Study Of Technologies To Lower HC And CO Emissions In Low And High Temperature Two-stage Combustion

As a new combustion model of diesel engine, the low and high temperature two-stage combustion have the potential to reduce NOx and PM emissions at the same time. But it also causes significant increment of CO and HC emissions so that would lead thermal efficiency to drop. So it is very important to find ways to lower CO and HC emissions under the circumstance of maintaining low NOx and PM emissions.The experiment was done on a CA6DL2-35E3 diesel engine which is a turbocharged and intercooled common-rail diesel engine. During the experiment, on one hand, learning to use INCA calibration system to control injection parameters that the experiment needs to study; on the other hand, making the experiment by the method of research in stages. Firstly, researching the low temperature combustion stage alone, then analyzing the influences of pilot injection parameters on the low temperature combustion stage. Optimizing the pilot injection parameters to reduce CO and HC emissions as many as possible, but we must ensure low NOx emissions. Secondly, analyzing the influences of main injection parameters on the CO and HC emissions of the low and high temperature two-stage combustion. Thirdly, exploring the possibility of changing post injection parameters to reduce the CO and HC emissions of the low and high temperature two-stage combustion. Main experiment conclusions are as follows:1. During the low temperature combustion stage, increasing pilot injection quantity or posting pilot injection timing could reduce HC and CO emissions, but it would be restricted by pressure raise rate and NOx emissions. And the NOx emissions limit is more outstanding.2. Comparing to single pilot injection, increasing pilot injection times could make the state controllability of the fuel and air mixture increase, and could reduce HC and CO emissions, improve fuel economy by increasing pilot injection quantity or posting pilot injection timing properly, and could be able to keep NOx emissions mainly unchangeable at the same time. But as pilot injection time increases, the improvement degree of emission and economy performance significantly decreases. When using multiple injections, among all the different injection strategies, the strategy of distributing fuel uniformly is the best at the overall performance of emission and economy.3. Advancing main injection timing could reduce the CO and PM emissions of the low and high temperature two-stage combustion, and could improve fuel economy. But it would be restricted by the NOx emissions. The change of main injection timing nearly has no effect on HC emissions. In the low and middle load range, as the main injection quantity increase, the emissions of CO and HC would be reduced constantly, the PM emissions would be also reduced, and fuel economy would be improved. But the NOx emissions would be increasing. While the main injection quantity is overmuch, the combustion would deteriorate so that the CO and HC emissions would start to be increased, PM emissions would be increased significantly, and fuel economy would be reduced. On the contrary, the NOx emissions would be reduced.4. The change of injection pressure has a little influences on the HC emissions of the low and high temperature two-stage combustion. Increasing injection pressure could reduce CO and PM emissions, and could improve fuel economy. But it is also restricted by the NOx emissions.5. When the total fuel quantity of main and post injection is 68mg/cyc, any adjustment of post injection parameter could not reduce the CO and HC emissions. But if we match the post injection parameters reasonable, we could reduce the NOx and PM emissions. While the fuel economy would be reduced.6. Although optimized multiple pilot injection could reduce the CO and HC emissions in the low temperature combustion stage, it have no help to reduce the final CO and HC emissions of the low and high temperature two-stage combustion. On the contrary, it will increase the CO, HC and PM emissions. However, it is helpful to reduce the NOx emissions further.