EP3775567B1 - Method for controlling at least one radial blower in a cooling system, and radial blower - Google Patents

Description

The invention relates to a method for controlling at least one radial fan in a refrigeration system and a refrigeration system.

From the DE 10 2010 001 538 A1 a radial fan for a gas laser is known. Such a radial fan comprises between a first and second radial bearing, in particular a radial gas bearing, a motor which is formed by a rotor and a stator. An impeller is provided on a shaft in the housing of the radial fan, which is driven in rotation by the motor, in order to circulate the laser gas of a laser assembly. This centrifugal fan further comprises an axial gas bearing which is positioned remotely from the impeller, with the motor having the first and second radial bearings arranged directly adjacent thereto being positioned between the axial gas bearing and the impeller. A pressure medium is supplied to the radial gas bearings and the axial gas bearing through channels in the housing in order to form a hydrodynamic bearing.

Such radial fans are also suitable for integration into a refrigeration system. During operation of the refrigeration system, in particular the radial fan or fans, it is necessary for the operating points of the radial fans to be monitored. The operating points of such a refrigeration system are constantly changing due to a continuously changing ambient temperature, the amount of heat to be cooled and the required temperature of the refrigeration system. These changes affect the centrifugal fans. Either the centrifugal fans can be overloaded and thus damaged, or the operating range is not optimally utilized.

From the DE 10 2013 102 648 A1 an electric motor with function monitoring of the motor bearings is known. This electric motor comprises a stator with a rotor which is mounted in bearing arrangements so that it can rotate relative to it, as well as a motor housing and a vibration sensor for recording vibrations occurring in the electric motor Vibrations caused by malfunctions in the bearing assemblies.

From the DE 10 2006 011 613 A1 a single-stage centrifugal pump with an axial thrust compensation device is known, with an impeller connected to a shaft being arranged to rotate in the housing of the centrifugal pump. At least one split ring seal arranged between the impeller and the housing forms a relief chamber, with the relief chamber being connected to the pressure region of the centrifugal pump by a pressure-transmitting connection. A shaft seal is arranged between the shaft and the housing. This shaft is provided with at least one roller bearing that absorbs axial forces.

From the DE 43 27 506 A1 a turbo vacuum pump is known. This has a housing which is provided with a suction opening and a delivery opening. An evacuation pump arranged in the housing compresses the gas sucked in through the suction opening, which gas is discharged through the delivery opening. A motor is also provided to drive the evacuation pump.

From the KR 2001 0081670 A a turbo compressor is known. This turbo compressor includes a housing with a cover, in which a rotor with an impeller arranged on the face side is positioned in a rotating manner. A vibration sensor assigned to the blade ends of the impeller is provided in the cover in order to monitor the blade ends for possible blade breakage.

From the KR 2016 0087299 A a turbo compressor is also known. This turbocompressor includes a shaft which is rotatably supported by two radial foil air bearings spaced apart from one another. An axial film air bearing is also provided. Vibrations are transmitted to a vibration sensor provided on the outer circumference of the metal plate via a metal plate, which is assigned to the axial film air bearing and the radial film air bearing adjacent thereto.

The invention is based on the object of proposing a method for controlling at least one radial fan in a refrigeration system and a radial fan, whereby a maximum energy efficiency of the radial fan or fans and thus of the refrigeration system is achieved.

This object is achieved by a method for controlling at least one centrifugal fan in a refrigeration system, in which the centrifugal fan comprises a housing in which a shaft is rotatably mounted, which at one end accommodates at least one impeller of a compressor that is attached to the housing and at least one radial bearing and at least one thrust gas bearing by which the shaft is rotatably supported in the housing and has a motor driven by a rotor and a stator, the motor being provided between the first and second radial bearings, a vibrometer for Shaft is aligned and another vibrometer is assigned to a front end of the shaft and positioned in the axis of rotation of the shaft and with the vibrometers, which are assigned to the shaft, operating points of the shaft are recorded and forwarded to a controller for determining an operating state of the radial fan. By monitoring the shaft, by which the at least one impeller of the radial fan is driven and the cooling is achieved on the basis of the pressure medium or refrigerant accelerated and/or compressed by the at least one impeller, the current operating state of the radial fan can be recorded and a critical operating state can also be monitored at the same time become. Due to the direct monitoring of the shaft, a corresponding control can be made possible based on the currently recorded operating situation in order to prevent a critical operating state or a limit value of the radial fan from being exceeded on the one hand and on the other hand to control an optimal efficiency value.

A critical limit value is preferably detected by the control of the radial fan and exceeding the limit value is prevented by the control of the radial fan itself or optionally by the control of the refrigeration system. The controller can do this intervene to limit or reduce the speed of the motor in terms of its control in order to drive the shaft rotating below the critical limit value.

Furthermore, with several radial fans provided in the refrigeration system, operating points are preferably detected by the respective vibrometer, the respective operating points of the radial fans are compared with one another and adjusted to the maximum energy efficiency of the respective radial fan. Such control and monitoring has the advantage that the respective controllers for the radial fans independently carry out a check to achieve an energy efficiency maximum, i.e. that each radial fan can work independently of one another in its own energy efficiency maximum and thus optimal overall efficiency of the refrigeration system is achieved. This means that a network of several radial fans can be operated in a controlled energy minimum for the refrigeration system. Irrespective of this, the self-protection function of each individual radial fan is preferably maintained with regard to its critical limit value.

If there are several centrifugal fans in the refrigeration system, these are preferably connected to one another in a network using data lines. In particular, a bus system is provided. This allows rapid communication and mutual exchange of the individual operating points.

Furthermore, if there are several radial fans in the refrigeration system, one of the radial fans is preferably operated as the master and the other radial fans are operated as slaves. As a result, the other radial fans operated as slaves are switched on by the master on the basis of its existing measured values in such a way that this network of radial fans works in a regulated energy minimum.

A further advantageous embodiment of the method provides that the signals recorded by the vibrometer are continuously evaluated. This allows full control and monitoring to be achieved.

The object on which the invention is based is also achieved by a radial fan, which comprises a housing in which a shaft is rotatably mounted, which at one end accommodates at least one impeller of a compressor which is attached to the housing and at least one radial bearing and at least one Has axial gas bearing, through which the shaft is rotatably supported on the housing, the shaft being driven by a motor having a rotor and stator, at least one vibrometer being provided which is associated with the shaft. By determining the operating points directly on the shaft, an exact detection of an operating state of the radial fan can be achieved. As a result, critical operating points or exceeding the limit values of the bearings and/or the radial fan can be recognized immediately and counteracted. The data recorded by the vibrometer are forwarded to the controller for the centrifugal fan.

The vibrometer is aligned radially to the shaft of the centrifugal fan. As a result, vibrations occurring during rotation of the shaft can be determined. A critical operating state of the shaft can be defined via the frequency and/or the amplitude of a vibrometer signal.

A further advantageous embodiment of the radial fan provides that the at least one vibrometer is assigned to the shaft between the rotor of the motor and the radial bearing or axial gas bearing provided adjacent thereto. As a result, critical operating states can be detected immediately adjacent to the generation of the rotational movement of the shaft.

Furthermore, a vibrometer is provided at a front end of the shaft. As a result, additional monitoring or a further parameter can be recorded in order to evaluate critical operating states.

The at least one vibrometer is preferably positioned in a housing opening so that it is assigned directly to the shaft. The vibrometer is preferably provided in the housing opening so as to be pressure-tight. As a result, on the one hand, the radial gas bearing and/or axial gas bearing arranged adjacent thereto can be driven hydrodynamically, and on the other hand, direct detection of the shaft is made possible.

The invention and other advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings.

• Figur 1 eine schematische Schnittansicht eines Radialgebläses,
• Figur 2 eine schematisch vergrößerte Ansicht eines Axialgaslagers benachbart zum Verdichter, und
• Figur 3 eine schematische Ansicht einer Kälteanlage.

Show it:

• figure 1 a schematic sectional view of a radial fan,
• figure 2 a schematic enlarged view of a thrust gas bearing adjacent to the compressor, and
• figure 3 a schematic view of a refrigeration system.

In figure 1 a schematic sectional view of a radial fan 11 is shown. This radial fan 11 radially accelerates a refrigerant from at least one impeller 16, 26 of a compressor 27 and directs it into lines of a refrigeration system 1, which is shown, for example, in figure 3 is shown.

This radial fan 11 radially accelerates the cooling medium from at least one impeller 16, 26 of a compressor 27 and compresses it into the gas pressure line 75 ( figure 3 ) the compression side of the refrigeration system 1 out. The impeller 16, 26 is seated on a shaft 17 which is driven by a motor 20 in the central region of the motor housing 21. This motor 20 consists of a rotor 18 connected to the shaft 17 and a stator 19 fastened to the motor housing 21. The area which is arranged outside the impeller 16, 26 viewed from the shaft 17 forms the pressure side of the fan. A radial bearing 22, 23, in particular a lower radial gas bearing 22 and an upper radial gas bearing 23, are arranged in the upper and lower region of the shaft 17, respectively. These radial gas bearings 22, 23 include stationary bearing surfaces referred to as the radial stator 24. Furthermore, the shaft 17 in the area of the radial gas bearings 22, 23 rotating bearing surfaces 25. The pressure medium for the gas bearings is advantageously the cooling medium. An axial gas bearing 31 is provided between the impeller 16 of the compressor 27 and the lower radial gas bearing 22 . This axial gas bearing 31 comprises a rotating disk 32 and axial stators 34 adjacent to the disk 32 or on its upper side and underside, each of which has stationary bearing surfaces 35 . Disc 32 includes rotating bearing surfaces 36 opposed to stationary bearing surface 35 . Between the axial gas bearing 31 and the impeller 16, a duct 41, which is connected to the compression side of the refrigeration system 1, runs under the impeller 16. The pressurized cooling medium is guided in a gaseous state under the impeller 16 through this duct 41 in order to counteract the axial gas bearing 31 to protect against the entry of particles.

The rotating bearing surfaces 25 of the radial gas bearing 22 and/or the rotating bearing surfaces 36 of the axial gas laser 31 preferably have surfaces that include grooves. Herringbone patterns are preferably provided. Such grooves or surface depressions are preferably introduced using an ultra-short pulse laser, in particular a picosecond laser. This enables processing with very short processing times. In addition, this processing step does not require any post-processing and meets the high requirements for precise design. The very short laser pulses in the microsecond range result in a direct sublimation of the material. As a result, these grooves can be produced without reworking, in particular without burrs. In particular, an ion beam method is used. Alternatively, micro-machining can also be provided.

The radial fan 11 is aligned vertically in an installation situation in the refrigeration system 1 . The compressor 27 is aligned downwards and the motor housing 21 is aligned vertically upwards. The radial fan 11 can advantageously be arranged directly above a flooded evaporator 66 so that any condensate that may occur when the refrigeration system 1 is at a standstill flows back down into the evaporator 66 .

In figure 2 a schematically enlarged view of the axial gas bearing 31 and a connection of the compressor 27 to the motor housing 21 of the radial fan 11 is shown. The compressor 27 with its housing 52 is connected to the motor housing 21 of the radial fan 11 without using a labyrinth seal or the like. The supply of the pressurized cooling medium via the channel 41 is used to prevent particles from entering the axial gas bearing 31 . The axial gas bearing 31 itself has such a narrow gap between the bearing surfaces 35 of the stator 34 and the bearing surfaces 36 of the rotating disk 32 that the axial gas bearing 31 itself forms a seal between a rotor chamber 46 in the housing 21 and a gas chamber 49 in the compressor 27 . Seen in the radial direction, the rotor space 46 is formed between a through bore 47 in the motor housing 21 and the shaft 17 mounted therein. The gas space 49 is formed between a housing section 51 of the motor housing 21 or housing 52 of the compressor 27 and the impeller 16 . A housing 52 of the compressor 27 preferably encompasses the housing section 51 and is firmly connected to the motor housing 21 outside of this housing section 51 .

A pressure connection 54 for the pressurized cooling medium, which is supplied to the channel 41 , is provided on the motor housing 21 . In an area in which the rotor space 46 and the gas space 49 adjoin one another, the cooling medium flows mainly in the direction of the gas space 49;

A seal between a pressure side of the compressor 27 and the motor housing 21 can thus be achieved by this arrangement. The compressor 27 is preferably designed as a multi-stage compressor or turbo compressor. A first stage forms the impeller 26, and the second stage forms the impeller 16. In particular, the seal between the pressure side of the second stage or the impeller 16 of the compressor 27 and the motor housing 21 of the Radial fan 11 done. In this way, a lower pressure can be set in the motor housing than on the pressure side of the compressor 27, as a result of which condensation of the cooling medium in the radial bearings 22, 23 is prevented. Furthermore, the pressure connection 54 can preferably have a filter element. This serves to ensure that no particles get into the compressor 27 and/or the axial gas bearing 31 .

This radial fan 11 can also have a heating device 56 in the area of the axial gas bearing 31 or adjacent to an axial stator 34 or between the two axial stators 34 . Such a heating device 56 serves to heat the axial gas bearing 31 to a temperature which is above the dew point of the cooling medium when the pressure is applied. This can prevent condensation of the cooling medium. Such a heating device 56 can be designed as an electrically driven heater, such as by a resistance heating element or a PTC element.

A vibrometer 61 , which is assigned to the shaft 17 , is preferably provided between the motor 20 and the lower radial gas bearing 22 . This vibrometer 61 is a measuring device for quantifying mechanical vibrations. Such a vibrometer 61 can be used to measure vibration frequency and vibration amplitude. For example, a so-called laser Doppler vibrometer can be used. This vibrometer 61 is inserted into a housing opening 62 of the motor housing 21 and is preferably arranged in a pressure-tight manner. This can be done by means of an O-ring seal 63, for example. As a result, the pressure in the rotor space 46 for the hydrodynamic operation of the radial and axial gas bearings 22, 23, 31 can be maintained. A measuring surface of the vibrometer 61 is aligned tangentially to the peripheral surface of the shaft 17 . In this case, the measuring surface can advantageously also lie on a bearing sleeve surrounding a radial gas bearing 22 , 23 . During the operation of the radial fan 11, the frequency and the amplitude can be continuously detected by the vibrometer 61 and passed on to a controller 71 of the radial fan or the refrigeration system. As a result, the current operating point or the operating points of the radial fan 11 prevailing during the cooling can be determined. In addition, a comparison with a limit value can be carried out at the same time. Such a limit value can be a critical operating state in which damage to the bearing or bearings or other components of the radial fan is to be expected. In particular to the effect that the shaft 17 in the motor housing 21 or the impellers 16, 26 in the compressor 27 are blocked.

Alternatively, a vibrometer 61 can also be provided between the motor 20 and the upper radial gas bearing 23 .

A further vibrometer 64 can be provided for additional monitoring of operating states of the radial fan 11, which is positioned in the axis of rotation of the shaft 17 and points to a front end of the shaft 17 with respect to a measuring surface. This also allows eccentricities in the rotating drive of the shaft 17 to be evaluated.

This additional vibrometer 64 is again positioned in a media-tight manner in a housing cover 65 in analogy to the vibrometer 61 .

In figure 3 a schematic view of a refrigeration system 1 is shown. This refrigeration system 1 is only an example and works in particular according to the principle of evaporative cooling. A refrigerant is located in an evaporator 66 . The energy or heat required to evaporate the refrigerant is extracted from the environment. The refrigerant absorbs this energy and turns into a gaseous state. The refrigerant in the gaseous state is fed via a line 67 to one or, according to the exemplary embodiment, to a plurality of radial fans 11 which each have a compressor 27 . The refrigerant is compressed to a high pressure and high temperature, which is higher than the inlet pressure and the inlet temperature before the compressor 11, respectively. The refrigerant is then fed to a liquefier or a condenser 68 . In this condenser, the refrigerant liquefied by cooling. The refrigerant is then passed through a throttle element, in particular an expansion valve 69, at high pressure. The refrigerant expands or is converted to low pressure and can be supplied to the evaporator 66 in the liquid state in order in turn to extract the heat from the environment. The refrigeration system 1 is a closed refrigeration circuit.

To control the individual radial fans 11, a controller 71 of the refrigeration system 1 is provided, by means of which the individual radial fans 11 can be controlled. The radial fans 11 are preferably each connected to the controller 71 by a bus system 72 . The compressor control or a radial fan control preferably works according to the master-slave principle. The master function is assigned to one of the radial fans 11 . The other radial fans 11 are operated as so-called slaves in the network. The controller 71 acquires the measured values of the sensors of the radial fan from the master. On the basis of these recorded or existing measured values, the further radial fans are switched on in each case, so that the network of radial fans 11 is operated at a regulated energy minimum. A protective function of each individual radial fan 11 is retained.

In order to achieve a safe operating range for the radial fan 11 in the refrigeration system 1, control and regulation algorithms are used in the controller 71 for controlling the radial fan 11 in such a way that no critical operating point can arise for the respective radial fan 11. Furthermore, the radial fans 11 can also communicate with one another via the bus system 72 in order to independently control the achievement of an energy efficiency maximum based on the measured values present in the radial fan 11 itself, in particular based on the measured values present in the master radial fan 11.

Claims (9)

1. A method for controlling at least one radial fan (11) in a cooling system (1), in which the radial fan (11) comprises a housing (21) in which a shaft (17) is rotatably mounted which, on one end, receives at least one impeller (16, 26) of a compressor (27), which is fixed on the housing (21), and the housing (21) comprises at least one radial bearing (22, 23) and at least one axial gas bearing (31), by means of which the shaft (17) is rotatably mounted in the housing (21), and an engine (20) driven by a rotor (18) and stator (19), said engine driving the shaft (17), characterized in, that a vibrometer (61) is aligned radially to the shaft (17) and a further vibrometer (64) is allocated to an end-face of the shaft (17) and positioned in the rotational axis of the shaft (17) and that operating points of the shaft (17) are detected by the vibrometers (61, 64), which are allocated to the shaft (17), and are forwarded on to a controller (71) for ascertaining an operating state of the radial fan (11).
2. The method of claim 1, characterized in, that a critical threshold value is recognised by the controller (71) of the radial fan (11), and exceeding the threshold values is prevented by the controller (71) of the radial fan (11) itself or alternatively by the controller (71) of a cooling system.
3. The method of claim 1 or 2, characterized in, that the operating points are detected by several radial fans (11) provided in the cooling system by means of the respective at least one vibrometer (61, 64), and the respective operating points are compared to one another and set to the maximum energy efficiency of the respective radial fan (11).
4. The method of any one of the preceding claims, characterized in, that several radial fans (11) are connected to one another in the cooling system with a network of data lines of a bus system for exchanging data.
5. The method of any one of claim 3 or 4, characterized in, that one of the radial fans (11) is operated as a master and the further radial fans (11) as slaves.
6. The method of any one of the preceding claims, characterized in, that the signals detected by the vibrometer (61, 64) are permanently evaluated, and the respective radial fan (11) is constantly monitored.
7. A radial fan for a cooling system (1), comprising:

   - a housing (21) in which a shaft (17) is rotatably mounted which, on one end, receives at least one impeller (16, 26) of a compressor (27), which is fixed on the housing (21),

   - at least one radial bearing (22, 23) and having at least one axial gas bearing (31) by means of which the shaft (17) is rotatably mounted in the housing (21),

   - an engine (20) driven by a rotor (18) and a stator (19), said engine driving the shaft (17),

   - at least one vibrometer (61, 64) which is allocated to the shaft (17), characterized in,

   - that the at least one vibrometer (61) is aligned radially to the shaft (17),

   - that a further vibrometer (64) is allocated to the shaft (17) to an end-face of the shaft (17) and positioned in the rotational axis of the shaft (17).
8. The radial fan of claim 7, characterized in, that the at least one vibrometer (61) is allocated to the shaft (17) between the rotor (18) of the engine (20) and the radial bearing (22, 23) or axial gas bearing (31) arranged adjacently thereto.
9. The radial fan according to claim 7 or 8, wherein the at least one vibrometer (61, 64) is positioned in a housing opening (62) of the housing (21) and is provided in the housing opening (62) in a pressure medium-tight manner.

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