Abstract:
A cooling fan for a vehicle. Many engine compartments of motor vehicles are small in size, and contain numerous components. Electric cooling fans are used to draw air through a radiator. Given the cramped conditions within the engine compartment, the exhaust of the fan cannot be directed into open air, but must impinge on one or more of the components within the compartment. This situation reduces velocity in the exhaust, and also reduces efficiency of the fan. The invention provides a collection of generally co-axial stators which divert the exhaust around the components, while retaining much of the velocity of the exhaust.

Description:
BACKGROUND OF THE INVENTION 
   In modern motor vehicles, the engine compartment is becoming increasingly crowded, primarily because of (1) the placement of additional components into the engine compartment, (2) the reduction in volume of the engine compartment, primarily to reduce overall aerodynamic drag of the vehicle, and many other factors. 
   The crowded nature of the compartment can cause problems in the operation of a cooling fan, such as that illustrated in  FIG. 1 . Fan  3  draws air  4  through a heat exchanger  6 , commonly termed a radiator, thereby cooling the liquid coolant within the radiator  6 . However, if, as on the right side of the Fig., an obstruction  9  is positioned within the exhaust of the fan  3 A, the obstruction  9  can reduce flow through the radiator, thereby reducing cooling. 
   The invention presents a stratagem for reducing the negative effects of the obstruction  9 . 
   SUMMARY OF THE INVENTION 
   An object of the invention is to provide an improved cooling fan for a vehicle. 
   A further object of the invention is to provide a cooling fan for a vehicle which operates efficiently in a confined environment. 
   In one form of the invention, stators are positioned in the exhaust stream of a cooling fan in a motor vehicle. The stators divert air into the radial direction, while increasing total airflow over the situation wherein the exhaust stream impinges on an obstacle it its path. 
   In one aspect, one embodiment comprises an apparatus, comprising: a cooling fan: draws cooling air through a radiator in a vehicle and expels exhaust air toward an obstacle; and a component positioned in the exhaust which increases efficiency of the fan by a measurable amount during at least some operating conditions of the cooling fan. 
   In another aspect, one embodiment comprises an apparatus, comprising: a generally axial-flow cooling fan which produces exhaust air in a vehicle; an obstacle present in the exhaust air, which diverts at least some of the exhaust air towards a radial direction, having a velocity above V 1  over a distance D 1 ; and means, present in the exhaust, for increasing V 1 . 
   In still another aspect, one embodiment comprises an apparatus, comprising: an axial-flow cooling fan in a vehicle comprising an obstruction downstream of the cooling fan which, together with a housing of the fan, forms a nozzle through which fan exhaust passes; and a plurality of stators between the cooling fan and the obstruction which divert fan exhaust into the nozzle, to increase average speed at the nozzle outlet. 
   In yet another aspect, one embodiment comprises an apparatus, comprising: a cooling fan which requires a torque T 1  to produce a flow F 1  in the absence of a predetermined downstream obstruction, and that requires a torque T 2 , higher than T 1 , to produce the flow F 1  in the presence of the downstream obstruction; and means for reducing the required torque below T 2 , to produce the flow F 1  in the presence of the downstream obstruction. 
   In yet another aspect, this invention comprises an apparatus, comprising: a cooling fan which requires a torque T 1  to produce a pressure rise P 1  across the fan disc in the absence of a predetermined downstream obstruction, and requires a torque T 2 , higher than T 1 , to produce the pressure rise P 1  in the presence of the downstream obstruction; and means for reducing the required torque below T 2 , to produce the pressure rise P 1  in the presence of the downstream obstruction. 
   In still another aspect, one embodiment comprises an apparatus, comprising: a vehicle having an engine compartment; a cooling fan within the engine compartment which blows air in an axial direction; and stator vanes which divert part of the air into a radial direction, but do not divert another component of the airflow. 
   In yet another aspect, one embodiment comprises an apparatus, comprising: a vehicle powered by a heat-producing engine; a fan having an axis and which cools an upstream heat exchanger which cools coolant used by the engine, and produces an exhaust stream; an obstacle in the exhaust stream which creates an unfavorable angle of attack within the fan; and a diverter means which diverts exhaust around the obstacle, to thereby improve the angle of attack within the fan. 
   In still another aspect, one embodiment comprises a method of designing a fan which (1) draws air through a heat exchanger in an engine compartment of a vehicle and (2) produces an exhaust stream which impinges on an obstacle which interferes with optimal operation of the fan, comprising: measuring, computing, or estimating first fan operating characteristics when a first set of vanes is present between the fan and the obstacle; and measuring, computing, or estimating second fan operating characteristics when a second set of vanes, different from the first set, is present between the fan and the obstacle. 
   In yet another aspect, one embodiment comprises an apparatus, comprising: a vehicle having an engine compartment; a fan which draws air through a heat exchanger which cools engine coolant; an obstruction downstream of the fan; and a means for reducing pressure loss of fan exhaust due to the obstruction. 
   In still another aspect, one embodiment comprises an apparatus, comprising: a vehicle having an engine compartment; a fan which draws air through a heat exchanger which cools engine coolant; an obstruction downstream of the fan; and a means for reducing disruption in streamlines within the fan caused by the obstruction. 
   These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a prior-art fan used to cool a component in a vehicle; 
       FIG. 2  illustrates the general location of the invention within the vehicle environment; 
       FIG. 3  illustrates a fan used in  FIG. 2 ; 
       FIGS. 4 and 5  illustrate one form of the invention; 
       FIG. 6  is a cross-sectional view of part of  FIG. 4  or  5 ; 
       FIG. 7  is a three-dimensional view of turning of air, which occurs in  FIG. 6 ; 
       FIG. 8  illustrates one of the stators of  FIGS. 4 and 5 , in perspective view; 
       FIGS. 9-12  are plots of velocities and pressure contours that illustrate effectiveness of the stator vanes of  FIGS. 4 and 5 ; 
       FIGS. 13-15  illustrate flow vs pressure, flow vs input torque, and efficiency of the invention; 
       FIG. 16  is a schematic of a blade B of a fan  200 ; 
       FIG. 17  is a vector diagram illustrating two airstreams  210  and  220  seen by blade B of  FIG. 16 ; 
       FIG. 18  illustrates the vector sum  225  of the vectors in  FIG. 17 ; 
       FIG. 19  illustrates how the vector sum  225  changes if the vector  220  changes; 
       FIG. 20  illustrates a velocity profile of air which encounters a blockage, in the absence of turning vanes; 
       FIG. 21  illustrates a velocity profile of air which encounters a blockage, with turning vanes V present; 
       FIG. 22  illustrates a standard cylindrical coordinate system; 
       FIGS. 23 ,  24 , and  26  illustrate different forms of the invention; 
       FIG. 25  illustrates two locations P 3  and P 6 , at the 3 o&#39;clock and 6 o&#39;clock positions, respectively; 
       FIG. 27  illustrates two sectors S 1  and S 2  in a fan; and 
       FIG. 28  illustrates vanes occupying part of sector S 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  illustrates a generalized motor vehicle  15 , which contains an element  18 , such as a gasoline engine, which requires cooling. Block  21  represents a cooling system, which is shown in greater detail in  FIG. 3 . 
   In  FIG. 3 , a fan  24 , which is preferably, but not limited, to being driven by an electric motor (not shown), and preferably runs at a relatively constant speed, draws airstreams  22  through a radiator  30 . An obstruction  33  can be present in the exhaust of the fan  24 . The invention utilizes stators  35  to divert air around the obstruction  33 . 
     FIGS. 4 and 5  illustrate one type of fan  24  that can be used. Stators  36  are present in the exhaust of the fan  24  and function to turn the axial component and increase the radial component of the fan exhaust, as indicated in  FIG. 6 . It is emphasized that  FIG. 6  is a fragmentary cross-sectional view;  FIG. 7  illustrates the turning accomplished by the stators  36  in perspective view. 
     FIG. 8  illustrates a perspective view showing a cutaway drawn in wire frame illustration which is contained to show a cut away of one of the stators  36 , but in exaggerated scale: the solid metal/plastic cross section is enlarged with respect to the diameter, to more clearly show the shape of the cross section. 
   As  FIG. 6  indicates, the stators  36  can take the form of circular arcs, spanning 90 degrees, for example. 
     FIGS. 9-15  set forth test results and simulation results which illustrate selected properties of an embodiment of the invention.  FIGS. 9-12  are tracings of digital computer maps produced by simulation software, and are thus approximate illustrations. 
     FIGS. 9 and 10  illustrate a cross section of the annular operating region of the fan blade  45 , showing the exit plane of the fan blades themselves and an obstruction  48  which is downstream of the annular fan blade region. Wall section  51  of the obstruction  48  can be viewed as cooperating with wall section  54 , to thereby form a radial exit flow path for the fan exhaust flow. 
     FIG. 9  illustrates profiles of total pressure within the system in relative units. Total pressure includes a static component and a dynamic component. A scale of relative pressures is shown as the column of numbers, with 79.00 at the top. 
   To aid in showing overall patterns, the arrows leading from the scale of relative pressures are labeled with round numbers, such as 1, 15, 35, and so on. These round numbers represent convenient approximate values. For example, the arrow labeled 60 originates at a point between 52.14 and 65.57 on the scale. The number 60 is a convenient intermediate value between those two numbers. 
   Two significant features of  FIG. 9  are that (1) the highest pressure region (labeled 70) abuts the obstruction, and (2) the pressures diminish in the radial direction, as the sequence 60, 50, 35, and 15 indicates. 
     FIG. 10  is a plot similar to  FIG. 9 , but with the stator vanes V present. The highest pressure regions (labeled 70) lie on the concave sides of the vanes V. 
   Significantly, in  FIG. 10 , the region of next-highest pressure, that labeled 55, extends significantly farther outward in the radial direction than the corresponding region in  FIG. 9 , and the third pressure region, that labeled 40, extends virtually to the outer boundary  100 . 
   Stated more precisely,  FIG. 9  indicates that at the radially outermost point from the flow regime, pressure has dropped from about 70 to about 15 in positive units, or to about 20 percent of the maximal value of 70. In contrast,  FIG. 10  indicates that the analogous pressure drop is to only about 40 units, which is about 60 percent of the maximal value. 
   Thus, under the invention, high total pressure is sustained for a longer radial distance from the fan tip diameter, compared with the case of  FIG. 9 . 
     FIGS. 11 and 12  are similar to  FIGS. 9 and 10 , but illustrate velocity maps. In  FIG. 11 , the highest velocity is just above 11.07 units, and drops to just above 5.34 units at the radially farthest point from the fan tip diameter region N. 
   In  FIG. 12 , in which the stator vanes V are present, the highest velocity is higher, at above 12.12 units, compared with  FIG. 11 . Further, the triangular region in  FIG. 12  labeled with a value of about 11.02, and extending to the radially outermost flow region  105 , has a value about equal to the highest velocity in  FIG. 11 . 
   That is, the highest velocity in  FIG. 11  has a certain value, but which drops to about half that value at the radially outermost flow region  105 . In contrast, the vanes in  FIG. 12  produce a higher velocity, at roughly the same location, and at least 80 percent of that velocity (about 11.02/12.12) is sustained at the region  105 . 
   The invention of  FIG. 12  delivers a higher velocity air stream, such as that indicated as about 11.02 relative units in  FIG. 12 , for a longer radial distance than does the apparatus of  FIG. 11 , as a comparison of the region labeled 9.97 in  FIG. 11  with that labeled 11.02 in  FIG. 12  indicates. 
     FIGS. 13-15  provide additional test results. Three cases were considered in each plot, namely (1) a physical situation similar to that of  FIGS. 9-12 , but with no stators present, and no obstruction present (that is, with both stators and downstream blockage absent), (2) a similar physical situation, but with no stators present, but with the obstruction present (that is, with the ring stator absent), and (3) a similar physical situation, but with stators present and the obstruction present (that is, with the ring stators present). 
     FIG. 13  is a plot of non-dimensional pressure rise coefficient against non dimensional flow coefficient. The pressure coefficient is the ratio of fan static pressure rise divided by both fan RPM and Tip diameter squared. The Flow coefficient is the ratio of the airflow divided by both the speed and fan tip diameter. These coefficients convenient non-dimensional groupings that relate directly to measured static pressure rise and airflow performance. 
   These convenient non-dimensional groupings allow plots of different experimental setups to be compared directly. For example, if a different fan speed were used or a fan of a different diameter, the plots of those two situations could be compared directly with that of  FIG. 13 . 
     FIG. 13  shows that in all cases for a flow rate exceeding about 0.16, the invention provides a higher pressure rise. This pressure rise is a figure-of-merit for the type of fan in question, and the increase in pressure rise indicates better performance, particularly in view of the reduction in torque required to obtain that increase in pressure rise comparing the without vs with ring stator condition for operation above 0.225 flow coefficient. 
   The pressure rise drops as flow increases because, as flow increases, the dynamic component of the total pressure becomes larger. Because the Fig. reports static pressure, static pressure drops as flow increases. 
     FIG. 14  is a plot of torque drawn by or applied to the fan  24  by the motor driving the fan  24 . Plot  120  indicates that, with no stators nor obstruction present, the torque behavior drops as flow increases. 
   Plot  125  indicates that, with the obstruction present, but no stators present, torque remains somewhat constant, with a slight rise at about 0.22 units of flow coefficient. 
   Plot  130  indicates that, with the obstruction present and the stators installed, torque drawn form the motor is about the same as for plot  125 , up to about 0.21 units of flow coefficient. Then, torque behavior drops. 
     FIG. 15  is a plot of efficiency against flow coefficient.  FIG. 15  can be derived from  FIGS. 13 and 14 . From a broad view,  FIG. 13  indicates the power produced by the fan.  FIG. 14  indicates the power required by the fan. Thus, a comparison of power produced with power required provides a measure of efficiency. 
   More precisely, efficiency is computed as (P*F)/T
         wherein   P is the pressure coefficient in  FIG. 13 ,   F is the flow coefficient in  FIGS. 13 ,  14 , and  15 , and   T is the torque coefficient in  FIG. 14 .       

   For example, for a flow coefficient F of 0.2, the pressure coefficient P in  FIG. 13  is about 0.075, for the case without both obstruction and stators. The torque coefficient T in  FIG. 14  is about 0.029. (P*F)/T equals about (0.075*0.2)/(0.029). Since the quotient 0.075/0.029 is just under 3.0, the answer is under 0.6, consistent with  FIG. 15 . 
     FIG. 15  indicates that efficiency of the configuration with both blockage and ring stators increases for all flow coefficients exceeding 0.16. Further, the amount of the increase is obtained from plots  150  and  155 . The increase at point P 1  is from about 0.1 to 0.3, or by about 300 percent. The increase at point P 2  is from about 0.25 to 0.4, or by about 160 percent. The increase at point P 3  is from about 0.42 to about 0.52, or about 125 percent. 
   A significant comparison can be made between curves  155  and  150 . The condition without both stators and blockage is a curve of interest, but does not relate to an installed vehicle condition. Curve  150  shows higher efficiency than curve  155  for flow coefficient levels above 0.16. Typical on vehicle operating range for cooling fans of this type ranges from 0.16 at an idle condition to above 0.30 at higher vehicle speed operation. The combination of stators with the downstream blockage provides benefit throughout the entire on vehicle operating range 
   In one mode of operation, it is contemplated that the fan  24  operate above a flow coefficient of 0.25 at least 90 percent of the time. 
   Additional Considerations 
   1. The invention improves efficiency of the cooling system.  FIG. 16  illustrates a generalized fan  200  which produces an exhaust stream  201 . A single blade B is shown, which rotates in direction  205 . 
     FIG. 17  is a cross section of blade B. Arrow  210  represents the incoming air velocity seen by the blade B, due to rotation alone. The action of the fan  200  itself induces an axial component of inlet flow velocity represented by arrow  220 . The magnitude of arrow  220  with respect to arrow  210  will increase with increasing vehicle speed which by the action of higher levels of ram flow admitted by the fan  200 . 
   The net incoming air seen by the blade B is the vector sum of the two components  210  and  220 , indicated in  FIG. 18 . In general, for (1) a given rotational speed, which determines vector  210 , and (2) a given vehicle speed, which determines vector  220 , one (or more) specific blade shapes provide optimal efficiency of the fan  200 . 
   However, the presence of the obstacle disrupts this optimal efficiency. While the particular mechanism of the disruption is complex, a simplified view is that the obstacle reduces the velocity of the air flowing through the fan  200 . The disruption can be viewed as reducing the size of vector  220 , as indicated in  FIG. 19 . The vector sum  225  is now different. The changes to the vector sum  225  can vary greatly depending on the location along the blade hub to tip span and the location and nature of the downstream obstacle. 
   In general, the fan  200  was not designed for this different vector  225 , and efficiency is reduced. 
     FIGS. 20 and 21  are simulations illustrating how the invention mitigates the loss in efficiency caused by the obstacle. In  FIG. 20 , with no vanes present, the 5.5 meter-per-second profile line  230  is indicated. Arrow  235  points to a region where this velocity has been lost. 
   In contrast, in  FIG. 21 , with vanes V present, the velocity in that region is not reduced so greatly. Flow through the fan is maintained more closely to the optimal value. 
   2. The vanes in cross section can assume airfoil shapes. These shapes can be different at different circumferential locations around the fan. 
     FIG. 22  illustrates the fan  200 , together with a polar coordinate system superimposed thereon. A z-axis is shown. The radial coordinate, r, is the distance from the z-axis. The angle theta is measured from a reference line  250 . Point P, for example, has the coordinates (r, theta, z) of (4, 0, 10). 
   In general, the shapes of the vanes can be different at different coordinates. For example, in  FIG. 23 , vane V 1  has a chord length C 1 , while vane V 2  has a chord length C 2 . Different vanes can also have different axial lengths AX or different radial depths RD. 
   In  FIG. 24 , vane V 5  has an inlet angle A. Vane V 6  has a different inlet angle of zero. Vane V 7  has an exit angle of ninety degrees. Vane V 8  has a different exit angle A 2 . 
   In one embodiment, the inlet angles, or exit angles, or both, can be similar at similar angles theta, but at different angles theta, they can differ. For example, in  FIG. 25 , the angles in question can be similar at the 3 o&#39;clock position P 3 . The angles in question can also be similar at the 6 o&#39;clock position P 6 , but the former can be different from the latter. 
   In addition, the similar angles can span a range of positions. For example, the angles in question can be similar from 3 o&#39;clock to 6 o&#39;clock. 
   In  FIG. 26 , three vanes V are shown. The radial distance R 1  between adjacent vanes V 10  and V 11  is different from the radial distance R 2  between adjacent vanes V 11  and V 12 . 
   In a related type of difference, the channel width W between different pairs of vanes is different: different pairs define different channel widths. The channel width W need not be constant. Thus, an average width can be considered, or the minimum or maximum width. 
   Similarly, an annulus can be defined in the exhaust of the fan. An annulus is a band between two circles of different diameter. For example, the rings of Saturn form an annulus. In one form of the invention, vanes can be present in all or part of an annulus of given inner diameter, but vanes may be absent from other annuli. 
   In  FIG. 27 , vanes can be present in one sector S 1 , but absent from another sector S 2 . In  FIG. 28 , vanes can be partially present in sector S 1 , as indicated by the hatching, which indicates the presence of vanes. 
   Therefore, in general, the airfoil shape of the vanes can be different, at different coordinates (r, theta, z). The difference includes the absence of vanes entirely at certain coordinates. The parameters of airfoil shape, such as chord length, thickness, inlet angle, and exit angle, are defined in the art of aerodynamics. As stated, these parameters can vary over the (r, theta, z) space. 
   Also, the vanes in the sector which covers the obstacle can be designed differently from vanes in other sectors. For example, in  FIG. 28 , the obstacle O is represented. Sector S 1  covers the obstacle. 
   3. The vanes can be ring-shaped, with the larger-diameter rings closer to the fan, and the smaller-diameter rings farther from the fan. 
   4. In one embodiment, radial struts generically indicated by dashed block  300  in  FIG. 24  support the vanes. 
   In many types of fans, such radial struts are shaped to re-direct exhaust air generated by the fan. For example, in  FIG. 22 , because of the rotation indicated by arrow  205 , the airstream generated by the fan will have a velocity component in the tangential direction. The radial struts are shaped to re-direct this tangential air into the axial direction, that is, parallel with the z-axis. 
   In one form of the invention, this re-direction does not occur, is not desired, and the radial struts are not designed to perform this re-direction. 
   It is recognized that any time an object is placed in a flow stream, some re-direction will occur. For example, if a flow stream is moving East, and encounters an object, part of the flow stream will flow North, part South, and part upward. 
   Similarly, if a flow stream generated by a fan encounters a radial strut, part of the flow stream will flow slightly tangentially, to avoid the strut. 
   Nevertheless, under the form of the invention in question, the struts are not designed to enhance or decrease this minimal amount of tangential flow. Stated another way, the impact on tangential flow is sought to be minimal, and the radial struts designed accordingly. 
   5. The fan-vane system is designed to be mounted within an engine compartment of a vehicle. Block  350  in  FIG. 22  represents a mounting means. For example, the mounting means can take the form of three flanges, each having a bolt hole, the bolt holes defining a triangle. With such three-point mounting, flexing of the vehicle does not impart torsion to the fan. 
   That is, with four-point mounting, the four points define a quadrilateral, such as a rectangle. Assume that the rectangle is vertical, facing south, and the two lower corners are anchored. If the left upper corner moves north, and the right upper corner moves south, then torsion is applied to the rectangle. 
   Such torsion does not occur in three-point mounting. 
   Numerous substitutions and modifications can be undertaken without departing from the true spirit and scope of the invention. What is desired to be secured by Letters Patent is the invention as defined in the following claims.