RU2034999C1 - Centrifugal cryogenic compressor - Google Patents

Abstract

FIELD: cryogenic engineering. SUBSTANCE: compressor comprises housing 1 and end shields 2 and 3. Shaft 7 of the compressor rotor is mounted in radial gas dynamic bearings 4 and 5 and thrust bearing 6. A roll of the rotor of the driving electric motor, having massive magnetic conductor and two dummy pockets to form two clearly defined poles, is positioned on shaft 7. The end face parts of the rotor roll are short-circuiting rings of a ferromagnet short- circuited winding. There is an additional short- circuited winding provided with rods and short-circuited rings 13. In addition, the working wheel of compressor 14 and thrust journal 15 of axial gas dynamic bearing provided with armature 16 of speed pickup 17 having leads 18 is mounted on shaft 7. Cover 19, whose internal side is provided with thrust bearing 20, is secured to the housing. The stator of the driving engine of the compressor mounted inside the housing consists of magnetic conductor 21 and three-phase winding 22 received in grooves of the magnetic conductor. The leads of the winding are connected to a frequency converter through a switch for changing regimes of operation of the driving electric motor. Screw passage 25 for circulation of a coolant is also made in the housing. The flowing part of compressor 26, including diffuser 27 and spiral scroll 28, is mounted on the housing from the side of the working wheel. EFFECT: enhanced efficiency. 3 cl, 4 dwg

Description

 The invention relates to cryogenic technology and can be used in centrifugal cryogenic compressors on gas supports.

Known centrifugal cryogenic compressors, which are a device in which the flow part, impeller and high-frequency drive motor of the compressor are structurally combined [1]
Also known is a centrifugal helium compressor containing an impeller, a diffuser, a spiral scroll and a high-frequency asynchronous electric motor drive, the cylindrical rotor barrel of which with a lined magnetic circuit and a short-circuited winding is located on a shaft that is integrated with the impeller and mounted vertically on radial and axial gas-dynamic supports in bearings a single housing, inside of which are located the stator of the drive electric motor and its forced cooling system [2]
The disadvantages of a centrifugal cryogenic compressor are:
the presence of dry contact in the axial gas-dynamic support, loaded with the total gravity of the rotor, when starting and stopping the compressor and reduced in this regard, the durability of its axial bearings;
reduced rigidity of the compressor rotor shaft at the location of the rotor barrel of the drive motor, which leads to a significant reduction in the frequency of natural transverse vibrations of the compressor rotor and the limitation of its operating speed;
increased complexity of manufacturing and dynamic balancing of the compressor rotor;
unsatisfactory starting properties of the compressor in the case of powering its high-frequency drive motor from a group source, for example, an electric machine frequency converter.

 The objectives of the invention is to ensure trouble-free operation when starting and stopping the compressor and increasing the durability of its axial bearings; increasing the operating frequency of the compressor rotor, simplifying its manufacture and dynamic balancing; improvement of compressor starting properties.

 This is achieved by the fact that the centrifugal cryogenic compressor contains an impeller, a diffuser, a spiral scroll and a high-frequency drive electric motor, the rotor barrel of which with a lined magnetic circuit and a short-circuited winding is located on a single shaft with the impeller mounted vertically on radial and axial gas-dynamic supports by means of bearing shields in a single housing, inside of which are located the stator of the drive electric motor and its forced cooling system; the inner surface of the stator magnetic circuit and the outer surface of the magnetic barrel of the rotor of the drive electric motor are conical with the same taper angle, the value of which is determined based on the requirement that the absolute values of the axial electromagnetic force applied to the rotor barrel from the stator side of the drive motor are equal during the start and stop of the compressor, and the total gravity of the compressor rotor, acting vertically in opposite directions; during the compressor start-up, the drive electric motor is overexcited, for example, by turning on the stator winding by a smaller number of working turns by means of additional tap ends from the stator winding and the drive motor operating mode switch, and at the time the compressor stops, a constant is fed into the stator winding current from an external regulated source.

 This is also achieved by the fact that the barrel of the rotor of the driving high-frequency electric motor is made with an explicit pole massive magnetic circuit and a short-circuited winding at the same time integrally with the compressor rotor shaft of ferromagnetic material with an axial length greater than the axial length of the stator magnetic circuit; on the outer surface of the rotor barrel facing the inner surface of the stator magnetic circuit, blind pockets are made in an amount equal to the number of poles by the side of the winding, the axial length of which is equal to the axial length of the stator magnetic circuit, and the ratio of the circumferential length to the stator pole division is 0.4-0 , 6.

 This is achieved by the fact that the rotor barrel is additionally equipped with a short-circuited winding made of non-magnetic material with low electrical resistance, for example, by casting with copper, the rods of which are located in the clearly expressed poles of the magnetic circuit, and the short-circuiting rings are located in ring grooves made from the end sides of the rotor barrel.

 To reduce gas-dynamic losses and noise, the edges of the clearly visible poles of the magnetic circuit of the rotor barrel of the drive high-frequency electric motor running in the direction of rotation are profiled so that these edges of the explicit poles provide the least possible resistance to gas flow during rotation of the compressor rotor.

 Comparative analysis with the prototype shows that the proposed centrifugal cryogenic compressor is characterized in that the inner surface of the stator magnetic circuit and the outer surface of the magnetic barrel of the rotor of the drive electric motor are conical with the same taper angle, to ensure the minimum value of which the drive motor is overexcited during the start and stop of the compressor.

The rotor barrel, depending on the required power and speed of the compressor is performed in various ways:
with charged magnetic core and short-circuit winding (similar to the prototype);
with a clearly polar massive magnetic circuit and a short-circuited winding made integrally with the compressor rotor shaft of ferromagnetic material with an axial length greater than the axial length of the stator magnetic circuit; clearly defined poles and a short-circuited winding are formed using blind pockets, the axial length of which is equal to the axial length of the stator magnetic circuit, and the ratio of the length along the outer circumference to the pole division of the stator is 0.4-0.6;
with an open-ended massive magnetic circuit according to claim 2 and an additional short-circuited winding made of non-magnetic material with low electrical resistance, the rods of which are located in the clearly defined poles of the magnetic circuit, and the short-circuiting rings are located in ring recesses made from the end faces of the rotor barrel;
with an explicitly polar massive magnetic circuit according to claim 2 and 3, which run in the direction of rotation of the edge of the poles of which are profiled to minimize their resistance to gas flow during rotation of the compressor rotor.

 Figure 1 shows a section of a centrifugal cryogenic compressor showing the performance of the rotor barrel of the drive motor in two versions; with a charged magnetic circuit and a short-circuited winding ("W"); with an explicit pole massive magnetic circuit with an additional short-circuited winding and profiled pole edges ("M"); figure 2 cuts aa and bb when performing the barrel of the rotor with an explicit pole magnetic circuit with an additional short-circuited winding and profiled edges of the poles ("M"); figure 3 is a block diagram of a centrifugal compressor electric drive composed of a power source (frequency converter) and a switch mode of operation of the compressor drive motor; figure 4, the qualitative dependence of the moment-speed in the case of the execution of the barrel of the rotor with an explicit pole massive magnetic circuit is integral with the compressor rotor shaft: 1 with a ferromagnetic short-circuited winding without additional copper short-circuited winding; 2 with an additional copper short-circuited winding without a ferromagnetic short-circuited winding; 3 ferromagnetic short-circuited winding and additional copper short-circuited winding (the resulting characteristic "moment-speed" of the drive motor); 4, 5, 6 and 7 family of compressor load characteristics.

_рккраями и ферромагнитная короткозамкнутая обмотка, стержнями которой являются явновыраженные полюса 10, а короткозамыкающими кольцами торцовые ферромагнитные части 11 (фиг.2, Б-Б) бочки ротора. Для улучшения пусковых свойств компрессора бочка ротора "М" оснащена дополнительной короткозамкнутой обмоткой, выполненной из немагнитного материала с малым электрическим сопротивлением, например, посредством заливки медью, стержни 12 (фиг.2, А-А) которой расположены в явновыраженных полюсах 10, а короткозамыкающие кольца 13 (фиг. 1) размещены в кольцевых выточках с торцовых сторон бочки ротора. Помимо бочки ротора "М" на валу 7 установлены рабочее колесо компрессора 14 и пята 15 осевой газодинамической опоры, в верхнюю часть которой встроен якорь 16 датчика скорости 17 с выводными концами 18, идущими к регистрирующему частоту вращения ротора компрессора прибору (на фиг.1 последний не показан). Датчик скорости 17 установлен на внутренней стороне крышки 19, крепящейся к корпусу 1. Там же установлен наружный подпятник 20 осевой газодинамической опоры ротора компрессора.The proposed centrifugal cryogenic compressor is considered on the example of a microcompressor, the barrel of the rotor of the drive motor of which is made with an explicit pole massive magnetic circuit integrally with the compressor rotor shaft. The compressor (FIG. 1) comprises a housing 1, in which the shaft 7 of the compressor rotor is installed in a vertical position by means of bearing shields 2 and 3 on the radial gas-dynamic bearings 4, 5 and the inner thrust plate 6 of the axial gas-dynamic bearing. Directly on the shaft 7 is the barrel of the rotor "M" of the drive motor with an explicit pole conical massive magnetic circuit 8 (Fig. 2), made integrally with the shaft 7, and two deaf pockets 9 (Fig. 2, A-A) with which two distinct poles 10 with compressor rotor profiled in the direction of rotation

_pk edges and a ferromagnetic short-circuited winding, the rods of which are clearly defined poles 10, and short-circuit rings end ferromagnetic parts 11 (figure 2, BB) of the rotor barrel. To improve the starting properties of the compressor, the rotor barrel "M" is equipped with an additional short-circuited winding made of non-magnetic material with low electrical resistance, for example, by casting copper, the rods 12 (figure 2, A-A) of which are located in explicit poles 10, and short-circuit rings 13 (Fig. 1) are placed in annular recesses from the end faces of the rotor barrel. In addition to the rotor barrel “M”, the impeller 14 of the compressor 14 and the heel 15 of the axial gas-dynamic support are installed on the shaft 7, in the upper part of which an armature 16 of the speed sensor 17 with output ends 18 connected to the instrument registering the rotor speed of the compressor is integrated (Fig. 1 last not shown). The speed sensor 17 is installed on the inner side of the cover 19, which is attached to the housing 1. There is also installed an outer thrust bearing 20 of the axial gas-dynamic support of the compressor rotor.

 In the housing 1 (Fig. 1), a compressor drive motor stator is installed, consisting of a charged magnetic core 21 with an angle of taper of the inner surface equal to the taper angle of the outer surface of the rotor barrel "M" and located in the grooves of the magnetic circuit 21 of the three-phase winding 22, the terminal ends C1-C2-C3 -C4-C5-C6 (Fig. 3) which are connected via a mode switch of the drive motor 23 to the frequency converter 24, for example, of an electric machine type.

 For forced cooling of the stator of the drive motor in the housing 1 there is a screw channel 25, through which a cooling agent (liquid or gas) circulates. The input and output of the cooling agent in figure 1 are indicated by arrows.

 From the side of the impeller 14 (Fig. 1), a compressor part 26 is installed on the housing 1, which includes a diffuser 27 and a spiral scroll 28. The inlet and outlet of the working gas, for example, helium or nitrogen, are indicated by arrows in Fig. 1.

, приложенной к бочке ротора со стороны статора приводного двигателя, и суммарной силы тяжести ротора компрессора

.The compressor operates as follows. Include a forced cooling system for the stator of the drive motor (figure 1). At the inlet of the flow part of the compressor 26 serves a working gas, for example, helium or nitrogen. Start the machine frequency converter 24 (figure 3). The mode switch 23 (figure 3) from the neutral position is included in the "Start" position. In this case, the output ends C4-C5-C6 of the three-phase winding 22 of the drive motor are connected to the output of the frequency converter 24. Due to the increase in working magnetic flux due to overexcitation of the drive motor from the frequency converter 24 (Fig. 3) and a small taper angle (1-2 ^° ) of the inner surface of the stator magnetic circuit 21 (Fig. 1) and the outer surface of the massive magnetic circuit 8 (Fig. 2) the barrel of the rotor "M" (figure 1), there is an equilibrium of electromagnetic force

applied to the rotor barrel from the stator side of the drive motor, and the total gravity of the compressor rotor

.

The resulting zero-gravity state of the compressor rotor leads to the unloading of the axial gas-dynamic support, consisting of an inner thrust bearing 6 and the heel 15 (Fig. 1), for a period of time during which the compressor rotor under the influence of the electromagnetic moment of the drive motor (Fig. 4, dependence "moment - speed "3) is accelerated from a stationary state to a steady rotation speed equal to the synchronous rotation speed n _{from the} magnetic field created in the working gate δ (Fig. 1) as a result of the flow of alternating currents with a frequency f _output converter 24 in a three-phase winding 22 (figure 3).

и приобретшая газодинамические свойства осевая опора, состоящая из подпятника 6 и пяты 15, нагружается силой, равной разности сил

-

(фиг.1).At the moment the compressor reaches the synchronous speed n _c, by the command received from the recording device associated with the speed sensor 17 (Fig. 1), the operating mode switch 23 (Fig. 3) is put into the "Work" position, in which as a result of the connection to the output of the frequency converter 24 of the output ends C1-C2-C3 of the three-phase winding 22, the working magnetic flux in the air gap δ of the drive motor (Fig. 1) is reduced to a nominal value corresponding to the values of the output voltage U _o and output frequency f _{o of the} converter 2 4 (FIG. 3), the value of the electromagnetic force decreases

and the axial support, which has acquired gas-dynamic properties, consisting of a thrust bearing 6 and a heel 15, is loaded with a force equal to the difference of forces

-

(figure 1).

As follows from figure 4, the compressor drive motor during start-up to a sub-synchronous speed n _nc behaves like a high-frequency asynchronous motor with two short-circuited windings on the rotor barrel: a ferromagnetic winding made integral with the compressor rotor shaft (starting properties of the engine with such the windings are illustrated by the torque-speed relationship 1) and an additional copper winding (the starting properties of an engine with such a winding are illustrated by the torque-speed relationship 2). The characteristic "moment-speed" 3 of the drive motor is obtained by summing the electromagnetic moments arising on the compressor shaft from the interaction of currents flowing in each of the above short-circuited windings with a working magnetic flux in the gap δ (Fig. 1).

где θ угловое положение явновыраженных полюсов 10 магнитопровода ротора 8 (фиг.2) относительно полюсов магнитного поля статора;
W_к магнитная коэнергия.When the compressor rotor reaches the sub-synchronous speed n _{nc, the} drive motor starts to behave as a synchronous reactive one, since a reactive moment appears on its shaft, which is equal to [3] with constant current in the stator winding
M _p =

where θ is the angular position of the pronounced poles 10 of the magnetic circuit of the rotor 8 (Fig.2) relative to the poles of the magnetic field of the stator;
W _to magnetic co-energy.

 At point A (Fig. 4), using the reactive moment, the compressor drive motor switches from asynchronous mode to steady-state synchronous mode, in which, after switching the mode switch 23 (Fig. 3) to the "Work" position, the electromagnetic moment on the compressor shaft is balanced at point B external braking torque corresponding to the rated load characteristic of compressor 4 (in Fig. 4, the transition from point A to point B is indicated by arrows), from the side of the impeller of compressor 14 (Fig. 1).

Using characteristics 5, 6, 7 in FIG. 4 illustrates the starting properties of the drive motor and its ability to absorb the load from the side of the compressor impeller; 5 load characteristic, in which the drive motor is still able to switch from asynchronous mode (point A) to synchronous mode (point B); 6 is the ultimate load characteristic at which the drive motor goes out of synchronism (point G, M = M _out. ) And cannot enter synchronism, because when the compressor is restarted, the compressor rotor does not reach the sub-synchronous speed n _nc (point D); 7 load characteristic, in which the drive motor is able to switch from asynchronous mode (point E) to synchronous mode (point G) in the absence of an additional copper short-circuited winding on its rotor barrel.

With the compressor rotor reaching a steady-state synchronous speed n _c , its heating from the side of the rotor barrel "M" (Fig. 1) of the drive motor practically ceases, since when operating in synchronous mode from an electric machine frequency converter 34 (Fig. 3) with a sinusoidal output shape voltage U _o minimized Joule losses in the ferromagnetic and additional copper short-circuited windings.

 Due to the increased stiffness of the shaft 7 (Fig. 1) at the location of the massive rotor of the drive motor (Fig. 1, "M"), the frequency of natural transverse vibrations increases significantly compared to the embodiment of the compressor with a charge rotor (Fig. 1, "Ш") the compressor rotor and the permissible value of its maximum operating speed.

краями обеспечивает снижение газодинамических потерь и шума, поскольку при работе компрессора в карманах 9 образуется вакуум, а на спрофилированных краях полюсов 10 отсутствует турбулентность в набегающем на них газовом потоке.The presence of blind pockets 9 (figure 2, aa) and clearly defined poles 10 with profiled in the direction of rotation

the edges provides a reduction in gas-dynamic losses and noise, since during the operation of the compressor in the pockets 9 a vacuum is generated, and at the profiled edges of the poles 10 there is no turbulence in the incident gas flow.

 To stop the compressor, the operating mode switch 23 (Fig. 3) is switched to the neutral position, in which the three-phase winding 22 is disconnected from the electric machine frequency converter 24 and then connected to an adjustable DC source, for example, an adjustable two-half-wave semiconductor rectifier (in Fig. 3, the last shown).

и

(фиг. 1). При этом происходит интенсивное электродинамическое торможение приводного электродвигателя до полной остановки ротора компрессора в строго определенной вертикальной плоскости пространства, определяемой положением явновыраженных полюсов бочки ротора "М" (фиг.1) относительно неподвижных полюсов магнитного поля, образованного в рабочем зазоре δ путем пропускания постоянного тока по статорной обмотке. Затем величина постоянного тока в обмотке 22 и соответствующая этому току электромагнитная сила

плавно снижаются до нуля, в результате чего обеспечивается безударная посадка невращающегося ротора компрессора в исходное (перед запуском) положение на внутренний подпятник 6 осевой газодинамической опоры (фиг.1).At the initial moment, a constant current of such magnitude is passed through the winding 22 (Fig. 3) that maintains a balance of forces

and

(Fig. 1). In this case, intense electrodynamic braking of the drive motor to a complete stop of the compressor rotor in a strictly defined vertical plane of space, determined by the position of the clearly visible poles of the barrel of the rotor "M" (Fig. 1) relative to the stationary poles of the magnetic field formed in the working gap δ by passing direct current across stator winding. Then the magnitude of the direct current in the winding 22 and the corresponding electromagnetic current

gradually decrease to zero, resulting in a shock-free landing of the non-rotating compressor rotor in its original (before starting) position on the inner thrust plate 6 of the axial gas-dynamic support (Fig. 1).

 Upon completion of the above operations, the winding 22 (Fig. 3) is disconnected from the direct current source, the supply of working gas to the inlet of the compressor 26 (Fig. 1) stops, and the forced cooling system of the stator of the drive motor is turned off.

The technical and economic effect of the use of the invention consists of the following main components:
reducing approximately two to three times the costs associated with the replacement of axial gas-dynamic supports and compressor repairs;
reduction of approximately 25-30% of the complexity of manufacturing and dynamic balancing of the compressor rotor;
excluding expenses associated with the acquisition, installation and operation of an individual power source (frequency converter) of the compressor drive motor.

Claims (3)

 1. CENTRIFUGAL CRYOGENIC COMPRESSOR, comprising an impeller, diffuser, spiral scroll and a high-frequency drive electric motor, the rotor barrel of which is located on a shaft that is integrated with the impeller and mounted vertically on radial and axial gas-dynamic bearings by means of bearing shields in a single housing in which the drive stator is located electric motor and its forced cooling system, characterized in that the barrel of the rotor of the drive high-frequency electric motor is made with a clearly polar m an integral magnetic circuit and a short-circuited winding integrally with a compressor rotor shaft of ferromagnetic material with an axial length greater than the axial length of the stator magnetic circuit, blind pockets are made on the outer surface of the rotor barrel facing the inner surface of the magnetic circuit of the stator, equal to the number of poles of the stator winding, the axial length of which is equal to the axial length of the stator magnetic circuit, and the ratio of the length along the outer circumference to the pole division of the stator is 0.4 0.6.  2. The compressor according to claim 1, characterized in that the rotor barrel of the high-frequency drive electric motor is additionally equipped with a short-circuited winding made of non-magnetic material with low electrical resistance, for example, by pouring copper, the rods of which are located in the clearly expressed poles of the magnetic circuit, and the short-circuit rings are placed in ring grooves made from the end faces of the rotor barrel.  3. The compressor according to claim 2, characterized in that the barrels of the rotor of the drive high-frequency electric motor running along the edges of the clearly marked poles of the magnetic circuit are profiled, for example, by rounding the edges so as to provide the smallest possible resistance to gas flow during rotation of the compressor rotor.

Images