Marine propulsion gearbox vibration isolation system structural design method
By designing a vibration isolator that includes a conical rubber ring and a limiting bolt, and combining it with a finite element model, the problems of design complexity and high cost of vibration isolation systems for marine propulsion gearboxes were solved. This achieved efficient low-frequency noise isolation and anti-overturning torque capability, and simplified the design process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NO 703 RES INST OF CHINA SHIPBUILDING IND CORP
- Filing Date
- 2024-11-27
- Publication Date
- 2026-07-07
AI Technical Summary
The lack of a clear vibration isolation system and structural design method for marine propulsion gearbox devices in the existing technology leads to complex design, high cost, and difficulty in meeting the requirements for low-frequency noise isolation and anti-overturning torque.
Design a vibration isolator that includes a conical rubber ring and a limiting bolt. Combining finite element model and calculation method, determine the layout, quantity, size and stiffness of the vibration isolation system. Adopt a vibration isolator structure with three-dimensional limiting capability, and realize the limiting function through the limiting bolt and the conical limiting steel component.
It simplifies the design complexity, reduces the design cost, improves the vibration isolation effect, reduces the lateral space dimension of the propulsion gearbox, enhances the power density, and meets the requirements of low-frequency noise isolation and anti-overturning torque for marine propulsion gearboxes.
Smart Images
Figure CN119646981B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ship structure design technology, specifically relating to a design method for a vibration isolation system and structure for a marine propulsion gearbox. Background Technology
[0002] Structural noise from marine propulsion systems not only affects sailing comfort but, more importantly, impacts the combat performance of military vessels. Gearboxes primarily operate at low frequencies, making them more susceptible to radiating low-frequency noise through the hull compared to higher frequencies. This allows enemy sonar to detect the vessel, exposing its target and compromising its stealth capabilities. Furthermore, with advancements in technology, marine propulsion gearbox designs are becoming increasingly lightweight, while power output has significantly increased. This leads to a continuous rise in gearbox overturning torque. Simultaneously, considering the ship's rolling and pitching operating conditions, the design of vibration isolation systems is becoming increasingly challenging, resulting in more complex structures.
[0003] Due to the complexity of the boundary conditions to be considered, vibration isolation system designs often include multiple types of limiting devices, including lateral, axial, and vertical ones, making the design of the unit's vibration isolation system cumbersome and increasing design and manufacturing costs. Furthermore, there are currently no clearly defined vibration isolation system and structural design methods for marine propulsion gearboxes for designers to refer to. Summary of the Invention
[0004] This invention aims to address the current lack of a clearly defined vibration isolation system and structural design method for marine propulsion gearbox devices.
[0005] A vibration isolation system for a marine propulsion gearbox, the vibration isolation system comprising a plurality of identical vibration isolators, each vibration isolator comprising: an upper steel member, a lower steel member, a limiting bolt, a tapered steel member, and a tapered rubber ring;
[0006] A conical rubber ring is placed between the lower and upper steel parts for vibration isolation;
[0007] The lower steel component is rigidly connected to the conical limiting steel component, which is made of steel; the limiting bolt is rigidly fixedly connected to the upper steel component and cooperates with the conical limiting steel component for limiting.
[0008] A gap is left between the bottom surface of the limit bolt and the upper surface of the lower steel part, which is a vertical limit gap; a gap is left between the side surface of the limit bolt and the inner wall of the tapered limit steel part, which is a lateral limit gap.
[0009] Furthermore, the limiting bolt is a bolt-shaped limiting structure.
[0010] Furthermore, the radial interface of the main body of the limiting bolt is elliptical.
[0011] Furthermore, the conical limiting steel component is a hollow structure, and the limiting bolt and the conical limiting steel component are engaged in such a way that the limiting bolt is inserted into the hollow structure from one side of the upper steel component to achieve the engagement and limiting.
[0012] A design method for a vibration isolation system structure for a marine propulsion gearbox includes:
[0013] First, determine the excitation frequency of the marine propulsion main engine and gearbox under various operating conditions. Based on the excitation frequency, determine the vertical natural frequency f of the vibration isolation system. At the same time, calculate the support stiffness K of the vibration isolation system based on the overall mass m above the vibration isolation system. The selection of the vertical natural frequency is then limited based on the support stiffness K.
[0014] The design includes an overall support raft for the propulsion main unit and gearbox. The vibration isolation system includes multiple vibration isolators. The vibration isolators are arranged according to the installation bottom surface and space of the raft, and the number of vibration isolators is determined.
[0015] Based on the number of vibration isolators in the vibration isolation system and the support stiffness of the vibration isolation system, the stiffness value and load of a single vibration isolator are calculated; based on the stiffness of a single vibration isolator, the minimum allowable size of the vibration isolator is determined, and combined with the design conditions of the unit mounting surface, the external dimensions and interface dimensions of the vibration isolator are determined.
[0016] At this point, the location, quantity, size, stiffness, and load of the vibration isolation system have been determined, and a finite element model including the propulsion main unit, gearbox, floating raft base, and vibration isolation system has been established.
[0017] Based on marine operating conditions, the overturning moment of the gearbox is calculated using the power, speed, and self-weight of the unit under rated operating conditions. Simultaneously, the displacement of each interface of the unit is calculated. The displacement compensation amount at each interface position is determined according to the design. The calculated interface displacement values are compared with those under marine operating conditions and gearbox overturning moment operating conditions. If the actual interface displacement compensation amount is greater than the calculated value, it indicates that the current operating conditions are not sufficient to meet the normal operating conditions of the unit, and there is a possibility that excessive interface displacement may lead to unit failure. Therefore, the vibration isolator structure design of the aforementioned marine propulsion gearbox vibration isolation system is adopted.
[0018] Based on a rigid linear system, the unit displacement at the vibration isolator position is calculated by back-calculating the actual interface compensation amount, thereby determining the required limit value; the design parameters of the vibration isolator limit gap are determined based on the calculated limit value; the specific dimensions of the limit bolt that meets the bearing strength are obtained based on the vibration isolator structure and design parameters; and the specific dimensions of the tapered limit steel part are obtained based on the limit gap.
[0019] Furthermore, the vertical natural frequency f of the vibration isolation system is selected and determined based on the excitation frequency, outside the frequency avoidance rate range.
[0020] Furthermore, the frequency avoidance rate is selected as 20%.
[0021] Furthermore, the formula for calculating the support stiffness of the floating raft vibration isolation system is as follows: .
[0022] Furthermore, in the process of arranging vibration isolators according to the bottom surface and space of the floating raft and determining the number of vibration isolators, the arrangement of vibration isolators should try to ensure that the stiffness center and the center of gravity coincide; if there is no coincidence condition, the coincidence deviation shall not exceed 10%.
[0023] Furthermore, based on marine conditions, when calculating the overturning moment of the gearbox using the power, speed, and self-weight of the unit under rated operating conditions, the propulsion equipment corresponding to the main propulsion unit must meet the operating conditions of 45° roll and 10° pitch.
[0024] Beneficial effects:
[0025] Currently, marine propulsion main engines and gearboxes have high power and large overturning moments, and must simultaneously consider the rolling and pitching conditions during marine navigation. Displacements at various interfaces easily exceed compensation capabilities, requiring vibration isolation systems with three-dimensional limiting capabilities. This necessitates the design of multiple types of isolators and limiters. To address this issue, this invention provides a feasible design method for a vibration isolation system and structure for marine propulsion gearboxes. The structural design method of this invention presents a vibration isolator design structure with three-dimensional limiting capabilities, and all key design parameters of this isolator can be obtained through the design method provided in this invention. This structural design method achieves the limiting function currently required by combining multiple isolators and limiters using only a single isolator, thus significantly reducing design difficulty and cost, decreasing the lateral space dimension of the propulsion gearbox, and increasing power density. Attached Figure Description
[0026] Figure 1 Flowchart of the design method for vibration isolation system structure for marine propulsion gearbox;
[0027] Figure 2 This is a schematic diagram of a vibration isolator structure.
[0028] Figure 3 This is a schematic diagram of the bottom structure of the floating raft support.
[0029] Figure 4 This is a schematic diagram of the vibration isolator arrangement;
[0030] Figure 5 This is a 3D model diagram of the unit including vibration isolation system parameters;
[0031] Figure 6 Front view of the vibration isolator structure design;
[0032] Figure 7 Design a top view of the vibration isolator structure;
[0033] Figure 8 Isometric drawings for vibration isolator structural design. Detailed Implementation
[0034] To address the problems existing in the background technology, this invention proposes a vibration isolation structure design that simultaneously satisfies the requirements for lateral, vertical, and axial three-dimensional restraint. This structure can significantly simplify the design complexity and reduce the overall design and manufacturing costs of the vibration isolation system. Furthermore, the vibration isolation design method for this marine propulsion gearbox device proposed in this invention provides methods for calculating and selecting design parameters for the vibration isolation system, which can be used as guidance during the design phase and has certain application value. The following description, in conjunction with specific implementation methods, will illustrate this.
[0035] Specific implementation method one: Combining Figure 1 This implementation method is described below.
[0036] This embodiment describes a design method for a vibration isolation system structure for a marine propulsion gearbox, comprising the following steps:
[0037] First, it is necessary to determine the excitation frequencies of the marine propulsion main engine and gearbox under various operating conditions, such as the rotor frequency, harmonic frequency, and blade frequency of the main equipment such as motors, internal combustion engines, or steam turbines, and the rotational frequency and meshing frequency of all rotors in the gearbox.
[0038] Based on the frequency avoidance rate range mentioned above, a suitable vertical natural frequency f (Hz) of the vibration isolation system is selected. In this embodiment, the frequency avoidance rate is selected as 20%. Simultaneously, based on the overall mass m (kg) above the floating raft vibration isolation system, the support stiffness K (N / m) of the floating raft vibration isolation system can be calculated. The formula for calculating the system's support stiffness is as follows: The stiffness should not be too soft, as this will lead to excessive unit displacement; if the stiffness is too high, it will result in poor vibration isolation. Therefore, the vertical natural frequency should be reduced as much as possible while meeting the unit displacement requirements.
[0039] Design the overall support raft for the propulsion main unit and gearbox. Arrange vibration isolators and determine the number of vibration isolators according to the installation bottom surface and space of the raft. The arrangement of vibration isolators should, as far as possible, ensure that the stiffness center and the center of gravity coincide. If there are objective conditions that do not allow for coincidence, the coincidence deviation should not exceed 10%. The coincidence deviation refers to the ratio of the distance between the stiffness center and the center of gravity to the farthest distance between vibration isolators. The farthest distance between vibration isolators refers to the farthest distance between vibration isolators in a certain direction.
[0040] This determines the number of vibration isolators required for the vibration isolation system. Furthermore, based on the overall system stiffness, the stiffness and load of each individual vibration isolator can be calculated. The number of vibration isolators should not be excessive, as this affects the available space and installation; conversely, the number should not be too small, as this leads to excessive stiffness in each isolator and reduces the safety of the vibration isolation system.
[0041] Based on the stiffness of a single vibration isolator, the minimum allowable size of the vibration isolator can be determined. Combined with the design conditions of the unit's mounting surface, the appropriate external dimensions and interface dimensions of the vibration isolator can be determined.
[0042] At this point, the location, quantity, size, stiffness, and load of the vibration isolation system have been determined, and a finite element model including the propulsion main unit, gearbox, floating raft base, and vibration isolation system can be established.
[0043] According to marine operating conditions, the propulsion equipment must meet the operating conditions of 45° roll and 10° pitch. At the same time, the overturning moment of the gearbox can be calculated based on the power, speed and weight of the unit under rated operating conditions. Considering the above operating conditions, the displacement of each interface of the unit under these conditions, such as the coupling and oil and water pipeline equipment interfaces, can be calculated.
[0044] The displacement compensation amount at each interface position is determined according to the design, and the calculated interface displacement values are compared considering marine conditions and gearbox overturning moment operating conditions. If the actual interface displacement compensation amount is greater than the calculated value, it indicates that the current operating conditions without displacement cannot meet the normal operating conditions of the unit, and there is a possibility that excessive interface displacement may lead to unit failure. In this case, the vibration isolator limiting design structure proposed in this invention can be adopted, such as... Figure 2 As shown.
[0045] The vibration isolator has a steel structure at the top and bottom, namely upper steel component 1 and lower steel component 5, which are used to ensure structural strength; between the lower steel component and the upper steel component is a conical rubber ring 3 structure, which is used for vibration isolation.
[0046] The lower steel part 5 is rigidly connected to the conical limiting steel part 4. The conical limiting steel part 4 is a steel part with a hollow structure. The hollow structure has a limiting structure in the shape of a bolt (without threads) that passes through the upper steel part, namely the limiting bolt 2.
[0047] The limit bolt 2 can be elliptical (the radial interface of the main body is elliptical) to simultaneously meet the different design requirements for axial and lateral limit clearances of the unit. The limit bolt 2 is rigidly fixedly connected to the upper steel part 1.
[0048] There is a gap between the bottom surface of the limiting bolt 2 and the upper surface of the lower steel part 5, which is a vertical limiting gap; there is a gap between the side surface of the limiting bolt 2 and the inner wall of the conical limiting steel part 4, which is a lateral limiting gap.
[0049] If the marine propulsion main engine and gearbox are considered as a rigid linear system, the displacement of the unit at the vibration isolator position can be calculated based on the actual interface compensation, thereby determining the required limit value. The design parameters of the vibration isolator limit clearance can then be determined based on the calculated limit value.
[0050] Based on the above design structure, the specific dimensions of the limiting bolt 2 that meets the load-bearing strength requirements can be calculated. The specific dimensions of the tapered limiting steel component 4 can be obtained based on the limiting gap.
[0051] At this point, all key design parameters for the vibration isolation system for marine propulsion gearboxes have been completed, and the design is now finished.
[0052] Example
[0053] For a marine propulsion main engine and gearbox assembly, the design method of this invention is used to design a vibration isolation system, specifically including the following steps:
[0054] 1. Determine all excitation frequencies of the marine propulsion main engine and gearbox: The excitation in the low frequency range of the unit is the rotor speed, with speeds of 1000 r / min and 200 r / min, corresponding to excitation frequencies of 16.7 Hz and 3.3 Hz.
[0055] 2. Select the natural frequency of the equipment's vibration isolation system to avoid various excitation frequencies: To maximize the avoidance rate, a natural frequency of 10Hz is selected. This frequency can ensure the vibration isolation effect to a certain extent, and at the same time, it can ensure that the rigidity of the unit system is large enough.
[0056] 3. Calculate the support stiffness of the vibration isolation system based on the equipment mass: The unit has a mass of 30t, and the support stiffness of the vibration isolation system can be calculated to be 1.3E8N / m.
[0057] 4. Determine the bottom surface installation conditions of the overall floating raft support for the propulsion main unit and gearbox: Based on the unit layout, the design of the overall floating raft structure was completed as follows: Figure 3 As shown in the figure. The section with the cross-section is designed as an area where vibration isolators can be installed.
[0058] 5. Arrange vibration isolators and determine their quantity, load, dimensions, and interface dimensions: Based on the bottom surface, a suitable quantity of 10 vibration isolators is arranged, as shown in the following positions. Figure 4 As shown, the arrangement of this vibration isolation system ensures that the center of stiffness coincides with the center of gravity of the unit. The external dimensions are 300mm*300mm, and the interface dimensions are 260mm*260mm.
[0059] 6. Determine the stiffness and load of individual vibration isolators based on the overall system support stiffness and mass: The total system stiffness is 1.3E8 N / m, there are 10 vibration isolators in total, and the stiffness of an individual vibration isolator is 1.3E7 N / m. The total system mass is 30t, and the load on an individual vibration isolator is 3t.
[0060] 7. Establish a finite element model of the main unit including the vibration isolation system, such as... Figure 5 As shown.
[0061] 8. Calculate the displacement of each interface of the unit under the simultaneous consideration of the ship's roll and pitch operating conditions and the gearbox overturning moment: After finite element modeling and calculation, the displacement calculation results of each interface under the current vibration isolation system design scheme are shown in the table below.
[0062] Table 1 Interface Displacement
[0063]
[0064] 9. Compare the calculated values with the actual allowable displacement compensation values to find the position with the largest difference in displacement compensation among all interfaces: The calculated lateral displacement of interface 5 is 4.51mm, and the maximum radial displacement compensation of the interface at this position cannot exceed 2.8mm, which cannot meet the compensation conditions of the interface at this position.
[0065] 10. Considering the equipment as a linear system, the required vibration isolator limiting clearances are deduced based on the allowable compensation for interface displacement: According to the actual displacement compensation conditions of interface 5, the lateral limiting displacement is 1.2mm, the axial limiting displacement is 2.3mm, and the vertical limiting displacement is 0.9mm. The vertical limiting clearance needs to consider the deformation of the vibration isolator under load; the static deformation under vertical load is 4.5mm. Taking into account rubber creep, the calculated vertical clearance is 5.4mm. Therefore, the lateral, axial, and vertical limiting clearances of the vibration isolator are 1.2mm, 2.3mm, and 5.4mm, respectively.
[0066] 11. The key design parameters of the vibration isolation system are known.
[0067] 12. Determine the vibration isolator structure that meets the strength requirements based on the design parameters: The design structure is as follows: Figures 6-8 As shown, where Figure 6 A front view of the vibration isolator structure design. Figure 7 Design a top view of the vibration isolator structure. Figure 8 Isometric drawings for vibration isolator structural design.
[0068] 13. Ensure that the external dimensions and other parameters meet the strength requirements.
[0069] 14. Complete the design of a vibration isolation system for marine propulsion gearboxes.
[0070] The above examples of the present invention are merely illustrative of the computational model and process of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.
Claims
1. A design method for a vibration isolation system structure for a marine propulsion gearbox, characterized in that, include: First, determine the excitation frequency of the marine propulsion main engine and gearbox under various operating conditions. Based on the excitation frequency, determine the vertical natural frequency f of the vibration isolation system. Simultaneously, based on the overall mass m above the vibration isolation system, the support stiffness K of the vibration isolation system is calculated. The selection of the vertical natural frequency is based on the constraint of the support stiffness K; The design includes an overall support raft for the propulsion main unit and gearbox. The vibration isolation system includes multiple vibration isolators. The vibration isolators are arranged according to the installation bottom surface and space of the raft, and the number of vibration isolators is determined. Based on the number of vibration isolators in the vibration isolation system and the support stiffness of the vibration isolation system, the stiffness value and load of a single vibration isolator are calculated; based on the stiffness of a single vibration isolator, the minimum allowable size of the vibration isolator is determined, and combined with the design conditions of the unit mounting surface, the external dimensions and interface dimensions of the vibration isolator are determined. At this point, the location, quantity, size, stiffness, and load of the vibration isolation system have been determined, and a finite element model including the propulsion main unit, gearbox, floating raft base, and vibration isolation system has been established. Based on marine operating conditions, the overturning moment of the gearbox is calculated using the power, speed, and self-weight of the unit under rated operating conditions. Simultaneously, the displacement of each interface of the unit is calculated. The displacement compensation amount at each interface position is determined according to the design. Comparing the calculated interface displacement values under marine operating conditions and gearbox overturning moment operating conditions, if the actual interface displacement compensation amount is greater than the calculated value, it indicates that the current operating conditions are not sufficient to meet the normal operating conditions of the unit, and there is a possibility that excessive interface displacement may lead to unit failure. Therefore, the vibration isolator with the following structure is designed: The vibration isolator includes an upper steel component (1), a lower steel component (5), and a limit bolt. (2) Conical limiting steel piece (4) and conical rubber ring (3); The conical rubber ring (3) is set between the lower steel piece (5) and the upper steel piece (1) for vibration isolation; The lower steel piece (5) is rigidly connected to the conical limiting steel piece (4), and the conical limiting steel piece (4) is a steel piece; The limiting bolt (2) is rigidly fixedly connected to the upper steel piece (1) and cooperates with the conical limiting steel piece (4) for limiting; A gap is left between the bottom surface of the limiting bolt (2) and the upper surface of the lower steel piece (5), which is the vertical limiting gap; A gap is left between the side of the limiting bolt (2) and the inner wall of the conical limiting steel piece (4), which is the lateral limiting gap; Based on the rigid linear system, the unit displacement at the position of the vibration isolator is calculated back according to the actual interface compensation amount, thereby determining the required limit value; the design parameters of the vibration isolator limit gap are determined according to the calculated limit value; the specific dimensions of the limit bolt (2) that meets the bearing strength are obtained according to the vibration isolator structure and design parameters; the specific dimensions of the conical limit steel part (4) are obtained according to the limit gap.
2. The design method for a vibration isolation system structure for a marine propulsion gearbox according to claim 1, characterized in that, The vertical natural frequency f of the vibration isolation system is determined based on the excitation frequency and is selected outside the frequency avoidance rate range.
3. The design method for a vibration isolation system structure for a marine propulsion gearbox according to claim 2, characterized in that, The frequency avoidance rate is selected as 20%.
4. The design method for a vibration isolation system structure for a marine propulsion gearbox according to claim 1, characterized in that, The formula for calculating the support stiffness of a floating raft vibration isolation system is as follows: .
5. The design method for a vibration isolation system structure for a marine propulsion gearbox according to claim 1, characterized in that, In the process of arranging vibration isolators according to the bottom surface and space of the floating raft and determining the number of vibration isolators, the arrangement of vibration isolators should try to ensure that the stiffness center and the center of gravity coincide; if there is no coincidence condition, the coincidence deviation shall not exceed 10%.
6. The design method for a vibration isolation system structure for a marine propulsion gearbox according to claim 1, characterized in that, According to marine operating conditions, when calculating the overturning moment of the gearbox based on the power, speed, and self-weight of the unit under rated operating conditions, the propulsion equipment corresponding to the main propulsion unit must meet the operating conditions of 45° roll and 10° pitch.