GB2489551A - Drag-reducing arrangement for marine vessels - Google Patents

Abstract

A drag reducing arrangement comprises a vortex generating rotor cone 80 having twisted ducts formed in its outer surface and a channel ducted stator means 81. The channel ducted stator means is provided with vanes 82 that define longitudinal channels that receive the vortex produced by the rotor cone and forms a series of drag reducing counter rotating vortex ring pairs (15, Fig 1). The arrangement can be used in a marine propulsion system (Figure 1) to reduce the turbulent drag of known propeller drive systems. It can also be used as a propulsor pod system (Figure 5) for use on a large vessel, for locating within a modified bow bulb to reduce drag and increase fuel efficiency. The arrangement can also be used for locating both fore and aft in a fully submersible vessel (Figure 6) as an inboard system to increase stealth and reduce drag respectively.

Description

Marine Drag-Reducing propulsion System.

The following invention relates to a hull drag-reducing marine propulsion system suitable for deploying across a range of existing and new marine vessels and roles.

Conventional stem-mounted ships propulsion systems comprising propellers or ducted fans do not reduce hull drag except partially at specific speeds. With the cost of fuel escalating, the requirement and overheads for adopting effective and economical hull drag reduction countermeasures become commercially feasible.

Hull drag is related to the surface area of the hull exposed to water in flow, hull length and speed combinations and to a lesser extent hydrodynamic shape and boundary layer turbulence-creating surface texture or roughness as presented to flow. The larger the cross-section presented to flow and the less streamlined the hull, the greater the volume of water displaced in flow each second and hence the greater the thrust required to overcome drag.

Increasing the ship's dead weight causes it to lie lower in the water and hence increases hull drag from increased said hull surface area exposed to flow. Conversely a hydrofoil hull lifts itself out of the water to reduce the surface area exposed to drag, but this requires high start-up speed and power. Such systems can not operate with heavy loads in rough seas, where lower buoyancy is required to reduce hull slamming, passenger discomfort and hull stresses. Modem ships therefore operate in a highly buoyant mode to reduce drag which causes increased hull slamming and stresses especially in rough seas, reducing ships operational life.

Adopting a ships bow bulb increases the effective hull length to reduce pitching in waves and said hull slamming whilst presenting a submersible streamlined shape to divert flow thereby reducing drag before it passes over the bows, changing the ship's optimal operating speed and efficiency characteristics whilst retaining high buoyancy.

A low drag, low buoyancy high propulsion system is therefore required that has high power-density, ruggedness, drag-reduction, stealth and is economical to retro-fit.

A vortex-creating resonant-turbulent boundary layer is one solution that can be streamed along the hull from the bows to reduce drag when operating in semi-submersible mode with increased payloads. Fish, aquatic mammals in water and golf balls in air present scaled, dynamic and dimpled surfaces to flow also making use of boundary layer vortex generation and to reduce wake, equivalent to the stem wave'.

A marine hull drag-reducing vortex-streaming bow-bulb based propulsion system has been published before by the Author, but it required a complex array of moving vanes which were expensive to produce, required powering and were prone to damage.

Additionally, fish cart flex their bodies and vary the roughness of their scales to enhance the effect creating larger scale vortices accompanying and assisting their movement through water, making the vortex streaming an active rather than passive process, integral to, rather than remoted from, motive power generation in water.

According to the present invention there is provided: -A drag-reducing marine propulsion system comprising one or more: -raised pitch flow-scanning vortex-generating ducted-channel rotor cones typically of 60-75 degrees ducted-channel angle rotating freely and or power assisted in flow, located axially on a flow-chaunel-ducted vortex bisector cone stator, with a leading or trailing ductcd powered impeller propeller or fan flow-compressing propulsor of normal pitch typically of 30-45 degrees blade angle, located axially within a manifold.

The Invention comprises three Embodiments: - 1. A compact ducted vortex ring-blowing stern vectored propulsion system, deployable as one or more outboards and or propulsor pods on floating marine vessels of different sizes, 2. A drag-reducing bows and or bow bulb-located vortex streaming drag reducIng system suitable for deployment on large floating and or semi-submersible marine vessels, 3. A combined bows and stem drag-reducing'stealthy propulsion system suitable for deployment on fully-submersible marine vessels of different sizes.

The Invention will be described according to the Following Figures: -Figure 1 shows the First Embodiment in sectional elevation, deployed on a launch as an outboard stem or alternatively as a vectored propulsor pod propulsion system, Figure 2 shows in detailed front elevation the ducted-channelled, vortex-generating rotor cone design, common to all three EmbOdiments, located in front of the trailing ducted-channelled stator cone, with the ducting partially omitted, Figures 3a and 3b show the Second Embodiment in sectional plan and front elevations the propulsion system's rotor cone in-situ, located in front of the trailing flow-channelled vortex bisector cone comprising the bow-bulb and hull, with external bisected vortex hull streaming and internal streaming for vectored bow-thrusting and propulsion, Figure 4 shows in elevation the external vortex bisection and streaming hull drag reduction principle of operation operating with a conventional stem propulsion system, Figure 5 shows in sectional plan view further detail of the internal flow management and routing via a turbine with external exhaust manifold diverting and deflecting flow proud of and ahead the bows, Figure 6 shows in plan view the third embodiment: the combined vortex ring-blowing inboard propulsion and vortex-streaming boundary layer drag reduction system with a fully submersible hull (submarine) travelling through ambient water, with recombinant stealthy' wake vortex cancelling, Figure 7 shows in plan view the bow wave-packetizing, vortex-streaming principle of hull drag-reduction.

The First Embodiment of The Invention will now be described with reference to the following Figures: -Referring to Fig. 1; the small marine vessel 10, e.g. a launch, has a high-powered outboard motor 16 powering said compact ducted propulsor system or propulsor pod with a leading stage ducted fan impeller or propeller compressor 11, mid-stage ducted vortex-scanning generator cone 12 and trailing-stage ducted vortex bisector stator cone 14. Bisected counter-rotating vortex ring pairs 15 are shown being blown aft, creating powerful thrust due to their dispersion-resistant properties. The ducting 17 is shown extending over the rotor forming the manifold.

Referring to Figure 2: -the vortex-generating rotor cone 80, is located in manifold flow in front of the trailing streaming vortex bisector stator cone 81. The vortex bisector stator cone is ducted channel-ribbed 81 82, and these channel ribs extend rearwards as hydrofoils to direct said generated vortex streams along the bows length of the hull in flow in the boundary layer to prevent dispersal and reduce drag. As the cone rotates passively in flow, water is drawn into opposite successive sides of the vortex generator rotor cone impeller inlets and directed to alternating sided outlets 84 85. This water is spun outwards and backwards and channelled, by centripetal rotor forces causing rotating flow to be ejected over alternate internal 85 and external 84 faces of the trailing vortex bisector rotor cone. The vortex streams produced are raster-scanned', building up a repeating streaming pattern to produce counter-rotating streaming pairs of concentric vortex rings, the outer ring which advantageously provides a vertical boundary layer resonant flow enhancement thereby eliminating hull surface friction and hence drag.

The rotation and fragmentation of rotor inlet flow spun into said ducted channels as described packetizes the flow, eliminating the bow and shock waves before they form.

The Second Embodiment of The Invention will now be described with reference to the following Figures: -Referring to Figure 5: the counter-rotating powered trailing rotor comprising a impeller or ducted fan 41 is located behind said leading rotor 40 within the manifold creating helical flow 48, pumping out water ahead of the forming bow wave and creating a dip in water level 49 ahead of the bow bulb 50. The exhaust water is then ducted externally aft 42 of the bow bulb, proud of the bows! boundary layer 44 where it unites with the bows 47 to deflect flow and prevent the vortex streaming from collapsing prematurely as it is deflected in flow by the bows 51.

The drag-reducing marine propulsion system is thus mounted about the front of a ships bow-bulb with said trailing channel-ducted vortex bisector cone comprising vessel's bow bulb skin and or bows and trailing hull, providing a combined means of hull vortex generation, bisection, propulsion, power generation, drag-reduction, steering and streaming, wherein said vortex-generating ducted channel rotor cone's vortex flow bisection by said stator cone creates an external resonant turbulent rotating vortical flow within the boundary layer flow used for said streaming over the bow bulb and hull creating drag reduction, and an internal collected bow bulb bisected counter-rotating vortical flow, powered by said trailing ducted powered propeller flow-compressing propulsor of lower pitch and used for vectored how-thrusting, maintaining external vortex flow streaming deflected aft over and ahead of the bows, and or power generation.

The Third Embodiment of The Invention will now be described: -The drag-reducing, vortex thrusting and streaming marine propulsion system Referring to Figure 3a: -the bow section is shown in front of a regular rectangular flat-bottomed container-scale Panamax Class ship hull in part section X -X with bow bulb vortex-streaming, channel-ducted hydrofoils extended over the bows and hull 3.

The vortex-generating rotor cone flow inlet 2 is located around the front of the bow bulb and is shown as a powered impeller with integral manifold surfaces 4.

Referring to Figure 3b: -the external bisected hull vortex streams 5, 6 generated by the vortex generator rotor cone 7 are shown channel-ducted along the sides of the bow bulb and the trailing rectangular, flat-bottomed hull in flow. Internal bisected vortex flow passes out through the vents which may be angled to provide bow thruster vectoring 8 when the vortex generator rotor cone is actively powered. The vortex generator rotor cone can also spin passively in flow when anchored, allowing power to be drawn by a generator to provide electricity.

Referring to Figure 4: -the vortex-streaming external-bisected rotor flow 12 is channelled along the trailing bow bulb and ships hull 16 in the boundary layer by vanes as shown in Figure 2a. The hull sits lower in the water and is semi-submersible to cut through waves and reduce slamming and stresses, advantageously creating less drag in displacing flow 10 due to said vortex boundary layer streaming, with the bisector rotor drawing water internally thereby reducing the bow wave height 14. As the vortex rotor cone 12 spins passively in flow, it directs water alternately along opposite sides of the vortex bisector cone; along internal and outer bow bulb surfaces respectively. Internal vortex stream is released by vents located flush behind the bow bulb 17.

Referring to Figure 5; internal water flow is ducted through the mouth of the manifold at the front of the bow bulb into powered compressor fan 41. Exhaust pressurised water is ducted backwards via radial ducting vanes 42 outside the hull into flow via hydrofoil array 43, which is mounted proud of the hull and boundary layer 44 thereby providing forward propulsion 45 whilst maintaining the vortex-streaming over thc bows and hull 46 and preventing it from collapsing. The sudden change in angle made between the bows and the bow bulb 47 can through hydrodynamic pressure cause said vortex-streaming in the boundary layer to collapse, therefore said manifold array is positioned strategically overhead to prevent this collapse from occurring by diverting flow above to maintain drag reducing vortex streaming in the boundary layer undisturbed along the bows where most of the drag is formed.

Referring to Figure 6: in the Third Embodiment of the Invention, a fully-submersible vessel with a substantially ovaloid or cigar hull shape e.g. a submarine 68 has a bows vortex ring generator rotor cone 64 rotating freely in flow with an internal ducted trailing counter-rotating compressor fan, ducting waste water via bows hydrofoil 67 aft to conserve vortex streaming in the boundary layer 63 and a ducted stern-powered dual rotor, bisector stator vortex ring-blowing system 61. The wake produced from the ducted stem propulsor 60 is minirnised due to the vortex ring flow limited dispersion and the aft-trailing vortex ring stream 62 expands to fill the stem gap, eliminating stem wave formation and drag hence making the craft stealthy. As the vortical flow rings rolling along the ovaloid hull are interrupted by the conning tower 65, they collapse. Vortical ring-streaming boundary layer flow is then re-instated mid-ships behind the conning tower and ahead of the tapering stern via ducted powered hydrofoil flow and a further vortex-generating rotor proud of the boundary layer 66.

Referring to Figure 7: -a marine vessel's hull is shown in sectional plan travelling with velocity V through water with ambient velocity V=0. The trailing vortices mid-ships 50 travelling forwards at V/2 and are shed from the stem of the hull as shown where they cancel and eliminate wake 51. Since the vortices are spun-up to have an outer speed of over V0 to match the ambient stationary water, and an inner speed the principle of hull vortex-streaming drag-reduction in the boundary layer to match or exceed hull speed V, the drag due to friction is largely eliminated. As the vortices trail along the hull, they expand in diameter to 50, thereby slowing down.

By spinning-up the leading bow vortices faster than flow, indicated by + +, bows drag is eliminated as they are swept back along the bows in shear. The trailing stern vortices are slowed, indicated by 0 0', with speed V12 rolling along the the mid- ships, thereby minimising drag. The slowed drag-inducing vortices, indicated by -- ,are eventually shed from the stem where they vortex cancel as shown by wavy line and X', thereby eliminating wake to make the ships hull stealthy'.

Claims (4)

1. Claims I. A drag-reducing marine propulsion system comprising one or more: -raised pitch flow-scanning vortex-generating ducted-channel rotor cones typically of 60-75 degrees ducted-channel angle rotating freely and or power assisted in flow, located axially on a flow-channel-ducted vortex bisector cone stator, with a leading or trailing ductcd powered impeller propeller or fan flow-compressing propulsor of normal pitch typically of 30-45 degrees blade angle, located axially within a manifold.
2. 2. A drag-reducing marine propulsion system as claimed in claim 1 mounted about the front of a ships bow-bulb with said trailing channel-ducted vortex bisector cone comprising vessel's bow bulb skin and or bows and trailing hull, providing a combined means of hull vortex generation, bisection, propulsion, power generation, drag-reduction, steering and streaming, wherein said vortex-generating ducted channel rotor cone's vortex flow bisection by said stator cone creates an external resonant turbulent rotating vortieal flow within the boundary layer flow used for said streaming over the bow bulb and hull creating drag reduction, and an internal collected bow bulb bisected counter-rotating vortical flow, powered by said trailing ductS powered propeller flow-compressing propulsor of lower pitch and used for vectored bow-thrusting, maintaining external vortex flow streaming deflected aft over and ahead of the bows, and or power generation.
3. 3. A drag-reducing marine propulsion system as claimed in claim I comprising: -a vortex-generating externally-mounted rotor cone rotating in flow mounted about the front of a submersible vessels bow bulb, with a trailing flow-channelled vortex bisector cone comprising the skin of said bow bulb, located within said bow bulb housing an internally bisected vortex flow powered compressor rotor and an externally-ducted radial exhaust manifold, providing a combined means of hull vortex-generation, bisection, propulsion, power generation, drag-reduction, bow thrusting and streaming wherein said rotor cone's vortex bisection creates an external resonant turbulent vertical boundary layer flow used for said streaming over the bow bulb bows and hull thereby creating said drag reduction.drag-reducing marine propulsion system as claimed in claim 1 comprising a marine drag reduction system as claimed above wherein said ducted collected bow bulb flow used for bow-thrusting, power generation and propulsion.
4. 4. A marine drag reduction system as claimed above wherein the bow wave, flow and it's submerged shock waves are dismantled by packetizing and rotating said packets so that they flow and roll along the hull surfaces within the boundary layer providing a means of drag reduction and disperse creating stealth.Amended claims have been fi(ed as follows:-4' Claims 1. An outboard propulsion system for a marine vessel wherein the drive arrangement comprises a shrouded vortex generating rotor cone having twisted ribs or ducts formed in its outer surface and a channel ducted stator cone means, wherein the channel ducted stator means is provided with vanes that define longitudinal channels that receive the vortex produced by the rotor cone.2. An outboard propulsion system for a marine vessel as claimed in claim 1 wherein the drive arrangement forms one or more vectored propulsor pods located about the hull of the ship. e SS * ct4. I 1 * * , * 5S En'CS * (5 * * * I