DE69226963T2 - BLAST DRIVE DEVICE FOR SHIPS WITH A SCREW IN A TUNNEL - Google Patents

Description

Field of the invention

The present invention is directed to a jet propulsion device for a propeller-driven vessel in a tunnel and, more particularly, to an impeller assembly and a tunnel structure for a jet propulsion unit for a propeller-driven vessel in a tunnel.

Background of the invention

The use of jet propulsion devices for marine vessels is a well-known technology. Jet propulsion has many advantages over the simple propeller, particularly in terms of maneuverability, and the energy consumption of a jet propulsion is much more efficient. However, widespread acceptance of jet propulsion for marine vessels has not yet occurred due to certain general problems associated with jet propulsion of ships. For example, jet propulsion for ships poses significant implementation problems due to uncertain performance over a wide range of speeds, water depth, sea conditions, etc.

Excess water intake at the inlet of the jet propulsion unit can cause agglomeration, i.e. excess water pressure between the hull and the inlet due to the unit being unable to take in a sufficient volume of water during ship maneuvers or poor sea conditions. Agglomeration creates a high drag characteristic that adversely affects propulsion performance.

Cavitation is another common problem. Cavitation means uneven loading of the impeller. Cavitation can be caused by excessive radial acceleration of the fluid, excessive swirling or turbulence of the fluid column, and unintentional partial vaporization of the fluid flow associated with a vacuum created by impeller action.

Accordingly, it would be desirable to design a jet propulsion unit for marine vessels in which all features work synergistically to ensure a constant water column even at high discharge and in which the water flow is neither turbulent nor swirling to eliminate cavitation effects. Furthermore, the unit should have maximum flexibility to handle the full speed range of the marine vessel and varying loads on the unit without creating the agglomeration and cavitation effects mentioned above.

Finally, the unit should be effective in preventing the inlet of foreign materials, so it should have a quick means of manually cleaning the inlet if contamination occurs.

US Patent 4,449,944, issued to Baker et al., discloses a variable inlet device for a hydrojet boat propulsion system that allows efficient transition from low speed operation to high speed operation of the boat. Installed in the "slot" of a "V" bottomed hull, The drive has an aerodynamically favourable air intake scoop with an injection door or plate that reacts to the imbalance between internal flow pressure and external screw flow pressure.

US Patent 3,543,713 issued to Slade discloses a propulsion unit for a marine vessel which operates by discharging water from a pump through an orifice. The orifice can be oriented according to the desired propulsion direction.

U.S. Patent 3,680,315, issued to Aschauer et al., discloses a hydraulic jet propulsion device for boats having a variable area discharge nozzle.

Australian Patent Application 24907/88 filed on 1 November 1988 and published for public inspection on 11 May 1989 discloses a marine propulsion unit comprising a housing with a variable inlet suction, a first set of blades downstream of the suction, a propeller/impeller, a second set of blades downstream of said propeller and a converging discharge housing downstream of said second set of blades. The use of variable suction through the inlet port is intended to reduce damming during the suction process and consequently cavitation and drag. The marine propulsion unit can be used with both outboard and stern drive power transmissions.

US Patent 3,302,605 granted to Kuether discloses a jet propulsion device for watercraft that has a Control mechanism designed to provide improved maneuverability and a propeller and housing structure designed to operate efficiently and use minimal energy.

US Patent 3,187,708 issued to Fox discloses a jet propulsion unit for boats completely outside the hull, which replaces the gear box propeller and rudder structure of the usual motor boat arrangements.

U.S. Patent 3,993,015 issued to Klepacz et al. discloses a hydraulic propulsion system for watercraft that includes the formation of an open-ended parallel-walled intake tunnel.

Other US patents of interest include 3,889,623 to Arnold; 3,827,390 to De Vault et al.; 3,233,573 to Hamilton; 4,133,284 to Holcroft; 3,868,833 to Noe et al.; 4,652,244 to Drury; 3,192,715 to Engel et al.; 3,598,080 to Shields; 3,620,019 to Munte; 3,842,787 to Giacosa; 3,624,737 to Keller; 4,718,870 to Watts; 4,643,685 to Nishida; 4,600,394 to Dritz; 3,782,320 to Groves Jr.; 3,776, 173 to Horwitz; 3,589,325 to Tattersall; 4,432,736 to Parramore; 3,788,265 to Moore; 4,474,561 to Haglung; and 4,925,408 to Webb at al.

Summary of the invention

According to the present invention, there is provided a jet propulsion unit for a seagoing vessel, comprising:

a converging intake section having convergingly tapered walls for receiving water from the vicinity of the unit, said walls having a smooth surface to inhibit turbulence;

an impeller section for increasing the energy of water from said suction section;

a diffuser section for promoting the axial flow of water from said impeller section;

a pivotable discharge section for discharging water from said diffuser section in the form of a substantially plug-flow directed water jet;

a cylindrical housing disposed in said impeller section having an inner surface of generally uniform diameter;

a rotatable hub concentrically disposed in said cylindrical housing and having an outer surface, viewed in axial cross-section, which has a concave portion and a convex portion and an outer diameter increasing from a minimum near said intake portion to a maximum near said diffuser portion;

a plurality of radially spaced impeller blades secured to said rotatable hub and extending from the outer surface of said hub to extending adjacent the inner surface of said cylindrical housing; said vanes being inclined at an angle with respect to the longitudinal axis of said rotatable hub;

an inner surface disposed in said diffuser section tapering from a maximum diameter proximate said impeller section to a minimum diameter proximate said vent section;

a fixed hub concentrically disposed in said diffuser section and having a convex outer surface tapering from a maximum diameter proximate said impeller section to a distal terminus proximate said vent section, said fixed hub outer surface and said inner surface defining an annulus in said diffuser section having a generally converging cross-sectional area;

a plurality of radially spaced diffuser vanes extending from said outer surface of the fixed hub to said inner surface of the diffuser section, said diffuser vanes having at least a distal portion parallel to a longitudinal axis of said fixed hub proximate said vent section;

a bearing disposed between said rotatable hub and said fixed hub; and

Means for rotating said rotatable hub with respect to the aforementioned fixed hub.

According to a preferred embodiment, the present invention provides a tunnel-mounted propeller jet propulsion unit for placement in the aft portion of a seagoing vessel to be propelled. The unit includes a tunnel having jet flow characteristics on a volumetric basis and an additional impeller assembly enabling the unit to operate without cavitation or bunching over a wide variety of conditions related to speed change, maneuverability and sea conditions. Additional features include an anti-bunching bypass valve for reducing excessive pressure in the intake section and a trim adjustment mechanism.

The jet propulsion unit for marine propellers in a tunnel for a seagoing vessel comprises a converging intake section with convergingly tapered walls for receiving water from the vicinity of the unit; an impeller section for increasing the energy of water from said intake section; and a diffuser section for promoting the axial flow of water from the impeller section. The discharge section is pivotable for discharging water from the diffuser section in the form of a directed jet of water. A cylindrical housing having an inner surface of generally uniform diameter is disposed within the impeller section. A rotatable hub is disposed concentrically within the cylindrical housing and has an outer surface having concave and convex portions and a outside diameter that increases from a minimum outside diameter near the intake section to a maximum outside diameter near the diffuser section. A plurality of radially spaced impeller blades are attached to the rotatable hub and extend from the outer surface of the hub to adjacent the inner surface of the cylindrical housing. The blades are inclined at an angle with respect to a plane containing a longitudinal axis of the rotatable hub. An inner surface disposed in the diffuser section tapers inwardly from a maximum diameter near the impeller section to a minimum diameter near the discharge section. Concentrically disposed in the diffuser section is a fixed hub having an outer surface that tapers inwardly from a maximum diameter near the impeller section to a distal end point near the discharge section. The outer surface of the fixed hub and the inner surface of the diffuser section define an annulus in the diffuser section having a generally converging cross-sectional area. A plurality of radially spaced diffuser vanes extend from the outer surface of the fixed hub to the inner surface of the diffuser section. The diffuser vanes have at least a distal portion that is parallel to a longitudinal axis of the fixed hub proximate the discharge section. A bearing is disposed between the rotatable hub and the fixed hub with means for rotating the rotatable hub relative to the fixed hub.

The intake passage preferably has a transverse inlet cross-sectional area which is in a ratio of approximately 1.5 to about 2.5:1 proportional to an inlet cross-sectional area of the impeller section. An armhole conduit allows ready access to the inlet passage and one or more straightening vanes securely attached along an inner perimeter surface dampen rotation of the incoming flow. The impeller section preferably includes a bypass valve located upstream of the impeller blades to inhibit agglomeration. The cross-section of the impeller section inlet is proportional to the cross-section of the diffuser section outlet in a ratio of about 0.50 to 0.75:1, preferably in a ratio of about 0.60 to 0.70:1 and optimally about 0.64:1.

The discharge section preferably has a variable orifice nozzle that can be rotated 360º by a control mechanism and a trim adjustment that raises and lowers the nozzle to adjust the trim of the vessel. One or more straightening vanes are attached to an inner surface of the nozzle and spoke vanes are used to attach the control mechanism. The cross-section of the discharge section outlet is preferably proportional to a cross-section of the impeller section inlet in a ratio of about 0.25 to about 0.50:1, preferably in a ratio of about 0.30 to about 0.40:1, and optimally about 0.35:1.

The entire system provides low resistance flow, with internal obstructions to the flow being reduced and the converging sections being smooth and gradual.

Short description of the drawings

Fig. 1 is a partially cut-away longitudinal cross-section showing the jet propulsion unit with propeller in a tunnel within the confines of a sea-going vessel in the forward thrust position and in the aft thrust position.

Fig. 2 is an illustrative view of a tunnel-mounted propeller jet propulsion unit of the present invention of Fig. 1 in position in a seagoing vessel.

Fig. 3 is an external angled perspective view of the intake section of the nozzle propulsion unit of the present invention.

Fig. 4 is a front perspective view of the unit of Fig. 3 taken along lines 4-4.

Fig. 5 is a bottom perspective view of the intake section of the jet propulsion unit of Fig. 3 taken along lines 5-5.

Figure 6 is a side perspective view of the pump and drain sections of the nozzle drive unit of the present invention.

Fig. 7 is a rear perspective view of the pump and drain section of the nozzle drive unit in Fig. 6 taken along line 7-7.

Fig. 8 is a perspective cross-sectional view of the nozzle drive unit in Fig. 1 taken along lines 8-8 showing the blade and hub assembly.

Fig. 9 is a perspective cross-sectional view of the nozzle drive unit of Fig. 1 taken along lines 9-9 showing the blade and hub assembly.

Fig. 10 is a fragmentary perspective view taken along lines 10-10 of the unit of Fig. 1 showing the inlet face of an impeller assembly.

Fig. 11 is a fragmentary perspective view taken along lines 11-11 of the unit of Fig. 1 showing the discharge surface of the impeller assembly.

Fig. 12 is an angled perspective view of the impeller assembly.

Fig. 13 is a side perspective view of a diffuser vane assembly.

Fig. 14 is an axial view of the rotatable hub.

Fig. 15 is an axial view of the fixed hub.

Fig. 16 is a view of a dual hub assembly in longitudinal cross section.

Fig. 17 is a side perspective view of the impeller assembly of Fig. 12 showing an impeller blade attached.

Fig. 18 is a side surface perspective view of an impeller blade.

Fig. 19 is a planar perspective view taken along an inner length of the impeller blade.

Fig. 20 is a planar perspective view along an edge of the impeller blade showing a slope in the blade.

Fig. 21 is a planar perspective view along a second edge of the impeller blade showing the inclination in the impeller blade.

Detailed description of the invention

The present invention is based in part on the discovery that substantially increased propulsion power can be obtained by converging the mass of water flowing therethrough on a volumetric basis, as demonstrated by fluid flow through a nozzle. Or, in other words, the axial cross-sectional flow area decreases substantially uniformly from inlet to outlet. The use of a volumetric nozzle design in the present invention reduces turbulence and enhances the plug flow character of the water stream.

Referring to Fig. 1-2, the unit 11 acts similarly to an axial or turbine pump, which comprises a suction section I extending between lines AA to BB, a impeller section P extending between lines BB to CC and a discharge section D between lines CC to EE. A column of water drawn into the inlet passage 23 is activated and accelerated through the discharge section to provide thrust for a vessel 10.

The seagoing vessel 10 has the jet propulsion unit 11 for propellers installed in a tunnel in the rear section, so that the intake section I of the unit 11 is built into the bottom hull 9 between mounting blocks 7, and the discharge section D of the unit 11, which is held by cross members 5, extends out of the rear of the vessel instead of an ordinary impeller. The unit 11 is diagrammatically shown in two of its thrust positions: F - the forward propulsion position and R - the aft propulsion position. A drive engine 13 is directly attached to an impeller shaft 32 and a control link 15 is attached to the control means S of the drive unit 11.

Referring to Figs. 1, 4 and 5, the suction section I more specifically defines a suction passage 23 in a housing 12 communicating between a suction opening 22 formed in the bottom surface of the hull at one end and the suction opening 24 to the impeller section P at the other end. The passage 23, which is initially rectangular, has two vertical walls 152, a long inclined wall 153 and a short inclined wall 155, which converge at a bend 156 to form a cylindrical chamber. After the bend 156, the passage 23 is cylindrical. Converging walls of the passage 22 are suitably smoothed at intersections. and rounded to facilitate flow without turbulence. Typically, the angle of the bend 156 varies from about 40 to about 45 degrees depending on a specific design requirement. The cross-sectional area of the intake port 22 is preferably proportional to the cross-sectional area of the inlet 24 to an impeller 33 in a ratio varying from about 1.5 to about 2.5:1.

One or more straightening vanes 154 are disposed along the intake walls of the inlet casing 12. Directing vanes 154 are spaced radially along the surface of the inlet casing 12 so that equal volumes of water can be directed to the periphery of the impeller 33. Vanes 154 minimize radial loads on the impeller 33 for optimized flow performance. The vanes 154 also function to dampen any preliminary swirl and turbulence in the inlet water column.

Within the passage 23, as seen in Fig. 5, an intake grate 176 is arranged near the hull opening 22. The grate 176 is typically a covering of parallel bars arranged along the hull 9. The bars of the grate 176 have a streamlined or airfoil cross-section in the direction of the incoming flow to create minimal resistance to the water flow. The distance between the bars of the grate 176 should preferably not exceed the distance between diffuser vanes 40 to prevent the entry of large objects which cannot pass through unit 11.

If contamination occurs within the housing 12, an armhole conduit 100 is provided to allow quick access to the passage 23. The conduit 100 is located at the bend 156 and comprises a cylindrical housing 101 with an outer flange 102 and a plug 106. The plug 106 is provided with a solid portion 104 which is secured to a flanged cover 108 which completely fills the conduit housing 101. The portion 104 is provided with a smooth contour surface 103 which corresponds to the surface portion which is removed from the housing 12 at the bend 156 when the conduit 100 is installed. The line 100, when properly plugged, presents no additional resistance to flow or an area of flow disruption. The flange 102 is provided with upstanding threaded screws 109 which are inserted into holes in the flange 108 so that the plug 106 can be properly aligned during its installation. A handle 107 attached to the cover 106 provides additional alignment indicia.

A preferred feature of the present invention is a bypass valve assembly 172 mounted in the housing 12 near the inlet 24 shown in Fig. 1. Excess water is drained through the bypass valve assembly 172 when the water pressure between the hull 10 and the suction inlet 22 exceeds handling capacity. The buildup of excess water, colloquially known as agglomeration, is a common occurrence in Jet propulsion units for ships. When agglomeration occurs at high ship speeds, when the ship is subjected to sharp maneuvers, and/or during rough sea conditions, it imposes a high drag characteristic on the hull 10 and affects the propulsion performance of the unit 11. The valve assembly 172 functions as an anti-agglomeration device to reduce associated pressure.

The inlet section I is installed in the rear section of the hull so that forward movement of the vessel and subsequent elevation above the water surface allows the suction section I to be located slightly below the water level of the hull. However, for proper operation during a resting phase or at a low speed, the unit should be installed so that at least about 60 to 70 percent of the cross-sectional area of the impeller 33 is submerged. The suction section I is bolted to the hull, for example by means of a flange 150.

The impeller section P of the present invention, as seen in Figure 1, is shown from line AA to line BB as containing only a single stage impeller. The impeller assembly includes a removable housing 31 constructed from two smaller sections, an impeller housing 14 and a diffuser housing 16 having an impeller 33 and a diffuser 35. The impeller housing 14 is cylindrical with a generally uniform diameter at the inlet opening 24 and the outlet opening 26. The diffuser housing 16 is cylindrical with an inner surface extending from a maximum Diameter near the impeller section I to a minimum diameter near the discharge section D. The converging inner surface 39 of the diffuser housing 16 has an outlet cross-sectional area 28 which is preferably proportional to the cross-sectional area of the impeller section intake opening 24 in a ratio varying from about 0.5 to 0.75:1, preferably in a ratio of about 0.60 to about 0.70:1, and optimally about 0.64:1, such that the volumetric displacement of the diffuser section is less than the volumetric displacement of the impeller section. The volumetric displacement of the diffuser section is from about 75 to about 90 percent of the volumetric displacement of the impeller section, preferably from about 80 to about 90 percent of the volumetric displacement of the impeller section, and optimally 85 percent. In addition, the annular flow channel formed by the axial impeller/diffuser hub combination in the impeller housing 31 has smooth, substantially contiguous inner and outer surfaces to prevent turbulent boundary vortices. An important design criterion of the impeller section P is that the cross-sectional area of the impeller housing 14 and the diffuser housing 16 should be the same at the junction point 26.

With particular reference to individual parts of the impeller section P, the impeller assembly 33 has a unique design which has previously been subjected to many tests and modifications both with regard to the shape of a hub part 34 and the impeller blades 36, see Fig. 10-12, 14, 16-21. An essential aspect of the impeller 33 is that impeller blades 36 are hollow flattened blade sections mounted along an outwardly tapered convex surface 58 of the hub portion 34 as seen in Fig. 16, rather than a flat section as is typical in the prior art design.

Referring to Figures 14 and 16, an impeller hub 34 preferably has a convex surface and an annular interior, more preferably the hub 34 has an outer surface having a concave portion with a narrow diameter front end 60, a central portion 58 of increasing variable diameter, and a convex portion with a large diameter rear end 56 (viewed in axial cross section) and annular interior. The overall shape of the impeller hub 34 is designed so that the converging volumetric ratio begins in the annular space formed within the cylindrical impeller housing 14 in the intake section of the power unit of the present invention and compensates for the volume displaced by the impeller blades 36. A distal end 66 of the shaft 32 extends through a concentric axial bore 63 along the length of the hub 34. The forward end 60 has an annular end surface which abuts against a shoulder 68 on the shaft 32 to provide a smooth continuous surface for fluid flow. Annular walls of the hub 34, formed by concentric annular cavities 65 and 62, have a substantially constant thickness except for a distal annular end 64 which extends from the bore 63. extends outwardly, thereby providing a grippable surface for a closure layer 73.

As seen in Figures 10-12 and 17-21, the impeller 33 includes vanes 36 with hollow flattened sections mounted along the perimeter of the hub 34 at a slope designed to maximize the vanes' exposure to the fluid flowing therethrough and to reduce the radial acceleration component imparted by the impeller 33. Referring to Figure 18, the vanes 36 preferably have a convex outer radius 90, a concave inner radius 86, a short trailing edge 88, a long leading edge 84, wide surface sides 92 with a center P, and a thickness 91.

The pitch of the impeller blades 36 is defined as an average pitch or degree of twist in the length of the blades 36 as determined from the perpendicular with reference to a line tangent to the outer surface of the hub 34 at the leading edge 84 and at the trailing edge 88. When viewed along either the inner radius 86 or the outer radius 90 as in Figs. 17-19, or when viewed down the leading or trailing edge of the blade as seen in Figs. 20 and 21, an average pitch angle of both edge sides is preferably in a range of about 20-40 degrees from the perpendicular, more preferably about 30 degrees from the perpendicular, with one edge being pitched opposite to the other as required by the blade 36 to follow the contour of the hub surface 34. The leading edge is twisted in the direction of travel of the impeller rotation. It is that the leading edge 84 corresponds to the leading end 60 of the hub 34, which has a narrow diameter, and the trailing edge 88 corresponds to the trailing end 56 of the hub 34, and that the radial width of the center section of the vane 36 is a function of the radius of the center section region 58 of the hub 34, so that the impeller diameter is substantially constant. The overall length of the vane 36 is equal to the length of the hub 34 plus the angular component.

The wing 36 has a streamlined profile in cross-section that minimizes flow obstruction. In a radial direction, the thickness 91 of the wing 38 is substantially uniform. The leading or trailing edges 84 and 88 have a substantially uniform taper with a maximum thickness at a center that is approximately the same distance from each edge.

Figures 10-12 show a typical fan of five blades extending along the hub 34, but the number of blades, the impeller diameter and the degree of inclination can be optimized in relation to the power supplied by the propulsion engine 13 and in relation to the design considerations of the vessel in question.

The diffuser 35, as seen in Fig. 2, Fig. 8 and 9 and Fig. 14 (also sometimes known as a confusor), is located immediately adjacent to the impeller 33 and is designed to work in conjunction with the impeller 33 to achieve several important performance functions: (1) dampening a radial acceleration component; (2) spreading the path of water flow over the entire cross-section of the impeller face; (3) preventing partial vaporization of the fluid flowing therethrough resulting from a vacuum associated with impeller action by applying a low artificial back pressure to the impeller 33; and (4) enabling maximum impeller response and permitting more efficient transfer of the energy available to the prime mover. Any amount of steam present would cause uneven loading of the impeller 33 and cavitation.

The diffuser hub 38, as seen in Figures 15-16, preferably has an inwardly tapered convex surface and an annular interior space disposed oppositely with respect to the hub 34. The hub 38 has a large flat diameter front end 42, a decreasing variable diameter central portion 44, and a small diameter rear end 46 forming a rounded boss with a concentric bore 48 bored through the center thereof and a central annular end extension 54. The overall shape of the diffuser hub 38 is designed to maintain the converging volumetric ratio in the annular space formed within the diffuser housing 16 beginning in the intake section and continuing in the impeller housing of the drive unit of the present invention. A concentric outer annular cavity 52 is provided primarily for reducing excess weight, providing the hub 38 with walls of substantially constant thickness. A concentric inner annular bore 50 through the extended portion 54 defines a cylindrical housing for a bearing 82. The bore 50 has a reduced diameter in the boss portion 46 of the hub 38 as required by design stability criteria.

The design of the diffuser vanes is typically based on the design of standard straight vanes with the exception of significant changes built into the vanes 40 associated with the surface contour of the diffuser hub 38. The vanes 40 have a radial width that is a function of a diameter of the hub 38 so that the diffuser 35 has a constant diameter. The thickness of each vane may be streamlined or may typically be a uniform thickness throughout except for one edge side which may be edged or sharpened as required to fine tune the design. Vanes 40 have a leading edge 41 curved in a direction opposite to the direction of travel of the impeller 33 and a straight portion which is typically perpendicular to the hub surface, thus may be inclined at an angle of up to 10 degrees from an orthogonal plane bisecting the hub at the connection point and opposite to the direction of travel of the impeller 33 depending on the power tuning. The curved end 41 is typically at an angle of about 10 to about 40 degrees from a longitudinal plane bisecting the hub and includes a straight portion 43. The vanes 40 are securely attached longitudinally to one end of the perimeter surface of the hub 38 and to the inner walls of the housing 16 at the other and provide structural support for the Bearing function of hub 38. The number of diffuser vanes is selected taking into account the number of impeller blades in such a ratio that performance criteria of the diffuser section, e.g. back pressure and damping of radial acceleration, are achieved and that resonance and noise levels are minimized. An important design feature is the ratio of impellers to diffusers is odd:even or vice versa. For example, with 3, 5 or 7 impeller blades the corresponding number of diffuser vanes would preferably be 4, 8 or 10. Overall the diffuser is designed to control the shape of the water flow and the corresponding acceleration over a large pressure difference presented by a wide range of ship speeds, maneuvers and sea conditions.

The impeller assembly P, as seen in Fig. 1, is axially symmetrically disposed in the cylindrical impeller housing 31, with the diffuser assembly 35 mounted in close proximity behind the impeller assembly 33. The outer surface of the rear end 56 on the rotatable hub 34 is, as seen in Fig. 16, substantially continuous with the outer surface of the front end 42 on the fixed hub 38. The impeller assembly P is arranged so that this assembly can be easily and quickly removed for maintenance or replaced to enable adaptation of the impeller and the corresponding diffuser to the propulsion engine 13 and ship design requirements. The impeller housing 14 can have a replaceable wear sleeve 170, by means of which the diameter of the housing 14 can be reduced in accordance with the reduction of the diameter of the impeller 33.

In this way, a smaller diameter impeller arrangement can be used for smaller vessels. However, there is no limitation on high power or vessel size and the unit 11 can have a proportionally increased capacity for large vessels or for higher speed.

The impeller shaft 32 extending axially through the unit 11 is provided with a first bearing frame by the bearing assembly 140 which is secured to the inlet housing 12 and with a second bearing frame at the fixed hub 38. The bearing assembly 140 includes a housing 142, a roller bearing 144 and a locking ring 146. The bearing assembly 140 may further include a gear housing (not shown) for unit gearing to a particular prime mover requirement.

The shaft 32, as seen in Fig. 16, is provided with a shoulder 68 and a concentric distal portion 66 having portions 70 and 72 of progressively smaller concentric diameter. The impeller 33 slides onto the portion 66 of the shaft 32 so that the annular end of the leading edge 60 on the hub 34 abuts against the shoulder 68 to provide a smooth continuous surface for fluid flow. An annular locking sleeve 73 having a proximal annular end 74 having a larger diameter than a minimum diameter of the distal annular end 64 and extending outwardly from the hub bore 63 engages the annular end 64 holding the impeller 33 securely against the shoulder 68 on the shaft 32. A sealing ring 78 and a Locking screw nut 80 secures the sleeve 73. A distal portion 72 of the shaft 32 is threaded for locking the screw nut 80.

A combination of standard key (not shown) and keyway 67 synchronously engages the impeller 33 on the shaft 32.

The bearing sleeve 82 is inserted into the central annular portion 54 of the hub shell 38. The assembly is completed by inserting the shaft portion 70 with sleeve 73 through the bearing 82 so that the clearance between the hubs 34 and 38 is about 1/8 inch. A bore 48 in the boss end 46 of the fixed hub 38 provides an exit for water to wash around the exterior of the bearing 82. The bearing 82 is self-lubricating, self-cooling and self-flushing, which is typical of bearings used in marine applications.

Means for connecting the impeller section housing 14 to the suction housing 12 and a nozzle housing 20 to a discharge housing 18 include identical ring clamps 110 tightened by screws 113 within the clamp which fit over corresponding flanges 112 attached to the respective sections. The clamp 110 typically comprises two semi-circular grooved parts attached to a hinge 111. Additional connecting means include corresponding flange connectors using flanges 114 and 116 between the impeller housing 14 and the diffuser housing 16 and flanges 118 between the diffuser housing 16 and the discharge housing 18. Preferably a rubber gasket 115 is used therebetween. The rubber gasket 115 is typically an O-ring or sealing washer.

The design of the unit 11 is such that the control means S is seated centrally on the pump housing section 31 with a housing 130. Sections of the housing 130 are also connected by flanges 114, 116 and 118.

As seen in Figures 1, 6 and 7, an outlet or discharge section D extending from line C-C to line E-E comprises three cylindrical sections 18, 19 and 20 and serves two primary functions: to increase fluid velocity and to provide a means for pivotally directing the discharged stream to provide a control means. The discharge section D includes additional angles preferably from about 45 to 60 degrees or as required to horizontally align a discharge point 30 with the bottom hull 9 of a vessel 10 for discharging the discharged stream at or below the vessel's waterline.

The first section extending centrally from line C-C is the angled cylindrical housing 18. The housing 18 includes a pivotable portion 19 which is horizontally pivotable through 360 degrees. The pivotable second section 19 and the angled portion 18 are connected by the bearing assembly 120. The bearing assembly 120 includes an inner race 122 secured to the outer surface of the housing 18, an outer race 124 secured to the outer surface of the section 19, and a bearing ring 121 therebetween.

A control means 8 connects the control column 15 in a seagoing vessel to the rotary section 19 of the jet propulsion unit of the present invention. The control connection comprises a control rod 132 having a sleeve bearing 134 and first and second angle gears 136. The second angle gear 136, which is mounted on a control rod 138 and extends at an angle into the interior of the housing 18, is operatively connected to the rotary section 19 by means of spoke vanes 137. The control rod 138 has a sleeve bearing 135. Angle spoke vanes 137 are designed and installed so that they do not present an obstruction to the flow.

The third section of the vent D is a complementary angled housing 20 which is clamped to section 19 as previously mentioned and extends out to line EE. The housing 20 includes a nozzle 21 and is designed to be interchangeable to allow performance controlled selection of the nozzle 21. Alternatively, the nozzle 21 may have a variable outlet orifice for fine tuning flow rates and maximizing output performance by incorporating, for example, an iris-type mechanism (not shown). The cross-sectional area at the nozzle outlet 30 in the vent section D is preferably in a ratio of about 0.25 to about 0.50:1; preferably in a ratio of about 0.30 to about 0.40:1 and optimally about 0.35:1 proportional to the cross-sectional area of the impeller inlet 24. The inner surfaces of the discharge nozzle 21 are smooth and converge to the cross-sectional area of the outlet 30. In front of the nozzle 21, the discharge pipe a substantially constant diameter which is S-shaped in the forward direction. In addition, the constant diameter portion has a greater length dimension (measured along a centerline) than the nozzle 21 and a length to diameter ratio greater than 1.

The nozzle 21 includes one or more straightening vanes 162 preferably attached perpendicularly to the inner surface of section 20. The straightening vanes 162 are designed to dampen turbulence and allow a steady laminar column of water flow to be discharged from the unit 11. In addition, a ring 160 is attached to the outer edge of the nozzle 21 at the outlet 30. The ring 160 artificially increases the propulsive reaction of the discharged water by means of vortices formed around the ring edge to allow a smoother transition of the exiting water.

The discharge section D may further include a trim adjustment mechanism (not shown) for changing the height of the discharge outlet 30 relative to the water surface so that the current trim of the vessel can be adjusted if necessary. The trim adjustment mechanism preferably comprises overlapping sleeves arranged in the curved surface of one or both of the angled housing sections 18, 20 and means for positioning and locking the sleeves in a fixed position. Therefore, the vertical height of the outlet 30 is proportional to the angular arc in the sections 18 or 20, which can be increased or decreased by adjusting the degree of overlap of the sleeves. can be reduced in size. The positioning and locking means may be a hydraulic cylinder or a gear mechanism. The trim adjustment mechanism is particularly useful when the unit 11 is retrofitted to an existing vessel. For a new vessel designed to accept the drive unit 11, a trim adjustment capability is generally not required.

The vent housing 18 further includes an air opening 174 located approximately flush with the end of the diffuser hub 38 so that trapped air introduced into the unit 11 can escape and the unit 11 can be self-priming.

The control function of the discharge section D is included in the guidance of nozzle thrust as provided by the control device S. Direction sections are associated with the operation of the nozzle 21 in the positions F, R and radial positions therebetween.

As previously mentioned, excellent performance levels are obtained in the drive device of the present invention by causing the mass of water flowing therethrough to converge substantially uniformly on a volumetric basis as exhibited by fluid flow through a conventional nozzle or nozzle-shaped conduit. That is, the flow volume available per unit length (or alternatively axial cross-sectional flow area) preferably decreases substantially uniformly from inlet 22 to outlet 30. The flow volume per unit length of tunnel is defined as the volume of the tunnel minus the volume passed through the mass of the internal parts (e.g., impeller, diffuser, straightening vanes, shaft, etc.) per unit length. In this way, the tunnel passage has a nozzle-type flow characteristic. In a preferred embodiment, the unit flow volume of the drive device 11 substantially uniformly decreases in the manner of an ordinary nozzle or nozzle-shaped conduit having a convergence (reduction) angle of about 2 to about 15 degrees, and preferably about 5 to about 10 degrees. By nozzle-shaped duct is meant a duct with full convergent flow, which is constructed from one or more cylindrical and/or nozzle-shaped sections, where the convergence angle of the individual nozzle sections can be different, such as a nozzle duct constructed from a first section with a convergence angle of 10º, a second section with a convergence angle of 5º, a cylindrical third section and a fourth section with a convergence angle of 10º. The jet propulsion unit for a ship with a propeller in a tunnel of the present invention is preferably manufactured and assembled from stainless steel selected for its stability properties and resistance properties to corrosion, however a non-corrosive engineering plastic with good cohesive force would also be suitable for one or more parts of the propulsion unit.

It will be recognized that the performance of the jet propulsion unit 11 for a ship with propeller in a tunnel depends on the synergistic relationship the function of each individual section. Each individual section must be manufactured and assembled proportionally and symmetrically, taking into account the required pressure and flow balance needed to enable the jet propulsion unit to function effectively.

The predictability of performance in terms of the energy requirements of the jet propulsion unit allows the unit to be fine-tuned to a specific engine, taking into account the design criteria of the impeller blades associated with diffuser vanes and nozzle.

The foregoing description of the invention is intended to be illustrative and exemplifying of the same. Various changes in the materials, apparatus and specific parts employed will occur to those skilled in the art. It is intended that all such variations be included within the scope of the appended claims.

Claims (20)

1. A jet propulsion unit for a sea-going vessel, comprising: a converging intake section having convergingly tapered walls for receiving water from the vicinity of the unit, said walls having a smooth surface to inhibit turbulence; an impeller section for increasing the energy of water from said suction section; a diffuser section for promoting the axial flow of water from said impeller section; a pivotable discharge section for discharging water from said diffuser section in the form of a substantially plug-flow directed water jet; a cylindrical housing disposed in said impeller section having an inner surface of generally uniform diameter; a rotatable hub arranged concentrically in said cylindrical housing and having, viewed in axial cross-section, an outer surface having a concave portion and a convex portion and an outer diameter which extends from a minimum near said suction portion to a maximum near said diffuser section; a plurality of radially spaced impeller blades secured to said rotatable hub and extending from the outer surface of said hub to adjacent the inner surface of said cylindrical housing; said blades being inclined at an angle with respect to the longitudinal axis of said rotatable hub; an inner surface disposed in said diffuser section tapering from a maximum diameter proximate said impeller section to a minimum diameter proximate said discharge section; a fixed hub concentrically disposed within said diffuser section and having a convex outer surface tapering from a maximum diameter proximate said impeller section to a distal terminus proximate said vent section, said fixed hub outer surface and said inner surface defining an annulus within said diffuser section having a generally converging cross-sectional area; a plurality of radially spaced diffuser vanes extending from said outer surface of the fixed hub to said inner surface of the diffuser portion, wherein the said diffuser vanes have at least a distal region parallel to a longitudinal axis of said fixed hub proximate said discharge section; a bearing disposed between said rotatable hub and said fixed hub; and Means for rotating said rotatable hub with respect to said fixed hub. 2. The drive unit of claim 1, wherein said suction section includes an armhole conduit upstream of said impeller and a removable plug piece having an outer flange and an inner core, said core end having a contoured surface conforming to a wall of said suction section to present a generally smooth, continuous surface for fluid flow therethrough. 3. The drive unit of claim 1, wherein said intake section further comprises one or more straightening vanes securely mounted along an inner contour surface. 4. The power unit of claim 1, wherein a transverse inlet cross-sectional area of said intake section is proportional to an inlet cross-sectional area of said impeller section in a ratio of about 1.5 to about 2.5:1. 5. The drive unit of claim 1, wherein an outlet cross-sectional area of said diffuser section is proportional to an inlet cross-sectional area ratio of said impeller section in a ratio of about 0.50 to about 0.75:1. 6. The drive unit of claim 1, wherein a bypass valve is disposed upstream of said impeller blades for inhibiting agglomeration. 7. The drive unit of claim 1, wherein said bleed portion includes a removable nozzle secured to a housing by a quick connect member. 8. The drive unit of claim 1, wherein said discharge section comprises an adjustable nozzle with a variable outlet opening. 9. The drive unit of claim 8, wherein said nozzle is pivotable through 360º by a control mechanism. 10. The drive unit of claim 9, in which spoke vanes attach said control mechanism to the nozzle. 11. The drive unit of claim 7, wherein a discharge end of said nozzle has a fixed ring attached to attached to the same. 12. The drive unit of claim 1, wherein said discharge section further comprises one or more straightening vanes. 13. The drive unit of claim 1, wherein said bleed section further comprises a trim adjustment mechanism. 14. The drive unit of claim 1, wherein an outlet cross-sectional area of said discharge section is proportional to an inlet cross-sectional area of said impeller section in a ratio of about 0.25 to about 0.50:1. 15. The drive unit of claim 1, wherein said cylindrical housing is replaceable and said impeller portion further comprises a wear sleeve disposed between said inner diameter of said cylindrical housing and said impeller blades. 16. The drive unit of claim 1, further comprising a smoothly decreasing cross-sectional area of axial fluid flow from said suction section to said discharge section. 17. The propulsion unit of claim 1, wherein said discharge section has an outlet aligned with a vessel's hull and said water jet is at or below the waterline of the ship is drained. 18. The drive unit of claim 1, wherein said discharge section comprises a substantially constant diameter section and a nozzle section, the constant diameter section having a greater length than said nozzle section. 19. The drive unit of claim 18, wherein said constant diameter portion is S-shaped in the forward direction. 20. The drive unit of claim 18, wherein said constant diameter has a length to diameter ratio greater than 1.