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EU legislation provides for only local CO2 emission-free vehicles to be allowed in individual passenger transport by 2035. In addition, the directive provides for fuels from renewable sources, i.e. defossilised fuels. This development leads to three possible energy sources or forms of energy for use in individual transport. The first possibility is charging with electricity generated from renewable sources, the second possibility is hydrogen generated from renewable sources or blue production path. The third possibility is the use of renewable fuels, also called e-fuels. These fuels are produced from atmospheric CO2 and renewable hydrogen. Possible processes for this are, for example, methanol or Fischer-Tropsch synthesis. The production of these fuels is very energy-intensive and large amounts of renewable electricity are needed.

This paper presents a concept of a high efficiency stoichiometric gasoline engine first published in [1]. The engine is modelled in GT-Power and uses the FKFS UserCylinder. All effects and components that cannot be modelled with these two software modules are estimated by tuning the model parameters to achieve the desired effects. The basic concept of the engine for the model was first published in [2] and [3] by Negüs et al. and includes engine friction reduction, improved turbocharger efficiency, variable compression ratio and variable valve train to allow Miller-Cycle and zero-cam profile cylinder deactivation capability. To further increase efficiency of the engine, measures are introduced to increase knock resistance. The first measure includes a pre-chamber spark plug, which proved to significantly reduce combustion duration [4] and thus the likelihood of knock due to rapid combustion of the fuel mass.

The electrification of vehicle fleets for urban delivery transport is becoming increasingly important due to ever stricter legal requirements and the high public pressure on companies. In this paper, a converted 3.5 t light-duty vehicle with a maximum gross weight of 7.5 t is presented. The vehicle has a serial hybrid electric powertrain with a maximum electric traction power of 150 kW and a 60 kW fuel cell range extender, and uses a 46 kWh battery with 400 V mean voltage level, resulting in a full electric range of 120 km. The electric drive is realized with an induction motor and a lithium-manganese-iron-phosphate (LMFP)-battery as well as a 2-speed gearbox. The fuel cell system has a fuel tank with 100 l volume and 700 bar pressure level, resulting in a total mass of around 4.2 kg of hydrogen. This enables an overall vehicle range of 400 km.

In this paper, a serial/parallel hybrid electric vehicle with a 17 kWh battery and 400 V voltage level is simulated. The vehicle is a C-segment vehicle, which has optimized driving resistances. It also has an external recharge possibility, which enables fully electric driving. The vehicle uses an Otto-engine concept as well as two electric motors. One motor is a permanent magnet synchronous motor and can be used as traction motor or generator, the other one is an induction motor used as main traction motor for the vehicle. The vehicle uses a 2-speed gearbox, where the electric motors are mounted in P2-configuration. To reach optimal results for the fuel consumption, an operating strategy based on the Equivalent Consumption Minimization Strategy (ECMS) is introduced and implemented in the vehicle simulation.

As the late combustion phase in SI engines is of high importance for a further reduction of fuel consumption and especially emissions, the impacts of unburnt mass, located in a small volume with a relatively large surface near the wall and in the top land volume, is of high relevance throughout the range of operation. To investigate and quantify the respective interactions, a state of the art Mercedes-Benz single cylinder research SI-engine was equipped with extensive measurement technology. To detect the axial and radial temperature distribution, several surface thermocouples were applied in two layers around the top land volume. As an additional reference, multiple surface thermocouples in the cylinder head complement the highly dynamic temperature measurements in the boundary zones of the combustion chamber.

For the regeneration of the Lean NOx Trap (LNT) a rich air-to-fuel ratio must be generated. This operation is very critical and has low combustion stability, especially in low load operation. A certain minimum engine load is always required for the regeneration phase. In the Real Driving Emissions this minimum engine load can be undercut over a long period of time. Hence, a reliable regeneration phase is not possible. The aim of these investigations is to extend the engine map range in which regeneration is possible towards lower loads. This is done by means of a variable valve train with second exhaust valve lift, which increases the internal residual gas amount. This in turns increases the temperature at start of combustion in the cylinder. Especially at low load and low combustion stability this leads to a stabilization of the combustion process. This advantage in combustion stability can be used for a reduction of the minimum engine load.

Pilot injection gas engines are commonly used as large stationary engines. Often, the combustion is implemented as a dual-fuel strategy, which allows both mixed and diesel-only operation, based on a diesel engine architecture. The current research project focuses on the application of pilot injection in an engine based on gasoline components of the passenger car segment, which are more cost-effective than diesel components. The investigated strategy does not aim for a diesel-only combustion, hence only small liquid quantities are used for the main purpose of providing a strong, reliable ignition source for the natural gas charge. This approach is mainly driven to provide a reliable alternative to the high spark ignition energies required for high cylinder charge densities. When using such small liquid quantities, a standard common-rail diesel nozzle will apparently not be ideal regarding some general specifications.

For scavenging the combustion chamber during the gas exchange, a temporary positive pressure gradient between the intake and the exhaust is required. On a single-scroll turbocharged four cylinder engine, the positive pressure gradient is not realized by the spatial separation of the exhaust manifold (twin-scroll), but by the use of suitable short exhaust valve opening times. In order to avoid any influence of the following firing cylinder onto the ongoing scavenging process, the valve opening time has to be shorter than 180 °CA. Such a short valve opening time has both, a strong influence on the gas exchange at the low-end torque and at the maximum engine power. This paper analyzes a phenomenon, which occurs due to short exhaust valve opening durations and late valve timings: A repeated compression of the burned cylinder charge after the bottom dead center, referred to as “recompression” in this paper.

This study presents a comparison of different approaches for the simulation of HEV fuel consumption. For this purpose a detailed 1D-CFD model within an HEV drivetrain is compared to a ‘traditional’ map-based combustion engine model as well as different types of simplified engine models which are able to reduce computing time significantly while keeping the model accuracy at a high level. First, a simplified air path model (fast running model) is coupled with a quasi dimensional, predictive combustion model. In a further step of reducing the computation time, an alternative way of modeling the in cylinder processes was evaluated, by replacing the combustion model with a mean value model. For this approach, the most important influencing factors of the 1D-CFD air path model (temperature, pressure, A/F-ratio) are used as input values into neural nets, while the corresponding outputs are in turn used as feedback for the air path model.

More than 20 years after the first presentation of the heat transfer equation according to Bargende [1,2], it is time to introduce some useful additions and enhancements, with respect to new and advanced combustion principles like diesel- and gasoline- homogeneous charge compression ignition (HCCI). In the existing heat transfer equation according to Bargende the calculation of the actual combustion chamber surface area is formulated in accordance with the work of Hohenberg. Hohenberg found experimentally that in the piston top land only about 20-30% of the wall heat flux values from the combustion chamber are transferred to the liner and piston wall. Hohenberg explained this phenomenon that is caused by lower gas temperature and convection level in charge within the piston top land volume. The formulation just adds the existing piston top land surface area multiplied by a specified factor to the surface of the combustion chamber.

Turbocharged SI-DI-engines in combination with a reduction of engine displacement (“Downsizing”) offer the possibility to remarkably reduce the overall fuel consumption. In charged mode it is possible to scavenge fresh unburnt air into the exhaust system if a positive slope during the overlap phase of the gas exchange occurs. The matching of the turbo system in SI-engines always causes a trade-off between low-end torque and high power output. The higher mass flow at low engine speeds of an engine using scavenging allows a partial solution of this trade-off. Thus, higher downsizing grades and fuel consumption reduction potential can be obtained. Through scavenging the global fuel to air ratio deviates from the local in-cylinder fuel to air ratio. It is possible to use a rich in-cylinder fuel to air ratio, whereas the global fuel to air ratio remains stochiometrical. This could be very beneficial to reduce the effect of catalytic aging on the one hand and engine knock on the other hand.

The hybrid power train technology offers various prospects to optimize the engine efficiency in order to minimize the CO₂ emissions of an internal-combustion-engine-powered vehicle. Today different types of hybrid architectures like parallel, serial, power split or through-the-road concepts are commonly known. To achieve lowest fuel consumption the following hybrid electric vehicle drive modes can be used: Start/Stop, pure electric/thermal driving, recuperation of brake energy and the hybrid mode. The high complexity of the interaction between those power sources requires an extensive investigation to determine the optimal configuration of a natural-gas-powered SI engine within a parallel hybrid power train. Therefore, a turbocharged 1.0-liter 3-cylinder CNG engine was analyzed on the test bench. Using an optimized combustion strategy, the engine was operated at stoichiometric and lean air/fuel ratio applying both high- and low-pressure EGR.

The simulation of the combustion process is an essential part of the internal combustion engine development. For simulating whole engine maps quasi-dimensional models in combination with 1-D-flow simulations are widely used. This procedure is beneficial due to short computation times and accurate forecast capability of quasi-dimensional combustion models. For the simulation of homogeneous SI-engines the two-zone entrainment model is usually used, which is based on hemispherical flame propagation. In this work a new approach for the quasi-dimensional calculation of the stratified SI-engine combustion process is proposed, which is based on the two-zone entrainment model. This proven approach was extended with regard to the inhomogeneous air/fuel composition of stratified SI-engines that make a two-zone treatment not sufficient. Therefore, four unburnt zones are defined: a rich zone, a stoichiometrical zone, a lean zone and a remaining air zone.

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.

Natural gas as a fuel for internal combustion engines is a combustion technology showing great promise for the reduction of CO2 and particulate matter. To demonstrate the potential of natural gas direct injection, especially in combination with supercharging, some experimental investigations were carried out using a single-cylinder engine unit with lateral injector position. For this purpose different injection valve nozzles, piston crown geometries as well as operating strategies were investigated. First experimental results show that it is also possible to better support the combustion process by providing a late injection of a part of the fuel, near ignition point, so that the additional induced turbulence can speed up the flame propagation 1 Mixture formation with gaseous fuels due to its low mass density is more critical than in gasoline engines, because even high injection velocities still produce very low fuel penetration.

The research institute FKFS in cooperation with the IVK Universität Stuttgart has recently presented QuickSim, a 3D-CFD-tool, that works integrated into the commercial 3D-CFD-code Star-CD. QuickSim has been developed to cover a vacancy in the market of simulation programs for engine development. The code introduces a new concept in the 3D-CFD-simulation of internal combustion engines (SI-Manifold-Injection and SI-GDI), that drastically reduces the CPU-time in comparison to a conventional 3D-CFD-simulation. QuickSim, as a 3D-CFD-tool, combines the advantages of local resolution of the fluid-dynamical field of internal combustion engines exactly like that provided by traditional 3D-CFD-simulations and the versatility and clearness of the real working-process analysis (WP) and of the full 1D-flow calculations. The CPU-time always remains in an acceptable range (few hours over a full operating cycle for a single-processor computing simulation).