Low noise cooling system

Abstract

 A cooling system (20) for use with an internal combustion engine (24) is disclosed, the cooling system (20) including a fan (26) defining a central axis, a radiator (30) asymmetrical in shape about the central axis, and a fan shroud (34) disposed about the fan (26) and defining a flow path for directing cooling flow across the radiator (30). The fan shroud (34) includes a radially converging inlet portion (40), a radially diverging outlet portion (44) and a cylindrical transition portion (42) therebetween. The radially converging inlet portion (40) and the radially diverging outlet portion (44) are axisymmetrical in shape about the central axis and are substantially symmetric with one another about an imaginary plane (49) constructed normal to the central axis. The geometry of the fan shroud (34), the alignment of the fan shroud (34) relative to the fan (26), and the fan spacing relative to the radiator (30) are determined according to dimensionless numbers relating the various geometries to the fan diameter and the projected axial fan chord.

Description

Technical Field

[0001] This invention relates generally to a low noise fan and shroud arrangement for use with an engine cooling system.

Background Art

[0002] One dominant source of engine noise is the noise emitted by its cooling system. Such noise is a function of a variety of factors, including the type and position of the fan, the design of the fan shroud, and the type, size and position of the radiator core.

[0003] One example of a noise suppressing fan shroud is the fan shroud entrance structure disclosed in U.S. Patent No. 3,903,960 to Beck et al. The fan of U.S. Patent No. 3,903,960 is typical of other prior art fan structures in that it immediately tapers between a circular shape corresponding to that of the cylindrical discharge throat section and a rectangular shape corresponding to that of the radiator. As a result of such an asymmetrical discharge, separation and turbulence of cooling flow exiting the cylindrical discharge throat section, and its associated noise, is produced.

[0004] Another example of a noise suppressing fan shroud is shown in U.S. Patent No. 5,024,267 to Yamaguchi et al. which discloses a fan shroud having a box-shaped main body covering one of the surfaces of a heat exchanger and a cylindrical portion penetrating through the main body. A fan is disposed in the cylindrical portion and extends partially into the box-shaped main body. The main body includes an enlarged portion disposed adjacent to and corresponding to the protruding portion of the cylindrical portion to create a high static pressure region between the fan and radiator in an attempt to increase axial flow and reduce noise. However, without a physical structure guiding discharge flow from the fan, some recirculation and turbulence, and its associated noise, at the fan discharge is still likely to occur as a result of the influence of the asymmetrical box-shaped main body.

[0005] U.S. Patent No. 3,872,916 to Beck discloses a radially diverging shroud exit section which immediately tapers between a circular shape corresponding to that of the cylindrical discharge throat section and a rectangular shape corresponding to that of the radiator. As a result of such an asymmetrical inlet, inlet distortion and downstream turbulence of cooling flow through the fan is produced.

[0006] A need therefore exists for an engine cooling system having reduced operating noise levels. Such a cooling system should be adaptable to both blower-type and suction-type fan arrangements as well as axial flow and mixed flow fans. Preferably, such a cooling system should provide a defined flow path to reduce inlet distortion, separation, recirculation and turbulence of cooling flow through the fan. Ideally, such a cooling system should also be compact in view of vehicle space restrictions and should provide improved cooling characteristics.

Disclosure of the Invention

[0007] According to the invention, a cooling system for use with an internal combustion engine is disclosed, comprising a fan defining a central axis for the cooling system, the fan having an overall diameter and a projected axial chord width associated therewith, a heat exchanger asymmetrical in shape about the central axis, a fan shroud disposed about the fan, the fan shroud defining a flow path for directing cooling flow axially across the heat exchanger. In one embodiment, the fan shroud includes a radially converging inlet portion, a radially diverging outlet portion and a cylindrical transition portion disposed between the inlet and the outlet portions, which inlet and outlet portions are axisymmetrical in shape about the central axis.

[0008] In another embodiment, the fan shroud is mounted stationary about the fan defining a predetermined small radial running clearance therewith, the fan shroud including a radially converging inlet portion and a cylindrical transition portion, the radially converging inlet portion being axisymmetrical in shape about the central axis, and a box-shaped plenum sealingly connected between the stationary fan shroud and the heat exchanger, the box-shaped plenum extending between the stationary fan shroud and the heat exchanger and defining an abrupt transition with the fan shroud between the asymmetrically shaped heat exchanger and the axisymmetrical shaped fan shroud.

[0009] In yet another embodiment, the improvement is disclosed comprising the fan shroud including a radially converging inlet portion axisymmetrical in shape about the central axis and a radially diverging outlet portion axisymmetrical in shape about the central axis.

Brief Description of the Drawings

[0010] Fig. 1 is a side cross-sectional view of a cooling system including a fan, fan shroud and heat exchanger arranged in a suction mode according to one embodiment of the present invention.

[0011] Fig. 2 is a perspective view of the cooling system of Fig. 1.

[0012] Fig. 3 is a partial side cross-sectional view of the fan shroud mounting arrangement of Fig. 1.

[0013] Fig. 4 is a partial side cross-sectional view of a first alternate fan shroud mounting arrangement for the cooling system of Fig. 1.

[0014] Fig. 5 is a partial side cross-sectional view of a second alternate fan shroud mounting arrangement for the cooling system of Fig. 1.

[0015] Fig. 6 is a partial side cross-sectional view of a cooling system including a fan shroud and heat exchanger arranged in a suction mode according to a second embodiment of the present invention.

[0016] Fig. 7 is a partial side cross-sectional view of a first alternate fan shroud mounting arrangement for the cooling system of Fig. 6.

[0017] Fig. 8 is a partial side cross-sectional view of a second alternate shroud mounting arrangement for the cooling system of Fig. 6.

[0018] Fig. 9 is a partial side cross-sectional view of a cooling system including a fan, fan shroud and heat exchanger arranged in a blower mode according to a third embodiment of the present invention.

[0019] Fig. 10 is a partial side cross-sectional view of a cooling system including a rotating fan and shroud assembly and heat exchanger arranged in a suction mode according to a fourth embodiment of the present invention.

[0020] Fig. 11 is a partial side cross-sectional view of a cooling system including a rotating fan and shroud assembly and heat exchanger arranged in a blower mode according to a fifth embodiment of the present invention.

[0021] Fig. 12 is a partial side cross-sectional view of a cooling system including a mixed flow fan, fan shroud and heat exchanger arranged in a suction mode according to a sixth embodiment of the present invention.

Best Mode for Carrying Out the Invention

[0022] Prior to the present invention, fan structures have focused primarily on improving flow characteristics of cooling flow entering the fan. As such, various radiused fan inlet structures have evolved in an attempt to reduce turbulence of cooling flow entering the fan. However, the overall design of the fan structure and of fan spacing relationships relative to the fan structure is equally important to achieving a cooling system having reduced noise characteristics. The present invention provides a fan structure and optimized fan spacing relationships which yield an efficient cooling system having reduced operating noise levels.

[0023] Referring now to Fig. 1, a cooling system 20 for a vehicle 22 is shown. Cooling system 20 is mounted and driven separate from engine 24 of vehicle 22 to reduce noise produced by the vehicle. Cooling system 20 includes a rotating bladed fan 26 hydraulically driven by a motor 27. Motor 27 derives hydraulic power from engine 24. Fan 26 is rotatably mounted independent of engine 24 within a cooling compartment 28 and is separated from the engine by a noise barrier 29. Fan 26 is mounted downstream of a radiator 30 and oil cooler 31 to induce flow from inlets 32 of compartment 28 thereacross as shown by the direction of the arrows.

[0024] To reduce noise and efficiently pump cooling flow across heat exchangers 30 and 31, fan 26 is mounted in close running radial clearance within a stationary fan shroud 34. Fan 26 defines a central axis 38 for cooling system 20 and rotates thereabout to define a swept region generally cylindrical in shape. Disposed between fan shroud 34 and radiator 30 is a plenum 36. Plenum 36 seals between fan shroud 34 and radiator 30 and provides an optimally sized and spaced transition duct that, together with the fan shroud, minimizes inlet distortion and large scale turbulence of cooling air entering the fan.

[0025] Referring now to Fig. 2, cooling system 20 is shown in perspective view to better illustrate the axisymmetric flow path defined by the fan shroud and the asymmetric flow path defined by the plenum. Fan shroud 34 is generally circular in shape corresponding to fan 26 and is concentric about central axis 38. Conversely, plenum 36 is rectangular in shape corresponding to radiator 30 and is asymmetric throughout its length along central axis 38. Rather than tapering between a rectangular shape corresponding to that of the radiator and a circular shape corresponding to that of the fan shroud, plenum 36 is box-shaped throughout its length to define an abrupt transition at its junction with the fan shroud.

[0026] Referring now to Fig. 3, cooling system 20 is shown in greater detail. As previously stated, because fan 26 is disposed downstream of radiator 30, cooling system 20 operates in a suction mode to induce cooling flow across the radiator. Flow exiting the radiator enters box-shaped plenum 36 and is drawn into the fan shroud 34 where it transitions from the asymmetric rectangular flow path of the radiator to an axisymmetric flow path. Through testing, a variety of preferred dimensional relationships were determined relating the geometry of the fan to the geometry of the fan shroud, the spacing of the fan shroud relative to the radiator, and the radial running clearance between the fan and fan shroud. These dimensional relationships were found to enhance performance and reduce noise.

[0027] Fan shroud 34 includes a radially converging inlet portion 40, a cylindrical transition portion 42 and a radially diverging outlet portion 44. Inlet portion 40 and outlet portion 44 each are shaped axisymmetric about central axis 38 and, further, are preferably substantially symmetric with one another about an imaginary plane, such as plane 49, constructed perpendicular to central axis 38. The radially converging axisymmetric shape of inlet portion 40 uniformly accelerates flow into the fan to reduce inlet distortion and minimize turbulence intensity. The transition portion 42 permits the fan to be mounted at low running clearances with the fan shroud, thereby reducing recirculation and turbulence across the leading edge of the fan blades. The radially diverging axisymmetric shape of outlet portion 44 uniformly decelerates or diffuses flow exiting the fan to maintain minimal recirculation and turbulence across the fan blades.

[0028] Although a variety of radially converging and diverging axisymmetric inlet and outlet portions can be used to perform the present invention (i.e., inlet and outlet portions having varying radii of curvature), inlet and outlet portions 40 and 44, respectively, are axisymmetrically shaped about respectively, are axisymmetrically shaped about central axis 38 each having a preferred constant radius of curvature R related to the overall fan diameter D. Although the radius of curvature of the inlet portion can be preferably greater than or equal to the radius of curvature of the exit portion, in the preferred embodiment the inlet and outlet portion radii of curvature are substantially equal to provide upstream and downstream flow path symmetry. For the preferred embodiment, the radius of curvature R is desirably in the range of about 6 percent to about 10 percent of the overall fan diameter D and, in the specific preferred embodiment of Fig. 3, is approximately 8 percent of the overall fan diameter D.

[0029] Similarly, although a variety of fan shroud axial lengths and placements relative to the fan can be used to practice the present invention, a preferred axial length and axial placement exists for transition portion 42 relative to fan 26 to reduce recirculation across the fan blades. For example, the axial length L of transition portion 42 is desirably in the range of about 40 percent to about 75 percent of the projected axial chord width W of fan 26 and, in the specific preferred embodiment of Fig. 3, is approximately 50 percent of the projected axial width W. Further, leading edge 48 of fan 26 is aligned with a plane 49 constructed normal to central axis 38 and passing through the junction of inlet portion 40 with transition portion 42. As a result, a predetermined projected chord width portion P of fan 26 extends into outlet portion 44. The predetermined projected chord width portion P is directly related to the axial length L of transition portion 42 and is desirably in the range of about 60 percent to about 25 percent of the projected axial chord width W of fan 26 and, in the specific preferred embodiment of Fig. 3, is approximately 50 percent of the projected axial width W.

[0030] To reduce recirculation across the tips of the fan blades, there exists a desired close running radial clearance T between the fan blades and the fan shroud. In the preferred embodiment, radial clearance T is in the range of about 0.1 percent to about 1.0 percent of the overall fan diameter D and, in one specific embodiment, is approximately 0.5 percent of the overall fan diameter D.

[0031] Beyond the shape of fan shroud 34 and its placement, there exists a desired axial spacing relative to the exit surface 50 of radiator 30 that results in further reductions in levels of noise. In the preferred embodiment, the entrance of fan shroud 34 is optimally spaced from exit surface 50 a distance E of about 1.5 percent to about 10 percent of the overall fan diameter D and, in the specific preferred embodiment of Fig. 3, is approximately 2 percent of the overall fan diameter D.

[0032] Other fan mounting arrangements contemplated within the scope of the present invention include different mounting locations of plenum 36 to fan shroud 34. In addition to sealingly connecting plenum 36 flush with the entrance of inlet portion 40 as depicted in Fig. 3, plenum 36 can be sealingly connected further downstream to encompass varying portions of fan shroud 34. For example, in Fig. 4, box-shaped plenum 36 is mounted to fan shroud 34 at transition portion 42 encompassing inlet portion 40, while in Fig. 5 plenum 36 is mounted to the exit of outlet portion 44 encompassing the entire fan shroud 34. By extending plenum 36 over a portion of fan shroud 34, the radius of the inlet bell-mouth can be increased to further reduce separation and turbulence while still maintaining a compact shroud and plenum assembly. Further, an additional noise barrier is provided radially outward of fan shroud 34, also tending to shield noise levels produced during fan operation.

[0033] Referring now to Figs. 6 through 8, various axisymmetric fan shrouds are depicted shaped similar to fan shroud 34 except for the elimination of the radially diverging outlet section. In Figs. 6 through 8, axisymmetric fan shroud 60 is disposed downstream of a box-shaped plenum similar to fan shroud 34 of Fig. 1. As such, there exists similar desired spacing relationships tending to reduce noise produced by the fan. However, the preferred axial length and axial placement for fan shroud 60 relative to fan 26 differs somewhat from the axial length and axial placement disclosed for fan shroud 34. For example, the axial length L' of transition portion 61 is desirably in the range of about 65 percent to about 85 percent of the projected axial chord width W of fan 26 and, in the specific preferred embodiment of Fig. 3, is approximately 80 percent of the projected axial width W. Leading edge 48 of fan 26 is similarly aligned with a plane 62 constructed normal to central axis 38 and passing through the junction of inlet portion 63 with transition portion 61. As a result, a predetermined projected chord width portion P' of fan 26 extends beyond fan shroud 60. The predetermined projected chord width portion P' is related to the axial length L' of transition portion 61 and is desirably in the range of about 35 percent to about 15 percent of the projected axial chord width W of fan 26 and, in the specific preferred embodiment of Fig. 6, is 20 percent of the projected axial width W. Similar to fan shroud 34, other fan mounting arrangements contemplated for fan shroud 60 include plenum 36 being sealingly connected to transition portion 61 and encompassing inlet portion 63 (Fig. 7) and plenum 36 being sealingly connected to the exit of transition portion 61 and encompassing the entire fan shroud 60 (Fig. 8).

[0034] The present invention is also adaptable to blower-type cooling systems by mounting the fan and fan shroud upstream of the radiator and maintaining the leading edge of the fan aligned with the junction of the inlet and transition portions of the fan shroud. For example, in Fig. 9 cooling system 70 is shown including a similar fan shroud 74 and fan 76 to that of cooling system 20, except fan shroud 74 and fan 76 are disposed upstream of radiator 80 to blow or force air across radiator 80.

[0035] The present invention is also adaptable to shrouded fan assemblies mounted both in a suction mode downstream of the radiator (Fig. 10) and in a blower mode upstream of the radiator (Fig. 11). For the shrouded fan assemblies shown in Figs. 10 and 11, a labyrinth seal 82 is provided between the plenum and fan shroud similar to that disclosed in U.S. Patent No. 5,183,382 issued to a common inventor on 02 February 1993. In Fig. 10, fan shroud 84 is shaped and aligned relative to fan 86 similar to that of cooling system 20, except that shroud 84 is attached to fan 86 to define a fan and shroud assembly. Similar to plenum 36, plenum 88 is sealingly connected between a radiator 89 and the inlet portion 91 of fan shroud 84. As such, plenum 88 defines the stationary portion of the labyrinth seal 82, while inlet portion 91 of fan shroud 84 defines the rotating portion of labyrinth seal 82.

[0036] Further, various features of the present invention can be combined to yield combinations of fan shroud configurations having reduced noise characteristics. For example, in Fig. 12 fan shroud 90 is shown adapted for use with a mixed flow fan 92 in a mixed flow cooling system 93. Similar to fan shroud 34 of cooling system 20, fan shroud 90 includes an axisymmetric radially converging inlet portion 94 and an axisymmetric radially diverging outlet portion 96. However, to provide close radial running clearance with mixed flow fan 92, transition portion 98 has a radially diverging shape corresponding to the blade contours of fan 92. The preferred spacing relationships for cooling system 93 are substantially the same as those for cooling system 20, except that the overall fan diameter refers to the mean fan diameter of fan 92.

[0037] From the above description, it can be seen that an engine cooling system is provided that includes a fan shroud optimally configured to reduce noise generated by separation, recirculation and turbulence of cooling flow. Further, the fan, fan shroud and heat exchanger are optimally arranged relative to one another to reduce operating noise levels. Still other related objects and advantages of the present invention are apparent from the drawings and written description. For example, the present invention is also adaptable to provide a higher performance cooling flow system. For a given allowable operating noise level, the fan speed may be higher with the present invention over that of prior art cooling systems.

Claims

1. A cooling system (20,70,93) for use with an internal combustion engine (24), comprising:
   a fan (26,76,86,92) defining a central axis (38) for said cooling system (20,70), said fan (26,76,86,92) having an overall diameter and a projected axial chord width associated therewith;
   a heat exchanger (30,31,80,89) asymmetrical in shape about said central axis (38);
   a fan shroud (34,60,74,84,90) disposed about said fan (26,76,86,92) and defining a flow path for directing cooling flow across said heat exchanger (30,31,80,89), said fan shroud (34,60,74,84,90) including a radially converging inlet portion (40,63,91,94) and a transition portion (42,61,98), said radially converging inlet portion (40,63,91,94) being axisymmetrical in shape about said central axis (38); and
   a box-shaped plenum (36,88) sealingly connected between said fan shroud (34,60,74,84,90) and said heat exchanger (30,31,80,89), said box-shaped plenum (36,88) defining an abrupt transition with said fan shroud (34,60,74,84,90) between an asymmetrical shape corresponding to the asymmetrical shape of said heat exchanger (30,31,80,89) and an axisymmetrical shape corresponding to the axisymmetrical shape of said fan shroud (34,60,74,84,90).

2. The cooling system (20,70,93) of claim 1, wherein said fan shroud (34,60,74,84,90) further includes a radially diverging outlet portion (44,96), said radially converging inlet portion (40,63,91,94) and said radially diverging outlet portion (44,96) being axisymmetrical in shape about said central axis (38).

3. The cooling system (20,70,93) of claim 2, wherein said radially converging inlet portion (40,63,91,94) and said radially diverging outlet portion (44,96) are substantially symmetric with one another about an imaginary plane (49) constructed perpendicular to said central axis (38).

4. The cooling system (20,70,93) of claim 2, wherein said box-shaped plenum (36,88) is sealingly connected to said outlet portion (44,96) of said fan shroud (34,60,74,84,90).

5. The cooling system (20,70,93) of claim 1, wherein said fan (26,76,86,92) has a leading edge (48) and said radially converging inlet portion (40,63,91,94) and said transition portion (42,61,98) define a junction and an inlet plane (62) perpendicular to said central axis (38) and passing through said junction, said fan (26,76,86,92) being situated in said fan shroud (34,60,74,84,90) with said leading edge (48) aligned with said inlet plane (62).

6. The cooling system (20,70,93) of claim 1, wherein said box-shaped plenum (36,88) is sealingly connected to said inlet portion (40,63,91,94) of said fan shroud (34,60,74,84,90).

7. The cooling system (20,70,93) of claim 1, wherein said box-shaped plenum (36,88) is sealingly connected to said transition portion (42,61,98) of said fan shroud (34,60,74,84,90).

8. The cooling system (20,70,93) of claim 1, wherein said heat exchanger (30,31,80,89) is spaced a predetermined distance from said fan shroud (34,60,74,84,90) along said central axis (38), said predetermined distance being in the range of about 1.5 percent to about 10 percent of said overall diameter.

9. The cooling system (20,70,93) of claim 1, wherein said transition portion (42,61,98) has a predetermined axial length in the range of about 40 percent to about 85 percent of said projected axial chord width.

10. The cooling system (20,70,93) of claim 2, wherein said radially converging inlet portion (40,63,91,94) and said radially diverging outlet portion (44) each have a radius of curvature in the range of about 6 percent to about 10 percent of said overall diameter.

Drawing