RU2531990C2 - Screw propeller life extension - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to ship repair and can be used for whatever type of propeller screws made of different materials. Screw propulsor life extension comprises measurement of actual geometrical parameters of propeller screw, calculation of the range of departure of said parameters by correction of operating parameters of propulsive complex.

EFFECT: longer life.

1 dwg

Description

The invention relates to the field of ship repair and can be used for all types of propellers made of various materials.

A known method of extending the life of propellers with geometric parameters that do not correspond to the design and specified by the drawing of the propeller, such as correcting geometric parameters by welding (1), (2).

The disadvantage of this method is the presence of welding stresses and the need for subsequent heat treatment or mechanical stress to relieve welding stresses. In addition, mechanical grinding of the welding site is required, and in the repair zone A of the propeller blade, welding is prohibited.

The problem solved by the claimed invention is a method for calculating the range of deviations of the geometric parameters of the propeller, which extends the life of the propeller by correcting the operational characteristics of the propulsion system, based on the actually measured geometric parameters of the propeller.

The essence of the claimed invention lies in the fact that they measure the geometric parameters of the propeller with the subsequent calculation of the correction of the operational characteristics of the propulsion system, allowing to extend the life of the propeller.

The proposed method is new: the difference from the prototype is the elimination of welding operations. The set of essential features of the invention leads to a new technical result - reducing the complexity, cost of repair and extending the life of the propellers.

The invention is illustrated by calculating the mass and propulsive characteristics depending on the deviations of the geometrical parameters of the propeller from the nominal values using the dependences derived by mathematical analysis, which allow a quantitative assessment of operational characteristics with known deviations of the radius of the propeller radius δ _R , as well as the length, pitch and thickness of the cylindrical sections propeller blades.

It is known that when the propeller geometry differs from the calculated one, the power plant and propulsion mismatch. The propeller, correctly designed for rated conditions, at the maximum speed of rotation, the highest power of the power plant is selected. The efficiency of such a propeller is higher in comparison with both a hydrodynamically heavy and a hydrodynamically light propeller. In the case of using a hydrodynamically heavy propeller, a shortage of revolutions and power occurs, while with a hydrodynamically light propeller, the nominal revolutions are selected, however, the consumption of the rated power and the achievement of the necessary stop are not ensured. Thus, the proposed calculation of the efficiency, emphasis, speed of the vessel and the maximum rotational speed of the propeller allows you to quantify their change from the nominal and draw a conclusion on the extension of the life of the propeller.

The calculation sequence is performed in the following order:

по формуле $$K_{n_T}=\frac{K_{T_0}}{J_0^2}\text{, }\left(\text{1}\right)$$

1. Determine the constant $$K_{n_T}$$

according to the formula $$K_{n_T}=\frac{K_{T_0}}{J_0^2}\text{,}\left(\text{one}\right)$$

- коэффициент упора гребного винта на рабочем режиме при номинальной геометрии;Where $$K_{T_0}$$

- propeller thrust coefficient in operating mode at nominal geometry;

J ₀ - propeller tread in operating mode with nominal geometry.

2. Build a parabola $$K_T=K_{n_T}\cdot J^2,$$

where K _T is the coefficient of emphasis;

J - working tread of the propeller.

по точке пересечения кривой $$K_{T_i}\left(J\right)$$

и параболы $$K_{n_T}\cdot J^2$$

.3. Determine the relative gait J _i and the coefficient of emphasis $$K_{T_i}$$

at the intersection of the curve $$K_{T_i}\left(J\right)$$

and parabolas $$K_{n_T}\cdot J^2$$

.

при известной поступи J_i с использованием кривой $$K_{Q_i}\left(J\right)$$

.4. Find the value of the moment coefficient $$K_{Q_i}$$

with a known step J _i using a curve $$K_{Q_i}\left(J\right)$$

.

:5. Determine the value of the maximum speed $$n_{n\mathrm{about}{m}_i}\left(\mathrm{one}/c\right)$$

:

$$K_{Q_i}{n}_{n\mathrm{about}{m}_i}^2=K_{Q_0}{n}_{n\mathrm{about}{m}_0}^2\text{.}\left(\text{2}\right)$$

6. The full speed V _i (m / s) is determined by the formula:

$$V_i=J_i\cdot n_{n\mathrm{about}{m}_i}\cdot D_0\text{,}\left(\text{3}\right)$$

where D ₀ is the diameter of the propeller.

7. The efficiency η of the propeller is expressed as:

$${\eta }_i=\frac{J_i}{2\pi }\frac{K_{T_i}}{K_{Q_i}}\text{.}\left(\text{four}\right)$$

Propeller action curves are shown in the drawing.

The obtained values of speed, efficiency allow us to determine their relative change from the nominal values. The magnitude of the relative changes in efficiency and speed allow us to conclude that the actual geometric parameters of the propeller correspond to the required operational characteristics. The range of deviations of the geometric parameters of the propeller is calculated as the difference between the actual geometric parameters of the propeller and the nominal geometric parameters.

Thus, the proposed method for calculating the range of deviations of the geometric parameters of the propeller allows you to extend the life of the propeller, guarantee its reliability, reduce the complexity and cost of restoring the propeller due to the complete or partial refusal to repair by welding based on the above method.

Information sources

1. OST5R.9782-2004. Copper-based alloy propellers. Correction of defects and damage. Typical technological process.

2. RD5.UEIA.3369-2003. Steel propellers. Elimination of defects and damage. Typical technological process.

Claims (1)

A method for extending the life of a propeller, including measuring the actual geometric parameters of the propeller, calculating a range of deviations of the geometric parameters of the propeller from the nominal ones and correcting the geometric parameters of the propeller by correcting the operational characteristics of the propulsion system.