US 4,363,630 AGranted

Ship's hull with a helical channel ahead of each propeller and method of establishing the shape of the same

OwnerGiovanni B. T. Di Viganoinventor

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Abstract

A clear annular space is provided around the propeller shaft shroud between the aft end of the helical channel proper and the propeller disc. The helical channel is brought far enough around the shaft shroud root so that the aft end of the web formed where the helical channel becomes tangent to the outer hull skin is at an angle not exceeding 40.degree. above the horizontal and preferably not more than 35.degree.. The overall cross-sectional taper of the afterbody takes into account the shaft shrouds as well as the rest of the hull. Because it has been found that the effectiveness of helical channels in smoothing out the torque loads on propeller blades is difficult to predict and sometimes is negative, the method of establishing the configuration by model tests is important. In that method, the radial component of water flow with respect to the propeller disc may be neglected, but both the axial and the peripheral component must be considered in establishing a favorable hull configuration.

Claims49

Dependent claims

A method of establishing the configuration of the underwater afterbody of the hull of a screw-propeller-driven ship provided with a helical channel for guiding the flow of water relative to the advancing hull towards a propeller when the ship is under way, comprising the performance of the basic steps of measuring the water flow relations at the propeller disc location of a model of a proposed hull, then modifying the model to optimize the shape of the underwater afterbody of the hull, and finally, after repetition of the measuring and modifying steps as found necessary or desirable, establishing a hull afterbody configuration with more favorable water flow relations at the propeller disc, in which method there is the improvement consisting in that:

the measurement of the flow relations at the location of the propeller disc of a model is a measurement of the tangential and axial velocity components (V.sub.t,V.sub.a) of water flow entering the propeller disc when no propeller is present at enough points around the propeller disc to establish a characteristic curve which gives the incident flow velocity vector (V.sub.s) against a blade of a propeller of a selected configuration at a selected operating speed of revolution at a radius (r.sub.q) value typical for effective thrust development, expressed in coordinates of tangential and axial vector components (V.sub.q,V.sub.a), disregarding any radial components, for various values of the angular position of a propeller blade around the propeller axis;
there are established, for comparison with results of said flow relation measurement, the thrust values of the blade of a selected propeller for the full range of incident-flow vectors that are of interest;
the thrust value relations to incident-flow vectors are used to plot "isodyne" lines and said characteristic curve on the same vector field, to show incident flow of velocities at respective locations around the propeller disc in coordinates of tangential and axial flow velocity (V.sub.q,V.sub.a) and simultaneously to show the range of propeller blade thrust variation resulting from the same combinations of tangential and axial flow;
the step of modifying the tested model in respect of the position of the propeller disc and the location and shape of a helical channel and the cross-sectional taper of the stern portion of the hull on the thrust variation range of a propeller revolution is carried out by reference to the relation of corresponding modified characteristic curves to the propeller isodyne lines on a common vector field plot of tangential and axial flow velocity (V.sub.q,V.sub.a) and
the modifying of the model so as to reduce the thrust variation range of the propeller blade revolution is thereby carried out to an extent beyond which reduction would no longer be economically justified by the relation of construction complication to the degree of further reduction that is producible.

2 more elements

A hull for a ship having a pair of counter-rotating propellers on opposite sides of the lengthwise vertical median plane of the ship on the stern portion of the ship for driving the ship by rotation of the propellers, each on a propeller shaft, in the direction in which the propeller blades move downward when they are in the quadrant of their revolution directed towards said median plane, said hull including for each propeller shaft a shaft shroud body extending aft from a propeller shroud root bulging from the portion of the hull in which the hull cross-section below the waterline tapers towards the stern of the hull, and said hull being further provided with a pair of helical channels affecting the profiles of said shroud roots as well as of said hull portion and respectively leading to each propeller so as to lead water, during forward motion of the ship with a component of twist around the aft portion of the shaft shroud, to the path of the propeller blades, in the direction of twist that is contrary to the direction of revolution of the propeller, in which hull there is incorporated the improvement consisting in that:

the helical channel in each case terminates by merger into a clear annular space surrounding the propeller shaft shroud at a location where the channel profile (UQT) reaches substantial tangency to the aft end of an external hull skin surface (LQS) connecting the main portion of the hull to the propeller shaft shroud and the line (RQ) drawn to the place (Q) where said tangency is reached from the center of curvature (R) of the portion of the shaft shroud surface tangent to a vertical line on the opposite side of the shaft shroud, which line lies in an athwartship plane passing through said place of reaching tangency, runs, from above center of curvature, at an angle not more than 40.degree. above the horizontal, nor more than 60.degree. below the horizontal,
the stern portion of the hull aft of the merger of said helical channels into said clear annular spaces is not supported by any keel, fin or deadwood structure extending to the neighborhood of the plane of the bottom of the hull;
the most concavely bent portion of the profile of the helical channel is in each case near the point (P) of tangency thereto of a line drawn through the center of curvature of the profile, in the same athwartship vertical profile plane, of the part of the propeller shroud root tangent to a vertical line, for all parts of the propeller shroud root having a profile passing through the vertical, and
the curvature of said most concavely bent portion of said profile does not decrease lengthwise of the channel towards the stern over the entire length of the helical channel.

1 more element

A hull for a ship having a pair of counter-rotating propellers on opposite sides of the lengthwise vertical median plane of the ship on the stern portion of the ship for driving the ship by rotation of the propellers, each on a propeller shaft, in the direction in which the propeller blades move downward when they are in the quadrant of their revolution directed towards said median plane, said hull including for each propeller shaft a shaft shroud body extending aft from a propeller shaft shroud root bulging from the portion of the hull in which the hull cross-section below the waterline tapers towards the stern of the hull, and said hull being further provided with a pair of helical channels affecting the profiles of said shroud roots as well as of said hull portion and respectively leading to each propeller so as to lead water, during forward motion to the ship, with a component of twist around the aft portion of the shaft shroud, to the path of the propeller blades, in the direction of twist that is contrary to the direction of revolution of the propeller, in which hull there is incorporated the improvement consisting in that:

the helical channel in each case terminates by merger into a clear annular space surrounding the propeller shaft shroud at a location where the channel profile (UQT) reaches substantial tangency to the aft end of an external hull skin surface (LQS) connecting the main portion of the hull to the propeller shaft shroud and the line (RQ) drawn to the place (Q) where said tangency is reached from the center of curvature (R) of the portion of the shaft shroud surface tangent to a vertical line on the opposite side of the shaft shroud, which line lies in an athwartship plane passing through said place of reaching tangency, runs, from said center of curvature, at an angle not more than 40.degree. above the horizontal, nor more than 60.degree. below the horizontal,
the helical channels merge on the afterbody of the hull with a single keel channel;
on the forebody of the hull said keel channel divides into two channels, extending towards the bow from the place of division, which two channels are symmetrical with respect to the middle of the ship;
the most concavely bent portion of the profile of the helical channel is in each case near the point (P) of tangency thereto of a line drawn through the center of curvature of the profile, in the same athwartship shroud root tangent to a vertical line, for all parts of the propeller shroud root having a profile passing through the vertical, and
the curvature of said most concavely bent portion of said profile does not decrease lengthwise of the channel towards the stern over the entire length of the helical channel.

2 more elements

A hull for a ship having a first pair and a second pair of counter-rotating propellers each of said pairs consisting of propellers respectively located symmetrically on opposite sides of the lengthwise vertical median plane of the hull on the stern portion of the ship for driving the ship by rotation of the propellers, each on a propeller shaft, in the direction in which the propeller blades move downward when they are in the quadrant of their revolution directed towards said median plane, said first pair constituting an inner pair located farther aft than said second pair, which constitutes an outer pair, said hull including for each propeller shaft a shaft shroud body extending aft from a propeller shroud root bulging from the portion of the hull in which the hull cross-section below the waterline tapers towards the stern of the hull, and said hull being further provided with two pairs of helical channels affecting the profiles of said shroud roots as well as of said hull portion and respectively leading to each propeller so as to lead water, during forward motion of the ship with a component of twist around the aft portion of the shaft shroud, to the path of the propeller blades, in the direction of twist that is contrary to the direction of revolution of the propeller, in which hull there is incorporated the improvement consisting in that:

the helical channel in each case terminates by merger into a clear annular space surrounding the propeller shaft shroud at a location where the channel profile (UQT) reaches substantial tangency to the aft end of an external hull skin surface (LQS) connecting the main portion of the hull to the propeller shaft shroud and the line (RQ) drawn to the place (Q) where said tangency is reached from the center of curvature (R) of the portion of the shaft shroud surface tangent to a vertical line on the opposite side of the shaft shroud, which line lies in an athwartship plane passing through said place of reaching tangency, runs, from said center of curvature, at an angle not more than 40.degree. above the horizontal, nor more than 60.degree. below the horizontal,
the most concavely bent portion of the profile of the helical channel is in each case near the point (P) of tangency thereto of a line drawn through the center of curvature of the profile, in the same athwartship vertical profile plane, of the part of the propeller shroud root tangent to a vertical line, for all parts of the propeller shroud root having a profile passing through the vertical, and
the curvature of said most concavely bent portion of said profile does not decrease lengthwise of the channel towards the stern over the entire length of the helical channel.

A hull for a ship having an odd number of propellers in which:

at least the convex portions of the hull located forward of at least some concave hull portions produced by the presence of a helical channel in the hull are asymmetrically shaped underneath the waterline with respect to the vertical plane passing through the bow and stern waterline extremities so as to produce, when the hull moves through the water, a flow of water relative to the hull greater and faster on one side than on the other side, thereby to produce a vortex in the wake of the keel, and
said helical channel is provided in the after portion of the hull leading from a portion of the hull bottom where water flowing into said channel can readily pick up energy from the pre-development of said keel wake vortex and leading to a place forward of the middle or only propeller of the ship, so as to guide and reinforce said keel wake vortex and thereby to counter the vortex producing action of said propeller at the cruising speed of the ship and thus improve the propeller efficiency, said propeller being driven in a rotary direction opposite to that of the keel-wake vortex guided by said helical channel.

Dependencies are inferred from the claim text.

Facts

Application: 05/842,925Filed 17 Oct 1977 · continuation in part
Priority: DE 25147844 Apr 1975
Granted: 14 Dec 1982
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

B63H 5/16
Of propellers: characterised by being mounted in recesses; with stationary water-guiding elements; Means to prevent fouling of the propeller, e.g.…
B63B 1/08
With single hull: shape of aft part
Y02T 70/10
Maritime or waterways transport: measures concerning design or construction of watercraft hulls
Y02T 70/50
Maritime or waterways transport: measures to reduce greenhouse gas emissions related to the propulsion system