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A newly developed small-sized IES (inductive energy storage) circuit with semiconductor switch at turn-off action is successfully applied to an ignition system of a small gasoline internal combustion engine. This IES circuit can generate repetitive nanosecond pulse discharges. An ignition system using repetitive nanosecond pulse discharges is investigated as an alternative to a conventional spark ignition system. The present study focuses on the extension of the operational limits for lean and diluted combustion using the repetitive nanosecond pulse discharges. First, in order to investigate the flame kernel formation process when the repetitive nanosecond pulse discharges are used, the initial flame kernel is observed using Schlieren photography with a high speed camera. As a result, the flame kernel generated by repetitive pulse discharges is larger than by a conventional ignition system.

In order to extend the HCCI high load operational limit, the effects of the distributions of temperature and fuel concentration on pressure rise rate (dP/dθ) were investigated through theoretical and experimental methods. The Blow-Down Super Charge (BDSC) and the EGR guide parts are employed simultaneously to enhance thermal stratification inside the cylinder. And also, to control the distribution of fuel concentration, direct fuel injection system was used. As a first step, the effect of spatial temperature distribution on maximum pressure rise rate (dP/dθmax) was investigated. The influence of the EGR guide parts on the temperature distribution was investigated using 3-D numerical simulation. Simulation results showed that the temperature difference between high temperature zone and low temperature zone increased by using EGR guide parts together with the BDSC system.

The main objective of the FVV-project “Cylinder Module” was the development of a profoundly modular designed concept for object-oriented modeling of in-cylinder processes of internal combustion engines. It was designed in such a way, that it can either be used as a stand-alone real working-process calculation tool or in tools for whole vehicle simulations. It is possible to run the “Cylinder Module”-code inside the FVV-“GPA”-software for transient vehicle and driving cycle simulations and it is possible to use the graphical user interface “ATMOS” of the “GPA”-project. The code can also be used as a user-subroutine in 1-D-flow simulation codes. Much effort was spent on the requirements of flexibility and expandability in order to be well prepared to cope with the diversity of both today's and future tasks. The code is freely available for members of the German Research Association for Combustion Engines (FVV).

HCCI combustion can realize low NOx and particulate emissions and high thermal efficiency. Therefore, HCCI combustion has a possibility of many kinds of applications, such as an automotive powertrain, general-purpose engine, motorcycle engine and electric generator. However, the operational range using HCCI combustion in terms of speed and load is restricted because the onset of ignition and the heat release rate cannot be controlled directly. For the extension of the operational range using either an external supercharger or a turbocharger is promising. The objective of this research is to investigate the effect of the intake pressure on the HCCI high load limit and HCCI combustion characteristics with blowdown supercharging (BDSC) system. The intake pressure (Pin) and temperature (Tin) were varied as experimental parameters. The intake pressure was swept from 100 kPa (naturally aspirated) to 200 kPa using an external mechanical supercharger.

In order to comply with more and more stringent emission standards, like EU6 which will be mandatory starting in September 2014, GDI engines have to be further optimized particularly in regard of PN emissions. It is generally accepted that the deposition of liquid fuel wall films in the combustion chamber is a significant source of particulate formation in GDI engines. Particularly the wall surface temperature and the temperature drop due to the interaction with liquid fuel spray were identified as important parameters influencing the spray-wall interaction [1]. In order to quantify this temperature drop at combustion chamber surfaces, surface temperature measurements on the piston of a single-cylinder engine were conducted. Therefore, eight fast-response thermocouples were embedded 0.3 μm beneath the piston surface and the signals were transmitted from the moving piston to the data acquisition system via telemetry.

In this study, in order to clarify the mechanism of preignition occurrence in highly boosted SI engine at low speed and high load operating conditions, directphotography of preignition events and light induced fluorescence imaging of lubricant oil droplets during preignition cycles were applied. An endoscope was attached to the cylinder head of the modified production engine. Preigntion events were captured using high-speed video camera through the endoscope. As a result, several types of preignition sources could be found. Preignition caused by glowing particles and deposit fragments could be observed by directphotography. Luminous flame was observed around the piston crevice area during the exhaust stroke of preignition cycles.

The European Union has defined legally binding CO2-fleet targets for new cars until 2030. Therefore, improvement of fuel economy and carbon dioxide emission reduction is becoming one of the most important issues for the car manufacturers. Today’s conventional car powertrain systems are reaching their technical limits and will not be able to meet future CO2 targets without further improvement in combustion efficiency, using low carbon fuels (LCF), and at least mild electrification. This paper demonstrates a highly efficient and performant combustion engine concept with a passive pre-chamber spark plug, operating at stoichiometric conditions and powered with liquefied petroleum gas (LPG). Even from fossil origin, LPG features many advantages such as low carbon/hydrogen ratio, low price and broad availability. In future, it can be produced from renewables and it is in liquid state under relatively low pressures, allowing the use of conventional injection and fuel supply components.

Increasing combustion pressure, low viscosity oils, less oil supply and the increasing stress due to downsizing of internal combustion engines (ICE) lead to higher loads within the bearing. As the mechanical and tribological loads on the piston pin bearings have a direct impact on the service life and function of the overall engine system, it is necessary to develop a robust tribological design approach. Regarding the piston pin bearing of a diesel engine, this study aims to describe the effects of different parameters on a DLC-coated piston pin within the bearing. Therefore, an external engine part test rig, which applies various forces to the connecting rod and measures the torque on a driven pin, is used to carry out validation measurements. The special feature of the test bench is the way the piston is beared. For the first experiments, the piston crown is placed against a plate (plate-bearing); later, this plate-bearing is replaced by a hydrostatic bearing.

Further improvements of internal combustion engines to reduce fuel consumption and to face future legislation constraints are strictly related to the study of mixture formation. The reason for that is the desire to supply the engine with homogeneous charge, towards the direction of a global stoichiometric blend in the combustion chamber. Fuel evaporation and thus mixture quality mostly depend on injector atomization features and charge motion within the cylinder. 3D-CFD simulations offer great potential to study not only injector atomization quality but also the evaporation behavior. Nevertheless coupling optical measurements and simulations for injector analysis is an open discussion because of the large number of influencing parameters and interactions affecting the fuel injection’s reproducibility. For this purpose, detailed numerical investigations are used to describe the injection phenomena.

To increase thermal efficiency of internal combustion engines, dilution combustion systems, such as lean burn and exhaust gas recirculation systems, have been developed. These systems require spark-ignition coils generating large discharge current and discharge energy to achieve stable ignition under diluted mixture conditions. Several studies have clarified that larger discharge current increases spark-channel stretch and decreases the possibility of spark channel blow-off and misfire. However, these investigations do not mention the effect of larger discharge current and energy on the initial combustion period. The purpose of this study was to investigate the relation among dilution ratio, initial-combustion period, and coil specifications to clarify the control factor of the dilution limit.

The industry is working intensively on the precision of thermal management. By using complex thermal management strategies, it is possible to make engine heat distribution more accurate and dynamic, thereby increasing efficiency. Significant efforts are made to improve the cooling efficiency of the engine water jacket by using 3D CFD. As well, 1D simulation plays a significant role in the design and analysis of the cooling system, especially for considering transient behaviour of the engine. In this work, a practice-oriented universal method for creating a 1D water jacket model is presented. The focus is on the discretization strategy of 3D geometry and the calculation of heat transfer using Nusselt correlations. The basis and reference are 3D CFD simulations of the water jacket. Guidelines for the water jacket discretization are proposed. The heat transfer calculation in the 1D-templates is based on Nusselt-correlations (Nu = Nu(Re, Pr)), which are derived from 3D CFD simulations.

In this research, simulation and experimental investigation of H2 emission formation and its influence during the post-oxidation phenomenon were conducted on a turbo-charged spark ignition engine. During the post-oxidation phenomenon phase, rich air-fuel ratio (A/F) is used inside the cylinder. This rich excursion gives rise to the production of H2 emission by various reactions inside the cylinder. It is expected that the generation of this H2 emission can play a key role in the actuation of the post-oxidation and its reaction rate if enough temperature and mixing strength are attained. It is predicted that when rich combustion inside the cylinder will take place, more carbon monoxide (CO)/ Total Hydro Carbon (THC)/ Hydrogen (H2) contents will arrive in the exhaust manifold. This H2 content facilitates in the production of OH radical which contributes to the post-oxidation reaction and in-turn can aid towards increasing the enthalpy.

The authors investigated the reasons of how a preignition occurs in a highly boosted gasoline engine. Based on the authors' experimental results, theoretical investigations on the processes of how a particle of oil or solid comes out into the cylinder and how a preignition occurs from the particle. As a result, many factors, such as the in-cylinder temperature, the pressure, the equivalence ratio and the component of additives in the lubricating oil were found to affect the processes. Especially, CaCO3 included in an oil as an additive may be changed to CaO by heating during the expansion and exhaust strokes. Thereafter, CaO will be converted into CaCO3 again by absorbing CO2 during the intake and compression strokes. As this change is an exothermic reaction, the temperature of CaCO3 particle increases over 1000K of the chemical equilibrium temperature determined by the CO2 partial pressure.

The most significant operation limit prohibiting the further reduction of the CO2 emissions of gasoline engines is the occurrence of knock. Thus, being able to predict the incidence of this phenomenon is of vital importance for the engine process simulation - a tool widely used in the engine development. Common knock models in the 0D/1D simulation are based on the calculation of a pre-reaction state of the unburnt mixture (also called knock integral), which is a simplified approach for modeling the progress of the chemical reactions in the end gas where knock occurs. Simulations of thousands of knocking single working cycles with a model representing the Entrainment model’s unburnt zone were performed using a detailed chemical reaction mechanism. The investigations showed that, at specific boundary conditions, the auto-ignition of the unburnt mixture resulting in knock happens in two stages.

In the competition for the powertrain of the future the internal combustion engine faces tough challenges. Reduced environmental impact, higher mileage, lower cost and new technologies are required in order to maintain its global position both in public and private mobility. For a long time, researchers have been investigating the so called Homogeneous Charge Compression Ignition (HCCI) that promises a higher efficiency due to a rapid combustion - i.e. closer to the ideal thermodynamic Otto cycle - and therefore more work and lower exhaust gas temperatures. Consequently, a rich mixture to cool down the turbocharger under high load may no longer be needed. As the combustion does not have a distinguished flame front it is able to burn very lean mixtures, with the potential of reducing HC and CO emissions. However, until recently, HCCI was considered to be reasonably applicable only at part load operating conditions.

High combustion pressure in combination with high pressure gradient, as they e.g. can be evoked by high efficient combustion systems and e.g. by alternative fuels, acts as broadband excitation force which stimulates natural vibrations of piston, connecting rod and crankshaft during engine operation. Starting from the combustion chamber the assembly of piston, connecting rod and crankshaft and the main bearings represent the system of internal vibration transfer. To generate exact input and validation values for simulation models of structural dynamic and elasto-hydrodynamic coupled multi-body systems, experimental investigations are done. These are carried out on a 1.5-l inline four cylinder Euro 6 Diesel engine. The modal behaviour of the system was examined in detail in simulation and test as a basis for the investigations. In an anechoic test bench airborne and structure-borne noises and combustion pressure are measured to identify the engine´s vibrational behaviour.

For the gasoline engine, the isochoric process is the ideal limit of the ideal processes. During the project, a combustion engine with real isochoric boundary conditions is built. A “resting time” of the piston for several degrees crank angle in the top dead center (TDC) can be realized with a special crank drive. This crank drive consists of two crankshafts with different strokes, which are combined. The two crankshafts rotate with a ratio of two to one in opposite directions. The total stroke corresponds to the amount of the first crankshaft, so it is possible to investigate different strokes of the second crankshaft in the same crankcase. Different “resting times” can be achieved by different strokes of the second crankshaft. A specific combination of both crankshafts make a stroke possible which corresponds to that of a conventional combustion engine.

Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended slightly by low temperature plasma ignition while the power supply’s performance with steep voltage rising with time (dV/dt), showed higher peak value of the rate of heat release and better indicated thermal efficiency. In this study, basic study of low temperature plasma ignition system was carried out to find out the reason of combustion enhancement. Moreover, the durability test of low temperature plasma plug was performed to check the wear resistance.

On the way to emission-free mobility, future fuels must be CO2 neutral. To achieve this, synthetic fuels are being developed. In order to better assess the effects of the new fuels on the engine process, simulation models are being developed that reproduce the chemical and physical properties of these fuels. In this paper, the fuel DMC+ is examined. DMC+ (a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo) mainly, characterized by the lack of C-C Bonds and high oxygen content) offers advantages with regard to evaporation heat, demand of oxygen and knock resistance. Furthermore, its combustion is almost particle free. With the aid of modern 0D/1D simulation methods, an assessment of the potential of DMC+ can be made. It is shown that the simulative conversion of a state-of-the-art gasoline engine to DMC+ fuel offers advantages in terms of efficiency in many operating points even if the engine design is not altered.

As a result of the R&D focus being shifted from internal combustion engines to electrified powertrains, resources for the development of internal combustion engines are restricted more and more. With that, the importance of highly efficient engine development tools is increased. In this context, 0D/1D engine simulation offers the advantage of low computational effort and fast engine model set-up. To ensure a high predictive ability of the engine simulation, a reliable burn rate model is needed. Considering the increasing interest in alternative fuels, the aspect of predicting the fuel influence on combustion is of special importance. To reach these targets, the change of engine combustion characteristics with changing fuels and changing air-fuel-ratios were investigated systematically in a first step. For this purpose, engine test bed data were compared with expected fuel-dependent flame wrinkling trends based on Markstein/Lewis number theory.