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A dynamic model of a Heavy Duty (HD) turbocharged and aftercooled diesel engine was developed. The engine was equipped with high pressure diesel injection, a Variable Geometry Turbine (VGT) and an Exhaust Gas Recirculation (EGR) system. This engine was targeted at meeting EURO4 emission requirements. The final emission results were 2.4 g/kWh NOx and 0.107 g/kWh particulates for the European 13 mode test. Better than 3.0 g/kWh NOx and 0.10 g/kWh particulates are expected to be characteristic EURO4 emission requirements (approximate year of implementation is 2004). In the design of the EGR system the model provided initial assessments of the properties of this system. Associated engine and turbocharger behaviour as well as optimal control strategies were predicted. A transient engine control algorithm was developed using the dynamic engine model. The VGT is closed loop controlled and EGR is shut off during a short time after a load increase.

The lengthy experience of TNO with the application of gaseous fuels in engines is discussed. The emphasis is on emissions and efficiency of optimal gaseous fuelled engines in comparison to systems with partial diesel fuel replacement. In spark ignition operation (100% diesel fuel replacement) lean-burn and stoichiometric (electronic control and 3-way catalyst) concepts have been developed. In the optimization mathematical modelling of combustion and flow phenomena is used in combination with engine test bed work. Essential new hardware including micro-electronic control systems is developed. It has been demonstrated on test bed with CNG and LPG that the US HD Diesel Standards of 1994 can be met in the diesel transient cycle. Sufficient lifetime of the system has yet to be demonstrated however.