Modeling and predictive control of a new injection system for compressed natural gas engines

The accurate metering of the air/fuel mixture in internal combustion engines equipped with Common Rail injection systems strictly depends on the injection pressure regulation. This is a critical objective to be accomplished in Compressed Natural Gas injection systems, as the gas compressibility makes the fuel delivery process more complex. Since the design of a controller requires a model of the injection system, in this paper a physics-based state space model of an innovative Compressed Natural Gas injection system is presented. The model parameters only depend on well defined geometrical data and fuel properties. Comparison of simulation and experimental results for different operating conditions validates the model. Further, the proposed model is used for designing a Generalized Predictive Controller (GPC) for the injection pressure regulation. The implementation of the control law consists of simple steps. Experimental results show the effectiveness of the proposed approach.