Trane Fan manual Aerodynamic Air Path, This provides smooth, spiral-free discharge

Features and Benefits

The low sound and high performance of theTrane 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 theTrane Model Q fan.

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