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The introduction of real driving emissions cycles and increasingly restrictive emissions regulations force the automotive industry to develop new and more efficient solutions for emission reductions. In particular, the cold start and catalyst heating conditions are crucial for modern cars because is when most of the emissions are produced. One interesting strategy to reduce the time required for catalyst heating is post-oxidation. It consists in operating the engine with a rich in-cylinder mixture and completing the oxidation of fuel inside the exhaust manifold. The result is an increase in temperature and enthalpy of the gases in the exhaust, therefore heating the three-way-catalyst. The following investigation focuses on the implementation of post-oxidation by means of scavenging in a four-cylinder, turbocharged, direct injection spark ignition engine. The investigation is based on detailed measurements that are carried out at the test-bench.

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.

Intensified emission regulations as well as consumption demands lead to an increasing significance of unburned hydrocarbon (UHC) emissions for diesel engines. On the one hand, the quantity of hydrocarbon (HC) raw emissions is important for emission predictions as well as for the exhaust after treatment. On the other hand, HC emissions are also important for predicting combustion efficiency and thus fuel consumption, since a part of unreleased chemical energy of the fuel is still bound in the HC molecules. Due to these reasons, a simulation model for predicting HC raw emissions was developed for diesel engines based on a phenomenological two-zone model. The HC model takes three main sources of HC emissions of diesel engines into account: Firstly, it contains a sub-model that describes the fuel dribble out of the injector after the end of injection. Secondly, HC emissions from cold peripheral zones near cylinder walls are determined in another sub-model.

In order to optimize spray layouts of commonly used high-pressure injectors for gasoline direct injection (GDI) engines featuring multi-hole valve seats, a detailed understanding of the cause-effect relation between inner spray hole geometries and inner flow conditions, initializing the process of internal mixture formation, is needed. Therefore, a novel measurement setup, capable of determining spray hole individual mass flow rates, is introduced and discussed. To prove its feasibility, a 2-hole configuration is chosen. The injected fuel quantities are separated mechanically and guided to separate pressure tight measurement chambers. Each measurement chamber allows for time resolved mass flow rate measurements based on the HDA measurement principle (German: “Hydraulisches Druck-Anstiegsverfahren”).

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.

As a consequence of reduced fuel consumption, direct injection gasoline engines have already prevailed against port fuel injection. However, in-cylinder fuel homogenization strongly depends on charge motion and injection strategies and can be challenging due to the reduced available time for mixture formation. An insufficient homogenization has generally a negative impact on the combustion and therefore also on efficiency and emissions. In order to reach the targets of the intensified CO2 emission reduction, further increase in efficiency of SI engines is essential. In this connection, 0D/1D simulation is a fundamental tool due to its application area in an early stage of development and its relatively low computational costs. Certainly, inhomogeneities are still not considered in quasi dimensional combustion models because the prediction of mixture formation is not included in the state of the art 0D/1D simulation.

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.

Today, mechanical systems such as the piston groups of internal combustion engines are simulated using Multiple Body-System (MBS) - approaches. However, the use of these models is restricted to a few problems as their adaptability is limited. The simulation of mechanical systems only by means of finite elements shows great promise for the future. In order to consider lubrication effects between two touching bodies of a mechanical system, a hydrodynamic contact algorithm (HCA) for finite element (FE) applications was developed. This paper discusses the technical background and first results for the simulation of a piston group using this new approach.

The real cycle simulation is an important tool to predict the engine efficiency. To evaluate Extended Expansion SI-engines with a multi-link cranktrain, the challenge is to consider all concept specific effects as best as possible by using appropriate submodels. Due to the multi-link cranktrain, the choice of a suitable heat transfer model is of great importance since the cranktrain kinematics is changed. Therefore, the usage of the mean piston speed to calculate a heat-transfer-related velocity for heat transfer equations is not sufficient. The heat transfer equation according to Bargende combines for its calculation the actual piston speed with a simplified k-ε model. In this paper it is assessed, whether the Bargende model is valid for Extended Expansion engines. Therefore a single-cylinder engine is equipped with fast-response surface-thermocouples in the cylinder head. The surface heat flux is calculated by solving the unsteady heat conduction equation.

2-dimensional time resolved (200 frames/s) flow field measurements have been made in a transparent SI square piston engine using a movie version of particle image velocimetry (PIV). To this end the beam of a copper vapor laser was formed into a light sheet and was double pulsed with a pulse separation of 50 μs at a repetition rate of 200 Hz. A rotating drum camera was used to record the Mie-scattered signals from seeding particles. The circumferential velocity of the drum of the camera causes an image shifting of the two exposures taken with a double pulse. By proper adaption of drum and engine speed, a series of up to 70 double pulsed images per individual engine cycle may be recorded on film. This film data may be evaluated uniquely with respect to both magnitude and direction of individual flow vectors in the flow field.

The fluorescence characteristics of different carbonyl compounds were investigated in a pressurized bomb using an excimer laser (308 nm) for excitation. The partial pressure of the carbonyl compounds and air was varied between 0 - saturation pressure and 0 - 5 bar, respectively. The fluorescence signal of different ketones increased almost linearly with vapour pressure. It was found to be almost independent of air pressure indicating only a weak quenching influence of oxygen. Ethylmethylketone (EMK) has a boiling temperature and vapour pressure similar to gasoline. Therefore, the applicability of EMK for measuring 2-D fuel distributions in a combustion chamber was tested in a transparent SI square piston engine. EMK was injected into the intake manifold by a conventional injector for studying the fuel/air mixing during the intake and compression stroke at 1.000 rpm. From the 2-D fluorescence signals 2-D air/fuel ratios were calculated using calibration data from bomb experiments.

The influence of internal mixture formation oil hydrogen combustion in a SI engine was investigated using high speed Schlieren photography. To this end a computer controlled high pressure injection system for direct injection of gaseous hydrogen was developed. The injection system for hydrogen direct injection consists of an electronic control unit, a solenoid valve and a purpose developed injector. The timing and the duration of the hydrogen injection are controlled by an electronic unit. The fuel-air ratio was varied by adjusting the opening time of the solenoid valve. The hydrogen was fed into the combustion chamber of the engine with a pressure of 6.0 MPa. With this injection system and injection pressure it, is possible to inject the hydrogen into the combustion chamber of the engine even during hydrogen combustion. In order to compare the results of internal mixture formation, experiments with external mixture formation were also performed.

A real-time 3-dimensional, nonlinear simulator for the dynamical behaviour of trucks has been developed. The simulator serves as industrial test stand for examinations on different electronic control systems. This paper describes the challenging task of developing a powerful real-time simulator with hardware coupling based on parallel transputer systems. The integration of an anti-lock braking system (ABS) as hardware-in-the-loop by means of an interface electronic device is described. The interface electronics provide the coupling of the electronic control unit (ECU). The special demands on the signals and the resulting concept for the developed electronic interface are specified. Some results from dynamic braking simulations show the quality of the simulator.

An important cornerstone of our society is the individual mobility which, today, chiefly can only be offered by the automobile. However, in the industrial countries the car at the same time is exposed to harsh criticism as far as environmental pollution is discussed. Goal of this presentation is to show a scientific method by means of which environmental loads during manufacture, use and utilization/disposal of whole systems - in this special case vehicles - can be quantified and optimized. In order to do this, the instrument of life cycle analysis of parts and processes is used and in the same way the scientific method is developed beyond the level of literature. Due to these modifications the results are only useful if the boundary conditions are mentioned in detail. Considerations on the system such as the examination of an automobile require a method extended by essential criteria due to its complexity.

A two-dimensional technique for the quantitative determination of the fuel-air ratio in hydrogen fuelled engines has been developed. The technique is based on the spontaneous Raman scattering of the hydrogen molecules (Stokes Q-branch) and the simultaneous measurement of the pressure inside the combustion chamber. From these data the local partial pressure of the hydrogen and, therefore, the fuel-air ratio can be calculated. This method was applied in a single cylinder direct injection research engine in order to prove the applicability of this technique under real engine conditions. The measurements inside the side chamber of the engine show a fast mixing process of the compressed air and the injected hydrogen (6 MPa injection pressure) independent of the injection timing.

Quantitative Laser-Induced Incandescence (LII) has been applied to investigate the soot formation in a combusting Diesel jet for various conditions. For the quantification of the LII signal the local soot volume fraction of a diffusion flame burner was measured using laser beam extinction. These data were used for the calibration of the LII signal. The investigation of the soot formation in a combusting Diesel jet was performed in a high pressure, high temperature combustion chamber with optical access. A wide range of pressure (up to 10 MPa) and temperature (up to 1,500 K) conditions could be covered using a hydrogen precombustion, which is initiated inside the chamber before fuel injection. The influence of different gas atmospheres have been investigated by varying the gas composition (H2, O2 and N2) inside the chamber.

Knocking is one of today’s main limitations in the ongoing efforts to increase efficiency and reduce emissions of spark-ignition engines. Especially for synthetic fuels or any alternative fuel type in general with a much steeper increase of the knock frequency at the KLSA, such as hydrogen, precise knock prediction is crucial to exploit their full potential. This paper therefore proposes a post-processing tool enabling further investigations to continuously gain better understanding of the knocking phenomenon. In this context, evaluation of local auto-ignitions preceding knock is crucial to improve knowledge about the stochastic occurrence of knock but also identify critical engine design to further optimize the geometry. In contrast to 0D simulations, 3D CFD simulations provide the possibility to investigate local parameters in the cylinder during the combustion.

For basic research on the piston group a new simulation technique is developed using the contact algorithm of a commercial FE-code (MARC). Several improvements were made in order to adapt the MARC solver to the problem of sliding and dynamic contact. The first computations, a real transient analysis simulating the piston group, of both a two-stroke engine and a modern direct injected four-stroke Diesel engine for passenger cars, show that the new method is able to calculate the movements, velocities and accelerations of the piston. The quality of the results is mainly influenced by the hydrodynamic effects.

Engine valve flow coefficients are used to describe the flow throughput performance of engine valve/port designs, and to model gas exchange in 0D/1D engine simulation. Valve flow coefficients are normally determined at a stationary flow test bench, separately for intake and exhaust side, in the absence of the piston. However, engine operation differs from this setup; i. a. the piston might interact with valve flow around scavenging top dead center, and instead of steady boundary conditions, valve flow is nearly always subjected to pressure pulsations, due to pressure wave reflections within the gas exchange ports. In this work the influences of piston position and flow pulsation on valve flow coefficients are investigated for different SI engine geometries by means of 3D CFD and measurements at an enhanced flow test bench.

The automotive industry uses supercharging in combination with various EGR strategies to meet the increasing demand for Diesel engines with high efficiency and low engine emissions. The charge air is heated by the EGR and the compression in the turbocharger to such an extent that high NOx emissions and a reduction in engine performance occurs. For this reason, the charge air cooler cools down the charge air before it enters the air intake manifold. In case of low pressure EGR, the charge air possesses a high moisture content and under certain operating conditions an accumulation of condensate takes place within the charge air cooler. During demanding engine loads, the condensate is entrained from the charge air cooler into the combustion chamber, resulting in misfiring or severe engine damage.