A. Velji

Karlsruhe Institute of Technology | KIT · Institute of Internal Combustion Engines

The aim of this study is to investigate the impact of global operating parameters, e.g., engine speed, brake mean effective pressure, and air–fuel ratio, of a turbocharged 4-cylinder GDI engine on the reactivity of soot particles against oxidation. The knowledge of soot reactivity is crucial for optimizing gasoline particulate filter regeneration s...

For modern Diesel aftertreatment systems the ratio of nitrogen dioxide (NO2) to nitrogen oxides emissions (NOx) is of great importance for the conversion of total NOx especially at low loads and low engine out exhaust temperatures. As known from previous studies the relative air-fuel ratio and so the increase of oxygen has a major impact on the in-...

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 regener...

Gasoline direct injection (GDI) shows advantages compared with port fuel injection (PFI) regarding efficiency and specific power. Due to stricter regulations for fuel consumption (via the regulation of carbon dioxide), GDI engines are becoming increasingly favourable compared with PFI engines. Therefore the share of GDI engines, especially in combi...

Modern gasoline engines are often operated with direct injection. As new test procedures like real driving emissions (RDE) are introduced higher engine loads become more relevant. Experimental measurements were done in previous projects at the institute to identify the influencing factors of particle emissions, especially at high engine loads. In t...

The proportion of nitrogen dioxide in the engine-out emissions of a Diesel engine is of great importance for the conversion of the total oxides of nitrogen (NOX) emissions in SCR catalysts. Particularly at lower engine loads and lower exhaust temperatures an increase of the already low NO2/NOX fraction will enhance the SCR operation significantly....

Der Marktanteil von aufgeladenen Ottomotoren mit Direkteinspritzung (GDI) steigt aufgrund des Potentials zur Reduzierung des Kraftstoffverbrauchs und somit der Reduktion des CO2-Ausstoßes für die kommenden Klimaziele immer weiter an. Im Vergleich zu Ottomotoren mit Saugrohreinspritzung (PFI) zeigen Motoren mit Direkteinspritzung Nachteile bei den P...

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...

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 ope...

Die Direkteinspritzung im Ottomotor ist ein zukunftsorientiertes Konzept zur weiteren Reduktion von Kraftstoffverbrauch und Schadstoffemissionen. Zur Erschließung des Potenzials der Benzin-Direkteinspritzung sind jedoch intensive Forschungs- und Entwicklungsarbeiten erforderlich. Im vorliegenden Beitrag berichtet das Institut für Kolbenmaschinen de...

In this work, the RAYLIX measurement technique is applied for the first time in the combustion chamber of a direct injection, heavy duty Diesel engine. This technique is a combination of elastic Rayleigh scattering, laser induced incandescence, and extinction. When applied properly, it can provide spatially-resolved information about soot particle...

In this work, the RAYLIX measurement technique is applied for the first time in the combustion chamber of a direct injection, heavy duty Diesel engine. This technique is a combination of elastic Rayleigh scattering, laser induced incandescence, and extinction. When applied properly, it can provide spatially-resolved information about soot particle...

To this day, Diesel engines with direct injection are the most efficient internal combustion engines for passenger cars. The major challenge of these engines with a conventional Diesel combustion process is the high level of particulate matter and nitrogen oxide emissions. Diesel engines in passenger cars normally use a pilot injection strategy for...

This chapter deals with mixture formation, combustion and pollutant emissions in high-speed direct injection (HSDI) diesel engines. In the first part of the chapter the fundamentals of mixture preparation are covered. The physics of spray formation, spray propagation and their characterisation by global values like spray angle and penetration are d...

This paper gives an overview of modern high speed photography. The systems that are used at the Institut fuer Kolbenmaschinen (IFKM) in Karlsruhe/Germany are described. Two examples for engine application outline the possibilities and challenges in connection with high speed measurements.

In this work the formation and oxidation of soot inside a direct injection spark ignition engine at different injection and ignition timing was investigated. In order to get two-dimensional data during the expansion stroke, the RAYLIX-technique was applied in the combustion chamber of an optical accessible single cylinder engine. This technique is...

In this work, heat loss was investigated in two different HCCI single cylinder engines. Thermocouples were adapted to the surfaces of the cylinder heads and the temperature oscillations were detected in a wide range of the engine operation maps. The resultant heat transfer profiles were compared to the heat losses predicted by existing models. As m...

Given the fact that, in an endeavor to achieve the goals of engineering for a trade-off between cleaning up exhaust emissions and maximizing fuel economy, two main paths are being followed in advancing and optimizing SI-engine operating strategy in the upper part-load range. On the one hand, homogenization and operation in the compression ignition...

An important source for soot formation during the combustion of diesel engines with direct injection is the interaction of liquid fuel or a very rich air/fuel-mixture with the flame. This effect appears especially in modern direct injection engines where the injection is often split in a pre- and a main injection due to noise reasons. After the ign...

The flow inside a simplified one-stroke engine with squared cross section has been calculated with compressible Large Eddy Simulation (LES) using our code SPARC and compared with the measurements on the same geometry. The one-stroke engine has a turbulence generator, which can ether generate a tumble or homogenous turbulence depending on the config...

In order to meet the permanently growing demands on future combustion processes a continuous development of experimental measurement techniques is indispensable. The Institute for Reciprocating Engines of the Universität Karlsruhe, Germany, developed a new calculation approach for the three-dimensional reconstruction of the flame propagation based...

Die hohen Anforderungen bei der Optimierung von Verbrennungsprozessen in Ottomotoren bedingen zunehmend eine konsequente Erweiterung der messtechnischen Analysemöglichkeiten. Am Institut für Kolbenmaschinen der Universität Karlsruhe (TH) wurde diesbezüglich ein neues Berechnungskonzept zur dreidimensionalen Rekonstruktion der Flammenausbreitung auf...

Single-cylinder engine tests were carried out to assess the potential of homogeneous charge compression ignition (HCCI) diesel combustion compared to the conventional heterogeneous operation mode. For the experiments a single-cylinder engine with a cylinder volume of 0.421 litre was used. Besides the comparison of conventional operation and HCCI op...

The purpose of this study was the characterization of the size distribution and the concentration of the particles emitted by diesel engines under various speed and load points, and different injection pressures. Fine and ultrafine particles emitted by modern diesel engines, in particular those with sizes below 100 nm, are of significant importance...

Today research and development in the field of gasoline engines have to face a double challenge: on the one hand, fuel consumption has to be reduced, while on the other hand, ever more stringent emission standards have to be fulfilled. The development of engines with its complexity of in-cylinder processes requires modern development tools to explo...

Engines with gasoline direct injection promise an increase in efficiency mainly due to the overall lean mixture and reduced pumping losses at part load. But the near stoichiometric combustion of the stratified mixture with high combustion temperature leads to high NOx emissions. The need for expensive lean NOx catalysts in combination with complex...

In this work the influence of various engine load changes with different engine speeds on the soot particle concentrations and properties was investigated because these operating modes are well known for short but high soot emissions. To derive specific information on emission behavior of particle matters tests were carried out with the Two-Color-M...

Modern direct injection spark ignition engines (DISI-engines) require increasing fuel-injection-pressures in order to accelerate mixture preparation. Therein the fuel-pump is an essential component. Non-conventional materials offer a high potential to realize high pressure combined with low wear and friction. An exemplary high pressure fuel pump wa...

The gasoline direct injection engine is one of the most promising concepts for the reduction of fuel consumption and emissions. Intensive research and development activities are consequently being carried out at present. This article deals with reports from investigations concerning the influence of different intake air flow conditions on in-cylind...

Single-cylinder engine tests were carried out to assess the influence of several engine operating parameters on HCCI combustion. For the experiments, single-cylinder engines with cylinder volumes of 0.5 and 2 liter were used to represent light and heavy duty application. Engine operation parameters like EGR-rate, air / fuel ratio and injection timi...

Contemporary diesel engines are high-tech power plants that provide high torques at very good levels of efficiency. By means of modern injecting-systems such as Common-Rail Injection, combustion noise and emissions could be influenced positively as well. Diesel engine are therefore used increasingly in top-range and sports cars.

The complexity of the mixture formation in direct injection engines requires - according to a suitable mixture transportation and vaporization of the fuel - detailed knowledge of the in-cylinder processes to reliably place an ignitable mixture at ignition timing near the spark plug for any speed and load. Two different optical measurement technique...

This work deals with measurements of soot concentration and particle sizes carried out at different locations in a common-rail diesel engine. For this purpose two different techniques have been applied. The extended two-colour-method was applied in the combustion chamber of a single cylinder. This method yields a crank angle resolved signal of the...

Starting with the knowledge of exhaust gas recycling (EGR), studies were made on the preparation of gas mixtures that comply with demands relating to the simultaneous decrease of NOx and particle emissions from diesel engines. The particle emissions are mainly soot. The critical pollutants from diesel engines are the NOx and particles. The discussi...

To operate gasoline direct injection engines at part load and in stratified mode the mixture formation has to fulfil several requirements. The complexity of this process requires - regarding a suitable mixture transportation and vaporisation of the fuel - an adjusted design of the combustion chamber and the intake ports to reliably place an ignitab...

The objective of this research work was to assess the potential of an electrostatic fluid atomization method for application in direct injection systems for combustion engines. The most important finding of this study was that it is possible to detect the influence of electrostatic atomization at injection pressures up to 300 bar using diesel fuel....

The innovative common rail injection system introduced with the new MTU Series 4000 engines surmounts the typical restriction inherent to conventional injection systems, i.e. the dependency of the injection pressure on engine speed. This paper describes a new combustion development procedure which systematically utilises the advantages of the commo...

Combustion zone (flame) propagation and flow velocities are measured using optical measurement techniques in a single-cylinder direct injected diesel engine. Combustion and, hence, flame propagation is detected by optical fibers and flow velocities have been measured by a new single-color, 2 dimensional Laser Doppler Velocimeter (LDV). Flame propag...

Knowledge of flame propagation and flow characteristics enables a more detailed description of in-cylinder processes as well as assessing the influences of engine operating conditions and design parameters, particularly in regard to fuel economy and emission control. Spatial flame propagation in a single-cylinder spark-ignition engine is studied by...

Knowledge of flame propagation and flow characteristics enables a more detailed description of the phenomenon flame quenching and the resulting higher unburned hydrocarbon emission. Flame propagation in a single-cylinder SI engine is studied by means of a new measuring technique using optical fibers. A Laser-Doppler-Velocimeter is used to measure f...

Internal combustion engines play a major role in transportation, due to the future emissions reduction legislation; researches are done in order to improve the combustion process behaviour and lowering the exhaust emissions. Two-stroke engines have a very good power-weight ratio, reliable, and they have a simple mechanical structure. The aim of thi...

Kurzfassung In einer Druckkammer und an einem Durchflußprüfstand wurden diverse Hochdruck-einspritzventile auf ihre Eignung für Benzin Direkteinspritzung getestet. Ziel war die Quan-tifizierung der Einflußparameter auf die Gemischbildung und den Gemischtransport. In einem Einzylindermotor wurden anschließend thermodynamische Analysen und Abgas-Mess...

The automotive industry needs to be in a continuous challenge regarding reduced fuel consumption and reduced emissions driven by both legislation and customer needs. In order to optimize the combustion process the DI-spark ignition engines were developed (DI – direct injection). The advanced gasoline engine technologies include reduced engine frict...