Abstract:
Presented is a fluid propulsor for propelling a vehicle that incorporates a Coanda Effect Inducer (CEI), more commonly called an inlet fluid inducer in this application, in its inlet to induce fluids passing by the vehicle to turn uniformly toward a powered fluid energizing device such as a rotor of the propulsor. This concept enhances the efficiency of the rotor and the overall efficiency of the propulsor. The rotor is preferably at least primarily enclosed in a housing and the rotor may operate either fully submerged in liquid or in a partially liquid and partially gaseous environment. The CEI and the powered fluid energizing device are, in the preferred embodiment, installed in an inlet housing of the propulsor. Fluid flow directing devices may be incorporated to separate liquid from gas flowing to the rotor in some instances. The inlet fluid inducer may take the shape of a cylinder or any other flow directing shape and while more effective when rotating in the direction of fluid flow is also viable when not rotating.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
       [0001]    This application is a continuation-in-part to applicant&#39;s earlier applications: Ser. No. 11/088,212 filed Mar. 18, 2005 now abandoned, Ser. No. 11/373,620 filed Mar. 10, 2006 now U.S. Pat. No. 7,422,498 issued Sep. 9, 2008, and Ser. No. 11/526,958 filed Sep. 26, 2006 now abandoned. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Enclosed rotor propulsion system for marine craft, such as waterjets and Applicant&#39;s enclosed ventilated rotor Hydro Air Drive® (HAD) invention, are limited in the overall efficiency they can realize by the efficiency of recovery by their water inlets of the fluid available at their water inlets. As an example, waterjets can have very high efficiency rotors, stator vanes that straighten the discharge flow of the rotors, and discharge nozzles. The overall efficiency of the just mentioned three items are in the 90% or higher area for a well-designed high power level waterjet. 
         [0003]    However, the overall efficiency of a waterjet is severely limited by its inlet&#39;s ability to recovery oncoming fluids efficiently. This is because the oncoming fluid flow is forced to turn into the duct that surrounds the waterjet&#39;s rotor. As an example, a waterjet&#39;s inlet may see efficiencies of fluid recovery of 92% over its lower half but only 54% or so over its upper half. This is because the fluid flow is separating over the upper part of the inlet duct as it is trying to turn from the inlet toward the rotor. This is so even though the waterjet operates as an enclosed pressurized system and thereby is creating suction at its inlet. 
         [0004]    The HAD sees a slightly different situation in that it is not a pressurized system and therefore does not create much of a suction at its inlet. The advantage of the HAD is that it only operates with the lower half of its rotor submerged so its inlet fluid does not have to turn as far as does the waterjet&#39;s. However, the lack of inlet suction of the HAD does hamper the ability of its inlet to fully recover fluid approaching its inlet. 
         [0005]    What all of this means is that propulsors, such as the waterjet and the HAD, would benefit greatly by having water inducer devices at their inlets. As a side point, it is realized that having a straight-in inlet with the inlet in-line with the rotor with no turns would provide high inlet efficiencies. Such an in-line inlet is sometimes referred to as a ram inlet. The shortcomings of the ram inlet are twofold—it: 1) has high drag due to the inlet&#39;s frontal area and 2) increases vessel draft since the ram inlet is normally lower than the vessel&#39;s keel. These shortcomings of the ram inlet are overcome by the instant-invention while maintaining the ram inlet&#39;s high efficiency. 
         [0006]    The Coanda Effect can be used for turning fluids around curved surfaces and has been known for years. This Coanda Effect can be improved by use of a rotating cylinder or other curvilinear shape placed perpendicular to or at least partially perpendicular to the fluid flow to entice the fluid to turn in the direction of rotation of the rotating surface. The instant invention takes advantage of these known sciences and places a Coanda Effect Inducer (CEI) at or near the entrance of the receding inlet surface of a propulsor&#39;s inlet. The effect of the CEI is to greatly improve the recovery of fluids flowing past the propelled vehicle and of delivering such fluids to a fluid energizing device, such as a rotor, of the propulsor. This greatly improves the overall efficiency of the propulsor and hence the performance of the vehicle. Hereinafter, the CEI is commonly called an inlet fluid inducer. 
         [0007]    What is called the receding inlet surface hereinafter is normally the upper surface in a standard waterjet propulsor installation. Such an upper receding inlet surface may be seen in Burg, U.S. Pat. No. 6,629,866, where, in that example, inlet flow directing valves  49 ,  51  act as the preceding mentioned receding inlet surface of the propulsor. Burg&#39;s flap-like flow directing valves  49 ,  51  are incapable of rotation through 360 degrees nor do his flap-like devices  49 ,  51  extend below the outlines of his hull which is the preferred embodiment of the instant invention especially when the instant invention&#39;s fluid inlet inducer  30  is fixed and not rotating. Propulsors installed in the sides of hulls, as presented in continuation-in-part Burg, U.S. Pat. No. 7,422,498, may see the receding inlet surface and its CEI more vertically oriented. In the instant invention the receding inlet surface may be oriented horizontally or at any angle to horizontal. 
         [0008]    Willyard, U.S. Pat. No. 4,070,982, has a drive cylinder  16  disposed at the forward end or bow of a vessel  10  that energizes oncoming water. The energized water then flows completely through the length of the vessel  10  in a duct  15  to be discharged at the aft end of the vessel  10  thereby providing forward thrust. Portions of Willyard&#39;s energized water may be directed to a propeller  32  in a duct  31  positioned at the aft end or transom of his vessel  10 . However, in no case does Willyard offer a CEI that is in powered communication with his propeller  32  except by the passing energized water. Further, Willyard does not offer a CEI that is housed in housings that also house the propelling rotor as does the instant invention. The instant invention, in its preferred embodiment, has its CEI integral with its rotor housing and/or an inlet housing attached to the rotor housing which is very important in order to simplify fabrication, installation, and maintenance. Further, Willyard has his drive cylinder  16  disposed at the water surface at the very bow of his vessel so that it sees oncoming waves and water mixed. This is contrary to the instant invention wherein the CEI is normally disposed at a further aft portion of the vessel&#39;s hull and normally sees only oncoming water. 
         [0009]    A discussion of the instant invention and the advantages it offers is presented in detail in the following sections. 
       OBJECTS OF THE INVENTION 
       [0010]    A primary object of the invention is provide an improved propulsor for propelling a vehicle where said propulsor accelerates fluid to produce thrust and where said fluid is obtained through an inlet that intakes fluid from external to the vehicle and directs said fluid toward a fluid energizing device wherein said inlet includes an inlet fluid inducer and wherein said inlet fluid inducer directs said fluid toward a fluid energizing device such as a powered rotor. 
         [0011]    A related object of the invention is that the inlet fluid inducer may rotate. 
         [0012]    A directly related object of the invention is that the inlet fluid inducer provide a uniformity to the energy in the fluid supplied to the fluid energizing device. 
         [0013]    A related object of the invention is that said inlet fluid inducer be oriented more perpendicular to than parallel to a plane that includes a rotational axis of the fluid energizing device. 
         [0014]    A further object of the invention is that the inlet fluid inducer be capable of rotation in the direction of fluid flow. 
         [0015]    Yet another object of the invention is that the inlet fluid inducer extend less than 60 percent of its maximum dimension perpendicular to fluid flow beyond an average height of a vehicle hull portion when said vehicle hull portion is viewed proximal to, forward of, and in line with the inlet fluid inducer. 
         [0016]    A directly related refining object of the invention is that said inlet fluid inducer extend less than 40 percent of its maximum dimension perpendicular to fluid flow beyond an average height of a vehicle hull portion when said vehicle hull portion is viewed proximal to, forward of, and in line with the inlet fluid inducer. 
         [0017]    A further directly related refining object of the invention is that said inlet fluid inducer extend less than 20 percent of its maximum dimension perpendicular to fluid flow beyond an average height of a vehicle hull portion when said vehicle hull portion is viewed proximal to, forward of, and in line with the inlet fluid inducer. 
         [0018]    Yet another object of the invention is that the inlet fluid inducer may rotate freely in the direction of fluid flow through 360 degrees of rotation with no powering means. 
         [0019]    Another object of the invention is that the inlet fluid inducer may be driven by a power source that also drives the fluid energizing device through 360 degrees of rotation. 
         [0020]    A directly related object of the invention is that a drive shaft of a fluid energizing device may also drive the inlet fluid inducer. 
         [0021]    Still another object of the invention is that the fluid energizing device may receive primarily liquid over one portion of its rotation and primarily gas over another portion of its rotation. 
         [0022]    A related object of the invention is that a fluid directing device may be disposed at least in its majority downstream of the inlet fluid inducer. 
         [0023]    A directly related object of the invention is that the fluid directing device has the ability to, in at least one mode of its operation, restrict gas from passing to the fluid energizing device. 
         [0024]    Another object of the invention is that the fluid directing device be powered by an actuator. 
         [0025]    Yet another object of the invention is that the inlet fluid inducer may include recesses in its periphery that are capable of energizing fluids when the inlet fluid inducer is rotating. 
         [0026]    A further object of the invention is that the inlet fluid inducer may be driven with gears. 
         [0027]    Still another object of the invention is that the fluid energizing device be a rotor. 
         [0028]    Yet another object of the invention is that the fluid discharge from the fluid energizing device may be given direction by a rudder. 
         [0029]    A further object of the invention is that the inlet fluid energizing device by supported by an inlet housing of the marine propulsor. 
         [0030]    Another object of the invention is that the inlet fluid inducer and the fluid energizing device be in mechanical communication in a common housing or a connected housing. 
         [0031]    It is still another object of the invention that the inlet fluid inducer should be relatively close to the fluid energing device to maximize overall system efficiency. 
         [0032]    A directly related object of the invention is that a distance from an aft portion of the fluid inlet inducer to a forward portion of the fluid energizing device be no more than six diameters of the fluid energizing device or rotor. 
         [0033]    Another directly related object of the invention is that a distance from an aft portion of the fluid inlet inducer to a forward portion of the fluid energizing device be no more than four diameters of the fluid energizing device or rotor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  shows a centerline cross-sectional profile view of a prior art waterjet propulsor. 
           [0035]      FIG. 2  presents a cross-section, as taken through plane  2 - 2  of  FIG. 1 , that shows the general values of recovery of fluids by the inlet as seen at a plane just forward of the fluid energizing rotor that can be expected in a commercial waterjet based on present day designs. Note that the overall inlet efficiency, based on 92% in the lower half and 54% in the upper half, comes to only about 73%. 
           [0036]      FIG. 3  is the same centerline cross-sectional profile view as given in  FIG. 1  but in this case a Coanda Effect Inducer (CEI), also called as an inlet fluid inducer herein, has been added as is a preferred embodiment of the instant invention. The direction of rotation of the inlet fluid inducer aids in directing the inlet water in a uniform manner to the fluid energizing rotor. Note that the fluid inlet inducer is shown as being able to rotate through a full 360 degrees of rotation which is the preferred method of operation. However, it may also be fixed in position where, while not as efficient in so doing, it will also provide the Coanda effect of turning the inlet fluid upward toward the rotor. The fluid inlet inducer may have its rotation powered or non-powered where in the latter case it is free-wheeling. 
           [0037]      FIG. 4  gives a cross-section, as taken through line  4 - 4  of  FIG. 3 , that gives the predicted values for the recovery of fluids by the inlet with the inlet fluid inducer rotating. Note that predicted recovery values of fluids entering the lower portion of the fluid energizing device is 96% and over the upper portion 90%. This results in an overall inlet efficiency of 93%. The very important result is that there is about a twenty-five percent improvement in overall efficiency for a waterjet with the inlet fluid inducer compared to one without an inlet fluid inducer. 
           [0038]      FIG. 5  illustrates a proposed version of a inlet fluid inducer, as taken through plane  5 - 5  of  FIG. 3 , that shows one possible means of driving this cylindrical shaped inlet fluid inducer. In this particular case the drive means consists of a drive motor with power transmitted through gears. 
           [0039]      FIG. 6  presents a cross-section, as taken through line  6 - 6  of  FIG. 3 , that shows a preferred flat surface forward to the inlet fluid inducer. Note that the lower surface of the inlet fluid inducer is disposed more into the oncoming fluid than surfaces of the hull forward of the inlet fluid inducer in this example. This preferred approach insures optimum performance of the inlet fluid inducer while adding very little additional drag. 
           [0040]      FIG. 7  presents a partial profile centerline cross-section of a HAD with an instant invention inlet fluid inducer applied. There are, ideally, fluid directing means—flaps in this illustration—applied to either side of the shaft here. In this instance, the fluid directing means are retracted to their most upward positions which allows water to flow to the entire HAD fluid energizing rotor from top to bottom. This is the preferred position of the fluid directing means for low vehicle speed operation when maximum low speed thrust is desired. 
           [0041]      FIG. 8  is the same partial profile centerline cross-section of a HAD as presented in  FIG. 7  but in this case the fluid directing means are extended downward to aid in directing fluids to only a portion of the fluid energing rotor. It is important to note also that a lowered position of the fluid directing means allows gas to pass to the upper portion of the fluid energizing rotor. As such, the rotor is operating only partially submerged which has advantages compared to standard pressurized system waterjets. These advantages are discussed later in this application. 
           [0042]      FIG. 9  is a cross-sectional plane, as taken through  9 - 9  of  FIG. 7 , that shows the fluid directing means in their retracted position. Note that in this position the fluid directing means restrict the flow of gases to the fluid energizing device which is normally a rotor with blades. 
           [0043]      FIG. 10  is a cross-sectional plane, as taken through  10 - 10  of  FIG. 8 , that illustrates how the fluid directing means are positioned during high speed vehicle operation where the fluid energizing device is only partially submerged. 
           [0044]      FIG. 11  presents a cross-sectional plane, as taken through line  11 - 11  of  FIG. 7 , that shows the fluid flow distributions just forward of the fluid energizing rotor when the fluid directing means are in their retracted position. 
           [0045]      FIG. 12  is a cross-sectional plane, as taken through line  12 - 12  of  FIG. 8 , that illustrates fluid flow distributions just forward of the fluid energizing rotor when the fluid directing means are in an extended high vehicle speed position. Note that there is gas above the fluid directing means and water below it in this instance. Inlet recovery efficiencies should be in the 98% area over the lower half of the fluid energizing rotor in this instance. 
           [0046]      FIG. 13  illustrates fluid flow inlet characteristics when the inlet fluid inducer is not rotating. While this is very workable and considered part of the instant invention, performance is substantially better when the inlet fluid inducer is rotating in the direction of the water flow. 
           [0047]      FIG. 14  shows a cross-sectional plane, as taken through line  14 - 14  of  FIG. 13 , that illustrates water flow characteristics with the inlet fluid inducer not rotating. Comparing this  FIG. 13  to  FIG. 12  gives some idea of the expected performance improvements to having the inlet fluid inducer rotating. 
           [0048]      FIG. 15  illustrates flow characteristics around a non-rotating cylinder disposed perpendicular to fluid flow. Note that the flow separates around the aft side of the cylinder. 
           [0049]      FIG. 16  shows the same cylinder as that presented in  FIG. 15  but with the cylinder rotating. It is apparent that the fluid does not detach as is the case of the non-rotating cylinder of  FIG. 15 . This rotating cylinder makes for a much more efficient and low drag situation than the non-rotating cylinder of  FIG. 15 . Both  FIGS. 15 and 16  actually show characteristics of the Coanda Effect since the fluid is at least partially attached to the curvilinear surfaces and turn inward in both instances. 
           [0050]      FIG. 17  shows the same HAD unit as shown previously; however, in this case the inlet fluid inducer is cylindrical and rotating in an opposite direction to travel and freestream fluid flow. This has merit in a case where a HAD or waterjet is not operating but the vehicle is still moving forward as would be the case of operating with their drive engine out but with other propulsors still operating. The reason this is so is that the forward direction of rotation of the inlet fluid inducer directs oncoming fluids away form the HAD&#39;s inlet thereby reducing drag forces that would occur with fluid entering a non-operating unit. 
           [0051]      FIG. 18  presents a centerline profile cross-section plane that shows an alternate method of driving an inlet fluid inducer. In this case the inlet fluid inducer is directly driven by a main drive shaft of a propulsor. Also, this figure shows how an inlet fluid inducer could work when operating in reverse as is the inlet fluid inducer here. Running the inlet fluid inducer in reverse, either powered or non-powered, along with reverse operation of the rotor results in enhanced reverse thrust. 
           [0052]      FIG. 19  presents a cross-section plane, as taken through  19 - 19  of  FIG. 18 . 
           [0053]      FIG. 20  is a cross-section plane, as taken through  20 - 20  of  FIG. 18 . The inlet fluid inducer illustrated here is in the form of truncated cones either side of a gear drive track. Realize that the inlet fluid inducer can take many shapes to accommodate different hull shapes, inlet designs, and the like. 
           [0054]      FIG. 21  is another cross-section plane, as taken through  21 - 21  of  FIG. 18 , that shows an optional elliptical, as seen in this cross-section, shaped inlet fluid inducer. 
           [0055]      FIG. 22  shows yet another version of an inlet fluid inducer that in this case is made up of two separate parts. 
           [0056]      FIG. 23  is a partial centerline cross-section plane with a variation of an inlet fluid inducer that incorporates pumping recesses to enhance pumping or fluid accelerating abilities of the inlet fluid inducer. 
           [0057]      FIG. 24  is a cross-section plane, as taken through  24 - 24  of  FIG. 23 , that shows the preferred shape and workings of the inlet fluid inducer variation of  FIG. 23 . 
       
    
    
     DETAILED DESCRIPTION 
       [0058]      FIG. 1  shows a centerline cross-sectional profile view of a prior art waterjet propulsor as it is propelling a vehicle  39  forward at high speed. Note that high speed is defined herein as being forward speeds of 15 knots or more and low speeds as speeds of less than 15 knots. Shown also are the shaft  31 , fluid energizing device which in this case is a rotor  42 , stator including flow straightening stator vanes  40 , and discharge nozzle  41 . Other items of interest include inlet housing  34 , vehicle hull  39 , waterline  45 , waterflow arrows  37 , turbulent water flow arrows  50 , and thrust arrow  51 . The power source is not shown to simplify the drawings. Note that the turbulent water flow arrows  37  indicate that the water flow is separating over the upper surface of the inlet housing  34 . 
         [0059]      FIG. 2  presents a cross-section, as taken through plane  2 - 2  of  FIG. 1 , that shows the general values of recovery of energy available at the inlet  55  in a plane just forward of the rotor  35  as can be expected in a large commercial waterjet to today&#39;s technology. The overall inlet efficiency can be approximately determined from the inlet pressure islands  47 . Note that the approximate overall inlet efficiency, based on 92% in the lower half and 54% in the upper half, comes to only 73%. 
         [0060]      FIG. 3  is the same centerline cross-sectional profile view as given in  FIG. 1  but in this case a Coanda Effect Inducer (CEI), more commonly called an inlet fluid inducer  30  herein, has been added as is one form of a preferred embodiment of the instant invention marine propulsor  53 . The direction of rotation, as shown by rotation arrow  49 , of this inlet fluid inducer  30  aids in directing and adding energy to the recovered incoming fluid as it is directed to the fluid energizing device such as rotor  42 . Note that the fluid inlet inducer  30  is shown as being able to rotate through a full 360 degrees of rotation which is the preferred method of operation. However, it may also be fixed in position where, while not as efficient in so doing, it will also provide the Coanda effect of turning the inlet fluid upward toward the rotor. The fluid inlet inducer  30  may have its rotation powered, the most efficient means for turning the inlet fluid upward toward the rotor  42 , or non-powered where in the latter case it is free-wheeling. 
         [0061]    The inlet fluid inducer  30  should be relatively close to the fluid energing device or rotor  42  for maximum overall system efficiency. A distance from an aft portion of the fluid inlet inducer  30  to a forward portion of the fluid energizing device  42  of no more than six diameters of the fluid energizing device or rotor  42  is desired with values of less than four diameters preferred. Further, in this preferred embodiment of the instant invention, the inlet fluid inducer  30  is supported by the inlet housing  34 . The two items presented in this paragraph are very important as they make for the best manufacture, installation, maintenance, and efficiency. 
         [0062]    The dimension A given in  FIG. 3  shows that the inlet fluid inducer  30  can extend below the average depth of the hull portion  39  forward of the inlet fluid inducer  30 . Having the inlet fluid inducer  30  on average lower than the hull portion  39  forward of it allows the inlet fluid inducer  30  to operate more efficiently and in cleaner water. This is done with very little addition to the drag of the inlet as will be discussed later in the descriptions of  FIGS. 15 and 16 . 
         [0063]    In  FIG. 3  and subsequent figures in this application, dimension A is best defined as a percentage of the diameter of the inlet fluid inducer  30  and may extend to as much as 60 percent or more of the diameter of the inlet fluid inducer  30  and offer advantage in efficiency of recovery of fluids external to the inlet and still add little drag to the vehicle. For purposes of this application, the amount that the inlet fluid inducer  30  can extend beyond the average height of a hull portion  39  forward of the inlet fluid inducer  30  is either not specified or defined as less than 60% of inlet fluid inducer  30  diameter, less than 40% of inlet fluid inducer  30  diameter, or less than 20% of inlet fluid inducer  30  diameter. It is to be noted that the term diameter used here can actually be the maximum dimension of the inlet fluid inducer  30  that is perpendicular to fluid flow as could be the case for shapes other than cylindrical. 
         [0064]    Each of these extensions, relative to the hull portions, have advantages and disadvantages. For example, in the case of a Surface Effect Ship (SES) such as applicant&#39;s SeaCoaster® that is supported by pressurized gas cushions with the propulsor inlets disposed at least primarily aft of the gas cushions it is best to have the inlet fluid inducer  30  extend beyond the hull portion in front of it as far as possible. This is because the gas cushions aerate the water and there may also be a layer of gas between the hull  39  and the water surface when it reaches the propulsor&#39;s water inlet. Having the inlet fluid inducer  30  extend outward beyond the hull means that its outward portions can work in relatively clean gas free liquid. Contrarily, it is desirable to have the inlet fluid inducer  30  not so far extended for a very high-speed craft. 
         [0065]    Large displacement hulls may find extension of the inlet fluid inducer  30  to work best when at low values also. This is because of the boundary layer associated with large displacement hulls and the desire to take in water to the propulsor from close to the hull where it has already been brought up to near ship speed. The advantage of the instant invention in such a displacement hull application is that the propulsor gets an added thrust advantage from taking in the ship&#39;s accelerated boundary layer rather than quiescent water in outer reaches of the boundary layer. It is further to be noted that the instant invention may be disposed so that it is actually has all or part of its inlet higher than its fluid energizing rotor as would be the case when operating on the upper or side surfaces of hydrofoil, submarine, or other submerged or partially submerged vehicle. 
         [0066]      FIG. 4  presents a cross-section, as taken through line  4 - 4  of  FIG. 3 , that gives the predicted values for the recovery of the inlet fluid with the inlet fluid inducer  30  rotating as shown. Note that the expected recovery over the lower portion of the fluid energizing rotor is 96% and over the upper portion 90%. This results in an overall inlet efficiency of 93%. The net result is about a twenty-seven percent improvement in overall waterjet efficiency for a waterjet with the inlet fluid inducer compared to one without. 
         [0067]      FIG. 5  illustrates a proposed version of an inlet fluid inducer  30 , as taken through plane  5 - 5  of  FIG. 3 , that shows one possible means of driving this cylindrical shaped inlet fluid inducer  30 . In this case the drive means consists of a drive motor  43  with power transmitted through a set of right angle gears  44 . The drive motor  43  may be driven electrically, hydraulically, or by other means. 
         [0068]      FIG. 6  presents a cross-section, as taken through line  6 - 6  of  FIG. 3 , that shows a preferred flat hull  39  surface forward to the inlet fluid inducer  30 . Note that the lower surface of the inlet fluid inducer  30  is disposed more into the freestream than surfaces forward of the inlet fluid inducer  30  as shown here. This preferred approach shown here insures optimum performance of the inlet fluid inducer  30  while adding very little additional drag. However, it is to be realized that, while the arrangement shown is preferred, that the instant invention&#39;s inlet fluid inducer  30  can actually be flush with the hull  30  surfaces or even recessed from them and such arrangements are considered within the spirit and scope of the instant invention. 
         [0069]      FIG. 7  presents a partial profile centerline cross-section of a Hydro Air Drive (HAD)  54  with an instant invention inlet fluid inducer  30  applied. There are, ideally, fluid directing means  33 —flaps in this illustration—applied. These flaps  33  are to either side of the shaft  31  in this preferred arrangement of the instant invention. In this  FIG. 7 , the fluid directing means  33  are retracted to their most upward positions with power supplied by actuators  32  which allows water to flow to the entire HAD fluid energizing rotor  35  from top to bottom. This is the preferred position of the fluid directing means  33  for low vehicle speed operation to provide maximum low speed thrust. 
         [0070]    Another item of note in  FIG. 7  is the optional use of low cost and low maintenance labyrinth seals  52  to restrict water from flowing freely around the inlet fluid inducer  30 . While the fluid inlet  55  is shown below the fluid energizing rotor  35  here it is to be realized that it can be fully or partially to the side of or even above the fluid energing rotor  35  as a particular installation may dictate. An optional rudder  36  that provides steering in forward and in reverse is also shown. 
         [0071]      FIG. 8  is the same partial profile centerline cross-section of a HAD  54  as presented in  FIG. 7  but in this case the fluid directing means  33  are extended downward to aid in directing liquid flow to only a portion of the fluid energizing rotor  35 . It is important to note also that a lowered position of the fluid directing means  33  allows gas to pass to the upper portion of the rotor  42  through gas passageways  57  as is indicated by gas flow arrows  38 . As such, the fluid energizing rotor  35  is operating only partially submerged which has advantages compared to standard pressurized system waterjets. Two of these advantages are: 1) The HAD rotor is not subject to cavitation damage since it is aerated and 2) Ingestion of aerated water by the HAD does not result in a severe performance decay it does in the case of a standard pressurized system waterjet. 
         [0072]      FIG. 9  is a cross-sectional plane, as taken through  9 - 9  of  FIG. 7 , that shows the fluid directing means  33  in their retracted position. Note that gas flow is restricted from entering the duct and from reaching the fluid energizing rotor  35  since it is blocked from doing so by the fluid directing means  33 . 
         [0073]      FIG. 10  is a cross-sectional plane, as taken through  10 - 10  of  FIG. 8 , that illustrates how the fluid directing means  33  are positioned during high speed vehicle operation where the fluid energizing rotor  35  is only partially submerged. Note the gas flow arrows  38  that show that gas is passing through in this arrangement. Waterlines  45  either side of the instant invention propulsor  54  are also shown. 
         [0074]      FIG. 11  presents a cross-sectional plane, as taken through line  11 - 11  of  FIG. 7 , that shows the fluid flow distributions, as indicated by fluid energy islands  47 , just forward of the fluid energizing rotor when the fluid directing means are in their retracted position. 
         [0075]      FIG. 12  is a cross-sectional plane, as taken through line  12 - 12  of  FIG. 8 , that illustrates fluid flow distributions, as indicated by fluid energy islands  47 , just forward of the fluid energizing rotor when the fluid directing means are in an extended high vehicle speed position. Note that there is gas above the fluid directing means and liquid below it in this instance. Inlet recovery efficiencies should be in the 98% area over the lower half of the fluid energizing rotor in this instance where the inlet fluid inducer is rotating and adding energy and direction to the incoming fluids. 
         [0076]      FIG. 13  illustrates fluid flow inlet characteristics when the inlet fluid inducer is not rotating. While this is very workable and considered part of the instant invention, performance is substantially better when the inlet fluid inducer is rotating in the direction of the water flow. Expected inlet recoveries should be in about the 80% area in this case with the inlet fluid inducer not rotating. Note also that the waterline  45  is lower than in the case where the inlet fluid inducer is rotating as seen in  FIG. 12  so the fluid energizing rotor would most likely not be receiving as much liquid as the fluid energizing rotor of  FIG. 12 . 
         [0077]      FIG. 14  shows a cross-sectional plane, as taken through line  14 - 14  of  FIG. 13 , that illustrates liquid flow characteristics with the inlet fluid inducer not rotating. Note the lower waterline  45  here than in  FIG. 12 . Also, the expected recovery is 80% while it is 98% in  FIG. 12  where the inlet fluid inducer is rotating in the direction of fluid flow. 
         [0078]      FIG. 15  illustrates flow characteristics around a non-rotating cylinder  48  disposed perpendicular to ideal fluid flow. Note that the flow, indicated by turbulent flow lines  50 , separates around the aft side of the cylinder  48 . 
         [0079]      FIG. 16  shows the same cylinder  48  as that presented in  FIG. 15  but with the cylinder  48  rotating in the direction of flow as is indicated by rotation arrow  49 . It is apparent that the fluid does not detach as is the case of the cylinder  48  that is not rotating of  FIG. 15 . This rotating cylinder  48  makes for a much more efficient and low drag situation than the cylinder  48  that is not rotating of  FIG. 15 . Both  FIGS. 15 and 16  actually show characteristics of the Coanda Effect since the fluid is at least partially attached to the curvilinear surfaces on the aft side of the cylinder  48  and turn inward. 
         [0080]      FIG. 17  shows the same HAD  54  as shown previously; however, in this case the inlet fluid inducer  30  is rotating in an opposite direction to travel and external fluid flow. This has merit in a case where a HAD or waterjet is not operating but the vehicle is still moving forward since this forward direction of rotation of the inlet fluid inducer  30  prevents water from entering the HAD&#39;s inlet  55  thereby reducing drag. 
         [0081]      FIG. 18  presents a centerline profile cross-section plane that shows an alternate method of driving an inlet fluid inducer  30 . In this case the inlet fluid inducer  30  is directly driven by a main drive shaft  31  of the propulsor. Also, this figure shows how an inlet fluid inducer  30  could work when operating in reverse as is the inlet fluid inducer  30  here. Running the inlet fluid inducer  30  in reverse along with reverse operation of the fluid energizing rotor results  35  in enhanced reverse thrust. 
         [0082]      FIG. 19  presents a cross-section plane, as taken through  19 - 19  of  FIG. 18 . Note that the fluid flow directing means  33  are retracted here. 
         [0083]      FIG. 20  is a cross-section plane, as taken through  20 - 20  of  FIG. 18 . The inlet fluid inducer  30  illustrated here is in the form of truncated cones either side of a gear track  46 . Realize that the inlet fluid inducer  30  can take many shapes to accommodate different hull shapes, inlet designs, and the like. 
         [0084]      FIG. 21  is another cross-section plane, as taken through  21 - 21  of  FIG. 18 , that shows an optional elliptical shaped inlet fluid inducer  30 . 
         [0085]      FIG. 22  shows yet another version of an inlet fluid inducer  30  that in this case is made up of two parts. 
         [0086]      FIG. 23  is a partial centerline cross-section plane with a variation of an inlet fluid inducer that incorporates pumping recesses  56  to enhance pumping or fluid accelerating abilities of the inlet fluid inducer  30 . Note that other manners of shape and of possible recesses in the inlet fluid inducer  30  are considered within the spirit and scope of the instant invention. 
         [0087]      FIG. 24  is a cross-section plane, as taken through  24 - 24  of  FIG. 23 , that shows a preferred shape and workings of the inlet fluid inducer  30  variation of  FIG. 23 . 
         [0088]    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.