| With the vigorous development of the automotive industry, years of oil resources consumption is increasing year by year, the human into the threat of oil depletion and industrial development needs of contradictions.Air pollution is increasingly serious, more nationwide, especially in the southeast coastal economic developed area, there have been haze weather, the air index for severe pollution, endangering human health directly.Energy saving and environmental protection is still two themes in the research field of the auto industry.Diesel engine occupies an important position in the automotive engine, in a light machine also has its place.Reasonable organization an important role in energy conservation and emissions reduction, combustion of fuel injection pressure have significant influence on the atomization of the fuel quality, thus affecting the rate of fuel and air mixing and distribution in the combustion chamber, and influence the distribution of concentration field of diesel engine ignition and the spread of flame, which in turn affect the combustion emissions generated in the process of situation.With the development of diesel engine, which can realize the fuel injection pressure has increased to 300 mpa and may continue to improve.Such a high injection pressure influence on the energy conservation and emissions reduction of diesel engine and the significance to be clear, so this paper studies the injection pressure of light diesel spray, the influence of the combustion and emissions.The research results are shown below.Firstly,increase injection pressure injection can shorten the duration and improve the quality of atomization, improve the efficiency of fuel and air mixing.Shorten the ignition delay period, pre burn vigorously, the peak heat release rate increases, the burn center of gravity in advance, the combustion duration shorter, the average pressure in cylinder peak peak increases and the average temperature in cylinder.Secondly,when the injection pressure reaches a certain value, we will continue to increase the influence of injection pressure on atomization characteristics co., LTD.In speed and load of different cases, the airflow movement in cylinder, specific to what value after limited impact on the quality of atomization is not the same.Although continue to improve the quality of injection pressure on the atomization effect of smaller, but especially in the high speed or high load conditions, especially the load, the greater the increase of injection pressure on the injection duration shorten effect more apparent, shorten the injection duration of fuel concentration field distribution are not allow to ignore, so continue to improve the injection pressure on combustion conditions.Thirdly,at low speed and low load(1000 r/min- 20% load), using low injection pressure, by avoiding hit a wall, realize space mix, improve the efficiency of hybrid instead.So in the case of low speed and low load, cannot set too high injection pressure, and injection pressure can not arbitrarily raising, low load fuel injection quantity is small, the injection pressure fuel injection duration shortened, in the actual use of injectors cannot achieve precise injection.Not only increase the fuel injection control system wear and increase the difficulty, also affect the engine performance.Under the conditions of the light diesel prototype, the optimal injection pressure is around 60 Mpa.Fourthly, when the engine is low speed, because the gas turbulent flow movement in cylinder is not strong, generally easy to fuel up against the wall;With high speed because of the gas in cylinder turbulent motion is strong, and general fuel hit a wall is not easy to happen.And because of the different rotating speed, the turbulent motion in cylinder, the existence of oil beam Angle is different, because the prototype for omega type combustion chamber, the higher the speed, oil beam in the greater the Angle between the cylinder axis.Lastly,Improve the injection pressure to make more homogeneous mixture, avoid local oxygen zone, soot emission reduction.Generally increase injection pressure can make the burning violently, temperature increase, reduce HC and CO emissions, and NOx emissions continue to increase.But in the case of small load, due to the diesel engine air-fuel ratio is compared commonly big, especially in high speed small load causing too loose mixture concentration, and make the HC emissions increase.And within the scope of the individual conditions and injection pressure, due to combustion and the heat generated by the severe in advance, on the contrary make CO generation increases, and combustion duration is shorter, inadequate late oxidation, CO emissions continue to increase.In high speed small load, excessive concentration field distribution of the uniform can realize low temperature burning, reduce NOx emissions. |
PDF Full Text Request