Apparatus For Water Jet Propulsion

Abstract

Apparatus for water jet propulsion in which a screw propeller is integrally formed with a surrounding duct, which surrounding duct rotates with the screw propeller to eliminate blade-tip vortex. A duct comprised of alternately disposed movable and stationary segments, which movable elements are adjustably positioned to mate with the stationary segments to provide optionally either an intake duct with an optimum configuration to reduce cavitation or a discharge duct with an optimum configuration.

Description

BACKGROUND OF THE INVENTION

The present invention relates in general to apparatus for propelling water vehicles, and more particularly, to apparatus for propelling water vehicles by water-jet propulsion.

Heretofore, screw blades employed for propelling water vehicles were inefficient. Such inefficiency was primarily caused by blade-tip vortex and cavitation. Blade-tip vortex is caused by water passing across the top of fast moving blade-tips, which produces a circular vortex action. This action creates a turbulance and thereby decreases the efficiency of the blade-tips. Cavitation is a formation of small bubbles of water vapor resulting from a decrease of water pressure on the rear side of the rotating screw blades. When the water pressure is reduced to a point equal to or below the vapor pressure of the ambient water, the water vaporizes and forms small bubbles or cavities.

Both blade-tip vortex and cavitation, and particularly cavitation, produce noise which is objectionable. This is particularly so in connection with submarines when a quiet operation is desired.

Attempts have been made to overcome the problems arising out of blade-tip vortex and cavitation. One arrangement has been to surround the blade screw with a duct fitted closely to the tips of the blades to assist in reducing blade-tip vortex. However, there appears to be a need of some clearance between the fast moving blade-tips and the stationary surrounding metal duct. This clearance produces a leakage path which permits a turbulance similar to blade-tip vortex. Fluid passing through a constricted opening under great pressure and at a high velocity is to some extent abrasive. The abrasive action wears away both the blade-tip and surrounding duct, which results in an increase in the clearance. The increase in clearance, in turn, increases the amount of blade-tip turbulance.

Presently existing water-jet apparatus for propelling water vehicles employ an intake duct or a discharge duct with a combined configuration for the intake side and for the discharge side. The combined configuration is a compromise between the optimum shape for an intake duct and the optimum shape for a discharge duct. While such a combined shape is more efficient than attempting to reverse the engines with a unit having an optimum shape for the intake side and an optimum shape for the discharge side, such a unit would provide reduced power when the engines are reversed. Such a configuration, which is sometimes referred to as the "English Curve," is quite inefficient and tends to lack usefulness for a water-jet propulsion system.

SUMMARY OF THE INVENTION

Apparatus for propelling water vehicles by water-jet propulsion, in which a propeller is formed with a surrounding duct fixed thereto. The surrounding duct rotates with the propeller for reducing blade-tip vortex. As a further feature, the drive shaft for the propeller can optionally be set-off from the axis of the hub to increase the effective face area of the propeller.

A duct for water-jet propulsion apparatus having alternately disposed movable and stationary segments, in which the movable segments are adjustably positioned in mating relation with the stationary segments to provide optionally either an optimum configuration as an intake duct to reduce cavitation or an optimum configuration as a discharge duct. An intake duct for water-jet propulsion having a frusto-conical configuration to reduce cavitation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of the apparatus of the present invention for propelling water vehicles by water-jet propulsion.

FIG. 2 is a vertical section of the apparatus shown in FIG. 1 taken along line 2--2 of FIG. 1.

FIG. 3 is an end view of the apparatus shown in FIGS. 1 and 2 taken along the line 3--3 of FIG. 1 at the aft end of the apparatus.

FIG. 4 is an end view of the apparatus shown in FIGS. 1 and 2 taken along the line 4--4 of FIG. 1 at the forward end of the apparatus.

FIG. 5 is a vertical section view taken along line 5--5 of FIG. 2.

FIG. 6 is a section taken along line 6--6 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated in FIGS. 1-5 is a twin water jet propulsion apparatus 9 embodying the present invention, which comprises identical water jet propulsion apparatus 10 and 10a. Hence, the water jet propulsion apparatus 10 will be described in detail hereinafter and like parts for the water jet propulsion apparatus 10a will be designated by the same reference numeral but with a suffix "a."

The water jet propulsion apparatus 10 (FIG. 2) comprises ducts 15 and 20 at opposite ends thereof. Joining the confronting ends of the ducts 15 and 20 is a screw propeller 25 which is disposed within a cylindrical housing 30. Rotating the screw propellers 25 and 25a is a common drive arrangement 35 (FIGS. 4 and 5).

Either duct 15 or duct 20 can be adjustably employed as the intake duct or as the discharge duct. For purposes of convenience, in the description to follow the duct 15 will be described as the intake duct and the duct 20 will be described as the discharge duct.

The intake duct 15 in the preferred embodiment has a configuration of a truncated cone to reduce cavitation and comprises 16 segments. Segments 50-57 are movable segments and segments 60-67 are stationary segments. The movable segments 50-57 and the fixed segments 60-67 are alternately disposed to form the periphery wall of the duct 15. The stationary segments are fixed at proximal ends thereof to the housing 30 (FIG. 2). The movable segments are pivotally connected at their proximal ends to the housing 30. In the exemplary embodiment for the intake duct 15, the movable segments 50-57 are extended angularly relative to the housing 30 and mate with the fixed segments 60-67 (FIG. 3) to form a relatively smooth inner frusto-conical wall for the path of travel of water advancing toward the propeller screw 25, which may be referred to as the optimum configuration of an intake duct. Thus, as an intake duct, the movable segments fan out angularly relative to the housing 30 to mate with the stationary segments.

In a like manner, the discharge duct 20 includes 16 segments. In the exemplary embodiment, the discharge duct 20 has a cylindrical configuration formed by eight movable segments 70-77, which are retracted angularly relative to the housing 30 to mate with adjacent movable segments thereof for the discharge of water expelled by the propeller screw 25. This configuration may be referred to as the optimum configuration for a discharge duct. The movable segments are pivotally connected to the proximal ends thereof to the housing 30 (FIG. 2) and the stationary segments are fixed at their proximal ends to the housing 30. When the movable segments are retracted angularly relative to the housing 30, they form the inner cylindrical wall of the duct 20 for the discharge flow of the water (FIG. 4).

Connected to the movable segments 50-57 for the duct 15 are angular actuating arms 90-97, respectively. Each arm has one leg thereof fixed to its associated movable segment for imparting an angularly extending or retracting movement thereto relative to the housing 30. At the junction between the legs, the actuating arms 90-97 are pivotally connected for pivotal movement to the housing 30 by means of suitable ears and pins. Mounted on the housing 30 are suitable hydraulic cylinders 100-107. Pistons 110-117 are disposed within the cylinders 100-107, respectively, and are connected through their piston rods to the other legs of the arms 90-97, respectively, for imparting thereto a pivotal movement. Thus, imparting rectilinear movement to the pistons 110-117 causes the actuating arms 90-97, respectively, to extend or retract the movable segments 50-57, respectively, of the duct 15 angularly relative to the housing 30.

In a like manner, connected to the movable segments 70-77 for the duct 20 are angular actuating arms 120-127, respectively. Each arm has one leg thereof fixed to its associated movable segment for imparting an extending or retracting angular movement thereto relative to the housing 30. At the junction between the legs, the actuating arms 120-127 are pivotally connected for pivotal movement to the housing 30 by means of suitable ears and pins. Pistons 130-137 are disposed within the cylinders 100-107, respectively, and are connected through their piston rods to the other legs of the arms 120-127, respectively. The pistons 130-137 are oppositely located in the cylinders 100-107, respectively, with respect to the pistons 110-117. Intermediate the pistons 130-137 and pistons 110-117 are sealing plugs 140-147, respectively.

For actuating the pistons 110-117 and the pistons 130-137 within the cylinders 100-107 to impart a reciprocating movement thereto, fluid under pressure is supplied to each side of the hydraulic cylinders 100-107. Toward this end, a network of hydraulic supply conduits 140 and a network of hydraulic return conduits 145 supply positive fluid pressure to each end of each side of the cylinders 100-107. A suitable source of fluid under pressure, not shown, is connected to the network 140 and 145. The hydraulic supply conduits 140 are connected to the lowest pressure point in each side of the hydraulic 100-107 and the hydraulic return conduits 145 are connected to the highest pressure point in each side of the hydraulic cylinders 100-107, whereby positive fluid pressure is alternately applied to each end of each side of the hydraulic cylinders 100-107 while the return network is opened to permit fluid on the other end of each side of the hydraulic cylinders 100-107 to be evacuated. An automatic bleed arrangement is provided, since any entraped air will rise and will be entraped to be carried out with the fluid in its exhaust cycle. Conventional O-rings 146 are provided as fluid seals for the hydraulic system.

For limiting the angular extent of movement of the movable segments 50-57 for the duct 15 so as to enable the movable segments 50-57 and the fixed segments 60-67 to mate properly in the intake adjusted position or the discharge adjusted position, adjustment screws 150-157 are mounted on the arms 90-97, respectively. The screws 150-157 adjustably engage the housing 30 to limit the angular extent of travel of the associated actuater arm and permit adjustment thereof for proper mating of the movable segments 50-57 with the fixed segments 60-61. Adjustment screws 160-167 on the cylinders 100-107, respectively, limit the linear extent of travel of the pistons 110-117, respectively, and permit adjustment thereof for proper mating of the movable segments 50-57 in the discharge mode for the duct 15.

Similarly, adjustment screws similar to adjustment screw 170 for the actuating arm 120 are adjustably mounted on the actuating arms 121-127, respectively, for engagement with the housing 30 to limit the angular extent of the movable segments 70-77 for the duct 20 so as to enable the movable segments 70-77 to properly mate in the intake adjusted position or the discharge adjusted position with the stationary segments 80-87. The adjustment screws, which are similar to the adjustment screws 150-157 previously described, limit the movement of the movable segments 70-77 by restricting the angular extent of the pivotal movement of the actuating arms 120-127 toward the housing 30. Adjustment screws, not shown, on the cylinders 100-107, respectively, similar to the adjustment screws 160-167, limit the linear extent of the travel of the pistons 130-137, respectively, and permit adjustment thereof for proper mating of the movable segments 70-77 in the discharge mode of the duct 20.

From the foregoing, it is to be observed that the duct 15 is selectively formed into the shape of a truncated cone and functions in this mode as the intake duct. Water enters the wide end of the duct 15 and impinges on the sloping inner walls of the duct 15. This action creates a pressure head which is converted into a velocity head as the water advances toward the screw propeller 25. The duct 15 gradually decreases in cross-sectional areas in the downstream direction. As the water proceeds through the screw propeller 25, it is accelerated and discharged through the cylindrical shape which is the exemplary configuration for a discharge duct.

Disposed within the housing 30 in the path of travel of water advancing through the duct 15 is the screw propeller 25. The screw propeller 25 comprises a hub 180 which extends in the direction of travel of the water from the duct 15 toward the duct 20. Fixed to the hub or core 180 are screw blades 181-185. As is well-known, the hub 180 rotates fitted with radiating blades 181-185, which are arranged in a spiral configuration. The hub 180 is smaller than the inner core of conventional or shaft driven screw propellers.

According to the present invention, a cylindrical tube, sleeve, duct or collar 190 is fixed to the distal ends of the screw blades 181-185 for rotation therewith. The duct 190 may be integrally formed with the distal ends of the blades 181-185 or welded thereto. Suitable bearings, such as roller bearings 191, are disposed between the rotating duct 190 and the housing 30, which serve as thrust bearings as well as anti-friction bearings.

Integrally formed with the duct 190 is a driven gear 195 for imparting rotation to the screw propeller 25 and the surrounding duct 190. Meshing with the gears 195 and 195a is a centrally located drive gear 196 (FIG. 5), which is keyed to a drive shaft 197 of the vehicle. O-rings 198 seal off the gear box to reduce the seepage of water thereinto and to reduce the escape of gear lubricant into the water.

By virtue of the duct 190 being fixed to the distal ends of the screw blades 181-185 for rotation therewith and by eliminating clearance between the tip of the screw blades and the duct surrounding the screw propeller, blade-tip turbulance is substantially eliminated.

The cavitation is substantially reduced by increasing the pressure on the back side of the screw blades 181-185, which is achieved by the acceleration of intake water in the frusto-conically shaped intake duct of the present invention.

Claims

I claim:

1. A duct for fluid jet propulsion apparatus comprising:

a housing;

a plurality of movable segments pivotally connected to said housing;

a plurality of stationary segments fixed to said housing;

said movable segments and said stationary segments being alternately disposed and in adjacent relation about said housing; and

means connected to said movable segments for pivoting said movable segments relative to said housing into selective mated positions with adjacent segments for at times forming a desired configuration as an intake duct and at other times forming a desired configuration as a discharge duct,

said movable segments fan out pivotally from said housing into angular expansion for mating relation with said stationary segments to form a desired configuration as an intake duct.

2. A duct as claimed in claim 1 wherein said movable segments are retracted angularly with respect to said housing for mating relation with adjacent movable segments to form a desired configuration as a discharge duct.

3. A duct as claimed in claim 2 wherein said means includes an hydraulic system.

4. A duct as claimed in claim 3 and comprising adjustment means for restricting the extent of movement of said movable segments.