Impact Theory Based Total Cylinder Sampling System and its Application 2008-01-1795
A novel non-destroy repeatable-use impact theory based total cylinder sampling system has been established. This system is mainly composed of a knocking body and a sampling valve. The knocking body impacts the sampling valve with certain velocity resulting in huge force to open the sampling valve and most of the in-cylinder gas has been dumped to one sampling bag for after-treatment.
The feasibility and sampling response characteristics of this impact theory based total cylinder sampling system were investigated by engine bench testing. Within 0 to 35°CA ATDC (Crank Angle After Top Dead Center) sample timing 50 percent to 80 percent of in-cylinder mass would be sampled, which was a little less compared with the traditional system. The half decay period of pressure drop was 10 to 20 degrees crank angle within 0 to 60°CA ATDC sample timing, which was about 2-3 times of the traditional system. The in-cylinder pressure histories were of highly consistency which certificated the application ability in engine chemical kinetics research.
The PM and its DS fraction shaped one-peak history, the peak value appeared at 20°CA ATDC. The PM quantity history reaches its peak value at about 30°CA ATDC. At any crank angle the diameters of formed PM own two centers, one is smaller than 0.01μm and the other is 0.133μm. NOx formation history shaped like S, and most of the NOx formed within 20°CA after combustion began. The PM quantity kept almost the same, however the DS fraction increased under transient operations. The effects of EGR on in-cylinder PM and DS behavior investigation showed that the weak oxidation of DS resulted from recirculated gas was the main reason for lower in-cylinder PM and DS peak value and higher PM emission.