SYSTEM AND METHOD FOR CONTROLLING FAN AIRFLOW

BACKGROUND

[0001] The invention relates generally to fan assemblies, and more specifically to axial flow fan assemblies.

[0002] Axial flow fans generally comprise a plurality of radial blades rotating within a shroud. Increasing performance demands on axial flow fans have required that fans provide increased volumes of air while, at the same time, reducing the size of the fan. One solution to increasing fan performance is simply to increase the speed at which the fan rotates. Increasing fan speed can also be accompanied by increased acoustic emissions, increased vibration, and decreased component life. Therefore, as can be appreciated, there remains a need in the art for cooling fans that provide high volumes of airflow by designs and improvements that increase performance without necessitating an increase in the speed at which fan operates.

BRIEF DESCRIPTION

[0003] In accordance with an embodiment of the invention, a system is provided. The system includes an axial flow fan assembly. The axial flow fan assembly includes a shroud and a fan, wherein the shroud and the fan are configured to move in relation to one another along a direction normal to a plane of rotation of the fan. The axial flow assembly further includes at least one sensor configured to sense an ambient parameter related to airflow through the fan. The axial flow assembly also includes a device configured to receive a sensing signal from the at least one sensor and to dynamically control a design parameter related to the airflow in response to the signal.

[0004] In accordance with an embodiment of the invention, a method is provided. The method includes disposing an axial flow fan assembly comprising a shroud and a fan and configuring the shroud and the fan to move in relation to one another. The method further includes determining at least one ambient parameter related to airflow through the fan assembly. The method also includes optimally configuring a design parameter related to the airflow. The method further includes dynamically controlling the design parameter in response to the ambient parameter.

[0005] In accordance with an embodiment of the invention, a system is provided. The system includes an axial flow fan assembly. The axial flow fan assembly includes a shroud and a fan, wherein the shroud and the fan are configured to move in relation to one another. The axial flow fan assembly further includes a device configured to control at least one design parameter related to airflow through the fan assembly.

DRAWINGS

[0006] These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0007] FIG. 1 is diagrammatical representation of a system for controlling fan airflow in accordance with an embodiment of the present invention.

[0008] FIG. 2 is diagrammatical representation of a system for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0009] FIG. 3 is diagrammatical representation of a system for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0010] FIG. 4 is diagrammatical representation of a system for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0011] FIG. 5 is a flow chart of the control logic for operation of the system of FIG. 1 for controlling fan airflow in accordance with an embodiment of the present invention.

[0012] FIG. 6 is a diagrammatical representation of clearance modification for controlling fan airflow in accordance with an embodiment of the present invention.

[0013] FIG. 7 is a diagrammatical representation of clearance modification for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0014] FIG. 8 is a diagrammatical representation of clearance modification for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0015] FIG. 9 is a diagrammatical representation of shroud modification for controlling fan airflow in accordance with an embodiment of the present invention.

[0016] FIG. 10 is a diagrammatical representation of shroud modification for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0017] FIG. 11 is a diagrammatical representation of the functional relationship between simulation studies in airfoil geometry and airflow characteristics in accordance with an embodiment of the present invention.

[0018] FIG. 12 is a diagrammatical representation of the functional relationship between simulation studies in airfoil geometry and airflow characteristics in accordance with an alternative embodiment of the present invention.-13

[0019] FIG. 13 is a diagrammatical representation of the functional relationship between simulation studies in airfoil geometry and airflow characteristics in accordance with an alternative embodiment of the present invention.

[0020] FIG. 14 is a diagrammatical representation of the functional relationship between simulation studies in airfoil geometry and airflow characteristics in accordance with an alternative embodiment of the present invention.

[0021] FIG. 15 is a diagrammatical representation of blade twist modification for controlling fan airflow in accordance with an embodiment of the present invention.

[0022] FIG. 16 is a diagrammatical representation of blade twist modification for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0023] FIG. 17 is a diagrammatical representation of effective blade power reduction for controlling fan airflow in accordance with an embodiment of the present invention.

[0024] FIG. 18 is a diagrammatical representation of effective blade power reduction for controlling fan airflow in accordance with an alternative embodiment of the present invention.

[0025] FIG. 19 is a diagrammatical representation of the functional relationship between simulation studies in airfoil geometry and flow performance of fan in accordance with an embodiment of the present invention.

[0026] FIG. 20 is a diagrammatical representation of functional relationship between speed of fan and power of fan for various airfoil designs in accordance with an embodiment of the present invention.

[0027] FIG. 21 is a flow chart for a method for controlling fan airflow in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

[0028] When introducing elements of various embodiments of the present invention, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters are not exclusive of other parameters of the disclosed embodiments.

[0029] In accordance with the embodiments of the present invention, a fan assembly is disclosed. The exemplary fan assembly includes an axial flow fan assembly comprising a shroud and a fan. The shroud and the fan are configured to move in relation to one another along an axial direction normal to a plane of rotation of the fan. The fan assembly also includes at least one sensor configured to sense an ambient parameter related to airflow through the fan. The fan assembly further includes a device configured to receive a sensing signal from the at least one sensor and to dynamically control a design parameter related to the airflow in response to the signal. A number of control measures may be used to control the flow of air through the fan as detailed below.

[0030] FIG. 1 is a diagrammatical representation of a system for controlling fan airflow in accordance with an embodiment of the present invention. The system includes a fan assembly 10. Fan assembly 10 further includes a shroud 12 and a fuci 14. A number of blades 18 are typically fixed to the hub 16 of the fan 12. The fan 14 typically rotates about an axis of rotation 25. Typically, there is a gap left between the shroud 12 and the tips 22 of the blades 18. These gaps are technically defined as tip clearance.

[0031] Referring to FIG. 1 again, there is a clearance modification unit 42 that modifies the clearance between the shroud 12 and the tips 22 of the blades 18 according to various design needs as will be explained in greater details subsequently. It is through the tip clearance 24 between the fan blade tips 22 and the shroud 12 and additionally through the intervening space between the plurality of blades 18 that airflow 28 takes place. Referring to FIG. 1 again, there is airflow path modification unit 32 that modifies various design parameters of the shroud 12 and blades 18 according to various design needs in order to modify the flow path as will be explained in greater details subsequently.

[0032] The fan assembly 10 in FIG. 1 further includes a fan-shroud motion mechanism 52 that moves the shroud 12 and the fan 14 in relation to one another along the axis of rotation 25. The axis 25 typically coincides with a direction normal to a plane of rotation of the fan. The fan-shroud motion mechanism 52 further includes a fan-shroud gear train 54 that causes the relative motion between the shroud 12 and the fan 14. In one embodiment of the invention, a first motion transmission line 56 transmits the motion generated by gear train 54 to the shroud 12 and consequently the shroud 12 moves along axis 25 while the fan 14 remains stationary. In another embodiment of the invention, a second motion transmission line 58 transmits the motion generated by gear train 54 to the fan 14 and consequently the fan 14 moves along axis 25 while the shroud 12 remains stationary. In yet another embodiment of the invention, both shroud 12 and fan 14 may move in relation to one another.

[0033] Referring to FIG. 1 again, the fan assembly 10 further includes an ambient parameters sensing unit 72. The ambient parameters sensing unit 72 includes a temperature sensor 74 and a pressure sensor 76. The fan assembly 10 further includes a fan speed control unit 82 that controls the speed of the fan 14 in accordance with the design needs of the fan assembly 10 as will be explained in greater details subsequently.

[0034] In one further embodiment of the invention as represented in FIG. 1, the system 10 includes a control unit 62 that is configured to control various components of the fan assembly 10. In one embodiment, the control unit 62 is an electronic fan control unit for the fan assembly 10. In another embodiment, the control unit 62 is an electronic logic controller that is programmable by a user. The control unit 62 may be operable to control operation of flow-path modification unit 32, clearance modification unit 42, fan-shroud motion unit 52, temperature sensor 74, pressure sensor 76 and speed control device 82 so as to optimize the flow of air through the fan assembly 10. In some embodiments, the control unit 62 may control the plurality of components flow-path modification unit 32, clearance modification unit 42, fan-shroud motion unit 52 and speed control device 82 based on output either from the temperature sensor 74 or from the pressure sensor 76 or from both.

[0035] In some other embodiments, the control unit 62 may further include a database 64, an algorithm 66, and a data analysis block 68. The database 64 may be configured to store predefined information about the fan assembly 10. For example, the database 64 may store information relating to fan assembly flowrate, temperature, and pressure and the like related to the fan assembly 10. Furthermore, the database 64 may be configured to store actual sensed/ detected information from the above- mentioned sensors. The algorithm 66 may facilitate the processing of signals from the above-mentioned plurality of sensors.

[0036] In one embodiment of the invention the flow-path modification unit 32, the clearance modification unit 42, the fan-shroud motion unit 52, the temperature sensor 74, the pressure sensor 76, the speed control device 82 and the control unit 62 operate as integral part of the fan assembly 10. In another embodiment of the invention, the combination of the flow-path modification unit 32, the clearance modification unit 42, the fan-shroud motion unit 52, the temperature sensor 74, the pressure sensor 76, the speed control device 82 and the control unit 62 may work as a retrofit airflow control device 92. One such retrofit system may be installed, operated and maintained as a stand-alone system in connection with the operation of the system. FIG.s 2, 3 and 4 are diagrammatical representations of the system in FIG. 1 for controlling fan airflow in accordance with alternative embodiments of the present invention and corresponding numerals represent corresponding parts.

[0037] FIG. 5 is a flow chart of the control logic for operation of the system of FIG. 1 for controlling fan airflow in accordance with an embodiment of the present invention. The control logic 200 describes how the airflow through fan assembly 10 is controlled using a control unit such as the one (62) represented in FIG. 1. One such control unit 62 typically controls multiple components of the fan assembly 10 such as the flow-path modification unit 32, the clearance modification unit 42, the fan-shroud motion unit 52, the temperature sensor 74, the pressure sensor 76 and the speed control device 82. The control logic starts at step 202. The logic includes step 204 for determining local temperature (TLOC)- In step 206, the cooling load required of the fan assembly 10 is estimated and Tcutoff, the threshold minimum desired value of TLOC is determined. In step 208, it is determined whether Tux: is less than Tcut0fr. If TLOC is more than Tcut0ff, operation is stopped as in step 228. If TLOC is less than Tcut0fr, further control in airflow is desired as in step 212. At step 212, a first combination of control measures is carried out. As part of the first combination of control measures, tip clearance between the tips of the blades of the fan and the shroud is dynamically controlled as in step 213 in one embodiment of the invention. This step is explained in more details with the help of FIG. 3 and FIG. 4 below.

[0038] FIG. 6 is a diagrammatical representation of the working of the clearance modification unit 42 for controlling fan airflow 28 in accordance with one embodiment of the present invention. Specifically, FIG. 6 diagrammatically represents a baseline configuration of the clearance modification unit 42. Referring to FIG. 6, the fan blade 18 of FIG. 1 is attached to hub 16 of FIG. 1. As already described in FIG. 1, typically there remains a clearance between the blade tip 22 and the shroud 12. Moreover, the tip clearance between the blade tip 22 and the shroud 12 varies from the leading edge of blade 18 to the trailing edge of blade 18 in a non uniform manner. More specifically, the clearance 26 at the leading edge is more than the clearance 24 at the trailing edge of blade 18.

[0039] FIG. 7 diagrammatically represents a modified configuration of the clearance modification unit 42 in accordance with one embodiment of the invention. Referring to FIG. 7, the fan blade 18 of FIG. 1 is attached to hub 16 of FIG. 1. The blade tip 102 of the blade 18 is a modified configuration of the blade tip 22 of FIG. 1 and FIG. 6. More specifically, blade tip 102 follows the profile and the curvature of the shroud 12 after profiling such that the tip clearance is uniform from the leading edge of blade 18 to the trailing edge of blade 18. More specifically, the clearance is equal in magnitude from the leading edge 106 of the blade 18 to the trailing edge 104 of the blade 18.

[0040] FIG. 8 diagrammatically represents an extreme condition of the modified configuration of the clearance modification unit 42 in accordance with another embodiment of the invention. Referring to FIG. 8, the fan blade 18 of FIG. 1 is attached to hub 16 of FIG. 1. The blade tip 112 of the blade 18 is a modified configuration of the blade tip 22 of FIG. 1 and FIG. 6. More specifically, blade tip 112 follows the profile and curvature of the shroud 12 after profiling such that zero clearance exists from the leading edge 116 of the blade 18 till the trailing edge 114 of the blade 18. In one such extreme configuration, there is no tip clearance between the tips of the blades 18 and the shroud 12. Thereby, there is no space for leakage airflow to take place. Operationally, this sets the limit for the modification described in relation to FIG. 7.

[0041] In one embodiment of the invention, the clearance modification unit 42 operates on the blade tips as described above. In another embodiment of the invention, the clearance modification unit 42 operates on the clearance by modifying the shroud as described below. FIG. 4 is a diagrammatical representation of the working of the clearance modification unit 42 for controlling fan airflow 28 in accordance with one embodiment of the present invention. Specifically, FIG. 9 diagrammatically represents a configuration that includes modification of the shroud 12 (FIG. 1) for controlling airflow 28 through fan 14 in accordance with an embodiment of the present invention. Referring to FIG. 9, the fan blade 18 of FIG. 1 is attached to hub 16 of FIG. 1. In one embodiment of the invention the blade tip 122 of blade 18 is same as the blade tip 22 of FIG. 1 and FIG. 6. In another embodiment of the invention, the blade tip 122 of blade 18 is the modified configuration 102 of the blade tip as in FIG. 7. Referring to FIG. 9, the cylindrical portion and the radius of curvature of the curved (bell-like) portion of the shroud 12 are maintained in a way such that the clearance at the trailing edge 124 of the blade 18 and the clearance at the leading edge 124 of the blade 18 are equal in magnitude. Typically, this is technically achieved by ending the bell-like portion 127 of the shroud at the leading edge of the blade followed by the cylindrical portion 128 of the shroud extending till the trailing edge of blade 18.

[0042] FIG. 10 diagrammatically represents an alternative configuration of modification of the shroud 12 (FIG. 1) for controlling airflow 28 through fan 14 in accordance with another embodiment of the present invention. Referring to FIG. 10, the fan blade 18 of FIG. 1 is attached to hub 16 of FIG. 1. In one embodiment of the invention the blade tip 132 of blade 18 is same as the blade tip 22 of FIG. 1 and FIG. 6. In another embodiment of the invention, the blade tip 132 of blade 18 is the modified configuration 102 of the blade tip as in FIG. 7. Referring to FIG. 10, the cylindrical portion of shroud 12 is maintained till a length below the blade tip leading edge such that clearance at the leading edge is maintained equal through till clearance at the trailing edge of the blade 18. Thus, clearance 136 at the leading edge of the blade 18 is equal in magnitude to clearance 134 at the trailing edge of the blade 18, Typically, this is technically achieved by extending the cylindrical portion 138 upward beyond the blade tip trailing edge and extending the curved bell-like part 137 downward, with the starting point of curvature at a point below the leading edge of the blade 18.

[0043] Referring to FIG. 5 again, in another embodiment of the invention, shroud and fan may be moved relative to one-another along an axis normal to the plane of rotation of the fan as in step 214 in order to control airflow 28 (FIG. 1). As described previously, the fan assembly 10 in FIG. 1 further includes a fan-shroud motion mechanism 52 that moves the shroud 12 and the fan 14 in relation to one another along the axis of rotation 25. In one embodiment of the invention, the shroud 12 moves along axis 25 while the fan 14 remains stationary. In another embodiment of the invention, the fan 14 moves along axis 25 while the shroud 12 remains stationary. In yet another embodiment of the invention, both shroud 12 and fan 14 may move in relation to one another.

[0044] Referring to FIG. 5 again, in one further embodiment of the invention, effective flow-path of the airflow is dynamically modified as in step 216 as in FIG. 5 and FIG. 6 below in order to control airflow 28 (FIG. 1). FIG. 5 is a diagrammatical representation of the functional relationship between simulation studies of airfoil geometry and airflow characteristics in accordance with an embodiment of the present invention. Specifically, FIG. 11 is a diagrammatical representation of the working of the flowpath modification unit 32 for controlling fan airflow 28 in accordance with one embodiment of the present invention. Referring to FIG. 11, a set of curves 150 diagrammatically represents airfoil profiles for various simulation studies. The two dimensional curves 155, 156, 157 and 158 are drawn on a horizontal dimension of airfoil profile 152 and a vertical dimension of airfoil profile 154. Of these, curve 155 represents an exemplary baseline airfoil profile. Of the other curves, 156 represents an exemplary airfoil profile A, 157 represents an exemplary airfoil profile C and 1.18 represents an exemplary airfoil profile B.

[0045] FIG. 12 is a diagrammatical representation of the geometric details of the exemplary airfoil profile B in accordance with one embodiment of the present invention as illustrated in FIG. 11. Referring to FIG. 12, the two dimensional curve 158, representing exemplary airfoil profile B, is drawn on the horizontal dimension of airfoil profile 152 and the vertical dimension of airfoil profile 154. Referring to FIG. 12, a horizontal line 163 joins the leading edge 160 and the trailing edge 162 of the airfoil profile B and is typically known as the Chord. Further, the linear distance between the leading edge 160 and the trailing edge 162 is called the Chord-length of the airfoil profile B. The radius of curvature at the leading edge 160 is called leading edge radius and the respective circle 159 is called leading edge circle. Similarly, the radius of curvature at trailing edge 162 is called trailing edge radius and the respective circle 161 is called trailing edge circle. Further, a curve 164 extends from the leading edge 160 to the trailing edge 162 and represents the Camber-line of the airfoil profile B. This line bisects the upper and lower curves of the airfoil in a direction perpendicular to the chord. The perpendicular distance from any point on the chord and a corresponding point on the camber line is technically known as the Camber of the airfoil profile B at that point. Referring to FIG. 12 once more, maximum thickness 166 of the airfoil profile B occurs at a linear distance 167 from the leading edge along line 163. Further, maximum camber 168 of the airfoil profile B occurs at a linear distance 169 from the leading edge along line 163.

[0046] Airfoil profile B has been designed and simulated to achieve optimal improvement in airflow over input power, speed and blade-twist corresponding to the baseline conditions. In one such optimal configuration, profile B typically achieves 23% improvement in airflow while maintaining input power, speed and blade-twist corresponding to the baseline conditions. Further, referring to FIG. 12, in one such optimal configuration, the radius of the leading edge circle 159 is typically about 1.55% of the chord length 165 with +/- 0.2% range variability; the radius of the trailing edge circle 160 is typically about 1% of the chord length 165 with +- 0.2% range variability. Further, in one such optimal configuration, the maximum thickness 166 is typically about 13.6% of the chord length 165 with +- 2% range variability and the maximum thickness 166 typically occurs at a location 167 corresponding to about 33%> of the chord length 165. Further, in one such optimal configuration, the maximum camber 168 is typically about 6.58% of the chord length 165 with +-2% range variability and the maximum camber 168 typically occurs at a location 169 corresponding to about 49% of the chord length 165.

[0047] FIG. 13 is a diagrammatical representation of the working of the flowpath modification unit 32 for controlling fan airflow 28 in accordance with another embodiment of the present invention. Referring to FIG. 13, a set of curves 170 diagrammatically represents airflow characteristics of first type for various simulation studies. The two dimensional curves 175, 176, 177 arid 178 are drawn on a horizontal dimension of airflow characteristics 'Angle of attack' 172 and a vertical dimension of airflow characteristics 'Coefficient of lift' (CL) 174. Of the curves, curve 175 represents an exemplary baseline airflow characteristic. Of the other curves, 176 represents an exemplary airflow characteristics for Airfoil Profile A, 177 represents an exemplary airflow characteristics for Airfoil Profile C and 178 represents an exemplary airflow characteristics for Airfoil Profile B. Referring to FIG. 13, the airfoil profiles signify that the maximum coefficient of lift for all airfoil profiles for analytical simulation studies are higher than the maximum coefficient of lift value fcr the baseline profile. In other words, the analytical simulation studies as disclosed herein report significant improvement over the baseline characteristics.

[0048] FIG. 14 is a diagrammatical representation of the working of the flowpath modification unit 32 for controlling fan airflow 28 in accordance with another embodiment of the present invention. Referring to FIG. 14, a set of curves 190 diagrammatically represents airflow characteristics of second type for various simulation studies. The two dimensional curves 195, 196, 197 and 198 are drawn on a horizontal dimension of airflow characteristic 'Angle of attack' 192 and a vertical dimension of airflow characteristics 'Lift to drag ratio' (L/D) 194. Of these, curve 195 represents an exemplary airflow characteristic of a baseline profile. Of the other curves, 196 represents an exemplary airflow characteristic for Airfoil Profile A, 197 represents an exemplary airflow characteristic for Airfoil Profile C and 198 represents an exemplary airflow characteristic for Airfoil Profile B. The profiles signify that for a higher lift to drag ratio and higher coefficient of lift, the range of operability is maximum for Airfoil Profile B. Therefore, in one embodiment of the invention, Airfoil Profile B is selected as the optimum configuration for operation.

[0049] FIG. 15 is a diagrammatical representation of blade twist modification for controlling fan airflow in accordance with an embodiment of the present invention. Specifically, in FIG. 15, the representative sketch 300 represents a visualization of the extent of twist of an exemplary blade 306 having baseline profile. Typically, the length of a blade between the hub side and the shroud side is technically known as blade-span of the blade. Further, twist of a blade is typically characterized in terms of two parameters - an angle of twist of the blade and the length percentage (%) of the blade-span that has the twist. Referring to FIG. 15, in one embodiment of the invention, between the hub side 302 and the shroud side 304 of baseline blade 306, a length of about 40% of the blade-span, measured from the hub side 302 may include minimal angle of twist. Further, referring to FIG. 16, the representative sketch 320 represents a visualization of the extent of twist of an exemplary twisted blade 326. In one embodiment of the invention, between the hub side 322 and the shroud side 324 of the twisted blade 326, the entire blade-span of the twisted blade 326 is configured to include a twist such that the angle of twist is higher in value than the minimal angle of twist existing for the baseline blade 306. Increasing the extent of twist in the fan blade, as mentioned herein, typically results in a flow incidence that helps in increasing the lift and thereby the lift to drag ratio of the blades and thereby the performance of the fan as a whole.

[0050] Referring to FIG. 5 again, in yet another embodiment of the invention, effective blade power may be dynamically reduced as in step 218 and in FIG. 7 below. FIG. 17 is a diagrammatical representation of effective blade power reduction for controlling fan airflow in accordance with an embodiment of the present invention. Specifically, in FIG. 17, the representative sketch 400 represents the blade taper visualization for an exemplary baseline blade 18 vis-a-vis an exemplary tapered blade 402. The tapered blade 402 is attached to hub 16 of FIG. 1. Referring to FIG. 18, in one embodiment of the invention, the blade tip 22 of blade 402 is same as the blade tip 22 of FIG. 1 and FIG. 6. In another embodiment of the invention, the blade tip 22 of blade 402 is the modified configuration 102 of the blade tip as in FIG. 7. Referring back to FIG. 17, the trailing edge 403 of tapered blade 402 is same as the trailing edge of blade 18 of FIG. 9. The leading edge 404 of the tapered blade 402, on the other hand, is tapered from its base attached to the hub 16 to the tip 22 such that there is a reduced chord length 406 at the tip of blade 402 compared to the chord length at the base. The blade tip 22 and the shroud 12 are maintained such that the clearance at the trailing edge 403 of blade 402 and the clearance at the leading edge 404 of blade 402 are equal in magnitude. Tapering the blade, as mentioned above, helps in reducing the leakage loss, thus aiding uniform lift generation throughout the blade span and thereby helps in reducing the power required for fan operation.

[0051] FIG. 19 is a diagrammatical representation' of the functional relationship between simulation studies in airfoil geometry and flow performance of the fan in accordance with another embodiment of the present invention. Specifically, FIG. 19 is a diagrammatical representation of the individual and combined effect of flow-path modification unit 32, clearance modification unit 42, fan-shroud motion unit 52 and twisted blade configuration (as in FIG. 7) for controlling fan airflow 28 (FIG. 1) in accordance with one embodiment of the present invention. Referring to FIG. 19, graph 500 diagrammatically represents flow improvement profiles for various simulation studies. The vertical bars 512, 514, 516 and 518 are drawn on a horizontal dimension of various simulation studies 502 and a vertical dimension of improved airflow performance 504.

[0052] Referring to FIG. 19, of the vertical bars, 512 represents visualization of airflow performance owing to baseline configuration. The vertical bar 514 represents visualization of airflow performance owing to a combination of Profile B profiling, axial positioning, clearance modification, twist and shroud modification. The vertical bar 516 represents visualization of airflow performance owing to a combination of Profile B profiling, axial positioning, clearance modification and shroud modification. The vertical bar 518 represents visualization of airflow performance owing to a combination of Profile B profiling, axial positioning and shroud modification. In one embodiment of the invention, the vertical bar 514 signifies 55% improvement in flow performance. In another embodiment of the invention, the vertical bar 516 signifies 28% improvement in flow performance. In yet another embodiment of the invention, the vertical bar 518 signifies 23.5% improvement in flow performance. The vertical bar 518 corresponds to the optimum configuration selected for operation as is explained in more details below with help of FIG. 20.

[0053] FIG. 20 is a diagrammatical representation of functional relationship between speed of fan and power of fan for various airfoil designs in accordance with an embodiment of the present invention. Specifically, FIG. 20 is a diagrammatical representation of the individual and combined effect of flow-path modification unit 32, clearance modification unit 42, fan-shroud motion unit 52 and twisted blade configuration (as in FIG. 7) for controlling fan airflow 28 (FIG. 1) in accordance with one embodiment of the present invention. Referring to FIG. 20, graph 600 diagrammatically represents speed of fan and power of fan for various simulation studies. The positional points 612, 614, 616 and 618 are drawn on a horizontal dimension of power of fan 602 and a vertical dimension of speed of fan 604.

[0054] Referring to FIG. 20, point 612 represents speed and power settings corresponding to baseline configuration. Vertical line 606 corresponds to standard power set-up required for baseline configuration and Horizontal line 608 corresponds to standard speed set-up required for baseline configuration. Of the other points, 614 represents speed and power settings corresponding to a combination of Profile B profiling, axial positioning, clearance modification, twist and shroud modification. The point 616 represents speed and power settings corresponding to a combination of Profile B profiling, axial positioning, clearance modification and shroud modification. The point 618 represents speed and power settings corresponding to a combination of Profile B profiling, axial positioning and shroud modification.

[0055] Referring to FIG. 20 once again, it may be observed that the points 612 and 618 overlap each other signifying that same speed and power configuration as in the baseline configuration of the fan are required for the design configuration corresponding to point 618. Further, as may be understood from the corresponding mappings in FIG. 19, in one embodiment of the invention, the point 614 corresponds to 55% improvement in flow performance. In another embodiment of the invention, the point 616 corresponds to 28% improvement in flow performance. In yet another embodiment of the invention, the point 618 corresponds to 23.5% improvement in flow performance. In one further embodiment of the invention, the point 618 represents the optimum configuration selected for operation as this signifies minimum change required over the baseline configuration in terms of speed and power of fan and maximum gain (23.5%) in flow performance.

[0056] Referring to FIG. 5 again, the control logic 200 further includes step 222 for determination of local pressure (PLOC) 222. Further, in step 224, comparison is made between Pcutofrand PLOC to determine whether PLOC is less than Pcutoff. If PLOC is more than Pcutoff, operation is stopped as in step 228. If PLOC is less than Pcutoff, speed of the fan is further increased as in step 226. The control logic is completed and ended in step 228.

[0057] FIG. 21 is a flow chart of a method 700 in accordance with an embodiment of the present invention. The method 700 includes disposing axial flow fan assembly comprising a shroud and a fan as in step 702 and configuring shroud and fan to move in relation to one another along an axis normal to the plane of rotation of the fan as in step 704. The method also includes determining an ambient parameter related to airflow as in step 706. The method further includes optimally configuring a design parameter related to the airflow as in step 708. The method subsequently includes dynamically controlling a design parameter in response to ambient parameter as in step 712.

[0058] In summary, in one embodiment of the invention, the airflow through the fan assembly 10 may be increased by dynamically controlling clearance between blades of fan and shroud and/ or by moving shroud and fan relative to one-another along an axis normal to the plane of rotation of the fan and/ or by dynamically modifying effective flow-path of the airflow and/ or by dynamically reducing effective blade power. There is an associated trade-off/ optimization to be made between fan speed and the design strategies disclosed above to reach the desired condition.

[0059] Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and feature, can be mixed and matched by one of ordinary skill in this art to construct additional assemblies and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the assemblies and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0060] While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

CLAIMS:

1. A system comprising:

an axial flow fan assembly comprising:

a shroud;

a fan, wherein said shroud and said fan are configured to move in relation to one another along a direction normal to a plane of rotation of said fan;

at least one sensor configured to sense an ambient parameter related to airflow through said fan; and

a device configured to receive a sensing signal from said at least one sensor and to dynamically control a design parameter related to said airflow in response to said signal.

2. The system of claim 1, wherein said ambient parameter comprises at least one of temperature and pressure.

3. The system of claim 1, wherein said design parameter comprises at least one parameter related to reduction of an clearance between a plurality of blades of said fan and said shroud.

4. The system of claim 3, wherein said at least one parameter related to reduction of an clearance comprises a profile of a tip of at least one of said plurality of blades.

5. The system of claim 3, wherein said at least one parameter related to reduction of an clearance comprises a geometry of said shroud.

6. The system of claim 3, wherein said at least one parameter related to reduction of an clearance comprises axial positions of said fan and said shroud in relation to one another.

7. The system of claim 6, wherein said device comprises at least one motion means to control said axial positions of said fan and said shroud in relation to one another.

8. The system of claim 1, wherein said design parameter comprises at least one parameter related to modification of an effective flow-path of said airflow.

9. The system of claim 8, wherein said at least one parameter related to modification of an effective flow-path of said airflow comprises at least one of: a profile of at least one of said plurality of blades and an extent of twist of at least one of said plurality of blades.

10. The system of claim 9, wherein said profile comprises a maximum thickness of said blade occurring at a first location corresponding to about 33% of a chord length of said blade, said first location measured from a center of a leading edge circle of said blade; and a maximum camber of said blade occurring at a second location corresponding to about 49% of the chord length of said blade, said second location measured from said center of said leading edge circle of said blade.

11. The system of claim 1, wherein said design parameter comprises at least one parameter related to effective blade power reduction.

12. The system of claim 11, wherein said at least one parameter related to effective blade power reduction comprises a taper of at least one of said plurality of blades along its height.

13. The system of claim 1, wherein said axial flow fan assembly is configured to cool a radiator in a locomotive fan assembly.

14. The system of claim 1, wherein said design parameter comprises a speed of said fan.

15. A method comprising:

disposing an axial flow fan assembly comprising a shroud and a fan;

configuring said shroud and said fan to move in relation to one another;

determining at least one ambient parameter related to airflow through said fan assembly;

optimally configuring a design parameter related to said airflow; and

dynamically controlling said design parameter in response to said ambient parameter.

16. The method of claim 15, wherein said ambient parameter comprises at least one of: temperature and pressure.

17. The method of claim 15, wherein said design parameter comprises clearance between a plurality of blades of said fan and said shroud and wherein said configuring comprises reducing said clearance.

18. The method of claim 17, wherein said reducing said clearance comprises profiling of a tip of at least one of said plurality of blades.

19. The method of claim 17, wherein said reducing said clearance comprises configuring a geometry of said shroud.

20. The method of claim 17, wherein said reducing said clearance comprises controlling axial positions of said fan and said shroud in relation to one another.

21. The method of claim 15, wherein said design parameter comprises effective flow-path of said airflow and wherein said configuring comprises modifying said effective flow-path.

22. The method of claim 21, wherein said modifying comprises modifying at least one of: a profile of at least one of said plurality of blades and an extent of twist of at least one of said plurality of blades.

23. The method of claim 22, wherein said profile comprises a maximum thickness of said blade occurring at a first location corresponding to about 33% of a chord length of said blade, said first location measured from a center of a leading edge circle of said blade; and a maximum camber of said blade occurring at a second location corresponding to about 49% of the chord length of said blade, said second location measured from said center of said leading edge circle of said blade.

24. The method of claim 15, wherein said design parameter comprises at least one structural parameter related to effective blade power and wherein said configuring comprises configuring said structural parameter.

25. The method of claim 24, wherein said configuring said structural parameter comprises tapering of at least one of said plurality of blades along its length.

26. The method of claim 15, wherein said design parameter comprises a speed of said fan.

27. The method system of claim 15, further comprising disposing a radiator in a locomotive fan assembly in proximity of said airflow; and cooling said radiator.

28. A system comprising:

an axial flow fan assembly comprising a shroud and a fan, wherein said shroud and said fan are configured to move in relation to one another; and

a device configured to control at least one design parameter related to airflow through said fan assembly.

29. The system of claim 28, wherein said design parameter comprises at least one of: at least one parameter related to reduction of an clearance between a plurality of blades of said fan and said shroud; at least one parameter related to modification of an effective flow-path of said airflow; and at least one structural parameter related to effective blade power reduction.

30. The system of claim 29, wherein said at least one structural parameter comprises at least one of: a profile of at least one of said plurality of blades; and a twist-angle of at least one of said plurality of blades.