Prediction And Control Of Turbocharged & After-cooled Diesel Engine Emission

In order to meet with the requirement of national emission regulations, engine designer and manufacturer focus on how to reduce the exhaust pollutants efficiently. Many domestic institutes have done emission predict calculation but few of them are directly helpful for manufacture. And the manufacturers always control engine emission by mass of experiments without theoretic prediction aid. In our study, we do some calculations, which based on phenomenology model, to predict how some important parameters affect engine emission, then change related parameters and redesign some key components to improve engine emission performance according to the prediction result.Here we use a prediction software SCOPE to evaluate the trend how the parameters like intake manifold temperature ( IMT ),compression ratio, overall air-fuel ratio, exhaust gas recirculation ratio, fuel injection timing, peak injection pressure and intake air swirl affect NOx , PM and fuel consumption ratio of turbocharger & after-cooled diesel engine. The result shows below: (1) Reducing intake manifold temperature or compression ratio, using EGR or delaying fuel injection timing individually will result in less NOx emission; Increasing overall air-fuel ratio or peak injection pressure individually will conduce to less PM emission. (2) When two parameters act together, they always affect each other, either strengthen or weak others. (3) When the parameters such as intake manifold temperature, start of injection, overall air-fuel ratio, peak injection pressure act together, they will make a great reduction of NOx emission while PM increased a little. It is necessary to look for other efficient way to reduce PM at the same time. (4) using EGR or increasing peak injection pressure seems to be the key factor to break the NOx - PM trade off and reducing them at the same time .Based on the prediction, we chose some efficient, economical measures and redesigned new parts for NTC-330 engine. The result of experiment shows that: (1) The intake manifold temperature drops from 160 ℃ to 55 ℃ by change water jacket aftercooler into a new designed air to air aftercooler and have a great NOx reduction . (2) The Smoke number significant reduced at peak torque speed by optimizing the turbocharger. (3) After redesign the injector, especially decrease the diameter of injecting hole from 0.178mm to 0.152mm , the PM is almost reduced by 45.2%.(4) The heavy smoke are significant improved at middle speed by a new air deflect plate strengthening the intake air swirl. (5) After redesign the camshaft, especially shorten the injection duration and improve the injection pressure,the smoke number reduced more than 50%. (6) The NOx reduced significant by delaying injection timing for 3.6 degrees.We can get conclusion below: (1) the program SCOPE can do a fairly precise prediction for turbocharged & after-cooled engine. (2) the emission control way choosed according to the prediction can reduce exhaust pollutants successfully. (3) NTC-330 meets the national regulation GB17691-2001 stage A by using new air to air aftercooler,new turbochanger and retarding injection timing.With further improvement including new air deflect plate, decreasing the diameter of injection hole and designing a new camshaft, NTC-330 meets the national regulation GB17691-2001 stage B.