Research On Mechanism Reduction Method For Low Temperature Combustion And Plasma Assisted Combustion Of Hydrocarbon Fuel

Combustion as an important means of energy conversion,its high efficiency and cleanliness have a significant impact on energy and environmental issues.Low-temperature combustion technology has significant advantages in energy saving and emission reduction,and has been highly valued in recent years.However,the low temperature combustion has the problems of poor combustion stability and complicated dynamic mechanism,which greatly hinders the analysis of reaction flow and the promotion of low temperature combustion technology.In this paper,aiming at low-temperature combustion reaction flow dynamics simulation,we seek the mechanism reduction methods suitable for low-temperature combustion and plasma assisted combustion.The main work and results of this article are as follows:(1)Due to the increasing attention of low temperature combustion,more precise and convenient low temperature chemical reaction mechanism is needed in the combustion reaction flow modeling.However,most of the conventional mechanism reduction methods are difficult to deal with the low temperature mechanism.In order to reduce the low temperature combustion mechanisms of hydrocarbon fuel efficiently,an improved path flux analysis mechanism reduction method(PFA)is proposed.In the improved reduction method,in addition to considering the coupling with the preselected components,the influence on the heat release should be fully considered.By comparing the reaction flow of the method with the traditional PFA method in the process of homogeneous ignition and flame propagation of heptane and octane,the accuracy and efficiency of the improved method(PFAHRR)are fully confirmed.The PFAHRR method is used in the mechanism reduction software Chem RC,which greatly improves the accuracy and efficiency of the software.This new method and tool provide an effective means for the analysis of combustion characteristics of hydrocarbon fuels,especially low temperature kinetics.(2)Aiming at the problem that plasma assisted combustion kinetics analysis need to deal with a large number of components and elementary reactions,and there is no mature mechanism reduction tool at present,then a method of plasma assisted combustion kinetics mechanism reduction is proposed.In order to reduce the kinetic mechanism of plasma assisted combustion,for the vibration excited state reaction,a method to classify the vibration excited state quenching reaction and characterize it with a representative reaction is proposed.The mechanism of CH4/CO2/HE mixture is used to calculate the ignition process of the reduced mechanism and detailed mechanism in the zero-dimensional plasma model,and the important parameters such as ignition delay time,temperature,and concentration of some components are compared and analyzed.The calculation results prove the accuracy of the reduced mechanism and verify the correctness and effectiveness of the mechanism reduction method.(3)In order to test the usability of the mechanism reduction method proposed in this paper in the simulation of complex reaction flow,and to study the basic characteristics of plasma assisted combustion,based on the reduced mechanism,and using the computational fluid dynamics software FLUENT to simulate the methane/air diffusion jet combustion process.The accuracy of the model and reduced mechanism are verified by the comparison and analysis of the numerical calculation results and the experimental results.By comparing the temperature field of the reaction flow and the O,OH mass fraction cloud diagram,when adding free radicals under different conditions of ignition flow temperature,different input energy,etc.The main factors that affect the plasma assisted combustion process are analyzed.And the results show that the free radicals at the high temperature pilot flow inlet will increase the overall temperature without changing the flame shape.The free radicals at the low temperature pilot flow inlet will cause the overall temperature to increase while the jet flame shape will change.Free radicals at fuel flow inlet will advance the whole reaction process.This paper proposes a mechanism reduction method which coupled the improved path flux method and heat release analysis to deal with low temperature combustion mechanism,and a lumped multi-level vibration excited state quenching reaction mechanism reduction method to deal with plasma assisted combustion mechanism.These mechanisms create conditions for simulating the reaction flow.