Ship propulsion shafting and modeling method thereof

Abstract

The invention discloses a modeling method of a ship propulsion shafting, which comprises the following steps of: establishing a longitudinal vibration characteristic calculation model of the propulsion shafting according to a dynamic theory by taking a design drawing of the ship propulsion shafting and parameters of each component as input; after constraint boundary conditions are set, longitudinal vibration natural characteristics are calculated; damping parameters are set, longitudinal exciting force is applied, and longitudinal vibration response of the propulsion shafting is calculated; safety checking is carried out on the longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing according to existing design specifications, and whether the established longitudinal vibration characteristic calculation model of the propulsion shafting is reasonable or not is determined; and when the longitudinal vibration characteristic calculation model of the propulsion shafting is reasonable, outputting parameters of each part of the longitudinal vibration characteristic calculation model of the propulsion shafting. According to the modeling method, a more perfect calculation model is established, the longitudinal constraint characteristic of the radial supporting bearing and the bending vibration characteristic of the propeller blade can be conveniently considered, and the calculation precision of the longitudinal vibration characteristic of the ship propulsion shafting is improved.

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 shaft system is a key system of the ship, and its vibration characteristics affect the safety and concealment of the ship. During the navigation of a surface ship, the propeller will generate periodic longitudinal exciting force when rotating in the non-uniform wake field at the rear, which can cause the longitudinal vibration of the propeller shaft system. This vibration energy is transmitted to the base and hull structure through the thrust bearing, thereby causing low-frequency hull structure vibration and radiated noise. Therefore, the longitudinal vibration characteristics of the ship's propulsion shaft system must be checked and calculated during the design stage to ensure the safe and reliable operation of the propulsion shaft system.

[0003] At present, the numerical calculation methods for the longitudinal vibration of ship propulsion shafting include transfer matrix method, finite element method, mechanical admittance method or impedance method, etc. The key to numerical calculation is to establish a suitable model. When modeling the propulsion shafting, the propeller is usually simplified to a rigid disk or mass block, the shaft section is simplified to a beam model, and the thrust bearing is simplified to a spring model, and the longitudinal constraint conditions at the thrust bearing are mainly considered. However, the center line of the ship propulsion shafting under the actual installation state is not a theoretical straight line under the action of its own gravity, and the radial support bearing is not completely free of longitudinal constraints due to the existence of friction pairs. In addition, whether it is for the propulsion shafting of the onshore bench test or the propulsion shafting of the actual ship, the inherent characteristics and transfer characteristics of the longitudinal vibration of the shafting obtained according to the above modeling and calculation methods are often quite different from the test results, especially for the long shafting with multiple radial support bearings. Therefore, it is necessary to conduct in-depth research on the modeling and calculation methods of the longitudinal vibration characteristics of the ship propulsion shafting and establish a more appropriate modeling method to guide the engineering design of the ship propulsion shafting. Summary of the invention

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

[0005] To achieve the above object, the present invention provides a modeling method for a ship propulsion shaft system, comprising the following steps: 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 the dynamics theory; The damping parameters are set on the established calculation model of the longitudinal vibration characteristics of the propulsion shaft system and the longitudinal excitation force is applied to calculate the longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing; The longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing are checked for safety against the existing design specifications to confirm whether the established calculation model for the longitudinal vibration characteristics of the propulsion shaft system 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.

[0006] Preferably, after the step of performing safety verification on the longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing with existing design specifications and judging whether the established calculation model for the longitudinal vibration characteristics of the propulsion shaft system is reasonable, the step further includes: When the calculation model of the longitudinal vibration characteristics of the propulsion shafting is unreasonable, return to the step of establishing the calculation model of the longitudinal vibration characteristics of the propulsion shafting according to the dynamics theory with the design drawings of the ship propulsion shafting and the parameters of each component as input.

[0007] Preferably, 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 step further includes: After setting constraint boundary conditions on the established calculation model of longitudinal vibration characteristics of propulsion shafting, the inherent characteristics of longitudinal vibration are calculated.

[0008] Preferably, when establishing a calculation model for the longitudinal vibration characteristics of a 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; and the coupling and flange are simplified to concentrated mass models.

[0009] 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 assembled according to the boundary conditions.

[0010] Preferably, when setting constraint boundary conditions on the established propulsion shafting longitudinal vibration characteristic calculation model, the constraint boundary conditions are applied at the thrust bearing and the radial support bearing.

[0011] 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: Constrained boundaries are imposed on the grounded ends of the radial bearing spring unit and the thrust bearing spring unit to obtain the longitudinal free vibration equation of the propulsion shaft system. The longitudinal free vibration equation of the shafting is solved by numerical calculation method, and the natural frequency and vibration mode of the longitudinal vibration of the propulsion shafting are obtained.

[0012] Preferably, the inherent characteristics of the longitudinal vibration include the inherent frequency and vibration 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 rotational speeds.

[0013] Preferably, the longitudinal vibration response of the propulsion shafting and the alternating thrust of the thrust bearing are safety checked against existing design specifications in the following manner: Determine the standard amplitude range corresponding to the frequency under the existing design specifications according to the natural frequency of the longitudinal vibration of the propulsion shaft 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 calculation model of the longitudinal vibration characteristics of the propulsion shafting is reasonably designed.

[0014] The present invention provides a ship propulsion shaft system, which is manufactured using parameters obtained based on the above modeling method.

[0015] The modeling method of the ship propulsion shaft system proposed in the present invention has the following beneficial effects: 1. A more complete calculation model for the longitudinal vibration characteristics of the propulsion shaft system has been established, which can conveniently consider the longitudinal constraint characteristics of the radial support bearing and the bending vibration characteristics of the propeller blades, thereby improving the calculation accuracy of the longitudinal vibration characteristics of the ship propulsion shaft system; 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 reliable operation of the ship propulsion shafting. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of the modeling method of the ship propulsion shaft system of the present invention; Figure 2 It is a structural schematic diagram of the finite element model of the longitudinal vibration characteristics in Example 1 of the modeling method of the ship propulsion shaft system of the present invention; Figure 3 The longitudinal vibration natural frequency and mode shape diagram calculated by the modeling method embodiment 1 of the ship propulsion shaft system of the present invention; Figure 4a This is a graph showing the change of the longitudinal amplitude at the thrust bearing with the rotational speed obtained by calculation in Example 1 of the modeling method for the ship propulsion shaft system of the present invention; Figure 4b The diagram of the alternating thrust at the thrust bearing versus the rotational speed calculated by the modeling method for the ship propulsion shaft system of the present invention in Example 1; 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.

[0017] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0018] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0019] 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", "inside", "outside" and the like indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] The invention provides a modeling method for a ship propulsion shaft system.

[0021] In this preferred embodiment, a modeling method for a ship propulsion shaft system includes the following steps: Step S10, taking the design drawings of the ship propulsion shaft system and the parameters of each component as input, and according to the dynamics theory, establishing a propulsion shaft system longitudinal vibration characteristic calculation model; Step S20, setting damping parameters on the established propulsion shafting longitudinal vibration characteristic calculation model and applying longitudinal excitation force, and calculating the propulsion shafting longitudinal vibration response and the alternating thrust of the thrust bearing; Step S30, conduct safety check on the longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing with the existing design specifications (GJB4000-2000) to determine whether the established calculation model of the longitudinal vibration characteristics of the propulsion shaft system is reasonable; when the calculation model of the longitudinal vibration characteristics of the propulsion shaft system is determined to be reasonable, execute step S40; when the calculation model of the longitudinal vibration characteristics of the propulsion shaft system is determined to be unreasonable, return to execute step S10 until it is determined to be reasonable.

[0022] Step S40, outputting the parameters of each component of the propulsion shaft system longitudinal vibration characteristic calculation model.

[0023] Furthermore, between step S10 and step S20, the following steps are also included: Step S11, after setting constraint boundary conditions on the established propulsion shaft system longitudinal vibration characteristic calculation model, calculate the longitudinal vibration inherent characteristics.

[0024] 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.

[0025] 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 assembled according to the boundary conditions. When setting the constraint boundary conditions on the established calculation model of the longitudinal vibration characteristics of the propulsion shaft system, the constraint boundary conditions are applied at the thrust bearing and the radial support bearing.

[0026] Step S20 specifically includes: 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; Step S202, using a numerical calculation method to solve the longitudinal free vibration equation of the shaft system to obtain the longitudinal vibration natural frequency and vibration mode of the propulsion shaft system.

[0027] Specifically, the longitudinal vibration natural characteristics include the propulsion shaft system longitudinal vibration natural frequency and vibration mode. The propulsion shaft system longitudinal vibration response includes the longitudinal amplitude of the thrust bearing at multiple rotation speeds.

[0028] The inherent characteristics of longitudinal vibration and alternating thrust of thrust bearings are checked for safety against existing design specifications in the following ways: 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 calculation model of the longitudinal vibration characteristics of the propulsion shafting is reasonably designed.

[0029] Table 1 Correspondence between frequency and standard amplitude in existing design specifications

[0030] Specifically, after determining the calculated speed range through the shaft speed of the propulsion system, 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 verification model.

[0031] When calibrating the model, it is necessary to first 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.

[0032] When comparing the alternating thrust of the thrust bearing, the alternating thrust of the thrust bearing does not exceed 50% of the rated power thrust or the smaller value of the average thrust at the same speed, which indicates that the model design is reasonable. The rated power thrust is obtained by matching the propeller of the ship engine to obtain the thrust under the rated working condition, which is a known condition in this calculation. According to the rated power thrust, the average thrust at different speeds can be calculated using the existing formula.

[0033] The following is a specific description using Example 1 as an example. The calculation object is a propulsion shaft system of a real ship, which uses a 5-blade fixed pitch propeller, 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.

[0034] The first step is to establish a calculation model for the longitudinal vibration characteristics of a real ship propulsion shaft system. According to the design drawings and component parameters of a real ship propulsion shaft system, the propeller is simplified to a beam-mass combination model, the blade is simplified to a beam model, the beam model mass and the first-order bending vibration natural frequency are consistent with the actual blade, the hub is simplified to a concentrated mass model, and the two are rigidly connected; the shaft section is simplified to a beam model, and only the longitudinal vibration characteristics of the beam are considered; at the radial support bearing, due to the friction constraint between the journal and the bearing, a certain longitudinal stiffness is considered; 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; the coupling, flange and other components with concentrated mass characteristics are simplified as mass models. In this example, the finite element method is used to establish the unit mass matrix and stiffness matrix of each component, and then the finite element model of the longitudinal vibration characteristics of the propulsion shaft system is assembled according to the boundary conditions. Figure 2shown.

[0035] The second step is to set constraint boundary conditions and calculate the inherent characteristics of longitudinal vibration. For the finite element model of longitudinal vibration characteristics of the propulsion shaft system established in the previous step, constraint boundaries are applied to the ground ends of the radial support bearing spring unit and the thrust bearing spring unit k2, that is, to constrain their longitudinal vibration degrees of freedom, and the longitudinal free vibration equation of the propulsion shaft system is obtained: M +Kx=0, where M and K are the system mass matrix and stiffness matrix respectively, and x is the node displacement vector of the system. is the node acceleration vector of the system. By solving the free vibration equation using numerical calculation methods, the natural frequency and vibration mode of the longitudinal vibration of the propulsion shaft system can be obtained. Figure 3 Among them, the calculated value of the natural frequency of the longitudinal vibration of the first section is about 8.93Hz, and the actual ship test value is about 9.17Hz. This model can also be used to calculate the natural frequency of the main vibration form of blade bending, which is about 39.9Hz.

[0036] The third step is to set the damping parameters, apply the longitudinal excitation force, and calculate the longitudinal vibration response of the propulsion shaft system. Set the damping parameters at the propeller and support bearings, and apply damping to the shaft section using the damping loss factor η, where η can be 0.005; apply the longitudinal excitation force at 0.7R of the propeller blade, where R is the propeller radius. When considering the blade frequency excitation force, the calculated alternating thrust and vibration displacement amplitude at the thrust bearing are shown in Figure 4a and Figure 4b When 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.

[0037] 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 those in Table 1 above, which shows that they meet the requirements of the 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 design of the propulsion shaft system is reasonable.

[0038] The modeling method of the ship propulsion shaft system proposed in this embodiment has the following beneficial effects: 1. A more complete calculation model for the longitudinal vibration characteristics of the propulsion shaft system has been established, which can conveniently consider the longitudinal constraint characteristics of the radial support bearing and the bending vibration characteristics of the propeller blades, thereby improving the calculation accuracy of the longitudinal vibration characteristics of the ship propulsion shaft system; 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 reliable operation of the ship propulsion shafting.

[0039] The invention provides a ship propulsion shaft system.

[0040] In this embodiment, a ship propulsion shaft system is manufactured based on the parameters of each component obtained by the above-mentioned modeling method.

[0041] 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 specification and drawings, or directly or indirectly applied in 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 the dynamics theory; The damping parameters are set on the established calculation model of the longitudinal vibration characteristics of the propulsion shaft system and the longitudinal excitation force is applied to calculate the longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing; The longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing are checked for safety against the existing design specifications to confirm whether the established calculation model for the longitudinal vibration characteristics of the propulsion shaft system 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.

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

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

4. The modeling method of a ship propulsion shaft system according to claim 1, characterized in that: 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.

5. The modeling method of a ship propulsion shaft system according to claim 1, characterized in that: 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 assembled according to the boundary conditions.

6. The modeling method of a ship propulsion shaft system according to claim 1, characterized in that: 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.

7. The modeling method of a ship propulsion shaft system according to claim 1, characterized in that: After setting constraint boundary conditions on the established propulsion shaft system longitudinal vibration characteristic calculation model, the step of calculating the longitudinal vibration inherent characteristics specifically includes: Constrained boundaries are imposed on the grounded ends of the radial bearing spring unit and the thrust bearing spring unit to obtain the longitudinal free vibration equation of the propulsion shaft system. The longitudinal free vibration equation of the shafting is solved by numerical calculation method, and the natural frequency and vibration mode of the longitudinal vibration of the propulsion shafting are obtained.

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

9. The modeling method of a ship propulsion shaft system according to claim 8, characterized in that: The longitudinal vibration response of the propulsion shaft system and the alternating thrust of the thrust bearing are checked for safety against the 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 calculation model of the longitudinal vibration characteristics of the propulsion shafting is reasonably designed.

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

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