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<div class="section abstract"><div class="htmlview paragraph">For the optimization and extension of operating range of future combustion systems aiming at ultra-low emissions and high efficiency, the control of gas exchange plays a major role. Important parameters for optimization are e.g. volumetric efficiency, residual gas control, in-cylinder charge motion and precise control of the level of homogeneity or inhomogeneity of the charge as required by the particular combustion mode. In addition, advanced operating modes such as Miller or Atkinson cycle or gasoline compression ignition demand a high degree of variability in cam timing. A highly flexible variable valvetrain has been designed for the investigation and development of such new combustion processes. This novel valvetrain is based on a mechanically fully variable actuation concept using two independently rotating cam disks per valve. By this arrangement, new degrees of freedom in the design of the valve opening curve arise. For a single cylinder research engine using a four-valve cylinder head, this valvetrain has been designed in a way so that all four valves can be controlled independently, offering the possibility of e.g. inlet valve phasing combined with a second event on the exhaust. The new valvetrain has been manufactured and tested on a mechanical component test bench. In a “backward” design approach, the valve lift curves and the timing variation range required for the generation of particular variations of in-cylinder charge motion were defined by 3D CFD simulation. On this basis, the layout of the valvetrain components for realization in the research engine was defined. The new valvetrain will be employed for the development of highly efficient low-emission combustion systems on the test bench.</div></div>

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New engine concepts such as Miller, HCCI or highly diluted combustion offer great potential for further optimization of ICEs in terms of fuel economy and pollutant emissions. However, the development of such concepts requires a high degree of variability in the control of gas exchange, characterized by variability in valve spread, maximum valve lift and -ideally independent of these two variables -in valve opening time. In current series variable valvetrains, valve lift and opening duration are usually directly dependent one from the other. In the ideal case, however, engine concepts such as Miller require a fully flexible variation of the closing time of the intake valve while still maintaining the same intake opening time. Here, a methodology for the geometric layout of fully variable valve trains with significantly extended functionalities is presented. In this concept, the control of the valve opening and closing events is distributed to two synchronously rotating cam disks. This geometric separation allows to vary the valve opening duration at constant maximum valve lift by varying the phase offset between the two disks. On the other hand, the geometric properties of the system can be used to vary the maximum valve lift at the constant valve opening and/or valve closing (depending on the layout), as well as for switching additional valve events on or off.The methodology presented here includes the computer-aided and partially automated generation of the characteristic geometric features of the system and the kinematic simulation and evaluation of the concept. By kinematic simulation, various possible resulting valve lift curves can be evaluated and optimized by adapting the geometry and the motion rules. The subsequent investigations on a component test bench serve to assess the newly developed concept with respect to functionality, required drive torque, stiffness and speed capability, thus proving its technical feasibility. 11/13/2020 the kinematic simulation by an analysis of the curvature, as well as by the early integration of gas exchange simulation.