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The research and development of variable valve train concepts increase the DOF of their functionalities. Beginning with discrete switching between two valve timings (Alfa Romeo: “Variatore di Fase Dinamico”), also the discrete variability of the valve lift (Honda: “VTEC”) was introduced in the 1980s. Increasing the variability to continuous camshaft phasing in the 1990s (Porsche: “VarioCam”) and lift control in the 2000s (BMW: “VALVETRONIC”) an almost fully variable electrohydraulic valve train concept for the inlet valves has been introduced (Alfa Romeo: “MultAir”). Regardless of whether in future a fully variable free valve concept will be introduced or not, a quantitative characterization of the variability of valve trains seems to be necessary to compare different valve train designs with each other. More, the operational parameter of electromagnetic (e.g. voltage, current) or electrohydraulic (e.g. hydraulic pressure, switching times) can be characterized with such a quantity.

Due to the short mixture formation times in the direct injection of modern gasoline engines, there is an increase in the emission of undesirable particle emissions. It is well known that particulate mass is not very high compared to diesel engines. However, the harmful small particles are a problem, which has led to the legislator limiting the number of particle emissions. As a result of previous studies with a portable emission measurement system (PEMS) of raw cleaned exhaust gas, the particle number (PN) of the sampling point after the catalyst was higher than before the catalyst at the same process parameters and engine operating points. Based on this reproducible phenomenon, several theories were proposed.

The paper first includes the main objective and boundary conditions for design and simulation of a multi fuel gas mixture system of a Wankel rotary engine. New regenerative fuels are more and more important for use in automotive propulsion and stationary applications of combustion engines. Due to the special design and operation of rotary engines there are opportunities for running these engines in future electric and hybrid applications with new designed liquids and gaseous fuels based on regenerative energy sources. Nevertheless, rotary engines have advantages in avoidance of preignition and detonation especially when using gaseous fuels with a higher percentage of hydrogen. The focus is on basic research and analyses of main physical and thermodynamic properties of separate lean burn gases (lower calorific value, mixed calorific value, AFR) and their effects on fuel mixing and engine performance.

Combustion concepts for future SI engines try to meet CO2-emission legislation all over the world. One approach is to minimize the gas exchange losses using a fully variable valvetrain on the engine’s intake side, or the reduction of the throttled part load operation either by downsizing concepts in connection with turbochargers or by deactivation of cylinders. An interesting strategy is the utilization of proven CVVL-components to find effective controlling methods for the combustion process of turbocharged direct injection SI engines. The new approach of using a fully variable valvetrain on the exhaust side improves the controlling of both residual gases and combustion processes. A camless valvetrain provides the opportunity to control air mass flow and combustion process for every single cylinder of a multi-cylinder engine to achieve best performance in fuel efficiency at part load operation combined with enhanced transient response of turbocharged engines.

The global development of oil prices and ongoing discussions with regard to meet future CO2-emission commitments necessitate new technologies and concepts in individual motor car traffic. While hybridization and electrification become more and more important on a small scale, the improvement in efficiency of conventional drive, especially in respect of SI engines, currently offers the highest potential in reducing fuel consumption and exhaust emissions. Thereby valve trains play a key role in the optimization of SI engines e. g. in connection with technologies and processes such as in-cylinder air-fuel mixing, combustion, HCCI, gas exchange, lean operation etc. Modern valve train systems entering mass production are despite of the fact of being called fully variable, yet cam-actuated systems. Thus variability and application are limited compared to direct (non-cam-actuated) engine control systems.