Shafting wet mode numerical simulation method for impact type water-turbine generator set

Abstract

The invention relates to the technical field of impact type water-turbine generator sets, in particular to an impact type water-turbine generator set shafting wet mode numerical simulation method, which comprises the following steps of: establishing a full-flow-channel impact type water turbine fluid analysis model, and defining reasonable pretreatment setting; solving by using a transient analysis method to obtain a time domain distribution rule of a water body near the runner bucket; utilizing simulation data to determine shafting wet mode calculation feature points of the impact type water-turbine generator set; converting the water body units of the wet modal calculation feature points into a wet modal analysis model; combining the obtained water body unit and the unit main body structure, and establishing a complete shafting wet modal analysis model of the impact type water-turbine generator set; defining a proper constraint form of the unit and the water body and a fluid-solid coupling relationship between the unit and the water body; and solving and extracting a wet modal analysis result of the shaft system of the impact type water-turbine generator set to obtain the stability characteristic parameters of the shaft system. According to the method, the shafting stability characteristic parameters of the impact type water-turbine generator set considering the influence of the water body can be obtained by utilizing a numerical simulation method according to the wet surface distribution rule of the runner bucket, and the problems that a wet modal numerical simulation method of the impact type water-turbine generator set is imperfect and low in precision are solved.

Description

Technical Field

[0001] The invention relates to the technical field of impulse turbine generator sets, and in particular to a wet mode numerical simulation method for a shaft system of an impulse turbine generator set. Background Art

[0002] The unit shaft stability is one of the important performance indicators of the impulse turbine generator set. This indicator is affected by many factors such as unit size, moment of inertia, mass, stiffness and runner water body. If the parameter design is unreasonable, the unit vibration will exceed the standard and even there will be a resonance risk. In order to ensure the safe and stable operation of the unit and prevent the unit vibration problem caused by unreasonable shaft stability design, it is necessary to perform numerical simulation on the shaft system of the impulse turbine generator set, extract the critical speed and first-order torsional natural frequency of the shaft system, and maintain a certain vibration margin with the runaway speed and excitation frequency respectively. The existing calculation of the shaft stability of the impulse turbine generator set usually adopts the equivalent water density method to simulate the influence of the water body around the runner on the shaft stability. This simplified numerical simulation method leads to large deviations in the calculated values ​​of the characteristic parameters of the shaft stability, increased vibration risks caused by insufficient vibration margin, and is not conducive to the optimal design of the unit. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a wet modal numerical simulation method for the shaft system of an impulse turbine generator set, which can realize the wet modal numerical simulation of the shaft system of the impulse turbine generator set by utilizing the fluid-solid coupling analysis method according to the actual coupling state between the unit and the water body when generating electricity, thereby solving the problems of imperfect calculation method for the stability of the shaft system of the impulse unit and low calculation accuracy.

[0004] The present invention is achieved by adopting the following technical solutions:

[0005] A method for numerically simulating wet modes of a shaft system of an impulse turbine generator set comprises the following steps:

[0006] Step S1, establishing a full-flow channel Pelton turbine fluid analysis model and defining reasonable pre-processing settings;

[0007] Step S2: according to step S1, using the transient analysis method to obtain the time domain distribution law of the water body near the runner bucket;

[0008] Step S3, using the simulation data of step S2, determining the wet modal calculation characteristic points of the shaft system of the impulse turbine generator set;

[0009] Step S4, converting the water unit of the wet modal calculation feature point in step S3 into a wet modal analysis model;

[0010] Step S5, combining the water unit and the main structure of the unit obtained in step S4 to establish a complete wet modal analysis model of the shaft system of the impulse turbine generator set;

[0011] Step S6, defining appropriate constraint forms of the unit and the water body, and the fluid-solid coupling relationship between the unit and the water body;

[0012] Step S7, solving and extracting the wet modal analysis results of the shaft system of the impulse turbine generator set according to step S6, and obtaining the shaft system stability characteristic parameters.

[0013] In the step S1, before performing wet modal calculation of the shaft system of the impulse turbine generator set, a fluid analysis of the impulse turbine of the entire flow channel is performed, a fluid analysis model including the shunt pipe, nozzle, and bucket area is established, and pre-processing settings including model inlet conditions and outlet conditions are defined.

[0014] In step S2, according to step S1, a transient analysis method is used to solve and obtain the time domain distribution law of the water body near the runner bucket. The distribution law is time-varying and periodic, and the wetting surface of the bucket changes periodically with time.

[0015] In step S3, the simulation data of step S2 is used to determine the wet modal calculation characteristic points of the shaft system of the impulse turbine generator set. The bucket wet surface states of different wet modal calculation characteristic points are different and can represent typical states.

[0016] In the step S4, the water body units of the wet modal calculation feature points in step S3 are converted to the wet modal analysis model, and during the conversion, discrete water body units are suppressed from participating in the conversion according to the continuity of unit distribution.

[0017] In step S5, a complete wet modal analysis model of the shaft system of the impulse turbine generator set is established in combination with the water unit obtained in step S4 and the main structure of the unit. The shaft system model includes the main shaft of the unit, the generator rotor, and the turbine runner. The water body model includes a continuous water body near the wetted surface of the bucket when the unit is running.

[0018] In the step S6, appropriate constraint forms and coupling relationships are defined, including the stiffness of the unit bearing support position, the surface constraint of the water body model, and the fluid-solid coupling surface between the runner and the water body.

[0019] In step S7, the wet modal analysis results of the shaft system of the impulse turbine generator set are solved and extracted according to step S6 to obtain the shaft system stability characteristic parameters, including the shaft system critical speed n0 and the shaft system first-order torsional natural frequency f0.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention realizes the wet modal numerical simulation of the shaft system of the impulse turbine generator set by using fluid-solid coupling calculation according to the time domain distribution law of the water body near the runner when the unit is generating electricity. This method innovatively fills the gap of the imperfect calculation method of the shaft system stability of the impulse turbine generator set.

[0022] 2. Before performing wet modal calculation of the shaft system of the hydro-generator set, the present invention first performs full-flow impulse turbine fluid analysis to obtain the time domain distribution law of the water body near the runner when the unit is generating electricity, and then establishes a fluid-solid coupling numerical simulation model. The model is consistent with the operation of the unit and can ensure the accuracy of the calculation.

[0023] 3. The present invention proposes the concept of characteristic points for numerical simulation of shaft wet modes. Each characteristic point can represent a typical water bucket wet surface state. The influence of water body range and thickness is taken into account in the simulation. The calculation result of the unit vibration margin is more accurate and can better ensure the safe and stable operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the numerical simulation method for the wet mode of the shaft system of a pulse turbine generator set. DETAILED DESCRIPTION

[0025] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present application.

[0026] The numerical simulation method of wet mode of the shaft system of impulse turbine generator set is as follows: Figure 1 As shown, the first specific implementation mode includes the following steps:

[0027] Step S1, establishing a full-flow channel Pelton turbine fluid analysis model and defining reasonable pre-processing settings;

[0028] Step S2: according to step S1, using the transient analysis method to obtain the time domain distribution law of the water body near the runner bucket;

[0029] Step S3, using the simulation data of step S2, determining the wet modal calculation characteristic points of the shaft system of the impulse turbine generator set;

[0030] Step S4, converting the water unit of the wet modal calculation feature point in step S3 into a wet modal analysis model;

[0031] Step S5, combining the water unit and the main structure of the unit obtained in step S4 to establish a complete wet modal analysis model of the shaft system of the impulse turbine generator set;

[0032] Step S6, defining appropriate constraint forms of the unit and the water body, and the fluid-solid coupling relationship between the unit and the water body;

[0033] Step S7, solving and extracting the wet modal analysis results of the shaft system of the impulse turbine generator set according to step S6, and obtaining the shaft system stability characteristic parameters.

[0034] In this embodiment, a wet modal numerical simulation method for the shaft system of an impulse turbine generator set is proposed. The wet modal numerical simulation of the shaft system of an impulse turbine generator set can be realized based on the time domain distribution law of the water body around the impeller when the unit is generating electricity, using a fluid-solid coupling calculation method, thereby solving the problem of imperfect calculation method for the stability of the impulse unit shaft system and low calculation accuracy.

[0035] Specific implementation method 2: Figure 1 As shown, this embodiment further limits S1 belonging to the specific embodiment one. In this embodiment, in the step S1, before performing the wet modal calculation of the shaft system of the impulse turbine generator set, the impulse turbine fluid analysis of the entire flow channel is first performed, a fluid analysis model including the diverter pipe, nozzle, and bucket area is established, and the pre-processing settings including the model inlet conditions and outlet conditions are defined.

[0036] In this implementation, a fluid-solid coupling calculation model is established based on the time domain distribution law of the water body near the runner when the unit is generating electricity. The model is closer to the actual working state and can improve the accuracy of numerical simulation.

[0037] Specific implementation method three: Figure 1 As shown, this embodiment further limits S2 belonging to the specific embodiment one. In this embodiment, in the step S2, according to step S1, the transient analysis method is used to solve and obtain the time domain distribution law of the water body near the impeller bucket. The distribution law is time-varying and periodic, and the wetting surface of the bucket changes periodically with time.

[0038] In this embodiment, the coverage of the wetted surface of the runner bucket, the continuity of the water body, and the influence of the thickness of the water body are considered to improve the accuracy of the wet mode numerical simulation.

[0039] Specific implementation method four: Figure 1 As shown, this embodiment further limits S3 belonging to the specific embodiment one. In this embodiment, in step S3, the simulation data of step S2 is used to determine the wet mode calculation characteristic points of the shaft system of the impulse turbine generator set. The wetting surface states of the buckets of different wet mode calculation characteristic points are different and can represent typical states.

[0040] In this implementation, the concept of wet mode numerical simulation characteristic points is proposed. Each characteristic point can represent a typical water bucket wet surface state. The influence of water body range and thickness is taken into account in the simulation. The calculation result of the unit vibration margin is more accurate and can better ensure the safe and stable operation of the unit.

[0041] Specific implementation method five: Figure 1 As shown, this embodiment further limits S4 belonging to the specific embodiment one. In this embodiment, in step S4, the water body unit of the wet modal calculation feature point in step S3 is converted to the wet modal analysis model. During the conversion, the discrete water body units are suppressed from participating in the conversion according to the continuity of the unit distribution.

[0042] In this embodiment, the water body unit is obtained through fluid calculation, and a judgment is made based on whether the water body meets the continuity requirement, which can more accurately evaluate the impact of the water body on the stability of the impulse unit shaft system.

[0043] Specific implementation method six: Figure 1 As shown, this embodiment further limits S5 belonging to the specific embodiment one. In this embodiment, in the step S5, a complete wet modal analysis model of the shaft system of the impulse turbine generator set is established in combination with the water unit obtained in step S4 and the main structure of the unit. The shaft system model includes the unit main shaft, the generator rotor, and the turbine runner. The water body model includes a continuous water body near the wet surface of the bucket when the unit is running.

[0044] In this embodiment, the water body unit is combined with the unit structure unit to form a fluid-solid coupling analysis model, which can significantly improve the simulation accuracy of the influence of the surrounding water body on the stability of the impulse unit shaft system.

[0045] Specific implementation method seven: Figure 1 As shown, this embodiment further limits S6 of the specific embodiment 1. In this embodiment, in step S6, appropriate constraint forms and coupling relationships are defined, including the stiffness of the unit bearing support position, the surface constraints of the water body model, and the fluid-solid coupling surface between the impeller and the water body.

[0046] In this implementation, the actual state of the unit and the experience in simulation calculation are combined to define the solution pre-processing settings to provide basic conditions for carrying out numerical simulation of the shaft system stability of the impulse unit.

[0047] Specific implementation method eight: Figure 1 As shown, this embodiment further limits S7 belonging to the specific embodiment one. In this embodiment, in step S7, the wet modal analysis result of the shaft system of the impulse turbine generator set is solved and extracted according to step S6 to obtain the shaft system stability characteristic parameters, including the shaft system critical speed n0 and the shaft system first-order torsional natural frequency f0.

[0048] In this implementation, it is clarified that the shaft system stability of the impulse unit focuses on the critical speed of the shaft system and the natural frequency of the first-order torsional vibration mode, and the wet mode calculation results and the excitation frequency are compared to lay the foundation for the optimization design of the shaft system stability of the impulse unit.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, it should be clear to those skilled in the art that the technical solutions described in the above embodiments may be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for numerically simulating wet modes of a shaft system of a pulse turbine generator set, comprising the following steps: Step S1, establishing a full-flow channel Pelton turbine fluid analysis model and defining reasonable pre-processing settings; Step S2: according to step S1, using the transient analysis method to obtain the time domain distribution law of the water body near the runner bucket; Step S3, using the simulation data of step S2, determining the wet modal calculation characteristic points of the shaft system of the impulse turbine generator set; Step S4, converting the water unit of the wet modal calculation feature point in step S3 into a wet modal analysis model; Step S5, combining the water unit and the main structure of the unit obtained in step S4 to establish a complete wet modal analysis model of the shaft system of the impulse turbine generator set; Step S6, defining appropriate constraint forms of the unit and the water body, and the fluid-solid coupling relationship between the unit and the water body; Step S7, solving and extracting the wet modal analysis results of the shaft system of the impulse turbine generator set according to step S6, and obtaining the shaft system stability characteristic parameters.

2. The wet modal numerical simulation method for the shaft system of a Pelton turbine generator set according to claim 1 is characterized in that: In the step S1, before performing wet modal calculation of the shaft system of the impulse turbine generator set, a fluid analysis of the impulse turbine of the entire flow channel is performed, a fluid analysis model including the shunt pipe, nozzle, and bucket area is established, and pre-processing settings including model inlet conditions and outlet conditions are defined.

3. The wet modal numerical simulation method for the shaft system of a Pelton turbine generator set according to claim 2 is characterized in that: In step S2, according to step S1, a transient analysis method is used to solve and obtain the time domain distribution law of the water body near the runner bucket. The distribution law is time-varying and periodic, and the wetting surface of the bucket changes periodically with time.

4. A method for numerical simulation of wet modal state of shaft system of impulse turbine generator set according to claim 3, characterized in that: In step S3, the simulation data of step S2 is used to determine the wet modal calculation characteristic points of the shaft system of the impulse turbine generator set. The bucket wet surface states of different wet modal calculation characteristic points are different and can represent typical states.

5. A method for numerical simulation of wet modal state of shaft system of impulse turbine generator set according to claim 4, characterized in that: In the step S4, the water body units of the wet modal calculation feature points in step S3 are converted to the wet modal analysis model, and during the conversion, discrete water body units are suppressed from participating in the conversion according to the continuity of unit distribution.

6. A method for numerical simulation of wet modal state of shaft system of impulse turbine generator set according to claim 5, characterized in that: In step S5, a complete wet modal analysis model of the shaft system of the impulse turbine generator set is established in combination with the water unit obtained in step S4 and the main structure of the unit. The shaft system model includes the main shaft of the unit, the generator rotor, and the turbine runner. The water body model includes a continuous water body near the wetted surface of the bucket when the unit is running.

7. A method for numerical simulation of wet modal state of shaft system of impulse turbine generator set according to claim 6, characterized in that: In the step S6, appropriate constraint forms and coupling relationships are defined, including the stiffness of the unit bearing support position, the surface constraint of the water body model, and the fluid-solid coupling surface between the runner and the water body.

8. A method for numerical simulation of wet modal state of shaft system of impulse turbine generator set according to claim 7, characterized in that: In step S7, the wet modal analysis results of the shaft system of the impulse turbine generator set are solved and extracted according to step S6 to obtain the shaft system stability characteristic parameters, including the shaft system critical speed n0 and the shaft system first-order torsional natural frequency f0.

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