Method for inhibiting periodic fluctuation of shafting vibration of nuclear power unit

Abstract

The application provides a method for inhibiting shaft vibration periodic fluctuation of a nuclear power unit, comprising the following steps: obtaining installation and operation parameters of a unit with periodic fluctuation, determining a thickness model by taking the installation and operation parameters as model boundary conditions, determining a relationship parameter between an oil inlet temperature of lubricating oil and a shaft neck temperature difference; determining a change relationship between the shaft neck temperature difference and the oil inlet temperature of lubricating oil and solving a curve change slope according to the thickness model and the relationship parameter between the oil inlet temperature of lubricating oil and the shaft neck temperature difference; determining an optimal lubricating oil temperature adjustment target value when the change slope in a change range is less than a preset threshold value in a preset lubricating oil temperature adjustment range; repeatedly adjusting an opening degree and a set value of a lubricating oil temperature adjustment valve according to a preset lubricating oil temperature adjustment range and a preset lubricating oil temperature adjustment amplitude until the lubricating oil temperature reaches the optimal lubricating oil temperature adjustment target value. The application inhibits the periodic fluctuation by inhibiting the rotor circumferential temperature difference.

Description

A method for suppressing periodic fluctuations in shaft vibration in nuclear power units Technical Field

[0001] This invention relates to the field of turbine generator vibration technology, and in particular to a method for suppressing periodic fluctuations in shaft vibration in nuclear power units. Background Technology

[0002] Currently, one-third of the Arabella-type steam turbine generator sets used in domestic nuclear power plants, manufactured by Dongfang Electric using technology imported from Alstom, exhibit periodic vibration fluctuations. These fluctuations manifest as periodic changes in the amplitude and phase of vibrations in multiple bearings during operation, with each fluctuation cycle lasting approximately 4.5 hours and exhibiting excellent repeatability. These fluctuations can persist for extended periods. From the shaft system perspective, the vibration fluctuations are concentrated on the generator side, with significant fluctuations observed in the generator and the adjacent low-pressure rotor, while the high-pressure side of the steam turbine shows virtually no noticeable vibration fluctuations.

[0003] The existence of this problem affects the operational stability of steam turbine generators. Furthermore, despite long-term research, vibration experts in domestic research institutes and nuclear power companies have yet to determine its root cause and a complete solution. However, research indicates that the thermal effect caused by synchronous whirling of the shaft within a small gap is related to this phenomenon. The general principle is as follows: when the shaft whirls within the small gap, it leads to uneven distribution of the oil film thickness on the journal surface. Due to the viscous shearing effect of the oil film within the small gap, a circumferential temperature difference occurs between the shaft surface and the lubricating oil film. When this temperature difference reaches a certain level, the rotor will undergo thermal bending. This thermal bending generates additional unbalanced forces on the rotor, causing vibration changes. A larger temperature difference results in greater vibration fluctuations. Therefore, the core of suppressing periodic vibration fluctuations is to suppress the circumferential temperature difference of the rotor. Summary of the Invention

[0004] The purpose of this invention is to propose a method for suppressing periodic vibration fluctuations in the shaft system of a nuclear power unit, thereby solving the technical problem of how to suppress periodic vibration fluctuations by suppressing the circumferential temperature difference of the rotor.

[0005] On the one hand, a method for suppressing periodic fluctuations in the shaft system of a nuclear power unit is provided, including:

[0006] The installation and operation parameters of the unit exhibiting periodic fluctuations are obtained, and the installation and operation parameters are used as boundary conditions to determine the thickness model. The thickness model is used to determine the average thickness of the oil film during the whirl motion of the rotating shaft within the small gap.

[0007] The relationship parameters between the lubricating oil inlet temperature and the journal temperature difference are determined based on the preset shaft surface temperature distribution model.

[0008] Based on the thickness model and the relationship parameters between the lubricating oil inlet temperature and the journal temperature difference, determine the relationship between the journal temperature difference and the lubricating oil inlet temperature, and solve for the slope of the curve.

[0009] Within the preset lubricating oil temperature adjustment range, the optimal lubricating oil temperature adjustment target value is determined when the slope of change within the range is less than the preset threshold.

[0010] Within the preset unit lubricating oil temperature adjustment range, the opening and set value of the lubricating oil temperature regulating valve are repeatedly adjusted according to the preset lubricating oil temperature adjustment range each time, and the unit's operating status parameters are continuously observed until the lubricating oil temperature reaches the optimal lubricating oil temperature adjustment target value.

[0011] Preferably, the thickness model specifically includes:

[0012]

[0013]

[0014]

[0015]

[0016]

[0017] Where h is the oil film thickness at point P, S is the thinnest point of the oil film on the rotating shaft, β is the angle between point S and the horizontal position, and point S is the initial position in the circumferential direction. The angle between any point P on the rotating shaft surface and point S is α. x and A y The vortex amplitudes in the x and y directions are Ф respectively. x and Ф y Let e0 be the initial phase in the x and y directions, e0 be the static eccentricity, ω be the vortex angular velocity, and R be the initial phase in the x and y directions, respectively. j Let C be the radius of the rotating shaft, e be the dynamic eccentricity, and C be the radius of the rotating shaft. b For the radius gap, θ j Center O of the rotating shaft j The angle with the horizontal position, N is the number of time points within one vortex cycle, t is the time, and i is the number of time points within N.

[0018] Preferably, the thickness model further includes:

[0019]

[0020] in, Let be the average oil film thickness at point P, N be the number of time nodes within one eddy cycle, h be the oil film thickness at point P, ω be the eddy angular velocity, t be the time, and i be the number of time nodes within N.

[0021] Preferably, the surface temperature distribution model of the rotating shaft includes:

[0022]

[0023]

[0024]

[0025] Where ρ and c are the oil density and specific heat within the micro-gap, respectively, and T is the oil film temperature. b and T j Here, τ represents the temperature of the bearing pad and the shaft, respectively; τ is the viscous shear force; μ is the oil viscosity; and H is the convective heat transfer coefficient between the oil film and the shaft / bearing pad. T represents the temperature difference between the oil film and the ambient temperature. e T0 is the ambient temperature, T0 is the oil inlet temperature, and ΔT is the oil film temperature rise.

[0026] Preferably, the parameters for determining the relationship between the lubricating oil inlet temperature and the journal temperature difference specifically include:

[0027] The average temperature at the same point at different times during one revolution of the shaft is taken as the surface temperature of the shaft at that point, as shown in the following formula:

[0028]

[0029] in, ω is the average temperature, N is the whirl angular velocity, T is the number of time points in one whirl cycle, and T is the oil film temperature.

[0030] Preferably, the safe range for each adjustment of the lubricating oil temperature is 44℃~46℃.

[0031] Preferably, the lubricating oil temperature is adjusted in increments of ±2°C.

[0032] Preferably, the unit's operating parameters include at least the unit's vibration after temperature adjustment, bearing temperature, lubricating oil cooler outlet temperature, and main oil tank oil temperature change.

[0033] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0034] The method for suppressing periodic vibration fluctuations in the shaft system of nuclear power units provided by this invention offers an effective way to alleviate the problem of periodic vibration fluctuations in the turbine generator shaft system during operation, especially when the periodic fluctuations in the turbine generator shaft system have been difficult to eradicate for a long time. The method has shown significant results in field applications and has improved the operational stability of the equipment. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0036] Figure 1 is a schematic diagram of the main process of a method for suppressing periodic fluctuations in the shaft system of a nuclear power unit according to an embodiment of the present invention.

[0037] Figure 2 is a schematic diagram of the synchronous vortex elliptical trajectory in an embodiment of the present invention.

[0038] Figure 3 is a thermal balance diagram of the oil film in an embodiment of the present invention.

[0039] Figure 4 is a schematic diagram showing the effect of bearing lubricating oil inlet temperature on journal temperature difference in an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] Figure 1 shows a schematic diagram of an embodiment of a method for suppressing periodic vibration fluctuations in the shaft system of a nuclear power unit provided by the present invention. In this embodiment, the method includes the following steps:

[0042] Step S1: Obtain the installation and operation parameters of the unit exhibiting periodic fluctuations, and use the installation and operation parameters as model boundary conditions to determine the thickness model. The thickness model is used to determine the average oil film thickness during the whirl motion of the rotating shaft within the small gap. That is, the installation and operation parameters of the unit exhibiting periodic fluctuations are used as model boundary conditions to establish an average oil film thickness model during the whirl motion of the rotating shaft within the small gap.

[0043] In a specific embodiment, the thickness model specifically includes:

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] Where h is the oil film thickness at point P, S is the thinnest point of the oil film on the rotating shaft, β is the angle between point S and the horizontal position, and point S is the initial position in the circumferential direction. The angle between any point P on the rotating shaft surface and point S is α. x and A y The vortex amplitudes in the x and y directions are Ф respectively. x and Ф y Let e0 be the initial phase in the x and y directions, e0 be the static eccentricity, ω be the vortex angular velocity, and R be the initial phase in the x and y directions, respectively. j Let C be the radius of the rotating shaft, e be the dynamic eccentricity, and C be the radius of the rotating shaft. b For the radius gap, θ j Center O of the rotating shaft j The angle with the horizontal position, N is the number of time points within one vortex cycle, t is the time, and i is the number of time points within N.

[0050] The thickness model further includes:

[0051]

[0052] in, Let be the average oil film thickness at point P, N be the number of time nodes within one eddy cycle, h be the oil film thickness at point P, ω be the eddy angular velocity, t be the time, and i be the number of time nodes within N.

[0053] Understandably, as shown in Figure 2, under the action of unbalanced forces, the shaft will rotate around its static equilibrium position O within a tiny gap. js It vortexes along an elliptical trajectory. In the diagram, point O... b O j These are the center of the tile and the center of the rotation axis, respectively. Define the center of the rotation axis at time t = 0 as being located at point O. j0 The position is such that the thinnest point of the oil film on the rotating shaft is S, and the angle between point S and the horizontal position is β. At this time, O b O js O j0 If three points are collinear, then

[0054]

[0055] In the formula, A x and A yThe vortex amplitudes in the x and y directions are Ф respectively. x and Ф y These are the initial phases in the x and y directions, respectively.

[0056] With point S as the initial position along the circumference, the angle between any point P on the surface of the rotating shaft and point S is α. At time t, the position of point P(x,y) consists of three parts: the static equilibrium position, the eddy current of the rotating shaft, and its own rotation.

[0057]

[0058] In the formula, e0 is the static eccentricity, ω is the vortex angular velocity, and R j The radius of the pivot is denoted as .

[0059] With the center of the tile O b With the center of the rotating shaft O j Establish a ξ-η coordinate system with the line connecting the axes. At time t, the dynamic eccentricity of the shaft can be expressed as:

[0060]

[0061] In the formula, e is the dynamic eccentricity, and C b θ represents the radius gap. j Center O of the rotating shaft j Angle with the horizontal position:

[0062]

[0063] in,

[0064] After one revolution of the shaft, the average oil film thickness at point P is: In the formula, N is the number of time nodes within one vortex cycle.

[0065] Step S2: Determine the relationship parameters between the lubricating oil inlet temperature and the journal temperature difference based on the preset shaft surface temperature distribution model; that is, solve the shaft surface temperature distribution and calculate the influence of the lubricating oil inlet temperature on the journal temperature difference.

[0066] In a specific embodiment, the temperature distribution model of the rotating shaft surface includes:

[0067]

[0068]

[0069]

[0070] Where ρ and c are the oil density and specific heat within the micro-gap, respectively, and T is the oil film temperature. b and T j Here, τ represents the temperature of the bearing pad and the shaft, respectively; τ is the viscous shear force; μ is the oil viscosity; and H is the convective heat transfer coefficient between the oil film and the shaft / bearing pad. T represents the temperature difference between the oil film and the ambient temperature. e Let T0 be the ambient temperature, T0 be the oil inlet temperature, and ΔT be the oil film temperature rise. Understandably, as shown in Figure 3, when the oil film within the tiny gap is in steady-state operation, the law of conservation of energy states:

[0071]

[0072] Rewriting the above equation in differential form:

[0073]

[0074] In the formula, ρ and c are the oil density and specific heat within the micro-gap, respectively, and T is the oil film temperature. b and T j Here, τ represents the temperature of the bearing pads and the shaft, respectively; τ is the viscous shear force; and μ is the oil viscosity. H is the convective heat transfer coefficient between the oil film and the shaft and bearing pads.

[0075]

[0076] Let dx = R j Substituting dα into the energy equation, we obtain the oil film temperature distribution equation:

[0077]

[0078] Neglecting heat conduction time, the temperature distribution on the shaft surface can be approximated as equal to the oil film temperature distribution. Assume the bearing temperature T... b It is a constant, equal to the ambient temperature T. e This yields the one-dimensional heat balance equation for solving the oil film temperature distribution:

[0079]

[0080] In the formula, This indicates the temperature difference between the oil film temperature and the ambient temperature.

[0081] From the above, we can see that the oil film temperature rise is: In the formula, T0 is the oil inlet temperature.

[0082] In this embodiment, solving the above equation yields the oil film temperature distribution, i.e., the shaft surface temperature distribution. By taking the average temperature at different times at the same point during one revolution of the shaft as the shaft surface temperature at that point, the relationship between the journal temperature difference and the lubricating oil inlet temperature for the Arabella-type nuclear power turbine generator set can be obtained, as shown in Figure 4. The specific parameters for determining the relationship between the lubricating oil inlet temperature and the journal temperature difference include: taking the average temperature at different times at the same point during one revolution of the shaft as the shaft surface temperature at that point, as shown in the following formula:

[0083]

[0084] in, ω is the average temperature, N is the whirl angular velocity, T is the number of time points in one whirl cycle, and T is the oil film temperature.

[0085] Based on the calculation results of the two steps, with the aim of reducing the circumferential temperature difference of the rotor, the target adjustment value of the lubricating oil temperature can be determined. Taking into account the risk analysis of lubricating oil temperature regulation by related disciplines such as operation, mechanics, and instrumentation, a specific adjustment method can be formulated.

[0086] Step S3: Determine the relationship between journal temperature difference and lubricating oil inlet temperature based on the thickness model and the relationship parameters between lubricating oil inlet temperature and journal temperature difference, and solve for the slope of the curve. That is, the relationship between journal temperature difference and lubricating oil inlet temperature can be obtained through the calculation results of the above two steps, and the slope of the curve can be solved.

[0087] Step S4: Within the preset lubricating oil temperature adjustment range, the optimal lubricating oil temperature adjustment target value is determined when the slope of change within the range is less than the preset threshold. That is, the lubricating oil temperature adjustment range of the Arabella-type steam turbine generator set is 44℃~46℃, and the optimal lubricating oil temperature adjustment target value is when the slope of change within the range is less than 0.05.

[0088] Step S5: Within the preset lubricating oil temperature adjustment range, repeatedly adjust the opening and set value of the lubricating oil temperature regulating valve, continuously observing the unit's operating parameters until the lubricating oil temperature reaches the optimal target value. That is, adjust the opening and set value of the lubricating oil temperature regulating valve, and after adjusting the temperature, continuously observe the changes in unit vibration, bearing temperature, lubricating oil cooler outlet temperature, and main oil tank temperature for 24 hours. Because lubricating oil temperature adjustment affects the cooling and lubrication performance of the bearing's black surface, the adjustment range of the lubricating oil temperature for the Arabella-type steam turbine generator set should not be too large each time, with an upper limit of ±2℃. Repeat the above operation until the lubricating oil temperature reaches the optimal target value.

[0089] In this embodiment, the unit's operating parameters include at least the unit's vibration after temperature adjustment, bearing temperature, lubricating oil cooler outlet temperature, and main oil tank oil temperature change.

[0090] In a specific embodiment, after mathematical modeling and analysis through the above steps, Unit 1 of a nuclear power plant calculated the relationship between the journal temperature difference and the lubricating oil inlet temperature within the allowable operating range of the lubricating oil inlet temperature. The calculation results are shown in Figure 3. Then, based on the allowable range of the lubricating oil, the adjustment target value was set at 47℃. The lubricating oil temperature was adjusted at 1℃ / time starting from the operating oil temperature of 43℃. The results after adjustment are shown in Table 1. The obtained results are consistent with the theoretical calculation results, and the periodic fluctuation phenomenon of the shaft system is weakened after the lubricating oil temperature increases.

[0091] Table 1. Periodic fluctuations of the turbine generator shaft system at Unit 1 of a nuclear power plant under different lubricating oil temperatures.

[0092]

[0093] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0094] The method for suppressing periodic vibration fluctuations in the shaft system of nuclear power units provided by this invention offers an effective way to alleviate the problem of periodic vibration fluctuations in the turbine generator shaft system during operation, especially when the periodic fluctuations in the turbine generator shaft system have been difficult to eradicate for a long time. The method has shown significant results in field applications and has improved the operational stability of the equipment.

[0095] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for suppressing periodic fluctuations in the shaft system of a nuclear power unit, characterized in that, include: The process involves acquiring installation and operating parameters of the unit exhibiting periodic fluctuations, and using these parameters as boundary conditions to determine a thickness model. This thickness model is used to determine the average oil film thickness during shaft whirl within a small gap. A pre-defined shaft surface temperature distribution model is used to determine the relationship parameters between the lubricating oil inlet temperature and the journal temperature difference. Based on the thickness model and the relationship parameters between the lubricating oil inlet temperature and the journal temperature difference, the variation relationship between the journal temperature difference and the lubricating oil inlet temperature is determined, and the slope of the curve is calculated. Within a pre-defined lubricating oil temperature adjustment range, the optimal lubricating oil temperature adjustment target value is determined when the slope within the range is less than a pre-defined threshold. Within the pre-defined unit lubricating oil temperature adjustment range, the opening and set value of the lubricating oil temperature regulating valve are repeatedly adjusted according to the pre-defined adjustment range, and the unit's operating parameters are continuously observed until the lubricating oil temperature reaches the optimal lubricating oil temperature adjustment target value. Specifically, the thickness model includes: Where h is the oil film thickness at point P, S is the thinnest point of the oil film on the rotating shaft, β is the angle between point S and the horizontal position, and point S is the initial position in the circumferential direction. The angle between any point P on the rotating shaft surface and point S is α. x and A y The vortex amplitudes in the x and y directions are Ф respectively. x and Ф y Let e0 be the initial phase in the x and y directions, e0 be the static eccentricity, ω be the vortex angular velocity, and R be the initial phase in the x and y directions, respectively. j Let C be the radius of the rotating shaft, e be the dynamic eccentricity, and C be the radius of the rotating shaft. b For the radius gap, θ j Center O of the rotating shaft j The angle with the horizontal position; the thickness model also includes: in, Let be the average oil film thickness at point P, N be the number of time nodes within one eddy cycle, h be the oil film thickness at point P, ω be the eddy angular velocity, t be the time, and i be the number of time nodes within N; the shaft surface temperature distribution model includes: Where ρ and c are the oil density and specific heat within the micro-gap, respectively, and T is the oil film temperature. b and T j Here, μ represents the temperature of the bearing pad and the shaft, respectively; μ is the oil viscosity; and H is the convective heat transfer coefficient between the oil film and the shaft / bearing pad. T represents the temperature difference between the oil film and the ambient temperature. e T0 is the ambient temperature, and T1 is the oil inlet temperature. The oil film temperature rise; the parameters for determining the relationship between the lubricating oil inlet temperature and the journal temperature difference specifically include: taking the average temperature at the same point at different times during one revolution of the shaft as the shaft surface temperature at that point, as shown in the following formula: in, ω is the average temperature, N is the whirl angular velocity, T is the number of time points in one whirl cycle, and T is the oil film temperature.

2. The method as described in claim 1, characterized in that, The preset lubricating oil temperature adjustment range is 44℃~46℃.

3. The method as described in claim 1, characterized in that, The slope of change within the range of change being less than a preset threshold means that the slope of change within the range of change is less than 0.

05.

4. The method as described in claim 1, characterized in that, The lubricating oil temperature is adjusted in increments of ±2℃.

5. The method as described in claim 1, characterized in that, The unit's operating parameters include at least the unit's vibration after temperature adjustment, bearing temperature, lubricating oil cooler outlet temperature, and main oil tank oil temperature change.

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