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In practical applications of ammonia SCR aftertreatment systems using urea as the reductant storage compound, one major difficulty is the often constrained packaging envelope. As a consequence, complete mixing of the urea solution into the exhaust gas stream as well as uniform flow and reductant distribution profiles across the catalyst inlet face are difficult to achieve. This paper discusses a modeling approach, where a combination of 3D CFD and a lumped parameter SCR model enables the prediction of system performance, even with non-uniform exhaust flow and ammonia distribution profiles. From the urea injection nozzle to SCR catalyst exit, each step in the modeling process is described and validated individually. Finally the modeling approach was applied to a design study where the performance of a range of urea-exhaust gas mixing sections was evaluated.

The design of an air to fuel ratio (AFR) control system is substantially facilitated by a suitable mathematical model of the mixture formation process. Such a model has to be a compromise between short simulation times and good prediction capabilities. Well-known simple “linear” wall-wetting models are easy to use but require substantial calibration time to experimentally determine the operating point dependent model parameters. Full 3D simulations of all physical effects are still computationally not tractable. In this work a control oriented mathematical model of the mixture formation phenomena has been built, which tries to find a middle way between these two extremes. Computation times for one engine cycle are less than half a minute on a standard Pentium-PC. Nevertheless, the model is able to predict nonlinear effects that cannot be described by conventional wall-wetting models.

This paper presents a control-oriented mean-value model of a pressure wave supercharger (PWS) which is coupled to an SI-engine. The model is able to predict the engine's intake pressure and other main process variables. The model is validated by stationary and transient measurements on an engine dynamometer.

The energy management of a hybrid vehicle defines the vehicle power flow that minimizes fuel consumption and exhaust emissions. In a combined hybrid the complex architecture requires a multi-input control from the energy management. A classic optimal control obtained with dynamic programming shows that thanks to the high efficiency hybrid electric variable transmission, energy losses come mainly from the internal combustion engine. This paper therefore proposes a sub-optimal control based on the maximization of the engine efficiency that avoids multi-input control. This strategy achieves two aims: enhanced performances in terms of fuel economy and a reduction of computational time.

Instantaneous in-cylinder pressure, a key variable in the improvement of engine performance and reduction of emissions, is not likely to be measured directly in production type engines in the near future. As a countermeasure, a pressure estimation method based on physical first principles for the estimation of the instantaneous in-cylinder pressure of an SI engine using measured crankshaft angular velocity is presented here. The approach consists of (a) mapping the model parameters at nominal operating conditions and (b) adapting the model parameters to current operating conditions using the instantaneous crankshaft angular velocity. The model reflects all essential effects on in-cylinder pressure, while the simulation time was reduced to 6 milliseconds per cycle on a standard PC. This makes it possible to estimate a cylinder-averaged pressure for each cycle up to an engine speed of more than 6000 rpm. The estimated in-cylinder pressure is available with a delay of one engine cycle.

Compressed Natural Gas (CNG) engines have become a promising alternative to classical IC engines because of low pollutant and carbon dioxide emissions. This paper will first briefly summarize these advantages and then concentrate on the modeling and the control of CNG engines. In the modeling part, it will be shown which effects are similar to those observed in gasoline SI engines and what new sub-models are necessary. In the control part, the problem of sudden A/F ratio changes (for instance during the regeneration of NOx trap catalysts) will be considered. In order to avoid excessive NOx engine-out emission in these transients it is important to switch from lean to rich conditions within very few combustion cycles while keeping the engine torque constant (for comfort reasons). The paper presents a model of the most important phenomena associated with those transients and a feedforward control that meets the mentioned requirements.

This paper discusses the possibility of equipping Euro 3 and older vehicles with a universal retrofit kit to reduce the NOX and the PM emissions without producing any secondary effect. Out of several configurations, the optimal setup for EGR and DPF regeneration was evaluated and tested on a passenger car engine testbench. Stationary results showed that with a low pressure EGR it was possible to reduce the NOX emissions by more than 50%, and the filtration efficiency of the DPF was greater than 99%. After various dynamic tests on the test bench to improve the control algorithm, the system was designed to be installed on a garbage truck.