Propeller

Abstract

To provide a propeller used in, for example, an aircraft, a vessel, a turbine, an unmanned aircraft, and an air circulation device.SOLUTION: A propeller includes means for creating fluid flow in a non-axial direction and redirecting it in an axial direction.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to propellers that may be used, for example, in aircraft, ships, turbines, unmanned aerial vehicles, and air circulation devices. Summary of the Invention

[0002] An embodiment of the present invention provides a propeller having a plurality of blades, means for generating non-axial lift by generating a non-axial fluid flow, and means for redirecting the non-axial fluid flow to generate axial fluid movement or thrust. The propeller may have a hub or a rim configuration, i.e., "hubless." The plurality of blades either extend outward from the hub or inward from the rim. Each blade may form an open or closed loop-type structure with an intake section, an exhaust section, and a tip that extends radially outward from the hub or inward from the rim configuration, i.e., "hubless." The means for generating non-axial lift and non-axial fluid flow to generate axial thrust may be a configuration of blades, each having a cross-sectional profile such that, at at least a portion of the tip, the distance from the axis of rotation to the leading edge of the blade exceeds the distance from the axis of rotation to the trailing edge of the blade.

[0003] A blade may have an inlet section, a discharge section, and a tip section that connects the inlet section and the discharge section but is not necessarily a separate component. A propeller may have an inlet root and a discharge root, for example, on either the rim or the hub. The tip section may include a 90-degree roll angle, with zero roll at the inlet root. The tip apex and pitch angles may be positive throughout. In an exemplary embodiment, the tip section generates more non-axial lift than either the inlet or the discharge section.

[0004] In an exemplary embodiment, the transition from suction to tip occurs when a given parameter section of the vane generates a greater amount of non-axial lift than it generates axial lift. [Brief explanation of the drawings]

[0005] For a more detailed description of exemplary embodiments of the disclosed propeller, reference is made to the following detailed description taken in conjunction with the following figures, all of which are exemplary embodiments of the disclosed propeller. [Figure 1A] 1 illustrates an exemplary propeller. [Figure 1B] 1 illustrates an exemplary propeller. [Figure 1C] 1 illustrates an exemplary propeller. [Figure 1D] 1 illustrates an exemplary propeller. [Figure 1E] 1 illustrates an exemplary propeller. [Figure 2] FIG. 10 illustrates a parameter section defining a propeller blade. [Figure 3] 10 is a diagram showing the shape of a blade parameter section. [Figure 4A] FIG. 1 shows the measured rake of the propeller blade's intake (intake), tip, and discharge (exhaust) parameter sections. [Figure 4B] FIG. 1 shows the rake measurements of the inlet, tip and outlet parameter sections of a propeller blade. [Figure 4C] FIG. 1 shows the rake measurements of the inlet, tip and outlet parameter sections of a propeller blade. [Figure 4D] FIG. 1 shows the rake measurements of the inlet, tip and outlet parameter sections of a propeller blade. [Figure 4E] FIG. 1 shows the rake measurements of the inlet, tip and outlet parameter sections of a propeller blade. [Figure 4F] FIG. 1 shows the rake measurements of the inlet, tip and outlet parameter sections of a propeller blade. [Figure 5A] FIG. 1 shows the measured skew and apex angles of the propeller blade inlet, tip, and outlet parameter sections. [Figure 5B] FIG. 1 shows the measured skew and apex angles of the propeller blade inlet, tip, and outlet parameter sections. [Figure 5C] FIG. 1 shows the measured skew and apex angles of the propeller blade inlet, tip, and outlet parameter sections. [Figure 5D] FIG. 1 shows the measured skew and apex angles of the propeller blade inlet, tip, and outlet parameter sections. [Figure 5E] FIG. 1 shows the measured skew and apex angles of the propeller blade inlet, tip, and outlet parameter sections. [Figure 5F] FIG. 1 shows the measured skew and apex angles of the propeller blade inlet, tip, and outlet parameter sections. [Figure 6] 1 is a diagram showing an example of a fluid flow around a propeller blade. [Figure 7A] FIG. 10 shows examples of alpha and radius values ​​in the selected parameters section. [Figure 7B] FIG. 10 shows examples of alpha and radius values ​​in the selected parameters section. [Figure 7C] FIG. 10 shows examples of alpha and radius values ​​in the selected parameters section. [Figure 7D] FIG. 10 shows examples of alpha and radius values ​​in the selected parameters section. [Figure 8A] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8B] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8C] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8D] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8E] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8F] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8G]FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 8H] FIG. 10 illustrates exemplary values ​​or relative values ​​of parameters defining a parameter section or vane. [Figure 9A] FIG. 10 shows the pitch angle of selected parameter sections of a blade. [Figure 9B] FIG. 10 shows the pitch angle of selected parameter sections of a blade. [Figure 9C] FIG. 10 shows the pitch angle of selected parameter sections of a blade. [Figure 9D] FIG. 10 shows the pitch angle of selected parameter sections of a blade. [Figure 9E] FIG. 10 shows the pitch angle of selected parameter sections of a blade. [Figure 9F] FIG. 10 shows the pitch angle of selected parameter sections of a blade. [Figure 10A] FIG. [Figure 10B] FIG. [Figure 11] A diagram showing an unmanned aerial vehicle. [Figure 12A] FIG. 10 shows the roll angle in the selected parameters section. [Figure 12B] FIG. 10 shows the roll angle in the selected parameters section. [Figure 12C] FIG. 10 shows the roll angle in the selected parameters section. [Figure 13A] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 13B] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 13C] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 13D] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 13E] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 13F] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 13G] FIG. 1 shows a propeller without a hub, but with a ring from which the propeller blades extend. [Figure 14A] Diagram showing a two-bladed propeller. [Figure 14B] A cross section of a two-bladed propeller. [Figure 15A] Diagram showing a three-bladed propeller. [Figure 15B] A cross section of a three-bladed propeller. [Figure 16A] Diagram showing a five-bladed propeller. [Figure 16B] A cross section of a five-bladed propeller. [Figure 17A] Diagram showing a seven-bladed propeller. [Figure 17B] A cross section of a seven-bladed propeller. [Figures 18A-18G] FIG. 1 illustrates an exemplary embodiment of a high rake propeller. [Figures 19A-19G] FIG. 1 illustrates another exemplary embodiment of a high rake propeller for intake and exhaust. [Figures 20A-20I] Diagram showing an inboard propeller. [Figures 21A-21F] FIG. 1 shows a propeller with through-hub exhaust. DETAILED DESCRIPTION OF THE INVENTION

[0006] 1A-1E illustrate a propeller 100 according to an exemplary embodiment. FIG. 1A illustrates a perspective view of the propeller 100. FIG. 1B illustrates a side view of the propeller 100, and FIG. 1C illustrates an opposite side view of the propeller 100. FIGS. 1D and 1E illustrate a top (front) view and a bottom (rear) view of the propeller 100, respectively. The propeller 100 includes a plurality of blades 102, 104, and 106, each having a tip 122, an intake 124, and an exhaust 126. In this exemplary embodiment, the blades 102, 104, and 106 extend from a hub 128. Each of the blades 102, 104, and 106 has a centerline 108, 110, and 112, respectively. The blades 102, 104, and 106 rotate about a hub axis 103. For simplicity, the term "hub" is sometimes used to include any axis of rotation, even if there is no physical hub.

[0007] The vane has a means for generating non-axial lift and non-axial fluid flow and a means for redirecting the non-axial fluid flow into an axial fluid flow. In an exemplary embodiment, the means for generating non-axial lift and non-axial fluid flow is a vane tip arrangement, as described further below. In an exemplary embodiment, the means for redirecting the non-axial fluid flow into an axial fluid flow is a tip and inlet arrangement, and may further include an exhaust, as described in more detail below.

[0008] As used herein, the term "propeller" may include a rotating blade device that can be used to move a fluid to propel a device or that is employed on a stationary device, such as an air circulation fan, including, for example, a cooling fan, to move a fluid, such as air, through or around the stationary device.

[0009] Propeller 100 has three blades 102, 104, 106 spaced at equal increments around hub 128. Propellers of the disclosed embodiments may have coplanar rotating blades, for example, two, three, four, five, six, seven, or eight blades. The number of blades will largely depend on the application of the propeller. For example, adding blades increases the blade area of ​​the employed propeller, thereby reducing blade loading, which may be beneficial for increasing the weight of the boat or aircraft.

[0010] The blades 102, 104, 106 may be configured to rotate about an axis corresponding to the hub axle 103, or in hubless devices, the blades may extend inward from a rotating support. Rotation of the support may be induced by an electromagnetic field. Hub 128 may also be hollow and may have openings in its surface, like the hub of a centrifugal fan.

[0011] FIG. 2 illustrates a vane 200 having parameter sections 1-29. Parameter section 1 is near the suction root 204, and parameter section 29 is near the discharge root 206. Each parameter section represents a set of physical properties or measurements whose values ​​determine the characteristics of the vane area. The parameter sections, as a group, determine the shape of the vane 200 and its behavior. While the parameter sections are evenly spaced in the exemplary embodiment, they may be selected to be unevenly spaced. FIG. 2 merely illustrates how the vane's parameter sections are laid out to define the vane's shape. The parameter sections represent the shape and orientation of the vane 200 at specific locations along the vane. Smooth transitions are made between the parameter sections to create the vane. As used herein, "orientation" may include position. In the exemplary embodiment of FIG. 2, vane sections 1-29 are planar sections arranged along an irregular helical median line 202. As used herein, "irregular helical" means a variation from the mathematical helix definition or as a helix in 3D space, where the angle between the tangent at any point on the helix and the propeller axis is not constant.

[0012] Although 29 blade sections are shown in Figure 2, more or fewer sections may be used to define the blades. Additionally, sections may be located within or partially located within a hub, which is not shown at all or not entirely. Blades may be defined by planar or cylindrical parameter sections.

[0013] Parameter sections 1-29 are defined by directional variables, such as roll angle and vertical angle (α), and may include position variables and shape variables such as chord length, thickness, and camber. Additional exemplary directional or position variables include rake, skew angle, and radius. Some or more of the variables may vary across a blade or blade section, while some may be constant throughout. Directional variables may be measured with reference to an X-Y-Z coordinate system. The X-Y-Z coordinate system has its origin at the shaft centerline and a generatrix perpendicular to the shaft or hub axis 103. The X-axis is positive downstream along the hub axis 103. The Y-axis extends upward along the generatrix, and the Z-axis is positive toward port for a right-handed propeller. A left-handed propeller is created by swapping the Z-axis to create a left-handed coordinate system.

[0014] The parameter sections may be positioned by the midpoint of the chord (leading to trailing edge), such as by using radius, rake, and skew. The parameter sections may be oriented using angles φ (phi), ψ (psi), and α (alpha), as further described below.

[0015] FIG. 3 illustrates a parameter section shape of a blade with reference to the outer cross-sectional diameter of the blade, which may be the parameter section. An example parameter section 300 is shown. The parameter section 300 is in the form of an asymmetrical airfoil. The airfoil is bounded by a curved blade surface line 302 and a generally flat blade surface line 304, with a rounded leading end 306 at the leading edge 310 of the parameter section and a pointed or less rounded trailing end 308 at the trailing edge 312 of the parameter section 300. Alternatively, the parameter section may be in the form of a symmetrical airfoil. Other parameter section shapes include, for example, a shape in which the blade surface lines 302, 304 are parallel. Alternatively, the blade surface lines 302, 304 may be straight and angled relative to one another. Both the leading and trailing edges may be radiused, both may be flat (orthogonal to one or both of the vane surface lines 302, 304), or either the leading edge or the trailing edge may be radiused and the other flat. For vanes formed from sheet material, for example, the vane surface lines 302, 304 may be generally parallel. In the illustrated example of a sheet-formed vane, the leading edge of the vane is radiused and the trailing edge is flat or less radiused, although both the suction and trailing edges may be radiused.

[0016] Exemplary shape variables in the parameters section are defined as follows:

[0017] Radius: The term "radius" is used to define both the shape of the parameter section and its orientation relative to the X-Y-Z coordinate system. With respect to the shape of the parameter section, the radius can represent, for example, the curvature of the leading edge 306 of the parameter section 300, and thus will be referred to as the "nose radius." Other attributes of the parameter section 300 can be used to calculate the radius. As an example, the parameter section leading edge radius can be calculated based on the maximum thickness 316 and the length of the chord 314.

[0018] Chord: The chord is the line 314 from the leading edge to the trailing edge of the parameter section.

[0019] Thickness: Various thickness measurements can define a parameter section, such as maximum thickness 316. Another illustrative example includes trailing edge thickness, which can be calculated as a percentage of maximum thickness 316. For example, trailing edge thickness can be 8% of maximum thickness 316 of parameter section 300.

[0020] Camber: Camber 318 defines the curvature of the parameter section.

[0021] Exemplary directional variables include:

[0022] Rake: Rake is the axial position of the parameter section mid-chord.

[0023] "Axial location," in this case, refers to the direction along the X-axis, which coincides with the propeller axis of rotation. Exemplary rake measurements are shown in Figures 4A-4F for various parameter sections. Each of Figures 4A-4F shows coordinates X, Y, and Z, where the X-axis coincides with the propeller axis of rotation, the Y-axis and the Z-axis are orthogonal to the X-axis, and the three axes are orthogonal to each other. Parameters are measured from the origin of the coordinate system. In an exemplary embodiment, the zero point of the coordinate system is along the propeller axis of rotation and is closer to the intake root than the exhaust root. Illustratively, values ​​along the X-axis toward the intake root are negative, and values ​​toward the exhaust root are positive. In general, the coordinate system is positioned as desired, and all parameters or geometries are measured from the origin of the selected coordinate system.

[0024] 4A and 4B show rake for parameter sections 412, 414 on the inlet section 402 of the blade 400. Parameter section 412 in FIG. 4A is toward the tip 404 of the blade 400. Parameter section 414 is toward the suction root 406. Rake is measured along the propeller axis of rotation or along a line parallel to the axis of rotation. In the illustrated example of FIGS. 4A and 4B, rake is the distance from point A, where X equals 0, to the X coordinate value of point B, which is the midpoint 410 of the chord of parameter sections 412, 414. The X coordinate value of point B is shown as B in FIGS. 4A-4F. x It is expressed as:

[0025] 4C and 4D illustrate the rake relative to parameter sections 418, 420 on the tip 404 of the blade 400. Parameter section 418 in FIG. 4C is at a first position on the tip 404 of the blade 400, where the roll value (discussed further below) is greater than zero and less than 90 degrees. Parameter section 420 in FIG. 4D is at a second position on the tip 404, where the roll value is 90 degrees or greater. In the illustrated example of FIGS. 4C and 4D, the rake is measured from point A with X equal to zero to point B with X coordinate value B. x 4E and 4F show the rake for parameter sections 422, 424 on the discharge section 426 of the blade 400. Parameter section 422 in FIG. 4E is at the tip 404 side of the blade 400. Parameter section 424 is at the discharge root 428 side. In the illustrated example of FIGS. 4E and 4F, the rake is the distance from point A with X equal to zero to the X coordinate value of point B, with point B being at the midpoint 410 of the chord of parameter sections 422, 424.

[0026] Pitch angle: The pitch angle is the angle between the chord line of the parameter section and a plane perpendicular to the X-axis. The pitch angle can be calculated based on the pitch spacing and the blade radius. Examples of pitch angles of parameter sections are provided in Figures 4A and 4C. Figures 4A and 4C show the pitch angles of parameter sections 412 and 418, respectively.

[0027] Radius: The orientation radius is the distance from the hub center 208 to the midpoint 320 of the parameter section chord 314. The chord 314 is also referred to as the nose-to-tail line. The radii described in this paragraph are referred to as parameter section orientation radii to distinguish them from parameter section shape radii, such as nose radius, which are not measured relative to an X-Y-Z coordinate system. The midpoint 320 of the chord 314 is the point on the parameter section chord line through which the centerline 202 would pass. This is shown in FIG. 2 by the line R extending from the hub center 208 to the midpoint of the chord of parameter section 5. Note that the chord of parameter section 5 and its midpoint are not specifically shown in FIG. 2.

[0028] 5A-5F show the vane 400 as viewed along the vane rotation axis X. FIGS. 5A-5F identify the radii and skew angles of representative parameter sections. FIG. 5A shows the radius of parameter section 412 at the inlet section 402 of the vane 400. FIG. 5B shows the radius of a parameter section at the inlet section 402 of the vane 400 that is further from the suction root 406 than parameter section 412, i.e., parameter section 414. FIGS. 5C and 5D show the radii of parameter sections 418 and 420, respectively, at the tip section 404. FIGS. 5E and 5F show the radii of exhaust parameter sections 422 and 424, respectively, at the exhaust section 426. The locations of parameter sections 412, 414, 418, 420, 422, and 424 when at the inlet section 402, tip section 404, or exhaust section 426 are provided solely for ease of discussion. Alternatively, the actual parameter values ​​and resulting fluid flow may define the location of the section.

[0029] 5A-5F further illustrate the skew angle in parameter sections 412, 414, 418, 420, 422, 424. The skew angle is the angle projected from a line passing through midpoint 410 of chord 314 to the Y-axis as viewed along the generatrix, in this exemplary embodiment, hub axis 103 (X-axis).

[0030] In addition to showing the skew angle and radius, Figures 7A-7D also show the apex angle α of the parameter section marked in each of Figures 7A-7D. The apex angle is sometimes also referred to as the "lift angle." α is the angle at which the parameter section is rotated relative to a line perpendicular to the skew line, identified in Figures 6A-6D and described below. This skew line refers to a line that forms a skew angle with the zero skew line. Depending on the value of α, the leading edge of the parameter section will either be "lifted" or "hanging" from a line perpendicular to the skew line that forms a skew angle with the zero skew line, which coincides with the Y-axis of the coordinate system identified in Figures 7A-7D.

[0031] Note that in Figures 5A-5F, α is zero and therefore not specified. When α is zero, the chord line of the parameter section is perpendicular to the zero skew line. This condition can be seen by comparing Figures 5A-5F with Figures 7A-7D.

[0032] Roll: Roll is the angle that a parameter section rotates about its chord line. As described herein, a zero roll value is in a plane parallel to the hub axis. In an exemplary embodiment, the roll at the suction root 132 is zero, the roll at the discharge root 134 is 180 degrees, and the roll at a position within the tip 122 is 90 degrees.

[0033] Various exemplary embodiments are described in terms of combinations of features. The disclosed propellers may include various combinations of features, equivalents of elements, and other embodiments in which not all features are included.

[0034] In an exemplary embodiment of the propeller, the propeller comprises a plurality of loop-shaped blades, as generally shown in Figures 1A-1E. The propeller of Figure 1A is referenced only as a general reference to identify the propeller region. The actual configuration of the propeller blades will vary within the specified ranges depending on the parameters.

[0035] Each blade 102, 104, 106 of propeller 100 includes a tip section 122, an inlet section 124, and an outlet section 126. In an exemplary embodiment, the inlet section occupies 0-45% of the blade, the tip section occupies 30-75% of the blade, and the outlet section occupies 50-90% of the blade.

[0036] Propeller 100 may have various numbers of blades. While the blades may vary within the scope of the embodiments, each preferably has the same characteristics and parameters. While two to twelve blades are illustrated, a propeller may have many more blades. In certain embodiments, a propeller may have three, four, five, seven, or eleven blades. In propeller embodiments with looped blades, the blades have an inlet root 132 at the hub 128 and a discharge root 134 at the hub 128. The inlet section 124, tip section 122, and discharge section 126 may together form a closed loop, or the loop may be open at the inlet "root" or discharge "root."

[0037] Roll: The roll angle (ψ) is, for example, the angle of orientation about the chord 314. Returning to FIGS. 1A-1F , for a propeller including the hub 128, the inlet section 124 extends generally outward from the hub 128. The inlet section 124 may have zero roll at the inlet root 132. The inlet section 124 may be configured to generate only axial lift or to generate axial lift greater than non-axial lift. The roll value for the entire parameter section of the inlet section 124 may be zero. An exemplary range of roll values ​​for the parameter section of the inlet section 124 is zero at the inlet root 132 and increases from approximately 1 degree to 35 degrees from the inlet section 124 to the tip section 122. Other ranges of roll values ​​for the inlet section 124 from the inlet root 132 to the tip section 122 include an increase from zero to approximately 5 degrees to 25 degrees and an increase from zero to approximately 10 degrees to 20 degrees.

[0038] The tip 122 may alternatively be defined by a tip intake end beginning at a roll value of zero at a first deviation and extending to a tip discharge end beginning at a roll value of 90 degrees or slightly greater than 90 degrees.

[0039] The tip section 122 is configured to generate only non-axial lift, to generate non-axial lift in excess of axial lift, or to generate non-axial lift in excess of axial lift relative to the inlet section 124. The roll values ​​in the parameter section for the tip section 122 will transition from less than 90 degrees to greater than 90 degrees. Exemplary roll value ranges for the tip section 122 include between 1 degree and 46 degrees at the transition from the inlet section 124 and between 91 degrees and 150 degrees where the tip transitions to the exhaust section 126. Other exemplary roll value ranges for the tip section 122 include between 5 degrees and 25 degrees at the transition from the inlet section 124 and between 110 degrees and 135 degrees of roll.

[0040] In an exemplary embodiment, the transition from intake section 124 to tip section 122 occurs when the amount of non-axial lift generated by a given parameter section exceeds the axial lift. In a specific embodiment of the invention, this transition occurs when the roll is 45 degrees or when the roll is in the range of 40 degrees to 50 degrees.

[0041] The discharge section 126 is configured to generate less non-axial lift than the tip section 122. In an exemplary embodiment of the invention, the blades are configured such that the average non-axial lift is greatest at the tip section 122 compared to either the inlet section 124 or the exhaust section 126. In an exemplary embodiment, the blades are configured such that the average non-axial lift is greatest at the exhaust section 126 than at the inlet section 124, as the case may be. Exemplary ranges of roll values ​​for the discharge section 126 include between 91 degrees and 150 degrees at the transition from the tip section 122 to the discharge section 126, and 180 degrees at the discharge root 134. Other exemplary ranges include between 91 degrees and 135 degrees at the transition from the tip section 122 and 180 degrees roll at the discharge root 134.

[0042] 8A-8H illustrate exemplary values ​​or relative values ​​of various parameters that define a parameter section or blade. FIG. 8A illustrates exemplary roll values ​​from the suction root to the discharge root of the blade. In an exemplary embodiment, from the suction root 132 to the discharge root 134, the roll of the parameter section transitions from approximately 0 degrees to 5 degrees over the first 25 percent of the blade, from approximately 5 degrees to approximately 162 degrees over the next 50 percent of the blade, and from approximately 165 degrees to approximately 180 degrees over the last 25 percent of the blade.

[0043] In an exemplary embodiment, between 10 percent and 90 percent of the blade generates non-axial lift, with further exemplary ranges including 10 percent to 75 percent and 25 percent to 50 percent.

[0044] 6 shows an illustrative example of a propeller 600 showing fluid flow around blades 602, 604. Inlets 606, 608 show axial fluid flow at the inlets 606, 608 of blades 602, 604, respectively. The fluid flow remains axial as the propeller moves forward or fluid moves through blades 602, 604. The fluid flow remains axial as the fluid leaves outlets 610, 612 of blades 602, 604.

[0045] Within the tips of the blades 602, 604, axial thrust is generated from non-axial lift. The non-axial lift forces cause fluid flow into the propeller blade, such as inside the loops. The fluid impinges non-axially against the leading edges of the tips 610, 612. As the fluid is drawn in by the tips 610, 612, it is redirected axially within the loops of the blades 602, 604. The non-axial lift forces can cause drag from the tips. As the fluid passes the trailing edges of the blades 602, 604, at the tips 610, 612, the fluid is axial or more axial than when it entered the loops of the blades 602, 604.

[0046] In the exemplary embodiment, propeller 600 is configured to create a mixture of freestream and jet fluid flow behind the propeller, where the mixing area is larger than the diameter of the propeller, which in this case is a measurement of the maximum span of the propeller across the hub axle.

[0047] 1A-1F, tip section 122, inlet section 124, and exhaust section 126 do not necessarily extend equal distances, such as along centerlines 108, 110, and 112. In an exemplary embodiment, inlet section 124 occupies a shorter distance than exhaust section 126. Thus, the distance along centerlines 108, 110, and 112 to the point where the vane is configured to redirect axial lift into non-axial lift is greater from exhaust root 134 than from suction root 132. In an exemplary embodiment, inlet section 124 extends a distance in the range of 10 percent to 50 percent of the centerline length, exhaust section 126 extends a distance in the range of 10 percent to 60 percent of the centerline length, and tip section 122 extends a distance in the range of 5 percent to 60 percent of the centerline length.

[0048] 8B illustrates exemplary relative pitch angle values ​​from the suction root to the discharge root of the blade. In an exemplary embodiment, from the suction root 132 to the discharge root 134, the pitch angle of the parameter section transitions from approximately 70 degrees to approximately 35 degrees, over the next 50 percent of the blade the pitch angle transitions from approximately 35 degrees to approximately 25 degrees, and over the last 25 percent of the blade the pitch angle transitions from approximately 25 degrees to approximately 75 degrees. In an exemplary embodiment of the invention, the pitch angle is non-zero throughout at the tip 122. In an exemplary embodiment of the invention, the tip 122 is defined and configured to have a non-zero pitch and redirect non-axial lift to generate axial thrust.

[0049] FIG. 8C illustrates the apex angle α of the blade from the suction root to the discharge root according to an exemplary embodiment. The apex angle orients the parameter sections non-orthogonal to the skew. In the exemplary embodiment, the apex angle is zero for all parameter sections. In another embodiment, the apex angle for the suction and tip sections is positive for all parameter sections, and the apex angle for the discharge section is negative for all parameter sections. In yet another embodiment, the tip section 122 may have at least one parameter section with a non-zero apex angle. In other embodiments, the average apex angle for the tip and suction sections is greater than the average apex angle for the discharge section.

[0050] In the exemplary embodiment, the average apex angle for the parameter section of the discharge section 126 is greater than the average apex angle for the parameter section of the intake section 124 .

[0051] Exemplary ranges for the apex angle of the tip 122 include 0-1 degree, 1-10 degrees, 4-6 degrees, 0-5 degrees, 1-4 degrees, and 2-3 degrees. The apex angle may also be zero throughout the blade. The apex angle at the apex may cause fluid to be drawn into the blade "loop," thereby generating drag. The apex angle at the apex may also cause fluid flow off-axis, which is redirected into the axial fluid flow within the loop. A larger apex angle in the apex region increases the amount of non-axial lift, which in turn increases the amount of non-axial fluid flow into the propeller. The apex angle of the parameter section of the tip 122 may generate non-axial lift and drag nearby. In exemplary embodiments, the apex angle is between -45 and 45 degrees, between -25 and 25 degrees, or between -15 and 15 degrees throughout the blade.

[0052] 8D illustrates exemplary relative radius values ​​from the suction root to the discharge root of the blade. In an exemplary embodiment, the radius of the parameter section increases over the first 60 to 80 percent of the blade starting at the suction root 132, and then decreases through the parameter section through the discharge root 134. As used in this and other paragraphs, the transition of parameters across the parameter section corresponds to the transition through the blade.

[0053] 8E illustrates an exemplary rake value from the suction root to the discharge root of the blade. The rake in the exemplary embodiment may be gradually negative from the suction root 132 of the blade for the first 30 to 40 percent of the blade. The rake may then increase over the next 10 to 15 percent of the blade until it reaches a positive value. The rake may continue to increase over the next 20 to 40 percent of the blade, and then level off or decrease for the remainder of the blade. The rake may also be linear from the suction root at zero to the positive discharge root value.

[0054] 8F illustrates an exemplary relative skew value from the suction root to the discharge root of the blade. In an exemplary embodiment, the skew value continues to increase from the suction root 132 to the discharge root 134. In another exemplary embodiment, the skew value may continue to decrease such that the discharge is forward of the suction and tip in the plane of rotation. The chord 314 of the parameter section may be perpendicular to the skew line throughout the blade or at a portion of the blade. Here, the skew line that the chord 314 is perpendicular to is the skew line that cooperates with the zero skew line to form the skew angle.

[0055] 8G shows exemplary relative camber values ​​from the suction root to the discharge root of the blade. In the exemplary embodiment, the camber of the parameter section transitions from a positive value at the suction root 132 to a negative value at the discharge root 134. Here, the suction side of the blade changes to the pressure side of the blade near the tip-to-discharge transition at the interface of the positive and negative camber.

[0056] 8H shows exemplary relative chord values ​​from the suction root to the discharge root of the blade. In an exemplary embodiment, the chord decreases from the suction root 132, then begins to increase toward the discharge section 126 and continues to increase to the discharge root 134. In another exemplary embodiment, the chord increases from the suction root 132, then decreases toward the discharge section 126 and continues to decrease to the discharge root 134.

[0057] In an exemplary embodiment, the tip 122 from the tip intake end to the tip discharge end exhibits one or more of the following characteristics: The mean non-axial lift is greater than the mean axial lift ·Non-axial lift is generated from the tip intake end to the tip discharge end. Alpha value is zero throughout. The pitch angle is positive throughout. · The pitch spacing is positive throughout. The pitch angle is positive throughout between 70% and 95% of the tip 122. The vane radius value is maximized within the tip extending from the parameter section with a roll value of 80 degrees to the parameter section with a roll value of 95 degrees.

[0058] The table below provides example values ​​for selected parameter sections. The parameter sections are 2, 6, 11, 19, 25, and 29 selected from a vane consisting of 30 parameter sections. Parameter section 2 is the selected parameter section closest to the suction root 132. Parameter section 29 is the selected parameter section closest to the discharge root 134. [Table 1]

[0059] 5A-5F provide schematic representations of parameter sections 2, 6, 11, 19, 25, and 29, respectively. As noted above, FIGS. 5A-5F illustrate parameter sections with an α value of zero. In an exemplary embodiment, such parameter sections may be part of a group of parameter sections that all have an α value of zero and form a propeller blade.

[0060] 5A-5F, it can be seen that the radius increases from parameter section 2 to parameter section 19, then decreases from parameter section 25 to parameter section 29. The pitch, skew, and roll increase across parameter sections 2, 6, 11, 19, 25, and 29. The pitch angle decreases from parameter section 2 to parameter section 25, then begins to increase at parameter section 29.

[0061] 9A-9F provide a schematic representation of the pitch angle for parameter sections 2, 6, 11, 19, 25 and 29, respectively. The pitch angle varies across the blade, with maximum values ​​at the suction root and discharge root.

[0062] 7A-7D show representations of parameter sections 6, 11, 19, and 25 of the 30 parameter sections that make up a blade, as shown in the table below. Such parameters include varying α values. The table below provides example values ​​for selected parameter sections. [Table 2]

[0063] The radius, pitch, skew, pitch angle, and roll are given the same values ​​as in the illustrated example where α is zero. In the embodiment shown in Figures 7A-7D, α decreases from parameter sections 6 to 19, then becomes negative at locations on the blade between parameter sections 19 and 25. This change is illustrated in Figures 7A-7D.

[0064] It should be noted that where values ​​are associated with section parameters, the values ​​may define vane sections, such as the inlet, tip and exhaust sections, each of which are defined herein.

[0065] Exemplary embodiments of the propeller may include one or more of the following features, as well as any of the features described herein. Over at least a portion of the tip 122 of the suction side 90-degree roll, the distance (N) from the hub axis 103 to the front end of the parameter section measured vertically exceeds the distance (T) from the hub axis to the rear end of the parameter section measured vertically. At 80% of the tip, the roll value is below 90 degrees and N>T. The average pitch angle of the discharge section 126 is greater than the average pitch of the intake section 124. The pitch angle changes in response to changes in roll. The pitch angle is positive throughout the entire blade. The overall length of the leading edge of the propeller blade exceeds the overall length of the trailing edge measured perpendicular to the propeller axis. - The initial rake position (suction side root) is lower than the final rake position (discharge side root), so there is a gap between the suction side root and the discharge side root when the discharge side root is located behind the suction side root. The skew increases from the suction root 132 to the discharge root 134. The suction root is ahead of the discharge root, and the skew starts at zero and ends at a positive value. The suction root is behind the discharge root, and the skew starts at zero and ends at a negative value. The entire intake section is in front of the discharge section, except for the top area. The maximum thickness of the blade cross section is between the midpoint of the chord and the leading edge of the cross section. The pressure surface continues to rotate toward the apex of the suction section, becoming the suction surface of the discharge section. The suction root 132 is aligned with the discharge root 134, with zero skew. Substantial mixing of the jet stream and free stream downstream of the discharge vanes compared to traditional propellers. The blades are configured to "effectively increase" the propeller diameter by increasing mixing between the free stream and the jet stream. The pitch angle of the discharge vanes at their base ends is greater than the pitch angle of the suction vanes at their base ends. The tip has a 90 degree roll angle closer to the discharge than to the intake. There is a gap between the base of the intake and exhaust parts. · The chord length of the parameter section varies across the blade. ·The parameter sections that make up the blade are planar and perpendicular to the centerline. ·Part or all of the parameter sections that make up the blade are not planar but cylindrical with respect to the center line. · Negative rake at discharge. · The rake at the discharge section is positive. Various blade configurations can be combined into a single propeller.

[0066] Propeller variations may have the same centerline but vary in other parameters. A series of propellers according to exemplary embodiments of the present invention are based on a common centerline and may vary blade parameters including section pitch, angle of attack, angle, rake, surface area, area ratio, spline shape, cross-sectional profile, chord length, apex angle, and roll.

[0067] FIGS. 14A and 14B, 15A and 15B, 16A and 16B, and 17A and 17B are side and cross-sectional views of two-bladed, three-bladed, four-bladed, and seven-bladed propellers, respectively. The cross-sections are taken along the axis of rotation from a position forward on the propeller. The cross-sections are taken generally at the tip 122 of the blade. As can be seen in each cross-sectional view, for each blade cross-sectional profile, at this particular region of the tip 122, the distance A from the axis of rotation to the leading edge of the blade cross-section exceeds the distance B from the axis of rotation to the trailing edge of the blade cross-section. In an exemplary embodiment of the invention, A is greater than B for the entire tip 122. In another exemplary embodiment of the invention, A is greater than B for between 50 percent and 100 percent of the tip 122. In another embodiment, the percentage of the tip 122 where A is greater than B is in the range of between 85 percent and 90 percent. In general, the greater the difference in length between A and B, the more fluid will be entrained from the off-axial direction. Similarly, the greater the proportion of the blade where A is greater than B, the more fluid will be entrained from the off-axial direction.

[0068] Exemplary embodiments have been shown or described as propellers with hubs. The blades described herein may also be used in hubless propeller devices, as shown in FIGS. 13A-13G. FIG. 13A is a perspective view of a "hubless" propeller 800. In this embodiment, there are seven blades 804, each having an inlet root 132 and a discharge root 134 extending from a rim 802, with the tip 122 pointing toward the center of the propeller. FIGS. 13B-13G show top (upper), bottom (bottom), "front" (front), "rear" (rear), "left" (left side), and "right" (right side) views, respectively. The terms "left," "right," "front," and "rear" are used solely to distinguish between views spaced 90 degrees around the propeller and are not meant to be literal, given the circular nature of the device. The blades have the same or similar characteristics as a hubbed propeller, but some provide a change in the intake flow due to the rim.

[0069] Also disclosed is a method of creating a propeller according to any of the embodiments described herein. In an exemplary embodiment, multiple independently modifiable direction and shape variables are provided to define the orientation and shape of multiple parameter sections that form a propeller blade. The shape and direction variables may be any combination of those disclosed herein. The parameter sections may be planar or cylindrical. In an exemplary embodiment, the variables are modified to direct and redirect lift as needed, as described herein. The configured parameter sections are then used to form a blade by extrapolating between the parameter sections to form a smooth line. This method may be used to form any blade described herein.

[0070] The present invention encompasses several different devices incorporating the disclosed propellers. For example, the present invention includes, as exemplary devices, thrusters, shrouded propellers, in-case propellers, impellers, aircraft, watercraft, turbines, including wind turbines, cooling systems, heating systems, automobile engines, unmanned aerial vehicles, turboblowers (hydrojets), air circulation systems, compressors, pump jets, centrifugal fans, jet engines, etc. The present invention also includes methods of manufacturing and designing a propeller including any of the above-listed devices according to any of the embodiments described, illustrated, or claimed herein, methods of manufacturing a device comprising any of the above propellers, and methods of manufacturing a product, including the installation of a device incorporating any of the above propellers.

[0071] The ratio of roll to distance along the centerline can be a factor in whether a particular propeller is suitable for an application. For example, a greater roll per given distance creates a more squat blade profile, which may make it more suitable for cooling or ventilation fan applications.

[0072] In an exemplary embodiment, a propeller as described herein is incorporated into a turboblower, for example, as shown in Figures 10A and 10B. The turboblower may have, for example, eight or twelve blades. Note that the blades shown in Figures 10A and 10B are not necessarily of the type described herein; the drawings are provided merely to illustrate the type of device.

[0073] In another exemplary embodiment of the invention, a propeller as described herein is incorporated into an unmanned aerial vehicle or device, such as that shown in Figure 11. Note that the blades shown in Figure 11 are not necessarily of the type described herein; the drawing is provided merely to illustrate the type of device.

[0074] Various embodiments and views of exemplary propellers are provided in Figures 18A-18F, 19A-19F, 20A-20I, and 21A-21F. Views and perspectives from the top (top), bottom (bottom), "front" (front), "rear" (rear), "left" (left side), and "right" (right side) are provided and labeled. The terms "left," "right," "front," and "rear" are used solely to distinguish views at 90-degree intervals around the propeller and are not meant to be literal, given the circular device. Figures 18A-18F show an exemplary embodiment of a propeller with a high rake value for the blade intake. Figures 19A-19F show another exemplary embodiment of a propeller with a high rake value for intake and discharge. Figures 20A-20I show an inboard propeller. 21A-21F show a propeller with through-hub discharge for an outboard motor.

[0075] Various embodiments of the invention have been described, each having different combinations of elements. The invention is not limited to the particular embodiments disclosed, but may include different combinations of the disclosed elements or omission of some elements and equivalents of such structures.

[0076] While the present invention has been described in terms of exemplary embodiments, other advantages and modifications will occur to those skilled in the art. Therefore, the present invention in its broader aspects is not limited to the specific details shown and described herein. For example, changes in the number of blades and blade curvature can be made without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific exemplary embodiments, but is intended to be construed within the full scope of the appended claims and their equivalents. The present disclosure also includes the following aspects. [Aspect 1] 1. A propeller for use with a fluid, said propeller being provided to propel an object or person or to move said fluid, said propeller comprising: Multiple wings and a means for generating non-axial lift and non-axial fluid flow; means for redirecting the non-axial fluid flow into an axial fluid flow; a rotation axis that coincides with the hub; the plurality of blades extend radially outward from the rotational axis and are arranged about the rotational axis; each vane forming a loop-shaped structure and having an inlet portion, a discharge portion, and a tip portion extending radially outward from the axis of rotation; the means for generating non-axial lift and non-axial fluid flow comprises a blade configured such that, in a cross-sectional profile of each of the plurality of blades viewed perpendicularly from the axis of rotation through the tip, a distance from the axis of rotation to a leading edge of the blade is greater than a distance from the axis of rotation to a trailing edge of the blade at at least a portion of the tip, each of the plurality of blades having a roll value of 40 to 50 degrees at a transition point from the suction section to the tip, the transition point occurring when the amount of non-axial lift generated by a given parameter section is greater than the axial lift generated; and a propeller, wherein the means for redirecting the non-axial fluid flow into an axial fluid flow includes an apex angle of between -45 degrees and 45 degrees throughout the blades. [Aspect 2] 2. The propeller of claim 1, wherein the tip of the blade includes a blade section having a roll angle of 90 degrees. Aspect 3 2. The propeller of claim 1, wherein an apex angle for all portions of the tip of the blade is positive. Aspect 4 2. The propeller of claim 1, wherein the apex angle for all portions of the tip of the blade is negative. Aspect 5 2. The propeller of claim 1, wherein the blades have irregular spiral centerlines. Aspect 6 2. The propeller of claim 1, wherein the tip of the blade generates more non-axial lift than either the inlet or the outlet. Aspect 7 2. The propeller of claim 1, wherein the roll value of the parameter section of the blade at the tip transitions from a value below 90 degrees to a value above 90 degrees. Aspect 8 A propeller as described in aspect 1, wherein the blade is configured such that mean non-axial lift is greatest at the tip compared to either the inlet or the outlet, the inlet being 0-45% of the blade, the tip being 30-75% of the blade, and the outlet being 50-90% of the blade. Aspect 9 2. The propeller of claim 1, wherein the inlet portion of the blade extends a distance in the range of 10 percent to 50 percent of the blade centerline length, the discharge portion extends a distance in the range of 10 percent to 60 percent, and the tip portion extends a distance in the range of 5 percent to 60 percent. Aspect 10 2. The propeller of claim 1, wherein the roll value of the discharge section of the blade starting at the transition point from the tip is between 91 degrees and 135 degrees and transitions to a roll value of 180 degrees at the discharge root of the blade. Aspect 11 2. The propeller of claim 1, wherein the blades are configured to generate a mixed jet stream and free stream flow that encompasses an area of ​​diameter greater than the propeller. Aspect 12 2. The propeller of claim 1, wherein the inlet portion of the blade occupies a shorter distance than the outlet portion. Aspect 13 2. The propeller of claim 1, wherein the pitch angle of a parameter section transitions from about 70 degrees to about 35 degrees from the suction root to the discharge root of the blade, the pitch angle transitions from about 35 degrees to about 25 degrees over the next 50 percent of the blade, and the pitch angle transitions from about 25 degrees to about 75 degrees over the last 25 percent of the blade. Aspect 14 2. The propeller of claim 1, wherein the pitch angle is non-zero throughout the tip of the blade. Aspect 15 2. The propeller of claim 1, wherein the blade apex angle is zero for all parameter sections. Aspect 16 2. The propeller of claim 1, wherein the blade has a positive apex angle for all portions of the tip. Aspect 17 2. The propeller of claim 1, wherein the rake of the blade becomes increasingly negative from the suction root of the blade through the first 30 to 40 percent of the blade, then increases until it reaches a positive value over the next 10 to 15 percent of the blade, continues to increase over the next 20 to 40 percent of the blade, and then levels off or decreases for the remainder of the blade. Aspect 18 2. The propeller of claim 1, wherein the non-axial lift of the blades is generated by between 10 percent and 75 percent of the blades. Aspect 19 2. The propeller of claim 1, wherein the rake value of the blade decreases from the suction root of the blade to the suction section of the blade and increases to the discharge section of the blade. Aspect 20 2. The propeller of claim 1, wherein an average apex angle for the blade parameter section at the discharge section exceeds an average apex angle for the blade parameter section at the inlet section. Aspect 21 2. The propeller of claim 1, wherein the skew of the blades increases from the blade suction root throughout the propeller. Aspect 22 2. The propeller of claim 1, wherein the blade has an apex angle that is zero throughout the blade. Aspect 23 2. The propeller of claim 1, wherein the blade pitch angle is positive throughout the blade. Aspect 24 2. The propeller of claim 1, wherein a distance (N) from the axis of rotation to a leading edge of a cross section measured perpendicularly from the axis of rotation over at least a portion of the tip of the blade toward the end of the inlet of the tip before the roll reaches 90 degrees exceeds a distance (T) from the axis of rotation to a trailing edge of the cross section measured perpendicularly. Aspect 25 25. The propeller of claim 24, wherein 80% of the tip portions of the blades have a roll value less than 90 degrees, and N>T for the same 80% of the tip portions. Aspect 26 25. The propeller of claim 24, wherein an average pitch angle of the blades at the discharge section is greater than an average pitch angle of the blades at the inlet section. Aspect 27 2. The propeller of claim 1, wherein a rake position at an inlet root of the blade is lower than a rake position at a discharge root of the blade, providing a gap between the inlet root and the discharge root. Aspect 28 2. The propeller of claim 1, wherein the blade's suction root is forward of its discharge root, and the skew starts at zero and ends at a positive value. Aspect 29 2. The propeller of claim 1, wherein a pitch angle of the blades at the base ends of the discharge sections is greater than a pitch angle of the blades at the base ends of the inlet sections. Aspect 30 2. The propeller of claim 1, wherein the tip of the blade has a roll angle of 90 degrees closer to the discharge section than to the inlet section. Aspect 31 2. The propeller of claim 1, wherein the blades have a closed loop configuration. Aspect 32 2. The propeller of claim 1, wherein the blades have an open loop configuration. Aspect 33 The propeller is 2. The propeller of embodiment 1, in the form of a rim with blades extending radially inward from the rim. Aspect 34 2. The propeller of claim 1, wherein a roll angle of a blade section of the blade from the suction root to the discharge root of the blade is 0 to 180 degrees. Aspect 35 10. A turboblower having one or more propellers according to claim 1. Aspect 36 An unmanned aerial device having one or more propellers as described in embodiment 1. Aspect 37 10. A marine vessel having one or more propellers according to claim 1. Aspect 38 10. A jet engine having one or more propellers according to embodiment 1. Aspect 39 A device having the propeller according to embodiment 1 selected from the group consisting of a thruster, a shrouded propeller, a cased propeller, an impeller, an aircraft, a ship, a turbine including a wind turbine, a cooling device, a heating device, an automobile engine, an unmanned aerial vehicle, a turbo blower (hydrojet), an air circulation device, a compressor, and a pump jet. Aspect 40 2. The propeller of claim 1, wherein the tip of the blade has an apex angle of zero throughout. Aspect 41 2. The propeller of claim 1, wherein a pitch angle of the blade at the base end of the discharge section is smaller than a pitch angle of the blade at the base end of the inlet section. Aspect 42 2. The propeller of embodiment 1, defined by a planar parameter section. Aspect 43 2. The propeller of claim 1, wherein the inlet section has a higher average pitch value than the average pitch value of the outlet section. Aspect 44 2. The propeller of claim 1, wherein the transition from the inlet to the tip occurs when the amount of non-axial lift generated by a given parameter section of the blade exceeds the axial lift generated. Aspect 45 45. The propeller of claim 44, wherein the transition from inlet to tip occurs when the roll is 45 degrees. Aspect 46 The propeller is 2. The propeller of embodiment 1, having a hub with blades extending radially outward from the hub. Aspect 47 2. The propeller of claim 1, wherein the rake value of the blade decreases at the inlet portion of the blade from the inlet root of the blade and increases at the outlet portion of the blade. Aspect 48 16. The propeller of claim 15, wherein the blade's discharge root is forward of its suction root, and the skew starts at zero and ends at a negative value.

Claims

1. A method of manufacturing a propeller (100) having a plurality of blades (400), each having an inlet portion (406), a discharge portion (426), and a tip portion (404) extending from the inlet portion (406) to the discharge portion (426), the method comprising: defining a plurality of parameter sections by selecting some of the parameters including values ​​for skew angle, roll angle, rake, radius, pitch angle, and apex angle; parametrically defining a parameter section at a transition from the intake section (406) to the tip section (404) such that the amount of non-axial lift at the tip section (404) is greater than the axial lift at the tip section (404); defining a parameter section to include a 90 degree roll value for said tip (404); and extrapolating between the parameter sections to form a smooth line to form a vane configured to form a loop when attached to the hub (128).

2. The method of claim 1 , comprising aligning the parameter sections along an irregular spiral centerline.

3. 3. The method of claim 1, further comprising forming the hub (128) with a plurality of vanes (400) extending outwardly from the hub (128), the plurality of vanes (400) being disposed about the hub (128).

4. 4. The method of claim 1, further comprising defining one or more parameters in an inlet parameter section to reduce the amount of non-axial lift at the inlet compared to the non-axial lift at the tip, and / or defining one or more parameters in an exhaust parameter section to reduce the amount of non-axial lift at the exhaust compared to the non-axial lift at the tip.

5. 5. The method of claim 1, comprising selecting parameters including an average pitch angle of the discharge section of the blade that is greater than an average pitch angle of the inlet section, and / or selecting parameters such that a root of the inlet section is forward of a root of the discharge section, wherein the skew starts at zero at the root of the inlet section and ends at a positive value at the root of the discharge section.

6. 6. The method of claim 1, comprising selecting parameters comprising a pitch angle of the root of the discharge section (426) that is greater than a pitch angle of the root of the inlet section (406).

7. 6. The method of claim 1, comprising selecting parameters comprising a pitch angle at a root of the discharge section (426) that is less than a pitch angle at a root of the inlet section (406).

8. 8. The method of claim 1, comprising selecting parameters in a parameter section such that the tip (404) has a roll angle of 90 degrees closer to the discharge (426) than to the inlet (406).

9. The method of any one of claims 1 to 8, comprising selecting parameters that include a zero apex angle throughout the tip (404).

10. The method of any one of claims 1 to 9, wherein the parameter section is planar.

11. 11. The method of claim 1, comprising selecting parameters such that, for at least a portion of the tip (404) of the blade upstream from a 90-degree roll, a distance (N) from a leading end of the parameter section measured perpendicular to a direction in which the blade extends outward from the axis of rotation toward the suction end of the tip (404) is greater than a distance (T) from a trailing end of the parameter section measured perpendicular to the axis of rotation, wherein 80% of the tip (404) has a roll value less than 90 degrees and N is greater than T for the same 80% of the tip (404).

12. The method of any one of claims 1 to 11, comprising selecting parameters including a non-zero pitch angle across the tip (404).

13. 13. The method of claim 1, comprising selecting parameters including an average apex angle of a parameter section of the discharge section (426), wherein the average apex angle of the parameter section of the discharge section (426) is greater than the average apex angle of a parameter section of the inlet section (406).

14. 14. The method of any one of claims 1 to 13, comprising selecting parameters including a rake in a parameter section that gradually increases negatively from the root of the inlet section (406) for the first 30 to 40 percent of the blade, then increases until it reaches a positive value for the next 10 to 15 percent of the blade, continues to increase until it reaches a positive value for 20 to 40 percent of the blade, and then levels off or decreases for the remainder of the blade.

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