Improve Cylinder-to-Cylinder Consistancy and Reduce Cycle-to-Cycle Variations of a Diesel Engine Using Closed-loop Control of Fuel Path Input Variables

摘要

This paper presents that the dwell time between two consequent injection pulses of a diesel engine that is equipped with a common rail fuel injection system has big impact on the combustion process. It is because the change of dwell time has influence on the injection pressure for the next injection. This phenomenon was then used in implementing a Indicated Mean Effective Pressure (IMEP) closed-loop control system to reduce the cycle-to-cycle combustion variations. The injected fuel quantity based IMEP closed-loop control system was also implemented and tested on the test diesel engine. Its disturbance rejection ability has been experimentally investigated to confirm that with this IMEP closed-loop control, diesel engine has strong disturbance rejection ability which implies that a speed governor with IMEP closed-loop control being the inner loop will improve engine speed control performance. Such two-loop speed control system was implemented and tested on the test engine in the lab. The inner IMEP closed-loop control for each cylinder has the same setpoint value which was calculated from the outer loop speed controller. This will increase the combustion consistency among all cylinders.