CN112260440B

CN112260440B - High-speed centrifugal air compressor

Info

Publication number: CN112260440B
Application number: CN202011087890.6A
Authority: CN
Inventors: 唐云冰; 徐韬; 庄赵栋; 张鸿
Original assignee: Changzhou E&e Turbo Power Co ltd
Current assignee: Changzhou E&e Turbo Power Co ltd
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2022-02-25
Anticipated expiration: 2040-10-13
Also published as: CN112260440A

Abstract

The invention discloses a high-speed centrifugal air compressor, wherein each first conductive connecting lobe comprises a first crossing part and at least two first fixing parts extending along the radial direction of an iron core, the first fixing parts are provided with first through holes, and at least two first copper strips respectively penetrate through the first through holes and then are fixed with the first fixing parts; each second conductive connecting lobe comprises a second spanning part and at least two second fixing parts extending along the radial direction of the iron core, a second through hole is formed in each second fixing part, and at least two second copper bars penetrate through the second through holes and then are fixed with the second fixing parts; each third conductive connecting lobe comprises a third spanning part and at least two third fixing parts extending along the radial direction of the iron core, a third through hole is formed in each third fixing part, and at least two third copper bars penetrate through the third through holes and then are fixed with the third fixing parts. The motor in the high-speed centrifugal air compressor can bear large current so as to meet the requirement of high-speed work.

Description

High-speed centrifugal air compressor

Technical Field

The invention relates to the technical field of compressors, in particular to a high-speed centrifugal air compressor.

Background

The air compressor is responsible for delivering air with specific pressure and flow rate to the electric pile in the fuel cell system, and provides necessary oxygen for the electric pile reaction, and is one of the most core parts in the fuel cell system. The common air compressor at present mainly comprises centrifugal type, roots type, screw type, vortex type, piston type, sliding sheet type and the like. The high-speed centrifugal air compressor has good comprehensive effects in the aspects of efficiency, noise, volume, oil-free performance, power density, manufacturing cost, responsiveness and the like, is considered to be one of the most promising types of air compressors, and can be widely applied to the fields of hydrogen fuel cells, electronic superchargers and the like

The high-speed centrifugal air compressor is also called turbine compressor, and its working principle is that when the impeller is rotated at high speed, under the action of centrifugal force the gas can be thrown into the rear diffuser, and a vacuum zone is formed at the impeller, at the moment the external fresh gas can be fed into the impeller. The impeller is continuously rotated and gas is continuously sucked and thrown out, thereby maintaining continuous flow of gas. The design of the high-speed centrifugal air compressor not only overcomes a plurality of single technologies, but also needs to effectively integrate the single technologies. These single techniques include: the design and processing of a high-efficiency centrifugal compressor, the design and manufacture of an ultra-high-speed motor, the design of an ultra-high-speed permanent magnet synchronous motor controller, the design and manufacture of an ultra-high-speed bearing, the design of high-speed rotor dynamics, the design of a whole machine structure and a thermal management system and the like.

The high-speed motor generally refers to a motor with the rotating speed of more than 10000r/min, and at present, induction motors, permanent magnet motors and switched reluctance motors are mainly used for successfully realizing high speed. The research on high-speed motors in foreign countries has already provided a considerable foundation and the industrial potential is good. Compared with foreign countries, the domestic research on the high-speed motor is weaker in foundation and low in industrialization level, the domestic research on the high-speed motor is mostly concentrated in the range of medium and low power and low rotating speed, and the gap is large from foreign countries. Permanent magnet motors are favored in high speed applications due to their advantages of high power and efficiency factors, large speed range, etc. At present, domestic research on high-speed permanent magnet motors is mainly focused on colleges and universities, and relevant research works are carried out on the aspects of design characteristics, loss characteristics, rotor strength and rigidity calculation, cooling system design, temperature rise calculation and the like of the high-speed motors.

When the electronic supercharger works, because the rotating speed of the electronic supercharger generally rotates at a high speed from tens of thousands of revolutions to more than twenty thousands of revolutions, under the high rotating speed, the motor has large heat productivity, and can obtain the high rotating speed only by obtaining larger current, the stator which adopts the enameled wire as the winding traditionally cannot bear the corresponding current under the working condition of the high rotating speed, and obviously, the structure of the motor in the electronic supercharger needs to be improved. Meanwhile, by using the innovative design of the gas compressor, the axial force of a rotor system is reduced, and the performance and the reliability of the whole machine are improved.

Disclosure of Invention

The invention provides a high-speed centrifugal air compressor, wherein a motor in the high-speed centrifugal air compressor can bear large current so as to meet the requirement of high-speed work.

The technical scheme for solving the technical problems is as follows:

the high-speed centrifugal air compressor comprises a first shell, a second shell, a compressor impeller and a motor, wherein a first containing cavity is arranged on the first shell, the second shell is connected to one end of the first shell, a second containing cavity is formed between the second shell and the first shell, the compressor impeller is located in the second containing cavity, one part of the motor is located in the first contracting cavity, the motor comprises a rotor and a stator, the rotor penetrates through the stator, the rotor is in pivot connection with the first shell, one end of the rotor is located outside the first shell and is connected with the compressor impeller, the stator comprises an iron core located in the first containing cavity and fixed with the first shell, a plurality of first copper strips forming an A phase, a plurality of second copper strips forming a B phase and a plurality of third copper strips forming a C phase, the first copper strips, the second copper strips and the third copper strips respectively penetrate through wire embedding grooves of the iron core, and the first copper strips, the second copper strips and the third copper strips respectively penetrate through wire embedding grooves of the iron core, Two ends of the third copper bar are respectively exposed outside the iron core; characterized in that, the stator still includes:

one end of the first insulating layer is respectively fixed on the end faces of the two axial surfaces of the iron core;

first layer conductive connection assembly, first layer conductive connection assembly's one end is fixed with the other end on first insulating layer, and first layer conductive connection assembly includes one or more along the first electrically conductive connection lamella, the electrically conductive connection lamella of second, the electrically conductive connection lamella of third that iron core circumference arranged, wherein:

each first conductive connecting lobe comprises a first crossing part and at least two first fixing parts extending along the radial direction of the iron core, the first fixing parts are provided with first through holes, and at least two first copper strips respectively penetrate through the first through holes and then are fixed with the first fixing parts;

each second conductive connecting lobe comprises a second spanning part and at least two second fixing parts extending along the radial direction of the iron core, a second through hole is formed in each second fixing part, and at least two second copper bars penetrate through the second through holes and then are fixed with the second fixing parts;

each third conductive connecting lobe comprises a third spanning part and at least two third fixing parts extending along the radial direction of the iron core, a third through hole is formed in each third fixing part, and at least two third copper bars penetrate through the third through holes and then are fixed with the third fixing parts.

The invention has the advantages that: the copper bar with the rectangular or polygonal section is used as a current carrier, the copper bar with the structure can bear larger current, and the motor in the centrifugal air compressor with the rotating belt of up to tens of thousands of revolutions can bear the current required by the centrifugal air compressor during working. In the invention, the first layer of conductive connecting assembly is separated from the end face of the iron core through the first insulating layer, and the first layer of conductive connecting assembly is connected and separated through each phase, so that each copper bar is fixed, and a current loop can be formed among each phase.

Drawings

FIG. 1 is a schematic cross-sectional view of a centrifugal air compressor of the present invention;

FIG. 2 is a schematic view of a rotor according to the present invention;

FIG. 3 is a schematic view of the stator of the present invention;

FIG. 4 is a schematic view of a first copper bar according to the present invention;

FIG. 5 is a schematic view of the core hidden from view in FIG. 3;

fig. 6 is a schematic view of a first layer of conductive connection components;

fig. 7 is a schematic view of a second layer of conductive connection assemblies;

FIG. 8 is a schematic view of a first insulating layer;

FIG. 9 is a schematic view of a first insulating layer;

FIG. 10 is a schematic view of a prior art compressor wheel mated to a first housing;

FIG. 11 is a schematic view of a compressor wheel of the prior art;

FIG. 12 is a schematic view of a compressor wheel of the prior art subjected to static pressure during operation;

FIG. 13 is a schematic view of a compressor wheel of the present invention mated to a first housing;

FIG. 14 is a schematic view of a compressor wheel of the present invention;

FIG. 15 is an enlarged view of portion Q of FIG. 13;

FIG. 16 is a schematic view of a compressor wheel of the present invention under static pressure during operation;

FIG. 17 is a schematic view of the air compressor impeller of the present invention being operated with air intake and exhaust and force;

FIG. 18 is a graph of the relationship between rib height on a compressor wheel and axial force as calculated by the turbomachinery using computational fluid dynamics software;

reference numbers in the drawings:

a first housing 1, a first receiving cavity 10;

a second housing 2, a second receiving cavity 20;

the compressor impeller 3, the impeller back 30, ribs 31, a proximal end 31a, a distal end 31b and an impeller back cavity 32;

a motor 4;

rotor 5, rotor shaft 50, permanent magnet 51, end cover 52, carbon fiber sleeve 53;

the stator 6, the iron core 61, the first copper bar 62, the second copper bar 63 and the third copper bar 64;

a first layer of conductive connection component D1, a second layer of conductive connection component D2, a first conductive connection lobe 65, a first spanning portion 65a, a first fixing portion 65b, a first through hole 65c, a first abdicating space 65D, a second conductive connection lobe 66, a second spanning portion 66a, a second fixing portion 66b, a second through hole 66c, a second abdicating space 66D, a third conductive connection lobe 67, a third abdicating portion 67a, a third fixing portion 67b, a third through hole 67c, a third abdicating space 67D, a fourth conductive connection lobe 68, a fourth abdicating portion 68a, a fourth fixing portion 68b, a fourth through hole 68c, a radially extending portion 69, a first insulation layer J1, a first annular portion J1a, a first connection portion J1b, a first mounting hole J1c, a second insulation layer J2, a second annular portion J2a, a second connection portion J2b, and a second mounting hole J1 c.

Detailed Description

As shown in fig. 1, the high-speed centrifugal air compressor of the present invention includes a first housing 1, a second housing 2, a compressor impeller 3, and a motor 4, wherein the first housing 1 is provided with a first receiving cavity 10, the second housing 2 is connected to one end of the first housing 1, a second receiving cavity 20 is formed between the second housing 2 and the first housing 1, the compressor impeller 3 is located in the second receiving cavity 20, and a portion of the motor 4 is located in the first contracting cavity 10.

As shown in fig. 1, the motor 4 includes a rotor 5 and a stator 6, the rotor 5 passes through the stator 6, the rotor 5 is pivotally connected to the first housing 1, and one end of the rotor 5 is located outside the first housing 1 and connected to the compressor wheel 4. As shown in fig. 2, the rotor 5 is a permanent magnet rotor, the rotor 5 includes a rotor shaft 50, a permanent magnet 51, an end cover 52 and a carbon fiber sleeve 53, the rotor shaft 50 is connected to the bearing 1a, the bearing 1a is supported on the first housing, the rotor shaft 50 passes through the permanent magnet 51, the carbon fiber sleeve 53 is sleeved on the circumferential surface of the permanent magnet 51, the end cover 52 is respectively installed at two ends of the permanent magnet 51, and preferably, a part of the end cover 52 is in interference fit in the carbon fiber sleeve 53.

Like fig. 2, rotor 5 adopts carbon fiber cover 53 ligature permanent magnet 51, avoids centrifugal force to throw away permanent magnet 51, and the light inertia of carbon fiber cover 53 quality is little, and it is great to compare in the conductivity of traditional alloy cover, and space and time harmonic can produce great eddy current loss in the alloy protective sheath, and carbon fiber cover 53's conductivity is little, can effectively restrain the eddy current loss in the protective sheath, and permanent magnet rotor 5 adopts the formula of pasting of permanent magnet 51 face, and rotor 5 radius of gyration is little like this, and space utilization is high.

As shown in fig. 2, the rotor shaft 50 is assembled with the end cover 52 at the left end (seen from the figure) in an interference manner, the positioning function is achieved in the axial direction, the permanent magnets 51 are uniformly adhered according to the circumference, the end cover 52 at the right end (seen from the figure) is installed to compress the other end of the magnetic steel, and finally the carbon fiber sleeve 53 is pressed into the outer diameter of the permanent magnet 51 through a tool to bind the permanent magnet, so that the magnetic steel is prevented from being thrown away under the action of centrifugal force.

As shown in fig. 3, the stator 6 includes an iron core 61 located in the first receiving cavity 10 and fixed to the first housing 10, a plurality of first copper bars 62 forming a phase a, a plurality of second copper bars 63 forming B phase, and a plurality of third copper bars 64 forming C phase, the first copper bars 62, the second copper bars 63, and the third copper bars 64 respectively pass through the wire embedding slots of the iron core 61, and two ends of the first copper bars 62, the second copper bars 63, and the third copper bars 64 are respectively exposed outside the iron core 61. The first copper bar 62, the second copper bar 63 and the third copper bar 64 are wrapped with insulating polyimide tapes and then penetrate through the iron core 61.

In the embodiment, the iron core 61 is made of the high-frequency low-iron-loss non-oriented 0.2mm B20AT1200 silicon steel sheet adhesive, compared with the traditional iron core connection process which mainly comprises rivet riveting, laser welding, self-buckling and overlapping riveting and other modes, because the modes damage the insulating layer of the silicon steel sheet to a certain extent, a low-impedance loop is easily formed, large current which is many times higher than normal current is generated in the low-impedance loop, the heat is easily generated, the deterioration and aging of insulation are accelerated, and the iron core is bonded by an adhesive coating to avoid the defects of the traditional process.

In this embodiment, as shown in fig. 3 and 4, the cross sections of the first copper bar 62, the second copper bar 63, and the third copper bar 64 are all rectangular or polygonal, and the conventional copper wire winding structure is replaced by the copper bars with such a structure, which enables the motor to have more copper and a higher copper/total volume coefficient, and the current-carrying capacity of the current to be large, so that the operation performance and efficiency of the motor are better. Preferably, the inner walls of the first copper bar 62, the second copper bar 63 and the third copper bar 64 are provided with radial extending parts 69 extending along the radial direction of the stator, and the volume of each copper bar can be further increased through the radial extending parts 69, so that the current carrying capacity of the current is further improved.

As shown in fig. 4 and 5, the stator 6 further includes a first insulating layer J1 and a first layer of conductive connecting assembly D1, one end of the first layer of conductive connecting assembly D1 is fixed to the other end of the first insulating layer J1, the first layer of conductive connecting assembly D1 includes one or more first conductive connecting lobes 65, second conductive connecting lobes 66, and third conductive connecting lobes 67, which are arranged along the circumferential direction of the core 61, in this embodiment, the number of the first conductive connecting lobes 65, the second conductive connecting lobes 66, and the third conductive connecting lobes 67 is 2, and the first conductive connecting lobes 65, the second conductive connecting lobes 66, and the third conductive connecting lobes 67 are alternately arranged along the same circumference.

As shown in fig. 6, each first conductive connecting lobe 65 includes a first spanning portion 65a and at least two first fixing portions 65b extending along the radial direction of the core 61, a first through hole 65c is formed in each first fixing portion 65b, at least two first copper bars 62 respectively pass through the first through hole 65c and then are fixed to the first fixing portion 65b, each second conductive connecting lobe 66 includes a second spanning portion 66a and at least two second fixing portions 66b extending along the radial direction of the core 61, a second through hole 66c is formed in each second fixing portion 66b, and at least two second copper bars 63 respectively pass through the second through holes 66c and then are fixed to the second fixing portions 66 b; each third conductive connecting lobe 67 includes a third spanning portion 67a and at least two third fixing portions 67b extending along the radial direction of the iron core 61, a third through hole 67c is formed in the third fixing portion 67b, and at least two third copper bars 64 are fixed with the third fixing portion 67b after passing through the third through hole 67 c.

As shown in fig. 6, a first relief space 65d is formed between the first spanning portion 65a and the first fixing portion 65b, a second relief space 66d is formed between the second spanning portion 66a and the second fixing portion 66b, and a third relief space 67d is formed between the third spanning portion 67a and the third fixing portion 67 b.

As shown in fig. 5, the stator 6 further includes a second insulating layer J2 and a second layer of conductive connecting assembly D2, two layers of first layer of conductive connecting assembly D1 are disposed at one end of the iron core 61, the two layers of first layer of conductive connecting assembly are separated by the second insulating layer J2, the other end of the iron core 61 is further disposed with a layer of second layer of conductive connecting assembly D2, the first layer of conductive connecting assembly D1 is separated from the second layer of conductive connecting assembly D2 by the second insulating layer J2, and the first layer of conductive connecting assembly D1 and the second layer of conductive connecting assembly D2 are both fixed to the second insulating layer J2.

As shown in fig. 4 and 5, at least a portion of the first copper bars 62 forming the phase a, the second copper bars 63 forming the phase B, and the third copper bars 64 forming the phase C is not connected to the first layer of conductive connecting assembly, and the first copper bars 62, the second copper bars 63, and the third copper bars 64 which are not connected to the first layer of conductive connecting assembly are connected to the second layer of conductive connecting assembly through the first offset space 65d, the second offset space 66d, and the third offset space 67d, respectively.

As shown in fig. 4 and 7, the second layer conductive connection assembly D2 includes one or more first conductive connection lobe 65, second conductive connection lobe 66, third conductive connection lobe 67, and fourth conductive connection lobe 68 arranged along the circumference of the core 61.

As shown in fig. 7, the fourth conductive connecting lobe 68 includes a fourth spanning portion 68a and three fourth fixing portions 68B extending along the radial direction of the core 61, a fourth through hole 68C is formed in the fourth fixing portion 68B, and one first copper bar 62 in the phase a, one second copper bar 63 in the phase B, and one third copper bar 64 in the phase C respectively pass through one fourth through hole 68C and then are fixed to the corresponding fourth fixing portion 68B. A fourth relief space 68d is formed between two adjacent fourth fixing portions 68 b.

As shown in fig. 4, 5 and 8, the first insulating layer J1 includes a first annular portion J1a and a plurality of first connecting portions J1b disposed on an inner circumferential surface of the first annular portion J1a, two first mounting holes J1c are disposed on each first connecting portion J1b, and the first copper bar 62, the second copper bar 63 and the third copper bar 64 respectively pass through the first mounting holes J1c and are in clearance fit or transition fit with the first mounting holes J1 c.

As shown in fig. 4, 5 and 9, the second insulation layer J2 includes a second annular portion J2a and a plurality of second connecting portions J2b disposed on an inner circumferential surface of the second annular portion J2a, two second mounting holes J1c are disposed on each second connecting portion J2b, and the first copper bar 62, the second copper bar 63 and the third copper bar 64 respectively pass through the second mounting holes J2c and are in clearance or transition fit with the second mounting holes J2 c.

In the conventional exhaust gas turbocharger, a turbine is fixed at one end of a rotating shaft, a compressor impeller is fixed at the other end of the rotating shaft, the rotating shaft is supported by a bearing 1a installed on a shell, when the common exhaust gas turbocharger works, the axial force from the compressor impeller is counteracted through the pressure at the turbine end, namely, the turbine end generates a leftward axial force when working, the compressor impeller 3 generates a rightward axial force when working, the axial forces generated at the turbine end and the compressor impeller end are opposite, and the two axial forces are almost equal in size, so that the axial force loaded on the bearing supporting the rotating shaft of the turbine and the compressor impeller is almost zero, and the bearing is subjected to small abrasion.

As shown in fig. 10 and 11, the centrifugal air compressor is different from a general exhaust gas turbocharger in that a compressor wheel 3 in the centrifugal air compressor is directly driven by an electric motor to continuously force air into an engine. The advantage of direct connection of the motor is that higher efficiency and faster response speed are brought, when the centrifugal air compressor works, the pressure of air at the trailing edge of the compressor impeller 3 reaches the maximum, the space distance between the back 30 of the impeller facing the first housing 1 of the compressor impeller 3 and the trailing edge is very close, the airflow can seep into the back cavity 32 between the back 30 of the impeller and the first housing 1 from the trailing edge and stay in the back cavity 32 of the impeller, with the high-speed rotation of the compressor impeller 3, the air left in the back cavity 32 of the impeller forms a pressure P (as shown in fig. 12) to the compressor impeller 3, the pressure P is only next to the pressure at the trailing edge of the compressor impeller 3, at this time, the back 30 of the impeller receives a great pressure, so that the axial acting force generated to the rotor shaft 50 faces one direction, and the whole rotor assembly generates a great load to the bearing 1a, and finally the abrasion of the bearing 1a is intensified, reducing the life of the bearing.

Referring to fig. 13 and 14, in order to overcome the problem of bearing abrasion of the support rotor 5 caused by air pressure entering between the back surface 30 of the impeller and the first housing 1 in the centrifugal air compressor, in the present invention, the back surface 30 of the impeller, facing the first housing 1, of the compressor impeller 3 is provided with a plurality of ribs 31 for reducing the axial force applied to the compressor impeller 3 during operation, and the ribs 31 are connected with the back surface 30 of the impeller to form a whole, such as by casting the ribs 31 and the compressor impeller 3 to form a whole, or by forming the compressor impeller 3 first and then machining the back surface 30 of the impeller of the compressor impeller 3 to form a plurality of grooves, and the protruding part between two adjacent grooves is the rib 31.

As shown in fig. 14, the ribs 31 preferably protrude from the impeller back 30. One end of each rib 31 is a proximal end 31a, the other end of each rib 31 is a distal end 31b, and the proximal ends 31a and the distal ends 31b are not on the same circumference. More preferably, the ribs 31 are parallel to the radial direction of the compressor wheel 3.

As shown in fig. 16, when the compressor wheel 3 rotates, it is obvious that the ribs 31 rotate with the compressor wheel 3, and the ribs 31 agitate the gas in the wheel back cavity 32, so that the gas in the almost static state flows, and the average circumferential velocity of the gas flow in the wheel back cavity 32 increases, and further the radial pressure gradient in the wheel back cavity 32 is increased, i.e. a counter pressure P1 against the pressure P is generated, so that the axial force (e.g. forward) applied to the wheel back 30 is reduced, and on one side of the vane passage (i.e. the gas compression passage), the flow state is hardly affected by the increased ribs 31, so that the backward axial force is substantially unchanged, and the axial force applied to the bearing is reduced, and thus the wear of the bearing can be reduced.

As shown in fig. 17, the axial force applied to the compressor wheel 3 is calculated by the following process:

F_c＝-F_c1-F_c2+F_c3

in the above formula, F_cAxial force to which the compressor impeller is subjected, F_c1For gas forces acting on the inlet face of the compressor wheel, F_c2For gas forces acting on the outer diameter of the compressor wheel from the inlet to the outlet outer diameter, F_c3Is the gas force acting on the back of the impeller of the compressor;

for gas force F acting on inlet face of compressor impeller_c1The static pressure at the inlet face and the intake air velocity and flow rate can be calculated by the following equation:

in the above formula, r_c1Is the casing radius, p, at the inlet of the compressor impeller_c1Static pressure of inlet face of compressor impeller, M_cFor compressor impeller inlet flow, C₀₁Air intake speed:

gas force F acting on the outer diameter of the inlet to the outer diameter of the outlet of a compressor wheel_c2The diameter of the inlet and the outlet of the impeller of the gas compressor and the static pressure of the outlet are mainly determined, and the calculation can be carried out according to the following formula:

in the above formula, r_c2Is the compressor impeller exit radius, p_c2Static pressure of an outlet of an impeller of the gas compressor;

after reinforcing ribs are added on the back surface of the impeller, the pair F_c3Is greater, so the gas force F acting on the back of the impeller is greater_c3The correction is made as follows:

F_c3＝F_c30(1-η)

in the above formula, F_c30For F calculated by using conventional model_c3The value of (n) is a correction coefficient considering the back reinforcement of the impeller;

in the above formula, r_c3Is a radius, p_c3Is a radius equal to r_c3The static pressure of (c);

in the above formula, s is the gap width of the back cavity of the impeller, and h is the rib height.

After the rib 31 is additionally arranged on the back surface 30 of the impeller 3 of the vane machine impeller 3, the influence of the axial force of the vane machine impeller 3 is verified as follows:

the model with the ribs 31 and the model without the ribs 31 on the back surface 30 of the impeller are subjected to full three-dimensional numerical simulation respectively, in order to fully evaluate the influence of the compressor impeller 3 with the ribs 31 on the axial force of the bearing and consider the influence of the ribs 31 on the pneumatic efficiency of the compressor impeller 3, the compressor impeller 3 and the impeller back cavity 32 are combined, and a structural grid is constructed for the whole calculation domain to improve the calculation precision.

The numerical calculation is carried out by adopting ANSYS CFX (impeller mechanical application computational fluid dynamics software), an impeller channel and an impeller back cavity 32 are set as rotating domains, the rotating speed is 100000rpm, the total temperature and the total pressure of an inlet of the compressor impeller 3 and the speed direction are given, the outlet back pressure (static pressure) of the outlet of the compressor impeller 3 and the outlet back pressure (static pressure) of the impeller back cavity 32 close to a rotor shaft is given, a k-e model is selected as a turbulence model, and all wall surfaces are non-slip heat insulation wall surfaces.

As shown in fig. 15, in order to quantitatively evaluate the influence rule of the height of the ribs 31 on the impeller back 30 on the axial force, 5 sets of calculation schemes are provided, including 4 sets of schemes with ribs 31 with different heights on the impeller back 30 and 1 set of schemes without the ribs 31. The gap width s of the impeller back cavity 32 is set to be 1.3mm, the height h of the ribs 31 is respectively 0.4mm (scheme 1), 0.6mm (scheme 2), 0.8mm (scheme 3) and 1mm (scheme 4), and the ratio of the height h of the ribs 31 to the gap width s of the impeller back cavity 32 in the 4-group scheme is respectively 30.8%, 46.2%, 61.5% and 76.9%.

As shown in fig. 18, when the results are processed, the axial forces applied to the large blade, the small blade, the hub and the back 30 of the impeller of the compressor impeller 3 are vector-summed, so as to obtain the axial force applied to the compressor impeller 3 under the working condition. The relationship of fig. 18 is obtained by comparing the model without ribs with ribs 31 added to the back 30 of the impeller and carrying out non-dimensionalization treatment on the axial force values.

It can be seen that, as the height of the impeller back 30 added with the ribs 31 increases, the axial force applied to the impeller back 30 decreases, the axial force applied to the impeller in the calculated scheme is decreased by about 44% at most, and the effect of decreasing the axial force applied to the impeller back 30 by adding the ribs 31 to the impeller back 30 is obvious. The main feature is that the rotation effect of the ribs 31 added to the impeller back 30 increases the average circumferential speed of the air flow in the impeller back cavity 32, and further increases the radial pressure gradient in the impeller back cavity 32, so that the forward axial force applied to the impeller back 30 is reduced, and on one side of the blade channel, the flow state is hardly affected by the height of the ribs 31 added to the impeller back 30, so that the backward axial force is basically unchanged, and the total axial force is reduced.

The influence of the ribs 31 arranged on the back surface 30 of the impeller on the axial force is considered, and meanwhile, the influence of the ribs on the pneumatic efficiency of the centrifugal compressor is also evaluated, and numerical simulation results show that the pneumatic performance of the centrifugal compressor is hardly influenced after the ribs 31 are additionally arranged on the back surface 30 of the impeller as shown in the following table.

Scheme(s)	Flow (kg/s)	Total to total efficiency
			Rib-free bar	0.1205	0.840
With ribs (plan 1)	0.1199	0.837
			With ribs (plan 2)	0.1203	0.838
With ribs (plan 3)	0.1224	0.838
			With ribs (plan 4)	0.1234	0.838

Through the above calculation and experimental demonstration, it is obvious that the following advantages are obtained after the ribs 31 are provided on the impeller back surface 30:

(1) the axial force of the compressor impeller during working can be obviously reduced by 50% to the maximum extent, and the method is suitable for the condition of using the compressor alone;

(2) the structure of the impeller body of the compressor is not greatly changed, the cost is low and the implementation is easy;

(3) the axial force of the compressor impeller is effectively reduced, and the strength of the compressor impeller is increased;

(4) the structure has wide application range, and can be further popularized to the disc structure which is subjected to aerodynamic force during working.

Claims

1. A high-speed centrifugal air compressor comprises a first shell (1), a second shell (2), a compressor impeller (3) and a motor (4), wherein a first accommodating cavity (10) is arranged on the first shell (1), the second shell (2) is connected to one end of the first shell (1), a second accommodating cavity (20) is formed between the second shell (2) and the first shell (1), the compressor impeller (3) is positioned in the second accommodating cavity (20), one part of the motor (4) is positioned in the first accommodating cavity (10), the motor (4) comprises a rotor (5) and a stator (6), the rotor (5) penetrates through the stator (6), the rotor (5) is pivotally connected with the first shell (1), one end of the rotor (5) is positioned outside the first shell (1) and is connected with the compressor impeller (3), the stator (6) comprises an iron core (61) which is positioned in the first accommodating cavity (10) and is fixed with the first shell (1), characterized in that the stator (6) further comprises: the transformer comprises a plurality of first copper strips (62) forming an A phase, second copper strips (63) forming a B phase and third copper strips (64) forming a C phase, wherein the first copper strips (62), the second copper strips (63) and the third copper strips (64) respectively penetrate through wire embedding grooves of an iron core (61), and two ends of the first copper strips (62), the second copper strips (63) and the third copper strips (64) are respectively exposed outside the iron core (61);

a first insulating layer (J1), wherein the two axial end faces of the iron core (61) are respectively fixed with the first insulating layer (J1);

a first layer of conductive connection assembly (D1), one end of the first layer of conductive connection assembly (D1) being fixed with the other end of the first insulating layer (J1), the first layer of conductive connection assembly (D1) comprising one or more first conductive connection lobe (65), second conductive connection lobe (66), third conductive connection lobe (67) arranged circumferentially along the core (61), wherein:

each first conductive connecting lobe (65) comprises a first spanning part (65a) and at least two first fixing parts (65b) extending along the radial direction of the iron core (61), a first through hole (65c) is formed in each first fixing part (65b), and at least two first copper strips (62) are fixed with the first fixing parts (65b) after penetrating through the first through holes (65c) respectively;

each second conductive connecting lobe (66) comprises a second spanning part (66a) and at least two second fixing parts (66b) extending along the radial direction of the iron core (61), a second through hole (66c) is formed in each second fixing part (66b), and at least two second copper bars (63) respectively penetrate through the second through holes (66c) and then are fixed with the second fixing parts (66 b);

each third conductive connecting lobe (67) comprises a third spanning part (67a) and at least two third fixing parts (67b) extending along the radial direction of the iron core (61), third through holes (67c) are formed in the third fixing parts (67b), and at least two third copper bars (64) penetrate through the third through holes (67c) and then are fixed with the third fixing parts (67 b);

the back surface (30) of the compressor impeller (3) facing the impeller of the first shell (1) is provided with a plurality of ribs (31) for reducing the axial force borne by the compressor impeller (3) during working;

the axial force borne by the compressor impeller (3) is calculated through the following process:

F_c＝-F_c1-F_c2+F_c3

for gas force F acting on inlet face of compressor impeller_c1Relative to inlet face static pressure and inlet air velocity and flow, is calculated by:

gas force F acting on the outer diameter of the inlet to the outer diameter of the outlet of a compressor wheel_c2The method is mainly determined by the inlet and outlet diameters and outlet static pressure of the impeller of the gas compressor, and is calculated according to the following formula:

after ribs are added on the back of the impeller, F is paired_c3Is greater, so the gas force F acting on the back of the impeller is greater_c3The correction is made as follows:

F_c3＝F_c30(1-η)

in the above formula, r_c0Is the compressor impeller radius, r_c3Is a radius, p_c3Is a radius equal to r_c3The static pressure of (c);

in the above formula, s is the gap width of the back cavity of the impeller, and h is the rib height;

the gap width s of the back cavity of the impeller is set to be 1.3mm, the rib heights h are respectively 0.4mm, 0.6mm, 0.8mm and 1mm, and the ratio of the rib heights h to the gap width s of the back cavity of the impeller is respectively 30.8%, 46.2%, 61.5% and 76.9%.

2. A high-speed centrifugal air compressor according to claim 1, characterized in that the first (62), second (63) and third (64) copper bars are polygonal in cross-section.

3. A high speed centrifugal air compressor as recited in claim 1, wherein:

a first relief space (65d) is formed between the first spanning part (65a) and the first fixing part (65 b);

a second relief space (66d) is formed between the second spanning part (66a) and the second fixing part (66 b);

a third relief space (67d) is formed between the third spanning portion (67a) and the third fixing portion (67 b).

4. A high-speed centrifugal air compressor according to claim 3, further comprising: a second insulating layer (J2), a second layer of conductive connection members (D2);

the two ends of the iron core (61) are respectively provided with a first layer of conductive connecting assembly (D1) and a second layer of conductive connecting assembly (D2), the first layer of conductive connecting assembly (D1) and the second layer of conductive connecting assembly (D2) are separated by a second insulating layer (J2), and the first layer of conductive connecting assembly (D1) and the second layer of conductive connecting assembly (D2) are fixed with the second insulating layer (J2);

at least one part of a plurality of first copper bars (62) forming the phase A, a plurality of second copper bars (63) forming the phase B and a plurality of third copper bars (64) forming the phase C is not connected with the first layer of conductive connecting assembly (D1), and the first copper bars (62), the second copper bars (63) and the third copper bars (64) which are not connected with the first layer of conductive connecting assembly (D1) are respectively connected with the second layer of conductive connecting assembly (D2) through a first abdicating space (65D), a second abdicating space (66D) and a third abdicating space (67D).

5. A high-speed centrifugal air compressor according to claim 4, characterized in that the second layer conductive connection assembly (D2) comprises:

one or more first (65), second (66), third (67) and fourth (68) electrically conductive connection lobes arranged circumferentially along the core (61);

the fourth conductive connecting lobe (68) comprises a fourth spanning part (68a) and three fourth fixing parts (68B) extending along the radial direction of the iron core (61), a fourth through hole (68C) is formed in each fourth fixing part (68B), and a first copper bar (62) in the phase A, a second copper bar (63) in the phase B and a third copper bar (64) in the phase C are fixed with the corresponding fourth fixing parts (68B) after respectively penetrating through one fourth through hole (68C).

6. The high-speed centrifugal air compressor according to claim 1, wherein the first insulation layer (J1) comprises a first annular portion (J1a) and a plurality of first connection portions (J1b) arranged on an inner circumferential surface of the first annular portion (J1a), two first mounting holes (J1c) are arranged on each first connection portion (J1b), and the first copper bar (62), the second copper bar (63) and the third copper bar (64) respectively pass through the first mounting holes (J1c) and are in clearance fit or transition fit with the first mounting holes (J1 c).

7. A high-speed centrifugal air compressor according to claim 1, wherein one end of the ribs (31) is a proximal end and the other end of the ribs (31) is a distal end, the proximal and distal ends not being on the same circumference.

8. A high-speed centrifugal air compressor according to claim 1, characterized in that the ribs (31) are parallel to the radial direction of the compressor wheel (3).