Patent Application
20110263168
Important benefits are realized by the utilization of bow mounted surface-piercing propeller systems, both on large displacement vessels such as ships and barges, and on more streamlined, lower displacement, high speed watercraft. Most significant of these benefits is the production of the self-producing, lubricating boundary layer of gaseous fluid, e.g. air and air bubbles created by the intermixing by the rotating bow propeller of water and air. This layer of gaseous bubbles, produced during forward vessel motion, travels over the bottom surface of the vessel, thus reducing frictional drag on the vessel's hull as it moves through the water. This significant benefit of bow mounted surface-piercing propellers, as well as others, are described in detail in U.S. Pat. No. 7,096,810, the relevant disclosure of which is incorporated by reference herein.
It is accepted that vessel thrust and thus vessel efficiency will be increased by the use of a propeller shrouded marine propeller. See, for example, U.S. Pat. No. 2,030,375. However, the inherent drag of a propeller shroud, nozzle, or duct will, at certain speeds, begin to erode the efficiency of the propulsion system. As speed increases, there will continue to be an incremental decrease in efficiency, such that vessels so equipped are generally limited to slower speeds.
In addition, shrouded propellers are quite susceptible to cavitation within the shroud, thus further impacting propeller efficiency and presenting the strong possibility of propeller blade damage. Attempts to enhance the efficiency of submerged shrouded propellers by introducing air or other gaseous fluids to prevent cavitation have met with limited success.
The object of the present invention is to overcome the disadvantages and limitations of submerged, ducted propulsion systems by creating a water surface-piercing propeller environment within the duct, enclosure, or hull enclosure in which the propeller is operating; and further by effectively streamlining the duct in order to offset its detrimental drag effects, as it moves through the water. The result is an enclosed or ducted propulsion system which can propel vessels of any displacement at much higher speeds and with greater efficiency.
Significantly, the propulsion system of the present invention provides for the introduction of gaseous fluids, e.g. ambient air and/or exhaust fluid gas from the vessel's engine, into the enclosure or duct which houses or circumscribes the propeller. Air and other fluid gases are drawn down into the enclosure or duct to allow the propeller to operate in a half submerged, or water surface-piercing condition, while the vessel is moving forward through the water. The beneficial effects of water surface-piercing propeller operation is thereby obtained within a self-contained unit which continually maintains the top of the propeller out of the water during normal forward vessel operation.
In fact, in several embodiments of the invention, the rotating propeller will act as a ducted fan to suction in ambient air and/or exhaust gases and, augmented by a Venturi effect, continually feed the top section of a duct with these fluid gases to maintain the propeller as a surface-piercing unit. As the vessel is propelled forward, water is directed and will only pass through the lower section of the duct. Thus, during normal vessel operations only the lower blades of the propeller will rotate in water.
The “half-bullet” shape of the streamlined duct in several embodiments of the invention has a half-round shaped inlet. This may seem counter-productive when compared to the operation of a conventional ducted system which normally has a large, full circumference, aperture inlet for the large volume flow of water required to properly feed the shrouded propeller. However, the water flow in the duct of the present invention is accelerated through the inlet aperture of the open, forward lower section of the duct by the rotation of the propeller. As a result, the bow wave pressure is not redirected, but is sucked into this low pressure area of the duct, thereby relieving kinetic energy and contributing towards the increased efficiency of the propeller and ultimately in vessel performance.
Other embodiments of the invention position water surface-piercing propellers housed within substantially self-contained gaseous fluid supplied enclosures. Like those propellers operating in duct type enclosures, these propellers rotate in artificially created waterlines, in which half of the rotating propeller blades are also always out of the water.
Other objectives of the enclosed, water surface-piercing propeller of the invention are also achieved. For instance, given the flow of gaseous fluids, air and exhaust gas, at the intake of the propeller, there is complete propeller ventilation and a reduction of propeller cavitation at the intake. Friction on the entire propeller is also reduced. Thus, the invention provides a simplified method of addressing cavitation bubble effects, including gap cavitation, within a shrouded propeller.
The use of ambient air through the sealed housing of the drive shaft of the drive mechanism, in one of the embodiments of the invention, provides a more efficient and simplified way of supplying aeration to the duct, thereby providing the desired surface-piercing propeller effect within the duct.
The top half of the duct shown in several embodiments and the front portion of another embodiment of the present invention have bulbous bow type profiles. Such configurations have been proven to ameliorate bow wave pressure on a vessel and increase vessel performance up to 15%.
A further benefit of the present invention is the facilitating of engine exhaust venting through sealed air channels to substantially reduce the acoustic and thermal signatures of vessels. Exhaust noise suppression is also accomplished as a result of the aerated air/exhaust gas bubbles passing under the length of the bottom of the hull.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention, itself, however, both as, to its design, construction and use, together with additional features and advantages thereof, are best understood upon review of the following detailed description with reference to the accompanying drawings.
With particular reference to
Propulsion unit 10 comprises propeller 12, having a plurality of blades, operable via well known propulsion gearing 14 by the engine of vessel 100. Propeller 12 is housed or enshrouded within and circumscribed by rearward duct section 18 of propeller enclosure or duct 16. Duct 16 also comprises forward duct section 20 whose top portion 22 has a bulbous-type shape and whose bottom portion 24 gently slops downward and merges into the bottom of rearward section 18 of duct 16. Duct 16 is separated into upper duct section 26 and lower duct section 28 by transverse plate 30 which extends across the width of the duct. Duct 16 is supported beneath hull 2 by shroud member 32, through which propeller gearing 14 and gearing shroud 31 extend.
Air flow passage 34 leads from opening 36 in bow 4 of hull 2, through the hull to shroud member 32. Fluid exhaust gas from the engine of vessel 100 is directed through exhaust gas flow passage 38 to shroud member 32. It is contemplated that the system can operate by the introduction of gaseous fluids supplied by ambient air flowing through air flow passage 34 or by exhaust gas flowing through exhaust gas flow passage 38, or a combination of these gases.
Shroud member 32 is open at both its ends, so that as vessel 100 moves ahead through body of water 40 by means of the rotation of propeller 12, ambient air 44 flows through passage 34 and/or exhaust gas 39 flows through passage 38 into shroud member 32, and then into upper duct section 26 of duct 16. Gaseous fluids, e.g. air/exhaust gas, are substantially maintained within upper duct section 26 and are effectively prevented from entering lower duct section 28 by horizontally aligned transverse plate 30, which extends the width of duct 16 and is positioned approximately at the center of the duct. Thus blades 13 of propeller 12 which pass through upper duct section 26 are rotating substantially through gaseous fluids while the blades 15 of propeller 12 which pass through lower duct section 28 are rotating substantially through water. In this manner, propeller 12 becomes a “water surface-piercing” propeller. As discussed previously and in U.S. Pat. No. 7,096,810, the pertinent disclosure of which is incorporated by reference herein, surface-piercing propellers offer a number of significant advantages.
Significantly, as propeller 12 rotates it causes the gaseous fluids in upper duct section 26 to intermix with the water in lower duct section 28, producing a layer of gaseous bubbles 46 at bow 4 of hull 2. Shown best in
Top portion 22 of duct 16, with its bulbous-type configuration, further adds to the efficiency of the forward propulsion of vessel 100. Like the bulbous bows of many vessels, the bulbous top portion 22 acts to reduce the resistance on duct 16 as it moves through the water. Moreover, there will be additional buoyancy and thus added beneficial lift within top portion 22, as a result of the entrapment of gaseous fluids within upper duct section 28.
The enhanced efficiency resulting from the operation of propulsion unit 10 will result in substantial savings of both fuel costs and vessel travel time.
Although the concept of maintaining a propeller water surface-piercing environment remains the same,
Air flow passage 74 leads from an opening, in bow 104 of hull 102, similar to 36 discussed with regard to
As vessel 200 moves ahead through the water, ambient air 75 flows through air flow passage 74 into exhaust gas flow passage 78 and/or exhaust gas 77 flows through the exhaust gas flow passage. From here the gaseous fluids are directed to upper duct section 66 of duct 56, to maintain a substantially water-free, gaseous fluid filled environment in the upper duct section. The propeller water surface-piercing benefit are thus again achieved.
A snorkel like air tube 80, open at its top and bottom ends, can also be provided to allow the entry of ambient air 79 through the tube and into upper duct section 66 of duct 56. As described above, this ambient air can be combined with the air 75 from airflow passage 74 and engine exhaust gas 77 from exhaust flow passage 78 to maintain the gaseous fluid environment in upper duct section 66.
Air/exhaust gaseous fluid 91 compelled through passage 92 fills enclosure 94. As propeller 96 rotates, air is drawn to the propeller, creating a negative pressure area directly behind the hub of the propeller, thus assisting in compelling the flow of gaseous fluid through opening 99 at the bottom of enclosure 94. This will enhance the intermixing and creation of the gaseous fluid and water to create the boundary layer of gaseous bubbles 46 along the bottom of vessel hull 82, as depicted in
Ambient intake air 120 is supplied to enclosure 116 through vertical air vent tube or stack 122. Air scoop 124 located on top of air vent tube 122 provides an increased ram air effect, to assist the airflow through the vent tube, in order to accommodate increases in air consumption by propeller 112. Gaseous exhaust fluid 125 can also be supplied directly to enclosure 116 via exhaust line 126 from the vessel's engine or the exhaust line can be tapped into air stack 122 to be supplied to the enclosure, as seen in
Enclosure 116 itself is a water sealed chamber, whose bottom 128 is open to the water. The only other openings within enclosure 116 are for vent tube 122 and shaft 114, both connected through the enclosure by waterproof seals.
Rotation of propeller 112 within fluid gas filled enclosure 116 provides for intermixing of gaseous fluid and water, producing bubbles which exit the enclosure through its bottom 128. As previously described the bubbles form a lubricating boundary layer of bubbles which will travel along bottom of hull 111 of vessel 400.
The principles of the invention can be applied to outboard motor 130, which could be mounted on bow 134 of hull 132 of vessel 500, as seen in
Certain novel features and components of this invention are disclosed in detail in order to make the invention clear in at least one form thereof. However, it is to be clearly understood that the invention as disclosed is not necessarily limited to the exact form and details as disclosed, since it is apparent that various modifications and changes may be made without departing from the spirit of the invention.
