Research On Control Of Work Process And Emission Of Diesel Engine Under Cold Conditions

Energy crisis and environmental pollution are two serious problems to human beings.Energy crisis can be alleviated by means of saving energy and developing new energy sources.The exhaust of pollutants are limited and decreased by means of legislation and developing advanced technology.Diesel engine is widely used in the world due to its high thermal efficiency and good economy.The power loses,fuel consumption and emissions increase would occurred when the diesel engine were run under cold conditions,which aggravated the energy crisis and environmental pollution.So researches on the performance of diesel engine under cold conditions were necessary.Combustion optimization and exhaustion control of diesel engine under cold conditions were done in this paper,which aims to improve the power ability,fuel consumption and to decrease emission.The methods that combined simulation and experimentation were used to study the 4102ZLQ diesel.The prediction model of spray,combustion and exhaustion were used to simulate the fluxion,spray and combustion.In the fuel spray and mix model,discrete phase liquid droplets model has been used to simulate the movement of fuel liquid droplets.Multi-injection solid cone injector source and Rosin-Rammler distribution have been used to distribute fuel injection.The breakup of fuel liquid droplets has been simulated by Wave Breakup model. Turbulent flow has been simulated by Renormalization Group Theory (RNG)κ-εformula and near-wall region turbulent flow has been amended by wall functions.In combustion calculation,net production rate has been gained based on combining the laminar finite-rate model and the eddy dissipation model.Diesel combustion has been described by single step reaction.The simulation of diesel engine performance under cold conditions was based on the credible results of comparison between simulation and experiment.Gas fluid,spray development,distribution of spray liquid, temperature field and pressure field were performed by simulation results. The regular rule of in-cylinder fluid,the features of turbulence and eddy, the features of the nitrous oxide and Soot formation were analyzed.The result that compared simulation with experimentation shown that the three-dimension combustion model can be used to simulate the combustion process of diesel engine and to evaluate performance parameters of the engine.Three-dimension combustion model were used to simulate performance of diesel engine under cold conditions.The factors of power and emissions were analyzed,and counter measures were proposed.Pressure of inlet air and fuel injection advance angle were adjusted to improve the engine performance and exhaustion.The results showed that the region of low temperature extended when the diesel engine run under cold conditions compared with normal conditions,and that the formation of combustion mixture was weaken which decreased the power.The power of engine can be enhanced by adjusting the pressure of inlet air in a certain scope.The NOx emission was increased along with the increasing of combustion temperature,but it has few effects on Soot emission.The in-cylinder temperature was increased for larger injection advance angle.And the NOx emission was increased because of the longer lag period,but the formation of Soot emission decreased.The problem of power loses in cold conditions can improved effectively by increasing the injection advance angle.In addition,NOx emission increased and Soot emission decreased.