DEVICE FOR PROPELLING SHIPS, AND A NOZZLE USED IN THE DEVICE

Abstract: The invention relates to a device for propelling ships and the like, and a nozzle for (2) use in such a device. The nozzle has a cylindrical inner surface (7) which at the inlet side (8) and at the outlet side (9) is connected by means of a parabolic profile and a radius of curvature to an outer surface (6). At the inlet side (8) the radius of curvature and/or the distance to the front side of the nozzle are greater than the radius of curvature at the outlet side (9) and/or the distance to the rear side of the nozzle respectively.

Description: Device for propelling ships, and a nozzle used in the device The invention relates to a device according to the preamble of Claim 1. Such a device is known, inter alia, from patent application NL 1004558 of the same applicant. In the case of the known device with nozzle the nozzle has the special characteristic that when the screw propeller rotates in the opposite direction, during which the water stream flows from the rear side of the nozzle to the front side, a greater braking force is exerted upon the ship. However, the profile used for this purpose, with radius of curvature and parabolic profile at the rear side of the nozzle, was found to have an adverse effect on the thrust, and thus on the propulsion efficiency during travel in the forward direction. In order to avoid the above entioned disadvantage, the device is designed according to the characterizing part of Claim 1. As a result, the inflow of the water into the nozzle at the front side is improved, so that the thrust during travel in the forward direction is increased and the propulsion efficiency is therefore greater. It has been found that the braking force is not reduced when the screw propeller is rotating in the opposite direction. According to a further improvement, the device is designed according to Claim 2. This makes a further increase in thrust possible. According to various improvements, the device is designed according to one of Claims 3-10. The improvements relate to various embodiments. The invention also relates to a nozzle according to Claim 11. ' The invention is explained below with reference to an exemplary embodiment by means of a drawing. In the drawing: Figure 1 shows an exemplary embodiment of a stern of a ship, and Figure 2 shows a cross section of the profile of a nozzle used in the device according to Figure 1. Corresponding parts as far as possible are always indicated by the same reference numerals in the two figures. Figure 1 shows a stern 1 with a screw propeller 3 which is rotatable about an axis of rotation. A nozzle 2 is fitted around the screw propeller. The rotating screw propeller 3 causes a water stream F and pushes water backwards in the direction of a rudder 4, with the result that thrust is exerted upon the ship and the ship will move forwards, which means to the left in Figure 1. As far as possible, the nozzle 2 is designed all round without obstructions and in the plane through the axis of rotation of the screw propeller 3 as far as possible always has the same profile. Locally there are deviations on the outside of the profile in particular, because supports by means of which the nozzle 2 hangs on the stern 1 are provided on the nozzle. In order to avoid corrosion, anodes 5 are provided on the stern 1, the nozzle 2 and the rudder 4. In the embodiment shown, the nozzle 2 is fastened to a stern 1. Embodiments in which the nozzle, screw propeller and possibly the rudder are assembled to form a rudder propeller are also known. The nozzle according to the invention can likewise be used for these and also other embodiments. Figure 2 shows a cross section through the nozzle 2, which cross section shows the profile of the nozzle 2 in the plane through the axis of rotation of the screw propeller 3. The nozzle 2 is placed concentrically around ' the screw propeller 3, which is indicated in Figure 2 by a contour 10 of broken lines. The screw propeller 3 has a diameter D 4 . At the position of the screw propeller 3 the nozzle 2 has a cylindrical inner surface 7. The cylindrical inner surface 7 has an internal diameter D 3 , which is approximately 0.8% larger than the diameter D of the screw propeller 3. With smaller diameters of screw propeller 3 the internal diameter D 3 is at least 10 to 20 mm greater than the external diameter D 4 of the screw propeller 3. If the screw propeller 3 is adjustable, the gap between the screw propeller 3 and the nozzle 2 is generally kept larger. Rotation of the screw propeller 3 produces the water stream F, the direction of which corresponds to that indicated in Figure 1. The nozzle 2 has at the front side a cylindrical outer surface 11 with an external diameter Di, which cylindrical outer surface has a length L 4 and merges towards the back into a conical outer surface 6, the diameter of the outer surface 6 becoming smaller towards the back and forming an angle of taper with the axis of rotation of the screw propeller 3. The external diameter Di is approximately 1.2 to 1.3 times the diameter D 4 of the screw propeller 3, and is preferably 1.25 times the diameter D 4 . The length L of the cylindrical outer surface can vary from zero to 0.032 times the diameter D 4 of the screw propeller 3, and is preferably 0.016 times the diameter D 4 . The angle of taper α can vary from four to seven degrees, and is preferably approximately 5.6 degrees. At the front side of the nozzle 2 the cylindrical outer surface 11 merges with an inlet radius R x into an inlet surface 8 which connects to the cylindrical inner surface 7. The inlet radius R λ is approximately 0.019 to 0.023 times the diameter D 4 of the screw propeller 3, and is preferably 0.021 times D . The inlet length L 2 from the front side of the nozzle 2 to the cylindrical inner surface 7 is approximately 0.19 to ' 0.23 times the diameter D of the screw propeller 3, and is preferably 0.21 times the diameter D 4 . The cylindrical inner surface 7 has a length of 0.11 to 0.14 times the diameter D 4 of the screw propeller 3, so that the distance from the front side of the nozzle 2 to the centre of the cylindrical surface 7 is a length of 0.25 to 0.29 times the diameter D of the screw propeller 3, and is preferably 0.27 times the diameter D 4 . The profile of the inlet surface 8 is designed in such a way that near the inlet radius Ri the profile has a radius which corresponds to the inlet radius R lf and has a line of contact there which is also more or less tangential to the inlet radius Ri, and near the cylindrical inner surface 7 has a very large to infinite radius, and has a line of contact there which runs more or less parallel to the cylindrical inner surface 7. The profile of the inlet radius 8 preferably runs parabolically. At the rear side of the nozzle 2 the conical outer surface 6 merges with an outlet radius R 2 into an outlet surface 9 which connects to the cylindrical inner surface 7. The outlet radius R is approximately 0.015 to 0.019 times the diameter D 4 of the screw propeller 3, and is preferably 0.017 times D 4 . The outlet length L 3 from the rear side of the nozzle 2 to the cylindrical inner surface 7 is approximately 0.15 to 0.19 times the diameter D 4 of the screw propeller 3, and is preferably 0.17 times the diameter D 4 . The profile of the outlet surface 9 is designed in such a way that the profile near the outlet radius R 2 has a radius corresponding to the outlet radius R 2 , and has a line of contact there which is also more or less tangential to the outlet radius R 2 , and near the cylindrical inner surface 7 has a very large to infinite radius and has a line of contact there which runs more or less parallel to the cylindrical inner surface 7. The profile of the outlet radius 9 preferably runs parabolically. The inlet radius Ri and the outlet radius R 2 are preferably designed " as round bar material or round tubing rolled in a circle, which gives a strong construction. The material is carbon steel. The inlet surface 8, the cylindrical inner surface 7 and the outlet surface 9 are made of stainless steel, so that corrosion is avoided. In addition to the design mentioned above, all parts of the nozzle can also be made of stainless steel or carbon steel, or parts can be made of these or other suitable materials, depending on their use. The nozzle 2 has a length L x which is equal to approximately 0.5 times the diameter D of the screw propeller 3. The length of the cylindrical inner surface 7 is approximately 0.125 times the diameter D of the screw propeller 3. The centre of the outer periphery of the screw propeller 3 corresponds more or less to the centre of the cylindrical inner surface 7. It has been found that the position of the centre of the outer periphery of the screw propeller should preferably be placed approximately 0.55 times the length Li of the nozzle 2 from the front side of the nozzle 2. Embodiments in which the dimensions of the profile are adapted slightly are possible. In this case the length of the cylindrical inner surface 7, for example, can be longer, the length L 4 of cylindrical outer surface 11 and the length Li of the nozzle 2 being increased by the same value. Other profile adaptations can result in adaptations in the various diameters of the angle of taper α, in which case the inlet radius Ri and/or the inlet length L 2 will always remain greater than the outlet radius R 2 and/or the outlet length L 3 . The shape of the outer surface 6 shown, which for production reasons is conical, can also be adapted and, viewed in the lengthwise direction, can be given, for example, a slightly curved profile. The efficiency of the nozzle according to the invention does not suffer any adverse effects if the shape of the outer surface 6 is designed in such a way that no inadmissible disruptions such as local separation of the flow from the outside wall of the nozzle 2 occur. It has been found from experiments that by making the improvement according to the invention the propulsion efficiency can be improved by 4%. By using the nozzle according to the invention, a considerable saving is achieved for the user of a ship, while the required braking power, where during backward thrust, for example, a ship must be at a standstill within its length, remains at least the same.

Claims: Claims 1. Device for propelling ships and the like, comprising a screw propeller (3), which can be rotated about an axis of rotation by means of a drive, and a nozzle (2) mounted concentrically around the screw propeller (3), for guiding the water (F) which is set in motion by the rotating screw propeller, the nozzle being provided on the inside with a first cylindrical surface (7) which has an internal diameter (D 3 ) which is a gap width greater than the external diameter (D 4 ) of the screw propeller (3), and the nozzle being provided on the outside with an outer surface (6) which has the greatest external diameter (Di) near the front side of the nozzle, the nozzle also having a profile in an arbitrary plane through the axis of rotation, with radii of curvature (Ri, R 2 ) which connect to the outer surface being provided at the front side and the rear side of the nozzle, which radii of curvature on the inside of the nozzle connect with more or less parabolic profiles (8, 9) to the first cylindrical surface (7), characterized in that the radius of curvature (Ri) at the front side of the nozzle and the distance (L 2 ) from the front side of the nozzle to the first cylindrical surface (7) are greater than the radius of curvature (R 2 ) at the rear side of the nozzle and the distance (L 3 ) between the rear side of the nozzle and the first cylindrical surface respectively. 2. Device according to Claim 1, characterized in that at the front side of the nozzle (2) the radius of curvature (Ri) merges on the outside into a second cylindrical surface (11) , which connects to the outer surface (6) . 3. Device according to Claim 1 or 2, characterized in that the length (L ' ι) of the nozzle is approximately half the diameter (D 4 ) of the screw propeller (3) . 4. Device according to Claim 2 or 3, characterized in that the radii of curvature (Ri, R 2 ) are greater than 0.015 times the diameter (D 4 ) of the screw propeller (3) . 5. Device according to one of the preceding claims, characterized in that the radius of curvature (Ri) at the front side is approximately 0.019 to 0.023 times the diameter (D 4 ) of the screw propeller, and is preferably 0.021 times the diameter (D ) of the screw propeller (3) . 6. Device according to one of the preceding claims, characterized in that the distance from the front side of the nozzle to the centre of the first cylindrical surface (7) is approximately 0.25 to 0.29 times the diameter (D 4 ) of the screw propeller (3) , and is preferably 0.27 times the diameter (D 4 ) of the screw propeller (3) . 7. Device according to one of the preceding claims, characterized in that the greatest diameter (Di) of the outer surface (6) or the diameter of the second cylindrical surface (11) is approximately 1.2 to 1.3 times the diameter (D ) of the screw propeller (3), and is preferably 1.25 times the diameter (D 4 ) of the screw propeller (3) . 8. Device according to one of the preceding claims, characterized in that the smallest diameter (D 2 ) of the outer surface (6) is approximately 1.16 times the diameter (D ) of the screw propeller. 9. Device according to one of the preceding claims, characterized in that the length of the first cylindrical surface (7) is approximately 0.11 to 0.14 times the diameter (D 4 ) of the screw propeller (3), and is preferably 0.125 times the diameter (D 4 ) of the screw propeller (3) . 10. Device according to one of the preceding claims, characterized in that the outer surface (6) is largely conical, with an angle of taper (α) of approximately four to seven degrees. 11. Nozzle for use in a device according to one of the preceding claims.

Inventors: DEN UIL ARIE, DEN UIL, ARIE
Applicants: DEN UIL ARIE, SCHEEPSWERF VAN DE GIESSEN B V, DEN UIL, ARIE, SCHEEPSWERF VAN DE GIESSEN B.V.
Application year: 1999
Main classification: B63H5
IPC codes: B63H5