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In this paper, a simulation approach is introduced which takes into account all relevant heat sources and sinks in the combustion engine and in the engine compartment. With this approach, it is possible to calculate the appearing power flow and enthalpy flow as well as the component temperatures. Therefore, the complex thermodynamic and friction processes in the engine are described as simple as possible; the complete system can still be described reliably within certain limits, and the effects of different thermal optimization measures can be shown. It is an essential point for the modeling that only two integral quantities are necessary (the high pressure efficiency and the high pressure wall heat loss) for the complete combustion model.

For real working-process simulations it is essential to know the caloric properties of the working fluid, such as the specific enthalpy and the real gas constant. When using standard-fuels there are established models which describe the caloric variables as functions of temperature, air/fuel-ratio and pressure. In each case, these models were developed for a certain fuel composition and their application to alternative fuels is limited or not valid at all. Thus, an approach is discussed, which is valid for any user-defined fuel. This work presents the formulations for the caloric modelling of burnt gas and fuel vapor, respectively. An algorithm is introduced that provides a very fast calculation of the chemical equilibrium condition of burnt gas. The influence of the equilibrium coefficients and the fuel composition on the chemical equilibrium composition is discussed.

A quasidimensional combustion model for homogenous spark ignition combustion processes with variable valve timing is proposed which is able to compute a complete engine map in advance and can be calibrated rapidly. In the engine map there are not only load and speed that do change considerably, the residual gas mass does so as well. This paper exposes the models' potential and limits by both simulation and measurement on two different engines with port-injection. Methods for model adjustment as well as the implementation in the commercial one-dimensional flow simulation software “GT-Power” will be shown. Furthermore a knock control is introduced and resulting errors are discussed.

This paper focuses onto mixture formation issues of the Directstart of a gasoline direct injection engine. Regarding the starterless Directstart, i.e. an engine start through targeted injection and ignition timing without the help of an electrical starter, engine tests show that there exists a large room for improvements by attending the mixture formation of the first combustion. The conditions for the first combustion are very unusual: ambient pressure, nearly the same fuel, engine and charge temperature, no piston movement and only spray induced turbulence. Furthermore, engine tests show that the mixture formation changes with the engine temperature. This paper analyzes the mixture formation of the first combustion for different engine conditions by means of engine measurements and both optical measurements in a spray chamber and simulations performed by the fast response 3D-CFD-Tool QuickSim of IVK/FKFS.

In this work the formation and the evolution of the fuel spray emerging from a hollow-cone swirl injector were investigated. The first aim of the work was to set up a tool for fuel spray simulation in a CFD analysis that can offer a reasonable accuracy with no significant increment in the computational time. The analysis started from a theoretical formulation of the fuel flow inside the injector, based on the potential theory, obtaining an injector model which allows the calculation of the main spray characteristics usually required by the CFD analysis (i.e. droplet velocity, fuel film thickness, droplet size distribution). These parameters can be obtained only from spray cone angle and mass flow rate, which are the data commonly provided by injector manufacturers. Furthermore, a phenomenological approach was also presented, in order to properly simulate in CFD analysis the spray tip penetration in the dense spray zone, without requiring an increase of the spatial grid resolution.

The principle strategy, the development emphasis, and the investigation parameters of a DI gasoline engine are discussed. Several different combustion systems are briefly described and one system where the spark plug is located near the fuel injector is investigated. In addition, the influence of different operating parameters are studied. Some reasons for the improvement in the efficiency of a DI gasoline engine are shown with the help of thermodynamic analysis and simulation calculations. These show that at a constant operating point (engine speed = 2000 rpm, bmep = 2 bar) there is a reduction of the fuel consumption of 23% at unthrottled conditions in comparison to the homogeneous stoichiometric operation. In particular, the reduction of the pumping and heat losses and the reduction of the exhaust gas energy are responsible for this fuel consumption reduction.