Evaluation Methods Research Of Diesel Aftertreatment Devices

With more than 100 years development, the internal combustion engine has become the most efficient power resource. On the one hand, it brings convenience to our life,on the other hand, it brings the serious pollution to city and does harm to human health. Especially for the emission of diesel engines, as it strongly has contribution to cancer, so which is always focus by government departments and people recent years. Diesel vehicles have been used more widely than gasoline vehicles by their better power and economic. But diesel vehicles have been restricted in many big cities for their especial emission pollution. So diesel manufactures are adopting in a series of technical steps in engine to improve emission level of NOx and PM. However when the reduction in engine is to some degree, it need reduction from outside of engine to meet more strict emission regulation requirement. The emission control technology from outside engines has become a research hot focus in developed countries in world. Because aftertreatment works on emission pollution directly, and the effect is more prompt and effective. Practice shows that if the diesel meet the level above Euro III, it must install aftertreatment. It is obvious that developing aftertreatment technology is needed indeed. We must study the advanced experiences from foreign countries in diesel emission control field, and we need to discuss our national diesel aftertreatment technology test evaluate methods with diesel manufactures, aftertreatment manufactures and fuel industries to catch up with international track as soon as possible. This study takes the chance of drawing standard"Technical requirement and measurement methods of diesel aftertreatment devices", and research some aftertreatment evaluate methods according our national situation. More research is done in key performance target, and author provided his opinions, which establish a good foundation for implement regulation in the future.Author set up diesel aftertreatment devices evaluate system and study several aftertreatment work principle and application to set up abundant theory in latter test. Aftertreatment test system is based on engine bench. The engine model is Duramax 6600 V8 which can be saled only in Nor-America. The engine is researched and developed by Labview, which may be calibrated. This engine is famous for his good durability, and can meet aftertreatment durability evaluate test absolutely. Another advantage of this system is SFI (Supplementary fuel injection) installed in exhaust pipe which may inject fuel in exhaust system to increase exhaust temperature, so aftertreatment regeneration is finished. A new CW260 dyno made in Nanfeng mechanical factory, it is stabilized and reliable, and can be programmed to complete mode shift and running automatically. Muti-channel sensors meet the requirement of test inspection. The dyno has massive Microsoft to process real test data. We purchased a MEXA-7500D analyzer which is the newest specialized in catalytical converter research test made in HORIBA Ltd.. It has a cabinet along with two sample pump and oven instead of two control cabinet to measure emission pollution before and after catalytical converter. The configuration of MEXA-7500D is simple and novelty, the test efficiency is more high.This study researches the performance of diesel oxidation catalyst and particulate filter by means of test. It analyzes the DOC effect on diesel exhaust, and researches the performance of DPF pressure drop and filtration. As there are loading condition and regeneration condition for DPF, so test bench was designed for each condition to meet test requirement. The result showed that DPF loading has both effect on pressure drop and filtration. In general, the performance targets of loaded DPF are higher than those of regenerated DPF. This paper mainly studied the process of DPF regeneration, as if the conditions are not controlled well, the uncontrolled regeneration will occur during DPF regeneration. In this paper, three different types of uncontrolled DPF regeneration are studied by test. One is uncontrolled high initial exotherm at the start of DPF regeneration; The other is uncontrolled regeneration, which takes place when the engine goes to idle during normal DPF regeneration; The last one is uneven soot distribution causing excess thermal stress during normal DPF regeneration , which causes hot spot problem. In this study, different control strategies are developed for each of the three types of uncontrolled DPF regeneration. The No. one is to install a DOC before DPF to reduce SOF in DPF and adjusting SFI temperature ramp rate to ensure DPF regeneration safely. The No. two is to increase EGR as well as control through intake throttling to reduce fresh air into engine cylinders. The last one is to improve exhaust flow pattern, for example to install a diffuser at DPF inlet to improve uneven flow and temperature distribution. Test results show that uncontrolled DPF regeneration can be prevented and highly efficient and safe DPF regeneration can be achieved using these control strategies.The purpose of this paper is to set up test regulation of diesel exhaust aftertreatment devices scientifically, and research some rules and factors working on evaluating during test process. These can be analyzed by means of theory to get useful and reasonable methods, which set up a good technical base for developing diesel aftertreatment in the future.