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8
Features
and Benefits
The low sound and high performance
of the Trane Model Q
™
fan are achieved
by reducing noise-creating, energy-
consuming turbulence within the fan.
Airflow research and development
techniques employed were similar to
those used in perfecting today’s high
performance axial flow jet engine
compressors. The resulting smooth air
path has made the Model Q the first
vaneaxial fan to provide quiet, efficient
operation, suitable for air conditioning
duty.
Aerodynamic Air Path
A component by component analysis
of the Model Q points to 12
aerodynamic features which are keys
to a smooth air path. Starting at the
inlet, the struts [1] of the patented
bearing support are precisely
positioned in relation to the fan blades.
Air passing over the struts strikes the
blades in a pattern that prevents blade
whine.
The aerodynamically shaped inlet bell
[2] and inlet cone [3] provide uniform
axial flow parallel to the fan shaft. Air is
delivered equally to the leading edge of
the fan blades — no crowding toward
the fan tips.
Air separation is reduced by the
precision cast aluminum airfoil cross
section [4] of the fan blades. Blade pitch
[5], using a variable angle of attack in
the radial dimensions, is precisely
controlled to prevent energy loss.
Exceptionally close clearance
[6] between the blade tips and housing
reduces the eddy currents of fan tip
recirculation. The reinforcing ring
rigidizes the housing to maintain the tip
clearance. The interior of the fan wheel
is insulated to prevent hub
strengthening protrusions from
[7] windmilling in the airstream.
A precisely controlled space [8]
between the fan blades and diffuser
vanes is necessary to allow airflow
stabilization ahead of the vanes. The
vanes themselves are precision cast
aluminum and have an airfoil cross
section [9] and a precise radial pitch
[10]. This provides smooth, spiral-free
discharge.
The diffuser section design [11] is
critical. A precisely determined
diffusion angle produces the greatest
possible static regain within the
confines of the fan. An end cone
[12) covers the fan drive assembly,
thereby reducing the turbulence
generated by air passing over exposed
drives.
Precise Manufacturing Assures
Performance — Advanced
manufacturing techniques assure the
same performance characteristics for
each production Model Q fan.
•
Fin Struts — The fin struts of the
patented bearing support are precisely
positioned in relation to the fan blade.
Air passing over the struts strikes the
plate in a pattern that prevents the
irritating whine, from blade frequency,
which is characteristic of industrial
vaneaxials.
•
Inlet Bell and Cone — The
aerodynamically shaped inlet bell and
inlet cone provide uniform axial flow
into the fan parallel with the fan shaft.
Air is delivered equally to the leading
edge of the fan blades. This prevents
crowding toward the blade tip.
•
Wheel — The wheel consists of 8
precision cast blades with a twisted
radially projected shape and airfoil
cross section. This radial projection
utilizes a variable angle of attack in the
radial dimension and prevents radial
movement as the air particles move
through the wheel.
•
Tip Clearance — Close clearance
between the blade tips and housing
reduces eddy currents due to tip
recirculation. The reinforcing ring holds
the housing in its precise shape to
maintain proper clearance.
•
Vane Spacing — Precise space
between the fan blades and the diffuser
vanes is necessary to allow flow
stabilization ahead of the vanes. The 29
diffuser vanes also have an airfoil cross
section and a twisted, radially projected
shape. This provides smooth, spiral-
free air discharge.
•
Precision Cast Aluminum Fan and
Diffuser — Being cast, blade and vane
shapes are permanently and precisely
fixed. They are not subject to
misalignment or distortion as are
welded, sheet metal forms.
•
Diffuser Section — The diffuser
section design is critical. A precisely
determined flare angle at the diffuser
end produces the greatest possible
static regain within the confines of the
fan. Thus, externally mounted diffuser
accessories, common for industrial
vaneaxials, are not necessary.
•
Hydraulically Expanded Flow-
Formed Housing — In this process,
the cylindrical housing is drawn to its
final form over an expansion die. The
metal, expanded beyond its elastic
limit, permanently retains the precision
form imparted by the die.
•
Ductile Weld Technique — This
technique is required for the fan
housing seam to guarantee success of
the expansion forming process. The arc
and “puddle” are submerged in
molten flux that shields the weld
material from oxidation. This prevents
brittleness and also anneals the weld.
The result is a flexible, ductile seam
capable of being drawn and formed —
another example of the advanced
technology used in the Trane Model
Q fan.