Upcoming emission limits such as Euro VII will make it necessary to further reduce the NO x emission level of internal combustion engines while stricter CO 2 limits demand lower fuel consumption. Early closing of the intake valves (Miller timing) leads to reduced combustion temperatures due to lower effective compression ratio, and therefore lower formation and emission of nitrogen oxides. Miller timing is frequently used in gasoline engines, while in Diesel engines it competes with exhaust gas recirculation (EGR). When both measures are applied simultaneously, this may lead to increased emission of soot using standard Diesel fuel, as combustion temperature and oxygen content of the charge become too low. This work shows the investigation of different intake valve timings on an externally supercharged single-cylinder heavy-duty Diesel engine, stationary operated with hydrogenated vegetable oil (HVO), oxymethylene ether (OME), and standard Diesel fuel (DF). The synthetic fuels have a higher cetane number than DF, which supports ignition at lower temperatures. Moreover, OME has a soot-free combustion, which allows an extension of the operating limits without increased emissions. The results show that especially with Miller timing a high-performance turbocharging system is crucial, since higher boost pressure is required to compensate for the filling losses due to the earlier intake closing. The application of a high EGR rate is limited in this case, leading to a trade-off between Miller timing and EGR. All fuels show a reduction in nitrogen oxides of up to 40% with an improved efficiency of more than 3% at a typical road-load point. Measures to reduce ignition delay were found to be necessary, especially for DF. For OME, increased soot formation does not occur when combining Miller timing with low rail pressure, reduced boost pressure or EGR, which promotes simultaneous application of the measures resulting in minimized emissions of nitrogen oxides.
-------------------------------------------------------------------------------------------------------- This manuscript, according to publishing restrictions, is available only as a summary of the following parts: introduction, motivation, conclusions and outlook. Thank you for your understanding. -------------------------------------------------------------------------------------------------------- Motorsports has always been an optimal environment for innovative solutions. Highly motivated by competition, the solutions can be tested, implemented and validated within minimal development time, thus establishing Motorsports as a genuine innovation driver. But the way how to achieve gains in engine performance has remarkably changed in the last years. Today, due to different regulations – e.g. the introduction of an air restrictor in the World Rally Championship or the limitation of the fuel consumption in the Formula 1 World Championship –, engine power can be raised only by increasing engine efficiency. Accordingly, the development targets in Motorsports have changed. Thus, new solutions may become increasingly interesting for mass production engines in the future, too.
Losses in conventional automotive and hybrid powertrains can be reduced on both the engine and the transmission side. On the engine side for instance, cylinder deactivation can reduce the fuel consumption of an internal combustion engine (ICE). Friction losses of the non-firing cylinders still remain. Therefore, ICEs which are mechanically divided into two individual engines promise an even higher potential in terms of fuel economy. The objective of this paper is to present the concept of a clutch unit that is able to connect two ICEs. Thus, it is possible to create an innovative, cost- and fuel-efficient powertrain architecture for automotive applications: This is the concept of the Split-Crankshaft Engine (SCE). In a first step, this powertrain architecture and its particular requirements will be discussed. In a second step, a selection of proposals for crankshaft connecting clutches that have been presented in recent years will be detailed. The clutch concept of the SCE will be depicted in a third step: a switchable, electromechanically actuated clutch unit for load-dependent activation of the secondary engine. In order to reduce costs and weight as well as to minimize activation durations, the secondary engine will be started through a friction clutch. When the two sub-motors are synchronized, a form-locking, second clutch will be engaged in order to ensure the connection of both engines at high torque.
