RU2820671C1 - Ice breaker tanker aft end - Google Patents

Abstract

FIELD: shipbuilding.

SUBSTANCE: invention relates to ship building, particularly, to stern and propulsive complex of icebreaking vessels operated astern in severe ice conditions. Aft end of the ice-breaker tanker has a propulsion-steering complex, which includes three rudder propellers arranged in a triangle in the aft end of the hull of the tanker. Rudder propellers are located on separate platforms made in the form of ice teeth with streamlined shape and with sharp leading edge on the side of transom. Ice tooth trailing edge smoothly changes into tanker hull without ledges. Onboard rudder propellers are displaced relative to central rudder propeller by distance providing contactless turn of rudder propellers. In the plane of waterlines the propellers of the onboard rudder propellers do not go beyond the current waterline at any turning angle. Tanker aft end contours have a "spoon-like" shape with a smooth waterline, where the angle α waterline input is 67–72°, angle of inclination of the first theoretical frame 57–67°, angle ϕ sternpost inclination 19–27° for ballast and design draft respectively.

EFFECT: improved ice performance of tanker in ice conditions in reverse motion, as well as performance on clean water.

3 cl, 4 dwg

Description

The invention relates to the field of shipbuilding and concerns the design of the stern end and propulsion complex (of three steering columns) of double-action icebreaking ships (combining an icebreaker and a merchant ship in one hull), operating stern first in difficult ice conditions.

The development of the Arctic, the development of the Northern Sea Route, and ensuring the economic efficiency of transporting large volumes of oil determine the feasibility of using large-capacity double-action tankers with increased power and ice speed, which in difficult ice conditions are operated stern forward (reverse), which reduces ice resistance and, accordingly, operating costs for fuel and icebreaker support.

The development of such tankers is carried out taking into account the experience of designing and operating large-capacity double-acting gas carriers of the Christophe de Margerie type with a propulsion complex of three rudder propellers (RPC) with a shaft power of 3x15 MW. The use of propeller thrusters on tankers makes it possible to ensure its controllability, increase maneuverability and efficiency of reversing in ice conditions due to the erosion of ice formations by the jet from the propeller when turning the propeller drive. At the same time, in reverse modes, the thruster thrusters are subjected to intense ice exposure, and the space between the thruster struts can become clogged with ice fragments (the “wedge” effect), which reduces the efficiency of the vessel’s movement. This is a characteristic feature of the gas carrier “Christophe de Margerie” when moving in ice about 2 m thick, which is due (Fig. 1, which shows a bottom view of the bottom of the gas carrier) to the features of the aft end of the vessel with three protrusions for installing the propeller control system, which form broken waterlines. These protrusions cut the ice cover, while destruction of the ice by bending does not occur, which leads to the formation of large fragments of ice stuck between the racks of the breaker. As a result, ice resistance increases and the vessel's ice-passing capacity decreases, determined by the thickness of level ice at a bending strength of ice of 500 kPa, which the vessel can overcome at a minimum stable speed of about 2 knots. Thus, the destruction of water area ice into fragments, the width of which is much less than the distance between the racks of the thruster, is important for reducing ice resistance, increasing ice penetration and maneuverability.

The design of the aft end of an ice-sailing vessel is known (patent for invention RU 2494911, accepted as a prototype), in which, to reduce ice resistance, it is proposed to place a propulsion complex of three full-rotating propeller-propelled gears on one flat horizontal platform, fenced with an ice-removing ledge. In this case, the stern part of the vessel above the ice-release ledge has the shape of an icebreaker bow, and the stern contours below the mentioned platform, adjacent to the bottom, have a wedge-shaped shape with S-shaped waterlines. When the vessel moves in reverse, the ice cover is bent by the ice-breaking bow of the stern, then creeps under the stern part and rests against the ice-removing ledge, where the ice cover is destroyed into sectors, which prevents the interaction of ice with the racks of the thruster and, as a result, ensures the possibility of their unimpeded simultaneous rotation. However, this version of the layout of the propulsion complex and the design of the stern has a number of disadvantages, namely that in the process of interaction of the ice-release protrusion with the ice cover, ice resistance increases and the ice-passing ability of the vessel decreases. In addition, the proposed hull shape with a horizontal platform and an ice-removing ledge leads to a significant increase in hydrodynamic resistance, which significantly reduces the speed in clear water.

The objective of the proposed technical solution is to improve ice performance and maneuverability in reverse in ice conditions, as well as in clear water for forward and reverse modes.

To do this, in the aft end of an icebreaking tanker with a propulsion complex of three rudder propellers located in the aft end in a triangle, according to the invention, each rudder propeller is located on a separate platform (foundation), made in the form of an ice tooth with a streamlined shape and with a sharp incoming edge on the side transom (accepting the incoming flow of water and ice debris when moving stern forward), the trailing edge of the ice tooth smoothly transitions into the hull of the icebreaker tanker (without ledges to reduce the hydrodynamic resistance of the stern when operating the tanker in clear water), the central steering column is installed in the center plane of the icebreaker tanker , and the side rudder columns are offset relative to the central rudder column at the bow of the vessel at a distance that ensures free rotation of the rudder propellers relative to each other, the aft end of the icebreaking tanker (for effective crawling onto the ice in reverse mode) has a convex “spoon-shaped” shape with a smooth waterline, the angle α of the waterline entry is 67-72°, the inclination angle of the first theoretical frame is 67-57°, the sternpost inclination angle ϕ is 19-27° (for ballast and design draft, respectively).

The height of the ice tooth in the area of the incoming edge depends on the thickness of the ice and is at least 40% of the maximum thickness of level ice in the water area, overcome by the ship at a speed of 2 knots in reverse mode.

The essence of the technical solution is illustrated by drawings, which show: Fig. 2 - schematically shows the aft part of an icebreaking tanker with three propellers and a central skeg with S-shaped waterlines (bottom view on the bottom); in fig. 3 - side view of the stern end in the center plane of the icebreaking tanker; in fig. 4 - schematically shows the principle of operation of the stern of a tanker when moving in reverse in ice.

The figures indicate: 1 - tanker hull; 2 - VRK; 3 - waterline; 4 - ice tooth; 5 - incoming edge of the ice tooth; 6 - trailing edge of the ice tooth; 7-8 - ice sector; 9 - ice fragment; α - entry angle of the current waterline 67° and 72°; ϕ - sternpost angle of 19° and 27°.

The aft end of the ice tanker has (Fig. 2) a hull 1, three breakers 2, which are placed on foundations designed in the form of ice teeth 4 with a well-streamlined shape and a sharp leading edge 5 for splitting ice fragments from the ice cover destroyed by bending upon contact with the body and reducing the intensity of contact of the VRK stand with ice. To ensure the breaking of ice fragments, the height of the ice tooth in the area of the incoming edge is at least 40% of the maximum thickness of level ice in the water area, overcome by the ship at a speed of 2 knots in reverse mode. The transverse size of the ice tooth 4 is determined by the diameter of the VRK landing unit. The trailing edge of the ice tooth 6 smoothly transitions into the body 1 without ledges to reduce the hydrodynamic resistance of the stern when operating the tanker in clear water. Ice teeth are installed on the hull 1 of a tanker with a central skeg with S-shaped waterlines 3, which improves the hydrodynamic flow around the stern in the specified area in forward and reverse modes. The central, side thrust control gears and, accordingly, the ice teeth on the bottom of the hull 1 are placed in a triangle. The central thruster is shifted towards the transom, and the side thrusters are shifted relative to the central one towards the bow of the tanker by a distance that ensures free rotation of all three thrusters. To allow the passage of ice fragments and to prevent the “jamming” of ice fragments between the racks of the onboard and central thruster, the distance between them is at least 5×t _max , where t _max is the maximum thickness of level ice in the water area that the vessel can overcome at a speed of 2 knots in reverse mode. Additionally, the placement of the propellers is regulated by ensuring contactless rotation of the propellers, while in the plane of the waterlines, the propellers of the onboard propellers should not extend beyond the current waterline at any angle of rotation. The contours of the aft end of the icebreaking tanker have a “spoon-shaped” shape with a smooth waterline 3 and the angle α of the entry of the existing waterline of 67° and 72°, (Fig. 2), the angle of inclination of the first theoretical frame is 67° and 57° (5% of the length of the vessel waterline from the sternpost aft end), the sternpost tilt angle ϕ is 19° and 27° for ballast and design drafts, respectively (Fig. 3). For a relative thickness of level ice not exceeding t/B=0.048, where t is the thickness of level ice, B is the width of the tanker, the presented values are guaranteed to ensure the destruction of the level ice cover by bending of the acting waterline into two sectors (ice fragments) between the central and side propellers, which are additionally cut and split by the sharp incoming edge of the ice teeth into smaller fragments that freely pass along the bottom between the ice teeth.

Operation of the proposed ice-sailing tanker in reverse mode in ice conditions is carried out as follows. When the hull 1 of the tanker interacts with the ice cover, the ice cover is destroyed by bending into ice fragments 7 (Fig. 4), as a result of which two ice sectors 7, 8 are formed between the side and central air handlers. The third ice fragment 9 is formed in the area of the side ice tooth on the side stern cheekbones. As the stern moves, the sharp incoming edge of the central and side ice teeth additionally cuts and splits ice fragments into smaller ones, which prevents the ice cutting by the racks of the VRK 2. Smaller ice fragments pass freely without jamming between the VRK 2, after which they fall on the surface of the skeg with S -shaped waterline and are thrown off the side, thereby preventing the formation of ice accumulation on the bottom of the vessel (Fig. 4). The fragment 9 is cut off by the incoming edge of the side ice tooth and is also thrown from the bottom onto the side.

When operating in clear water in forward mode, continuous flow around the stern is ensured, thereby reducing hydrodynamic drag and increasing operating efficiency.

The stern end of a double-acting icebreaking tanker with a propulsion complex of three propellers is part of the vessel's hull, providing the required seaworthiness characteristics by constructively protecting the ship's rudder complex from the impact of ice debris on it when moving stern forward.

Claims (3)

1. The aft end of an icebreaking tanker, having a propulsion-steering complex, including three rudder propellers placed in a triangle in the aft end of the tanker hull, with the central rudder propeller installed in the center plane of the vessel offset towards the transom, and two rudder propellers installed on the sides, characterized in that that the rudder propellers are located on separate platforms, made in the form of ice teeth with a streamlined shape and with a sharp incoming edge from the side of the transom, the trailing edge of the ice tooth smoothly passes into the tanker hull without ledges, the side rudder propellers are offset relative to the central rudder propeller at a distance ensuring non-contact rotation of the rudder propellers, while in the waterline plane the propellers of the onboard rudder propellers do not extend beyond the current waterline at any angle of rotation, while the contours of the aft end of the tanker have a “spoon-shaped” shape with a smooth waterline, with the angle α of the waterline entry being 67-72° , the angle of inclination of the first theoretical frame is 57-67°, the angle of inclination ϕ of the stern post is 19-27° for ballast and design draft, respectively. 2. The aft end of the icebreaking tanker according to claim 1, characterized in that the distance between the racks of the side and central rudder propellers is at least 5×t _max , where t _max is the maximum thickness of flat ice in the water area overcome by the vessel at a speed of 2 knots in the mode reverse. 3. The aft end of the icebreaking tanker according to claim 1, characterized in that the height of the ice tooth in the area of the incoming edge is at least 40% of the maximum thickness of flat ice in the water area, overcome by the ship at a speed of 2 knots in reverse mode.