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Content archived on 2024-04-16

Interaction of jets with walls


Study the influence of the combustion chamber walls on mixture formation, combustion, the emission of pollutants and on energy efficiency of direct injection Diesel engines.
A detailed analysis of the spray wall impingement process was carried out by using the phase Doppler anemometry technique to obtain simultaneous measurements of droplet size and droplet velocity near the wall at high gas pressure and high gas and wall temperatures. An experimental study of a diesel spray impinging on a flat surface was completed and many insights into the wall spray structure were gained through analysis of the 2 velocity component histories at various distances from the wall.

In order to investigate the influence of the wall and the squish flow on the mixture formation mechanism, the high speed Schlieren technique for the 2-period engine was developed. Optical components were optimised to enable observation in the direction of the cylinder axis and perpendicular to this direction. With this system, it is possible to measure the wall temperature with high resolution during the complete cycle. This is accomplished through the use of an electronic unit inside the piston which functions independently from an external power source.

The objective of this project was the development of special measurement techniques and devices for the study of combustion chamber wall effects on the air/fuel mixing process of a direct injection diesel engine. Methods for visualising the initial atomization and wall impingement of a diesel spray are discussed. The development and implementation of a film thicknessmeasurement technique is detailed and a method for using this technique in high pressure/high temperature equipment is given.
This project is a follow up contract of EN3E-0143-D and forms an integral part of work carried out in contract JOUE-CT90-0029. Work is continued on the study of the influence of the interaction of the fuel jet with the walls of the injection bowl in the piston surface, on the mixture formation. Therefore the injection operation, injection pressure and injector/wall distance was varied. In all participating laboratories the injection systems developed by D-B are used.

The overall conclusion of this project, which is nearly finished, and contract EN3E-0143-D is, that the squish (internal mass transfer effect due to the piston movement and the irregular shape of the combustion chamber e.g. bowl in the upper surface of the piston in Diesel engines) and the combustion chamber wall are the most important parameters in the mixture formation of Diesel engines. Contract JOUE-CT90-0029 will study how these parameters influence mixture formation.


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Daimler-Benz AG
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Epplestraße 225
70567 Stuttgart

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Participants (3)