Accurate calculation method for basic load of gas turbine

Abstract

The invention relates to the field of gas turbines, in particular to an accurate calculation method for basic load of a gas turbine, which comprises the following steps of: constructing a gas turbine rotor one-dimensional beam element finite element model, a gas turbine cylinder one-dimensional beam element model, and a three-dimensional entity finite element model of a gas turbine support, a chassis and a cushion box; importing and combining into a basic load calculation model of the gas turbine; calculating load elements of the basic load calculation model, combining the load elements of the basic load of the gas turbine to obtain a basic working condition load of the basic load of the gas turbine, loading the basic working condition load to the basic load calculation model, and solving basic loads under different working conditions; and combining the basic loads under different working conditions, and calculating the long-term basic load and the short-term basic load of the gas turbine. According to the method, the basic load with an accurate position and an accurate numerical value can be extracted through the finite element model, a new method is provided for gas turbine basic load calculation, and the method has a wide engineering application prospect.

Description

Technical Field

[0001] The invention relates to the field of gas turbines, and in particular to an accurate calculation method for a gas turbine base load. Background Art

[0002] A gas turbine is a high-speed rotating impeller heat engine, mainly composed of three major parts: a compressor, a combustion chamber, and a turbine. The compressor draws air from the atmosphere, which is compressed step by step by the axial compressor. The temperature and pressure increase step by step. The compressed air is sent into the turbine to mix with the fuel gas and burn to generate high-temperature gas, which then flows into the turbine to expand and do work. The hot end of the gas turbine cylinder support generally adopts a flexible support to facilitate the free thermal expansion of the hot end cylinder.

[0003] In order to improve the convenience of transportation, installation and maintenance, the integration requirements of gas turbines are getting higher and higher. Most of them are integrated in the form of skid-mounted gas turbines, that is, the gas turbine body, pipelines, instrumentation and control systems and other equipment are installed on a chassis, so as to achieve the purpose of small footprint and easy installation and relocation. For gas turbines that are skid-mounted, their cylinders are connected to the chassis through a supporting structure, and the chassis is connected to the concrete foundation through anchor bolts and embedded parts. During operation, the gas turbine is subjected to multiple loads such as gravity, temperature, pipeline force and torque, airflow force and torque, and disturbance force. These forces are transmitted to the chassis through structures such as cylinders and bearing seats, and finally act on the anchor bolts and embedded parts. The force and torque transmitted through the anchor bolts and embedded parts are the basic loads.

[0004] As mentioned above, when the gas turbine is in operation, there are many types of forces, the force forms are complex, and the structural forms at the force application points are different. The final basic load distribution is also very complex. Traditional basic load calculations usually treat the unit and the supporting structure as a rigid whole, and use one-dimensional mechanical analysis methods to deal with the effects of gravity, pipeline forces and moments, and airflow forces and moments on the basic load. This treatment method ignores the elastic characteristics of structures such as the gas turbine cylinder and support, and the load application point cannot be accurately modeled, resulting in a large deviation between the calculation results and the actual situation. The calculation is simple but lacks accuracy.

[0005] For example, the Chinese patent with the authorization announcement number CN106547982B discloses a method and device for calculating the load of a compressor unit. The invention can realize the calculation of the basic load of the compressor unit, and the basic load value on each anchor bolt can be obtained by distributing the basic load. The patent uses a one-dimensional method to calculate the foundation of the compressor unit, and the dynamic load is calculated using an empirical formula. The basic load distribution is not detailed, and it is difficult to meet the basic load calculation accuracy requirements of the complex structure of the gas turbine. Therefore, there is an urgent need for an accurate calculation method for the basic load of a gas turbine. Summary of the invention

[0006] In order to overcome the problems existing in the prior art, the present invention aims to provide a method for accurately calculating the base load of a gas turbine.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for accurately calculating the basic load of a gas turbine, comprising the following steps:

[0008] S1: Obtain a three-dimensional model of the gas turbine rotor, divide it into sections according to the structural characteristics of the rotor, calculate the bending stiffness, mass and moment of inertia of each section, and establish a one-dimensional beam unit finite element model of the gas turbine rotor according to the equivalent principle of the above parameters;

[0009] S2: Obtain a three-dimensional model of the gas turbine cylinder, divide the cylinder into sections according to the structural characteristics of the cylinder, calculate the mass, inner diameter and outer diameter of each section, and establish a one-dimensional beam unit model of the gas turbine cylinder;

[0010] S3: Obtain the three-dimensional model of the gas turbine support, chassis and cushion box, and create a three-dimensional finite element model using solid elements;

[0011] S4: importing the one-dimensional beam unit finite element model of the gas turbine rotor, the one-dimensional beam unit model of the gas turbine cylinder, and the three-dimensional solid finite element models of the gas turbine support, chassis and cushion box obtained in steps S1-S3 into the finite element software ANSYS and merging them into a basic load calculation model of the gas turbine;

[0012] S5: Calculate the load elements of the basic load calculation model, where the load elements include gravity load, pipeline load, temperature load, airflow load and rotor unbalance load;

[0013] S6: combining load elements of the gas turbine basic load to obtain the basic operating condition load of the gas turbine basic load, loading the basic operating condition load to the basic load calculation model, and solving the basic load under different operating conditions;

[0014] S7: Combine the base loads under different operating conditions and calculate the long-term base load and short-term base load of the gas turbine.

[0015] The present invention is further configured as follows: in step S1, the three-dimensional model of the gas turbine rotor includes a compressor wheel and its moving blades, an intermediate shaft and a turbine wheel and its moving blades, the three-dimensional model of the gas turbine rotor is divided into three large sections, namely, a compressor section, an intermediate shaft section and a turbine section, each large section includes a plurality of segments, the length, mass and moment of inertia of each segment are extracted, the mass and moment of inertia of each stage of moving blades are extracted, and a one-dimensional beam unit finite element model of the gas turbine rotor is created. The equivalent taper is used to simulate the sudden change part of the stepped wheel to ensure that the bending stiffness before and after modeling is equal, and the moving blades are modeled with concentrated mass points.

[0016] The present invention is further configured as follows: static analysis is performed on the one-dimensional beam unit finite element model of the rotor to calculate the static deflection curve of the rotor, and static analysis is performed on the three-dimensional model of the gas turbine rotor at the same time, the vertical displacement of the sky and the earth at the same axial position is extracted, the vertical displacement of the sky and the earth is averaged to obtain the deflection curve of the rotor, the static deflection range of the three-dimensional model is preset, and the static deflection curve of the one-dimensional beam unit is controlled to fall within the static deflection range of the three-dimensional model.

[0017] The present invention is further configured as follows: in step S2, the three-dimensional model of the gas turbine cylinder includes an intake cylinder, a compressor cylinder, a combustion cylinder, a turbine and an exhaust cylinder; the three-dimensional model of the gas turbine cylinder is divided into several sections, the length, inner and outer diameters, and mass of each section are extracted, the mass of each stage of stationary blades, holding rings, combustion barrels and other components is extracted, and a one-dimensional beam unit model of the gas turbine cylinder is created.

[0018] In the above model, the cross section of the one-dimensional beam unit is a variable-section circular tube, the horizontal median plane of the cylinder is ignored, and the non-cylinder stationary parts are applied to the model as concentrated mass points.

[0019] The present invention is further configured as follows: static analysis is performed on the finite element model of the one-dimensional beam unit of the gas turbine cylinder, a static deflection curve is calculated, the static deflection curve is compared with the static deflection curve interval of the three-dimensional model of the gas turbine cylinder, and the static deflection curve of the one-dimensional beam unit of the gas turbine cylinder is controlled to fall within the static deflection interval of the three-dimensional model of the gas turbine cylinder.

[0020] The present invention is further configured as follows: in the basic load calculation model described in step S4, the one-dimensional beam unit of the gas turbine cylinder is connected to the cylinder support through a rigid zone, and the support and the chassis are connected using a surface friction contact unit. The one-dimensional beam unit of the gas turbine rotor is connected to the one-dimensional beam unit of the cylinder using a linear spring damper unit, the front bearing seat of the gas turbine is a rigid support, and the linear spring damper unit simulates the bearing stiffness and damping; the rear bearing seat of the gas turbine is a flexible support, and the equivalent dynamic stiffness of the rear bearing seat flexible support and the bearing is calculated.

[0021] The present invention is further configured as follows: the equivalent dynamic stiffness is calculated by the following formula:

[0022]

[0023] In the formula is the equivalent dynamic stiffness of the bearing seat and bearing, is the bearing dynamic stiffness, is the dynamic stiffness of the flexible support, [K s ] is the static stiffness of the flexible support, [M s ] is the mass of the flexible support, ω is the circular frequency of the rotation speed, [C s ] is the flexible support damping, [K b ] is the static stiffness of the bearing, [Cb] is the oil film damping, and i is an imaginary unit.

[0024] The present invention is further configured as follows: Step S5 specifically comprises:

[0025] S51: applying gravity acceleration to the basic load calculation model to calculate the gravity load;

[0026] S52: Calculate pipe loads based on cold and hot pipe forces and moments;

[0027] S53: Extract the average temperature of different sections from the three-dimensional finite element thermal analysis of the gas turbine cylinder, calculate the temperature field of the cylinder based on the flow aerodynamic and secondary air system data, and obtain the temperature load;

[0028] S54: Calculate the stator airflow load and the rotor airflow load based on the stator airflow force and torque and the rotor axial thrust;

[0029] S55: The rotor unbalance load is divided into two types: allowable unbalance and accidental unbalance. According to the rotor dynamic balancing requirements, determine the first, second and third order unbalances of the gas turbine under the unbalance level G = 6.3mm / s, and calculate the allowable unbalance;

[0030] According to the condition of two moving blades of the last stage of gas turbine being broken at the root, the first, second and third order unbalance are calculated, and the accidental unbalance is calculated.

[0031] The present invention is further configured as follows: in step S6, the basic working conditions include static load conditions, dynamic load conditions, disturbance load conditions and accidental load conditions.

[0032] The present invention is further configured as follows: Step S6 specifically comprises:

[0033] S61: Under the static load condition, gravity, cold pipe force and moment are applied to the basic load calculation model to calculate the static basic load force F g and static base load torque M g ;

[0034] S62: Under dynamic load conditions, the temperature field, stator flow force and moment, hot pipeline force and moment, and rotor axial thrust are applied to the gas turbine basic load calculation model to calculate the dynamic basic load force F d Dynamic base torque M d ;

[0035] S63: Under the disturbance load condition, the allowable unbalanced force is applied to the gas turbine basic load calculation model to calculate the disturbance basic load force F u and disturbance force base load torque M u ;

[0036] S64: Under accidental load conditions, apply accidental unbalanced forces to the gas turbine base load calculation model and calculate the accidental base load force F o and the accidental foundation load torque M o .

[0037] The present invention is further configured as follows: the long-term load force F is obtained by combining the following formulas: Li and long-term load torque M Li and short-term load F si and short-term load torque M si ;

[0038] F Li =F gi +F di +|F ui |;

[0039] M Li =M gi +M di +|M ui |;

[0040] F si =F gi +F di +|F ui |+|F oi |;

[0041] M si =M gi +M di +|M ui |+|M oi |;

[0042] Among them, i represents the three directions x, y and z of the Cartesian coordinate system.

[0043] In summary, the beneficial effects of the above technical solution of the present invention are as follows:

[0044] The present invention adopts a reasonable equivalent modeling method to shrink and model the three-dimensional model degrees of freedom of the gas turbine cylinder and rotor into a one-dimensional beam unit, and the support, chassis and cushion box are simulated by three-dimensional solid units. The linear spring damper spring unit simulates the front bearing stiffness and simulates the equivalent dynamic stiffness of the rear bearing and the rear bearing support. The one-dimensional rotor and cylinder beam unit model of the gas turbine are connected, the cylinder and the support are connected through a rigid zone, and the support and the chassis are connected by a surface friction contact unit. The equivalent finite element model greatly reduces the number of grids and speeds up the calculation speed. It can not only perform calculations of static load conditions and dynamic load conditions, but also makes the unbalanced response calculation of complex models including rotors, cylinders, supports, chassis and cushion boxes a reality.

[0045] The finite element model can be used to extract the precise position and accurate value of the base load, which provides a new method for the calculation of the gas turbine base load and technical support for the gas turbine design, and has broad engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0047] Figure 1 Gas turbine base load calculation flow chart;

[0048] Figure 2 One-dimensional beam element model of gas turbine rotor;

[0049] Figure 3 Gas turbine rotor static deflection curve;

[0050] Figure 4 3D model of gas turbine cylinder;

[0051] Figure 5 One-dimensional beam element model of gas turbine cylinder;

[0052] Figure 6 Gas turbine cylinder static deflection curve;

[0053] Figure 7 Gas turbine support, cylinder, and cushion box models;

[0054] Figure 8 Gas turbine bearing stiffness curve;

[0055] Fig. 9 Oil film damping curve;

[0056] Fig.10 Flexible support stiffness curve;

[0057] Fig.11 Equivalent dynamic stiffness of bearing seat and bearing;

[0058] Fig.12 Equivalent dynamic damping of bearing seat and bearing;

[0059] Fig.13 Schematic diagram of gas turbine base load location;

[0060] Fig.14 Long-term load capacity;

[0061] Fig.15 Long-term load moment;

[0062] Fig.16 Short-term load force;

[0063] Fig.17 Short-term load moments. DETAILED DESCRIPTION

[0064] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, other similar embodiments obtained by ordinary technicians in the field without making any creative work should all fall within the scope of protection of the present invention.

[0065] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0066] Example:

[0067] like Figure 1-17 As shown in the figure, a preferred embodiment of the present invention is a method for accurately calculating the basic load of a gas turbine, taking a gas turbine as an example, comprising the following steps:

[0068] S1: Obtain a three-dimensional model of the gas turbine rotor, divide it into sections according to the structural characteristics of the rotor, calculate the bending stiffness, mass and moment of inertia of each section, and establish a one-dimensional beam unit finite element model of the gas turbine rotor according to the equivalent principle of the above parameters;

[0069] The three-dimensional model of the gas turbine rotor includes a compressor wheel and its moving blades, an intermediate shaft and a turbine wheel and its moving blades. The three-dimensional model of the gas turbine rotor is divided into three large sections: a compressor section, an intermediate shaft section and a turbine section. Each large section contains several segments. The length, mass and moment of inertia of each segment are extracted. The mass and moment of inertia of each stage of moving blades are extracted. A one-dimensional beam unit finite element model of the gas turbine rotor is created, such as Figure 2 As shown in the figure, an equivalent taper is used to simulate the sudden change of the stepped impeller to ensure that the bending stiffness before and after modeling is equal, and the moving blade is modeled as a concentrated mass point.

[0070] The static analysis of the rotor one-dimensional beam unit finite element model is performed to calculate the rotor static deflection curve. At the same time, the static analysis of the gas turbine rotor three-dimensional model is performed to extract the vertical displacement of the sky and the earth at the same axial position. The vertical displacement of the sky and the earth is averaged to obtain the rotor deflection curve. The static deflection range of the three-dimensional model is preset, and the static deflection curve of the one-dimensional beam unit is controlled to fall within the static deflection range of the three-dimensional model. Figure 3 shown.

[0071] S2: Figure 4As shown, a three-dimensional model of a gas turbine cylinder is obtained, the cylinder is divided into sections according to the structural characteristics of the cylinder, the mass, inner diameter and outer diameter of each section are calculated, and a one-dimensional beam unit model of the gas turbine cylinder is established;

[0072] The three-dimensional model of the gas turbine cylinder includes an intake cylinder, a compressor cylinder, a combustion cylinder, a turbine and an exhaust cylinder; the three-dimensional model of the gas turbine cylinder is divided into several sections, the length, inner and outer diameters, and mass of each section are extracted, and the mass of each stage of the stator blade, the retaining ring and the combustion cylinder and other components are extracted, and a one-dimensional beam unit model of the gas turbine cylinder is created, such as Figure 5 shown.

[0073] In the above model, the cross section of the one-dimensional beam unit is a variable-section circular tube, the horizontal median plane of the cylinder is ignored, and the non-cylinder stationary parts are applied to the model as concentrated mass points.

[0074] The static analysis of the one-dimensional beam unit finite element model of the gas turbine cylinder is carried out to calculate the static deflection curve, which is compared with the static deflection curve range of the three-dimensional model of the gas turbine cylinder. The static deflection curve of the one-dimensional beam unit of the gas turbine cylinder is controlled to fall within the static deflection range of the three-dimensional model of the gas turbine cylinder, such as Figure 6 shown.

[0075] S3: Obtain the three-dimensional model of the gas turbine support, chassis and cushion box, and create a three-dimensional finite element model using solid elements, such as Figure 7 shown.

[0076] S4: importing the one-dimensional beam unit finite element model of the gas turbine rotor, the one-dimensional beam unit model of the gas turbine cylinder, and the three-dimensional solid finite element models of the gas turbine support, chassis and cushion box obtained in steps S1-S3 into the finite element software ANSYS and merging them into a basic load calculation model of the gas turbine;

[0077] In the basic load calculation model, the one-dimensional beam unit of the gas turbine cylinder is connected to the cylinder support through a rigid zone, and the support and the chassis are connected by a surface friction contact unit. The one-dimensional beam unit of the gas turbine rotor is connected to the one-dimensional beam unit of the cylinder by a linear spring damper unit. The front bearing seat of the gas turbine is a rigid support, and the linear spring damper unit simulates the bearing stiffness and damping; the rear bearing seat of the gas turbine is a flexible support, and the equivalent dynamic stiffness of the rear bearing seat flexible support and the bearing is calculated.

[0078] in, is the equivalent dynamic stiffness of the bearing seat and bearing, is the bearing dynamic stiffness, such as Figure 8 As shown;

[0080] is the dynamic stiffness of the flexible support, [K s ] is the static stiffness of the flexible support, such as Fig.10 As shown, [M s ] is the mass of the flexible support, ω is the circular frequency of the rotation speed, and the damping of the flexible support is ignored [C s ],[K b ] is the static stiffness of the bearing, [C b ] is the oil film damping, i is an imaginary unit; Fig. 9 shown.

[0081] The rear bearing seat of the engine is connected to the cylinder through a support plate, which has poor rigidity. It is necessary to calculate the equivalent stiffness of the support plate and the oil film and import it into the rotor-support dynamics system as a comprehensive support stiffness model for solution.

[0082] The equivalent dynamic stiffness is calculated by the following formula:

[0083]

[0084] Get the equivalent dynamic stiffness like Fig.11 As shown in Fig.12 shown.

[0085] Among them, Kxx is the x-direction (lateral) stiffness, Kyy is the y-direction (vertical) stiffness, Kxy and kyx are cross stiffness, Cxx is the x-direction (lateral) damping, Cyy is the y-direction (vertical) stiffness, and Cxy and Cyx are cross damping.

[0086] S5: Calculate the load elements of the basic load calculation model, where the load elements include gravity load, pipeline load, temperature load, airflow load and rotor unbalance load;

[0087] S51: Gravity load: Gravity load can be obtained by directly applying gravity acceleration in the basic load calculation model;

[0088] S52: Pipeline load: Pipeline load is divided into cold and hot loads. Pipeline calculation software such as CII is used to establish a gas turbine pipeline load model. Gravity and displacement constraints are applied to cold loads, and temperature, pressure and displacement constraints are applied to hot loads. The cold and hot pipeline forces and moments are calculated;

[0089] S53: Temperature load: Temperature load of the engine cylinder. The compressor and turbine pneumatics professionals provide the main channel temperature, density and velocity, and calculate the convection heat transfer coefficient of the main channel according to the empirical formula. The secondary air system provides the convection heat transfer coefficient and temperature of the engine chamber. The three-dimensional finite element model of the engine cylinder is thermally analyzed to obtain the three-dimensional temperature field of the engine cylinder, and the average temperature of the intake cylinder, compressor cylinder, combustion cylinder, turbine cylinder and exhaust cylinder is extracted;

[0090] S54: Airflow load: Airflow load includes thrust load and stator airflow force and moment. The thrust load uses one-dimensional fluid calculation software such as Flowmaster to calculate the fluid flow, pressure and temperature of the gas turbine flow path, and then the chamber force analysis is performed to obtain the rotor thrust. The stator airflow force and moment use fluid calculation software such as CFD to calculate the aerodynamic performance of the compressor and turbine, and the stator airflow force and moment can be extracted from the results.

[0091] S55: The rotor unbalance load is divided into two types: allowable unbalance and accidental unbalance. The allowable unbalance is determined based on the rotor dynamic balancing requirements. The gas turbine unbalance level G = 6.3mm / s is combined with the rotor mass to determine the allowable unbalance, and then the first, second, and third order unbalance is calculated.

[0092] For accidental unbalance, it is assumed that two adjacent moving blades of the last stage of the gas turbine are broken at the root. The eccentricity is calculated using 3D design software such as Solidworks. The accidental unbalance is calculated in combination with the rotor mass, and then the first, second and third order unbalance are calculated.

[0093] S6: combining load elements of the gas turbine basic load to obtain the basic operating condition load of the gas turbine basic load, loading the basic operating condition load to the basic load calculation model, and solving the basic load under different operating conditions;

[0094] The basic working conditions include static load conditions, dynamic load conditions, disturbance load conditions and accidental load conditions.

[0095] S61: Under static load conditions, the finite element software ANSYS is used to assign material data to the foundation load calculation model, apply gravity acceleration, cold pipeline force and moment, and fix the bottom of the channel iron to perform static force solution and extract the static foundation load force F g and static base load torque M g ;

[0096] S62: Under dynamic load conditions, the finite element software ANSYS is used to assign material data to the foundation load calculation model, apply the cylinder temperature field, stator air flow force and moment, rotor thrust, hot pipeline force and moment, and fix the bottom of the slot iron to perform static force solution and extract the dynamic foundation load force F d Dynamic base torque M d ;

[0097] S63: Under the disturbance load condition, the finite element software ANSYS is used, the basic load calculation model is assigned with material data, three load steps are applied, the first load step applies the first-order unbalance, the second load step applies the second-order unbalance, and the third load step applies the third-order unbalance. The damping ratio is given as 0.02, the bottom of the channel iron is fixed, and the harmonic response analysis is performed to extract the disturbance foundation load force F u and disturbance force base load torque Mu ;

[0098] S64: Under accidental load conditions, the finite element software ANSYS is used, the foundation load calculation model is assigned material data, three load steps are applied, the first load step applies the first-order unbalance, the second load step applies the second-order unbalance, and the third load step applies the third-order unbalance. The damping ratio is given as 0.02, the bottom of the channel iron is fixed, and the harmonic response analysis is performed to extract the accidental foundation load force F o and the accidental foundation load torque M o .

[0099] S7: Combine the base loads under different operating conditions and calculate the long-term base load and short-term base load of the gas turbine. The base load position is as follows: Fig.13 The figure shows the contact area between the engine cushion box and the channel iron, which is combined according to the following formula:

[0100] F Li =F gi +F di +|F ui |;

[0101] M Li =M gi +M di +|M ui |;

[0102] F si =F gi +F di +|F ui |+|F oi |;

[0103] M si =M gi +M di +|M ui |+|M oi |;

[0104] Obtain the long-term load force F Li and long-term load torque M Li ,like Figure 14-15 As shown; and short-term load force F si and short-term load torque M si ,like Figure 16-17 As shown; where i represents the three directions x, y and z of the Cartesian coordinate system.

[0105] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for accurately calculating the base load of a gas turbine, characterized in that: The following steps are involved: S1: Obtain the three-dimensional model of the gas turbine rotor, divide it into sections according to the rotor structural characteristics, calculate the bending stiffness, mass and moment of inertia of each section, and establish a one-dimensional beam unit finite element model of the gas turbine rotor according to the equivalent principle; S2: Obtain a three-dimensional model of the gas turbine cylinder, divide the cylinder into sections according to the structural characteristics of the cylinder, calculate the mass, inner diameter and outer diameter of each section, and establish a one-dimensional beam unit model of the gas turbine cylinder according to the equivalent principle; S3: Obtain the three-dimensional model of the gas turbine support, chassis and cushion box, and create a three-dimensional finite element model using solid elements; S4: importing the one-dimensional beam unit finite element model of the gas turbine rotor, the one-dimensional beam unit model of the gas turbine cylinder, and the three-dimensional solid finite element models of the gas turbine support, chassis and cushion box obtained in steps S1-S3 into the finite element software ANSYS and merging them into a basic load calculation model of the gas turbine; S5: Calculate the load elements of the basic load calculation model, where the load elements include gravity load, pipeline load, temperature load, airflow load and rotor unbalance load; S6: combining load elements of the gas turbine basic load to obtain the basic operating condition load of the gas turbine basic load, loading the basic operating condition load to the basic load calculation model, and solving the basic load under different operating conditions; S7: Combine the base loads under different operating conditions and calculate the long-term base load and short-term base load of the gas turbine.

2. The method for accurately calculating the base load of a gas turbine according to claim 1, characterized in that: In step S1, the three-dimensional model of the gas turbine rotor includes a compressor wheel and its moving blades, an intermediate shaft and a turbine wheel and its moving blades. The three-dimensional model of the gas turbine rotor is divided into three large sections: a compressor section, an intermediate shaft section and a turbine section. Each large section includes a plurality of segments. The length, mass and moment of inertia of each segment are extracted. The mass and moment of inertia of each stage of moving blades are extracted, and a one-dimensional beam unit finite element model of the gas turbine rotor is created.

3. The method for accurately calculating the base load of a gas turbine according to claim 2, characterized in that: The static analysis of the rotor one-dimensional beam unit finite element model is carried out to calculate the static deflection curve, which is compared with the static deflection curve range of the gas turbine rotor three-dimensional model to control the static deflection curve of the gas turbine rotor one-dimensional beam unit to fall within the static deflection range of the gas turbine rotor three-dimensional model.

4. The method for accurately calculating the base load of a gas turbine according to claim 1, characterized in that: In step S2, the three-dimensional model of the gas turbine cylinder includes an intake cylinder, a compressor cylinder, a combustion cylinder, a turbine and an exhaust cylinder; the three-dimensional model of the gas turbine cylinder is divided into several sections, the length, inner and outer diameters, and mass of each section are extracted, the mass of each stage of stationary blades, retaining rings and combustion tube components is extracted, and a one-dimensional beam unit model of the gas turbine cylinder is created.

5. A method for accurately calculating the base load of a gas turbine according to claim 4, characterized in that: The static analysis of the one-dimensional beam unit finite element model of the gas turbine cylinder is carried out, and the static deflection curve is calculated. The static deflection curve is compared with the static deflection curve range of the three-dimensional model of the gas turbine cylinder, and the static deflection curve of the one-dimensional beam unit of the gas turbine cylinder is controlled to fall within the static deflection range of the three-dimensional model of the gas turbine cylinder.

6. The method for accurately calculating the base load of a gas turbine according to claim 1, characterized in that: In the basic load calculation model described in step S4, the one-dimensional beam unit of the gas turbine cylinder is connected to the cylinder support through a rigid zone, the support and the chassis are connected by a surface friction contact unit, the one-dimensional beam unit of the gas turbine rotor is connected to the one-dimensional beam unit of the cylinder by a linear spring damper unit, the front bearing seat of the gas turbine is a rigid support, and a linear spring damper unit is used to simulate the bearing stiffness and damping; the rear bearing seat of the gas turbine is a flexible support, and the flexible support of the rear bearing seat is converted into an equivalent dynamic stiffness.

7. A method for accurately calculating the base load of a gas turbine according to claim 6, characterized in that: The equivalent dynamic stiffness is calculated by the following formula: In the formula is the equivalent dynamic stiffness of the rear bearing seat and bearing, is the bearing dynamic stiffness, is the dynamic stiffness of the flexible support, [K s ] is the static stiffness of the flexible support, [M s ] is the mass of the flexible support, ω is the circular frequency of the rotation speed, [C s ] is the flexible support damping, [K b ] is the static stiffness of the bearing, [C b ] is the oil film damping and i is the imaginary unit.

8. The method for accurately calculating the base load of a gas turbine according to claim 1, characterized in that: Step S5 is specifically as follows: S51: applying gravity acceleration to the basic load calculation model to calculate the gravity load; S52: Calculate pipe loads based on cold and hot pipe forces and moments; S53: Extract the average temperature of different sections from the three-dimensional finite element thermal analysis of the gas turbine cylinder, calculate the temperature field of the cylinder based on the flow aerodynamic and secondary air system data, and obtain the temperature load; S54: Calculate the stator airflow load and the rotor airflow load based on the stator airflow force and torque and the rotor axial thrust; S55: The rotor unbalance load is divided into two types: allowable unbalance and accidental unbalance. According to the rotor dynamic balancing requirements, determine the first, second and third order unbalances of the gas turbine under the condition of unbalance grade G = 6.3mm / s, and calculate the allowable unbalance. According to the condition of two moving blades of the last stage of gas turbine being broken at the root, the first, second and third order unbalance are calculated, as well as the accidental unbalance.

9. A method for accurately calculating the base load of a gas turbine according to claim 8, characterized in that: In step S6, the basic working conditions include static load conditions, dynamic load conditions, disturbance load conditions and accidental load conditions; S61: Under the static load condition, gravity, cold pipe force and moment are applied to the basic load calculation model to calculate the static basic load force F g and static base load torque M g ; S62: Under dynamic load conditions, the temperature field, stator flow force and moment, hot pipeline force and moment, and rotor axial thrust are applied to the gas turbine basic load calculation model to calculate the dynamic basic load force F d Dynamic base torque M d ; S63: Under the disturbance load condition, the allowable unbalanced force is applied to the gas turbine basic load calculation model to calculate the disturbance basic load force F u and disturbance force base load torque M u ; S64: Under accidental load conditions, apply accidental unbalanced forces to the gas turbine base load calculation model and calculate the accidental base load force F o and the accidental foundation load torque M o .

10. A method for accurately calculating the base load of a gas turbine according to claim 9, characterized in that: Step S7 specifically includes combining the basic loads under different working conditions in S6 according to the following formula to obtain the long-term load force F Li and long-term load torque M Li and short-term load F si and short-term load torque M si ; F Li =F gi +F di +|F ui |; M Li =M gi +M di +|M ui |; F si =F gi +F di +|F ui |+|F oi |; M si =M gi +M di +|M ui |+|M oi |; Among them, i represents the three directions x, y and z of the Cartesian coordinate system.

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