EA023077B1 - Propeller screw - Google Patents

Abstract

The invention can be used as a propulsive device for surface ships, submarine ships, aircrafts, airboats, air-cushion vessels. To decrease the cavitation effect on the propeller screw during operation by creating blade protection constituted by a laminar liquid flow, each blade of the propeller screw is made with additional cutwaters on the front surface of the blade in the direction of movement thereof from the leading edge of the propeller.

Description

The invention can be used as a propulsion device for surface, underwater and aircraft, airplanes, hovercraft.

Known propellers, which are a ship propulsion - special vessel mechanisms that create a driving force, or useful traction, which is necessary to overcome the environmental resistance of the movement of the vessel and to ensure its forward movement. They convert the energy of rotation of the propeller shaft, associated with the main engines and ship propulsion, into the energy of the forward motion of the vessel (A.M. Basin Propulsion and controllability of ships. Part 2. Ship propulsion. M., Transport, 1964). The main characteristics of the propellers are the number of blades, their shape, the angle of rotation of the blades away from the plane of the screw, dimensions, materials from which they are made, etc.

The drawback of all known propellers is still the effect of cavitation during their operation and, as a result, a noisy move that increases with increasing speed of the vessel, loss of power, rapid wear of the blades. When the liquid is subjected to pressure below the threshold (tensile stress), then the integrity of its flow is violated and vaporous cavities are formed. This phenomenon is called cavitation. The local liquid pressure at a certain point drops below the value corresponding to the saturation pressure at a given ambient temperature, the liquid goes into another state, forming mainly phase voids, which are called cavitation bubbles. The physical process of cavitation is close to the process of boiling a liquid. During cavitation, the average liquid pressure is higher than the saturated vapor pressure, and the pressure drop is local in nature. The leading role in the formation of bubbles during cavitation is played by the gases released into the resulting bubbles. These gases are always contained in the liquid and, with a local decrease in pressure, begin to be intensively released inside these bubbles. Since the bubbles can contract and expand sharply under the influence of variable local liquid pressure, the gas temperature inside the bubbles varies widely and can reach several hundred degrees Celsius. There is calculated data that the temperature inside the bubbles can reach 1500 ° C. The gases dissolved in the liquid contain more oxygen as a percentage than in air, and therefore the gases in the bubbles during cavitation are chemically more aggressive than atmospheric air.

The occurrence of cavitation cavities on the propeller blades leads to a change in its hydrodynamic characteristics and to erosive destruction of the blades, accompanied by sound radiation in a wide spectrum of frequencies. Arising in free vortices coming from the ends of the blades and the hub of the propeller, with an increase in the speed of the vessel, cavitation propagates along the suction side of the blades from their ends to the root. Initially, cavitation covers only part of the width of the blade near the incoming edge or in the region of its greatest thickness. As the velocity increases further (cavitation decreases), cavitation cavities propagate along the chord of the blade and, at a certain speed, capture the blade completely. At high speeds, the caverns extend beyond the limits of the blade. If the screw operates in an uneven flow, cavitation flashes are possible on the discharge side. The modes in which caverns cover only part of the surface of the blade and close on it are not accompanied by a change in the action curves of the screw and are called the first stage of cavitation. At this stage, erosion is most likely to occur. With a more intensive development of cavitation due to the deterioration of the hydrodynamic quality of the profiles and the restriction of the flow by caverns, the stop, torque and efficiency of the screw are reduced. These modes correspond to the 2nd stage of cavitation. When caverns extend beyond the limits of the blade, they are sometimes called supercavitation. To avoid cavitation of the blades, when designing the propellers, the disk ratio of the screw is increased.

The technical result of the invention is to reduce the effect of cavitation on the propeller during operation by creating a blade protection from the laminar fluid flow.

The technical result is achieved due to the fact that in the propeller containing the coupling, blades attached to it (from one or more) with a working edge, each of the blades is made with additional water cutters located on the front surface of the blade in the direction of its movement from the working edge of the screw .

In FIG. 1 shows a general view of a four-blade propeller, moreover, we note that a propeller with any number of blades could be represented here; FIG. 2 - working edge of the screw, front view.

Rowing screw (Fig. 1), consisting of blades 1 (from one or more), rigidly attached to the coupling, mounted on the end of the propeller shaft 2. This technical solution can be used for propellers with any number of blades. On the front plane of the blades 1 from its front working edge are water cutters 3 in the direction of movement of the blades so that they create guides for the flow of the flowing fluid around them freely. The edge of the water cutter 3 is pointed (Fig. 2), it is also working and is designed to cut off a part of the liquid medium adjacent to the working edge of the blade 1 of the formation 1 layer and give it the direction of unhindered movement along the guide vanes. In FIG. 1 and 2 schematically depict only four water cutters 3 on each blade. The optimal number of water cutters, their shape and location on the surface of the blade for each mushroom screw, depends on the type of blade, on its size and set speed

- 1 023077 characteristics of the vessel.

The propeller operates as follows. A screw, consisting of a coupling and blades attached to it with a number of 1 or more, is mounted on the end of the propeller shaft 2, driven into rotation by a marine engine. When the screw rotates, each blade due to its slope will throw water back; the reaction of this discarded water makes the ship move. At the same time, the edge of the water cutter cuts off a part of the liquid that is adjacent to the blade edge of the blade 1 of the formation of the aqueous medium and gives it the direction of unhindered movement along the blade guides formed by the water cutters 3. The surface of the blade is wrapped in a uniform layer of liquid, which becomes protection against cavitation and reduces its effect on the surface of the blade.

Claims (1)

CLAIM Propeller containing a coupling (2) with at least one blade (1) attached to it, whose working surface contains at least three water cut (3) in the direction of movement of the working edge of the blade (1), characterized in that the ridge (3 a) water cut is formed from the intersection from two sides of gentle arcs of conjugation with the surface of the blade, and the height of the ridge increases in the direction from the edge of the blade (1) to the coupling (2).