A BLADE COMPONENT FOR A PROPELLER

Abstract

 The invention relates to a blade component for a propeller. The blade component comprises a base which is attachable to a portion of a propeller hub to at least partially enclose the hub and form at least one open ended passage in the hub to permit flow there through. At least one propeller blade extends substantially radially outwardly from the base, and the at least one blade includes a blade face, a blade back, a leading edge, a trailing edge, and a root section connected to the base. An inlet opening is configured on the base which permits flow from the outside to the inside of the enclosed hub. The base or the hub further include a compartment which sub-divides the open ended passage and forms a further water flow passage when the base is attached to the hub, wherein the operatively forward end of the compartment is closed, and the opposing end is open such that water enters the water flow passage through the inlet opening and is directed to flow there through and exit the rear end of the enclosed hub. The inlet opening is configured to run substantially parallel to the axis of the hub, and the inlet opening is further located in register with the water flow passage there below and substantially adjacent to one side of the compartment.

Description

Background of the invention

[0001] The invention relates to a blade component for a propeller and more particularly, but not exclusively, to a blade component for a modular propeller for use with inboard and outboard boat engines.

[0002] A propeller is a device that transmits power by converting rotational motion into thrust. A pressure differential is produced between forward and rear surfaces of the airfoil-shaped blade, and a fluid (such as air or water) is accelerated behind the blade, thus resulting in thrust required to drive a motorized vessel to which the propeller is attached. One specific type of propeller is a propeller for use as a means of propulsion in boat engines, whether outboard or inboard.

[0003] Many different propeller designs are known in the trade, and they all share some of the same design characteristics. A propeller comprises a plurality of blades extending radially outwardly from a central rotating hub. Each blade is shaped in the form of an airfoil having two opposite surfaces, being a blade face (which is the pressure side of the blade facing the stern), and the blade back (which is the suction side of the blade facing the bow). Each blade furthermore includes a leading edge, which is the edge of the propeller adjacent the forward end of the hub. The leading edge leads the blade into the flow when the propeller is providing forward thrust. The opposing edge is referred to as the trailing edge, and the radially outer zone extending between the leading edge and the trailing edge is referred to as the blade tip. The root of the blade is the fillet area in the region of transition between the blade surface and the hub periphery.

[0004] Blade surface area refers to the total surface area of the propeller blade. When a propeller rotates on a fixed axis for any period of time a centrifugal force creating a negative pressure on the blade back of each rotating blade draw water inwards, and when the oncoming blade face comes into contact with the inward flow of water the water is compressed. A positive pressure is therefore induced, and the water in this positive pressure zone then exerts a force against the adjacent body of water, resulting in thrust. Standard blade designs permit the inward flow of water to flow over the entire curvature of the blade back. Studies have confirmed that in excess of 40% of the potential energy is not harnessed because on average only 60% of the negative pressure water mass is compressed by the blade face of an oncoming blade. Further potential energy is lost between the blade roots of each blade back, which fragments the flow of water when the positive pressure water mass collides with the negative pressure water mass. This disturbance affects the volume of water that gets displaced and thereby reducing the amount of useful thrust. It would obviously be beneficial if a way could be found to harness as much of the potential energy in order for the full potential energy of the water flow to be utilized. In addition, it would also be beneficial if a better way could be found to improve the behavioral flow of the exhaust gasses flowing through the hub so that the exhaust gases do not flow over into the blades under certain maneuvering conditions.

[0005] The inventor devised US 9,701,379 which was intended to address the above shortfalls and attempted to harness some of the wasted potential energy in order for the full potential energy of the water flow to be utilized. US 9,701,379 relates to a propeller for use with inboard and outboard boat engines. The propeller includes a hollow hub and a plurality of primary blades extending radially outwardly from the hub. The propeller includes a set of secondary blades inside the hub. The secondary blades are preferably located on a hub insert which fits inside the hub, which forms an annular volume between the inner surface of the hub and the outer surface of the hub insert. An inlet opening is located at the root of the blade on the blade face side of the primary blade (side facing backwards from the boat). The inlet opening permits for the inner annular volume to be in flow communication with a volume outside of the hub, in particular the space between two adjacent primary propeller blades. The propeller of the invention further includes tertiary blades which extend from the hub insert, each tertiary blade located between two adjacent secondary blades such that the secondary and tertiary blades divide the annular volume between the hub and the hub insert to form alternating water and exhaust gas flow passages. The water flow passage in the annular volume is in flow communication with the space between two adjacent primary blades by way of the inlet opening. The exhaust gas flow passage is in flow communication with an exhaust gas outlet of an engine to which the propeller is secured. According to the invention, the inlet opening extended substantially along the length of the root of the blade, and this resulted in superior performance.

[0006] The propeller illustrated in US 9,701,379 patent is also known as the Magblade propeller. It was designed with polymer over-molded safety sleeves that protected the leading edge of the blades from been damaged when striking a submerged object. The safety sleeves were disclosed in US 2015/0191233 A1. The other advantage of the safety sleeves was that it prevented cavitation forming on the leading edge of the blades due to the polymer safety sleeves flexing in both directions and thereby producing a differential pressure depending of the degree of flex of the safety sleeves. This prevented the formation of a low pressure on the leading edge of the blades and therefore cavitation could never form on the leading edge of the blades. The major drawback from having over-moulded safety sleeves on the leading edge of the blades was that the blades had to be much thicker than conventional blades in order to accommodate the safety sleeves which reduced the wide open throttle (WOT) speed that the outboard motor could achieve.

[0007] The Magblade propeller also included an anti-drag fin, which is disclosed in US 2015/0217846. This feature redirects the full flow of the water been drawn onto the back of the blades into the face of the oncoming blades which it effective does. The result however is that the blades loses significant lift and permits low pressure of the back of the blades to be injected ahead of the high pressure been thrust from the face of the blades which results in a reduced useful thrust and the formation of increased cavitation.

[0008] A Computational Fluid Dynamics (CFD) analysis was conducted which digitally analysed the performance of the propeller incorporating the invention, the Magblade propeller with thinner blades and without safety sleeves and a Solas™ aluminum propeller.

[0009] The CFD analysis revealed that the anti-drag fin on the back of each blade is causing the propeller to lose lift which will result in the Magblade propeller loosing pressure at the very leading and trailing edge of the blades. Due to the reduction in lift a lower pressure is generated on the face of the blades which produces less useful thrust.

[0010] It also revealed that the Magblade with thinner blades and without safety sleeves demonstrated an excessive and undesirable amount of cavitation that will affect the performance thereof. It was determined that the Magblade propeller produces excessive drag on the back of the blades as the pressure on the back of the blades is non-conductive to be able to be able draw water over the back of the blades at the desired level of acceleration required in order to create the desired amount of lift.

Summary of the invention

[0011] It is an object of the invention to provide a blade component for a propeller that will at least partially alleviate the above mentioned drawbacks and will improve performance and efficiency of the propeller the blade component is incorporated in.

[0012] According to the invention there is provided a blade component for a propeller comprising:

a base which is attachable to a portion of a propeller hub to at least partially enclose the hub and form at least one open ended passage in the hub to permit flow there through;

at least one propeller blade extending substantially radially outwardly from the base, and the at least one blade includes a blade face (operative rear end of the blade component and propeller formed), a blade back (operative rear end of the blade component and propeller formed), a leading edge, a trailing edge, and a root section connected to the base;

an inlet opening configured on the base which permits flow from the outside to the inside of the enclosed hub;

the base or the hub further including a compartment which sub-divides the open ended passage and forms a water flow passage when the base is attached to the hub, wherein the operatively forward end of the compartment is closed, and the opposing end is open such that water enters the water flow passage through the inlet opening and is directed to flow there through and exit the rear end of the enclosed hub;

wherein the inlet opening is configured to run substantially parallel to the axis of the hub, and the inlet opening is further located in register with the water flow passage there below and substantially adjacent to one side of the compartment.

[0013] In the preferred form of the invention, the base is configured with the compartment, the base is curved and the hub is configured with receiving formations for receiving the curved base. The receiving formations are preferably slots configured in the outer surface of the hub. The hub preferably includes three slots.

[0014] The base may be secured in the hub by a securing means.

[0015] The blade includes a flow guide. The flow guide is in the form of a raised lip extending along the contour of the trailing edge of the blade back. In use, the flow guide redirects the flow of low-pressure water drawn onto the blade back into the oncoming face of the adjacent blade without reducing the lift generated by a camber of the blade back. This harnesses almost all of the potential energy and thereby increases the amount of usable thrust, thereby improving the efficiency of the propeller.

[0016] The compartment is substantially U-shaped in plan view. The compartment is formed by a single elongate wall or a set of adjoined walls, either of which extend inwards from the inner surface of the base. The compartment is preferably formed by the single elongate wall which is substantially U-shaped in plan view.

[0017] The sub-divided open ended passage forms the water flow passage and a discrete exhaust gas flow passage. The compartment permits the separation of the exhaust gasses that are expelled by the motor through the hub and the water and objects of mass that are drawn into the inlet openings. The passages are isolated from each other, and exhaust gasses will not enter the water passage, and vice versa.

[0018] The compartment is formed by two opposing side wall portions which extend substantially parallel to the axis of the hub, with a further wall portion of the compartment which closes the operatively forward end of the compartment. Water enters the water flow passage formed by the compartment via the inlet opening, and the water exits the water flow passage at a rear open end thereof and out of the open rear end of the hub.

[0019] A portion of the closed forward end wall portion of the compartment is angled, curved or kinked. The result of the angle, curve or kink is that one of the two side wall portions is longer than the other. The longer of the two side wall portions is located along the leading edge side of the blade component. The inlet opening is located against the longer of the two wall portions.

[0020] The water and objects of mass enter the water flow passage through the inlet opening and are forced against the angled, curved or kinked wall, and the water and objects of mass are propelled outward from the water flow passage as a result of the centrifugal forces generated by the rotating propeller. A secondary form of thrust in forward motion is generated as a result of the above. The configuration of the compartment and inlet also prevents exhaust gases from flowing into the blades when reversing the propeller.

[0021] The exhaust gas flow passage is in flow communication with an exhaust outlet of an engine to which the propeller is secured. In use, the exhaust gas enters the exhaust gas flow passage from an open end thereof, at the front end of the hub, and will exit the exhaust gas flow passage at a rear end of the hub.

[0022] The compartment is configured on the base in such a way that when the base is attached to the hub, the exhaust gas flow passage comprises a single passage at the operatively forward end region thereof and splits into two narrower passages thereafter located on either side of the compartment, as a result of the positioning of the compartment within the open ended passage. This results in the exhaust gasses being compressed as they flow through the split exhaust gas flow passages and expelled out and away from the propeller. This results in additional form of thrust being generated.

[0023] The inlet opening is preferably a generally tear-drop shaped vent. A side of the vent is tapered to increase the flow of the water and objects of mass drawn into the compartment. The width of the operatively forward end of the vent is greater than the width of the operatively rear end of the vent.

[0024] According to another aspect of the invention there is provided a modular propeller comprising a plurality of propeller blade components described above attached to the hub as described above. The hub may be modular, comprising a core body having a central passage there through. The core body may include walls extending outwards from the core body and along the length thereof. Curved members may be configured to be attachable to an end each of the walls, thereby forming the slots wherein the base of the propeller component may slot into. The modular hub may further include a ring member which is fixed to core body or may be attachable to the core body, wherein when in place it forms the closed end of the hub.

[0025] According to another aspect of the invention there is provided a single unit propeller comprising a plurality of the propeller blade components described above which are integral to the hub as described above. The hub may be configured as described above in the modular version, however, instead of being modular in nature the hub parts are fixed together or are manufactured being integral to each other.

[0026] The configuration of the inlet opening and the wall arrangement assists in improving velocity and useful thrust of a propeller in use, the propeller being formed by the enclosed hub, wherein the pressure inside the water flow passage is maintained at a pressure which is lower than the pressure outside the enclosed hub, and furthermore, a greater pressure is generated at both the back and face of the blades, and there is a reduction in the disruption of the velocity of the thrust generated by the face of the blades as the forces exerted by the water drawn onto the back of the blades and thrust off the face of the blade remains substantially equal to the opposite reacting forces or forces of the vortices created by the propeller in use.

Brief description of the drawings

[0027] The invention shall be explained by way of reference to the following non-limiting drawings, in which:

Figure 1

is a top rear perspective view of a blade component for a propeller;

Figure 2

is a bottom rear perspective view of the blade component;

Figure 3

is a top rear perspective view of the blade component;

Figure 4

is a top front perspective view of the blade component;

Figure 5

is a front view of the blade component;

Figure 6

is a rear view of the blade component;

Figure 7

is a right side view of the blade component;

Figure 8

is a left side view of the blade component;

Figure 9

is a top view of the blade component;

Figure 10

is a bottom view of the blade component showing a plan view of the compartment on the base;

Figure 11

is a front perspective view of the hub;

Figure 12

is a rear perspective view of the hub;

Figure 13

is a front perspective view of an assembled propeller comprising a plurality of blade components attached to the hub;

Figure 14

is a rear perspective view of the assembled propeller;

Figure 15

is a front view of the assembled propeller;

Figure 16

is a rear view of the assembled propeller;

Figure 17

is a left side view of the assembled propeller;

Figure 18

is a top rear perspective view of a second embodiment of the blade component for a propeller;

Figure 19

is a bottom rear perspective view of the second embodiment of the blade component;

Figure 20

is a front perspective view of the hub;

Figure 21

is a rear perspective view of the hub;

Figure 22

is a representation showing the results of a useful thrust analysis of the Solas™ propeller;

Figure 23

is a representation showing the results of a useful thrust analysis of the Magblade propeller;

Figure 24

is a representation showing the results of a useful thrust analysis of the propeller which incorporates the invention;

Figure 25

is a representation showing the results of a flow analysis of the Solas™ propeller;

Figure 26

is a representation showing the results of a flow analysis of the Magblade propeller;

Figure 27

is a representation showing the results of a flow analysis of the propeller incorporating the invention;

Figure 28

is a representation showing the results of a cavitation analysis of the Solas™ propeller;

Figure 29

is a representation showing the results of a cavitation analysis of the Magblade propeller;

Figure 30

is a representation showing the results of a cavitation analysis of the propeller incorporating the invention;

Figure 31

is a back view representation showing the results of a displacement analysis of the Solas™ propeller;

Figure 32

is a front view representation showing the results of the displacement analysis of the Solas™ propeller;

Figure 33

is a back view representation showing the results of a displacement analysis of the Magblade propeller;

Figure 34

is a front view representation showing the results of the displacement analysis of the Magblade propeller;

Figure 35

is a back view representation showing the results of a displacement analysis of the propeller incorporating the invention; and

Figure 36

is a front view representation showing the results of the displacement analysis of the propeller incorporating the invention.

Detailed description of the invention

[0028] It should be appreciated to those skilled in the art that, without derogating from the scope of the invention as described, there are various alternative embodiments or configurations or adaptions of the invention and its features.

[0029] Referring to the drawings, in which like numerals indicate like features, a non-limiting example of the blade component in accordance with the invention is generally indicated by reference numeral 10.

[0030] Referring to Figures 1 to 10, the blade component 10 for a propeller comprises a curved base 12, a propeller blade 14, a tear-drop shaped vent 16, and a compartment 18 configured on the inner surface of the base 12.

[0031] The base 12 is configured to be attachable to a portion of a propeller hub 20 shown in Figures 11 and 12. When the base 12 is attached, the hub 20 is at least partially enclosed and an open ended passage 20.1 formed which permits flow through the hub 20. Referring to Figures 11 and 12, the hub 20 is configured with three large slots 20.2 for receiving three bases 12, each being configured in the outer surface 20.3 of the hub 20. The slots 20.2 extend along a portion of the outer surface 20.3 such that the bases 12 are slotted in from an open end of the hub 20, and engage with a closed end 20.4 of the outer surface 20.3. Once the three bases 12 are slotted into the slots 20.2 and secured in place, the assembled propeller 100 is formed as shown in Figures 13 to 17.

[0032] The propeller blade 14 extends substantially radially outwardly from the base 12. The blade 14 includes a blade face 14.1, a blade back 14.2, a leading edge 14.3, a trailing edge 14.4, and a root section 14.5 connected to the base 12.

[0033] The blade 14 includes a raised lip 14.6 which acts as a flow guide. The raised lip 14.6 shown in Figures 4, 5, 7, 10, 13, 15 and 17 extends along the contour of the trailing edge 14.4 of the blade back 14.2. In use, the raised lip 14.6 redirects the flow of low-pressure water drawn onto the blade back 14.2 into the oncoming face 14.1 of the adjacent blade without reducing the lift generated by a camber of the blade back 14.2.

[0034] The tear-drop shaped vent 16 as shown in Figures 1 to 3, 8, 10, 13, 14, 17 is configured on the base 12 which permits flow from outside the base 12 and hub 20 when enclosed, into the open ended passage 20.1.

[0035] The compartment 18 sub-divides the open ended passage 20.1 when the base 12 is attached to the hub 20 to form a discrete water flow passage 22.1 and a discrete gas exhaust flow passage 22.2, 22.3, 22.4. The compartment 18 permits the separation of the exhaust gasses that are expelled by a motor connected to the propeller in use, from the water and objects of mass that are drawn into the vent 16.

[0036] Referring to Figures 2 and 10, the compartment 18 is formed by the single elongate wall 24 which is substantially U-shaped in plan view. The single elongate wall 24 is made up of two opposing side wall portions 24.1, 24.2, a longer wall portion 24.1 and a shorter wall portion 24.2 which extend substantially parallel to the axis of the hub 20, and a kinked wall portion 24.3 which closes the operatively forward end 18.1 of the compartment 18. The opposing end of the compartment 18 is open such that water enters the water flow passage 22.1 through the slot 30 and is directed to flow there through and exit the rear end of the hub 20 when enclosed. The vent 16 is configured to run substantially parallel to the axis of the hub 20, when the base 12 is attached to the hub 20. The vent 16 is further located in register with the water flow passage 22.1 there below. The longer wall portion 24.1 is located along the leading edge side of the blade component 10, and the vent 16 is located adjacent the longer wall portion 24.1.

[0037] The water and objects of mass enter the water flow passage 22.1 through the vent 16 and are forced against the kinked wall portion 24.3, and the water and objects of mass are propelled outward from the water flow passage 22.1 as a result of the centrifugal forces generated by the propeller, when rotating in use.

[0038] The exhaust gas flow passage 22.2, 22.3, 22.4 is in flow communication with an exhaust outlet of the motor (not shown) to which the propeller can be secured. In use, the exhaust gas enters the exhaust gas flow passage 22.2, 22.3, 22.4 from an open end of the open end passage 20.1 at an operatively forward end 20.5 of the hub 20, and exits the exhaust gas flow passage 22.2, 22.3, 22.4 at an operative rear end 20.6 of the hub 20.

[0039] The compartment 18 is configured on the base 12 in such a way that when the base 12 is attached to the hub 20, the exhaust gas flow passage 22.2, 22.3, 22.4 comprises a single wider passage 22.3 at the operatively forward end region thereof and splits into two narrower passages 22.3, 22.4 thereafter, which are located on either side of the compartment 18.

[0040] Referring to Figures 18 to 21, another embodiment of the propeller blade component 10A is shown in Figures 18 and 19, which is attachable to the propeller hub 20A shown in Figures 20 and 21. The tear-drop shaped vent 16 on the base 12 is retained. This version of the invention only differs from the version shown in Figures 1 to 10, in that the compartment 18 is configured on a surface 20A.1 of the hub 20A. When the blade component 10A is attached to the hub 20A, a propeller is assembled which is similar to the propeller shown in Figures 13 to 17, and which functions in the same way and has the same advantages thereof.

[0041] The advantages and improvements of the invention shall also be described and illustrated with reference to a Computational Fluid Dynamics (CFD) analysis report, in which a performance comparison was conducted between a propeller incorporating the invention, the Magblade propeller with thinner blades and without safety sleeves, and a Solas™ propeller. The Solas™ propeller was selected for comparison based on the grounds that Solas™ is one of the leading propellers manufacturers in the world and that there are numerous existing reviews which rate the Solas™ brand of propellers very highly against its competitors. The Magblade propeller was selected in order to compare the advances in technology since the original design of the Magblade propeller.

[0042] The CFD results will explain in detail what makes the propeller incorporating the invention superior to any other propeller on the market including the Magblade propeller.

[0043] All three of the propellers analysed are of a 17" pitch and 13.25" diameter and the results were calculated at a speed of 5500 RPM with a gear ration of 2.33 and at 30.5 propeller rotations per second, which equates to a velocity of 13.17 meters per second.

[0044] The CFD analysis revealed that the anti-drag fin on the back of each blade of the Magblade causes the propeller to lose lift which will result in the Magblade propeller loosing pressure at the very leading and trailing edge of the blades. The only reason why the present Magblade propeller produces as much velocity is it does compared to that of the Solas™ propeller, is due to the flow of the water been drawn onto the back of the blades and then been redirected into the face of the oncoming blades. Due to the reduction in lift a lower pressure is generated on the face of the blades which compared to that of the Solas™ propeller, produces less useful thrust than both the propeller incorporating the invention and Solas™ propellers.

[0045] Referring to Figure 22, the useful thrust is being displaced outwards from the blades of the Solas™ propeller, thereby minimizing the amount of useful thrust. The propeller, when in motion, pushes water backward with an action force and according to Newton's 3^rd law, water exerting an equal and opposite reaction force pushes the propeller and the boat in a forward direction. As a result, the boat keeps on moving as long as the propeller keeps rotating. However, the equal forces on the Solas™ are pushed outward away from the face of the blades due to the injected low pressure flows, resulting in a loss of useful thrust. The more lighter the shade of the arrows, the greater the velocity, and the greater the useful thrust. The darker the shade of the arrows is, the lower the velocity. The greater the deviation of the high velocity from the low velocity, the more turbulent and less inefficient the thrust becomes. Due to the manner in which the low pressures flow between the blades and is injected ahead of the higher pressure from the blades by the diffuser ring at the back of the Solas™ propeller's hub, the low pressure intersects with the high pressure being thrust from the face of blades resulting in inconsistent pressures that disrupt the flow of velocity.

[0046] Referring to Figure 23, the useful thrust analysis result of the Magblade propeller is similar to the Solas™ propeller's useful thrust. The useful thrust analysis result for the propeller incorporating the invention is shown in Figure 24. It reveals that it produces a far greater amount of useable thrust than that presented by the Solas™ propeller and by the Magblade propeller. Like the Magblade propeller the propeller incorporating the invention has unique design features that work efficiently to harness all the potential energy produced by the propeller in order to produce an unmatched degree of useful thrust. Unlike the Magblade propeller that has a raised lip at the back center of each blade to redirect the flow of the water been drawn onto the back of the blade into the oncoming blade, the propeller incorporating the invention has a reverse cupping that functions in the opposite function to the cupping on the front of the blade. The cupping on the front of the blade enable the propeller to grip the water better and thereby limiting the amount the propeller slips through the water. The reverse cupping redirects the follow flow of the water from the back of the blade into the oncoming blade however does not reduce the life produced off the back of the blade. This is due to the fact that the reverse cupping runs parallel to the trailing edge of the back of the blade.

[0047] Unlike the Magblade propeller that has a separate vortex hub the propeller including the invention has a compartment which forms a water flow passage under the base of the blade when the base is attached to the hub, and which generates of vortex flow of objects with mass that are drawn into the flow passage via vents located on the base, which run parallel to the one wall of the compartment. The pressure inside the flow passage is maintained lower than the pressure outside the hub and due to the centrifugal forces from the rotation of the propeller, this causes objects with mass to be sucked into the flow passage and propelled out the flow passage as a secondary form of thrust. In addition to this, the compartment creates gaps or flow passages on either side to permit the exhaust gasses produced by the outboard motor to be compressed and like the objects with mass, the exhaust gasses flow through these passages also to act as an additional form of propulsion.

[0048] Referring to Figure 25, the flow analysis of the Solas™ propeller is shown. It becomes very evident how inefficient it is. The visible contours indicate the behavioural flow of the surrounding water and the arrows indicate the degree of velocity and the direction of the flow of energy been produced. The surrounding shades around the blades indicates the degree of pressure being generated by water that is drawn onto the back of the blades and thrust off the face of the blades. The darker the shades, the greater the amount of pressure generated, which results in greater thrust. As a result of the low pressure flows being injected ahead of the high pressure flow, the energy being thrust begins to dissipate when the vortices start to envelope the energy produced by the thrust, thereby producing extremely turbulent flow. As in Newton's 3^rd law of motion, there must be an equal and opposite reaction of force. However, the force of the vortices is not equal to that of the thrust, and therefore the energy from the thrust is dissipated through the vortices. This energy loss is qualified by the size of the arrows illustrated in Figure 25. The larger the arrows the greater the velocity, which means the greater the thrust. The closer the arrows get to the vortices, the smaller they get, up to the point where the velocity eventually become insignificant.

[0049] Referring the Figure 26, the Magblade propeller demonstrates the most turbulent flow. The lack of pressure being thrust from the face of the blades as a result of the reduced lift is evident by the shades surrounding the blades. Due to the low pressure that is injected between the blades along with the higher pressure that is thrust from the face of the blades, a significant amount of turbulence is generated behind the propeller resulting in a reduced flow of thrust, as is visually represented in the contour flow behind the propeller. This demonstrates that the Magblade propeller has the least efficient out of the three propellers compared, and it produces the least amount of useful thrust at the same given RPM.

[0050] The flow contours of the propeller which includes the invention are co-efficient and do not produce any vortices that disrupt the velocity of the thrust generated by the face of the blades. The forces exerted by the water remain equal to that of the opposite reacting forces, maximizing the amount of useful thrust. This maintained energy is qualified by the size of the arrows in Figure 27, as the arrows remain almost constant in size across the velocity spectrum and only begin to decrease in size when the propeller is some distance from the original point of displacement. The evidence of significantly darker shades surrounding the propeller demonstrate that a greater pressure is generated off both the back and face of the blades thereby producing more thrust. This evidence demonstrates that the propeller incorporating the invention is evidentially more efficient than the Solas™ and Magblade propellers and produces far more useful thrust at the same given RPM.

[0051] Referring to Figure 28, the leading edge of a blade of the Solas™ propeller show the effect of the low pressures spilling over onto the leading edge of the blades. This indicates that there are small traces of cavitation present. As a result of this cavitation, the pressure drops at the leading edge of the blade which is evident from the darker shades at the leading edge of the blade. This drop in pressure results in the cavitation of the propeller on both sides of each blade, as the pressure becomes lower than that of the surrounding pressure. The cavitation results in the formation of air bubbles which vaporize and eventually implodes on the surface on both sides of each blade. This damages the propeller and ultimately affects the performance of the propeller. The other knock-on effect caused by cavitation, is that the propeller beings to resonate and the vibrations are transferred to the propeller shaft of the outboard motor. Excessive and prolonged cavitation will shorten the lifespan of the gear box and power head of the outboard motor.

[0052] The Magblade propeller shown in Figure 29 demonstrates excessive and an undesirable amount of cavitation that will affect the performance of the propeller. As mentioned with the Solas™ propeller, an excessive amount of cavitation will damage the propeller and will shorten the lifespan of the gear box and power head of the outboard motor.

[0053] Referring to Figure 30, the propeller incorporating the invention does not demonstrate cavitation's at all. This is owing to the fact the there are no low pressures spilling over the leading edge of the blades. The lack of evidence in the formation of cavitation does not mean that a small amount of cavitation would not form on the leading edge of the blades, but rather it demonstrates that if cavitation had to form it would be insignificant to affect the performance of the propeller.

[0054] Referring again to Figures 28 and 29, the reason why a pressure differential can be seen in both the Solas™ and the Torpeller propeller is as a result of the leading edge of the blade turning much faster than the root of the blade, which causes a change in pressure at the leading edge of the blade. However, in the case of the propeller incorporating the invention, the pressure differential is not sufficient enough to produce cavitation on the leading edge of the blade, as can be seen in Figure 30. This provides evidence that the propeller including the invention will not produce cavitation that will affect the performance of the propeller, unlike that of the Solas™, and even more so the Magblade propeller.

[0055] The back and front views of the Solas™ propeller shown in Figures 31 and 32 illustrate how inefficiently the water will be displaced by the Solas™ propeller, as the pressure variance is even across the back and front of the blades with mid to high pressures generated on the back of the blade as well as on the front of the blade as indicated by the lighter shades.

[0056] Although the Solas™ propeller achieves suitable RMP's and speed within WOT band, the lack of useful thrust is clearly evident and so is the non-coefficiency of the propeller. This will result in longer hole-shot times (time to plane) and longer time and distance to reach WOT speed. The water being displaced from the face of the blades is displaced outwards and away from the initial point of origin, thereby creating a larger propeller wake and introducing more propeller wash. Consequently, this increases the drag which increases the total amount of slip added to the boats forward momentum. A propeller that achieves a suitable speed at high RPM's does not necessarily make it an efficient propeller. As a result of today's rising fuel costs, to save any amount of money on fuel on a day's outing on the water makes an enormous difference. This translates to more savings over a few outings, as well as a season.

[0057] The Magblade propeller results illustrated in Figures 33 and 34 when compared to those shown in Figures 31 and 32 of the Solas™ propeller, reveal that the Magblade propeller is producing excessive drag on the back of the blades as the pressure on the back of the blades is nonconductive to be able to be able draw water over the back of the blades at the desired level of acceleration required in order to create the desired amount of lift. The lack of acceleration of the water drawn over the blades is evidenced by the lighter shades as also visible on the back of the blades. The slightly darker shades in the proximity of the anti-drag fines is a clear indication that there is a reduction of lift from the back of the blades. The pressure on the front of the blades as can be seen by the lighter shades on the front of the blades is closely represented by that on the back of the blades, which is further evidence that there is a reduction of lift even though the water being drawn over the back of the blades is being redirected into the oncoming blades.

[0058] Referring to Figures 35 and 36, the propeller incorporating the invention, when compared to the results shown in Figures 31 to 32 of the Solas™ propeller, and to the results shown in Figures 33 to 34 of the Magblade propeller, reveal a completely different set of results. The back of the blades produce a far lower pressure indicated by the darker shade shown in Figure 35, which draws water over the back of the blades quickly due to the reverse cupping, and the full flow of the water is redirected into the oncoming blade as is indicated by the dark shade seen in Figure 36. The results illustrate that the propeller of the invention displaces a greater amount of water than the Solas™ propeller and the Magblade propeller without putting any additional load on the outboard or inboard motor.

[0059] The unique design features of the propeller incorporating the invention harness previously unused potential energy, it also improves distribution of low pressure flows and better management of the exhaust gasses.

Claims

1. A blade component for a propeller comprising:

a base which is attachable to a portion of a propeller hub to at least partially enclose the hub and form at least one open ended passage in the hub to permit flow there through;

at least one propeller blade extending substantially radially outwardly from the base, and the at least one blade includes a blade face, a blade back, a leading edge, a trailing edge, and a root section connected to the base;

an inlet opening configured on the base which permits flow from the outside to the inside of the enclosed hub; characterised in that

the base or the hub further includes a compartment which sub-divides the open ended passage and forms a water flow passage when the base is attached to the hub, wherein the operatively forward end of the compartment is closed, and the opposing end is open such that water enters the water flow passage through the inlet opening and is directed to flow there through and exit the rear end of the enclosed hub; and

wherein the inlet opening is configured to run substantially parallel to the axis of the hub, and the inlet opening is further located in register with the water flow passage there below and substantially adjacent to one side of the compartment.

2. The blade component as claimed in claim 1, wherein the base is configured with the compartment.

3. The blade component as claimed in claim 1, wherein the base is curved and the hub is configured with receiving formations for receiving the curved base.

4. The blade component as claimed in claim 1, wherein the blade includes a flow guide in the form of a raised lip extending along the contour of the trailing edge of the blade back.

5. The blade component as claimed in claim 1, wherein the compartment is substantially U-shaped in plan view.

6. The blade component as claimed in claim 1, wherein the compartment is formed by a single elongate wall or a set of adjoined walls.

7. The blade component as claimed in claim 2, wherein the compartment is formed by a single elongate wall or a set of adjoined walls, either of which extend inwards from the inner surface of the base.

8. The blade component as claimed in claim 1, wherein the sub-divided open ended passage forms the water flow passage and a discrete gas exhaust flow passage which permits the separation of the exhaust gasses that are expelled by the motor through the hub and the water and objects of mass that are drawn into the inlet openings, and wherein the exhaust gas flow passage is in flow communication with an exhaust outlet of the motor to which the propeller is secured, such that in use, the exhaust gas enters the exhaust gas flow passage from an open end thereof, at the front end of the hub, and exits the exhaust gas flow passage at a rear end of the hub.

9. The blade component as claimed in claim 6, wherein the compartment is formed by two opposing side wall portions which extend substantially parallel to the axis of the hub, with a further wall portion of the compartment which closes the operatively forward end of the compartment, such that water enters the water flow passage formed by the compartment via the inlet opening, and the water exits the water flow passage at a rear open end thereof and out of the open rear end of the hub.

10. The blade component as claimed in claim 9, wherein a portion of the closed forward end wall portion of the compartment is angled, curved or kinked, and the result of the angle, curve or kink is that one of the two side wall portions is longer than the other, and wherein the water and objects of mass enter the water flow passage through the inlet opening and are forced against the angled, curved or kinked wall, and the water and objects of mass are propelled outward from the water flow passage as a result of the centrifugal forces generated by the rotating propeller, which generates a secondary form of thrust in forward motion.

11. The blade component as claimed in claim 10, wherein the longer of the two side wall portions is located along the leading edge side of the blade component, and the inlet opening is located against the longer of the two wall portions.

12. The blade component as claimed in claim 8, wherein the compartment is configured on the base or hub in such a way that when the base is attached to the hub, the exhaust gas flow passage comprises a single passage at the operatively forward end region thereof and splits into two narrower passages thereafter, the narrower passages located on either side of the compartment, as a result of the positioning of the compartment within the open ended passage, and as a result the exhaust gasses are compressed as they flow through the split exhaust gas flow passages and expelled out and away from the propeller which results in an additional form of thrust being generated.

13. The blade component as claimed in claim 1, wherein the inlet opening is a generally tear-drop shaped vent, and a side of the vent is tapered to increase the flow of the water and objects of mass drawn into the compartment, wherein the width of the operatively forward end of the vent is greater than the width of the operatively rear end of the vent.

14. A modular propeller comprising a plurality of propeller blade components as claimed in claim 1, the blade components being attachable to the hub as claimed in claim 3 to form the propeller.

15. A single unit propeller comprising a plurality of the propeller blade components as claimed in claim 1 which are integral to a propeller hub.

Drawing