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A model for the calculation of heat release in direct injection Diesel engines is presented. It needs only one engine-specific experimental parameter. In the form the model is presented here it is limited to the medium and upper load range, where Diesel combustion is mainly mixing controlled. The development of the model is based on data from medium speed engines. The applicability to automotive engines is shown in some examples. The model is based on the theory of single phase turbulent jets. Starting from the balance of momentum and fuel mass flow the stationary part of the jet can be calculated. The propagation of the front of the unsteady jet is determined from a continuity consideration. Heat release is calculated based on the assumptions of the Simple Chemically Reacting System (SCRS). Fuel that is mixed with air is assumed to be burnt instantaneously.

The current level of mean effective pressure (mep) of automotive diesel engines is 20 to 30 bar. Maximum pressure (pmax) is about 180 to 200 bar. In special applications even higher figures have been achieved in the past. This led the authors to investigate what can be expected when operating at much higher pressures. In a theoretical study the mep of a passenger car engine was increased up to 80 bar. A zero-dimensional cycle simulation program was used for the calculations. Rate of heat release, valve timing and mechanical efficiency were kept constant. Several strategies concerning turbocharging and thermal loading were investigated. Some results for mep = 80 bar: - The specific fuel oil consumption is reduced by some 5%, if certain prerequisites are given. - Further reductions are possible depending on mechanical efficiency, which was set constant in this study. - Charge air pressure increases to approximately 10 bar.

The supercharging of small-displacement gasoline engines requires high pressure ratios combined with a wide range of air flow rate. To resolve this conflict, two-stage turbo charging with two turbochargers or the combination of a turbocharger and a mechanical compressor is used. But this is associated with an increase in complexity. The highest potential for avoiding a multi-stage system is provided by the systematic modification of the turbo-machinery operating maps, e.g. on the turbine side by using variable turbine geometry. An additional promising approach is the implementation on the compressor side of a variable guide vane. The shape of the compressor map is directly affected and the requirements for highly boosted engines can thus be fulfilled. The present paper provides an assessment of the potential of a variable compressor in combination with a variable geometry turbine (VTG) and additional wastegate on a small-volume gasoline engine.

In hybrid electric vehicles the combination of diesel engine and electric motor obviously provides lowest fuel consumption. However, compared with the Otto hybrid system, there are relatively high NOx and particulate matter emissions. This paper describes investigations of various strategies for a significant reduction of exhaust gas emissions in diesel hybrid electric vehicles. By reducing the dynamic operation of the combustion engine by supplementing the engine torque demand with an electric motor and limiting the maximum engine torque, the NOx emissions could be reduced by more than 30% and the particulate matter emissions by more than 20%, without influencing the fuel consumption compared to hybrid electric vehicles with conventional operation strategy.