Labyrinthian Fan

Abstract

An improved fan including means to form a seal at the fan tips and means to form a labyrinthian seal in the shroud gap. The combination of seals increases the effective airflow of the fan, reduces the operational noise, and reduces the horsepower required to drive the fan.

Description

BACKGROUND OF THE INVENTION

This invention relates to engine cooling systems and in particular to an improved fan system for use in the cooling systems.

The automotive industry has been faced with ever increasing cooling demands in vehicles. Increases in engine size and the addition of both pollution control equipment and power operated accessories have contributed to the need for higher cooling capacity.

At the same time as the demands for higher cooling capacity have increased, the demand for quieter operation has likewise increased. Because, in general, the noise attributed to the fan increases as its capacity to cool increases, the industry has been faced with a dilemma.

Also, with the addition of more auxillary equipment it is desirable to reduce the horsepower demands of the fan. This has been difficult because the horsepower needed to drive the fan, in general, increases as its capacity to cool increases.

There have been attempts to solve this problem. One of these is the flex-fan, which reduces pitch as engine speed increases and thereby reduces the noise and horsepower necessary to drive the fan at high speeds. Other fans have been developed which are temperature sensitive. They reduce pitch as the ambient and/or engine termperature is lowered and therefore reduce noise and horsepower requirements when the cooling capacity is unnecessary. Other devices change the fan speed as a function of temperature.

SUMMARY OF THE INVENTION

This invention presents a fan and a combination of a fan and shroud which dramatically increases the useable air flow of a given fan, improves its efficiency, and at the same time reduces the noise. Typically, the air flow is increased with a net decrease in noise. That is, the additional noise produced by the increased air flow is less than that eliminated by use of the invention.

If it is desired to maintain a certain airflow, large reductions in noise are observed in systems constructed in accordance with this invention. The constant airflow may be achieved by lessening the pitch and/or diameter of the fan and also by reducing its operating rotational speed. Thus, systems constructed in accordance with this invention produce less noise, require less input horsepower, and produce greater airflow than prior art fans.

The prior art fans are normally affixed to the engine which in turn is resiliently mounted to the vehicle frame. This resiliency isolates engine vibration from the vehicle and results in the engine moving as a reaction to its output torque. A heat exchanger or radiator and a stationary shroud are solidly mounted to the vehicle frame. To accommodate the relative movement between the fan and stationary shroud, and to allow for variances in installation, it is normal to provide clearance between these two members of 3/4 to 1 inch radially.

The invention accomplishes the remarkable improvements without reducing these required clearances. A rotating member is added to the fan at the periphery with a minimum clearance between the blade tips and this member, hereinafter referred to as a rotating shroud. This rotating shroud coacts with the stationary shroud, a box-like enclosure attached to the radiator. These two shrouds form a labyrinth seal in the clearance space between them, hereinafter referred to as the shroud gap.

Three separate phenomena exist at the outside diameter of prior art fans: (1) a localized flow of air from the pressure side of a blade to its suction side over the blade tip; (2) a toroidal circulation of air from the exhaust side of the fan to the inlet side of the fan; and (3) a continuous shearing action through these turbulent flow regimes caused by the fan blade rotation.

The addition of the rotating shroud to the fan circumference, with minimal clearances, effectively limits air flow from the pressure side of the fan blade to its suction side over the blade tip. The rotating shroud coacting with the stationary shroud in a labyrinth sealing relationship greatly reduces the recirculating toroidal flow from the high-pressure fan discharge to the lowpressure fan inlet zone in the shroud gap. The entire system thereby minimizes and mechanically separates the undesired turbulent flows. This action significantly reduces blade shear through turbulent flow patterns and results in improved useful air delivery, reduced input horsepower requirements, and greatly reduced noise generation.

In the preferred embodiment, a labyrinthian fan is constructed by disposing a U-shaped rotating shroud around the circumference of the fan. The fore and aft disc portions of the U-channel extend radially outwardly from the fan circumference. The stationary shroud, a box-like structure, includes a circular orifice of lesser dimension than the sides of the box. This orifice is disposed between the disc portions of the rotating shroud forming a labyrinth seal in the shroud gap. Thus, the recirculation flows are reduced and the concurrent benefits of reduced noise, increased airflow, and reduced horsepower are realized.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention will become more apparent in the following detailed description of a preferred embodiment when read in conjunction with the figures in which:

FIG. 1 is a plan view of a fan and shroud constructed in accordance with the principles of this invention.

FIG. 2 is a cross-sectional view of the fan and shroud shown in FIG. 1.

FIG. 3 schematically depicts the problem in the prior art solved by this invention.

FIG. 4 schematically depicts the air flow associated with fans constructed in accordance with this invention.

FIGS. 5-9 schematically illustrate exemplary alternate embodiments of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A labyrinthian fan constructed in accordance with the principles of this invention is denoted generally by the reference numeral 10 in FIGS. 1 and 2. The fan includes a central hub 12 with mounting holes 14. A plurality of blades 16 emanate radially from the hub 12. The particular type of fan is immaterial to this invention and thus the fan 10 has been illustrated somewhat diagrammatically. However, this invention may be used with any type of fan such as flex-fans, temperature sensitive fans and the like.

A sealing member 18 is affixed to the tips of the fan blades 16. In this preferred embodiment the sealing member 18 is in the form of a U-shaped channel, however, as will be treated in detail hereinafter, other configurations could be used. The U-shape is preferred because of its rigidity in resisting deformation and the resulting stresses when the fan 10 is rotating. The sealing member 18 may be attached to the fan blades in any conventional manner; i.e., bolts, rivets, welds and the like.

As seen in FIG. 2 the fan 10 is positioned behind a radiator 20. A box-like stationary shroud 22 surrounds the fan 10. The shroud 22 includes a downwardly turned flange 24 which operates in conjunction with the sealing member 18 to form a labyrinth seal at the shroud gap 30.

Turning now to FIGS. 3 and 4, the operating principles of this invention, as now understood, will be described. FIG. 3 illustrates a conventional fan blade 26, which is rotatably mounted behind a heat exchanger or radiator 20 to the engine 34 by conventional means (not shown) and a shroud 28. Because the engine to which the fan is mounted moves relative to the shroud 28, a shroud gap 30 is provided to prevent contact between the fan 26 and the shroud 28. As stated earlier, the shroud gap 30 is generally from 3/4 to 1 inch radially. This relatively large shroud gap 30 permits undesirable turbulent airflows to occur about the fan blade tips. These flow conditions have been schematically depicted in FIG. 3.

The flow indicated as 32 is the desirable flow which provides useful heat exchanger cooling air. Flow path 38, indicated as a torous pattern in the shroud gap 30, and flow 39, depicted as a localized flow at each blade tip, are undesirable. They produce no useful cooling air movement, cause fan noise, and create losses in fan efficiency.

In FIG. 4, the preferred embodiment flow conditions are schematically illustrated. It is readily apparent that any recirculating flow 38 in the shroud gap 30 will have to follow a twisted or tortuous path because of the labyrinth seal formed by the flange 24 and the sealing member 18. The tortured nature of the shroud gap greatly increases the path's resistance to fluid flow and consequently reduces the amount of recirculating air. By reducing the recirculating air 38, the amount of desirable flow 32 is increased and the noise caused by the recirculating air 38 is reduced. Additional benefits are achieved since the clearance between the fan blades and the rotating shroud is extremely small, thereby essentially eliminating flow 39. However, the rotating shroud 18 could be spaced somewhat from the blade 16.

In the preferred embodiment it has been determined that the best results are achieved when the tips of the sealing member 18 and the flange 24 are either in alignment as shown in FIG. 4 or if the flange enters the bight of the U as shown in FIG. 5. Some benefit of this invention may be realized when the flange 24 is outside of the bight of the sealing member 18 (FIG. 6) but tests have shown that the benefits are reduced.

The benefits of increased useful airflow, reduced noise generation, and reduced horsepower requirements are realized by developing a labyrinth seal in the shroud gap and by minimizing the localized flow over each blade tip. These two actions coupled with the barrier effect which prevents the interaction between the remaining, though greatly reduced, toroidal recirculation in the shroud gap and flow circulation over the fan tips affords the advantages noted. There are any number of configurations which would achieve this goal. FIGS. 7-9 schematically illustrate three possible configurations. Many more could be used. The embodiment discussed is preferred because of the strength requirements in vehicular systems with high rotational speeds. In low speed applications other constructions may be preferred. Many other designs can be utilized without departing from the scope and spirit of the invention as is set forth in the appended claims.

Claims

What is claimed is:

1. In an automotive cooling system the combination comprising:

a heat exchanger and an automotive engine mounted for both axial and radial movement with respect to each other;

a fan rotatably mounted to said engine and having a plurality of blades and including sealing means for creating a labyrinth seal; and

a shroud mounted to said heat exchanger and encircling said fan, said shroud having means for coacting with said sealing means on said fan to form a labyrinth seal in the gap between said shroud and said fan;

said means on said fan and said shroud which form said labyrinth seal being disposed such that relative axial and radial movement therebetween does not interfere with the rotation of said fan.

2. The system set forth in claim 1 wherein said sealing means is a U-shaped hoop circumferentially disposed about said fan blades and said coacting means is an inwardly turned flange on said shroud.

3. The system set forth in claim 2 wherein the tip of said flange is substantially aligned with the tips of said U-shaped sealing means.

4. The system set forth in claim 2 wherein the tip of said flange is disposed within the bight of said U-shaped sealing means.

5. In an automotive cooling system the combination comprising:

a radiator and an automotive engine mounted for movement with respect to each other;

a fan rotatably mounted to said engine and having a pluarlity of blades and including a substantially U-shaped hoop disposed about the perimeter of said blades for creating a labyrinth seal; and

a shroud mounted to said heat exchanger and encircling said fan, said shroud having an inwardly depending flange entering the bight of said hoop for coacting with said hoop to form a labyrinth seal in the gap between said shroud and said fan;

said hoop and said flange which form said labyrinth seal being disposed such that relative axial and radial movement therebetween does not interfere with the rotation of said fan.