Modeling and Control of Combustion Phasing in Dual-Fuel Compression Ignition Engines

TL;DR

This paper develops a simplified, control-oriented combustion phasing model for dual-fuel engines and compares adaptive and feedforward control strategies through simulations, achieving high accuracy in steady state.

Contribution

It introduces a mean-value combustion model and two control strategies for dual-fuel engines, improving control simplicity and computational efficiency.

Findings

Both controllers reach steady state within 5 cycles.

Adaptive control achieves <0.1 CAD steady state error.

Feedforward control achieves <1.5 CAD steady state error.

Abstract

Dual fuel engines can achieve high efficiencies and low emissions but also can encounter high cylinder-to-cylinder variations on multi-cylinder engines. In order to avoid these variations, they require a more complex method for combustion phasing control such as model-based control. Since the combustion process in these engines is complex, typical models of the system are complex as well and there is a need for simpler, computationally efficient, control-oriented models of the dual fuel combustion process. In this paper, a mean-value combustion phasing model is designed and calibrated and two control strategies are proposed. Combustion phasing is predicted using a knock integral model, burn duration model and a Wiebe function and this model is used in both an adaptive closed loop controller and an open loop controller. These two control methodologies are tested and compared in simulations. Both control strategies are able to reach steady state in 5 cycles after a transient and have steady state errors in CA50 that are less than 0.1 crank angle degree (CAD) with the adaptive control strategy and less than 1.5 CAD with the model-based feedforward control method.