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We have performed simulations and experiments to characterize the mixture formation in spray-guided direct injected spark ignition (DISI) gasoline engines and to help to understand features of the combustion process, which are characteristic for this engine concept. The 3-D computations are based on the KIVA 3 code, in which basic submodels of spray processes have been systematically modified at ETH during the last years. In this study, the break-up model for the hollow-cone spray typical for DISI engines has been validated through an extended comparison with both shadowgraphs and Mie-scattering results in a high-pressure-high-temperature, constant volume combustion cell at ambient conditions relevant for DISI operation, with and without significant droplet evaporation. Computational results in a single-cylinder research engine have been then obtained at a given engine speed for varying load (fuel mass per stroke), swirl and fuel injection pressure.

The physical behavior of the combustion process in a jet-guided direct injection spark ignition engine has been investigated with three different measurement techniques. These are flame visualization by use of endoscopy, ion-current sensing at 16 different locations in the combustion chamber and the estimation of the flame temperature as well as soot concentration based on multi-wavelength-pyrometry. The results of all these measurement techniques are in good agreement between each other and give a coherent picture of the physical behavior of the combustion process and make it possible to characterize the main influence parameters on combustion. This serves as a basis for validation and improvement of simulation tools for the engine thermodynamics and combustion.

The continuous pursuit of more efficient diesel engines and the stricter emission regulations with the introduction of the Real Driving Emissions test (RDE) necessitate further investigations of heating strategies and their suitability in terms of series production. Under these circumstances heating strategies of a variable valve train for a single-cylinder research diesel engine have been first simulated and then experimentally tested at the Institute of Internal Combustion Engines of the Karlsruhe Institute of Technology (KIT). By combining statistical experimental design (DoE) and 1-D gas exchange simulations, empirical DoE models for the design of suitable camshaft configurations have been established. After having performed a potential assessment, the most favorable configurations were manufactured and subsequently tested.

Due to the prevalent fuel economy, research on electric hybrid vehicles (HEVs) has attracted recently widespread attention. However, most researches were focused on electrification, neglecting the crucial role of internal combustion engines (ICEs) in reducing fuel consumption. Holding the opinion that ICEs can contribute more in developing fuel economic vehicles, we present in this paper a new HEV topology with two ICEs - Dualhybrid. Two separate traction units, conventional drivetrain with ICE1at front axle and electric hybrid drivetrain with ICE2+battery at rear axle constitute the powertrain of this new HEV concept. One dimensional simulation with sub-models built upon different modelling methods is implemented. Energy management of Dualhybrid is identified with a rule-based control strategy. Base and Fullhybrid model were built as references and a comparative simulation among the three models was conducted.

The fuel economic and emission performance of an innovative electric hybrid vehicle (HEV), Dualhybrid, with two internal combustion engines (ICEs) under cold start conditions was studied. Sub-models including powertrain, lubrication and cooling system as well as exhaust system were built and integrated into the models of Dualhybrid and two other reference models: Base model and Fullhybrid model. Coupled lubrication and the exhaust systems of the two ICEs are proposed. The effect of the combination of oil heating and electric heating on the fuel consumption of Dualhybrid was investigated. The results show that the coupled lubricating system of Dualhybrid is beneficial to improve the fuel economy in cold start. The method of hybrid heating can provide a sufficient heating power of the cabin in the initial stage of cold start without declining the fuel economic performance significantly.

The investigation of transient engine operation plays a key role of the future challenges for individual mobility in terms of real driving emissions (RDE). A fundamental investigation of the transient engine operation requires the simultaneous application of measurement technologies for an integrated study of mixture formation, combustion process and emission formation. The major prerequisite is the combustion cycle and crank angle resolved analysis of the process for at least several individual consecutive combustion cycles during transient operation. The investigations are performed with a multi cylinder DISI engine at an Engine-in-the-Loop test bench, able to operate the engine in driving cycles as well as within target profiles (e.g. speed and torque profiles). The research project describes the methodology of analyzing elementary transient operational phases, (e.g. different variants of load steps).

The gradual global tightening of emission legislation for particulate matter emissions requires the development of new gasoline engine exhaust aftertreatment systems. For this reason, the development of gasoline direct injection engines aims at the reduction of particulate emissions by application of a Gasoline Particulate Filter (GPF). The regeneration temperature of GPF depend on soot reactivity towards oxidation and therefore on particle properties. In this study, the soot reactivity is correlated with nanostructural characteristics of primary gasoline particles as a function of specific engine injection parameters. The investigations on particle emissions were carried out on a turbocharged 4-cylinder GDI-engine that allows the variation of injection parameters. The emitted engine soot particles have been in-situ characterized towards their number and size distribution using an engine exhaust particle sizer (EEPS).

E-fuels are proven to be a major contributing factor to reduce CO2 emissions in internal combustion engines. In gasoline engines, C1 oxygenate are seen as critical to reach CO2 and emission reduction goals. Their properties affect the fuel injection characteristics and thus the fuel mixture formation and combustion emissions. To exploit the full potential of e-fuels, the detailed knowledge of their spray characteristic is necessary. The correlation between the fuel content of C1 oxygenates and particulate emissions do not appear to be linear. To understand this correlation, the spray characteristics have to be investigated in detail. The reduced stoichiometric air requirement leads to an increase of the injected fuel mass, which has to evaporate. This can lead to a changed fuel film interaction within the combustion chamber walls and therefore a change of particle formation.

In this work, heat loss was investigated in homogeneous and stratified DI-SI operation mode in a single cylinder research engine. Several thermocouples were adapted to the combustion chamber surfaces. The crank angle resolved temperature oscillations at the cylinder head and piston surface could thereby be measured in homogeneous and stratified operation mode. A grasshopper linkage was designed and adapted to the engine, to transfer the piston signals to the data acquisition device. The design of the experimental apparatus is described briefly. For both operation modes the average steady-state temperatures of the combustion chamber surfaces were compared. The temperature distribution along the individual sensor positions at the cylinder head and piston surface are shown. Furthermore, the curves of the crank angle resolved temperature oscillations in stratified and homogeneous operation mode were compared.

The need for carbon-neutral transportation solutions has never been more pronounced. With the continually expanding volume of goods in transit, innovative and dependable powertrain concepts for freight transport are imperative. The green hydrogen-powered internal combustion engine presents an appealing option for integrating a reliable, non-fossil fuel powertrain into commercial vehicles. This study focuses on the adaptation of a single-cylinder diesel engine with a displacement of 2116 cm3 to facilitate hydrogen combustion. The engine, characterized by low levels of swirl and tumble, underwent modifications, including the integration of a conventional central spark plug, a custom-designed piston featuring a reduced compression ratio of 9.5, and a low-pressure hydrogen direct injection system. Operating the injection system at 25 bar hydrogen pressure, the resulting jet profiles were varied by employing jet forming caps affixed directly to the injector nozzle.

Thermal management has always played a significant role in reducing emissions and improving the fuel efficiency of the internal combustion engines (ICEs). With a momentous influence on the thermal behavior of the engines, the cooling system has a considerable impact on ICE performance. In this scenario, a method based on artificial neural network (ANN) of the cooling system was proposed in this work. Specific modeling methods were adopted for the various operating conditions and flow circuits of the cooling system. To describe these varied dynamic characteristics, four ANN sub-models were established to simulate the system at different temperature stages. As a closed-loop system, the temperature of the cooling system can be regarded as a result of all the experienced operating points. Therefore, integral parameters describing the trajectory of the system were selected as the input of the ANNs.

Despite the known benefits of direct injection (DI) spark ignition (SI) engines, port fuel injection (PFI) remains a highly relevant injection concept, especially for cost-sensitive market segments. Since particulate number (PN) emissions limits can be expected also for PFI SI engines in future emission legislations, it is necessary to understand the soot formation mechanisms and possible countermeasures. Several experimental studies demonstrated an advantage for PFI SI engines in terms of PN emissions compared to DI. In this paper an extended focus on higher engine loads for future test cycles or real driving emissions testing (RDE) is applied. The combination of operating parameter studies and optical analysis by high-speed video endoscopy on a four-cylinder turbocharged SI engine allows for a profound understanding of relevant soot formation mechanisms.

The start of combustion in a spark-ignited engine is highly dependent upon the conditions between the two spark plug electrodes at ignition. In addition to the air-to-fuel ratio in this gap, the gas flow is seen as most critical. In a combustion engine with a standard spark plug that protrudes into the combustion chamber, this gas flow is mainly dependent upon the tumble, swirl, or squish that is developed by the cylinder head and the piston movement. However, the air movement in the pre-chamber depends on the orientation of the orifices towards the main combustion chamber (MCC). This implies a less complex manipulation of local velocity in the electrode gap. This paper focuses on the effect of different pre-chamber designs on spark deflection by the inflowing gas. Therefore, a test rig was developed using the spark plug thread in the cylinder head of a motored engine.

A raise of efficiency is the strongest selling point concerning the total cost of ownership (TCO), especially for commercial vehicles (CV). Accompanied by legislations, with contradictive development demands, satisfying solutions have to be found. The analysis of energy losses in modern engines shows three influencing parameters. Wall heat transfer (WHT) losses are awarded with the highest optimization potential. Critical for the occurrence of these losses is the WHT, which can be described by representing coefficients. To reduce WHT accompanying losses a decrease of energy transfer between combustion gas and combustion chamber wall is necessary. A measurement of heat fluxes is necessary to determine the WHT relations of the combustion chamber in an engine. As this has not been done for a Heavy-Duty (HD) engine, with peak pressures up to 250 bar, an increased in-cylinder turbulence and high exhaust gas recirculation (EGR)-rates before, it is presented in the following.

In this paper experimental results of a medium duty single cylinder research engine with spark ignition are presented. The engine was operated with stoichiometric natural gas combustion and additional charge dilution by means of external and cooled exhaust gas recirculation (EGR). The first part of this work considers the benefits of cooled EGR on thermo-mechanical stress of the engine including exhaust gas temperature, cylinder head temperature, and knock behaviour. This is followed by the analysis of the influence of cooled EGR on the heat release rate. In this context the impact of fuel gas composition is also under investigation. The influence of increasing EGR on fuel efficiency, which is caused by a changed combustion process due to higher fractions of inert gases, is shown in this section. By application of different pistons a relationship between the piston bowl geometry and the flame propagation has been demonstrated.

The subject of this paper is the reduction of the particle number emissions of a gasoline DI engine at high engine load (1.4 MPa IMEP). To reduce the particle number emissions, several parameters are investigated: the large scale charge motion (baseline configuration, tumble and swirl) can be varied at the single cylinder engine by using inlays in the intake port. The amount of residual gas can be influenced by the exhaust backpressure. By using a throttle valve, the exhaust backpressure can be set equal to the intake pressure and hence simulate a turbocharger's turbine in the exhaust system or the throttle valve can be wide open and thus simulate an engine using a supercharger. Additionally, higher fuel injection pressure can help to enhance mixture formation and thus decrease particulate formation. Therefore, a solenoid injector with a maximum pressure of 30 MPa is used in this work.