ramsperger-Kassel-Marcus (RRKM)theory, Yao-Lin (YL) method is applied to calculate the rate constants of the unimolecualr dissociations of biofuels including methyl butyrate (CH3CH2CH2C(=O)OCH3) and ethyl propionate (CH3CH2C(=O)OCH2CH3),by way of which the anharmonic effect of those two systems are discussed respectively. Besides, with least square method, this paper obtains the Arrhenius rate parameters of anharmonic and harmonic rate constants in canonical systems. In the last part of this paper, dynamic properties, including vibrational distribution, reaction cross section, rotational alignment and reaction rate constant of CH2Cl2 reacting with Ca in ground state and excitation state are calculated by means of quasi-classical trajectory (QCT) method.Conclusions are as follows: (1) For 6S70MC HCCI, speeds reduced from 85 r/min to 55 r/min, NOx emissions also decreased. (2) While burning within HCCI with 65 r/min,increasing the ratio of methane in biofuel molecure, with fixed amount, NOx emissions also decreased. (3) With temperature rising, rate constants of unimolecular dissociation involving in methyl butyrate and ethyl propionate increase respectively, while the growth rate of rate constant decreases gradually. (4) For the pyrolysis of methyl butyrate and ethyl propionate, the anharmonic effect on chemical reaction becomes obvious because of the isomerizing reaction due to chemical bond of C-H breaking. (5) While burning within internal combustion engine with speed of 85 rpm/min, the emission of NOx can be reduced by means of increasing the ratio of methane in the mixture between methane and biofuel molecures. (5) The rate constants of the reaction between CH2Cl2 and Ca in ground state are larger than those of the reaction between CH2Cl2 and Ca in excitation states.