Experiment Study On Emission Reduction Of Electronic Control Common-rail Diesel Engine

With the improvement of living level, requirement for the performance of vehicles is getting higher and higher, and with more and more strict emission regulations, diesel engines will face bigger challenge. Diesel engines have better power performance and economy, but higher NOx and somke. It is the inevitable trend to reduce emission with electric control common-rail diesel engine.With a DENSO ECU-U2 high pressure CR system as research object, the relative issues, such as the principle and characteristics of electronically control technique, the design and developments of for electronically control system, as well as the control strategy, are studied. According to the diesel engine combustion characteristics and the requirements of emission regulations, a suitable control strategy and its implementation for high pressure CR system are proposed. Because of the disadvantage of taditional PID control, fuzzy PID control was studied, take fuel injection pressure for instance, simulation of traditional PID and fuzzy PID was studied, the results show that fuzzy controller progresses a better speciality in step response and robustness and disturbance rejection.The running conditions of diesel engines are classified. For each running condition, a corresponding control strategy, including injection quantity, injection timing and common rail pressure, is obtained, which helps to meet the demand of quick start and steady running of engine.A test rig is set up based on a CA6DE direct injection diesel engine equipped with ECD-U2. MAP calibration is accomplished using the online calibration software, combustion analysis software and data acquisition software. The precision, feasibility and reliability of software design are verified by the tests. The experiments indicate that CR injection system has a great potential to decrease the emission and improve the performance of direct injection diesel engines.The pilot injection orthogonal experiment project was designed in this paper, and the effects of fuel injection pressure and the pilot injection on emission and fuel consumption were studied. The results show that high injection pressure and little injection timing can reduce emission; pilot injection can reduce NOx vastly, and the pilot injection can get the optimization between emission and fuel consumption. Based on the results, the optimization points under different working conditions were got. Performance experiment suggests that CR injection system has a big potential to decrease the emission and improve the performance at the same time for diesel engine.