University of Alberta Facility
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The Combustion
Wind Tunnel was built in the early 1970’s as one of the features of the Mechanical Engineering Building. Over the years the
tunnel has had many uses including environmental testing, aerodynamic
research of low-drag bodies for the Society of Automotive Engineers
Super-mileage project, and assisting a ski-jumper in reducing drag during
competition. The wind tunnel is a 2 story closed-loop facility. It
has 2 test sections:
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- A large low-speed upper
section (2.5m x 2.5m)
- A smaller high-speed lower
section (1.22m x 2.44m).
The tunnel is powered by a
200 HP
DC electric motor which can produce
constant air speeds up to 36 m/s in the lower test section. Starting
in early 1997, several modifications were made to facilitate the existing
tunnel for combustion related research. These included the following:
- Purge fans to clear
combustion products and reactants from the tunnel between tests.
- A combustible gas detection
system and emergency purge control system to prevent dangerous
build-ups of explosive gases in the event of a leak.
- A ceramic roof to prevent
the tunnel from burning down.
- Installation of a window
close to the point of combustion so that detailed photographs of the
flame could be made.
- A mobile traverse used for
plume characterisation (i.e. current activities: temperature profile
of the plume) and single point efficiency measurements.
- The installation of
numerous sensor packages to measure temperatures, wind velocities, gas
flow rates, gas concentrations, and more.
To
measure the efficiencies of a flare, we ignite the flare in the lower
test section of the tunnel and watch the accumulation in concentration of
various chemical species within the tunnel. The flares currently burn
methane, natural gas, propane, or a combination of these fuels diluted with
carbon dioxide and/or nitrogen. We now put liquid droplets in
the gas stream as an additional influencing parameter.
The flare is ignited
with a hydrogen flame and the tunnel is brought up to speed in order to
test the effects of cross-winds on flare efficiency. Emissions collect
in the tunnel and are measured in real time. Turbulence generators can
be placed upstream of the flare in the tunnel to simulate the gusting and
turbulence found in the wind outdoors.
Probably our most important
equipment is a suite of 7 online gas analyzers that measure hydrocarbons,
carbon dioxide, carbon monoxide, oxygen, oxides of nitrogen, and water
vapor. The following is a list of the components of this system:
- Hydrocarbons – FID (flame ionization detector)
- Carbon Dioxide – NDIR
(non-dispersive infrared)
- Carbon Monoxide – NDIR
(non-dispersive infrared)
- Oxygen – PMD (paramagnetic
detector)
- Nitric Oxide –
Chemiluminescent
- Velocity and Temperature Measurements
The wind tunnel is equipped
with various pitot tubes and anemometers in order to measure velocities at
different points and at different ranges. Temperature is measured using AD590
constant-current transducers and a variety of thermocouples.
Laser Doppler Velocimetry
and hot wire anemometry are used to make very precise measurements of flows and
turbulence. These systems can be mounted on a computer-controlled
traverse within the tunnel itself.
- Flare Stream Measurements
We measure flare gas flows
using mass flow controllers. These devices allow us to measure
gas flow rates very accurately. They are equipped with electronically
controlled valves that give us precise control when setting gas flow
rates. Currently, our mass flow meters are calibrated for natural gas,
propane, methane, air, carbon dioxide, and nitrogen. We can adjust the
flow meters for other gas types as the need arises.
Currently, we use a Pentium
II 400 MHz computer running National Instruments LabVIEW software.
The computer receives data from all of our various sensor packages through 3
separate data acquistion cards. As well, the software is used to
control the various valves, fans, and pumps throughout the two-story
tunnel. This system allows us to rapidly create or reconfigure our
laboratory for varied experiments with a minimum amount of effort.
A laser diffraction size
analyser is used to characterize the size distribution of droplets that are
added to the gas flare stream.
- Particle Image Velocimeter (PIV)
A PIV is now installed in
the Combustion Wind Tunnel. The laser used is a double-pulsed Nd:YAG with a
power of 400 mJ/pulse.
University of Alberta / NRC Facility
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