Research On The Multi-step Chemical Reaction Mechanism Of Typical Fuel

In order to predict the ignition and combustion performance of RP-3 aviation kerosene,the alternative fuels of RP-3 aviation kerosene and its multi-step chemical reaction mechanism are investigated, it can provide a reliable chemical reaction mechanism for the numerical simulation of two-phase spray combustion process in the gas turbine combustor,afterburner and scramjet combustor. The research contents include three parts, as following:Firstly, n-decane is choosen to be the alternative fuel of RP-3 aviation kerosene and its detailed reaction mechanism which contains 62 species and 344 elementary reactions is determined. The performance of n-decane in the premix burner is investigated and the numerical results are compared with experimental data, it shows that n-decane can be used as the alternative fuel of RP-3 aviation kerosene. The sensitivity analysis and reaction flow analysis method are used to simplify the detailed reaction mechanism of n-decane, and a simplified mechanism which includes 36 species and 62 elementary reactions is obtained. The simplified mechanism is used to simulate the combustion processes in the perfectly stirred reactor and the premix burner respectively, the numrcial results are compared with the experimental data. It shows that, to the equilibrium temperature and major component concentration in perfectly stirred reactor, the numerical results of the simplified mechanism are well agree with that of the detailed mechanism, and to the major component concentrations in premixed burner, the numerical results ot the simplified mechanism are basically agree with that of the detailed mechanism and experiment data. Therefore, the simplified mechanism can be used to predict the combustion characteristics of n-decane well during a wide range.Secondly, the Bunsen burner with premixed pre-evaporated combustion of RP-3 aviation kerosene is designed, and the combustion performance of the Bunsen burner are measured. The experimental results show that the stable combustion fuel gas ratio of Bunsen flame should be greater than 0.0603. When the Reynolds number in the tube is greater than 1150, the laminar flame will make transition to the turbulence flame. The height of flame core, inner flame and outer flame can be got by analyzing the positions of extreme value point, such as the CH4, UCH, CO2 and temperature. The trend of the temperature and gas composition concentrations on the axial direction and the radial direction at different height is basic similar at different working conditions.Finally, based on the experimental system, the numerical simulation object of Bunsen burner is modeled, and theree kinds of alternative fuel of aviation kerosene and the corresponding multi-step chemical reaction mechanisms are applied to numerical simulate the premixed pre-evaporated combustion flame of Bunsen burner, and the numerical results are compared with the experimental data. The results show that the standard k- e turbulence model and EDC combustion model can be used to simulate the premixed pre-evaporated combustion flame of Bunsen burner. The flow field and the distribution of temperature, O2 and CO2 concentration at the center section and different cross sections are basically similar when the three kinds of reduced mechanisms are used to simuate the premixed pre-evaporated combustion flame respectively. When the reduced mechanism of n-decane with 36 species and 62 elementary reactions is applied to simulate the premixed pre-evaporated combustion flame, the distribution of temperature, O2 and CO2 concentration at the axial direction and the radial direction of different heights show good agreement with the experiment data at all the working conditions, it can more accurately and reliably predict the flame temperature and the gas composition than the other two reduced mechanisms. The results of the reduced mechanism with 23 elementary reactions are different from the experimental data, therefore the reduced mechanism of C12H23 with 23 elementary reactions cannot be used to predict the premixed pre-evaporated combustion process of RP- 3 kerosene. The reduced mechanism with 38 elementary reactions can give a certain forecast, such as the temperature on the axial directionat at the lean fuel conditions, and the O2 concentration distribution at rich fuel conditions, but it cannot be used to accurately predict the CO2 distribution.Therefore, the reduced mechanism of n-decane with 36 species and 62 elementary reactions in this paper can accurately predict the actual combustion process of RP-3 aviation kerosene, and it can be used as a reliable chemical reaction mechanism to numerical simulate the combustion process in gas turbine combustor.