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

In internal combustion engines equipped with the common rail injection system the accurate metering of the air/fuel mixture strictly depends on the pressure regulation. Accuracy in metering is difficult to be achieved especially for compressed natural gas (CNG) injection systems, as the gas compressibility makes the fuel delivery process more complex. Since the controller design requires a model of the injection system, this paper presents a physics-based state-space model of an innovative CNG injection system. The model parameters only depend on well defined geometrical data and fuel properties. Comparing simulation and experimental results in different operating conditions validates the model. Further, the proposed model is used for designing a generalized predictive controller for the injection pressure regulation, which is implemented in few steps. Experimental results show the effectiveness of the proposed approach. (C) 2008 Elsevier Ltd. All rights reserved.