Method for installing energy-saving pre-rotating guide vane in front of marine propeller

Abstract

The invention provides a method for installing an energy-saving pre-rotating guide vane in front of a marine propeller, and relates to the technical field of propeller energy-saving guide vane installing.The method comprises the steps that data collection is conducted, specifically, pod propeller flow field data is collected; calculating the circumferential distribution position of the guide vane; and calculating the radial angle of the guide vane installation. According to the method, the defects of the background technology can be effectively improved and overcome, firstly, the pre-rotating guide vanes are arranged according to a certain circumferential angle, the influence of the vanes on the axial speed field in front of the propeller is small, and in other words, the propeller design can be well matched with the flow field behind the ship after the guide vanes are additionally installed; secondly, due to the fact that the blades are short and thin, the wet surface area in contact with water is small, and generated resistance is small; and finally, the energy-saving guide vane in front of the propeller mainly utilizes the characteristics of a tangential velocity field and is matched with an inflow triangle of the propeller to carry out customized design, the thin, few and short blades reduce the influence on resistance increase and the axial velocity field, and meanwhile, the propelling efficiency can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of propeller energy-saving guide vane installation, and more specifically, relates to a method for installing energy-saving pre-rotation guide vanes in front of a marine propeller. Background Art

[0002] At present, energy conservation and carbon reduction are important measures to promote global green environment construction and promote global economic and social development. The shipping industry is an important part of global trade, and its carbon emissions account for a certain proportion of the global total emissions. Ships are important means of transportation for shipping. If the carbon emissions of ships during operation can be effectively controlled, it will have a positive significance for the global energy conservation and carbon reduction cause. During the operation process, if the power of the ship's main engine can be effectively reduced while maintaining the transportation efficiency and duration, it can achieve energy-saving effects.

[0003] In recent years, research on water power energy saving has developed rapidly, and its advantages are as follows: First, improve propulsion efficiency. After installing the hydrodynamic energy-saving device, under the same speed conditions, the propulsion power required for the ship to sail in the water is less than that before the hydrodynamic energy-saving device is installed; Second, it does not change the original internal structure of the hull. The hydrodynamic energy-saving device is usually installed on the outer plate of the hull, which does not change the internal structure of the hull. It is easy to install and construct; Third, low input and high output. Usually the price of a water-powered energy-saving device is less than 500,000 yuan. Ideally, it can save 300,000 to 2 million yuan in fuel costs each year, and the cost can be recovered in one to two years.

[0004] The current hydrodynamic energy-saving devices can be divided into propeller-front hydrodynamic energy-saving devices and propeller-rear hydrodynamic energy-saving devices according to their relative relationship with the propeller. The function of the propeller-front energy-saving device is to guide the propeller-front flow field to be used more efficiently by the propeller, such as the wake compensation duct. The wake compensation duct is a propeller-front energy-saving device installed at the stern and above the propeller shaft. It consists of two asymmetric acceleration-type semicircular ducts. Its main energy-saving principle is to guide the stern flow field (axial velocity), improve the axial velocity distribution of the propeller inlet surface, and improve the propeller efficiency. The duct can generate additional thrust for ship propulsion.

[0005] However, in actual use, it is found that the propeller-front hydrodynamic energy-saving device has disadvantages: 1. The flow field matching is not good. The flow field around the hull is an unsteady motion flow field, that is, the velocity field of the flow field changes with time. Since the wake compensation duct usually accelerates a large range of flow field areas, it is difficult to accurately control the flow in the duct; 2. Increased resistance. Although the duct will theoretically increase thrust, the suction effect of the propeller will accelerate the flow separation at the trailing edge of the duct. If the design is not good, it will cause a large increase in resistance, and the energy-saving effect will consume energy instead; 3. The energy of the tangential velocity is not effectively utilized. Due to the existence of the hull, there must be tangential velocity in the velocity field at the stern. Theoretically, when the tangential velocity is zero or even negative, the efficiency of the propeller will be improved. However, the wake compensation duct only increases the axial velocity and does not effectively utilize the tangential velocity energy, so the improvement in propulsion efficiency is limited.

[0006] In order to solve the above problems, we propose a method for installing energy-saving pre-rotation guide vanes in front of a marine propeller to solve the above problems. Summary of the invention

[0007] The present invention aims to overcome the deficiencies of the prior art and to provide a method for installing energy-saving pre-swirl guide vanes in front of a marine propeller.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides a method for installing energy-saving pre-rotation guide vanes in front of a marine propeller, comprising the following steps: S1. Data collection: collecting pod propeller flow field data; S2. Calculate the circumferential distribution position of the guide vanes: Take point A, the location information of A is , assuming that the plane is the guide vane inlet surface, the velocity at point A is: (1) Where x is a unit vector perpendicular to the plane, is the tangential unit vector in the plane, r is the radial unit vector in the plane, assuming that, , It is a small amount and can be ignored; Assume that the tangential velocity of the water flow caused by the propeller rotation is set to: ; ; search Use energy-saving guide vanes to form Condition; By numerical calculation method CFD, the flow surface is calculated and the tangential velocity matrix is ​​obtained. Radial: (2) Pick Each column as an array Find the average value of an array and evaluate the circumferential direction Distribution or The situation is used as the main basis for the circumferential distribution angle; S3. Calculate the radial angle of the guide vane installation: Radial (3) Take a column of circumferential values ​​that have been determined in step S2; n radially; At each radial direction; (4) After designing the arch line, each radial position can be formed; (5) The arch line and radial installation angle of the guide vane can be obtained by calculation; S4, according to the calculated structure in steps S2 and S3, the guide vanes are customized and designed and manufactured; S5. Weld and fix the energy-saving blades.

[0009] The present invention has the following beneficial effects: By installing the energy-saving pre-swirl guide vanes according to the method of the present invention, the shortcomings of the background technology can be effectively improved and solved. First, the pre-swirl guide vanes are composed of 3-4 thinner blades arranged at a certain circumferential angle, and the guide vanes have little effect on the axial velocity field in front of the propeller, that is, the propeller design can better match the flow field behind the ship after the guide vanes are installed; secondly, because the guide vanes are shorter and thinner, the wet surface area in contact with water is small, and the resistance generated is smaller; finally, the energy-saving guide vanes in front of the propeller mainly utilize the characteristics of the tangential velocity field and are customized in combination with the inlet triangle of the propeller. The thinner, fewer and shorter guide vanes reduce the influence on the increased resistance and the axial velocity field, and can greatly improve the propulsion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a structural diagram of guide vane installation in the present invention; Figure 2 It is a diagram defining the circumferential and radial directions in the present invention; Figure 3 It is a tangential flow field cloud diagram before and after the guide vanes are installed in the present invention; Figure 4 Schematic diagram of radial and circumferential distribution of the tangential velocity field in front of the propeller in the present invention; Figure 5 It is a schematic diagram of a radial section of a sample data taken in the present invention; Figure 6 This is a comparison diagram of the tangential drainage effect of the energy-saving guide vane in the present invention; Figure 7 It is a schematic diagram of the pre-spin effect and energy-saving effect in the present invention; Figure 8 This is the energy-saving effect of different blade angles in the present invention. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] See also Figure 1 - Figure 8 The present invention provides a method for installing energy-saving pre-rotation guide vanes in front of a marine propeller, comprising the following steps: S1. Data collection: collecting pod propeller flow field data; S2. Calculate the circumferential distribution position of the guide vanes: Take point A, the location information of A is , assuming that the plane is the guide vane inlet surface, the velocity at point A is: (1) Where x is a unit vector perpendicular to the plane, is the tangential unit vector in the plane, r is the radial unit vector in the plane, assuming that, , It is a small amount and can be ignored; Assume that the tangential velocity of the water flow caused by the propeller rotation is set to: ; ; search The use of energy-saving guide vanes Condition; By numerical calculation method CFD, the flow surface is calculated and the tangential velocity matrix is ​​obtained. Radial: (2) Pick Each column as an array Find the average value of an array and evaluate the circumferential direction Distribution or The situation is used as the main basis for the circumferential distribution angle; S3. Calculate the radial angle of the guide vane installation: Radial (3) Take a column of circumferential values ​​that have been determined in step S2; n radially; At each radial direction; (4) After designing the arch line, each radial position can be formed; (5) The arch line and radial installation angle of the guide vane can be obtained by calculation; S4, according to the calculated structure in steps S2 and S3, the guide vanes are customized and designed and manufactured; S5. Weld and fix the energy-saving blades.

[0013] In this embodiment, reference Figure 1 - Figure 2 As shown, by installing energy-saving pre-swirl guide vanes in front of the propeller, the shortcomings of the background technology can be effectively improved and solved. First, the energy-saving pre-swirl guide vanes have 3-4 thin blades arranged at a certain circumferential angle. The energy-saving pre-swirl guide vanes have little effect on the axial velocity field in front of the propeller, that is, the propeller design can better match the flow field behind the ship after the energy-saving pre-swirl guide vanes are installed; secondly, because the energy-saving pre-swirl guide vanes are shorter and thinner, the wet surface area in contact with water is small, and the resistance generated is small; Finally, the energy-saving pre-swirl guide vanes in front of the propeller mainly utilize the characteristics of the tangential velocity field and are customized in combination with the propeller's inlet triangle. The thinner, fewer, and shorter blades reduce the impact on increased drag and axial velocity field, while greatly improving propulsion efficiency.

[0014] This patent adopts an energy-saving pre-rotation guide vane in front of the propeller. The guide vane is a stator component. Through the drainage effect of the guide vane blades, the propulsion efficiency of the propeller is improved, thereby achieving energy-saving effects.

[0015] refer to Figure 1 As shown in the figure, the components that the water flows through are divided into three categories: Component No. 0, the stern, Component No. 1, the stator energy-saving guide vane, and Component No. 2, the rotor propeller (right-hand rotation). First, the water flows through the stern outer plate to form a velocity distribution field in front of the stator. After the blade design of the stator, the water flow is guided to form a velocity distribution field behind the stator that is conducive to the propeller inflow. The distance between the rear of the stator and the front of the rotor is small, and the change in the velocity distribution field can be ignored, that is, the velocity field distribution behind the stator is the same as the velocity field distribution in front of the rotor. This velocity distribution field is the optimal inflow velocity distribution field for the rotor, which can be efficiently used by the rotor to improve the propulsion efficiency.

[0016] refer to Figure 3 As shown in the figure, the tangential velocity field of the hull in front of the propeller. The left figure is the velocity field without energy-saving guide vanes, and the right figure is the velocity field with energy-saving guide vanes installed. By comparison, it can be found that after the pre-swirl guide vanes are installed, the tangential wake velocity that is unfavorable to the propeller efficiency is changed (positive value), and its negative value remains unchanged.

[0017] refer to Figure 4The figure shows the mechanism of the energy-saving pre-rotating guide vane in front of the propeller of this patent: the tail of the hull is a large curvature surface, and the fluid flows through the surface of the hull and converges in front of the propeller. Since the hull has left-right symmetry, the tangential flow field caused by it must have positive and negative velocities. By analyzing the tangential velocity field, the tangential velocity distribution curves in different radial and circumferential directions can be obtained. The curves are analyzed and calculated to determine the circumferential arrangement angle and radial arrangement height of the guide vane (the guide vanes in the figure have different circumferential angles and the same radial angle, and this patent can change these two variables). Through the blade surface of the pre-rotating guide vane, the positive tangential velocity that is unfavorable to the efficiency is guided into the negative tangential velocity that is favorable to the efficiency, so as to change the inlet angle of the propeller and improve the propeller's propulsion efficiency.

[0018] refer to Figure 5 As shown, a radial section is taken to illustrate the technical effect: The velocity at the stern of component No. 0 is V0, and when it flows to the leading edge of the stator blade section of component No. 1, the velocity is decomposed into an axial velocity V0_axial and a tangential velocity V0_tangential. At this time, the tangential velocity is directed downward, and the fluid changes into a velocity V1 in the middle of the guide vane and a velocity V2 at the trailing edge of the stator section as the guide vane drains. The velocity V2 is decomposed into an axial velocity V2_axial and V2_tangential. At this time, according to the drainage effect of the guide vane, the tangential velocity of V2_tangential is directed upward, achieving a "pre-rotation" effect.

[0019] V3_o is the inflow velocity vector of the rotor propeller of component 2 without guide vanes installed, which can be decomposed into V3_axial and V3_o_tangential. The pre-swirl velocity is formed by the drainage effect of the energy-saving guide vanes, so the tangential component of the rotor propeller profile inflow velocity after installing the energy-saving guide vanes is V3_tangential = V3_o_tangential – V2_tangential, and V3_axial forms a combined velocity V3 as the new rotor profile inflow.

[0020] According to the speed triangle theory of the propeller, the angle between the speed V3 and the horizontal direction is smaller than that between the speed V3_o. Under the condition that the geometric pitch angle (propeller geometric dimensions) remains unchanged, the hydrodynamic pitch angle required for thrust is smaller, thereby achieving the effect of improving the propeller propulsion efficiency.

[0021] refer to Figure 6-8 As shown in the figure, before and after the installation of energy-saving pre-swirl guide vanes, the tangential velocity distribution in front of the rotor changes significantly (positive values ​​are converted to negative values), which effectively plays the drainage role of the guide vanes and achieves energy-saving effects.

[0022] refer to Figure 7As shown, each line represents the energy saving effect of installing different guide vanes, among which the square line is without guide vanes, the dot line and the triangle line are 4% and 5.1% respectively. Because the flow field is non-stationary and the speed changes with time, by adjusting the overall angle of the guide vane, different energy saving effects can be calculated and optimized.

[0023] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for installing energy-saving pre-rotation guide vanes in front of a marine propeller, preferably comprising the following steps: S1. Data collection: collecting pod propeller flow field data; S2. Calculate the circumferential distribution position of the guide vanes: Take point A, the location information of A is , assuming that the plane is the guide vane inlet surface, the velocity at point A is: (1) Where x is a unit vector perpendicular to the plane, is the tangential unit vector in the plane, r is the radial unit vector in the plane, assuming that, , It is a small amount and can be ignored; Assume that the tangential velocity of the water flow caused by the propeller rotation is set to: ; ； search Use energy-saving guide vanes to form Condition; By numerical calculation method CFD, the flow surface is calculated and the tangential velocity matrix is ​​obtained. Radial: (2) Pick Each column as an array Find the average value of an array and evaluate the circumferential direction Distribution or The situation is used as the main basis for the circumferential distribution angle; S3. Calculate the radial angle of the guide vane installation: Radial (3) Take a column of circumferential values ​​that have been determined in step S2; n radially; At each radial direction; (4) After designing the arch line, each radial position can be formed; (5) The arch line and radial installation angle of the guide vane can be obtained by calculation; S4, according to the calculated structure in steps S2 and S3, the guide vanes are customized and designed and manufactured; S5. Weld and fix the energy-saving blades.

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