Abstract:
The instant invention presents enhancements to waterjet propulsors used for propelling marine vehicles including a way to bleed off aerated boundary layer water from the inlet of the waterjet propulsor, air fences to further help in preventing aerated boundary layer water from entering the inlet of the waterjet propulsor, and a way to preclude water from entering the waterjet&#39;s water inlet when the waterjet is not operating and the marine vehicle is moving forward at high speed.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
     This application is a continuation-in-part to Applicant&#39;s earlier filed applications Ser. No. 09/702,905 filed Oct. 26, 2000, now abandoned, and Ser. No. 09/809,414 filed Mar. 15, 2001, now U.S. Pat. No. 6,629,866 issued Oct. 7, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     State of the art waterjet propulsors for marine craft utilize an impeller that pressurizes water supplied to the impeller from a water inlet. The pressurized water than passes through a stator that has fixed vanes to straighten out the water flow exiting the impeller. After exiting the stator, the pressurized water passes through a water-accelerating nozzle to thereby generate propulsive thrust. This type of waterjet propulsor is called a pressurized system waterjet here. 
     A shortcoming of these existing pressurized system waterjet designs is that they suffer serious performance falloff when air or other gas is included in their inlet fluid flow. Tests run on pressurized system waterjets at Pratt &amp; Whitney Aircraft in the sixties showed that serious loss of performance resulted from as little as three to five percent of air or other gases by volume of total inlet fluid flow. This is because the compressible gas degrades the efficiency of the waterjet&#39;s water pressurizing impeller. Two primary sources of air entrained in the inlet water of a waterjet are due to: 1) Boats operating in rough seas where air flow is trapped under the hull and passes into the waterjet inlet and 2) Air cushioned boats where the underside of the hulls are partially aerated as a normal condition of operation. 
     As a point of interest, some of Applicant&#39;s earlier work, such as given in the continuation-in-part applications listed under a preceding section titled CROSS REFERENCE TO OTHER APPLICATIONS, revolve around enclosed or semi-enclosed rotor propulsors that operate partially aerated as a preferred condition. Such units are designed to operate as mainly non-pressurized systems with their rotors aerated. As such, it is normally not necessary to bleed off entrained air or gas in their water inlets. 
     A second shortcoming of existing waterjets is that, in boats with multiple waterjet propulsors, the drag or resistance of a non-operating waterjet becomes very high as boat speed is increased. This is due to the resistance of the water flow passing through the non-operating waterjet. 
     The instant invention addresses both of the aforementioned shortcomings of existing state-of-the-art pressurized system waterjets. This is accomplished by offering a way to bleed off part or all of the air in the waterjet inlet water and a way to deflect at least most of the water from entering the inlet of a non-operating waterjet when moving forward a high speeds. A further enhancement is the use of air fences that restrict water containing entrained air from entering from the sides of the waterjet&#39;s water inlet. For purposes of this application, high speed is defined as being fifteen knots or higher. 
     SUMMARY OF THE INVENTION 
     With the foregoing in mind, it is a principal object of the present invention to provide an improved waterjet propulsor for marine craft that has a boundary layer bleed opening disposed, at least in its majority, forward of the waterjet propulsor&#39;s powered rotor, said boundary layer bleed opening taking in aerated boundary layer water thereby reducing the amount of air entering the powered rotor during high speed forward operation of the marine craft. 
     A related object of the invention is that the boundary layer bleed opening extends, as a sum of its openings, over a majority of a width of the waterjet&#39;s fluid inlet. 
     A further object of the invention is that aerated boundary layer water taken in by the inlet boundary layer bleed opening passes through a valve that controls flow of the aerated boundary layer water. 
     Yet another object of the invention is that the aerated boundary layer water taken in by the inlet boundary layer bleed opening passes through a bypass pump that accelerates flow of the aerated boundary layer water. 
     Another related object of the invention is that at least a portion of the aerated boundary layer water taken in by the inlet boundary layer bleed opening be dispensed or discharged into the waterjet propulsor downstream of the waterjet rotor. 
     A directly related object of the invention is that at least a portion of the aerated boundary layer water taken in by the boundary layer bleed opening be dispensed or discharged from a stator vane assembly disposed downstream of the waterjet rotor. 
     Another related object of the invention is that at least a portion of the aerated boundary layer water taken in by the boundary layer bleed opening be dispensed or discharged from a waterjet nozzle of the improved waterjet propulsor. 
     A further object of the invention is that there be a first air fence disposed, at least in its majority, to one side of the waterjet fluid inlet. 
     A directly related object of the invention is that there be a second air fence disposed, at least in its majority, to an opposite side of the waterjet fluid inlet from the first air fence. 
     Yet another object of the invention is that it include an inlet flow deflector that, when extended, deflects fluid flow from entering the waterjet fluid inlet. 
     A directly related object of the invention is that force for movement of the inlet flow deflector be provided by a powered actuated. 
     A further related object of the invention is that the inlet flow deflector, as a sum of its parts, extend over a majority of a width of the waterjet fluid inlet. 
     Yet one more object of the invention is that the instant invention waterjet propulsor can be a pressurized system waterjet. 
     The invention will be better understood upon reference to the drawings and detailed description of the invention which follow in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 presents a partial underside plan view of an instant invention waterjet propulsor as installed in a boat hull. 
     FIG. 2 is a centerline cross sectional view, as taken through vertical centerline plane line  2 — 2  of FIG. 1, that shows the waterjet&#39;s rotor or impeller and its drive motor, an inlet water deflector, and boundary layer air bleed mechanism in a preferred embodiment. 
     FIG. 3 is another cross-sectional view of the instant invention waterjet propulsor, as taken through line  3 — 3  of FIG. 1, that illustrates the water flow pattern with the inlet fluid flow deflector extended so that it prevents all or at least most of oncoming water from impacting the waterjet&#39;s inlet opening. This is a desirable condition to reduce drag when operating at high boat speeds with a waterjet not operating. 
     FIG. 4 presents a partial cross section, as taken through line  4 — 4  of FIG. 2, that shows an aerated boundary layer or air layer forward of the waterjet inlet. This view also shows air fences disposed along the boat&#39;s bottom. 
     FIG. 5 gives another cross section, as taken through line  5 — 5  of FIG. 2, that shows a section of the aerated boundary layer bleed mechanism. This includes a bypass valve and bypass pump in this version of the instant invention. 
     FIG. 6 is a partial cross sectional view that is the same as that given in the cross sectional view of FIG. 2 but in a simpler form. The optional bypass valve, bypass pump, and waterjet inlet fluid flow deflector have been eliminated in this simplest version of the instant invention. 
     FIG. 7 presents a partial vertical centerline plane cross section, similar to that presented in FIG. 2, that shows an alternative means of dispensing the aerated boundary layer water taken in by the boundary layer bleed. In this case, the dispensing takes place from the stator vane assembly. Aspiration of the aerated boundary layer water here provides impetus for sucking the boundary layer in at the boundary layer bleed. This is the same situation as exists when the aerated boundary layer water is dispensed into the waterjet nozzle. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 presents a bottom plan view of the instant invention waterjet propulsor  53  installed in a boat hull  35  that is shown in partial section. Shown are aerated boundary layer water  31  that is passing under the boat hull  35 , boundary layer bleed opening  45 , water flow arrows  32 , aerated boundary layer water flow arrows  33 , aerated boundary layer water bleed line discharge opening  54 , air fences  44 ,  54 , waterjet inlet fluid flow deflector  46 , waterjet propulsor vertical centerline plane  55 , and waterjet discharge nozzle  40 . Note that the aerated boundary layer forward  31  forward of the waterjet fluid inlet  52  is mostly taken in at the boundary layer bleed opening  45  here. 
     FIG. 2 is a centerline cross sectional view, as taken through the vertical centerline line  2 — 2  of FIG. 1, of the instant invention showing an aerated boundary layer bleed line  39  that takes in aerated boundary layer water  31  at its boundary layer bleed opening  45 . The boundary of the aerated water is roughly depicted by boundary layer line  30 . In this elaborated version of the instant invention, the aerated boundary layer water passes through a bypass valve  36  that is operated by a bypass valve powered actuator  50  and a bypass or boost pump  37  that is powered by bypass pump motor  51 . The discharge of the aerated boundary layer water  31  is normally accomplished by dumping it into the waterjet nozzle  40  at the aerated boundary layer water bleed line discharge  54 . This creates an aspirating effect on the aerated boundary layer water  31  in the bleed line  39 . However, it is not necessary to have the aerated boundary layer discharge into the waterjet nozzle to make a workable system since, in this instance, the optional bypass pump  37  provides energy to move the fluids in and discharge the fluids from the aerated water boundary layer bleed line  39 . 
     The actual waterjet propulsor rotor or impeller  41  is driven by its motor  38  through shaft  43 . Note that the three motors or actuators,  38 ,  50 , and  51  are not shown in cross section to simplify the drawings. Discharge from the waterjet impeller  41  normally would pass through a flow straightening stator assembly  42  and then out a waterjet nozzle  40 . The accelerated fluid discharge from the waterjet nozzle  40  produces the waterjet&#39;s thrust. 
     Other items shown in FIG. 2 include a waterline  34 , an air fence  44 , waterjet inlet fluid flow deflector  46 , and waterjet inlet fluid flow deflector actuator  47 . 
     FIG. 3 is a cross-sectional view, as taken though line  3 — 3  of FIG. 1, that presents a view to one side of a vertical centerline plane  55  of the instant invention waterjet propulsor  53 . Note that in this instance the waterjet inlet fluid deflector  46  is extended to thereby deflect at least most of the passing fluids from entering the waterjet fluid inlet  52 . While, the waterjet inlet lip  48  is actually not impacted by passing fluids in this example it is possible that at least some impact on the waterjet inlet lip  48  will occur. In any case, the ability to deflect fluids from entering the waterjet fluid inlet  52  is invaluable for reducing drag of a non-operating waterjet propulsor when a boat is traveling forward at high speed. 
     FIG. 4 is a cross section, as taken through line  4 — 4  of FIG. 2, that shows the aerated boundary layer water  31  forward of the waterjet inlet. Note the two air fences  44 ;  54  here. 
     FIG. 5 is a cross section, taken through line  5 — 5  of FIG. 2, that shows the aerated boundary layer water entering the boundary layer bleed opening  45 . The air fences  44 ,  54  prevent aerated water from entering the waterjet inlet from its sides. After entering the aerated boundary layer water bleed line  39  the aerated boundary layer water bleed flow  31  passes through a bypass valve  36  and bypass pump  37  in this elaborate version of the invention. 
     FIG. 6 gives a simpler version of the invention. It is shown in the form a partial version of a similar vertical centerline plane cross section that was presented in FIG.  2 . However, in this preferred embodiment version, there is no bypass valve or bypass pump in the aerated boundary layer water bleed line  39 . Part of the force for moving the fluid in this case comes from the aspirating effect of the discharge nozzle fluid flow on the discharge of the fluid from the boundary layer bleed line  39  into the waterjet nozzle. For further simplicity, the optional waterjet inlet water flow deflector is eliminated here. 
     FIG. 7 presents, in a partial vertical centerline cross section similar to that presented in FIG. 2, an optional situation whereby the aerated boundary layer water  31  is discharged through the stator vane assembly  42 . This approach is actually the most elegantly simple and a preferred embodiment since the aspirating force on the aerated boundary layer water  31  discharging from the stator vane assembly  42  is very high. 
     While the invention has been described in connection with a preferred and several alternative embodiments, it will be understood that there is no intention to thereby limit the invention. On the contrary, there is intended to be covered all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims, which are the sole definition of the invention.