Method for controlling critical rotating speed of rotor by adjusting rigidity of bearing supporting system

Abstract

The invention discloses a method for controlling the critical rotating speed of a rotor by adjusting the rigidity of a bearing supporting system, and relates to the field of heavy rotating equipment with a bearing support. The method for controlling the critical rotating speed of the rotor by adjusting the rigidity of the bearing supporting system comprises the following steps that a rigidity model of the bearing supporting system is built, a rigidity calculation point is marked as O1, and supporting points at the two ends are marked as O2 and O3; collecting the distance a between the O1 and the O2, and collecting the distance b between the O1 and the O3; the bearing rigidity K2 at the O2 position is collected, and the bearing rigidity K3 at the O3 position is collected; according to a, b, K2 and K3, the bearing supporting rigidity K0 at the position of O1 is obtained; the rigidity KM1 borne by the mass M1 at the position O1 is obtained according to the bearing supporting rigidity K0 at the position O1 and the transverse rigidity K1 of the shaft at the position O1; and obtaining the critical rotating speed of the rotor according to the M1 and the KM1. According to the method, the rigidity borne by the mass of the point is calculated, the critical rotating speed of the rotor is obtained, the critical rotating speed of the rotor can be controlled by adjusting the rigidity of a bearing supporting system, and resonance is avoided.

Description

Technical Field

[0001] This invention relates to the field of heavy-duty rotating equipment with bearing support, and particularly to a method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system. Background Technology

[0002] Rotating machinery has a wide range of applications. Typical rotating equipment designs consist of a rotating shaft and bearings. The shaft system, composed of the shaft and its support, has inherent frequency characteristics, which raises the issue of the rotor's critical speed. Standard specifications for the design and manufacture of steam turbines, water pumps, centrifugal compressors, and other similar equipment stipulate critical speed avoidance rates to prevent resonance. The stiffness characteristics of the bearing support are a crucial factor affecting the critical speed of the shaft system. Therefore, designing an adjustable stiffness bearing support system is an important approach and method for adjusting the critical speed of the shaft system.

[0003] When the rotor mass is relatively light, the bearings and their support system have a relatively small impact on the first-order critical speed of the rotor system. However, when the rotor mass is relatively heavy, the support stiffness of the bearings and their support system has a significant impact on the critical speed of the rotor system. For example, the rotor of a high-power steam turbine can weigh several tons, and its design speed is generally above 3000 rpm. Such rotors often operate at speeds that are close to critical and are called flexible rotors.

[0004] Traditional bearing support systems have fixed, non-adjustable support stiffness, typically designed to be high to withstand / suppress vibrations transmitted from the equipment. However, the stiffness of bearings (specifically sliding bearings) is finite, and its value is difficult to increase further after reaching a certain order of magnitude. Therefore, according to the basic vibration formula ω=√(K / M), limited by the sliding bearing stiffness, the natural frequency (critical rotor speed) decreases as the rotor mass increases. Consequently, the first-order critical speed of a large-mass rotor is not high. The design technology for large-mass flexible rotors is complex, requiring repeated iterative calculations. Furthermore, units often require multi-objective operating condition adjustments at different speeds, making conventional design methods prone to falling into the resonance region. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem solved by this invention is: how to control the critical speed of the rotor by adjusting the stiffness of the bearing support system.

[0006] To achieve the above objectives, the present invention provides a method for controlling the critical speed of a rotor by adjusting the stiffness of a bearing support system, comprising the following steps: Build a stiffness model of the bearing support system, and denote the stiffness calculation point as O1, and the support points at both ends as O2 and O3; Collect the distance 'a' between O1 and O2, and the distance 'b' between O1 and O3; Collect the bearing stiffness K2 at point O2, and collect the bearing stiffness K3 at point O3; Based on a, b, K2, and K3, obtain the bearing support stiffness K0 at point O1; Based on the bearing support stiffness K0 at O1 and the shaft's own lateral stiffness K1 at O1, the stiffness KM1 of the mass M1 at O1 is obtained. Based on M1 and KM1, the critical speed of the rotor is obtained.

[0007] By adopting the above technical solution, a stiffness model of the bearing support system is built and relevant data and stiffness are collected. According to the stiffness of the rotor system of the rotating equipment, it mainly consists of the lateral stiffness of the shaft itself and the stiffness of the bearing support, and the relationship between the two is series stiffness, while the stiffness between the bearings is parallel stiffness. Based on this, the stiffness of the mass at that point can be calculated, and thus the critical speed of the rotor can be obtained, providing a basis for adjusting the stiffness of the bearing support system to control the critical speed of the rotor. Therefore, this method can control the critical speed of the rotor by adjusting the stiffness of the bearing support system, thereby avoiding resonance.

[0008] In one implementation, the bearing support stiffness K0 at point O1 is obtained based on a, b, K2, and K3, specifically including: The bearing support stiffness K0 at point O1 is calculated using the first formula, where the first formula is: 1 / K0 = (1 / K2)b 2 / (a+b) 2 +(1 / K3)a 2 / (a+b) 2 .

[0009] By adopting the above technical solution, a stiffness model of the bearing support system is built, and the distances a and b and the bearing support stiffness K2 and K3 are collected. The bearing support stiffness K0 at O1 is calculated using the first formula, which provides basic data for subsequent calculation of the stiffness of mass M1 at O1 and the critical speed of the rotor, and enables more accurate control of the rotor critical speed.

[0010] In one embodiment, the stiffness KM1 of the mass M1 at O1 is obtained based on the bearing support stiffness K0 at O1 and the shaft's own lateral stiffness K1 at O1, specifically including: The stiffness KM1 of the mass M1 at point O1 is calculated using the second formula, where the second formula is: KM1 = (K0 * K1) / (K0 + K1).

[0011] By adopting the above technical solution, after building a stiffness model of the bearing support system and collecting relevant distance and stiffness data, the bearing support stiffness K0 at point O1 is calculated using the first formula. Based on this, the stiffness KM1 of the mass M1 at point O1 is calculated using the second formula in combination with the lateral stiffness K1 of the shaft itself at point O1. This can accurately determine the stiffness of the mass point, thus providing a basis for the subsequent accurate calculation of the rotor critical speed. It helps to control the rotor critical speed by adjusting the bearing stiffness and avoid large-mass flexible rotors from falling into the resonance region.

[0012] In one embodiment, the rotor critical speed is obtained based on M1 and KM1, specifically including: The critical speed of the rotor is calculated using a third formula, wherein the third formula is: ω=√(KM1 / M1).

[0013] By adopting the above technical solution, after calculating KM1 using the first and second formulas, the rotor critical speed is calculated using the above formulas, thereby achieving accurate acquisition of the rotor critical speed. This facilitates targeted control and adjustment of the rotor critical speed, preventing the large-mass flexible rotor from falling into the resonance region.

[0014] In one embodiment, the method for controlling rotor criticality further includes the following steps: The critical speed of the rotor can be adjusted by adjusting K2 and K3.

[0015] By adopting the above technical solution, the critical speed of the rotor can be adjusted, avoiding the large-mass flexible rotor from falling into the resonance region, and solving the problem of controlling the critical speed of the rotor by adjusting the stiffness of the bearing support system.

[0016] In one implementation, adjusting K2 and K3 specifically includes: A tie rod is connected in series with the bearing support stiffness to form a comprehensive stiffness; The overall stiffness is adjusted by adjusting the stiffness of the tie rod support.

[0017] By adopting the above technical solution, the structure is adjusted by using a bearing tie rod, that is, a tie rod is connected in series with the bearing oil film support stiffness, thus changing the overall stiffness of the support position.

[0018] In one embodiment, adjusting the stiffness of the tie rod support specifically includes: The stiffness of the tie rod support is calculated using the fourth formula, where the fourth formula is: K = E * A / L, where K is the stiffness of the tie rod support, E is the modulus of elasticity, A is the cross-sectional area of ​​the tie rod, and L is the length of the tie rod. Based on A and L, the stiffness K of the tie rod support is obtained.

[0019] By adopting the above technical solution, the stiffness K of the tie rod support is obtained, thereby changing the overall stiffness of the support position. At the same time, the strength of the support is maintained, ensuring the reliability and safety of equipment operation.

[0020] In one implementation, calculating A and L specifically includes: A and L are calculated using the fifth formula, where the fifth formula is: N = E * A * X / L δ=N / A Where X represents the deformation, δ is within the allowable strength range of the material, and N is the force value at the support point.

[0021] By adopting the above technical solution, the relevant parameters of the tie rod can be accurately calculated, and the tie rod support stiffness can be precisely adjusted. Ultimately, the stiffness of the bearing support system can be effectively adjusted, thereby better controlling the rotor critical speed and avoiding resonance.

[0022] In one implementation, it further includes: The value of δ is kept within the designed safety range; Based on δ and N, obtain A; Based on A, K, and E, obtain L.

[0023] By adopting the above technical solution, when calculating and selecting, first, by taking the value of δ within the design safety value (leaving a safety factor), and then distributing the force N to the support point according to the mass and position of the rotor, the cross-sectional area A of the rod can be calculated; since the stiffness K requirement of the rod has been set, and E and A have been determined, the length of the rod can be calculated according to the aforementioned fourth formula.

[0024] In one implementation, a and b are the same; Alternatively, a and b may be different.

[0025] By adopting the above technical solution, this method can be applied to scenarios with different spacing.

[0026] In summary, the present invention has at least one of the following beneficial technical effects: 1. By constructing a stiffness model of the bearing support system and collecting relevant data and stiffness, and considering that the stiffness of the rotor system of the rotating equipment mainly consists of the lateral stiffness of the shaft itself and the stiffness of the bearing support, and that the relationship between the two is a series stiffness, while the stiffness between the bearings is a parallel stiffness, the stiffness of the mass at that point can be calculated, thereby obtaining the rotor's critical speed. This provides a basis for adjusting the stiffness of the bearing support system to control the rotor's critical speed. Therefore, this method can control the rotor's critical speed by adjusting the stiffness of the bearing support system, thereby avoiding resonance. 2. By adjusting the bearing stiffness, the rotor critical speed is changed. By adjusting the structure and using a bearing tie rod, a tie rod is connected in series with the bearing oil film support stiffness, thus changing the overall stiffness of the support position. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating a method for controlling the critical speed of a rotor by adjusting the stiffness of a bearing support system, as described in an embodiment of the present invention. Figure 2 This is a stiffness model of the bearing support system according to an embodiment of the present invention; Figure 3 This is a structural diagram showing the adjusted structure according to an embodiment of the present invention.

[0028] In the diagram: 1-bearing housing, 2-bearing housing cover, 3-bearing, 4-horizontal tie rod, 5-vertical tie rod. Detailed Implementation

[0029] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] The method for controlling the rotor critical speed by adjusting the stiffness of the bearing support system in this embodiment of the invention is described in [reference needed]. Figure 1 , Figure 2 As shown, the method for controlling the critical speed of the rotor by adjusting the stiffness of the bearing support system includes the following steps: 101: Build a stiffness model of the bearing support system, and denote the stiffness calculation point as O1, and the support points at both ends as O2 and O3; 102: Collect the distance 'a' between O1 and O2, and the distance 'b' between O1 and O3; 103: Collect the bearing stiffness K2 at point O2, and collect the bearing stiffness K3 at point O3; 104: Based on a, b, K2, and K3, obtain the bearing support stiffness K0 at point O1; 105: Based on the bearing support stiffness K0 at O1 and the shaft's own lateral stiffness K1 at O1, obtain the stiffness KM1 of the mass M1 at O1; 106: Obtain the rotor critical speed based on M1 and KM1.

[0031] Therefore, this invention establishes a stiffness model of the bearing support system and collects relevant data and stiffness. Based on the stiffness of the rotor system of the rotating equipment, which mainly consists of the lateral stiffness of the shaft itself and the stiffness of the bearing support, and the relationship between the two is series stiffness, while the stiffness between the bearings is parallel stiffness, the stiffness of the mass at that point can be calculated, thereby obtaining the critical speed of the rotor. This provides a basis for adjusting the stiffness of the bearing support system to control the critical speed of the rotor. Therefore, this method can control the critical speed of the rotor by adjusting the stiffness of the bearing support system, thereby avoiding resonance.

[0032] Preferably, a specific method for calculating the critical speed of a rotor is provided: The bearing support stiffness K0 at point O1 is calculated using the first formula, where the first formula is: 1 / K0 = (1 / K2)b 2 / (a+b) 2 +(1 / K3)a 2 (a+b) 2 ; The stiffness KM1 of the mass M1 at point O1 is calculated using the second formula, where the second formula is: KM1 = (K0 * K1) / (K0 + K1); The critical speed of the rotor is calculated using a third formula, wherein the third formula is: ω=√(KM1 / M1).

[0033] Specifically, in the model building steps, a stiffness model of the bearing support system is built, with the stiffness calculation point denoted as O1, and the support points at both ends denoted as O2 and O3. This model can be built using computer simulation or an actual physical model. Computer simulation offers the advantage of easy parameter modification and adjustment, while a physical model provides a more intuitive representation of the system's actual condition.

[0034] In the data acquisition step, the distance 'a' between O1 and O2 and the distance 'b' between O1 and O3 are acquired. Distance acquisition can be achieved using tools such as a laser rangefinder or vernier calipers. Laser rangefinders are suitable for measuring larger distances, offering high accuracy and speed; vernier calipers are suitable for precise measurements of smaller distances. Simultaneously, the bearing support stiffness K2 at O2 and the bearing support stiffness K3 at O3 are acquired. Stiffness can be acquired using professional stiffness testing equipment, calculating stiffness by applying a certain force to the bearing and measuring its deformation.

[0035] In the stiffness calculation step, the bearing support stiffness K0 at point O1 is obtained based on a, b, K2, and K3. Specifically, the bearing support stiffness K0 at point O1 is calculated using the first formula: 1 / K0 = (1 / K2)b 2 / (a+b)2 +(1 / K3)a 2 / (a+b) 2 This formula is derived based on mechanical principles and can accurately calculate the bearing support stiffness at point O1. Then, based on the bearing support stiffness K0 at point O1 and the shaft's own lateral stiffness K1 at point O1, the stiffness KM1 experienced by the mass M1 at point O1 is obtained. Specifically, this is calculated using the second formula: KM1 = (K0 * K1) / (K0 + K1). This formula considers the combined effect of the bearing support stiffness and the shaft's own lateral stiffness.

[0036] In the step of calculating the critical speed, the rotor's critical speed is obtained based on M1 and KM1. Specifically, the rotor's critical speed is calculated using the third formula, ω=√(KM1 / M1). This formula is based on the principles of vibration and can accurately calculate the rotor's critical speed.

[0037] Preferably, a tie rod is connected in series with the bearing support stiffness to form a comprehensive stiffness; By adjusting the stiffness of the tie rod support, the overall stiffness can be adjusted, thereby regulating the critical speed of the rotor. For details, see Figure 3 As shown, an optimized and improved scheme based on the traditional bearing housing is adopted, with tie rods arranged vertically and horizontally; The vertical tie rod 5 needs to be adjusted by measuring the gap between the bearing 1 and the bearing housing 3 during installation. The bearing housing cover 2 and the bearing housing 1 clamp the bearing 3. There are two transverse tie rods 4, arranged symmetrically on both sides, with the same preload, and the preload is adjusted by measuring the gap between bearing 3 and bearing housing 1.

[0038] Furthermore, a specific method for calculating the stiffness of a tie rod support: The stiffness of the tie rod support is calculated using the fourth formula, where the fourth formula is: K = E * A / L, where K is the stiffness of the tie rod support, E is the modulus of elasticity, A is the cross-sectional area of ​​the tie rod, and L is the length of the tie rod. Based on A and L, obtain the stiffness K of the tie rod support; A and L are calculated using the fifth formula, where the fifth formula is: N = E * A * X / L δ=N / A Where X represents the amount of deformation, δ is within the allowable strength range of the material, and N is the force value at the support point; The value of δ is kept within the designed safety range; Based on δ and N, obtain A; Based on A, K, and E, obtain L.

[0039] Specifically, a calculation embodiment is provided: The required stiffness of the tie rod is set at 1*10e8 N / m, and the required tensile force at one end is 1750 kgf. Note that the stiffness value of the tie rod is calculated based on the target critical speed using the aforementioned stiffness synthesis formula, while the tensile force of the rod is mainly determined by the mass and distribution of the rotor components it needs to support.

[0040] According to N=E*A*X / L, δ=N / A, where δ is taken to be no greater than 70MPa; Therefore, the area A is not less than 17500 / 70e6 = 2.5e-4m. 2 =250mm 2 The required rod diameter is 17.8mm; The elastic modulus is calculated based on steel, E=2*10e11. In fact, the stiffness K = E * A / L, substituting this into the equation, we get the required length of the 18mm rod. L = 2 * 10e11 * 2.5e-4 / 1 * 10e8 N / m = 5e-1m = 500mm, Deformation amount X=17500 / 1*10e8=1.74e-4m=0.174mm The actual design uses two tie rods, each 12mm in diameter, tightened with M12 screws.

[0041] M12 cross-section calculation: 6 2 *3.14*2=226mm 2 Slightly less than 250mm 2 In practice, two M12 screws, each 200mm long, made of 35CrMo, are selected. Their static loads are as follows: δ=N / A=20000 / 226=88.5MPa The resulting stiffness: K=E*A / L=2*10e11*226*10e-3 / 200=2.26e8 N·m This stiffness value is incorporated into the shaft stiffness, effectively reducing the system stiffness. Furthermore, the shaft stiffness can be easily adjusted by changing the rod length L through adjusting the helix height of M12.

[0042] This invention, through precise model building, data acquisition, and formula calculation, can accurately calculate the critical speed of the rotor. Furthermore, by adjusting the stiffness of the bearing support system, especially by introducing and adjusting the stiffness of the tie rod support, the critical speed of the rotor can be flexibly changed, preventing the large-mass rotor from falling into the resonance region under different operating conditions. This improves the safety and stability of rotating equipment and, compared to traditional fixed stiffness design methods, has stronger adaptability and adjustability.

[0043] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for controlling the critical speed of a rotor by adjusting the stiffness of a bearing support system, characterized in that, It includes the following steps: Build a stiffness model of the bearing support system, and denote the stiffness calculation point as O1, and the support points at both ends as O2 and O3; Collect the distance 'a' between O1 and O2, and the distance 'b' between O1 and O3; Collect the bearing support stiffness K2 at point O2, and collect the bearing support stiffness K3 at point O3; Based on a, b, K2, and K3, obtain the bearing support stiffness K0 at point O1; Based on the bearing support stiffness K0 at O1 and the shaft's own lateral stiffness K1 at O1, the stiffness KM1 of the mass M1 at O1 is obtained. Based on M1 and KM1, the critical speed of the rotor is obtained.

2. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 1, characterized in that, Based on a, b, K2, and K3, the bearing support stiffness K0 at point O1 is obtained, specifically including: The bearing support stiffness K0 at point O1 is calculated using the first formula, where the first formula is: 1 / K0=(1 / K2)b 2 / (a+b) 2 +(1 / K3)a 2 / (a+b) 2 。 3. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 2, characterized in that, Based on the bearing support stiffness K0 at O1 and the shaft's own lateral stiffness K1 at O1, the stiffness KM1 experienced by the mass M1 at O1 is obtained, specifically including: The stiffness KM1 of the mass M1 at point O1 is calculated using the second formula, where the second formula is: KM1 = (K0 * K1) / (K0 + K1).

4. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 3, characterized in that, Based on M1 and KM1, the critical speed of the rotor is obtained, specifically including: The critical speed of the rotor is calculated using a third formula, wherein the third formula is: ω=√(KM1 / M1).

5. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 1, characterized in that, The method for controlling rotor criticality also includes the following steps: The critical speed of the rotor can be adjusted by adjusting K2 and K3.

6. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 5, characterized in that, Adjustments to K2 and K3 include: A tie rod is connected in series with the bearing support stiffness to form a comprehensive stiffness; The overall stiffness is adjusted by adjusting the stiffness of the tie rod support.

7. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 6, characterized in that, Adjusting the stiffness of the tie rod support specifically includes: The stiffness of the tie rod support is calculated using the fourth formula, where the fourth formula is: K = E * A / L, where K is the stiffness of the tie rod support, E is the modulus of elasticity, A is the cross-sectional area of ​​the tie rod, and L is the length of the tie rod. Based on A and L, the stiffness K of the tie rod support is obtained.

8. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 7, characterized in that, Calculating A and L specifically includes: A and L are calculated using the fifth formula, where the fifth formula is: N = E * A * X / L δ=N / A Where X represents the deformation, δ is within the allowable strength range of the material, and N is the force value at the support point.

9. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 8, characterized in that, Also includes: The value of δ is kept within the designed safety range; Based on δ and N, obtain A; Based on A, K, and E, obtain L.

10. The method for controlling the critical speed of a rotor by adjusting the stiffness of the bearing support system as described in claim 8, characterized in that: a and b are the same; Alternatively, a and b may be different.

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