Abstract
The key challenges of passenger car today are to reduce carbon dioxides and to clean up exhaust gas emission. For practical use of homogeneous charge compression ignition (HCCI) engine, wider operating range, combustion changing and robust control for different usage situation (e.g. fuel quality, parts degradation) is needed. The objective in this research is to develop robust control that is included detection technologies of combustion fluctuation, combustion noise and nitrogen oxides (NOx) emission on HCCI.
In this paper, a crank angle sensor, a knock sensor and an ion current sensor were applied as detecting applications for combustion conditions. A crank angle sensor and a knock sensor were mass production. An ion current sensor was a trial piece that equipped a general electric circuit. Combustion fluctuation was detected by rotational fluctuation using a crank angle sensor. An optimization of detecting timing was decided by a calculation of output shaft torque. Combustion noise was detected by a power of engine vibration using a knock sensor. An optimization of detecting frequency was decided by a result of Draper’s equation. NOx emission was detected by integral value of ion current. Above described detection methods were validated detecting performance on dyno.
A coefficient of determination between combustion fluctuation standard deviation of indicated mean effective pressure and rotational fluctuation achieved 0.8 for each cylinder. A coefficient of determination between combustion noise (rate of maximum pressure rise) and power of engine vibration achieved 0.9 for each cylinder. NOx emission had a high correlation with integral value of ion current. Therefore highly detecting performance was provided by using these correlations.
An important limitation of this study is the limited test on internal exhaust gas recirculation HCCI using negative valve overlap.
To develop detection technologies of combustion conditions that adapted to HCCI, to combine these technologies for robust control, and test results of stabilizing HCCI combustion on real engine are new points presented in this paper.
We had developed robust control for stabilizing HCCI operation. Detecting technologies of combustion condition in this control were combustion fluctuation detection using a crank angle sensor, combustion noise detection using knock sensor, and NOx emission detection using ion current sensor.
KEYWORDS – Homogeneous charge compression ignition, Stability, Crank angle sensor, Knock sensor, Ion current sensor