In order to meet future emission norms for small carbureted SI engines, such as those
used on motorcycles in India, there is a need to study mixture preparation, specifically the two-phase flow exiting the carburetor and entering the inlet manifold. A fully functional, modular experimental rig is designed and erected for performing both
qualitative and quantitative flow visualization. The vibrations of the engine are minimized to reduce their effect on the flow. A special, optically accessible tube of
square cross-section is added between the carburetor and the inlet manifold, to enable
the visualization of flow at the exit of the carburetor. An electronic circuit to obtain a
signal for the engine crank angle and convert it to a standard TTL pulse, for use on standard imaging systems to capture cycle resolved-images is also designed.
The flow in the optical section is qualitatively visualized using high and low
speed cameras. The resulting images and movies show two modes of fuel transport
within the inlet manifold, one of which is in the form of a dense cloud of fine fuel
droplets during some part of the intake stroke. The second mode is in the form of a
film at all times in the cycle, along the lower surface of the inlet manifold during
idling and along vertical walls under loaded conditions. Recirculation is seen on the
vertical walls of the manifold during idling and under load.
Finally, the thickness of the fuel film in the optical section at the exit of the
carburetor is measured, using PLIF. This part of the study also reveals that there is a film on upper surface of the optical section, at all loads and speeds. This film is lesser than the resolution of measurement for low loads, and increases to 0.5 mm in the case of highest load and speed attained at full throttle. In contrast to the loaded conditions, during idling, the film occurs on the lower surface of the manifold and its thickness is highest (1 mm.). The film is also present throughout the cycle during idling and all load-speed conditions, suggesting that the mixture that goes into the engine has a significant part of fuel in liquid form.
| Identifer | oai:union.ndltd.org:IISc/oai:etd.ncsi.iisc.ernet.in:2005/2251 |
| Date | 10 1900 |
| Creators | Prabhu, Nishikant Madhusudan |
| Contributors | Ravikrishna, R V |
| Source Sets | India Institute of Science |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Relation | G22924 |
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