Jürgen Pfeil

A Basic Experimental Study of Gasoline Direct Injection at Significantly High Injection Pressures

In gasoline direct injection engines with stratified-combustion strategies only a short time is available for mixture preparation. Therefore, investigations are carried out to evaluate the influence of high injection pressure up to 50 MPa in order to optimize the mixture preparation. Two types of multi-hole injectors are analyzed in a pressure vessel under various pressure and temperature conditions. Laser light sheet visualization technique is applied in order to determine spray characteristics like shape, angle, penetration depth and spray width. To determine the velocity of the air surrounding the spray, a PIV (Particle Image Velocimetry) measurement technique is used. Droplet sizes and velocities are measured with a Phase Doppler Anemometer (PDA) in different positions in the spray center and at the spray edge. Spray visualization experiments show the influence of evaporation on spray propagation at higher temperatures. With increasing chamber pressure, a widening of the jet is observed, while its length remains nearly constant. PIV-measurements show a torus-like flow at the spray front and a distinctive air entrainment into the spray, which depends on injection pressure and chamber pressure. Analyses of droplet velocity and diameter with PDA reveal high velocities of very small droplets at higher injection pressures. However, droplet velocity does not increase in the same dimension as does the fuel pressure.

High-Speed Visualisation of Combustion in Modern Gasoline Engines

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 exploit the full potential in order to reduce fuel consumption. Especially optical, non-intrusive measurement techniques will help to get a better understanding of the processes. With the presented high-speed visualisation system the electromagnetic radiation from combustion in the UV range is collected by an endoscope and transmitted to a visualisation system by 10, 000 optical fibres. The signal is projected to 1, 920 photomultipliers, which convert the optical into electric signals with a maximum temporal resolution of 200 kHz. This paper shows the systematic application of flame diagnostics in modern combustion systems. For this purpose, a single-cylinder SI engine has been modified for a spray guided combustion strategy as well as for HCCI. The characteristics of flame propagation in both combustion modes were recorded and correlated with thermodynamic analyses. In case of the spray guided GDI engine, high pressure fuel injection was applied and evaluated.

Experimentelle Untersuchungen zur Entwicklung des kurbelwinkelaufgelösten Brennraumluftverhältnisses im Transientbetrieb eines Ottomotors mit Direkteinspritzung

Mit der absehbaren Einfuhrung neuer gesetzlicher Zertifizierungszyklen (WLTP) und unter Berucksichtigung des realen Kundenfahrverhaltens (RDE – Real Driving Emissions), gewinnt die Untersuchung der transienten Betriebsphasen eines Verbrennungsmotors zunehmend an Bedeutung. Eine detaillierte Analyse dieser Ubergangszustande stellt dabei besondere Herausforderungen sowohl an die eingesetzte Messtechnik als auch an die angewandte Entwicklungsmethodik. Dies wird vor dem Hintergrund deutlich, dass meist nur einige wenige Arbeitsspiele wahrend dieser transienten Betriebsphasen fur die vergleichsweise hohen Emissionen verantwortlich sind.

Investigating the Cause of Initial Pre-ignition - A New Approach

The irregular combustion phenomenon of low speed pre-ignition (LSPI) is still an important issue in modern internal combustion engine development and research, despite numerous publications looking into different directions such as the influence of injection strategy, scavenging, engine oil and fuel properties, and solid particulate matter as a potential ignition source.