Experimental and Numerical Study of Swirling ... - Solid Mechanics

Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke
Marine Diesel Engines
Chapter 3
the cylinder and the flow is incompressible. The piston can slide to
a position where it completely covers/ closes the cylinder intake
port. Moreover, the piston is shifted manually from one position to
another and it is not in continuous motion like in real engine. Thus
the variation in in-cylinder flow characteristics is not a function of
time.
Chemical Species: A mixture of air and very small concentration (in
ppm) of glycerol droplets as seeding is used as the working fluid.
There is no fuel injection, chemical reaction and exhaust products/
gases.
Combustion: The measurement is conducted with flowing fluid
and experimental setup to be at room temperature. No combustion,
heat sources and temperature gradients (in fluid and solid walls,
piston and cylinder head) are involved.
Stratified Flow: Contrary to real engine scavenging process, no fluid
density variations occur inside the test cylinder. Therefore, there is
no in-cylinder stratified flow regime where the incoming air
interacts with exhaust gases which are lower in density than air.
Also the test cylinder is mounted horizontally instead of being
vertical in real engines. This factor can be significant if there exists a
stratified flow.
3.4 Smoke Visualization
A qualitative analysis of the test model is performed by conducting
visualization using glycerin smoke from a smoke generator. The smoke is
blown in to the setup and pictures are taken using a digital camera. The
smoke generator cannot produce a constant jet of smoke and instead injects
intermittent puffs of smoke which gradually reduces in concentration at the
end of each puff (smoke generator here is one used in Disco/ concerts etc that
produces smoke by heating and evaporating glycerin). The smoke enters the
experimental setup from one side and the distance is kept in a way that the
smoke jet has minimum effect on the actual flow pattern at the inlet to the
experimental setup. Figure 3.5 shows the smoke entering the inlet section
and being diverted at an angle by the guide vanes thus helping in checking
the general performance of the design. The flow then enters the cylinder
with an angle to the radius and bends in the axial direction (Figures 3.6).
The pictures presented in figures 3.7-3.11 are taken using a 13W (blue color)
energy saver light bulb as light source and pictures are taken using a
webcam, Microsoft LifeCam Cinema ® . The idea was to attempt to visualize
flow patterns by making the blue light giving a fluorescence-like effect after
being reflected from the smoke particles. The visualization was carried out by
first keeping the experimental setup in darkness and then using blue light as
the only light source. The light reflection from glycerin smoke particles
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Experimental Setup