  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.
