US3662702A

US3662702A - Multiple propeller ducted system

Info

Publication number: US3662702A
Application number: US46779A
Authority: US
Inventors: David John Doust
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-06-16
Filing date: 1970-06-16
Publication date: 1972-05-16
Anticipated expiration: 1989-05-16

Abstract

A ducted propulsion system for waterborne, semi-submerged or fully submerged vessels comprising a ducted system having two or more intake ducts which open below the mid depth of the vessel, and which merge into a specially shaped non-circular composite duct which generally extends in the fore and aft direction of the vessel. Propeller means are mounted independently in the composite duct and adapted to induce a flow of water through the system of ducts to propel said vessel. The propeller means comprise two or more propellers or impellers each having its own independent shafting, bearings and supporting structure.

Description

United States Patent Doust [451 May 16, 1972 [54] MULTIPLE PROPELLER DUCTED SYSTEM [72] Inventor: David John Doust, 276 St. James St. W.,

FOREIGN PATENTS OR APPLICATIONS 1,112,686 3/1956 France ..l15/l6 287,253 7/1931 Italy ..1l5/39 Primary Examiner-Milton Buchler Assistant ExaminerCarl A. Rutledge Attorney-Jerry B. Cesak [57] ABSTRACT A ducted propulsion system for waterborne, semi-submerged or fully submerged vessels comprising a ducted system having two or more intake ducts which open below the mid depth of the vessel, and which merge into a specially shaped non-circular composite duct which generally extends in the fore and aft direction of the vessel. Propeller means are mounted independently in the composite duct and adapted to induce a flow of water through the system of ducts to propel said vessel. The propeller means comprise two or more propellers or impellers each having its own independent shafting, bearings and supporting structure.

18 Claims, 27 Drawing Figures PATENTEDHAY 16 m2 SHEET 1 [IF 9 FIG. 1

INVENTOR I 3 David John DOUST PA TEN (JIL'N TS PHE'NTEDMAHSM 3.662.702

SHEETEUFQ INVENTOR David John DUUST imwv PA T AGENTS P'A'TENTEBHAY 16 m2 SHEET 3 OF 9 PATENTEDMAY 16 m2 SHEET k 0F 9 HAPELLER t SECrIoN INVENTOR David John DOUST 7m 7 PAT T AGENTS PRTENTEUMAY 1s m:

SHEET 5 [1F 9 MF'ELLER SECTlO MEQ IN DIFFUSE R SECTION t VESSEL INVENTOR David John DOUST jmv fia 4X PATENT AGENTS INVENTOR David John DOUST PA'TE'N'TEDnmsm 3.662.702

SHEET 8 BF 9 DlFFUSER 'SEC'TKDN INVENTOR David John DOUST AT AGENTS PATENTEDMHBM: 3.662.702

SHEET 9 OF 9 INVENTOR David John DOUST PATE T AGENTS MULTIPLE PROPELLER DUCTED SYSTEM This invention relates to a new and improved propulsion and steering apparatus for use with waterborne, semi-submerged or fully submerged vessels.

Conventional propellers working outside of a ships hull can be adversely affected by the following factors:

a. Breakdown of flow into the propeller or propellers, especially in the case of full-bodied vessels such as tankers, ore and bulk carriers;

b. Vibration of the hull structure due to propeller-excited pulsations arising from the flow irregularities exaggerated by item (a);

c. Loss of propulsive efficiency at high thrust loadings, rates of rotation and input shaft powers which physically restrict the speed performance of large vessels and largely determine the choice between single, twin or multiple combinations;

d. Loss of manoeuvrability and rudder action due to the blanking effect of the after body shape on the flow into the rudders;

e. Loss of stopping ability and reverse propeller thrust on the vessel, making the problem of stopping and taking avoiding action very difficult in the case of super-tankers and other large vessels;

f. Liability of damage to propeller or propellers working outside the confines of the hull surface, due to contact by ice, floating hazards or other vessels.

According to the present invention, there is provided a ducted propulsion system for waterborne, semi-submerged or fully submerged vessels comprising a ducted system having two or more intake ducts which open below the mid depth of the vessel, and which merge into a specially shaped non-circular composite duct which generally extends in the fore and aft direction of the vessel, propeller means mounted independently in said composite duct and adapted to induce a flow of water through said system of ducts to propel said vessel, said propeller means comprising two or more propellers or impellers each with its own independent shafting, bearings and supporting structure.

By fitting such a series of two or more propellers or impellers, longitudinally spaced along the composite duct, it is possible to increase the total power absorption of the overall propulsion system without the attendant disadvantages of multi-conventional propeller systems exposed outside of the hull surface of the vessel.

Due to the configuration of the composite duct, it is also possible to provide for power absorption from the main propulsion machinery in excess of that which can be absorbed by a single propeller working in a circular duct, thus resulting in increased thrust available for propulsion of the vessel.

The mechanical complications of co-axially mounted, contra-rotating propellers are also largely overcome by driving the multi-stage series of propellers independently and mounting them non-coaxially in the composite duct.

The invention will be further described by way of example only with reference to the embodiments illustrated in the accompanying drawings, wherein:

FIG. I is a schematic drawing of the duct system;

FIG. 2 is a sectional detail view of the inlet section of the duct;

FIG. 3 is a sectional detail view of the inlet grid;

FIG. 4 is a sectional detail plan view of the inlet fairing;

FIG. 5 is a sectional view on the line 5-5 of FIG. 4;

FIG. 6 is a sectional detail plan view of the valve section of the duct;

FIG. 7 is a sectional view on the line 7-7 of FIG. 6;

FIG. 8 is a sectional detail plan view of the transition section of the duct;

FIG. 9 is a series of section views on the line V-V, W-W and X-X ofFIG. 8;

FIG. 10 is a sectional detail plan view of the merging section of the duct;

FIG. 11 is a sectional view on the line 11-11 of FIG. 10;

FIG. 12 is an isometric view of the merging section;

FIG. 13 is a sectional plan view of the impeller section of the duct;

FIG. 14 is a detail of the shaft support;

FIG. 15 is a sectional view on the line 15-15 of FIG. 13;

FIG. 16 is a sectional plan view of a modified impeller section of the duct;

FIG. 17 is a detail of the shaft supporters;

FIG. 18 is a sectional view on the line 18-18 of FIG. 16;

FIG. 19 is a sectional view on the line 19-19 of FIG. 16;

FIG. 20 is a sectional plan view of the diffuser section;

FIG. 21 is a series of sectional views on the lines P-P, Q- Q and T-T of FIG. 20;

FIG. 22 is a sectional plan view of the rudder section;

FIG. 23 is a sectional view on the line 23-23 of FIG. 22;

FIG. 24 is a detail view of the exit grid bars;

FIG. 25, 26 & 27 illustrate various methods of noise and vibration attenuation.

Referring to the drawings, a vessel 11 is provided with a ducted propulsion system comprising two intake ducts 12 opening from the sides of the vessel and extending inwards and aft to merge into a common composite duct 13 the exit end of which opens into a rudder section or expansion nozzle 14. A third intake duct opening from the bottom of the vessel may be provided if desired; however, such a duct is not shown in the drawings.

Each intake duct is of non-circular cross-section with special triangulated recessing provided at their after extremities to avoid high entry hydraulic losses in the overall system. Each of the intake ducts 12 is also provided with conventional flow restricting means of substantially rectangular cross-section, to vary the effective flow of water, through said ducts by varying the cross-sectional area of the ducts.

In order to increase the permissible power input to a particular vessel and without the complication of conventional multiple/twin-screw shafts (A-bossings) exposed outside of the ship surface, two or more impellers may be mounted noncoaxially mounted within the common duct 13. Note that with the composite duct system indicated, impeller clearances are much less critical than for a regular duct and concentric coaxial impeller, and produces improvements in propulsion efficiency of between 5 and 10 percent relative to a single impeller.

The propellers are mounted in the mid portion of the composite duct 13, these propellers are spaced longitudinally at intervals in the duct. 7

Each propeller or impeller is separately mounted on a shaft and may be driven independently or through a common gear box or propulsion motor, depending on the particular application of the system. I

Greatly increased lateral control of the vessel when going astern is achieved by throttling the flow in either of the Y-intake ducts 12. This can be further improved by the use of controlled pitch impellers.

FIG. 1 is a diagrammatic layout of the ducted propulsion system or as it is called the YPASS Propulsion System". The various sections are designated in FIG. 1 as follows:

Section A Inlet Section Section B Valve Section Section C Transition Section Section D" Merging Section Section E" Impeller Section Section F Diffuser Section Section G" Rudder Section Each of these sections is described separately.

INLET SECTION The duct inlet is illustrated in FIG. 2. The width of the duct is shown as a. Inlet grids 14 are spaced across the front of the inlet 15. These grids protect the inlet ducts from ice or submerged objects. Details of the cross-section of the grids are shown in FIG. 3. It has been found that to avoid high frictional losses the width b of the triangular grid preferably is from about 0.l inches to about 0.1a and the spacing between the grid bars is preferably from about 0.1a to about a.

It has been determined that conic development recesses give the minimum friction entry losses into such a system. The angle of entry at of the recessed cone fairing 16 which is shown in FIGS. 2 and 4 may vary from about to about 60 with the optimum angle varying from about to 40 depending on the local lines of the vessel in way of the ducted inlet. A good average design value appears to be about 30 for a vessel of average after body fullness. The dimension d which is the depth of the inlet fairing 16 may vary from about 0 to about 0.5a. FIG. 5 illustrates the cross-section of the inlet fairing l6 taken on the line 5-5 on FIG. 4.

VALVE SECTION The valve section of the duct is illustrated in FIG. 6. The valve 17 is shown in the open position in full lines and in the closed position in broken lines. FIG. 7 is a detail of the valve 17 and shows the valve mounted on a shaft 18 which is sup ported from above. The valve 17 could, of course, be mounted on a shaft passing through the duct to give a top and bottom support for the valve. This can be done as desired. If desired, the corners of the duct can be rounded. The value of e which is the radius of the corners of the duct in the valve section should be selected to be in the range of from about 0 to less than 0.5 V a -l'h where a is the width of the duct and h is the height of the duct at the valve section.

TRANSITION SECTION The transition section of the duct which is located between the valve section and the merging section is illustrated in FIGS. 8 and 9. It has been found advantageous in order to efficiently control the flow of water without causing choking at the intersection to limit the radius j of the corner of this section by the following formula:

The length transition section L is greater than the width of the duct a".

FIG. 9 shows the manner which the cross'section of the transition section changes from a more or less rectangular section at x to a section which has a flat surface on one side and a semi-circular surface at the other. At the point at which the transition section joins the valve section, at line XX, the cross-section of the duct is rectangular with the corner radius being equal to e which was defined above. Moving along the transition section the surface of the duct on the inside or on the Y-side does not change. In other words, it remains flat with small radius corners. The surface of the duct on the outside of the Y gradually changes into a curved section, the radius of which is determined by the formula given above. At the point at which the transition section joins the merging section, the outer surface of the duct is semi-circular.

MERGING SECTION The merging section in which the two separate inlet ducts l2 merge into a common duct 13 is illustrated in FIGS. 10, 11 and 12. The ratio of the area of the inlet ducts in relation to the area of the common ducts is dependent of the speed of advance of the vessel, its size and shape. Generally, it has been found that the width of the common duct w should be greater than a, the width of the single duct. In addition, it has also been found that the cross-sectional area of the composite duct must not be greater than the combined cross-sectional areas of the inlet ducts.

For optimum results, the angle 13" which is the angle that the center line of the separate inlet ducts makes with the center line of the vessel, should be selected to be in the range of from about to about 60. The width of the joining piece It between the two ducts, should be equal to or less than w", the width of the common duct. This joining piece 39 is a watertight structural member which is flat to simplify mounting of the impeller shaft stuffing boxes and bearings. A fairing piece 40 which need not be watertight is located aft of the joining piece 39 to streamline the flow of water through the ducts.

IMPELLER SECTION The impeller section is shown in FIGS. 13 to 19. FIG. 13 is a plan view of an impeller section in which there are located two impellers 20. The impellers may be staggered one in front of the other as is shown or they may be mounted side by side. Each impeller is driven by its own independent shaft. The shafts are supported on shaft supports 21 which are shown-in detail in FIG. 14. The impellers 20 would normally be operated so that the impellers were contra-rotating and were out of phase with each other. The clearance which has been found on these very large impellers is surprisingly little and a maximum of 3 inches has been found to be required. Usually considerably less than this is needed.

To reduce the wear of the walls of the duct, wear inserts 22 are inserted into the walls of the duct at those places at which the propellers come close to the walls and at which wear would normally be quite high. 7

It has been found that the number of blades in the propeller can be varied considerably depending on the type of vessel in which the ducted propulsion system is used. Usually, the number of blades varies from about three to seven.

FIG. 16 illustrates an impeller section in which there are three impellers 23, each mounted on its own independent drive shaft. In this case, the impellers are staggered so that two are along side of one another and the center one is placed forward of the other two. I

In such an arrangement, the shaft supports 24, which are illustrated in FIG. 17, would normally be located above and below the shaft. Wear inserts 25 may be fitted about the periphery of the duct in line with the impellers which are located in a side-by-side arrangement. Additional wear inserts 26 may be located at the top and bottom of the duct as is illustrated in FIG. 18 at the point at which the forward impeller approaches the surface of the duct.

FIG. 19 shows the arrangement of the three impellers two of which operate in a clockwise direction and the third impeller operates in a counter-clockwise direction. The propellers are mounted on the shaft so that they are out of phase with each other.

The cross-section of the duct in the impeller section is illustrated in FIG. 19. The two side walls'are semi-circular to fit the contour of the impellers or propellers mounted within them. The top and bottom surfaces are flat.

DIFFUSER SECTION FIGS. 20 and 21 show the diffuser section and illustrate how the duct cross-section varies at this section. The side walls of the duct in the impeller section are semi-circular and the top and bottom walls are flat. In the difiuser section the cross-section becomes rectangular. At the start of the diffuser section the radius in the corners is h/2 where h is the height of the duct. At the end of the ditfuser section, the cross-section of the duct is rectangular. The radius at the corners gradually changes and is determined by the formula x (h/2) (u/H) where h is the length of the diffuser section and 14" is the distance from the end of the diffuser section to the point at which the radius is to be calculated. The length of the diffuser section is shown as H.

RUDDER SECTION dem rudder arrangement is further increased by the use of controlled pitch impellers. The cross-section at the rudder section is shown in FIG. 23 and is rectangular.

A series of grids are spaced across the aft end of the duct to protect the rudders. Details of the grid bars are given in FIG. 24. The number of rudders used varies greatly again with the type of vessel. It is envisaged that anywhere from two to rudders can be used to advantage.

NOISE AND VIBRATION ATTENUATION The ducted propulsion system of the present invention can be modified to modulate the noise emission external to the ship. Various ways of doing this are shown in FIGS. 25, 26 and 27.

FIG. 25 illustrates one method by which noise and vibration may be controlled. The left-hand side of the figure is a crosssection of the ship with the hull 32 being shown and the duct wall 33. The right-hand part of the drawing is a longitudinal cross-section and the transverse members 35 are shown. Damping material 36 can be adherred to the exterior surface of the duct walls 33 in order to reduce the noise and vibration.

FIG. 26 again shows a cross-section of the duct, the lefthand side of the drawing being a section across of the ship and the right-hand side of the drawing being a longitudinal crosssection. Acoustic absorptive material 37 is adherred to the exterior wall of the duct 33, the hull 32 and the transverse members 35 to provide noise and vibration control.

FIG. 27 illustrates the use of acoustic insulation. In this case, the void between the hull 32 and the duct 33 is filled with acoustic insulation 18 again to reduce noise and vibration.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A ducted propulsion system for waterborne, semisubmerged or fully submerged vessels comprising a duct system having two or more intake ducts which open below the mid depth of the vessel and which merge into a composite duct generally extending in the fore and aft direction of said vessel, each of said inlet ducts consisting of:

an Inlet Section a Valve Section, and a Transition Section said inlet section having a recessed cone fairing at its after end which makes an angle of less than 60 with the hull, and a plurality of grids spaced across the inlet,

said valve section having a valve adapted to throttle, the

flow of water through said inlet duct and said transition section having a cross-section which gradually changes from the cross-section of the valve section to the cross-section of the merging section,

said inlet ducts join together to form a single composite duct at the merging section, the angle between said separate inlet ducts and the center line of the ship being in the range of from about to about 60 said composite duct consisting of an impeller section in which there is mounted propeller means adapted to induce a flow of water in said duct system, said propeller means comprising two or more propellers or impellers each having its own independent shafting bearing and supporting structure, the side walls of the duct forming said impeller section being semi-circular and the top and bottom being flat a diffuser section in which the cross-section of the duct changes gradually from that of the impeller section to a rectangular cross-section and a rudder section having a rectangular cross-section adapted to house a plurality of rudders and a series of grids spaced across the aft end of said duct.

2. The ducted propulsion system as claimed in claim 1 having two inlet ducts which open from the sides of the vessel.

3. The ducted propulsion system as claimed in claim 1 in which there are three inlet ducts, two opening from the sides of the vessel and one opening from the bottom of the vessel.

4. The ducted propulsion system as claimed in claim I in which the cross-sectional area of of the composite duct is not greater than the combined cross-sectional areas of said inlet ducts.

5. The ducted propulsion system as claimed in claim 1 in which said recess cone fairing makes an angle of between 10 and 40 with the hull.

6. The ducted propulsion system as claimed in claim 1 in which there are two impellers mounted in a side-by-side relationship.

7. The ducted propulsion system as claimed in claim 1 in which there are two impellers which are mounted one in front of the other in a staggered relationship.

8. The ducted propulsion system as claimed in claim 1 in which there are three impellers, two of which are mounted along side of each other and the third is mounted between the other two and out of line with them.

9. The ducted propulsion system as claimed in claim 1 in which the impellers are contra-rotating.

10. The ducted propulsion system as claimed in claim 1 in which the number of rudders is from two to ten.

11. The ducted propulsion system as claimed in claim 1 in which sound and vibration absorptive material is placed about the ducts to modulate noise emission.

12. A ducted propulsion system for waterborne, semi-submerged or fully submerged vessels comprising a duct system having at least two intake ducts which open below the mid depth at the sides of the vessel and merge into a composite duct extending toward the stern, each of said inlet ducts including an inlet section, a valve section and a transition section, a valve in said valve section adapted to throttle the flow of water through the inlet duct, said transition section having a cross-section which gradually changes from that of the valve section to that of the merging section, and inlet ducts joining together to form a single composite duct at the merging section, said composite duct including an impeller section, a diffuser section and a rudder section, propeller means provided in said impeller section and including at least two propellers for inducing a flow of water through the duct system, said diffuser section having a cross-section which gradually changes from that of the impeller section to that of the rudder section, and a plurality of rudders provided in the rudder section.

13. The ducted propulsion system as claimed in claim 12 in which the cross-sectional area of the composite duct is not greater than the combined cross-sectional areas of said inlet ducts.

14. The ducted propulsion system as claimed in claim 12 in which the two propellers are disposed in a side by side relationship in said impeller section.

15. The ducted propulsion system as claimed in claim 12 in which the two propellers are mounted one in front of the other in a staggered relationship.

16. The ducted propulsion system as claimed in claim 12 in which there are three propellers in said impeller section, two of the propellers being disposed in a side by side relationship and the third being disposed between the other two and out of line with them.

17. The ducted propulsion system as claimed in claim 12 in which said propellers are contra-rotating.

18. The ducted propulsion system as claimed in claim 12 together with sound and vibration absorptive material placed about the ducts to modulate noise emission.

Claims

1. A ducted propulsion system for waterborne, semisubmerged or fully submerged vessels comprising a duct system having two or more intake ducts which open below the mid depth of the vessel and which merge into a composite duct generally extending in the fore and aft direction of said vessel, each of said inlet ducts consisting of: an Inlet Section a Valve Section, and a Transition Section said inlet section having a recessed cone fairing at its after end which makes an angle of less than 60* with the hull, and a plurality of grids spaced across the inlet, said valve section having a valve adapted to throttle, the flow of water through said inlet duct and said transition section having a cross-section which gradually changes from the cross-section of the valve section to the cross-section of the merging section, said inlet ducts join together to form a single composite duct at the merging section, the angle between said separate inlet ducts and the center line of the ship being in the range of from about 20* to about 60* said composite duct consisting of an impeller section in which there is mounted propeller means adapted to induce a flow of water in said duct system, said propeller means comprising two or More propellers or impellers each having its own independent shafting bearing and supporting structure, the side walls of the duct forming said impeller section being semi-circular and the top and bottom being flat a diffuser section in which the cross-section of the duct changes gradually from that of the impeller section to a rectangular cross-section and a rudder section having a rectangular cross-section adapted to house a plurality of rudders and a series of grids spaced across the aft end of said duct.

4. The ducted propulsion system as claimed in claim 1 in which the cross-sectional area of of the composite duct is not greater than the combined cross-sectional areas of said inlet ducts.

5. The ducted propulsion system as claimed in claim 1 in which said recess cone fairing makes an angle of between 10* and 40* with the hull.