Ship propulsion shafting and method of modeling thereof

Abstract

The application discloses a modeling method of a ship propulsion shafting, comprising the following steps: taking design drawings and parameters of each component of the ship propulsion shafting as input, establishing a calculation model of longitudinal vibration characteristics of the propulsion shafting according to dynamics theory; setting constraint boundary conditions, calculating inherent characteristics of longitudinal vibration; setting damping parameters and applying longitudinal excitation force, calculating longitudinal vibration response of the propulsion shafting; checking safety of the longitudinal vibration response of the propulsion shafting and alternating thrust of the thrust bearing according to existing design specifications, confirming whether the calculation model of longitudinal vibration characteristics of the propulsion shafting is reasonable; and outputting parameters of each part of the calculation model of longitudinal vibration characteristics of the propulsion shafting when the calculation model of longitudinal vibration characteristics of the propulsion shafting is reasonable. The modeling method establishes a more perfect calculation model, can conveniently consider longitudinal constraint characteristics of radial support bearings and bending vibration characteristics of propeller blades, and improves calculation precision of longitudinal vibration characteristics of the ship propulsion shafting.

Description

Technical Field

[0001] The present invention relates to the technical field of ship propulsion systems, and in particular to a ship propulsion shaft system and a modeling method thereof. Background Art

[0002] The propulsion shafting system is a critical system of a ship, and its vibration characteristics impact the ship's safety and stealth. During navigation, the propeller's rotation in the non-uniform wake flow field generates periodic longitudinal excitation forces, which can induce longitudinal vibrations in the propeller shaft system. This vibration energy is transmitted through the thrust bearing to the foundation and hull structure, causing low-frequency hull structural vibrations and radiated noise. Therefore, verification and calculation of the longitudinal vibration characteristics of the ship's propulsion shafting system are essential during the design phase to ensure safe and reliable operation of the propulsion shafting system.

[0003] Currently, numerical calculation methods for the longitudinal vibration of ship propulsion shafting include the transfer matrix method, finite element method, mechanical admittance method, or impedance method. The key to numerical calculation is to establish an appropriate model. When modeling the propulsion shafting system, the propeller is usually simplified as a rigid disk or mass block, the shaft segment is simplified as a beam model, and the thrust bearing is simplified as a spring model. The longitudinal constraint at the thrust bearing is primarily considered. However, the centerline of a ship propulsion shafting system in its actual installation state is not a theoretical straight line due to its own gravity, and the radial support bearings are not completely free of longitudinal constraints due to the presence of friction pairs. Furthermore, for both propulsion shafting systems tested on land benches and those of actual ships, the inherent and transfer characteristics of the shafting longitudinal vibration obtained using these modeling and calculation methods often differ significantly from the test results, especially for long shafting systems with multiple radial support bearings. Therefore, it is necessary to conduct in-depth research on the modeling and calculation methods for the longitudinal vibration characteristics of ship propulsion shafting systems and establish more appropriate modeling methods to guide the engineering design of ship propulsion shafting systems. Summary of the Invention

[0004] The main purpose of the present invention is to provide a ship propulsion shafting and a modeling method thereof, aiming to improve the calculation accuracy of the longitudinal vibration characteristics of the ship propulsion shafting.

[0005] To achieve the above object, the present invention provides a modeling method for a ship propulsion shafting system, comprising the following steps:

[0006] Taking the design drawings of the ship propulsion shaft system and the parameters of each component as input, a calculation model for the longitudinal vibration characteristics of the propulsion shaft system is established according to dynamics theory;

[0007] The damping parameters are set on the established calculation model of the longitudinal vibration characteristics of the propulsion shafting and the longitudinal excitation force is applied to calculate the longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing.

[0008] The longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing are safety checked against existing design specifications to confirm whether the established calculation model for the longitudinal vibration characteristics of the propulsion shafting is reasonable;

[0009] When the propulsion shaft system longitudinal vibration characteristic calculation model is reasonable, the parameters of each component of the propulsion shaft system longitudinal vibration characteristic calculation model are output.

[0010] Preferably, after the step of performing safety verification on the propulsion shafting longitudinal vibration response and the alternating thrust of the thrust bearing with existing design specifications and determining whether the established propulsion shafting longitudinal vibration characteristic calculation model is reasonable, the method further includes:

[0011] When the calculation model of the longitudinal vibration characteristics of the propulsion shafting is unreasonable, the step of establishing the calculation model of the longitudinal vibration characteristics of the propulsion shafting according to the dynamics theory is returned to the step of taking the design drawings of the ship propulsion shafting and the parameters of each component as input.

[0012] Preferably, before the steps of setting damping parameters on the established propulsion shafting longitudinal vibration characteristic calculation model and applying longitudinal excitation force to calculate the propulsion shafting longitudinal vibration response and the alternating thrust of the thrust bearing, the method further comprises:

[0013] After setting constraint boundary conditions on the established calculation model of the longitudinal vibration characteristics of the propulsion shafting, the inherent characteristics of the longitudinal vibration are calculated.

[0014] Preferably, when establishing a calculation model for the longitudinal vibration characteristics of the propulsion shaft system, the propeller is simplified to an equivalent beam-mass combination model, the blade is simplified to a beam model according to the dynamic equivalence theory, and the hub is simplified to a mass block; the shaft section is simplified to a beam model; the thrust bearing is simplified to a spring-mass model; and the coupling and flange are simplified to a concentrated mass model.

[0015] Preferably, when establishing the calculation model of the longitudinal vibration characteristics of the propulsion shaft system, the finite element method is used to establish the unit mass matrix and stiffness matrix of each component, and then the calculation model of the longitudinal vibration characteristics of the propulsion shaft system is formed by assembling according to the boundary conditions.

[0016] Preferably, when setting constraint boundary conditions on the established propulsion shafting longitudinal vibration characteristic calculation model, constraint boundary conditions are applied at the thrust bearing and the radial support bearing.

[0017] Preferably, after setting constraint boundary conditions on the established propulsion shafting longitudinal vibration characteristic calculation model, the step of calculating the longitudinal vibration inherent characteristics specifically includes:

[0018] By applying constraint boundaries to the ground ends of the radial support bearing spring unit and the thrust bearing spring unit, the longitudinal free vibration equation of the propulsion shafting is obtained.

[0019] The numerical calculation method is used to solve the longitudinal free vibration equation of the shaft system, and the natural frequency and mode of the longitudinal vibration of the propulsion shaft system are obtained.

[0020] Preferably, the longitudinal vibration inherent characteristics include the natural frequency and mode of the longitudinal vibration of the propulsion shaft system; and the longitudinal vibration response of the propulsion shaft system includes the longitudinal amplitude of the thrust bearing at multiple rotating speeds.

[0021] Preferably, the longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing are checked for safety according to the existing design specification in the following manner:

[0022] According to the natural frequency of the longitudinal vibration of the propulsion shaft system, the standard amplitude range corresponding to the frequency under the existing design specification is determined;

[0023] The longitudinal amplitudes of the thrust bearing at multiple rotating speeds are compared with the standard amplitude range, and the alternating thrust of the thrust bearing at multiple rotating speeds is compared with the smaller value of half of the rated power thrust and the average thrust;

[0024] When the longitudinal amplitude and the alternating thrust of the thrust bearing both meet the requirements, it indicates that the longitudinal vibration characteristic calculation model of the propulsion shaft system is reasonably designed.

[0025] The present application provides a ship propulsion shaft system manufactured by using the parameters obtained based on the above modeling method.

[0026] The modeling method of the ship propulsion shaft system has the following beneficial effects:

[0027] 1. A more perfect longitudinal vibration characteristic calculation model of the propulsion shaft system is established, which can conveniently consider the longitudinal constraint characteristics of the radial support bearing and the bending vibration characteristics of the propeller blade, and improves the calculation accuracy of the longitudinal vibration characteristics of the ship propulsion shaft system.

[0028] 2. The modeling method is simple and easy to operate, and can be used for engineering design of the ship propulsion shaft system, thereby improving the safe and reliable operation degree of the ship propulsion shaft system. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 FIG. 1 is a flowchart of the modeling method of the ship propulsion shaft system of the present application;

[0030] Figure 2 FIG. 2 is a structural diagram of the longitudinal vibration characteristic finite element model in embodiment 1 of the modeling method of the ship propulsion shaft system of the present application;

[0031] Figure 3 FIG. 3 is a diagram of the natural frequency and mode of the longitudinal vibration calculated in embodiment 1 of the modeling method of the ship propulsion shaft system of the present application;

[0032] Figure 4aThis is a graph showing the change in longitudinal amplitude at the thrust bearing versus speed calculated in Example 1 of the modeling method for a ship propulsion shafting system of the present invention;

[0033] Figure 4b This is a graph showing the change in alternating thrust at the thrust bearing versus speed calculated in Example 1 of the modeling method for a ship propulsion shafting system of the present invention;

[0034] Figure 5 This is a diagram of the longitudinal vibration transmission characteristics of the propulsion shafting system of Example 1 of the modeling method for the ship propulsion shafting system of the present invention.

[0035] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0036] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] It should be noted that in the description of the present invention, the terms "transverse," "longitudinal," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] The present invention provides a modeling method for a ship propulsion shafting system.

[0039] In this preferred embodiment, a modeling method for a ship propulsion shaft system includes the following steps:

[0040] Step S10, using the design drawings of the ship propulsion shaft system and the parameters of each component as input, and according to dynamics theory, establishing a propulsion shaft system longitudinal vibration characteristic calculation model;

[0041] Step S20, setting damping parameters and applying longitudinal excitation force on the established propulsion shafting longitudinal vibration characteristic calculation model, and calculating the propulsion shafting longitudinal vibration response and the alternating thrust of the thrust bearing;

[0042] In step S30, the longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing are safety checked against the existing design specifications (GJB4000-2000) to determine whether the established calculation model for the longitudinal vibration characteristics of the propulsion shaft system is reasonable; when the calculation model for the longitudinal vibration characteristics of the propulsion shaft system is determined to be reasonable, step S40 is executed; when the calculation model for the longitudinal vibration characteristics of the propulsion shaft system is determined to be unreasonable, the process returns to step S10 until it is determined to be reasonable.

[0043] Step S40: outputting the parameters of each component of the propulsion shaft system longitudinal vibration characteristic calculation model.

[0044] Furthermore, between step S10 and step S20, the following steps are further included:

[0045] Step S11 , after setting constraint boundary conditions on the established propulsion shafting longitudinal vibration characteristic calculation model, calculate the longitudinal vibration inherent characteristics.

[0046] Specifically, in step S10, when establishing the calculation model of the longitudinal vibration characteristics of the propulsion shaft system, the propeller is simplified to an equivalent beam-mass combination model, the blade is simplified to a beam model according to the dynamic equivalent theory, the hub is simplified to a mass block; the shaft section is simplified to a beam model; the thrust bearing is simplified to a spring-mass model; the coupling and flange are simplified to a concentrated mass model. Specifically, the thrust bearing is simplified to a spring k 1-Quality m -spring k 2 models, k 1 is the stiffness between the thrust plate and the thrust washer, k 2 is the stiffness of the bearing base, m is the mass of the thrust bearing housing. When the shaft segment is simplified to a beam model, a certain longitudinal bearing stiffness is considered for the shaft segment within the length range of the radial support bearing.

[0047] When establishing the propulsion shafting longitudinal vibration characteristic calculation model, the finite element method is used to establish the unit mass matrix and stiffness matrix of each component. This is then assembled according to boundary conditions to form the propulsion shafting longitudinal vibration characteristic calculation model. When setting constraint boundary conditions on the established propulsion shafting longitudinal vibration characteristic calculation model, constraint boundary conditions are applied to the thrust bearing and radial support bearing.

[0048] Step S20 specifically includes:

[0049] Step S201 , applying constraint boundaries to the ground ends of the radial support bearing spring unit and the thrust bearing spring unit to obtain a longitudinal free vibration equation of the propulsion shaft system;

[0050] Step S202 : solving the longitudinal free vibration equation of the shafting system using a numerical calculation method to obtain the natural frequency and mode shape of the longitudinal vibration of the propulsion shafting system.

[0051] Specifically, the longitudinal vibration natural characteristics include the propulsion shafting longitudinal vibration natural frequency and mode shape, and the propulsion shafting longitudinal vibration response includes the longitudinal amplitude of the thrust bearing at multiple rotational speeds.

[0052] The inherent characteristics of longitudinal vibration and alternating thrust of thrust bearings are checked for safety against existing design specifications using the following methods:

[0053] Determine the standard amplitude range under the existing design specifications based on the shaft speed of the propulsion system;

[0054] Compare the longitudinal amplitude of the thrust bearing at multiple speeds with the standard amplitude range, and compare the alternating thrust of the thrust bearing at multiple speeds with the smaller value of half the rated power thrust and the average thrust;

[0055] When the longitudinal amplitude and the alternating thrust of the thrust bearing meet the requirements, it means that the design of the calculation model of the longitudinal vibration characteristics of the propulsion shafting is reasonable.

[0056] Table 1 Correspondence between frequency and standard amplitude in existing design specifications

[0057]

[0058] Specifically, after determining the calculated speed range by the propulsion system shaft speed, encryption processing is performed near the calculated speed corresponding to the natural frequency according to the inherent characteristics of the longitudinal vibration to ensure the accuracy of the calibration model.

[0059] When calibrating the model, it is first necessary to determine the multiple speeds corresponding to the thrust bearing. This speed can be calculated using the existing formula to propose a calculation frequency, which is the calculation frequency in Table 1 above. Based on this calculation frequency, the corresponding standard amplitude can be obtained. Then, the longitudinal amplitudes at multiple speeds of the thrust bearing are compared with the standard amplitude range. Because each speed corresponds to a longitudinal amplitude, the longitudinal amplitudes corresponding to all speeds are compared with the standard amplitude range. Then, it is determined that all longitudinal amplitudes meet the requirements of the above table, which shows that the model design is reasonable.

[0060] When comparing the alternating thrust of the thrust bearing, the model design is considered reasonable only if the alternating thrust does not exceed 50% of the rated power thrust or the average thrust at the same speed, whichever is smaller. The rated power thrust is determined by matching the propeller to the rated operating condition and is a known condition in this calculation. Based on the rated power thrust, the average thrust at different speeds can be calculated using existing formulas.

[0061] The following is a detailed description using Example 1 as an example. The calculation object is a propulsion shaft system of a real ship, which uses a 5-bladed fixed-pitch propeller, has a basic shaft diameter of 300 mm, a shaft length of 26 m, a total of 5 supporting bearings, a rated speed of 180 r / min, and a rated power thrust of 120 kN.

[0062] Firstly, the calculation model of the longitudinal vibration characteristics of the shafting of a real ship is established. According to the design drawings and component parameters of the shafting of a real ship, the propeller is simplified as a beam-mass combination model, the blade is simplified as a beam model, the mass and the first order bending vibration natural frequency of the beam model are consistent with the actual blade, the propeller hub is simplified as a concentrated mass model, and the two are rigidly connected; the shaft section is simplified as a beam model, only the longitudinal vibration characteristics of the beam are considered; at the radial bearing, a certain longitudinal stiffness is considered due to the frictional constraint between the shaft neck and the bearing; the thrust bearing is simplified as a spring k 1-mass m -spring k 2 model, k 1 is the stiffness between the thrust disc and the thrust pad, k 2 is the stiffness of the bearing base, m and the mass of the thrust bearing shell; the components with concentrated mass characteristics such as the coupling, flange, etc. are simplified as mass models. In this example, the finite element method is used to establish the element mass matrix and stiffness matrix of each component, and then the boundary conditions are assembled to form the longitudinal vibration characteristic finite element model of the shafting, as shown in Figure 2 .

[0063] Secondly, the constraint boundary conditions are set, and the longitudinal vibration inherent characteristics are calculated. For the longitudinal vibration characteristic finite element model of the shafting established in the previous step, the ground end of the spring element of the radial bearing and the spring element k2 of the thrust bearing are subjected to constraint boundary conditions, i.e. the longitudinal vibration degree of freedom is constrained, and the longitudinal free vibration equation of the shafting is obtained: M +Kx=0, where M, K are the system mass matrix and stiffness matrix respectively, x is the node displacement vector of the system, and the node acceleration vector of the system. The free vibration equation is solved by using numerical calculation method, and the longitudinal vibration natural frequency and mode shape of the shafting can be obtained, as shown in Figure 3 . The first section longitudinal vibration natural frequency is about 8.93 Hz, and the test value of the real ship is about 9.17 Hz. The natural frequency of the blade bending as the main vibration form can also be calculated by using this model, which is about 39.9 Hz.

[0064] Thirdly, the damping parameters are set, the longitudinal excitation force is applied, and the longitudinal vibration response of the shafting is calculated. The damping parameters are set at the propeller and the bearing, the damping is applied to the shaft section in the form of damping loss factor η, and η can be taken as 0.005; the longitudinal excitation force is applied at 0.7R of the propeller blade, R is the radius of the propeller. When considering the blade frequency excitation force, the alternating thrust at the thrust bearing and the vibration displacement amplitude calculated are shown in Figure 4a and Figure 4bWhen a unit excitation force is applied to the blade, the calculated transfer characteristics of the excitation force and the vibration response at the thrust bearing are shown in Figure 5 , where the 1st, 3rd and 4th peaks are the natural frequencies of the longitudinal vibration of the shaft system, and the 2nd peak is the first-order bending natural frequency of the blade.

[0065] The fourth step is to evaluate and analyze the longitudinal vibration characteristics of the propulsion shaft system. According to the relevant standards for the longitudinal vibration of the ship propulsion shaft system, Figure 4a and Figure 4b The calculation results are compared with Table 1 above, which shows that they meet the requirements of existing design specifications. At the same time, the corresponding alternating thrust at each speed does not exceed 50% of the rated power thrust and the average thrust at the same speed, and the vibration displacement is less than 0.51mm, indicating that the propulsion shaft system design is reasonable.

[0066] The modeling method of the ship propulsion shafting system proposed in this embodiment has the following beneficial effects:

[0067] 1. A more complete calculation model for the longitudinal vibration characteristics of the propulsion shafting has been established, which can conveniently consider the longitudinal constraint characteristics of the radial support bearings and the bending vibration characteristics of the propeller blades, thereby improving the calculation accuracy of the longitudinal vibration characteristics of the ship's propulsion shafting;

[0068] 2. This modeling method is simple and easy to operate, and can be used for the engineering design of ship propulsion shafting, thereby improving the safety and reliability of the ship propulsion shafting.

[0069] The present invention provides a ship propulsion shaft system.

[0070] In this embodiment, a ship propulsion shaft system is manufactured based on the parameters of each component obtained by the above-mentioned modeling method.

[0071] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied to other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A modeling method for a ship propulsion shaft system, characterized in that: The following steps are involved: Taking the design drawings of the ship propulsion shaft system and the parameters of each component as input, a calculation model for the longitudinal vibration characteristics of the propulsion shaft system is established according to dynamics theory; The damping parameters are set on the established calculation model of the longitudinal vibration characteristics of the propulsion shafting and the longitudinal excitation force is applied to calculate the longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing. The longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing are safety checked against existing design specifications to confirm whether the established calculation model for the longitudinal vibration characteristics of the propulsion shafting is reasonable; When the propulsion shaft system longitudinal vibration characteristic calculation model is reasonable, the parameters of each component of the propulsion shaft system longitudinal vibration characteristic calculation model are output; When establishing the calculation model of the longitudinal vibration characteristics of the propulsion shaft system, the propeller is simplified to an equivalent beam-mass combination model, the blade is simplified to a beam model according to the dynamic equivalence theory, the hub is simplified to a mass block; the shaft section is simplified to a beam model; the thrust bearing is simplified to a spring-mass model; the coupling and flange are simplified to a concentrated mass model.

2. The modeling method of a ship propulsion shafting system according to claim 1, characterized in that: After the step of performing safety verification on the propulsion shafting longitudinal vibration response and the alternating thrust of the thrust bearing against existing design specifications to determine whether the established propulsion shafting longitudinal vibration characteristic calculation model is reasonable, the following steps are further included: When the calculation model of the longitudinal vibration characteristics of the propulsion shafting is unreasonable, the step of establishing the calculation model of the longitudinal vibration characteristics of the propulsion shafting according to the dynamics theory is returned to the step of taking the design drawings of the ship propulsion shafting and the parameters of each component as input.

3. The modeling method of a ship propulsion shafting system according to claim 1, wherein: Before the step of setting damping parameters on the established propulsion shafting longitudinal vibration characteristic calculation model and applying longitudinal excitation force to calculate the propulsion shafting longitudinal vibration response and the alternating thrust of the thrust bearing, the method further includes: After setting constraint boundary conditions on the established calculation model of the longitudinal vibration characteristics of the propulsion shafting, the inherent characteristics of the longitudinal vibration are calculated.

4. The modeling method of a ship propulsion shafting system according to claim 1, wherein: When establishing the calculation model of the longitudinal vibration characteristics of the propulsion shaft system, the finite element method is used to establish the unit mass matrix and stiffness matrix of each component, and then the calculation model of the longitudinal vibration characteristics of the propulsion shaft system is formed according to the boundary conditions.

5. The modeling method of a ship propulsion shafting system according to claim 1, wherein: When setting constraint boundary conditions on the established calculation model of the longitudinal vibration characteristics of the propulsion shafting, constraint boundary conditions are imposed on the thrust bearing and the radial support bearing.

6. The modeling method of a ship propulsion shafting system according to claim 1, wherein: After setting constraint boundary conditions on the established propulsion shafting longitudinal vibration characteristic calculation model, the step of calculating the longitudinal vibration inherent characteristics specifically includes: By applying constraint boundaries to the ground ends of the radial support bearing spring unit and the thrust bearing spring unit, the longitudinal free vibration equation of the propulsion shafting is obtained. The longitudinal free vibration equation of the shafting is solved using numerical calculation methods, and the natural frequency and mode shape of the longitudinal vibration of the propulsion shafting are obtained.

7. The modeling method of a ship propulsion shafting system according to claim 3, characterized in that: The longitudinal vibration inherent characteristics include the propulsion shaft system longitudinal vibration inherent frequency and vibration mode; the propulsion shaft system longitudinal vibration response includes the longitudinal amplitude of the thrust bearing at multiple speeds.

8. The modeling method of a ship propulsion shafting system according to claim 7, characterized in that: The longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing are checked for safety against existing design specifications. Use the following method: Determine the standard amplitude range under the existing design specifications based on the shaft speed of the propulsion system; Compare the longitudinal amplitude of the thrust bearing at multiple speeds with the standard amplitude range, and compare the alternating thrust of the thrust bearing at multiple speeds with the smaller value of half the rated power thrust and the average thrust; When the longitudinal amplitude and the alternating thrust of the thrust bearing meet the requirements, it means that the design of the calculation model of the longitudinal vibration characteristics of the propulsion shafting is reasonable.

9. A ship propulsion shaft system, characterized in that: The invention is manufactured using parameters obtained based on the modeling method according to any one of claims 1 to 8.

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