A method for optimizing aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator

Abstract

The application provides a kind of aerodynamic cooling parameter optimization method of magnetic suspension natural gas pressure difference generator, it is related to natural gas pressure difference power generation equipment technical field, the magnetic suspension natural gas pressure difference generator is designed in the application, wherein the centripetal turbine type impeller structure can efficiently convert natural gas pressure difference energy into mechanical energy. Among them, the fairing adopts a spherical flow line type design and is configured with an annular hole, the shunt gas flow realizes magnetic bearing cooling and magnetic coupling isolation, the multi-gas flow channel design makes the gas flow split and flow, and enhances the heat dissipation effect. At the same time, the application improves the aerodynamic simulation accuracy through adaptive grid technology and multi-scale turbulence model; the heuristic dynamic programming algorithm and utility function are used, and the experience playback method is used to iteratively optimize the control input quantity, i.e. the structure parameter, and the structure parameter in the magnetic suspension natural gas pressure difference generator can be adjusted based on the optimized control input quantity to improve the performance of the magnetic suspension natural gas pressure difference generator.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of natural gas differential pressure power generation equipment, in particular to a method for optimizing aerodynamic cooling parameters of a magnetic suspension natural gas differential pressure generator. BACKGROUND

[0002] The current natural gas differential pressure power generation system generally adopts mechanical bearing to support the rotor, and the physical contact characteristics result in a high friction loss coefficient of 0.05-0.15 (ISO 4378 standard), an energy conversion efficiency loss of 8%-12%, and an oil film stiffness nonlinear characteristic of the mechanical bearing that easily causes subsynchronous vibration, an amplitude amplification coefficient of 5-8 times in the critical speed range, and an annual average maintenance cost accounting for 15%-20% of the total cost of the equipment. Although the magnetic suspension technology can eliminate the friction loss, it faces multiple coupling challenges in the natural gas differential pressure power generation scenario: the gas-solid thermal coupling effect is significant under high pressure difference (>6MPa) working conditions, and the traditional magnetic bearing is difficult to suppress the vortex instability (amplitude >50μm) caused by flow field pulsation, and the mutual restriction of magnetic pole layout and cooling flow channel design results in insufficient heat dissipation power density (<200W / cm²), and the magnetic saturation effect is intensified when the coil temperature rises by more than 80K, which restricts the long-term stability of the system.

[0003] With the wide application of natural gas energy, the natural gas differential pressure power generation technology has attracted much attention due to its ability to effectively utilize the pressure difference energy in the gas pipeline. The traditional natural gas differential pressure generator usually adopts a mechanical bearing to support the rotor structure, which has problems such as large friction loss, high maintenance cost, and short service life. At the same time, most of the existing equipment is of a split structure of generator and expander, which has deficiencies in aerodynamic cooling and collaborative optimization, resulting in difficulty in effectively controlling the temperature rise of the stator winding and the stator in high temperature environment, which affects the stability of equipment operation and power generation efficiency.

[0004] In terms of aerodynamic design, the conventional CFD (Computational Fluid Dynamics) simulation method usually adopts boundary layer mesh and physical field controlled mesh division, which is difficult to achieve high precision simulation for high-speed complex airflow area and complex boundary, resulting in large deviation of pressure drop prediction. At the same time, the existing single turbulence model cannot accurately describe the large-scale turbulence and the separation characteristics of the near-wall boundary layer, which limits the optimization space of aerodynamic performance. In terms of cooling structure design, the traditional scheme mostly uses external cooling system or independent heat dissipation system, which not only increases the structural complexity, but also affects the energy utilization efficiency of natural gas. SUMMARY

[0005] In view of the problems of high structural complexity and affecting the energy utilization efficiency of natural gas, the purpose of the present application is to provide a method for optimizing aerodynamic cooling parameters of a magnetic suspension natural gas differential pressure generator, comprising:

[0006] Step 1: Construct a three-dimensional model of the magnetic levitation natural gas pressure differential generator, wherein the magnetic levitation natural gas pressure differential generator includes an impeller, a stator, a magnetic levitation bearing mechanism, a fairing, a tubular casing, and a multi-gas flow channel, and the magnetic levitation natural gas pressure differential generator is from the outside to the inside, respectively, the tubular casing, the fairing, and the magnetic levitation bearing mechanism, the tubular casing includes an inlet casing, a pressure-bearing casing, and an outlet casing, the inlet casing and the pressure-bearing casing are fixed by rivets, and the pressure-bearing casing and the outlet casing are fixed by rivets;

[0007] The magnetic levitation bearing mechanism includes a rotor shaft and two bearing sub-mechanisms, and a stator is arranged between the two bearing sub-mechanisms, the stator is an annular permanent magnet, adopts a deep slot design, and is fixed in the pressure-bearing casing by inlaying;

[0008] The two bearing sub-mechanisms are externally provided with a fairing, the fairing is an axially protruding spherical streamlined structure, a plurality of circular holes are annularly arranged at the axial center point of the fairing, and the fairing is fixed in the pressure-bearing casing by rivets;

[0009] The impeller is a centripetal turbine structure, the impeller is fixed with the rotor shaft by embedding, and the impeller is located in the outlet casing, and the outlet casing adopts a gradually narrowing design at the impeller inlet in the direction from the pressure-bearing casing to the outlet casing;

[0010] The multi-gas flow channel includes an inner flow channel and an outer flow channel, the inner flow channel is a flow channel passing through the circular holes of the fairing and the region where the magnetic levitation bearing mechanism is located, and the outer flow channel is a flow channel in the region where the fairing is located inside the tubular casing;

[0011] Step 2: Based on the three-dimensional model, CFD simulation is performed on the process of natural gas passing through the magnetic levitation natural gas pressure differential generator to obtain the flow field distribution characteristics and temperature field characteristics of the natural gas flowing in the magnetic levitation natural gas pressure differential generator, and the actual values of the stator electromagnetic performance, the rotor electromagnetic performance, the stator mechanical strength, and the rotor mechanical strength, wherein the flow field distribution characteristics and the temperature field characteristics include the Mach number, the local temperature gradient, the Reynolds number, and the velocity vector variation of the internal region of the magnetic levitation natural gas pressure differential generator;

[0012] Step 3: Based on the Mach number, the local temperature gradient, the Reynolds number, and the velocity vector variation of the internal region of the magnetic levitation natural gas pressure differential generator, a target grid is constructed by using an adaptive grid division technique;

[0013] Step 4: For each grid region in the target grid, a turbulence model is constructed according to the Reynolds number obtained in step 2;

[0014] Step 5: Extract the turbulence model for all grid regions in the target grid to obtain the parameter feature vector. The parameter feature vector includes the temperature rise of the winding, the temperature rise of the stator, and the pressure drop of natural gas through the magnetic levitation natural gas differential pressure generator.

[0015] Step 6: Calculate the utility value based on the temperature rise of the windings, the temperature rise of the stator, and the pressure drop of natural gas through the magnetic levitation natural gas differential pressure generator. Then, calculate the control input based on the utility value and determine whether the utility value is less than or equal to a preset threshold. If the utility value is less than or equal to the preset threshold, use the calculated control input as the optimized control input. The optimized control input is used to adjust the structural parameters in the magnetic levitation natural gas differential pressure generator. If the utility value is greater than the preset threshold, return to step 3.

[0016] Optionally, the bearing sub-mechanism includes an axial magnetic levitation bearing, a radial magnetic levitation bearing, and a protective bearing. The two bearing sub-mechanisms are installed at both ends of the rotor shaft. The two ends of the rotor shaft are respectively fixed inside the pressure housing by bearing seats. The rotor shaft is connected to the bearing sub-mechanism by a shrink sleeve. From the center of the rotor shaft to both ends are the radial magnetic levitation bearing, the axial magnetic levitation bearing, and the protective bearing, respectively. The outer rings of the protective bearing, the axial magnetic levitation bearing, and the radial magnetic levitation bearing are welded and fixed inside the fairing.

[0017] Optionally, step 3 specifically includes:

[0018] For regions within the magnetic levitation natural gas differential pressure generator with Mach numbers greater than or equal to 0.6, a first-size mesh is used; for regions with Mach numbers greater than or equal to 0.3 and less than 0.6, a second-size mesh is used; and for regions with Mach numbers less than 0.3, a third-size mesh is used. The first size is smaller than the second size, and the second size is smaller than the third size. A boundary layer refinement using wall function correction is employed to refine the mesh, resulting in the initial mesh. For regions in the initial mesh with local temperature gradients greater than or equal to 100 K / m, a hexahedral dominant structure mesh is used, with 2 or 3 layers automatically densified at the boundaries, and the maximum local mesh size not exceeding 0.3 mm, thus obtaining the first mesh. For regions in the first mesh with velocity vector changes less than 0.5 m / s, a structured coarse mesh is used to replace the first mesh, resulting in the target mesh.

[0019] Optionally, step 4 specifically includes:

[0020] For each grid region in the target grid, determine whether the Reynolds number in the grid region is greater than or equal to 10. 4 The Reynolds number in the grid region is greater than or equal to 10. 4 In this case, a k-ε turbulence model is constructed in the grid region where the Reynolds number is less than 10.4 In this case, a k-omega turbulent flow model is constructed in the grid region.

[0021] Optionally, the utility value is calculated according to the temperature rise of the winding, the temperature rise of the stator and the pressure drop of the natural gas passing through the magnetic levitation natural gas differential pressure generator in step 6, which is realized by the following formula:

[0022] ;

[0023] wherein, represents the utility value, represents the difference between the temperature rise of the winding at time t and the preset winding temperature rise, represents the difference between the temperature rise of the stator at time t and the preset stator temperature rise, represents the difference between the pressure drop of the natural gas passing through the magnetic levitation natural gas differential pressure generator at time t and the preset pressure drop, represents the deviation of the actual value of the stator electromagnetic performance from the preset target value, represents the deviation of the actual value of the rotor electromagnetic performance from the preset target value, represents the deviation of the actual value of the stator mechanical strength from the preset target value, represents the deviation of the actual value of the rotor mechanical strength from the preset target value, represents the temperature rise weight, represents the pressure drop weight, represents the mechanical weight, represents the electromagnetic weight.

[0024] Optionally, the control input quantity is calculated based on the utility value in step 6, which specifically includes:

[0025] Step A1: defining state quantity , the state quantity is represented as:

[0026] ;

[0027] wherein, represents the deviation of the actual value of the stator mechanical strength from the preset target value, represents the deviation of the actual value of the rotor mechanical strength from the preset target value, represents the difference between the temperature rise of the winding at time t and the preset winding temperature rise, represents the difference between the temperature rise of the stator at time t and the preset stator temperature rise, represents the difference between the pressure drop of the natural gas passing through the magnetic levitation natural gas differential pressure generator at time t and the preset pressure drop;

[0028] Step A2: calculating the control input quantity according to the utility value and the state quantity , combined with the formula of the minimized cost function, the control input quantity is calculated .

[0029] Optionally, the formula of the minimized cost function is represented as:

[0030] ;

[0031] wherein, denotes a discount factor, denotes a cost value at time t, denotes a cost value at time t, denotes a cost value at time t, denotes a time interval.

[0032] The beneficial effects produced by the above technical solutions are:

[0033] The magnetic suspension natural gas differential pressure generator is designed, the centripetal turbine type impeller structure in the magnetic suspension natural gas differential pressure generator can realize the purpose of efficiently converting natural gas differential pressure energy into mechanical energy during the operation of the magnetic suspension differential pressure generator, and the fairing is designed, the fairing is designed in a spherical flow line type and is provided with an annular hole, the split gas flow realizes magnetic bearing cooling and magnetic coupling isolation, the multi-gas flow channel design makes the gas flow split and flow, and the heat dissipation effect is enhanced. Meanwhile, based on the structure of the magnetic suspension natural gas differential pressure generator, a kind of aerodynamic cooling parameter optimization method of magnetic suspension natural gas differential pressure generator is provided, the aerodynamic simulation precision is improved by adaptive grid technology and multi-scale turbulence model;Heuristic dynamic programming algorithm and utility function are used, and the control input quantity, i.e., the structure parameter, is iteratively optimized by combining the experience playback method, and based on the optimized control input quantity, the structure parameter in the magnetic suspension natural gas differential pressure generator can be adjusted to improve the performance of the magnetic suspension natural gas differential pressure generator. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Fig. 1 is a flow diagram of the aerodynamic cooling parameter optimization method of the magnetic suspension natural gas differential pressure generator in an embodiment of the present application;

[0035] Figure 2 Fig. 2 is a structural diagram of the magnetic suspension natural gas differential pressure generator in an embodiment of the present application;

[0036] Figure 3 Fig. 3 is an elevation view of the fairing in an embodiment of the present application;

[0037] In the figure, 1 - impeller, 2 - stator, 3 - magnetic suspension bearing mechanism, 4 - fairing, 5 - tubular casing, 301 - rotor shaft, 302 - bearing sub-mechanism, 3021 - axial magnetic suspension bearing, 3022 - radial magnetic suspension bearing, 3023 - protection bearing, 501 - inlet casing, 502 - pressure-bearing casing, 503 - outlet casing. DETAILED DESCRIPTION

[0038] The specific embodiments of the present application are described in further detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but are not intended to limit the scope of the present application.

[0039] In view of the problems existing in the prior art, the present application provides a kind of magnetic suspension natural gas pressure difference generator's aerodynamic cooling parameter optimization method, in combination with Figure 1 It can include the following steps:

[0040] Step 1: build a three-dimensional model of the magnetic suspension natural gas pressure difference generator, in combination with Figure 2 Wherein, the magnetic suspension natural gas pressure difference generator includes impeller 1, stator 2, magnetic suspension bearing mechanism 3, fairing 4, tubular casing 5 and multi-gas flow channel, and the magnetic suspension natural gas pressure difference generator is tubular casing 5, fairing 4 and magnetic suspension bearing mechanism 3 from outside to inside, the tubular casing 5 includes inlet casing 501, pressure-bearing casing 502 and outlet casing 503, the inlet casing 501 and the pressure-bearing casing 502 are fixed by rivets, and the pressure-bearing casing 502 and the outlet casing 503 are fixed by rivets;

[0041] The magnetic suspension bearing mechanism 3 includes a rotor shaft 301 and two bearing sub-mechanisms 302, and a stator 2 is arranged between the two bearing sub-mechanisms 302, the stator 2 is an annular permanent magnet, and a deep groove design is adopted, and the stator 2 is fixed in the pressure-bearing casing 502 by inlaying;

[0042] The bearing sub-mechanism 302 includes an axial magnetic suspension bearing 3021, a radial magnetic suspension bearing 3022 and a protection bearing 3023, the two bearing sub-mechanisms 302 are installed at both ends of the rotor shaft 301, both ends of the rotor shaft 301 are fixed in the pressure-bearing casing 502 by a bearing seat, the rotor shaft 301 connects the bearing sub-mechanism 302 by expansion sleeve and drives power generation, and from the center of the rotor shaft 301 to both ends are the radial magnetic suspension bearing 3022, the axial magnetic suspension bearing 3021 and the protection bearing 3023, respectively, the outer ring of the protection bearing 3023, the outer ring of the axial magnetic suspension bearing 3021 and the outer ring of the radial magnetic suspension bearing 3022 are welded and fixed in the fairing 4.

[0043] The two bearing sub-mechanisms 302 are externally provided with a fairing 4, which is an axial protruding spherical streamlined structure, combined with Figure 3 A plurality of circular holes are arranged in the axial center of the fairing 4, and the diameter of the circular holes can be 4 mm, which is used to guide the airflow to pass through the inside of the magnetic suspension bearing mechanism 3 to achieve heat dissipation and effectively reduce the magnetic coupling between the magnetic bearing and the stator 2. The fairing 4 is fixed in the pressure-bearing shell 502 by rivets;

[0044] The impeller 1 is a centripetal turbine structure, and the impeller 1 is fixed with the rotor shaft 301 by embedding, and the impeller 1 is located in the outlet shell 503. From the pressure-bearing shell 502 to the outlet shell 503, the outlet shell 503 is designed to be gradually narrowed at the inlet of the impeller 1. The impeller 1 is used to efficiently convert the pressure difference energy of natural gas into mechanical energy of the rotor shaft 301;

[0045] The multi-gas flow channel includes an inner flow channel and an outer flow channel, combined with Figure 2 , Figure 2 The arrows in the above formula represent the direction of gas flow. The inner flow channel is a flow channel passing through the circular holes of the fairing 4 and the area where the magnetic suspension bearing mechanism 3 is located. The outer flow channel is a flow channel in the area outside the fairing 4 in the tubular shell 5.

[0046] Through the above design, the heat dissipation effect of the airflow in the unit is enhanced, and the energy conversion efficiency is improved.

[0047] Step 2: Based on the three-dimensional model, CFD simulation is performed on the process of natural gas passing through the magnetic suspension natural gas pressure difference generator to obtain the flow field distribution characteristics and temperature field characteristics of the natural gas flowing in the magnetic suspension natural gas pressure difference generator, as well as the actual values of the stator electromagnetic performance, the rotor electromagnetic performance, the stator mechanical strength and the rotor mechanical strength. The flow field distribution characteristics and temperature field characteristics include the Mach number, local temperature gradient, Reynolds number and velocity vector change of the internal area of the magnetic suspension natural gas pressure difference generator.

[0048] Step 3: Based on the Mach number, local temperature gradient, Reynolds number and velocity vector change of the internal area of the magnetic suspension natural gas pressure difference generator, a target grid is constructed by using an adaptive grid division technique.

[0049] For the region in the internal area of the magnetic suspension natural gas differential pressure generator where the Mach number is greater than or equal to 0.6, which mainly appears at the front end of the impeller and the high-speed airflow contraction channel, a first size grid is adopted; for the region where the Mach number is greater than or equal to 0.3 and less than 0.6, which includes the stator channel inlet and the vicinity of the ring hole of the fairing, a second size grid is adopted; for the region where the Mach number is less than 0.3, which includes the structural cavity and the low-speed backflow region, a third size grid is adopted, wherein the first size is smaller than the second size, and the second size is smaller than the third size; a boundary layer refinement grid (y+ controlled within 30) is adopted to correct the wall function, and the first layer thickness is not more than 0.05 mm to ensure the accuracy of the simulation of the temperature gradient distribution, thereby obtaining an initial grid; in the specific implementation process, the numerical value of the first size can be within the range of 0.2 mm to 0.4 mm to ensure the capture of shock waves and strong turbulent effects, the numerical value of the second size can be within the range of 0.5 mm to 1.0 mm, and the numerical value of the third size can be within the range of 1.5 mm to 2.5 mm. For the region in the initial grid where the local temperature gradient is greater than or equal to 100 K / m, i.e., the heating region of the winding, stator, magnetic suspension bearing, etc., a hexahedral main structure grid is adopted, and 2 or 3 layers are automatically encrypted at the boundary, and the maximum local grid size is not more than 0.3 mm, thereby obtaining a first grid; for the region in the first grid where the velocity vector variation is less than 0.5 m / s, a structured coarse grid is adopted to replace it, thereby reducing the number of simulation units and improving the overall simulation efficiency; the grid type and quality control: mainly adopting a multi-region partition adaptive division strategy, and mixedly using structured hexahedral and unstructured tetrahedral / prismatic grids to ensure that the grid orthogonality is better than 0.7 and the minimum twist angle is greater than 20° to avoid numerical dissipation, thereby obtaining a target grid.

[0050] Step 4: For each grid region in the target grid, a turbulence model is constructed according to the Reynolds number obtained in step 2.

[0051] For each grid region in the target grid, it is judged whether the Reynolds number in the grid region is greater than or equal to 10 4 , and in the case where the Reynolds number in the grid region is greater than or equal to 10 4 , a k-ε turbulence model is constructed in the grid region, and in the case where the Reynolds number in the grid region is less than 10 4 , a k-ω turbulence model is constructed in the grid region.

[0052] Step 5: Extracting the turbulence model of all grid regions in the target grid obtains a parameter feature vector, which includes the temperature rise of the winding, the temperature rise of the stator and the pressure drop of the natural gas passing through the magnetic suspension natural gas differential pressure generator, and the parameter feature vector can also include the local Reynolds number, the vorticity distribution, the pressure gradient variation trend, the heat flux density and the velocity vector distribution.

[0053] In the implementation process, the parameter feature vector is compressed in dimension by a dimension reduction technique to form a state input vector for subsequent heuristic dynamic optimization.

[0054] Step 6: Calculate the utility value according to the temperature rise of the winding, the temperature rise of the stator and the pressure drop of the natural gas passing through the magnetic levitation natural gas pressure differential generator, and then calculate the control input based on the utility value, judge whether the utility value is less than or equal to the preset threshold, in the case of the utility value being less than or equal to the preset threshold, the calculated control input is taken as the optimized control input, the optimized control input is used to adjust the structural parameters in the magnetic levitation natural gas pressure differential generator; in the case of the utility value being greater than the preset threshold, return to execute step 3.

[0055] Among them, the utility value is calculated according to the temperature rise of the winding, the temperature rise of the stator and the pressure drop of the natural gas passing through the magnetic levitation natural gas pressure differential generator, which is specifically realized by the following formula:

[0056] ;

[0057] Among them, The utility value is represented by u(t), The difference between the temperature rise of the winding at time t and the preset winding temperature rise is represented by ΔT(t), The difference between the temperature rise of the stator at time t and the preset stator temperature rise is represented by ΔT(t), The difference between the pressure drop of the natural gas passing through the magnetic levitation natural gas pressure differential generator at time t and the preset pressure drop is represented by ΔP(t), The deviation of the actual value of the stator electromagnetic performance from the preset target value is represented by ΔS(t), The deviation of the actual value of the rotor electromagnetic performance from the preset target value is represented by ΔR(t), The deviation of the actual value of the stator mechanical strength from the preset target value is represented by ΔM(t), The deviation of the actual value of the rotor mechanical strength from the preset target value is represented by ΔM(t), The temperature rise weight is represented by wT, The pressure drop weight is represented by wP, The mechanical weight is represented by wM, The electromagnetic weight is represented by wE.

[0058] Among them, the control input based on the utility value specifically includes:

[0059] Step A1: Define the state quantity , the state quantity is represented as:

[0060] ;

[0061] Among them, The deviation of the actual value of the stator mechanical strength from the preset target value is represented by ΔM(t), represents the deviation of the actual value of the rotor mechanical strength from the preset target value, represents the difference between the temperature rise of the winding at t and the preset winding temperature rise, represents the difference between the temperature rise of the stator at t and the preset stator temperature rise, represents the difference between the pressure drop of natural gas passing through the magnetic suspension natural gas differential pressure generator at t and the preset pressure drop;

[0062] Step A2: according to the utility value and the state quantity , the control input quantity is calculated by combining the formula of the minimum cost function.

[0063] The formula of the minimum cost function is as follows:

[0064] ;

[0065] wherein, represents a discount factor, represents the cost value at t, represents the cost value at t, represents the time interval.

[0066] Further, the present application adopts an experience replay method to store the state change, the control input quantity and the corresponding utility value after adjusting the motor structure parameters as a tuple , and stores it in the ER database G; the sampling probability is determined according to the change amount of the utility value or the closeness to the target value, and if a certain set of structure parameter adjustment greatly improves the cooling efficiency, the priority of the corresponding tuple is improved; the sampling probability of the kth tuple is:

[0067] ;

[0068] ;

[0069] wherein, represents the probability of the kth tuple being sampled, represents the weight of the kth tuple, represents the ranking of the kth tuple, is determined by the formula of the utility value, L represents the number of iterations, and a is a hyperparameter, represents the a power of .

[0070] The technical key points of the present application are:

[0071] ​1. The centripetal turbine impeller structure is designed to convert the natural gas pressure difference energy into mechanical energy, the motor structure is modeled by using the ANSYS software, the aerodynamic simulation precision is improved by the adaptive mesh technology and the multi-scale turbulence model, and the best aerodynamic performance is realized;

[0072] 2. The gas flow passage in the differential pressure generator is designed, the fairing is designed in the shape of a sphere and is provided with annular holes, the gas flow is branched to cool the magnetic bearing, and the multi-gas flow channel design makes the gas flow branch and combine, and the heat dissipation effect is enhanced;

[0073] 3. The sealing gasket is arranged at the rear end of the differential pressure generator to change the gas flow passage, the gas on the low-pressure side is concentrated to the force side of the turbine impeller, and the pressure difference energy conversion rate is further improved.

[0074] Compared with the prior art, the advantages of the present application are:

[0075] 1. The centripetal turbine impeller structure can realize the purpose of efficiently converting the natural gas pressure difference energy into mechanical energy during the operation of the magnetic suspension differential pressure generator.

[0076] 2. The gas flow passage in the differential pressure generator and the spherical fairing structure can optimize the gas pressure drop and the motor temperature rise, reduce the magnetic coupling degree, and improve the heat dissipation efficiency and the energy conversion efficiency.

[0077] The above description is only the preferred embodiments of the present disclosure and the explanation of the applied technical principles. It should be understood by those skilled in the art that the scope of the application involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combinations of the above technical features, and should also cover other technical solutions formed by the above technical features or their equivalent features in any combination without departing from the above inventive concept. For example, the above features are replaced with the technical features disclosed in the embodiments of the present disclosure (but not limited to) having similar functions to form technical solutions.

Claims

1. A method for optimizing the aerodynamic cooling parameters of a magnetically levitated natural gas differential pressure generator, characterized in that, include: Step 1: Construct a three-dimensional model of a magnetic levitation natural gas differential pressure generator, wherein the magnetic levitation natural gas differential pressure generator includes an impeller, a stator, a magnetic levitation bearing mechanism, a fairing, a tubular casing, and multiple gas flow channels. From the outside to the inside, the magnetic levitation natural gas differential pressure generator consists of a tubular casing, a fairing, and a magnetic levitation bearing mechanism. The tubular casing includes an inlet casing, a pressure-bearing casing, and an outlet casing. The inlet casing and the pressure-bearing casing are fixed together by rivets. The pressure-bearing casing and the outlet casing are also fixed together by rivets. The magnetic levitation bearing mechanism includes a rotor shaft and two bearing sub-mechanisms. A stator is provided between the two bearing sub-mechanisms. The stator is a ring-shaped permanent magnet with a deep groove design. The stator is fixed inside the pressure housing by an inlay method. The two bearing submechanisms are equipped with fairings on their exteriors. The fairings are axially protruding spherical streamlined structures. Multiple circular holes are arranged in a ring around the axial center point of the fairings. The fairings are fixed to the inside of the pressure machine housing by rivets. The impeller is a radial turbine structure. The impeller is fixed to the rotor shaft by a fitting method. The impeller is located inside the outlet casing. From the pressure casing to the outlet casing, the outlet casing adopts a gradually narrowing design at the impeller inlet. The multi-gas flow channel includes an inner flow channel and an outer flow channel. The inner flow channel is the flow channel that passes through the circular hole of the fairing and through the area where the magnetic levitation bearing mechanism is located. The outer flow channel is the flow channel in the area inside the tubular housing and outside the fairing. Step 2: Based on the three-dimensional model, CFD simulation is performed on the process of natural gas passing through the magnetic levitation natural gas differential pressure generator to obtain the flow field distribution characteristics and temperature field characteristics of natural gas flowing inside the magnetic levitation natural gas differential pressure generator, as well as the actual values ​​of stator electromagnetic performance, rotor electromagnetic performance, stator mechanical strength, and rotor mechanical strength. The flow field distribution characteristics and temperature field characteristics include the Mach number, local temperature gradient, Reynolds number, and velocity vector change in the internal region of the magnetic levitation natural gas differential pressure generator. Step 3: Based on the Mach number, local temperature gradient, Reynolds number, and velocity vector change in the internal region of the magnetic levitation natural gas differential pressure generator, construct the target mesh using adaptive mesh generation technology; Step 4: For each grid region in the target grid, construct a turbulence model based on the Reynolds number obtained in Step 2; Step 5: Extract the turbulence model for all grid regions in the target grid to obtain the parameter feature vector. The parameter feature vector includes the temperature rise of the winding, the temperature rise of the stator, and the pressure drop of natural gas through the magnetic levitation natural gas differential pressure generator. Step 6: Calculate the utility value based on the temperature rise of the windings, the temperature rise of the stator, and the pressure drop of natural gas through the magnetic levitation natural gas differential pressure generator. Then, calculate the control input based on the utility value and determine whether the utility value is less than or equal to a preset threshold. If the utility value is less than or equal to the preset threshold, use the calculated control input as the optimized control input. The optimized control input is used to adjust the structural parameters in the magnetic levitation natural gas differential pressure generator. If the utility value is greater than the preset threshold, return to step 3.

2. The method for optimizing aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator according to claim 1, characterized in that, The bearing sub-mechanism includes an axial magnetic levitation bearing, a radial magnetic levitation bearing, and a protective bearing. The two bearing sub-mechanisms are installed at both ends of the rotor shaft. The two ends of the rotor shaft are fixed to the inside of the press housing by bearing seats. The rotor shaft is connected to the bearing sub-mechanism by a shrink sleeve. From the center of the rotor shaft to both ends are the radial magnetic levitation bearing, the axial magnetic levitation bearing, and the protective bearing, respectively. The outer rings of the protective bearing, the axial magnetic levitation bearing, and the radial magnetic levitation bearing are welded and fixed inside the fairing.

3. The method for optimizing aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator according to claim 1, characterized in that, Step 3 specifically includes: For regions within the magnetic levitation natural gas differential pressure generator with Mach numbers greater than or equal to 0.6, a first-size mesh is used; for regions with Mach numbers greater than or equal to 0.3 and less than 0.6, a second-size mesh is used; and for regions with Mach numbers less than 0.3, a third-size mesh is used. The first size is smaller than the second size, and the second size is smaller than the third size. A boundary layer refinement using wall function correction is employed to refine the mesh, resulting in the initial mesh. For regions in the initial mesh with local temperature gradients greater than or equal to 100 K / m, a hexahedral dominant structure mesh is used, with 2 or 3 layers automatically densified at the boundaries, and the maximum local mesh size not exceeding 0.3 mm, thus obtaining the first mesh. For regions in the first mesh with velocity vector changes less than 0.5 m / s, a structured coarse mesh is used to replace the first mesh, resulting in the target mesh.

4. The method for optimizing aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator according to claim 1, characterized in that, Step 4 specifically includes: For each grid region in the target grid, determine whether the Reynolds number in the grid region is greater than or equal to 10. 4 The Reynolds number in the grid region is greater than or equal to 10. 4 In this case, a k-ε turbulence model is constructed in the grid region where the Reynolds number is less than 10. 4 In this case, a k-ω turbulence model is constructed in the grid region.

5. The method for optimizing the aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator according to claim 1, characterized in that, In step 6, the utility value is calculated based on the temperature rise of the windings, the temperature rise of the stator, and the pressure drop of natural gas through the magnetic levitation natural gas differential pressure generator. This is specifically achieved through the following formula: ； in, Represents utility value. This represents the difference between the temperature rise of the winding at time t and the preset temperature rise of the winding. This represents the difference between the stator temperature rise at time t and the preset stator temperature rise. This represents the difference between the pressure drop of natural gas passing through the magnetically levitated natural gas differential pressure generator at time t and the preset pressure drop. The deviation between the actual value and the preset target value of the stator electromagnetic performance. This refers to the deviation between the actual value of the rotor's electromagnetic performance and the preset target value. This indicates the deviation between the actual value of the stator's mechanical strength and the preset target value. This indicates the deviation between the actual value of the rotor's mechanical strength and the preset target value. Indicates the weighting of temperature rise. Indicates the pressure drop weight. Indicates mechanical weight, Indicates electromagnetic weight.

6. The method for optimizing aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator according to claim 1, characterized in that, Step 6, which calculates the control input based on utility value, specifically includes: Step A1: Define state variables The state quantity Represented as: ； in, This indicates the deviation between the actual value of the stator's mechanical strength and the preset target value. This indicates the deviation between the actual value of the rotor's mechanical strength and the preset target value. This represents the difference between the temperature rise of the winding at time t and the preset temperature rise of the winding. This represents the difference between the stator temperature rise at time t and the preset stator temperature rise. This represents the difference between the pressure drop of natural gas passing through the magnetic levitation natural gas differential pressure generator at time t and the preset pressure drop. Step A2: Based on utility value and state variables By combining the formula for minimizing the cost function, the control input quantity is calculated. .

7. The method for optimizing aerodynamic cooling parameters of a magnetic levitation natural gas differential pressure generator according to claim 6, characterized in that, The formula for minimizing the cost function is expressed as follows: ； in, Indicates the discount factor. This represents the cost value at time t. express The cost value at any given moment Indicates a time interval.

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