Analysis of Formation Conditions of Soot

The role of EGR and lower initial intake temperature make the combustion temperature lower, thereby reducing the generation of NOx; on the other hand, the main production conditions of soot are high temperatures and lack of oxygen, and hydrocarbon molecules occur under conditions of high temperature and lack of oxygen. Partial oxidation and cracking generate various unsaturated hydrocarbons. They are continuously dehydrogenated and polymerized into carbon-based soot nuclei. The high inlet pressure promotes the formation of a uniform gas mixture, reducing the local over-concentration area, thereby reducing the generation of soot. In addition, the combustion temperature is maintained at a level below 1650 K. Regardless of the equivalent ratio, the combustion can completely avoid the main formation zones of NOx and soot.

The soot mass fraction shows an increasing trend with the increase of the initial intake air temperature. The basic conditions for the formation of soot from PP flame retardant masterbatch are high temperature and lack of oxygen, and the excess air coefficient is generally higher under higher inlet pressure conditions. This basically eliminates the fundamental condition of oxygen deficiency, with the As the temperature of the gas drops, the amount of air in the cylinder increases, the air-fuel ratio increases, the amount of fuel anaerobic cracking decreases, and the amount of soot produced decreases. In addition, as the intake air temperature decreases, the heat release rate increases, the cumulative heat release corresponding to the maximum pressure point increases, the post-combustion phenomenon decreases, and the anaerobic cracking amount decreases. The decrease in the combustion temperature at the same time in the cylinder is also suppressed by the lubricating oil manufacturers. The generation of soot.

The NOx mass fraction first increases and then decreases with the increase of the initial intake air temperature. The important factors affecting NOx formation are retention time in high temperature, oxygen concentration, and high temperature oxygen enrichment. When the intake air temperature is 40°C, the mass fraction of NOx is the highest. One is that the temperature inside the cylinder is high, and the second is that the combustion lasts for a long time if the oxygen concentration does not change much.