Combustion Phasing Modelling and Control for Compression Ignition Engines with High Dilution and Boost Levels

TL;DR

This paper develops and validates a nonlinear combustion phasing model for diesel engines with high dilution and boost, and designs adaptive and feedforward controllers to improve combustion timing accuracy during transients.

Contribution

It introduces a simplified, calibrated combustion model and compares adaptive and feedforward control strategies for precise combustion phasing in challenging engine conditions.

Findings

Adaptive control achieves steady state in ≤5 cycles with errors <±0.1 CAD.

Feedforward control reaches steady state with errors <±0.5 CAD.

Model validation confirms accuracy under high EGR and boost conditions.

Abstract

Because fuel efficiency is significantly impacted by the timing of combustion in internal combustion engines, accurate control of combustion phasing is critical. In this paper, a nonlinear combustion phasing model is introduced and calibrated, and both a feedforward model-based control strategy and an adaptive model-based control strategy are investigated for combustion phasing control. The combustion phasing model combines a knock integral model, burn duration model and a Wiebe function to predict the combustion phasing of a diesel engine. This model is simplified to be more suitable for combustion phasing control and is calibrated and validated using simulations and experimental data that include conditions with high exhaust gas recirculation fractions and high boost levels. Based on this model, an adaptive nonlinear model-based controller is designed for closed-loop control, and a feedforward model-based controller is designed for open-loop control. These two control approaches were tested in simulations. The simulation results show that during transient changes the CA50 (the crank angle at which 50% of the mass of fuel has burned) can reach steady state in no more than 5 cycles and the steady state errors are less than +/-0.1 crank angle degree (CAD) for adaptive control, and less than +/-0.5 CAD for feedforward model-based control.