Study On Transient Operating Conditions And Control Strategy Of High Pressure Common Rail Diesel Engine

Diesel engine transient operations are the intermediate state when diesel engine switches from one steady operation to another steady operation, during this period the torque or speed of engine is constantly changing over time. The typical transient operations including starting, load increase and acceleration transient event. Under the daily driving schedule of automotive, especially on urban roads, the diesel engine is inherently related to unsteady conditions. Compared with the steady operations, there is a vast difference on the emission, thermodynamic, kinetic and many other features of diesel engine under the transient operations. The most critical conditions encountered by automotive engines are met during transient events, and some components of emission during transient operation are higher than steady operation.As the national stage IV emission standards full implementation were required from January 1,2015, and the compulsory certification of diesel emissions during transient operations was required since national stage IV emission standards. Thus, a depth study of transient operations of diesel engine, and a reasonable and effective control strategy for transient operations are very necessary and urgent for improve the transient performance of diesel engine.In order to improve the performance of diesel engine during transient operation, the characteristics of typical transient operations, such as starting, load increasing and acceleration were described. Different aspects of the features of diesel engine during transient operations were conducted a systematic analysis, such as system delays, in-cylinder processes, kinetic factors and emission mechanism. On this basis, combined with high pressure common rail diesel engine electronic control technology, the control strategies of starting control, torque structure, injection control and rail pressure control during transient operations were studied, the control model of transient operation was built by MATLAB/SIMULINK software, and the embedded C code was downloaded in the self-developed development ECU. After the key MAPs was calibrated, in order to verify the control strategies, the typical transient operations, such as starting, load increasing and acceleration were tested on the engine test bed by use YN30CR high pressure common rail diesel engine.The results showed that the change of the control parameters during these three transient operations such as engine running state, calculated torque, fuel quantity, injection parameters and rail pressure control parameters were all fit the design requirements of the control strategies, the operation parameters such as torque and speed were fulfill the performance characteristic of diesel engine. The engine showed good response and stability performance, indicated that the control strategies were effective and reasonable.