Research On The Effect Of Crankcase Blow-by Gas On Engine Particulate Emissions

As environmental climate change and energy issues become increasingly prominent,especially the haze continues to increase,the government began to pay more and more attention to energy conservation and emission reduction.Traditional automobile is one of the main sources of emissions,with the increasingly stringent emission regulations,the modern engine due to technological progress so that the engine structure becomes more and more optimized,particulate emissions are less and less,the attendant problem is the crankcase blow-by gas on the proportion of particles increased.The GDI engine emission particles under the influence of crankcase blow-by gas is relatively larger,leading the engine research and development personnel pay more attention to the crankcase blow-by gas on the engine particulate emissions.Therefore,based on the engine test bench and the optical test platform,this paper studies the variation law of the crankcase blow-by gas on the engine particles,the specific content is as follows:1.Carried out 2.0L supercharged diesel engine and 1.4TGDI engine blow-by gas test.It is found that diesel engine blow-by gas rate maximum value in the medium speed full load conditions,under the same load from the medium speed to the maximum speed in the process of blow-by gas change little.The blow-by gas flow rate of the gasoline engine increases with the increase of the torque,and the speed has little effect on the blow-by gas rate.2.Particle measurement tests were carried out on the engine bench,study 1.4 TGDI engine respectively in the speed of 1000r/min,2000r/min and 3000r/min,different blow-by gas under different load distribution characteristics of engine particles,including the particle number concentration,mass concentration and surface area concentration.1)Under the condition of 1000r/min,different load and different blow-by gas state,the particle number concentration is still dominated by nuclear modal particles,the mass concentration is dominated by the accumulation mode particles,accumulation mode surface concentration gradually reduce with the increase of the blow-by gas,the particles concentration gradually from the accumulation mode to the nuclear mode.The blow-by gas mode was mainly the nuclear mode component,and the peak value of the particle size increased to the large particle size,the concentration of the nuclear mode of the particles increased exponentially,and the accumulation mode mass concentration and surface area concentration increased significantly under high load.2)Under the condition of 2000r/ min,different load and different blow-by gas state,the number?mass and surface area of the particles accumulation mode were the largest in the load 60N·m and 250N·m,while the load 200N·m less impact,the particle number concentration? mass concentration and surface area concentration is still dominated by accumulation modal particles,indicating that the engine emissions at 2000r/min200N·m are optimal.3)Under the condition of 3000r/min,different load and different blow-by gas state,the particle number concentration changed from double peak to triplet with the increase of blow-by gas,the blow-by gas component was mainly concentrated in 14~110nm,especially the number concentration of the particles accumulation mode,the change of the number concentration? mass concentration and surface area concentration at 200N·m was the most obvious.3.The visualization of influence of crankcase blow-by gas on GDI engine particle generation process on optical experiment platform,by changing the blending ratio of oil and gasoline,the combustion of crankcase blow-by gas and fuel in the combustion chamber was observed,explore the mechanism of blow-by gas and fuel mixing to generate particles.The tests show that the formation process of the particulate is mainly due to the dynamic equilibrium between the particulate formation process and the oxidation reaction process,with the increase of the blending ratio,with the increase of the blending ratio will hinder the flame propagation speed and particle oxidation reaction process,is conducive to the formation of particles,affect the luminous intensity of the flame,so that the burning time becomes longer,the change of particle mass with time is similar to that of natural flame luminosity,and it is a single peak distribution,and there is a maximum point.