A method for designing the assembly layout of a water surface ship stern and water jet propeller

Abstract

This invention relates to a design method for the assembly layout of a stern section and a waterjet propulsion system for a surface vessel. The method comprises: S1, studying the characteristics of the stern section of the surface vessel and considering the assembly layout with the waterjet propulsion system, making adaptive improvements to the stern section's lifting point and cross-sectional characteristics; S2, designing a guide channel in front of the duct, with design factors including the starting position, width, and depth of the guide channel; S3, combining the propulsion system's embedded connection form and shafting layout, comprehensively considering the effects of resistance and wake field, selecting the optimal appendage scheme for the stern layout. This invention comprehensively considers propulsion strength, vibration, and flow field aspects, forming a stern structure where the duct and stern are integrated. A guide channel area is adaptively designed in front of the propulsion duct's flow field. For the shafting layout of the embedded waterjet propulsion system, a stern shaft frame scheme selection and design are carried out, resulting in a stern modification scheme, assembly scheme, and appendage scheme for the main hull with lower resistance and more uniform wake.

Description

Technical Field

[0001] This invention relates to the field of ship propulsion technology, and more specifically to a design method for the assembly layout of the stern shape and waterjet propulsion system of a surface vessel. Background Technology

[0002] Based on the installation method of the waterjet propulsion device, there are two main types: externally mounted and internally mounted, each with different shafting configurations. The externally mounted waterjet propulsion device is located over the hull and uses an axial-flow propulsion pump shafting structure, which is relatively simple. Its nozzle is placed underwater at the hull bottom, avoiding significant flow losses in the intake channel caused by the increased position and changed flow direction. This type is also known as a submersible waterjet propulsion device.

[0003] Because the connection between the externally mounted waterjet propulsion system and the hull differs significantly from that of traditional propeller propulsion, the different assembly layout at the intersection of the two will result in a complex shape and a large adjustable space at the bottom of the hull, which will have a significant impact on resistance and flow field. When adapting the two, factors such as speed, wake, shaft system layout, and appendage arrangement need to be comprehensively considered. Summary of the Invention

[0004] This invention aims to improve the design of the assembly layout of the stern shape and the externally suspended waterjet propulsion system of surface ships, and to provide support for the application of externally suspended waterjet propulsion systems. It provides a design method for the assembly layout of the stern shape and the waterjet propulsion system of surface ships. The application effect can realize the design of the waterjet propulsion system and its matching stern structure, forming a stern modification scheme, assembly scheme and appendage scheme for the main hull with low resistance and uniform wake.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for designing the assembly layout of the stern section and waterjet propulsion system of a surface vessel, comprising the following steps:

[0007] S1. Adaptive improvement of the main hull design: Study the stern characteristics of surface ships, consider the assembly layout with waterjet propulsion, and make adaptive improvements to the stern hull lifting point and cross-sectional characteristics.

[0008] S2. Design of the guide channel in front of the duct: A guide channel is designed in front of the duct. The design factors include the starting position, width and depth of the guide channel. Among them, the depth of the guide channel is the focus of rapid selection. For the embedded water jet propulsion connection, in order to achieve sufficient flow in front of the duct, guide channel schemes of different depths are designed. The influence on resistance and wake field is comprehensively considered to select the optimal guide channel scheme.

[0009] S3. Appendage selection and design for waterjet propulsion and shaft system: Combining the propulsion embedded connection form and shaft system layout, and taking into account the influence of resistance and wake field, appendage selection is carried out for the stern layout form, and the optimal appendage scheme is selected.

[0010] In the above scheme, in the improvement of the main hull scheme in step S1, the duct of the waterjet propulsion is embedded inside the main hull to form a stern structure in which the duct and the stern are integrated. In order to match the waterjet propulsion, the linear transition of the stern installation area is required to be smooth.

[0011] In the above scheme, for the preliminary scheme of the ship type with a U-shaped to V-shaped transition zone near the stern lift point in the mid-to-rear section, the stern shape of the mid-to-rear section of the ship is improved into a full U-shaped section design, and the stern lift point is moved forward to near the maximum cross section in the middle of the ship to form a stern longitudinal flow ship type.

[0012] In the above scheme, in step S2, when designing the guide channel, the influence of the flow field is considered, and the longitudinal position of the guide channel is arranged according to the streamline direction so that it is in line with the streamline.

[0013] In the above scheme, in step S2, when designing the starting position of the guide channel, the length of the guide channel and the shaft sleeve arranged in front of it are taken into account, so that the guide channel and the shaft sleeve are spaced at a certain longitudinal distance.

[0014] In the above scheme, the distance between the guide groove and the shaft sleeve is 0.01 to 0.02D, where D is the diameter of the guide tube inlet.

[0015] In the above scheme, in step S2, when designing the width of the guide channel, the width corresponding to 0.1D to 0.15D of the duct inlet embedded in the ship body is selected to ensure that the incoming flow of the embedded water jet propulsion unit is as uniform as possible, while ensuring the connection strength.

[0016] In the above scheme, in step S2, when designing the depth of the guide channel, under the condition that the starting position and width remain unchanged, guide channel schemes with different depths are designed. Based on the rapid numerical simulation method, the influence of depth change on ship resistance and the wake flow on the rotor disk at the guide is analyzed, and the guide channel scheme is designed and selected.

[0017] In the above scheme, in step S3, the support arm is selected, and two types of shaft support are designed, namely single-arm and double-arm shaft support. For the above two appendage schemes, a full appendage rapid numerical simulation model is established based on the rapid numerical method. The effects of single-arm and double-arm shaft support on ship resistance and wake flow at the duct inlet are compared, the corresponding results are analyzed, and the support type is selected.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention, based on an externally suspended submersible waterjet propulsion system, proposes a design method for the assembly layout of the stern section and waterjet propulsion system of a surface vessel. Taking into account factors such as propulsion strength, vibration, and flow field, a stern structure integrating the duct and stern is formed. A guide channel area is adaptively designed in front of the propulsion duct flow field. For the shaft system layout of the embedded waterjet propulsion system, a stern shaft bracket scheme is selected and designed. The application results enable the design of waterjet propulsion systems and matching stern structures, resulting in a main hull stern modification scheme, assembly scheme, and appendage scheme with lower resistance and more uniform wake. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0021] Figure 1 This is a comparison of the side views of the mid-to-aft section hull lines of the ship before and after the improvement in this embodiment of the invention;

[0022] Figure 2 This is a schematic diagram of the assembly of the externally suspended waterjet propulsion device in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the guide groove and shaft sleeve area in an embodiment of the present invention;

[0024] Figure 4 These are schematic diagrams of guide grooves at different depths in embodiments of the present invention;

[0025] Figure 5 These are schematic diagrams of single-arm and double-arm shaft support schemes in embodiments of the present invention. Detailed Implementation

[0026] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the specific implementation of this invention will now be described with reference to the accompanying drawings, taking the layout design of a surface vessel and an externally suspended waterjet propulsion system as an example.

[0027] This invention focuses on submersible waterjet propulsion, conducting a rapid optimization study of the stern shape and propulsion assembly area of ​​surface vessels. The assembly layout parameters include the stern shape lifting point and cross-sectional shape, guide channel depth and width, starting position, and appendage type. The specific implementation steps are as follows:

[0028] S1. Adaptive Improvement of Main Hull Design: Study the stern characteristics of surface vessels, consider the assembly layout with waterjet propulsion, and make adaptive improvements to the stern hull lifting point and cross-sectional characteristics.

[0029] The flow-through components of a waterjet propulsion system include a rotor, a stator, and ducts. This invention proposes embedding the ducts of the waterjet propulsion system inside the main hull, forming a stern structure where the ducts and stern are integrated. This assembly layout provides structural support for the propulsion system and also reduces its vibration. To match the propulsion system, a smooth transition in the stern mounting area is required, necessitating an improved design of the stern profile.

[0030] like Figure 1 As shown in the preliminary hull design, the mid-to-aft section transverse section exhibits a transition zone from U-shape to V-shape near the stern lift point. This area shows a twist in the transverse section towards the bilge, with drastic changes in hull shape. Furthermore, the stern lift point is relatively far aft, approximately near station 16, resulting in a large vertical gradient during stern lift and drastic changes in stern lift, which is detrimental to propeller duct assembly.

[0031] The above-mentioned mid-to-rear section linear characteristics will, on the one hand, increase the turbulence intensity of the stern flow field, and on the other hand, may lead to flow separation in the stern flow field, which will not only increase drag, but also have an adverse effect on the uniformity of the stern flow field.

[0032] In response to the above problems, such as Figure 1 , Figure 2 As shown, in this embodiment, the stern shape of the mid-to-rear section of the ship adopts a full U-shaped section design, and the stern lifting point is moved forward to near the maximum transverse section in the middle of the ship to form a longitudinal flow hull shape. This makes the mid-to-rear section of the ship's line shape transition smoothly, which is conducive to the installation of the propeller and can also achieve the effects of drag reduction and improvement of the stern flow field.

[0033] S2. Design of the Guide Channel in Front of the Duct: Since the duct is embedded inside the main hull, the outer plating at the stern will have a certain impact on the inlet and outlet flow fields of the duct. To ensure sufficient flow in front of the duct, a guide channel needs to be designed in front of the duct to reduce "water blockage." When designing the guide channel, the influence of the flow field is considered, and its longitudinal position is arranged according to the streamline direction to ensure it aligns with the streamline. Design factors for the guide channel scheme include the starting position, width, and depth of the guide channel.

[0034] At the starting position of the guide channel, a shaft sleeve is arranged in front of the guide channel. Therefore, the hull surface near the shaft sleeve and the guide channel forms a "convex-concave" curvature change. If their longitudinal positions overlap, it can easily lead to complex vortex flow field phenomena. Therefore, the lengths of both are selected to ensure a certain longitudinal distance between them. Figure 3 As shown, the preferred value is 0.01 to 0.02D, where D is the diameter of the catheter inlet.

[0035] Regarding the width of the guide channel, since the thruster is an embedded connection, to ensure that the incoming flow to the thruster is as uniform as possible, the current selection is a width corresponding to 0.1D to 0.15D of the guide channel inlet embedded in the hull. When the width is further increased, the "water blockage" phenomenon becomes more serious, resulting in insufficient water intake and a decrease in the hydrodynamic performance of the thruster. If the embedded width is too small, it is not easy to ensure the connection strength.

[0036] Since the adjustment margin for the starting position and width of the guide channel is small, the focus is on the rapid selection of the depth of the guide channel. With the starting position and width unchanged, guide channel schemes with different depths are designed. Based on the rapid numerical simulation method, the influence of depth change on ship resistance and the wake flow on the rotor disk at the guide duct is analyzed, and the guide channel scheme is designed and selected.

[0037] In this embodiment, for the embedded thruster connection, two guide groove schemes with different depths are designed to ensure sufficient flow in front of the duct. A comparison diagram of the schemes is shown below. Figure 4 As shown. The depths of the middle region of the guide channel scheme from the axis are 0.35D (Scheme 1) and 0.40D (Scheme 2), respectively. The guide channel schemes of different depths are compared in terms of resistance and wake flow. The resistance comparison between the two schemes is as follows:

[0038] Table 1. Resistance Coefficients for Model-Scale Guide Channel Selection

[0039] plan Fr Vm(m / s) <![CDATA[Ct×10 -3 ]]> Option 1 0.2236 1.793 3.872 Option 2 0.2236 1.793 3.908

[0040] The following is a comparison of the accompanying currents:

[0041] Table 2. Three-dimensional average wake fraction table

[0042]

[0043] The table above shows the three-dimensional average wake fraction. As can be seen, the radial and tangential average wake fractions are much smaller than the axial average wake fraction. Therefore, the influence of the axial average wake should be the primary consideration when selecting a guide channel. Since the deepening scheme results in higher resistance and a smaller axial wake fraction, considering both resistance and the wake field, Scheme 1 is the preferred option for guide channel selection.

[0044] S3. Appendage selection and design for waterjet propulsion and shaft system: Combining the propulsion embedded connection form and shaft system layout, and taking into account the influence of resistance and wake field, appendage selection is carried out for the stern layout form, and the optimal appendage scheme is selected.

[0045] Because the waterjet propulsion unit is installed at a relatively high position, the tilt angle of its axis is smaller. Consequently, the position of the propeller shaft exiting the main hull is moved further back, and the distance from the propeller shaft exit point to the center of the propeller disk is shortened. Moreover, since the stator and guide tubes are embedded inside the hull, they can provide strength support for the propulsion unit. Therefore, according to the shaft system analysis, only one shaft support is required. Compared to the conventional propeller assembly scheme, the waterjet propulsion unit reduces the number of shaft supports by one pair.

[0046] For the selection of support arms, from Figure 3 As can be seen, the longitudinal position of the shaft support overlaps with the position of the guide channel. Considering the ship's hull shape characteristics in the guide channel area, two types of shaft supports were designed: single-arm and double-arm shaft supports, as shown below. Figure 5 As shown in the figure. For the two appendage schemes mentioned above, a full appendage speed numerical simulation model was established based on the speed numerical method. The effects of single and double-arm shaft support forms on ship resistance and wake flow at the duct inlet were compared. The drag coefficients of the two support schemes at low speed Fr = 0.2236 and high speed Fr = 0.3726 are shown in the table below.

[0047] Table 3. Model Scale Support Arm Selection Resistance Coefficient Table

[0048]

[0049] As can be seen from the table above, the resistance of a single-arm support is less than that of a double-arm support, meaning that the resistance performance of a single-arm support is better than that of a double-arm support.

[0050] The following is a comparison of the flow tracing results for single-arm and double-arm support structures.

[0051] Table 4. Three-dimensional average wake fraction

[0052]

[0053] Table 5 Comparison of Axial Non-uniformity

[0054] Axial flow nonuniformity single-arm support 0.3223 Dual-arm support 0.3283

[0055] The table above shows the three-dimensional average wake fractions for the two types of supports. It can be seen from the table that the radial and tangential average wake fractions are much smaller than the axial average wake fraction. Focusing on the influence of axial wake, the single-arm support has a larger axial average wake fraction than the double-arm support, and its axial wake non-uniformity is less than that of the double-arm support. Therefore, the wake effect of the single-arm support is slightly better than that of the double-arm support. Considering both resistance and the wake field, the preferred option for support arm selection is the single-arm support.

[0056] This embodiment takes the externally suspended waterjet propulsion system as the research object and proposes an assembly layout design method suitable for the stern shape and waterjet propulsion system of surface ships, taking into account the connection form of the waterjet propulsion system duct and the main hull. A stern structure with the duct and the stern integrated is formed. Considering the influence on the flow field, a guide channel is designed in front of the duct flow. According to the propeller shaft arrangement, a unique stern appendage of the embedded waterjet propulsion system is formed, realizing the design of the waterjet propulsion system and its matching stern structure.

[0057] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for designing the assembly layout of the stern shape and waterjet propulsion system of a surface vessel, characterized in that, Includes the following steps: S1. Adaptive improvement of the main hull design: Study the stern characteristics of surface vessels, consider the assembly layout with waterjet propulsion, and make adaptive improvements to the stern hull lifting point and cross-sectional characteristics. Embed the waterjet propulsion duct into the main hull to form a stern structure in which the duct and the stern are integrated. In order to match the waterjet propulsion, the linear transition of the stern installation area is required to be smooth. S2. Design of the guide channel in front of the duct: A guide channel is designed in front of the duct. Considering the influence of the flow field, the longitudinal position of the guide channel is arranged according to the streamline direction to make it flow with the streamline. The design factors include the starting position, width, and depth of the guide channel. When designing the starting position of the guide channel, the length of the guide channel and the shaft sleeve arranged in front of it are comprehensively considered, so that the distance between the guide channel and the shaft sleeve is 0.01~0.02D, where D is the diameter of the duct inlet. When designing the width of the guide channel, the width corresponding to the duct inlet being embedded in the hull is selected as 0.1D~0.15D. When designing the depth of the guide channel, with the starting position and width unchanged, guide channel schemes with different depths are designed. Based on the rapid numerical simulation method, the influence of depth change on ship resistance and the wake flow on the rotor disk at the guide is analyzed, and the optimal guide channel scheme is selected. S3. Appendage selection and design for waterjet propulsion and shaft system: Combining the propulsion embedded connection form and shaft system layout, and taking into account the influence of resistance and wake field, appendage selection is carried out for the stern layout form, and the optimal appendage scheme is selected.

2. The method for designing the assembly layout of the stern shape and waterjet propulsion system of a surface vessel according to claim 1, characterized in that, For the initial design of a ship type with a U-shaped to V-shaped transition zone near the stern lift point in the mid-to-rear section, the stern shape in the mid-to-rear section is improved to a full U-shaped section design, and the stern lift point is moved forward to near the maximum cross section in the middle of the ship, forming a stern longitudinal flow ship type.

3. The method of designing the arrangement of a water surface vessel stern and a water jet propeller according to claim 1, characterized in that, In step S3, the selection of support arms is carried out, and two types of shaft support are designed, namely single-arm and double-arm shaft support. For the above two attachment schemes, a full attachment rapid numerical simulation model is established based on the rapid numerical method. The effects of single-arm and double-arm shaft support on ship resistance and wake flow at the duct inlet are compared, the corresponding results are analyzed, and the support type is selected.

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