Research Of The Combustion Characteristics Of Heavy Duty Vehicle Preheater

The vehicle preheater has been promoted and widely used in the air-conditioningsystem to solve the vehicle cold start problems in fuel economy and environmental pollution.The combustion process of vehicle preheater consists: flow combustion between the fuel andthe air; flow heat transfer between the high temperature gas and the external fluid.The combustion characteristics of heavy duty vehicle preheater were researched bytheoretical analysis, experimental test and numerical simulation.Firstly, the theory of vehicle preheater combustion process was analyzed combiningwith experimental data to obtain actual air-fuel ratio data, which was the boundary conditionof the three-dimensional simulation. Vehicle preheater combustion process was simulated toresearch the combustion characteristics of vehicle preheater. Meanwhile, the parameters ofthe preheater characteristic structures, preheater performance was analyzed. Finally, theexperimental data and simulation data were compared to verify the accuracy of thesimulation.The combustion process of the vehicle preheater relates to the theory ofthermochemistry, chemical kinetics and heat-mass transfer. The problems of stoichiometry,reaction heat, heat value and chemical equilibrium etc. were solved to research thecombustion process, which provided the theoretical basis and boundary conditions forvehicle preheater simulation.The vehicle preheater was simulated to research the combustion characteristics of thepreheater combustion chamber in this paper. The combustion characteristics were researchedto find the optimal combustion process. The preheater region was divided to make it moreclose to the actuality. Through the analysis of fluid flow of gas flow field and external flowfield, the residence time of fluid was extended in flow field to promote fuel combustion andheat transfer. The data of gaseous components and temperature were analyzed, whichindicated that fuel was complete combustion and carbon monoxide emission was inreasonable range. However, small amounts of nitric oxidewas produced due to effect of thehigh temperature. According to the analysis of heat transfer of preheater, the flow of airrelatively disordered to promote air preheat and combustion.Through processing the parameters of the nozzle diameter, the conical hood diameter, the combustion tube length and the fin height, conclusions are as follows: when the nozzlediameter was1.0mm, elected flame was obviously produced to promote combustion andemission; when the conical hood diameter was70.0mm, both can meet the requirements ofthe gas flow, and promote d combustion of fuel in the combustion chamber; when thecombustion tube length was300.0mm, vortex can be avoided in the heat exchanger structureflow field area, and temperature of secondary combustion chamber was uniform; when thefin height was12.0mm, both can meet the flow requirements of the gas in the combustionchamber, andalso ensured temperature requirements of the water outlet.The preheater performance was tested to obtain experimental data. In the earlypreheater operation, the test results indicated that combustion of fuel was incomplete, andemitted higher carbon monoxide. In the low-temperature environment, the emissions ofnitric oxide were decreased, but emissions of carbon monoxide and unburned diesel werehigher. The error of experimental data and simulation data was less than5percent, whichverified that the simulation results were accurate.