RU2228878C2 - Propeller - Google Patents

Abstract

FIELD: shipbuilding; manufacture of marine propellers. SUBSTANCE: proposed propeller has hub with blades connected to it and inscribed in surface having generatrix in form of parabola. Profile of blade section is formed by two parabolas engageable in area of trailing edge by semi-circumference inscribed in hub body. Leading edge of blade is rounded-off at radius not exceeding radius of said semi-circumference. Rear plane of propeller has stabilizing surface which is tangential to upper surface of propeller blade projecting above this rear plane. Coefficients of parabolas are selected from definite relationships. Hub may be additionally provided with booster blades of lesser diameter for compensation of reduction of water pressure on main blades. EFFECT: increased thrust of propeller; reduced level of noise and suppression of cavitation. 2 cl, 3 dwg

Description

The essence of the invention is the creation of a propeller blade and, based on it, a propeller having improved power characteristics with less noise effect and reduced cavitation.

A propeller is proposed, the blade profile of which represents the intersection of two parabolas: Y ₁ = K ₁ X ^1/2 and Y ₂ = K ₂ X ^1/2 + 2R, the shape of the blades is inscribed in the parabola Y ₁ = K ₁ X ^1/2 in rectangular Cartesian coordinates.

Two parabolas Y ₁ and Y _{2 are in} contact on the Y axis with a semicircle of radius R - the trailing edge. The leading edge is rounded at a distance R from the point of intersection of the parabolas of radius R _q ≤ R to improve streamlining.

The propeller blade has a stabilizing plane that is tangent to the upper plane of the screw and serves to reduce noise and cavitation.

The invention relates to the field of shipbuilding, to the construction of propellers used as ship propulsors.

In the propeller adopted for the prototype (1) containing the hub, the blades of a convex-concave section with a helical surface of a cup-shaped form, the following disadvantages should be noted:

- the shape of the blades is cup-shaped, which does not provide the necessary focusing of the flow;

- the blades extend beyond the hub by 1/3 of the length, as a result of which they participate little in increasing the power of the flow;

- the cross section of the blades is linear (a plane of a certain thickness), which leads to a heavier structure while ensuring the necessary strength;

The invention is intended to increase propeller thrust while reducing noise and cavitation.

The technical result is achieved due to the fact that the profile of the propeller shaft blades is formed by the intersection of two parabolas: Y ₁ = K ₁ X ^1/2 and Y ₂ = K ₂ X ^1/2 + 2R, Fig. 1, and the shape of the blades fits into the parabola Y ₁ = K ₁ X ^1/2 , Fig. 2 (3).

Two parabolas are in contact on the Y axis with a semicircle of radius R - the trailing edge, which fits into the body of the hub, creating the necessary strength, Fig. 1 (2).

The leading edge has a rounded radius R _q <R _i at a distance R _i from the point of intersection of the parabolas to improve streamlining, Fig. 1 (1).

The current coordinate of the point of intersection of the parabolas on the axis XL _i and the current radius R _i are found from the formulas

where R _0i is the current length of the propeller blade in meters on the hub. The countdown is from the origin.

The coefficients are selected from the following values:

K =>1; K ₁ =>0.5; K ₂ = (0.1 ÷ 0.6) · K ₁ ; K ₃ <= 0.1;

In (2), it is noted that an element in the form of a plate or wedge of relatively small sizes, but not more than 0.15 chords, can be attached to the trailing edge of the profile.

The rear plane of the screw has a stabilizing plane, which is tangent to the upper (possibly lower) plane of the propeller blade and serves to reduce noise and cavitation, Fig 2 (1).

The stabilizing plane is formed by a sector of the plane with a maximum value at the end of the rear propeller blade equal to L ₀ <= R _max , and gradually decreases to zero by about 1/3 of the length of the rear plane of the propeller blade. At small radii of the screw, the bending of the aqueous medium occurs evenly, without cavitation.

The dimensions of the stabilizing plane should be chosen as the smallest, since with an increase in its area the screw efficiency drops sharply.

ROW SCREW WORK

When the propeller rotates, the blades discard water in the direction along the axis of the hub, Fig. 2 (2), which contributes to the formation of a directed flow. The implementation of the propeller blades, figure 2 (3), in the form of intersecting planes of parabolas inscribed in the parabola, figure 2 (3), contributes to the formation of a uniformly directed flow of water coming off the blades with its focus in the opposite direction of the vessel. The presence of a stabilizing plane reduces noise and cavitation.

To reduce cavitation of the propeller blade, i.e. to reduce the formation of air bubbles that occur during boiling due to a sharp drop in pressure, it is necessary to provide small additional and boost blades R _add with a maximum raster

These additional blades create an increase in water pressure on the "outgoing" main working blades, thereby to some extent reduce a sharp drop in pressure on the main blades, resulting in reduced cavitation.

To increase productivity and focus the flow, the blades themselves on the hub must be formed along the parabola Y ₀ = K ₀ X ^1/2 , where the coefficient K ₀ ≥ 0.7.

All this allows you to increase the efficiency and quality and operational characteristics of the propeller.

Comparative evaluation tests carried out on the manufactured mock-ups showed the efficiency of the proposed propeller approximately 10% higher than the known one (1) with a decrease in dimensions of approximately 30%.

The proposed propeller can be effectively used in icebreakers, where the propeller is installed in front and serves as an ice ax.

SOURCES OF INFORMATION

1. Cl. B 63 H 1/26 1/14, 1995, patent 2108265.

2. Cl. B 63 H 1/26 1999, patent 2127208.

Claims (2)

1. A rowing screw containing a hub with blades attached to it inscribed on a surface having a parabola as its generatrix, characterized in that the sectional profile of the blades is formed by the intersection of two parabolas defined in rectangular Cartesian coordinates (XY) by graphs Y ₁ = K ₁ X ^1/2 and Y ₂ = K ₂ X ^1/2 + 2R, where X and Y are the abscissa and ordinate, respectively, moreover, the parabolas mate on the Y axis with a semicircle of radius R, which forms the trailing edge and is inscribed in the body of the hub, and the leading edge has a curve of radius R _q not exceeding R, at a distance of the current radius R _i from the point of intersection of the parabolas, while the rear plane of the rowing the screw has a stabilizing surface tangent to the upper surface of the screw blade and protruding above the rear plane by an amount L ₀ not exceeding the maximum radius of the screw R _max near the trailing edge, gradually decreasing to zero by 1/3 of the width of the blade p about the back plane, while the specified parabola, forming the surface into which the blades are inscribed, is set by the schedule Y = KX ^1/2 , where the x-axis is directed along the hub, and the indicated current radius R _i and the abscissa L _i the intersection points of these parabolas satisfy the relations L _i ≈ R _0i / 2π K ₃ , R _i = L _i / K ₄ , where R _0i is the current length of the propeller blade on the hub in meters, counted from the beginning of the Cartesian coordinates, moreover, the coefficients are selected from the relations K≥1, K ₁ ≥ 0.5, K ₂ = (0.1-0.8) K ₁ , K ₃ ≤ 0.1, K ₄ ≥ 13 / K ₁ . 2. The propeller according to claim 1, characterized in that the blades are formed on the surface of the hub along a parabola Y ₀ = K ₀ X ^1/2 , where the coefficient K ₀ ≥ 0.7.

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