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Optical Research Engines-Tools in Gasoline Engine Development?
Technical Paper
944010
Sector:
Language:
English
Abstract
Numerous research engines have been designed to allow the
optical investigation of in-cylinder fluid flow and combustion
phenomena. Their design concepts are usually matched to the
requirements of the optical techniques applied in the actual
studies, and thus, machines have resulted which quite often have a
rather limited scope of application.
However, the amount of information to be gained from diagnostic
techniques such as LDA, PIV, CARS, LIF, combustion photography
etc., created interest in applying such techniques in the
development process of combustion systems. As combustion system
engineering aims at supporting and governing flame propagation by
means of in-cylinder fluid dynamics and turbulence generation and
by the preparation and distribution of the fuel-air mixture, there
is considerable interest to visually "see" the influence
of hardware or process variations on flow field, on mixture
distribution and on flame propagation.
On the one hand this creates the need for an optical engine
concept which allows:
1. a wide range of operating conditions for engine speed and
load
2. the variation of hardware components, e.g. the attachment of
different cylinder heads to an optical base engine, and
3. which provides access to the combustion chamber necessary for
the straightforward application of the diagnostic techniques.
On the other hand, engine development requires data which
provide fast and specific insight into the phenomena of interest
and which are sensitive enough to demonstrate the variations
introduced in the different steps of hardware or process
design.
The paper describes the design of a singe cylinder base engine
which provides optical access to the combustion chamber via glass
cylinders and a piston with a glass crown.
The application of this engine to the visual analysis of
gasoline mixture formation and combustion is demonstrated with
examples given for two- and four-valve cylinder heads.
The optical methods used in this study comprise of Laser-induced
Florescence (LIF) to image the unburned mixture within the laser
light sheet illuminating a plane of the combustion chamber and of
flame photography to visualize flame propagation. Simultaneous
recording of engine thermodynamic data allows to compare
conventional engine diagnostics with the results gained from the
optical techniques.