Two-Input Two-Output Control of Blended Fuel HCCI Engines

Precise cycle-to-cycle control of combustion is the major challenge to reduce fuel consumption in Homogenous Charge Compression Ignition (HCCI) engines, while maintaining low emission levels. This paper outlines a framework for simultaneous control of HCCI combustion phasing and Indicated Mean Effective Pressure (IMEP) on a cycle-to-cycle basis. A dynamic control model is extended to predict behavior of HCCI engine by capturing main physical processes through an HCCI engine cycle. Performance of the model is validated by comparison with the experimental data from a single cylinder Ricardo engine. For 60 different steady state and transient HCCI conditions, the model predicts the combustion phasing and IMEP with average errors less than 1.4 CAD and 0.2 bar respectively.

A two-input two-output controller is designed to control combustion phasing and IMEP by adjusting fuel equivalence ratio and blending ratio of two Primary Reference Fuels (PRFs). The designed controller consists of a Discrete Sliding Mode Controller (DSMC) and a feed-forward integral controller. The results of testing the controller on a detailed complex HCCI model shows the controller can accurately track both IMEP and combustion phasing over a range of HCCI operating conditions. In addition, the designed controller shows the ability to maintain a minimal disturbance to desired combustion phasing and IMEP when the engine speed and the intake manifold temperature change.