“We have considered the technical trend of Euro 6 heavy-duty diesel engines. The conventional route is to use EGR to reduce the nitrogen oxides in the cylinder to about 3 grams, and then use DPF to reduce the particulate matter to the standard required by Euro VI, and then reduce it through SCR. Residual nitrogen oxides. According to this technical route, we have successfully developed the Euro 6 diesel engine and obtained EU certification.†From December 2nd to 3rd, 2014, Weichai Power Co. , Ltd. promoted the meeting on the promotion of energy-saving, emission reduction and sustainable development of internal combustion engines. Dr. Li Qin, a joint stock company limited company, said: "But there is a problem. The characteristics and difficulties of the traditional European 6 technical route are that the high EGR rate of the whole spectrum leads to a shortage of full-loaded oxygen. In order to maintain the previous power, a high boost is needed. To make up for it, this raises the highest burst pressure in the cylinder and requires a redesign of the engine ."
Li Qin: Efficient SCR and passive regeneration will be the key technologies in Europe VI
It is understood that the bottleneck of the traditional European six technical route is that it needs to withstand the outbreak pressure of more than 200 bar. It will take 5 to 10 years for this platform to be upgraded to the market acceptance level. Another approach is to significantly reduce engine power (by more than 15%), but it is difficult to gain market acceptance.
“In this context, we invented our own low-explosive pressure program without altering the engine. Later, we found a better solution, which was to remove the EGR cooler, the SCR uncooled EGR solution. Now, from Europe, another One piece of information is the pure SCR solution.†Li Qin further explained: “The advantages of the EGRless diesel engine include not requiring too high boost pressure, not generating excessive explosion pressure, and relatively inaccurate requirements for the supercharger and fuel injection system. Low, no need to increase the demand for vehicle cooling system, and reduce various failures caused by EGR system.In addition, under the same conditions, pure SCR has the advantage of operating cost, and this advantage is more important for the Chinese market that value the cost. Based on the above analysis, I think there is no prospect for EGR on heavy-duty engines."
Another major problem facing Europe VI is the regeneration of DPF, which includes passive regeneration and active regeneration.
"Active regeneration is achieved through engine measures to achieve a DOC front-row temperature of more than 300°C. An oxidation reaction occurs in the DOC after the fuel injected in the cylinder or exhaust pipe. The temperature of the exhaust gas entering the DPF is raised to above 600°C, driving the PM. The DPF is oxidized, but its biggest problem is to accurately estimate the carbon load.If the carbon load is too large, it will cause the DPF to burn, and if the carbon load is too small, it will cause the DPF to be incompletely regenerated, and the effective length will be shortened. It can be seen that the DPF regeneration control has a high requirement for product consistency and a large amount of calibration work. From my experience, DPF is the most difficult to do with so much post-processing work.â€
Fortunately, passive regeneration occurs when the emission control level is upgraded to Euro 6, and the principle is to oxidize nitric oxide in the DOC to nitrogen dioxide. Nitrogen dioxide is more active than oxygen and can oxidize PM at 300°C. In addition, passive regeneration does not require much calibration work.
Therefore, Li Qin concluded that efficient SCR and passive regeneration will be key technologies for heavy-duty diesel engines in the future.
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