In English

Optical Study of Tumble, Spray and Combustion

Robin Ryrholm
Göteborg : Chalmers tekniska högskola, 2015. Diploma work - Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden, ISSN 1652-8557; 2015:38, 2015.
[Examensarbete på avancerad nivå]

The automobiles of today are getting more fuel efficient in order to meet future emission standards. It is also important to have more fuel efficient engines than the competitors. The consequence is that engine development is intensified and more ideas needs to be tested thoroughly. One of the ideas at Volvo cars is a tumble flap. The tumble flap is controlled to close a predefined part of the intake port in order to increase the tumble motion in the combustion chamber. A tumble motion is a circular motion with it's axis of rotation parallel to the engine head. To make the effects of the tumble flap clearly visible an optical engine is used. An optical engine has a cylinder and piston made of glass which makes it possible to record what happens in the combustion chamber while the engine is running. The fuel is injected directly to the combustion chamber, so called direct injection engine. This gives excellent opportunity to see how the spray is affected by an increased tumble motion. The effect on the combustion could be seen when changing parameters. The events appear in a fraction of a second why a high speed camera is used to capture the events. It has been shown that the spray is mostly effected in a late phase of the intake stroke. The spray is stable and relatively small in the early stage and is therefore only mildly effected by the ongoing gas motion. With the tumble flap activated, it is possible to observe that fuel is moving back to the valves before it is evaporated. Sometimes it is possible to see a tumble motion within the spray. If the injection pressure is increased, the initial spray stability will increase, the fuel reaches further before it is effected of the ongoing gas motion. The combustion takes place considerably faster with the tumble flap restriction. A problem with the tumble flap is that diffusion flame combustion may occur due to an increased risk of wall wetting.

Nyckelord: Optical engine, Tumble flap, Direct Injection Spark Ignition



Publikationen registrerades 2015-08-10. Den ändrades senast 2016-01-12

CPL ID: 220414

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