Marine ducted propeller jet propulsion system

Abstract

To provide a jet propulsion unit for a vessel including a diffuser / confusor, a steering control nozzle assembly, and a radius.SOLUTION: A radius is introduced at a transition point between a diffuser / confusor and a steering control nozzle assembly, with this the diffuser / confusor is capable of controlling a shape of water flow flowing out from a propulsion unit, as well as controlling corresponding acceleration over a large pressure differential presented by a wide range of vessel speeds, maneuvers and sea conditions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 61 / 799,274, filed March 15, 2013, entitled "MARINE DUCTED PROPELLER JET PROPULSION SYSTEM," which is incorporated herein by reference.

[0002] The present disclosure relates to exemplary embodiments of marine ducted propeller jet propulsion devices, and more particularly to exemplary embodiments of impeller assemblies and duct designs for marine ducted propeller jet propulsion units. [Background technology]

[0003] The use of jet propulsion systems in marine vessels is well known. Although jet propulsion energy consumption is far less efficient than conventional propeller systems, jet propulsion offers many advantages over simple propellers, particularly in shallow water and from the standpoint of maneuverability. However, widespread acceptance of jet propulsion for marine vessels has not occurred due to certain common problems associated with marine jet propulsion. For example, marine jet propulsion presents significant design challenges, including unstable performance over a wide range of speeds, water depths, and sea conditions, as well as excessive water intake at the jet propulsion unit inlet, which can cause balling.

[0004] Cavitation is another common problem. Cavitation represents an uneven pressure load (effective suction head) on the impeller. Cavitation can be caused by excessive radial acceleration of the fluid, excessive swirl and turbulence in the fluid column, and pressure changes that cause unintended partial vaporization of the fluid throughput due to the vacuum created by the impeller action. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 5,123,867 [Patent Document 2] U.S. Patent No. 6,027,383 Summary of the Invention [Problem to be solved by the invention]

[0006] It would therefore be desirable to design a marine jet propulsion unit whose features work synergistically together to provide a constant water column even at high power outputs and whose water throughput is neither turbulent nor vortex-free to eliminate cavitation and pressure change effects. Furthermore, the unit should have maximum flexibility to handle the entire range of vessel speeds and the variable loads placed on its prime mover unit without causing the aforementioned bowling and cavitation effects. [Means for solving the problem]

[0007] A marine jet propulsion unit comprising a diffuser / confuser, a steering control nozzle assembly, and a radius introduced at the transition point between the diffuser / confuser and the steering control nozzle assembly to enable the diffuser / confuser to control the shape of the water flow exiting the propulsion unit and the corresponding acceleration over large pressure differentials presented by a wide range of vessel speeds, maneuvers, and sea conditions.

[0008] These and other objects of the present disclosure will become apparent from a consideration of the following detailed description taken in conjunction with the accompanying drawings and claims, in which like reference numerals refer to like parts throughout. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an illustration of a marine ducted propeller jet propulsion device according to an exemplary embodiment of the present disclosure. [Figure 2]2 is an exploded view of the marine duct propeller jet propulsion device according to the exemplary embodiment of FIG. 1. [Figure 3] 2 is an exploded view of the marine duct propeller jet propulsion device according to the exemplary embodiment of FIG. 1. [Figure 4] 2 is an exploded view of the marine duct propeller jet propulsion device according to the exemplary embodiment of FIG. 1. [Figure 5] 2 is an illustration of an impeller and diffuser for a marine ducted propeller jet propulsion device according to the exemplary embodiment of FIG. 1; [Figure 6] 1 is an illustration of an impeller hub and diffuser hub for a marine ducted propeller jet propulsion device according to an exemplary embodiment of the present disclosure. [Figure 7] 1A-1D are various views of an impeller for a marine ducted propeller jet propulsion device according to an exemplary embodiment of the present disclosure. [Figure 8] 1A-1D are various views of a diffuser / confuser for a marine ducted propeller jet propulsion device according to an exemplary embodiment of the present disclosure. [Figure 9] 1 is an illustration of a marine ducted propeller jet propulsion device according to an exemplary embodiment of the present disclosure. [Figure 10] 1A-1D are various views of a trim for a marine ducted propeller jet propulsion device according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components, or portions of the illustrated embodiments. Moreover, while the subject disclosure will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments. It is intended that changes and modifications can be made to the described embodiments without departing from the true scope and spirit of the subject disclosure.

[0011] Exemplary embodiments of the disclosed method and system will now be described with reference to the drawings, in which: US Pat. Nos. 5,629,999 and 5,729,999 also describe conventional jet propulsion units, and both are incorporated by reference.

[0012] The present disclosure provides a propulsion system that substantially improves propulsion efficiency. This efficiency is achieved by (1) converging the passing water mass based on the volume as presented by the fluid flow through the nozzle and (2) volumetrically containing the mass of the system's internal features in the flow rate, thereby improving the focusing characteristics imparted to the flow by the housing. In use, the axial flow cross-sectional area decreases substantially and regularly from inlet to outlet without the resistance of the mass of the internal features presenting a restriction or obstruction to the flow. Additionally, the use of the volumetric nozzle design in the present disclosure reduces turbulence and more efficiently improves the solid plug flow or continuum characteristics of the water flow.

[0013] 1. FIG. 1 illustrates a diagram of a marine ducted propeller jet propulsion system 100 with an enclosed exhaust housing 1. The heat of the engine exhaust can heat the diffuser and steering nozzle assembly housing, which can heat the inner walls of the flow control housing and consequently improve the viscosity coefficient. This can impart heat to the water, reducing the surface drag coefficient of the housing material and increasing the flow viscosity. The benefit of the exhaust around the nozzle outlet is that it provides a pocket of exhaust for the water column it lies within, reducing drag losses of the water column as it strikes the continuous water and improving the counter effect of potential energy within the water column on kinetic energy or thrust.

[0014] 1 and 4, propulsion system 10 functions similarly to an axial flow, positive head, or turbine pump and includes an intake section 100 extending between lines AA and BB, an impeller section 200 extending between lines BB and CC, and a discharge section 400 extending between lines CC and EE. A column of water induced in inlet passage 102 by atmospheric pressure is forced and accelerated through discharge section 400 to provide thrust for vessel 12.

[0015] The watercraft 12 has a ducted propeller jet propulsion system 10 mounted in the aft section 14 such that the intake section 100 of the propulsion system 10 is integrated into the bottom hull 18 using an adapter plate 16 and discharge section 400 of the propulsion system 10, is supported by a transom 20, and extends to the rear of the boat 12 in place of a conventional propeller. The propulsion system 10 is shown schematically in two of its thrust positions: F—forward thrust position and R—reverse thrust position. The prime mover 22 is attached directly to the impeller shaft 24, and the steering linkage 26 is attached to the steering module 28 of the propulsion unit 10.

[0016] The replaceable thrust bearing assembly 30 also provides for the thrust bearing to be repositioned whether the vessel 12 is in or out of the water by disconnecting the drive coupling located on the end of the drive shaft and removing the locking bolts, which then allows replacement of the shaft thrust bearing assembly 30. The thrust bearing assembly 30 is designed to be self-lubricating to ensure that the bearings and seals are always lubricated.

[0017] As shown in Figures 2 and 3, intake section 100 defines, among other things, an intake passage 102 within housing 104, thereby providing communication between intake opening 106 formed in the bottom surface of the hull at one end and impeller intake 203 and impeller section 200 at the other end. Passage 110 is initially rectangular or elliptical in shape but transitions to a circular shape in a manner that controls flow convergence onto the face of impeller 202 and improves flow characteristics. As shown in Figure 2, passage 110 may include two vertical walls 112, a long sloped wall 114, and a short sloped wall 116 that converges into a cylindrical chamber 118 at bend 120. Following bend 120, passage 122 is cylindrical. The converging walls of passage 122 are preferably smooth and rounded at the intersection to facilitate turbulence-free flow. Typically, the angle of the bend 120 varies from about 30 degrees to about 45 degrees depending on specific design requirements, but is not limited to this, and can be adjusted to accommodate the volumetric mass of the internal mechanical components of the impeller intake 203.

[0018] 2, the impeller intake 203 can include a shaft 204, guide vanes 206, and directional vanes 208 while maintaining a Reynolds number (Re) in the range of 2300 to 4000, but typically closer to 2300. The cross-sectional area of ​​the intake 203 is preferably proportional to the cross-sectional area at the inlet 102 to the impeller 202 in a ratio varying from about 1.5 to about 2.5:1, and can be adjusted to include the volumetric insertion in the mass flow of the drive shaft 204, straightening vanes 206, and directional or pre-swirl vanes 208 by increasing the external dimensions accordingly.

[0019] The internal flow characteristics of the upper and lower intakes, 110 and 203, can accommodate the intake grille 210, shaft 204, guide vanes 206, and directional or anti-preswirl vanes 208 by cross-sectionally adjusting the shape of the intake transition from the intake inlet to the impeller face to ensure that the converging flow through the intake 203 to the impeller 202 is unrestricted. Failure to do so can create flow restriction, which can induce pressure changes in the flow to the impeller 202 (shown in more detail in FIG. 4), which can induce aeration in the flow, pressure changes, and cavitation.

[0020] A straight pipe section 211 of minimum length equal to 20% of the impeller blade width is located along the intake wall of the inlet housing 104 forward of the impeller 202 and is adjusted to accommodate the volumetric mass of the internal mechanisms within those parameters, where one or more straightening vanes 208 are used to induce continuous flow to the face of the impeller 202. Other directional vanes 206 are spaced radially along the side of the inlet housing 104 so that an equal volume of water can be induced to flow through the straightening vanes 208 to the periphery of the impeller 202. The vanes 208 minimize radial load on the impeller 202 for optimized fluid flow efficiency, resulting in continuous presentation of the fluid to the face of the impeller 202. The vanes 208 also act to damp any pre-swirl or turbulence in the inlet water column to the impeller 202. It is important that cross-sectional adjustments to the shape of the intake transition from intake 203 to the impeller face ensure that the internal flow characteristics of intake 203 accommodate the volumetric intrusion of the straightening and directional vanes 206, 208 and that the flow through the intake to the impeller 202 is not volumetrically restricted or inhibited. Failure to do so can create flow restriction, which can induce pressure changes in the flow to the impeller 202, which can induce pressure changes as well as aeration in the flow and cavitation.

[0021] An intake grille 210 is positioned within the passage 102 adjacent to the hull opening. The mass of the grille 210 is volumetrically displaced in the intake passage 102 so as not to cause restriction to the incoming flow. Without this, the flow would experience a low pressure drop on the intake side of the grille 210, causing turbulence or reduced-pressure aerated liquid to be presented to the face of the impeller 202. This could induce cavitation along its span from the face of the impeller. The grille 210 is typically a span of parallel bars positioned along the length of the hull 18 and angled below and aft of the rear of the intake housing 104. The bars of the grille 210 have a streamlined or hydrofoil cross-section in the direction of the incoming stream, creating minimal resistance to the water flow. The spacing between the bars of the grille 210 should preferably not exceed the spacing between the diffuser vanes, so that the largest object entering the impeller 202 passes through the diffuser vanes.

[0022] The induction plate of the intake system 100 can be adjusted by design to accommodate differences in hull deadrise, ensuring a smooth continuous entry of water into the intake 110 at the proper angle and flow rate to maximize the continuous flow input velocity to the impeller 202. This component also functions in conjunction with the intake pressure relief bypass valve by creating a backup pressure behind the intake, ensuring that the pressure rise ahead of the impeller 202 does not exceed its designed needs or induce drag under the hull. This relief pressure has been determined through testing to be in the range of 3-6 psi.

[0023] The variably sized intake section 203 can be provided in different sizes to allow installation of the propulsion system 10 to suit any type of vessel, regardless of its hull shape, size, deadrise, or speed, and is connected to the upper intake section 205 by means of a coupling or bolt assembly. The inlet section 200 is installed in the aft section of the hull such that the forward motion of the vessel and subsequent rise from the water surface allows the intake section 200 to be positioned slightly below the water level of the hull when the vessel is in motion. However, for proper operation at rest or at low speeds, the unit 10 should be installed so that at least about 60-80 percent of the cross-sectional area of ​​the impeller 202 is submerged. The intake section 203 is bolted to the hull by means of a flange, for example.

[0024] An armhole duct 216 is provided to allow quick access to the passageway 212 in the event of fouling inside the housing 104. The duct 216 is located at the bend 120 and includes a cylindrical housing 220 with an outer flange 222 and a plug 224. The plug 224 includes a solid section 226 secured to a flange cover 228 that completely fills the duct housing 220. The section 226 includes a smooth, contoured surface that aligns with the surface section removed from the upper intake housing 104 at the bend 120 when the duct 216 is installed. When properly plugged in place, the duct 216 does not cause any flow disturbances. The flange 222 includes a straight, threaded bolt 230 that is inserted into a bolt hole in the flange 222 to ensure proper alignment of the plug 226 during installation. A handle 232 attached to the cover 228 provides additional alignment indicia. A sensor can be positioned between flange 222 and duct 216 to initiate an engine shutdown mode if there is an attempt to remove plug 224 while prime mover 22 is running.

[0025] A bypass valve assembly (not shown) can also be mounted on the housing 104 near the inlet 203 shown in FIGS. 1 and 2. If the water pressure between the hull of the vessel 12 and the induction inlet 106 exceeds its handling capacity by more than 3-6 psi, excess water is released through the bypass valve assembly (not shown). Excessive water buildup, colloquially known as balling, is a common occurrence in watercraft propulsion units. Occurring at high speeds when the vessel is undergoing rapid maneuvering and / or during rough sea conditions, excessive balling creates drag on the hull of the vessel 12 and affects the propulsive efficiency of the unit 10. The valve assembly (not shown) functions as a balling prevention device, releasing pressure. It is known that this pressure should not exceed 3-6 psi. The intake pressure relief bypass valve 232 can work in conjunction with the induction plate by allowing excess pressure buildup ahead of the impeller 202 to be released around the impeller into the exhaust heat exchanger 207. The pressure bypass valve (not shown) can be set to the desired pressure relief deemed necessary according to sea conditions or vessel loads to improve unit performance. This is automatically controlled by a pressure sensor mounted on the side of the housing 104 that relays the operating pressure ahead of the impeller 202, allowing the valve to be adjusted by a programmable controller (not shown). Lack of pressure relief capability can lead to the concomitant rise in pressure ahead of the impeller 202 and at the intake, creating a drag effect at the intake inlet and further affecting the host vessel's performance. The flow released from the bypass valve (not shown) flows into the propulsion system exhaust housing 207.

[0026] 1 and 3 from line BB to line CC, impeller section 200 of the present invention is shown incorporating single stage impeller 202. Impeller assembly 200 includes removable housing 236 comprised of two smaller sections, impeller housing 251, and diffuser / confuser housing 242 having impeller 202 and diffuser / confuser 242. Impeller housing 251 is cylindrical with a generally uniform diameter at inlet port 344 and discharge port 346. Diffuser housing 242 is cylindrical with an inner surface that tapers inward from a maximum diameter adjacent impeller section 200 to a minimum diameter adjacent discharge section 400. The converging inner surface of the impeller housing 240 preferably has an outlet cross-sectional area proportional to the impeller section intake cross-sectional area in a ratio varying from about 0.5 to 0.75:1, adjusted to accommodate the volumetric mass of the internal workings of the impeller 202, namely the blades 250 and hub 252. The preferred ratio is about 0.60 to about 0.70:1, adjusted to accommodate the volumetric mass of the internal workings of the impeller, namely the blades and hub, and is optimally about 0.64:1, so that the displacement of the diffuser / confuser housing 240 is less than the displacement of the impeller section 200. The displacement of the diffuser section is adjusted to accommodate the volumetric mass of the impeller's internal workings, i.e., the blades and hub, from about 75 to about 90 percent, preferably about 80 to about 90 percent, and optimally about 85 percent, of the impeller section's displacement. Furthermore, the annular flow path provided by the axial impeller / diffuser / confuser hub combination in the impeller housing has smooth, substantially continuous inner and outer surfaces to prevent turbulent boundary vortices. An important design criterion for the impeller section 200 is that the cross-sectional areas of the impeller housing 251 and the diffuser housing 240 must be the same at their junctions.

[0027] With particular regard to the individual components of the impeller section 200, the impeller assembly 202 has a unique design that has undergone much testing and modification, both in terms of the shape of the hub portion 252 and the impeller blades 250. The replaceable blade assembly impeller allows for easy replacement of individual impeller blades 250 on the impeller 202 in the event of damage or to change the pitch of the impeller 202 for a different application. An essential aspect of the impeller 202 is that the impeller blades 250 are secured along an outwardly tapering convex surface of the removable hub portion 252, rather than a flat section as is typical in prior art impeller designs.

[0028] The assembled impeller hub 252 preferably has an outwardly tapered convex surface and an annular interior. More preferably, the hub 252 has an outer surface and an annular interior that include concave and convex portions when viewed in axial cross section. The assembled hub 252 has an outer surface with a narrow diameter tip, an increasing variable diameter middle portion, and a larger diameter aft end. The distal end of the shaft 204 extends the length of the hub 252 through a concentric axial bore 266. The tip has an annular end face that abuts a shoulder 264 on the shaft 204 to present a smooth, continuous surface for fluid flow. The annular wall of the assembled hub 252 is of substantially constant thickness, except for the distal annular end that extends outward from the bore 266 to provide an engageable surface vane section retainer, and except for the locking sheath.

[0029] Impeller 202 has blades 250 mounted along the contoured surface of hub 252 at an incline designed to maximize the exposure of the blades to the passing fluid and reduce the radial acceleration component imposed by impeller 202. Blade 250 has a convex outer radius 272, a concave inner radius 274, a short trailing edge, a long leading edge, a midpoint, and a wide surface side with a thickness.

[0030] The inclination of the impeller blade 250 is defined as the average inclination or degree of twist in the length of the blade 50 as determined from vertical with respect to a line tangent to the outer surface of the assembled hub 252 at the leading edge and at the trailing edge. When looking along either the inner radius 274 or the outer radius 272 or down either the leading or trailing edge, the average inclination angle of both the leading and trailing edges is preferably in the range of about 20 to 40 degrees from vertical, more preferably about 30 degrees from vertical, with one edge inclined opposite the other edge as required by the blade 250 to follow the hub 252 surface contour. The leading edge is twisted in the direction of forward movement of the impeller 202. It will be understood that the leading edge corresponds to the tip of the hub 252, which has a narrow diameter, and the trailing edge corresponds to the aft end of the hub 252, and that the mid-portion radial width of the blade 250 is a function of the mid-portion radius of the hub 252, such that the impeller diameter is substantially constant. The total length of the blades 250 is equal to the length of the assembled hub 252 plus an angular component.

[0031] Radially, the thickness 284 of the vane 250 is not substantially uniform as defined above, but rather a low-profile foil design as a result of improved design. The leading edge has a substantially uniform tapering, with a maximum thickness at a midpoint approximately equidistant from either edge. The leading edge entrance angle should be between 13 and 15 degrees, relative to the rotational speed of the impeller 202.

[0032] 7 shows a typical fan with five blades extending along an assembled hub 252. The number of blades, impeller diameter, and degree of pitch can be optimized in relation to the power supplied by prime mover 22 and the required design considerations of the vessel at hand.

[0033] The internal flow characteristics of the impeller housing 251 can be sized by the shape of the impeller housing 251 and the impeller hub 252 to accommodate the displacement of the impeller vanes 250 and hub 252 by cross section, thereby allowing the flow to transition unrestricted from the intake 203 through the impeller 202 to the diffuser / confuser 242 and maintaining the proper flow velocity to the steering nozzle 400. Failure to do so can cause changes in the flow characteristics through the system, resulting in cavitation at the leading edges of the impeller vanes or inducing pressure changes in the flow to the diffuser / confuser and into the steering nozzle assembly 400, which can induce turbulence or flow choke and resultant back pressure, reducing efficiency and ultimately creating a hydraulic damping effect.

[0034] By adding a continuous straight section to the end of the assembly impeller hub 252 and to the blade width representing a continuation of the existing pitch of the blades 250, the pitch effect of the impeller blades 250 on the accelerated flow can be improved by the extension of the span beyond the required pitch length. The design pitch of the impeller blades 250 can be a combined interpretation of the required outlet velocity efficiency and the power available from the power source driving the impeller 202. This power source can be any drive type, whether electric, gasoline, diesel, gas, or alternative fuel powered. The effect of the added span can work in conjunction with interchangeable diffuser blade components to improve the transition of the rotational outlet flow velocity behind the impeller blades 250 to a linear, laminar style flow through the diffuser 242 and onto the steering nozzle assembly 400. Similar to the ability to match a conventional propeller to the needs of a vessel, adjusting the diameter-to-pitch ratio allows for the adjustment of the additional span extension to improve the performance and efficiency of the impeller output to the drive. The internal flow characteristics of the impeller housing 251 can be adjusted by cross section to accommodate the displacement of the impeller vanes 250 and additional pitch extensions by adjusting the impeller housing diameter or by adjusting the impeller hub displacement at flow rate. This allows the flow transition from the intake through the impeller 202 to the diffuser 242 to be unrestricted and maintains the proper flow and velocity through the diffuser / confuser 242 onto the steering nozzle 400. Failure to do so can create changes in the flow characteristics through the system, resulting in a commensurate reduction in propulsive efficiency and ultimately, rapidly, system failure.

[0035] A durable plastic removable and replaceable impeller wear sleeve 260 can be provided to stop wear and tear on the impeller housing 251. The clearance dimension between the blade tips and the interior wall of the removable and replaceable impeller wear sleeve is critical and must be neither more nor less than touch contact.

[0036] The internal flow characteristics of the diffuser / confuser housing 242 can be adjusted by adjusting the shape of the diffuser / confuser housing 242 to accommodate the displacement of the diffuser 242 and hub 243 vanes by cross section. This allows unrestricted flow transition from the back of the impeller vanes 250 through the diffuser 242 to the top nozzle of the nozzle assembly 400 and maintain proper flow rate and velocity to the top steering nozzle 401. Failure to do so can create changes in the flow characteristics through the system, resulting in turbulence or flow choke and resulting back pressure. This can lead to cavitation at the leading edge of the impeller vanes 250, which can induce rapid pressure changes in the flow to the diffuser and onto the steering nozzle assembly 401, resulting in reduced efficiency and eventual system failure.

[0037] The replaceable diffuser / confuser vane component 245 allows for changes to the leading edge vanes for the diffuser 242, replacing them if damaged, or changing the pitch of the leading edges of the diffuser vanes 244a if they need to be adjusted to meet the trailing edge speed needs of the impeller 202 or require a change in the pitch of the impeller blades 250.

[0038] The radius of the diffuser vanes 244 from their leading edges to their straight trailing edge sections may be larger than in previous designs to ensure a reduced turbulent transition of the flow from the impeller vanes 250, allowing for a less aggressive reduction in turbulence as the flow changes from rotational to linear / laminar style. The angle of entry of the diffuser / confuser vanes 244 should correspond to the trailing edge flow velocity at the trailing edge of the impeller 202. The leading edge radius of each vane may extend approximately halfway along the length of the diffuser / confuser vane. The change in radius and resulting change in vane shape can be incorporated into the internal flow characteristics of the diffuser / confuser housing and / or the volumetric flow characteristics of the hub supporting the diffuser vanes 244, for a more rigorous convergent flow effect on the ensuing flow characteristics than previously achievable.

[0039] The exit radius 246 for the diffuser / confuser 242 can be adjusted to increase. The sharp transition from the diffuser / confuser exit to the steering nozzle assembly 400 can cause flow turbulence as the flow transitions from the diffuser / confuser 242 to the steering control nozzle assembly 400. This abrupt and sudden change in angle induces flow turbulence at higher flow velocities at the diffuser exit that restricts the flow and creates backpressure, as shown in U.S. Patent Nos. 5,629,997 and 5,729,997, which can affect the efficiency of the impeller 202 by creating resistance to flow away from the back surface of the impeller blades 250. Increasing this radius provides for a reduction in flow acceleration proportional to the constant velocity acceleration applied to the flow by the powered impeller 202 and the convergent flow characteristics provided by the design. The flow needs to be controlled through abrupt flow accelerations without becoming turbulent in nature, which creates turbulence and thus induces backpressure. It was found that by introducing a radius at the transition point from the diffuser / confuser 242 to the steering control nozzle assembly 401, the reduction in turbulence was reduced sharply and commensurately with the increase in radial length of the radius provided at the contact point between the diffuser / confuser 242 and the steering control nozzle assembly 400.

[0040] Diffuser / confuser 242 is disposed immediately adjacent to impeller 202 and is designed to function in conjunction with impeller 202 to accomplish several important performance functions: (1) attenuate the radial acceleration component imparted by impeller 202, (2) diffuse the path of water throughput across the entire impeller area cross-section, (3) provide a low artificial back pressure on impeller 202 to prevent partial vaporization of the passing fluid due to the vacuum associated with impeller action, and (4) enable maximum reaction of impeller 202 and allow more efficient conversion of available energy to potential energy by prime mover 22. Any degree of steam present would introduce uneven loading and cavitation on impeller 202. These performance functions are improved by the volumetric flow characteristics of diffuser / confuser 242 being adjusted to accommodate the volumetric mass of its internal working components.

[0041] The diffuser / confuser hub 243 preferably has an inwardly tapered convex surface and an annular interior, disposed opposite the hub impeller 252. The hub 243 has a flat, large-diameter leading end, a reduced, variable-diameter midsection, and a smaller-diameter trailing end, forming a rounded nose with a concentric bore cavity 246 drilled through its center and a central annular end extension. The concentric outer annular cavity 246 is primarily intended for excess weight reduction, providing the hub 252b with a substantially constant-thickness wall. The concentric inner annular bore 246 defines a cylindrical housing for a support bearing for the impeller shaft 204, which supports the impeller 202. The bore 246 has a reduced diameter in the nose section of the hub 243 as required by design strength criteria.

[0042] The diffuser / confuser vane design is typically based on a standard straight vane design, with the exception of a significant modification incorporated into the vanes 244 due to the surface contour of the diffuser hub 252b. The vanes 244 have a radial width that is a function of the diameter of the hub 243, so that the diffuser 242 has a constant diameter. The thickness of each vane 244 may be airfoil-shaped, or may typically have a uniform thickness throughout, except for the edge sides, which may be blunt or pointed as design refinements require. The vanes 244 have replaceable leading edge ports in replaceable sections 245 that curve in a direction opposite the directional advance of the impeller 202, and straight sections that are typically perpendicular to the hub surface, but may also be angled away from the orthogonal plane that bisects the hub 243 at the junction and opposite the directional advance of the impeller 202 by up to about 10 degrees depending on performance refinements. The curved ends of the removable diffuser / confuser vane section are typically angled at an angle of about 10 to about 40 degrees away from a longitudinal plane that bisects the hub 243 of the replaceable vane section and incorporates the straight sections. The vanes 244 are rigidly attached longitudinally at one end to the contoured surface of the hub 243 and at the other end to the inner wall of the housing, providing girding support for the bearing function of the hub 243. The number of diffuser / confuser vanes 244 is selected relative to the number of impeller vanes 250 in relation to the performance criteria of the diffuser / confuser section, such as providing back pressure and damping of radial acceleration, and minimizing resonance and noise levels. An important design feature is an odd:even impeller vane to diffuser / confuser vane ratio, or vice versa. For example, given 3, 5, or 7 impeller blades, the corresponding number of diffuser vanes would preferably be 6, 8, or 10.

[0043] Overall, the diffuser / confuser 242 is designed to control the shape and corresponding acceleration of the water flow over a wide range of vessel speeds, maneuvers, and large pressure differentials presented by sea conditions.

[0044] The impeller assembly 200 is axially symmetrically disposed within a cylindrical impeller housing 251, with the diffuser / confuser device 242 mounted adjacently aft of the impeller device 202. The outer surface of the aft end on the rotatable hub 252 is substantially continuous with the outer surface of the tip end on the fixed hub 243. The impeller assembly 200 is configured to make this assembly simple and quick and to allow for mating of the impeller 202 and matching diffuser 242 according to the prime mover 22 and vessel design requirements. The impeller housing 251 may have an interchangeable sleeve that allows the housing diameter to be reduced corresponding to the reduction in impeller diameter. Thus, a smaller diameter impeller arrangement can be used for smaller boats. However, there is no limit with respect to horsepower or vessel size, and the propulsion system 10 may have a commensurately expanded capacity for larger vessels or for higher speeds.

[0045] An impeller shaft 204 extending axially through the propulsion system 10 has a first bearing support by an interchangeable bearing assembly 30 mounted on the inlet housing 203 and a second bearing support 247 at a fixed hub 243. The bearing assembly 30 includes a housing, roller bearings, and a locking ring. The bearing assembly 30 may also include a gear housing (not shown) for unit gearing according to the particular prime mover requirements.

[0046] The shaft 204 has a concentric distal section with a shoulder and a concentrically reduced diameter section. The impeller 202 slides onto the section of the shaft 204 so that the annular end of its leading edge on the hub 252 abuts the shoulder to present a smooth, continuous surface for fluid flow. An annular locking sleeve, having a proximal annular end with a diameter larger than the minimum diameter of the distal annular end extending outward from the hub bore 266, engages the annular end to securely hold the impeller 202 against the shoulder on the shaft 204. A washer and locking nut secure the sleeve in place. The distal section of the shaft 204 is threaded for a locking nut so that a standard key (not shown) and keyway combination synchronously engages the impeller 202 on the shaft 204.

[0047] The bearing sleeve is inserted into the central annulus of the hub housing 252. The assembly is completed by inserting the shaft portion with the sleeve through the bearing so that there is approximately 1 / 8 inch clearance between the hubs 252 and 243. A bore 266 in the nose end of the fixed hub 243 provides an outlet for water to wash around the exterior of the bearing. The bearing is self-lubricating, self-cooling, and self-cleaning, which is typical of bearings used in marine applications.

[0048] An alternative bearing application for large ships is to set the bearings within directional vanes and position the impeller on a counter-lever section of a shaft that extends beyond the bearing housing located on a directional support.

[0049] The shaft can also be housed in a foil-shaped shaft housing to provide minimal resistance to the intake flow supported by directional vanes in front of the impeller forming a support structure. The mass of the housing designed into the intake flow characteristics can provide less resistance to the intake flow than a bare shaft as it stops the effect of the shaft rotational speed pre-swirling the flow against the face of the impeller.

[0050] The means for joining the impeller section casing to the intake housing 104 and the upper nozzle housing 401 to the discharge housing nozzle 402 include identical ring clamps or bolt flanges fastened by bolts in clamps that fit over mating flanges secured to the respective sections. The clamps typically include two semicircular grooved pieces attached at a hinge. Additional joining means include mating flange connectors, such as between the impeller housing 251 and the diffuser housing 242, which utilize a flange and a diffuser casing, and the discharge casing, which utilize a flange. Preferably, rubber seals, gaskets, or O-rings are used in between. The propulsion system 10 is designed so that the steering means 28 with its housing is located at the center and top of the pump housing section. The housing sections are also joined by flanges.

[0051] The outlet or discharge section 400, extending from line C--C to line E--E, comprises three cylindrical sections and serves two basic functions: a means for oscillatingly directing the outflow flow to provide fluid acceleration and control. The discharge section 400 preferably incorporates a 60 degree complement angle so that the discharge point is horizontally aligned with the hull bottom of the vessel 12.

[0052] The first section extending from line CC to the middle is an inclined cylindrical housing 291. Housing 400 has a swingable portion 293 that can swing horizontally up to 360 degrees. The swingable second section 293 and the inclined section are joined by a bearing assembly. The bearing assembly includes an inner race attached to the exterior surface of housing 291, an outer race attached to the exterior surface of the section, and a bearing ring between the two races.

[0053] The steering gear 28 connects the steering column in the vessel to the rotatable section of the jet propulsion unit of the present invention. The steering linkage includes a steering rod with a sleeve bearing and first and second universal joints. The second universal joint, attached to the top of the steering rod that extends at an angle through the interior of the housing 291, operates in conjunction with the rotating section through spoke vanes. The angle spoke vanes are designed and installed so as not to obstruct the flow.

[0054] The third discharge section 400 is a complementary angled housing clamped to the previous sections and extending to line E--E. The housing 291 contains a lower nozzle 402 and is designed to be interchangeable to allow performance-guided selection of nozzles. The cross-sectional area of ​​the steering assembly 291 within the discharge section 400 is preferably proportional to the impeller inlet cross-sectional area by a ratio of about 0.25 to about 0.50:1. The interior surface of the discharge nozzle is smooth and throttled to the outlet cross-sectional area by adjusting the entry diameter of the steering assembly 291 by a ratio of preferably about 0.30 to about 0.40:1, optimally about 0.35:1, to accommodate the volumetric mass of the steering shaft, spoke vanes, and internal workings of the flow control vanes in the flow stream.

[0055] The bottom nozzle 402 includes one or more straightening vanes, preferably affixed perpendicularly to the inner surface of the section. The straightening vanes are designed to dampen swirl and allow a steady laminar column of water throughput to exit the unit 10. In addition, the nozzle 402 includes a ring attached to the outer edge of the nozzle. The ring artificially enhances the propulsive response of the water being discharged through the nozzle 401 by creating a vortex around the edge of the ring, allowing for a smoother transition of the outflowing water.

[0056] The internal flow characteristics of the top steering nozzle 401 can be adjusted by adjusting its shape to accommodate the steering shaft 501 displacement by cross section. This allows the flow transition from the back of the diffuser vane 244 through the top nozzle 401 of the nozzle assembly to the bottom nozzle 402 without restriction and maintains proper flow rate and velocity to the steering nozzle. Failure to do so can cause changes in flow characteristics through the system, resulting in turbulence with resulting back pressure. This induces sudden pressure changes in the flow to the steering nozzle, resulting in turbulence and back pressure that affect the efficiency of the diffuser 242, reducing overall system efficiency and ultimately causing system failure. It was discovered that increasing the radius of the top nozzle 401 reduces flow resistance and interacts with the modified diffuser / confuser exit radius, improving the efficiency of the flow through the top nozzle 401. The increase in efficiency is directly related to the radial length of the elbow shape of the top nozzle 401 and the improved internal flow velocity achieved with the increased radial length.

[0057] The internal flow characteristics of the steering nozzle steering bearing assembly 291 can be adjusted by adjusting the geometry of the steering bearing assembly to accommodate the steering shaft 501 and spider arm displacement by cross section. This allows the flow to proceed unrestricted from the nozzle assembly's top nozzle 401, through the bearing assembly, to the bottom nozzle 402, and maintain proper flow and velocity to the steering nozzle. Failure to do so can cause changes in the flow characteristics through the system, resulting in turbulence with resulting back pressure. This can induce sudden pressure changes in the flow to the steering nozzle, resulting in turbulence, back pressure, and reduced efficiency.

[0058] The internal flow characteristics of the lower steering nozzle 402 can be adjusted by adjusting the shape of the lower nozzle to accommodate the guide vane displacement by cross section, allowing the flow to transition unrestricted from the bearing assembly to the bottom nozzle exit point and maintaining proper flow rate and velocity through the steering nozzle. Failure to do so can cause changes in the flow characteristics through the system, resulting in reduced efficiency.

[0059] The guide vanes 403 of the lower steering nozzle 402 can be raised above the radius to incorporate the same radius as the nozzle's exterior wall. This can provide a smoother transition to guide the flow outflow through the nozzle radius and reduce turbulence generation at different nozzle radiuses, improving flow through efficiency. The nozzle's internal flow characteristics can accommodate any guide vanes through cross-sectional adjustments to the nozzle shape to ensure unrestricted flow through the nozzle. As with the upper nozzle 401, increasing the radius of the lower steering nozzle 402 reduces flow resistance and improves flow efficiency through the lower nozzle. The increase in efficiency is directly related to the radial length of the elbow shape of the lower nozzle 402 and the internal flow velocity. The interchangeability of the lower steering nozzle 402 allows for adjustment of the existing outflow height by using nozzles of different radial lengths. This results in raising or lowering the outflow exit point, changing the thrust point and its effect on the vessel for changes in the radial length of the lower steering nozzle.

[0060] The jump-up steering vane 405 in the bottom nozzle 402 can assist in tracking and better control of vessels with low deadrise. The jump-up steering vane 405 will retract into the steering nozzle if any underwater obstacle, whether animal or mineral, is encountered. The bottom steering nozzle housing diameter accommodates the volumetric mass of the internal workings of the jump-up steering vane 305 in flow capacity by dimension.

[0061] Discharge housing 400 also includes an air bleed hole drilled approximately in line with the end of diffuser hub 243 to allow trapped air introduced into unit 10 to escape and to allow unit 10 to become self-priming. Flow from the air bleed hole can exit to atmosphere or into exhaust housing 500.

[0062] The control function of the discharge section 400 is incorporated by the direction of nozzle thrust as provided by the steering device 28. Directional heading is associated with the operation of the nozzle at positions F, R and intermediate radial positions.

[0063] A reversing bumper 700 with a rubber protector 701 may be designed to protect the steering nozzle assembly 409 from damage due to ramming from the rear or when the vessel is reversing or as an anchor for towing.

[0064] Hydraulic trim 600, seen in Figures 9 and 10, incorporating hydraulic ballpoint components 601, 602, and 603, can allow for up or down trimming of the vessel while underway without unduly affecting the flow efficiency of the drive. Available trim 600 allows for approximately a 20-degree up or down change in nozzle outlet positioning. The internal flow characteristics of hydraulic trim 600 can be parallel, and the inlet and outlet flow velocities of the trim device can be as equal as possible. Trim 600 can be included with or without an exhaust shroud.

[0065] The marine jet propulsion unit 10 of the present invention is preferably manufactured and assembled from stainless steel selected for its strength and resistance to corrosion characteristics; however, rust-resistant engineering aluminum, or plastics with excellent adhesion, impact, and structural strength would also be suitable for one or more components of the propulsion unit 10.

[0066] It will be appreciated that the performance of the watercraft propulsion system 10 is dependent upon the synergistic interrelationship of the functions of each individual section. Each individual section must be manufactured and assembled in a balanced and symmetrical manner, taking into consideration the required pressure and flow balances needed to enable the jet propulsion unit 10 to function efficiently.

[0067] The predictability of performance relative to the power requirements of the jet propulsion unit 10 allows the unit to be fine-tuned to a particular prime mover adhering to design criteria for the impeller blades, associated diffuser vanes, and nozzle.

[0068] The foregoing description of the invention illustrates and explains it. Various modifications of the materials, devices, and specific components employed will occur to those skilled in the art. It is intended to cover all such modifications within the scope and spirit of the appended claims.

Claims

1. 1. A device for a vessel, comprising: Diffuser / Confuser; a steering control nozzle assembly; an increasing radius introduced at a transition point between the diffuser / confuser and a steering control nozzle assembly, the diffuser / confuser designed to control the shape and corresponding acceleration of water flow over large pressure differentials presented by a wide range of vessel speeds, maneuvers, and sea conditions.

2. It is a hub, 10. The device of claim 1, further comprising a hub including a large flat diameter leading section, a reduced variable diameter intermediate section, a reduced diameter aft end forming a rounded nose with a concentric bore drilled through its center, and a central annular end extension.

3. The apparatus of claim 2 , wherein the diffuser / confuser includes an inwardly tapered convex surface and an annular interior disposed on opposite sides of the hub.

4. a concentric outer annular cavity, 4. The apparatus of claim 3, further comprising a concentric outer annular cavity, the primary purpose of which is to reduce excess weight by providing a substantially constant wall thickness for said hub.

5. further comprising a concentric inner annular bore; 5. The apparatus of claim 4.

6. a diffuser / confuser blade; A diffuser / confuser vane, comprising:

3. The apparatus of claim 2, further comprising a diffuser / confuser vane, said vane having a radial width that is a function of the diameter of said hub such that said diffuser / confuser has a constant diameter.

7. 7. The apparatus of claim 6, wherein the thickness of each vane may be airfoil-shaped and may have a uniform thickness throughout except for its edge portions, which may be either blunt or pointed.

8. 8. The apparatus of claim 7, wherein the vanes include leading edges that curve in a direction opposite to the directional advance of the impeller and straight sections that are typically perpendicular to the hub surface.

9. 9. The apparatus of claim 8, wherein the curved ends of the vanes are angled at an angle of about 10 to about 40 degrees away from a longitudinal plane that bisects the hub and incorporates the straight sections.

10. 10. The apparatus of claim 9, wherein the vane is rigidly attached at one end longitudinally to the contoured surface of the assembled hub.

11. An impeller, an impeller disposed immediately adjacent to the diffuser / confuser; 11. The apparatus of claim 10, further comprising impeller vanes secured along an outwardly tapered convex surface of the hub.

12. The apparatus of claim 11 wherein the number of diffuser / confuser vanes is selected relative to the number of impeller blades.

13. 13. The apparatus of claim 12, wherein the ratio of impeller blades to diffuser / confuser vanes is odd, even, or vice versa.

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