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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.

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.

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.

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.