Modeling, validation and system identification of a natural gas engine

In this paper, a model of a central fuel injected natural gas engine with transmission is developed and linear system identification is carried out to identify key model parameters that could lead to automated identification of transmission dynamics. The paper has two major components. First, the natural gas engine is modeled with an extension of the mean value engine model having three state variables: intake manifold pressure, fuel fraction in the intake manifold and the engine rotational speed. The model is validated in steady state and transient regimes over the whole range of engine speed. Second, a linear system identification algorithm is implemented in simulation on the engine model with perturbation in throttle opening and the speed to throttle transfer function is identified. Effective engine/driveline inertia can be found from the denominator coefficients of the identified model