CN113890234A - Closed motor cooling device with circulation convection between rotor holes - Google Patents

Closed motor cooling device with circulation convection between rotor holes Download PDF

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Publication number
CN113890234A
CN113890234A CN202111181648.XA CN202111181648A CN113890234A CN 113890234 A CN113890234 A CN 113890234A CN 202111181648 A CN202111181648 A CN 202111181648A CN 113890234 A CN113890234 A CN 113890234A
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air
pressure drop
motor
guide vane
axial
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CN113890234B (en
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史婷娜
康铭
颜冬
张振
夏长亮
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Zhejiang University ZJU
Zhejiang University Advanced Electrical Equipment Innovation Center
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Zhejiang University ZJU
Zhejiang University Advanced Electrical Equipment Innovation Center
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/32—Rotating parts of the magnetic circuit with channels or ducts for flow of cooling medium
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
    • H02K3/12—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors arranged in slots
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
    • H02K3/28—Layout of windings or of connections between windings
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
    • H02K5/20—Casings or enclosures characterised by the shape, form or construction thereof with channels or ducts for flow of cooling medium
    • H02K5/203—Casings or enclosures characterised by the shape, form or construction thereof with channels or ducts for flow of cooling medium specially adapted for liquids, e.g. cooling jackets
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K9/00—Arrangements for cooling or ventilating
    • H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
    • H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
    • H02K9/06—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium with fans or impellers driven by the machine shaft
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K9/00—Arrangements for cooling or ventilating
    • H02K9/19—Arrangements for cooling or ventilating for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Motor Or Generator Cooling System (AREA)

Abstract

The invention discloses a closed motor cooling device with circulation convection among rotor holes. Each yoke part of the rotor core is provided with an axial vent hole; two end plates are fixedly arranged on two end faces of the rotor core respectively, and a plurality of guide vanes are fixedly arranged on each end plate at equal intervals along the circumference; one end of each guide vane, which is far away from the end plate after being tangent to the motor, is arranged close to the shaft center, and then all the guide vanes rotate by the same angle in the same direction around the axial center line of each guide vane, so that an included angle is formed between each guide vane and the shaft center line of the motor and serves as an attack angle of each guide vane; each guide vane and the air flow path in the corresponding axial vent hole form an air sub-path, and the air sub-paths are communicated with each other to form an air loop. The invention does not need to change the structure of the stator and the shell, has short air circulation path, large section of the axial vent hole and small air pressure loss, and improves the heat dissipation capability.

Description

Closed motor cooling device with circulation convection between rotor holes
Technical Field
The invention belongs to a closed motor cooling device in the technical field of motors, and particularly relates to a closed motor cooling device with circulation convection among rotor holes.
Background
The enclosed motor has a more serious heat dissipation problem than the open motor because the air inside the enclosed motor does not flow through the outside. The water cooling structure can effectively suppress the stator temperature, but is not ideal for the rotor cooling effect. Currently, a common air internal circulation cooling structure is usually provided with an air duct on a casing or a stator, and forms a circulation path with a rotor air duct. The scheme has a long circulation path and complex geometric change on the path, and can generate large friction pressure drop and shape resistance pressure drop, so that the air flow is limited, and the heat dissipation effect is influenced.
Disclosure of Invention
In view of the above technical problems, the present invention provides a closed motor cooling device with circulation convection between rotor holes. This structure can make the air in the motor form whole flow between the ventilation hole, forms the inner loop, effectively improves rotor heat-sinking capability.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention comprises a shell, an end cover, a bearing, a stator core, a rotor core, a permanent magnet, an axial vent hole, a guide vane, an end plate, a rotating shaft and a winding;
two end faces of the shell are respectively and fixedly provided with two end covers, a rotating shaft is arranged in the middle of the interior of the shell, and two ends of the rotating shaft respectively penetrate through the two end covers and then are coaxially and movably connected with the two end covers through respective bearings;
the rotor core is coaxially and fixedly sleeved on the rotating shaft, a plurality of permanent magnets which are circumferentially arranged and axially run through are embedded in the rotor core, and each yoke part of the rotor core is provided with an axial vent hole; two end plates are fixedly mounted on two end faces of the rotor core respectively, through holes identical to the axial ventilation holes are formed in the two end plates and are communicated with the axial ventilation holes, a plurality of guide vanes are fixedly mounted on each end plate at equal intervals along the circumference, one ends, far away from the end plates, of the guide vanes are tangent to the motor and are arranged close to the center of the shaft, then all the guide vanes rotate around the axial center line of each guide vane along the same direction by the same angle, so that an included angle is formed between each guide vane and the axial center line of the motor and serves as an attack angle of each guide vane, each guide vane and an air flow path in the corresponding axial ventilation hole form an air sub-path, and the air sub-paths are communicated with each other and then form an air loop; the stator iron core is tightly installed on the inner wall of the machine shell, a plurality of winding axial through grooves are formed in the stator iron core along the circumferential direction and are provided with annular air gaps between the stator iron core and the rotor iron core, and corresponding windings are embedded in the winding axial through grooves respectively.
All along circumference equidistant ground fixed mounting have a plurality of guide vane on every end plate, specifically do:
the number of the guide vanes on each end plate is half of the number of the axial ventilation holes, all the guide vanes on each end plate are arranged at the axial ventilation holes, one axial ventilation hole is arranged between every two adjacent guide vanes on the same end plate at intervals, and the guide vanes on the two end plates are arranged in a staggered mode.
The casing is provided with a plurality of circles of cooling water channels which are axially arranged, and the cooling water channels in all circles are communicated with flowing water.
Each part of air pressure drop in the air sub-path consists of an active pressure drop unit generated by a guide vane and a passive pressure drop unit lost in the air circulation process;
the passive pressure drop unit comprises a deformation pressure drop generated by the narrowing of a channel when air enters the axial vent from the end part of the rotor core; a frictional pressure drop of air flowing within the axial vent; the deformed pressure drop is generated by the widening of the channel when the air flows out of the axial vent hole; the air generates a deformation pressure drop when the end of the rotor core turns.
The self axial length and the attack angle of each guide vane are set by the following guide vane size method:
the method comprises the following steps:
the first step is as follows: presetting the self axial length and attack angle of the initial guide vane;
the second step is that: constructing a pressure loss correction fluid network model based on the air sub-path, and calculating the air flow velocity of each part in the air sub-path under the current self axial length and attack angle of the guide vane according to the pressure loss correction fluid network model;
the third step: constructing a heat network model based on the closed motor cooling device, and calculating the air temperature rise of the motor under the current self axial length and the attack angle of the guide vane by using the heat network model according to the air flow rate in the axial vent hole under the current self axial length and the attack angle of the guide vane;
the fourth step: changing the self axial length and the attack angle of the guide vane, repeating the second step and the third step to obtain the air temperature rise of the motor under the axial length and the attack angle of each guide vane, and selecting the axial length and the attack angle with the lowest air temperature rise of the motor as the optimal axial length and the attack angle of the guide vane.
The second step is specifically as follows:
2.1) dividing the air sub-path into an active pressure drop unit and a passive pressure drop unit, modeling the active pressure drop unit, and setting an active pressure drop unit model according to the following formula:
Figure BDA0003297484110000021
wherein, Δ p1 is generated by the active pressure drop unitThe air pressure drop of (a); v. ofaAir axial velocity, ρ is air density;
2.2) presetting the self axial length and attack angle of the initial guide vane, and solving the air axial velocity v in the active pressure drop unit model by utilizing the chlorophyll-momentum theoryaThus, the air pressure drop generated by the active pressure drop unit under the current self axial length and the attack angle of the guide vane is obtained;
2.3) modeling the passive pressure drop unit, wherein an active pressure drop unit model and a passive pressure drop unit model jointly form a pressure loss correction fluid network model, and the passive pressure drop unit model is set through the following formula:
Δp2＝Δpe+Δpc+Δps+Δpf
Figure BDA0003297484110000031
Figure BDA0003297484110000032
Figure BDA0003297484110000033
Figure BDA0003297484110000034
wherein, Δ p2 is the air pressure drop generated by the passive pressure drop unit, and the passive pressure drop unit comprises a local pressure drop Δ p with suddenly enlarged cross sectioneLocal pressure drop Δ p with suddenly reduced cross sectioncPressure drop Δ p at the turnsAnd the friction pressure drop Δ p in the holef；ke,kcAnd ksRespectively, the coefficient of varying resistance at sudden expansion, sudden contraction and turning, AwAnd AnWide and narrow sections, v is air velocity, f is friction resistance coefficient, L is axial length of motor, DeIs an equivalent diameter, CrIs a spiral correction factor;
and then obtaining the air pressure drop generated by the passive pressure drop unit according to the air pressure drop generated by the active pressure drop unit, and solving by using a passive pressure drop unit model to obtain the air velocity v of each part in the air sub-path under the current self axial length and the attack angle of the guide vane.
The third step is specifically as follows:
3.1) carrying out grid division on a physical model of the closed motor cooling device to construct a thermal network model, wherein each grid is used as a node, the nodes are connected through thermal resistance, and the initial temperature of each node and the initial air temperature rise of the motor are preset;
3.2) calculating the convection heat transfer coefficient of the heat transfer surface corresponding to each node according to the current self axial length of the guide vane and the air flow velocity of each part in the air sub-path under the attack angle, then calculating the heat resistance of each node and air during heat convection, and finally calculating the total heat resistance of each node according to the heat resistance among the nodes;
3.3) calculating various losses in the motor based on the physical model of the closed motor cooling device, and applying the various losses in the motor as heat sources to corresponding nodes;
3.4) solving a thermal conductivity matrix of the thermal network model by utilizing a kirchhoff current law based on the total thermal resistance, the heat source and the temperature of each node, further obtaining the temperature rise of each node and updating the temperature of each node;
3.5) calculating the heat exchanged between the air in the motor and each heat exchange surface according to the temperature rise and the convection heat exchange coefficient of each node, and calculating and updating the air temperature rise of the motor by the following formula based on the air temperature rise of the motor:
Figure BDA0003297484110000041
wherein, cairIs the specific heat capacity of air, VairIs the volume of air in the motor, alpha, A and delta TwRespectively the convective heat transfer coefficient, area and temperature rise, Delta, of each heat transfer surfaceTairIn order to increase the temperature of the air of the motor before the renewal,
Figure BDA0003297484110000042
the temperature of the air of the motor is increased after being updated;
3.6) repeating the steps 3.3) -3.5) until the air temperature rise of the motor is converged, and obtaining the air temperature rise of the motor under the current self axial length and attack angle of the guide vane.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
the invention can make the air in the motor circularly flow through the axial vent hole without changing the structure of the stator and the shell, and has simple process and volume saving.
According to the invention, the guide vanes are arranged on the end plate every two axial ventilation holes, compared with the existing structure, the number of the vanes is reduced by half, and the wind resistance loss is small.
The invention corrects the calculation method of the air friction pressure drop in the ventilation holes of the rotor, better considers the influence of the rotation of the rotor on the friction pressure drop and more accurately calculates the air flow velocity in the holes at different rotating speeds.
The air circulation path of the invention is short, the section of the axial vent hole is large, the complicated geometric change is not generated on the circulation path, the air pressure loss is small, and then, the larger flow in the hole is generated, and the heat dissipation capability is improved.
Drawings
Fig. 1 is an axial sectional view of the entire motor.
Fig. 2 is a schematic radial cross-section of the middle of the machine.
Fig. 3 is a schematic view of an air circulation path of the motor.
FIG. 4 is a schematic view of a micro-bladed unit.
FIG. 5 is a graph showing the stress of lutein.
FIG. 6 is a front and back static pressure schematic of the axial plane of the guide vanes.
Fig. 7 is a fluid network model of an electric machine.
Fig. 8 is a curve showing the variation of the air flow rate in the rotor hole of the motor with the rotation speed of the motor.
Fig. 9 is a thermal network model of the motor.
FIG. 10 is a distribution diagram of maximum temperature rise of a motor rotor varying with guide vane parameters.
In the figure: the structure comprises a machine shell 1, end covers 2, bearings 3, a cooling water channel 4, a stator core 5, a rotor core 6, a permanent magnet 7, an axial vent hole 8, a guide vane 9, an end plate 10, a rotating shaft 11 and a winding 12.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, and it should be understood that the embodiments described herein are merely illustrative and explanatory of the present invention and do not limit the scope of the claims of the present application.
Specific examples are given below:
in the present embodiment, a 48-slot 8-pole closed permanent magnet synchronous motor is used as a research object.
As shown in fig. 1 and 2, the present invention includes a housing 1, an end cap 2, a bearing 3, a stator core 5, a rotor core 6, a permanent magnet 7, an axial vent hole 8, a guide vane 9, an end plate 10, a rotating shaft 11, and a winding 12;
two end faces of the casing 1 are respectively and fixedly provided with two end covers 2 through screws, so that the motor forms a closed structure, a rotating shaft 11 is arranged in the middle of the inside of the casing 1, and two ends of the rotating shaft 11 are respectively coaxially and movably connected with the two end covers 2 through respective bearings 3 after penetrating through the two end covers 2;
the rotor core 6 is coaxially fixed and sleeved on the rotating shaft 11 through a flat key, a plurality of permanent magnets 7 which are circumferentially arranged and axially run through are embedded in the rotor core 6, and each yoke part of the rotor core 6 is provided with an axial vent hole 8; two end plates 10 are fixedly installed on two end faces of the rotor core 6 respectively, through holes identical to the axial ventilation holes 8 are formed in the two end plates 10 and are completely communicated with the axial ventilation holes 8, a plurality of guide vanes 9 are fixedly installed on each end plate 10 at equal intervals along the circumference, one ends, far away from the end plates 10, of all the guide vanes 9 tangent to the motor are arranged close to the shaft center, then all the guide vanes 9 rotate by the same angle along the same direction around the axial center line of each guide vane 9, namely the guide vanes 9 are not parallel to the axial direction, and simultaneously, all the guide vanes 9 are not parallel to all the tangent planes of the motor, so that an included angle is formed between each guide vane 9 and the shaft center line of the motor and serves as an attack angle of each guide vane 9, the included angles between all the guide vanes 9 and the shaft center lines are the same, and all the guide vanes 9 rotate by the same angle along the same direction around the axial center line of each guide vane 9 to ensure that the rotor rotates by the same angle Generating air pressure directed toward the axial vents. Each guide vane 9 and the air flow path in the corresponding axial vent hole 8 form an air sub-path, and the air sub-paths are communicated with each other to form an air loop, as shown in fig. 3; the inner wall of the machine shell 1 is tightly provided with a stator core 5 in a heat shrink fit mode, and an annular air gap is arranged between the stator core 5 and the rotor core 6, wherein the gap is set to be 0.2-5mm in the specific implementation method. A plurality of winding axial through grooves are formed in the stator core 5 along the circumferential direction, corresponding windings 12 are embedded in the winding axial through grooves respectively, and two ends of each winding 12 extend out of the winding axial through groove.
A plurality of guide vanes 9 are fixedly mounted on each end plate 10 at equal intervals along the circumference, specifically:
the number of the guide vanes 9 on each end plate 10 is half of the number of the axial vent holes 8, all the guide vanes 9 on each end plate 10 are all arranged at the axial vent holes 8, one axial vent hole 8 is arranged between every two adjacent guide vanes 9 on the same end plate 10 at intervals, and the guide vanes 9 on the two end plates 10 are arranged in a staggered mode, namely, one guide vane 9 is arranged at one end of each axial vent hole 8, and no guide vane 9 is arranged at the other end of the axial vent hole 8.
The casing 1 is provided with a plurality of circles of cooling water channels 4 which are axially arranged, and each circle of cooling water channel 4 is communicated with flowing water and used for cooling the motor.
Each part of air pressure drop in the air sub-path consists of an active pressure drop unit generated by a guide vane and a passive pressure drop unit lost in the air circulation process;
the passive pressure drop unit comprises deformation pressure drop generated by the narrowing of a channel when air enters the axial vent holes 8 from the end part of the rotor core 6; the frictional pressure drop of the air flowing in the axial vents 8; the deformation pressure drop generated by the widening of the channel when the air flows out of the axial vent holes 8; the air generates a deformation pressure drop when the end of the rotor core 6 is turned.
The axial length and the angle of attack of each guide vane 9 are set by the following guide vane sizing method:
the method comprises the following steps:
the first step is as follows: presetting the self axial length and the attack angle of the initial guide vane 9;
the second step is that: considering the details of the circulation structure between rotor holes of the 48-slot 8-pole closed permanent magnet synchronous motor, constructing a pressure loss correction fluid network model based on the air sub-path, and calculating the air flow rates of all parts in the air sub-path under the current self axial length and attack angle of the guide vane 9 according to the pressure loss correction fluid network model as shown in fig. 7;
the second step is specifically as follows:
2.1) divide into initiative pressure drop unit and passive pressure drop unit with the air sub-circuit, the initiative pressure drop unit is specifically guide vane, models the initiative pressure drop unit, and initiative pressure drop unit model sets up through following formula:
Figure BDA0003297484110000061
where Δ p1 is the air pressure drop generated by the active pressure drop unit (i.e. the static pressure difference between the front and rear ends of the guide vanes, as shown in FIG. 6, p+And p-Static pressures of the front end and the rear end of each guide vane are respectively, the front end of each guide vane is far away from the corresponding end plate 10, and the rear end of each guide vane is close to the end plate 10); v. ofaAir axial velocity, ρ is air density;
2.2) presetting the self axial length and the attack angle of the initial guide vane 9, and solving the air axial velocity v in the active pressure drop unit model by utilizing the phyllotactic-momentum theoryaSo as to obtain the air pressure drop generated by the active pressure drop unit under the current self axial length and attack angle of the guide vane 9;
in particular, according to leafIn principle, the guide vane is divided into a plurality of micro-vane units with the length dx along the axial direction, as shown in fig. 4. The force applied to each of the micro-blade units is shown in fig. 5. In the plane of rotation of each of the micro-vane units, the relative velocity vrelAir annular induced angular velocity omega and rotating speed omega of guide vanefanAngle of attack
Figure BDA0003297484110000062
The mutual relationship of (A) and (B) is as follows:
Figure BDA0003297484110000063
Figure BDA0003297484110000071
further according to classical folacin theory, there are
Figure BDA0003297484110000072
Figure BDA0003297484110000073
Wherein, CLAnd CDThe rotor comprises a rotor body, a rotor blade, a stator blade, a rotor blade, a stator blade, a rotor blade and a rotor blade.
After the simultaneous calculation, the air annular induced angular velocity omega and the air axial velocity v are obtainedaAxial velocity v of airaThe air pressure drop Δ p1 generated by the active pressure drop unit can be obtained by being introduced into the active pressure drop unit model.
2.3) modeling the passive pressure drop unit, wherein an active pressure drop unit model and a passive pressure drop unit model jointly form a pressure loss correction fluid network model, and the passive pressure drop unit model is set through the following formula:
Δp2＝Δpe+Δpc+Δps+Δpf
Figure BDA0003297484110000074
Figure BDA0003297484110000075
Figure BDA0003297484110000076
Figure BDA0003297484110000077
wherein, Δ p2 is the air pressure drop generated by the passive pressure drop unit, and the passive pressure drop unit comprises a local pressure drop Δ p with suddenly enlarged cross sectioneLocal pressure drop Δ p with suddenly reduced cross sectioncPressure drop Δ p at the turnsAnd the friction pressure drop Δ p in the holef；ke,kcAnd ksThe coefficients of resistance to change, respectively sudden enlargement, sudden reduction and turning, can be found in the relevant manual. A. thewAnd AnWide and narrow sections, respectively, v air velocity, f friction drag coefficient, depending on the shape and flow velocity of the cooling path, L axial length of the motor, DeIs an equivalent diameter, CrAs a helical correction factor, Cr＝1+(0.1ωfanDe)2；
And then obtaining the air pressure drop (Δ p1 ═ Δ p2) generated by the passive pressure drop unit according to the air pressure drop generated by the active pressure drop unit, and solving by using a passive pressure drop unit model to obtain the air velocity v of each part in the air sub-path under the current self axial length and the attack angle of the guide vane 9.
FIG. 8 shows the flow velocity in the hole at different rotation speeds calculated by the fluid network model and the CFD simulation, and it can be seen from the CFD simulation result in the figure that the flow velocity in the hole increases with the increase of the rotation speedGradually increasing, but the rate of increase gradually decreasing. The flow velocity in the hole obtained by the traditional friction pressure drop calculation formula is almost linearly increased along with the increase of the rotating speed of the motor, and a spiral correction coefficient C is utilizedrThe numerical value obtained by calculating the corrected friction pressure drop is well matched with the CFD simulation, and the effectiveness of the pressure loss correction fluid network model is demonstrated.
The third step: constructing a heat network model based on the closed motor cooling device, and calculating the air temperature rise of the motor under the current self axial length and the attack angle of the guide vane 9 by utilizing the heat network model according to the air flow rate in the axial vent hole 8 under the current self axial length and the attack angle of the guide vane 9;
the third step is specifically:
3.1) carrying out grid division on a physical model of the closed motor cooling device according to the characteristics of structural size parameters, heating and heat dissipation and the like, wherein the unit structure and the subdivision precision of each grid can be extracted and selected according to the temperature, the area with larger temperature difference can be properly encrypted, a heat network model is constructed, each grid is taken as a node, the nodes are connected through thermal resistance, the thermal resistance among the nodes is solved according to the unit size and the material property of the grid, so that the internal temperature field of the motor is dispersed into an equivalent heat network topology, and the initial temperature of each node and the initial air temperature rise of the motor are preset;
the thermal network model is shown in fig. 9, where nodes 1-5 represent the casing, 6-10 represent the stator yoke, 11-17 represent the windings, 18-22 represent the stator teeth, 23-27 represent the rotor pole shoes, 29-33 represent the permanent magnets, 36-40 show the rotor yoke, and 35 and 41 represent the bearings. The model is established based on the fact that the temperature of each part in the motor can be analogized to voltage, loss is input into each part as a heat source, and analogized to a current source comprising copper loss, iron loss, permanent magnet eddy current loss and mechanical loss. The heat transfer process within the motor includes thermal conduction between solids, convective heat transfer between solids and fluids, and radiative heat transfer, denoted as thermal resistance.
3.2) calculating the convection heat transfer coefficient of each node corresponding to the heat exchange surface according to the air flow velocity of each part in the air sub-path under the current self axial length and the attack angle of the guide vane 9, wherein the heat exchange surface is the surface of each node for carrying out heat exchange with air, then calculating the heat resistance of each node and air during heat convection, and finally calculating the total heat resistance of each node according to the heat resistance among the nodes;
3.3) calculating various losses in the motor based on a physical model of the closed motor cooling device, wherein the losses comprise copper loss, iron loss, eddy current loss of a permanent magnet and mechanical loss, and applying the various losses in the motor as heat sources to corresponding nodes;
3.4) solving a thermal conductivity matrix of the thermal network model by utilizing a kirchhoff current law based on the total thermal resistance, the heat source and the temperature of each node, further obtaining the temperature rise of each node and updating the temperature of each node;
3.5) calculating the heat exchanged between the air in the motor and each heat exchange surface according to the temperature rise and the convection heat exchange coefficient of each node, and under the condition that the air temperature in the cavity below the winding end part is the same, calculating and updating the air temperature rise of the motor by the following formula based on the air temperature rise of the motor:
Figure BDA0003297484110000081
wherein, cairIs the specific heat capacity of air, VairIs the volume of air in the motor, alpha, A and delta TwThe convective heat transfer coefficient, area and temperature rise, delta T, of each heat transfer surfaceairIn order to increase the temperature of the air of the motor before the renewal,
Figure BDA0003297484110000092
the temperature of the air of the motor is increased after being updated;
3.6) repeating the steps 3.3) -3.5) until the air temperature rise of the motor is converged, and obtaining the air temperature rise of the motor under the current self axial length and attack angle of the guide vane 9.
The temperature rise of each node of the motor under the rated working condition is obtained by using the established heat network model and the CFD simulation, and is listed in Table 1. The error value of each node is less than 8% and is within the acceptable range.
TABLE 1 temperature rise of each node of the motor
Figure BDA0003297484110000091
The fourth step: changing the self axial length and the attack angle of the guide vane 9, repeating the second step and the third step to obtain the air temperature rise of the motor under the axial length and the attack angle of each guide vane 9, and selecting the axial length and the attack angle with the lowest air temperature rise of the motor as the optimal axial length and the attack angle of the guide vane 9.
The influence of the axial length of the guide vanes and the included angle between the vanes and the axial direction of the motor on the maximum temperature rise of the rotor is shown in fig. 10. As can be seen from the figure, the highest temperature rise of the rotor is reduced along with the increase of the self axial length of the blade, and the heat exchange area and the flow velocity in the hole of the blade are increased along with the increase of the self axial length of the blade, so that the heat exchange capacity of the rotor is enhanced. In addition, the temperature rise firstly decreases and then increases along with the increase of the attack angle of the blade, because the flow velocity in the hole firstly increases and then decreases along with the increase of the attack angle of the blade, and the windward area of the blade gradually decreases, so the lowest point of the temperature rise is positioned at the balance position where the flow velocity in the hole and the windward area are both large. According to fig. 10, it is finally determined that when the length of the guide vane is 21mm and the angle of attack of the vane is 20 °, the temperature rise of the rotor is the lowest, which indicates that the structure can make the air in the motor flow between the ventilation holes in a staggered manner, so as to form internal circulation, which is effective for improving the heat dissipation capability of the rotor.
The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (7)

1. A closed motor cooling device with circulation convection between rotor holes is characterized in that: the motor comprises a shell (1), an end cover (2), a bearing (3), a stator core (5), a rotor core (6), a permanent magnet (7), an axial vent hole (8), a guide vane (9), an end plate (10), a rotating shaft (11) and a winding (12);
two end faces of the casing (1) are respectively and fixedly provided with two end covers (2), a rotating shaft (11) is arranged in the middle of the inside of the casing (1), and two ends of the rotating shaft (11) are respectively and coaxially and movably connected with the two end covers (2) through respective bearings (3) after penetrating through the two end covers (2);
the rotor iron core (6) is coaxially fixed and sleeved on the rotating shaft (11), a plurality of permanent magnets (7) which are circumferentially arranged and axially run through are embedded in the rotor iron core (6), and each yoke part of the rotor iron core (6) is provided with an axial vent hole (8); two end plates (10) are respectively and fixedly installed on two end faces of the rotor core (6), through holes which are the same as the axial ventilation holes (8) are formed in the two end plates (10) and are communicated with the axial ventilation holes (8), a plurality of guide vanes (9) are fixedly installed on each end plate (10) at equal intervals along the circumference, one end of each guide vane (9) which is far away from the end plate (10) after being tangent to the motor is close to the center of the shaft, then all the guide vanes (9) rotate by the same angle along the same direction around the axial center line of each guide vane (9), an included angle is formed between each guide vane (9) and the shaft center line of the motor and is used as an attack angle of the guide vane (9), each guide vane (9) and an air flow path in the corresponding axial vent hole (8) form an air sub-path, and the air sub-paths are communicated with each other and then form an air loop; a stator core (5) is tightly installed on the inner wall of the machine shell (1), a plurality of winding axial through grooves are formed in the stator core (5) along the circumferential direction and in an annular air gap mode, and corresponding windings (12) are embedded in the winding axial through grooves respectively, wherein the annular air gap stator core (5) is arranged between the stator core (5) and the rotor core (6).
2. The enclosed motor cooling apparatus with circulating convection between rotor bores of claim 1, wherein: all along circumference equidistant fixed mounting have a plurality of guide vane (9) on every end plate (10), specifically do:
the number of the guide vanes (9) on each end plate (10) is half of the number of the axial ventilation holes (8), all the guide vanes (9) on each end plate (10) are arranged at the positions of the axial ventilation holes (8), two adjacent guide vanes (9) on the same end plate (10) are arranged at intervals of one axial ventilation hole (8), and the guide vanes (9) on the two end plates (10) are arranged in a staggered mode.
3. The enclosed motor cooling apparatus with circulating convection between rotor bores of claim 1, wherein: the machine shell (1) is provided with a plurality of circles of cooling water channels (4) which are axially arranged, and the cooling water channels (4) are all communicated with flowing water.
4. The enclosed motor cooling apparatus with circulating convection between rotor bores of claim 1, wherein: each part of air pressure drop in the air sub-path consists of an active pressure drop unit generated by a guide vane and a passive pressure drop unit lost in the air circulation process;
the passive pressure drop unit comprises deformation pressure drop generated by the narrowing of a channel when air enters the axial ventilation holes (8) from the end part of the rotor core (6); a frictional pressure drop of the air flowing in the axial vents (8); the deformation pressure drop is generated by the widening of the channel when the air flows out of the axial vent hole (8); the air generates deformation pressure drop when the end of the rotor core (6) turns.
5. A closed machine cooling device with circulation convection between rotor holes, according to claim 1, characterized in that the own axial length and angle of attack of each guide vane (9) is set by the following guide vane sizing method:
the method comprises the following steps:
the first step is as follows: presetting the self axial length and the attack angle of the initial guide vane (9);
the second step is that: constructing a pressure loss correction fluid network model based on the air sub-path, and calculating the air flow velocity of each part in the air sub-path under the current self axial length and attack angle of the guide vane (9) according to the pressure loss correction fluid network model;
the third step: constructing a heat network model based on the closed motor cooling device, and calculating the air temperature rise of the motor under the current self axial length and the attack angle of the guide vane (9) by utilizing the heat network model according to the air flow speed in the axial vent hole (8) under the current self axial length and the attack angle of the guide vane (9);
the fourth step: changing the self axial length and the attack angle of the guide vane (9), repeating the second step and the third step to obtain the air temperature rise of the motor under the axial length and the attack angle of each guide vane (9), and selecting the axial length and the attack angle with the lowest air temperature rise of the motor as the optimal axial length and the attack angle of the guide vane (9).
6. The cooling apparatus of the enclosed motor with circulation convection between rotor holes as claimed in claim 5, wherein the second step is specifically:
2.1) dividing the air sub-path into an active pressure drop unit and a passive pressure drop unit, modeling the active pressure drop unit, and setting an active pressure drop unit model according to the following formula:
Figure FDA0003297484100000021
wherein Δ p1 is the air pressure drop generated by the active pressure drop unit; v. ofaAir axial velocity, ρ is air density;
2.2) presetting the self axial length and attack angle of the initial guide vane (9), and solving the air axial velocity v in the active pressure drop unit model by utilizing the phyllotactic-momentum theoryaSo as to obtain the air pressure drop generated by the active pressure drop unit under the current self axial length and the attack angle of the guide vane (9);
2.3) modeling the passive pressure drop unit, wherein an active pressure drop unit model and a passive pressure drop unit model jointly form a pressure loss correction fluid network model, and the passive pressure drop unit model is set through the following formula:
Δp2＝Δpe+Δpc+Δps+Δpf
Figure FDA0003297484100000031
Figure FDA0003297484100000032
Figure FDA0003297484100000033
Figure FDA0003297484100000034
wherein, Δ p2 is the air pressure drop generated by the passive pressure drop unit, and the passive pressure drop unit comprises a local pressure drop Δ p with suddenly enlarged cross sectioneLocal pressure drop Δ p with suddenly reduced cross sectioncPressure drop Δ p at the turnsAnd the friction pressure drop Δ p in the holef；ke,kcAnd ksRespectively, the coefficient of varying resistance at sudden expansion, sudden contraction and turning, AwAnd AnWide and narrow sections, v is air velocity, f is friction resistance coefficient, L is axial length of motor, DeIs an equivalent diameter, CrIs a spiral correction factor;
and then obtaining the air pressure drop generated by the passive pressure drop unit according to the air pressure drop generated by the active pressure drop unit, and solving by using a passive pressure drop unit model to obtain the air velocity v of each part in the air sub-path under the current self axial length and the attack angle of the guide vane (9).
7. The cooling device of the enclosed motor with circulation convection between rotor holes as claimed in claim 5, wherein the third step is specifically:
3.1) carrying out grid division on a physical model of the closed motor cooling device to construct a thermal network model, wherein each grid is used as a node, the nodes are connected through thermal resistance, and the initial temperature of each node and the initial air temperature rise of the motor are preset;
3.2) calculating the convection heat transfer coefficient of the heat transfer surface corresponding to each node according to the current self axial length of the guide vane (9) and the air flow velocity of each part in the air sub-path under the attack angle, then calculating the thermal resistance of each node and air during thermal convection, and finally calculating the total thermal resistance of each node according to the thermal resistance among the nodes;
3.3) calculating various losses in the motor based on the physical model of the closed motor cooling device, and applying the various losses in the motor as heat sources to corresponding nodes;
3.4) solving a thermal conductivity matrix of the thermal network model by utilizing a kirchhoff current law based on the total thermal resistance, the heat source and the temperature of each node, further obtaining the temperature rise of each node and updating the temperature of each node;
3.5) calculating the heat exchanged between the air in the motor and each heat exchange surface according to the temperature rise and the convection heat exchange coefficient of each node, and calculating and updating the air temperature rise of the motor by the following formula based on the air temperature rise of the motor:
Figure FDA0003297484100000035
wherein, cairIs the specific heat capacity of air, VairIs the volume of air in the motor, alpha, A and delta TwThe convective heat transfer coefficient, area and temperature rise, delta T, of each heat transfer surfaceairIn order to increase the temperature of the air of the motor before the renewal,
Figure FDA0003297484100000041
the temperature of the air of the motor is increased after being updated;
3.6) repeating the steps 3.3) -3.5) until the air temperature rise of the motor is converged, and obtaining the air temperature rise of the motor under the current self axial length and attack angle of the guide vane (9).
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