Anode recirculation blower comprising an integrated sensor

Abstract

The invention relates to a side channel compressor (1) for a fuel cell system (31) for delivering and / or compressing a gaseous medium, in particular hydrogen, said side channel compressor comprising: a housing (3) and a drive (6), the housing (3) having a housing upper part (7) and a housing lower part (8); a compressor chamber (30) which extends peripherally in the housing (3) about an axis of rotation (4) and has at least one peripheral side channel (19, 21); a compressor wheel (2) which is located in the housing (3) and which is rotatably arranged about the axis of rotation (4) and is driven by the drive (6), said compressor wheel (2), in the region of the compressor chamber (30), comprising blades (5) arranged on the periphery of the compressor wheel; and a gas inlet opening (14) and a gas outlet opening (16) which are each formed on the housing (3) and which are fluidically connected to one another via the compressor chamber (30), in particular the at least one side channel (19, 21). According to the invention, at least one sensor (18) is located in the housing (3) of the side channel compressor (1), wherein the measured variable of the wall shear stress is determined by means of the sensor (18), in particular by means of a surface hot-film method, and wherein the sensor (18) is located in an interrupter region (15) of the compressor chamber (30) of the side channel compressor (1). The invention also relates to: a fuel cell system (31); a method for operating a side channel compressor (1) and / or a fuel cell system (31); and a method for manufacturing a combined measuring channel / cover assembly (33).

Description

[0001] Description

[0002] title

[0003] Anode recirculation fan with integrated sensor

[0004] State of the art

[0005] The present invention relates to a side channel compressor for a fuel cell system for conveying and / or compressing a gaseous medium, in particular hydrogen, which is intended in particular for use in vehicles with a fuel cell drive. Furthermore, the present invention relates to a fuel cell system, a method for operating a side channel compressor and / or a fuel cell system, and a method for producing a combined measuring channel-cover assembly.

[0006] In the automotive sector, alongside liquid fuels, gaseous fuels will also play an increasingly important role in the future. Hydrogen gas flows must be controlled, particularly in fuel cell-powered vehicles. The gas flows are no longer controlled discontinuously, as with liquid fuel injection, but rather the gas is taken from at least one high-pressure tank and fed to an ejector unit via an inlet line of a medium-pressure line system. This ejector unit feeds the gas to a fuel cell via a connecting line of a low-pressure line system. After the gas has flowed through a fuel cell, it is fed back to the ejector unit via a return line. A side channel compressor can be interposed to support the gas recirculation in terms of flow and efficiency.Side channel compressors are also used to support flow buildup in fuel cell propulsion, particularly during a (cold) start of the vehicle after a certain period of inactivity. These side channel compressors are typically powered by electric motors, which are powered by the vehicle battery during operation. When switched off, they can generate a significant amount of heat.

[0007] REVISED SHEET (RULE 91) ISA / EP of the fuel cell system and, at low ambient temperatures, so-called ice bridges form between the moving parts, in particular a compressor wheel and a housing, of the side channel compressor.

[0008] DE 10 2019 201 183 and DE 10 2019 219 992 each disclose a side channel compressor for a fuel cell system for conveying and / or compressing a gaseous medium, in particular hydrogen. The side channel compressor can have a housing with a compressor wheel located in the housing, which is arranged to rotate about an axis of rotation and is driven at least indirectly by a drive. The compressor wheel has conveying cells arranged on its circumference in the region of a compressor chamber, and each has a gas inlet opening and a gas outlet opening formed on the housing, which are fluidically connected to one another via the compressor chamber, in particular the at least one side channel.Furthermore, the respective side channel compressor has a drain and / or a valve and / or a purge valve by means of which nitrogen and / or water, which may be contained in the gaseous medium to be conveyed, can be discharged.

[0009] The side channel blower known from DE 10 2019 201 183 and DE 10 2019 219 992 can have certain disadvantages.

[0010] In order to keep the hydrogen concentration in the gaseous medium high, the nitrogen-rich and / or water-rich gas mixture must be vented and replaced with fresh hydrogen. This control, in particular "purging", takes place according to a time grid, since the determination of the nitrogen content is not easy to implement metrologically (e.g. with a mass spectrometer). As a result, a lot of valuable hydrogen is lost during venting and / or purging. Therefore, more hydrogen must be added, for example from a high-pressure tank into the anode circuit, so that the hydrogen concentration in the gaseous medium can be kept correspondingly high. Therefore, the side channel blower known from DE 10 2019 201 183 and DE 10 2019 219 992 has the disadvantage that the efficiency is reduced with frequent venting and / or purging and the hydrogen from the tank is used up more quickly.

[0011] CORRECTED SHEET (RULE 91) ISA / EP Disclosure of the invention

[0012] Advantages of the invention

[0013] According to the invention, a side channel compressor for a fuel cell system for conveying and / or compressing a gaseous medium, in particular hydrogen, is provided with the features of the independent patent claims. Furthermore, a fuel cell system, a method for operating the side channel compressor and / or a fuel cell system, and a method for producing a combined measuring channel-cover assembly are proposed and provided according to the invention.

[0014] Referring to claim 1, a side channel compressor is proposed in which at least one sensor is located in a housing of the side channel compressor, wherein the measured value of wall shear stress is determined by means of the sensor, in particular by means of a surface hot-film method, and wherein the sensor is located in an interrupter region of the compressor chamber of the side channel compressor. This provides the advantage of detecting a wall shear stress of the gaseous medium, which depends on the viscosity of the gaseous medium. The viscosity varies with the composition of the gaseous medium.

[0015] Thus, the placement of the sensor in the breaker area allows for a precise measurement of the wall shear stress, which allows for a precise derivation of the properties and composition of the gaseous medium. Furthermore, the placement of the sensor, which measures using a surface hot-film method, in the breaker area allows for a compact and flat sensor design, with the sensor being particularly flat in the direction of a rotational axis. This allows for a compact design of the entire side channel blower, keeping the required installation space in the overall vehicle to a minimum.

[0016] The subclaims relate to preferred developments of the invention.

[0017] REVISED SHEET (RULE 91) ISA / EP According to an advantageous embodiment of the side channel compressor, the sensor is arranged in the region of a first end face and / or a second end face between a compressor wheel and the housing. The respective end face runs radially to the axis of rotation between the compressor wheel and the housing. In this way, it is possible to achieve the advantage that a relatively narrow gap of a maximum of 2.5 mm, in particular 1 mm, is formed in the interrupter region between the compressor wheel and the housing with the sensor, whereby the properties of the gaseous medium in this region can be efficiently determined by measuring the shear stress. In this case, a short-circuit path exists in this interrupter region, at which the pressure difference between a gas outlet opening and a gas inlet opening is reduced.This pressure difference and the narrow gap create a shear flow that is driven by the rotation of the impeller. The sensor can therefore measure the wall shear stress at this point, particularly using the surface hot film method. The wall shear stress can be measured much more accurately using the sensor in the area of ​​this first and / or second end face than in other areas of the side channel compressor. This is because a small gap in the area of ​​the first and / or second end face between the compressor wheel and the housing allows for maximum viscosity influence, thereby improving the accuracy of the wall shear stress measurement. This allows for a better prediction of the composition of the gaseous medium, which in turn improves the efficiency of a downstream control process. In addition, cost-effective integration of the sensor into the side channel compressor is possible.

[0018] According to a particularly advantageous embodiment of the side channel compressor, the sensor is arranged as close as possible to or directly in the area of ​​an axial gap between the compressor wheel and the housing. The axial gap has a maximum gap size of 2.5 mm, in particular 1 mm. In this way, the advantage can be achieved that the sensor can be arranged in an area between the compressor wheel and the housing, wherein the sensor is attached in particular to the housing in which the compressor wheel has only a small overlap of the area with the blades. The area of ​​the blades of the compressor wheel has openings between the blades running axially to the axis of rotation, which represent a disturbing influence and

[0019] REVISED SHEET (RULE 91) ISA / EP can distort the measurement result of the wall shear stress or at least cause a slight inaccuracy in the measurement result, since flow turbulence can occur in this area. Due to the advantageous design of the side channel blower according to the invention, the influence of flow turbulence can be reduced and the accuracy of the measurement result can be improved.

[0020] According to an advantageous embodiment of the side channel compressor, the sensor is arranged in the region of a shroud surface between the compressor wheel and the housing, wherein in particular the shroud surface is formed axially to the axis of rotation between the compressor wheel and the housing. In this way, the wall shear stress of the gaseous medium can be measured at a point between the compressor wheel and the housing where, on the one hand, there is no opening between the impeller blades, so that at least almost no flow turbulence occurs at this point. This allows negative flow influences when measuring the wall shear stress in this area to be reduced, thereby improving the accuracy of the measurement result. In addition, the compressor wheel, which in one exemplary embodiment has a circumferential outer limiting ring on its outer diameter, which runs rotationally symmetrically to the axis of rotation around the compressor wheel.This limiting ring prevents leakage flows and / or flow turbulence from the compressor chamber, which extend radially outward from the compressor wheel's rotational axis. Furthermore, the sensor allows the wall shear stress to be measured in an area where the greatest relative movement occurs between a surface of the compressor wheel and a surface of the housing, particularly in the area of ​​the shroud surface. This further increases measurement accuracy and maximizes the influence of the viscosity of the gaseous medium. This allows for a precise derivation of the properties and composition of the gaseous medium.

[0021] According to a particularly advantageous development, the side channel compressor is designed such that the sensor is arranged in a channel, in particular a measuring channel, in the housing, wherein the channel is closed by a cover, wherein the cover defines the channel. In this case, the gaseous medium is

[0022] REVISED SHEET (RULE 91) ISA / EP the channel, whereby a laminar flow can be formed, particularly in the channel, by means of the pressure difference Ap between the channel inlet and outlet and the small diameter of the channel. This allows maximum influence of the viscosity to be achieved. The sensor measures the wall shear stress, particularly using a surface hot film, and calculates the viscosity of the anode gas from the known Ap and the known flow geometry of the channel. The channel can have a maximum diameter of 2.5 mm, in particular 1 mm. Since during normal operation only the gas composition changes at one operating point, a change in the wall shear stress can be used to determine the changed gas mixture.In this inventive design of the side channel compressor, the sensor is protected from flow turbulence caused by the blades, which improves the accuracy of the wall shear stress measurement. Furthermore, a compact design of the sensor and the entire side channel compressor can be achieved, thus minimizing the space required within the overall vehicle.

[0023] According to an advantageous development of the side channel blower, the sensor and the cover are designed as a combined measuring channel-cover assembly, which can be pre-assembled and / or inserted as a structural unit into a recess in the housing. This provides the advantage that the measuring channel-cover assembly can be quickly installed as a one-piece solution during assembly of the side channel blower, thus reducing the assembly and processing time of the side channel blower. This also reduces the assembly and processing costs per manufactured side channel blower. Furthermore, in the event of maintenance or repair due to a failure, for example, due to a dirty or blocked channel or a defective sensor, the combined measuring channel-cover assembly can be completely removed in a single step and replaced with a new unit.This can reduce maintenance and repair costs.

[0024] According to an advantageous embodiment, the side channel compressor comprises, in addition to the sensor, which in particular measures the wall shear stress, a speed sensor and / or at least one pressure sensor and / or a control unit and / or a purge valve. This provides the advantage that values ​​for the wall shear stress determined by the sensor and the speed of the compressor wheel by the speed sensor and a pressure difference

[0025] REVISED SHEET (RULE 91) ISA / EP can be determined by means of at least one pressure sensor, from which the viscosity of the gaseous medium and / or the composition of the gaseous medium can be determined, in particular the proportions of hydrogen and / or nitrogen and / or water. The raw data are evaluated by the control valve and, for example, an algorithm stored in the control unit can be used to effectively open the purge valve, a so-called purge, to release nitrogen as needed, while only a small amount of hydrogen, or at least almost no hydrogen, is lost. This way, the efficiency of the side channel compressor and the entire fuel cell system can be improved, as less hydrogen is lost.

[0026] To achieve the stated object, a fuel cell system with a side-channel compressor is also proposed. According to an advantageous embodiment of the fuel cell system, the system includes the control unit and / or the purge valve. This allows for a compact design and arrangement of the components, while also preventing the control unit and / or purge valve from cooling down during long downtimes and low outside temperatures, especially below 0°C, since they are integrated into the fuel cell system.

[0027] A method for operating a side channel compressor and / or a fuel cell system is also proposed. In a first step, the wall shear stress is measured using the sensor. In a second step, the speed n of the compressor wheel of the side channel compressor is recorded using the control unit or the optional speed sensor. In a third step, a flow velocity of the gaseous medium is calculated using the control unit based on the determined speed n. In a fourth step, the known pressure difference Ap is used or the pressure difference Ap is measured, in particular using at least one optional pressure sensor, between the gas inlet opening and the gas outlet opening. In addition, a known flow geometry is used as a basis, for example of the channel and / or the interrupter region.In a fifth step, the viscosity of the gaseous medium is determined at a specific time T1. In a sixth step.

[0028] REVISED SHEET (RULE 91) ISA / EP the measured data are used to calculate a change in the composition of the gaseous medium by delta calculation of several measuring points Tn using the control unit.

[0029] Also proposed is a method for operating a side channel compressor and / or a fuel cell system, comprising the following additional step: calculating a change in the composition of the gaseous medium by delta calculation of several measuring points Tn by means of the control unit and controlling the purge valve.

[0030] A method for producing a combined measuring channel-cover assembly is also proposed. In a first step, a sensor is inserted and connected to the base body using a form-fitting, material-fitting, or force-fitting process. In a second step, the cover is attached to cover and / or overlap the sensor and to form the channel. In a third step, the measuring channel-cover assembly is installed in the side channel compressor, particularly in the interrupter area.

[0031] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

[0032] REVISED SHEET (RULE 91) ISA / EP Brief description of the drawing

[0033] The invention is described in more detail below with reference to the drawing.

[0034] It shows:

[0035] Figure 1 is a schematic sectional view of a side channel compressor according to the invention,

[0036] Figure 2 shows a section of the side channel compressor according to a first embodiment, designated AA in Figure 1,

[0037] Figure 3 shows a section of a combined measuring channel-cover arrangement of the side channel compressor according to a second embodiment, designated II in Figure 2, in a side view,

[0038] Figure 4 is a perspective view of the side channel compressor according to a third embodiment,

[0039] Figure 5 is a simplified representation of a flow chart to illustrate the claimed method,

[0040] Figure 6 A schematic diagram of the elements sensor, control unit, speed sensor, pressure sensor and purge valve.

[0041] Description of the embodiment

[0042] The illustration according to Fig. 1 shows a longitudinal section through a side channel compressor 1 proposed according to the invention, which is designed rotationally symmetrically to a rotation axis 4.

[0043] In Fig. 1 it is shown that the side channel compressor 1 for a fuel cell system 31 for conveying and / or compressing a gaseous medium, in particular hydrogen, is provided with a housing 3 and a drive 6

[0044] CORRECTED SHEET (RULE 91) ISA / EP, wherein the housing 3 has an upper housing part 7 and a lower housing part 8. In addition, the housing 3 has a compressor chamber 30 which runs circumferentially around the axis of rotation 4 and has at least one circumferential side channel 19, 21, with a compressor wheel 2 located in the housing 3, which is arranged so as to be rotatable about the axis of rotation 4 and is driven by the drive 6, wherein the compressor wheel 2 has blades 5 arranged on its circumference in the region of the compressor chamber 30 and each having a gas inlet opening 14 and a gas outlet opening 16 formed on the housing 3, which are fluidically connected to one another via the compressor chamber 30, in particular the at least one side channel 19, 21. The side channel compressor 1 has at least one bearing 27, 47.The at least one side channel 19, 21 can run circumferentially around the rotation axis 4 at least in a partial area of ​​the housing 3, wherein in the partial area in which the at least one side channel 19, 21 is not formed in the housing 3, an interrupter area 15 is formed in the housing 3.

[0045] 1 shows that the drive 6 is designed as an axial-field electric motor 6, which has a stator 11 and a rotor assembly 17, wherein the stator 11 and the rotor assembly 17 are designed in a disk-shaped manner so as to rotate around the axis of rotation 4 and wherein the stator 11 is arranged next to the rotor assembly 17 in the direction of the axis of rotation 4. The rotor assembly 17 can be located at least indirectly on or in a hub disk 23 of the compressor wheel 2. FIG. 1 also shows that the side-channel compressor 1 has a stator chamber 42 and a rotor chamber 44, wherein components of the drive 6 are at least partially arranged in these chambers 42, 44. The upper housing part 7 has a continuous wall 29, which is located between the stator chamber 42 and the rotor chamber 44 and effects a fluidic separation between them. The stator chamber 42 is also at least partially surrounded and / or encapsulated by a stator housing 39.The lower housing part 8 has a cylindrical bearing journal 12, wherein the bearing journal 12 runs in the direction of the axis of rotation 4 in such a way that its outer surface runs circumferentially around the axis of rotation 4 and wherein a first bearing 27 and / or a second bearing 47 are in contact with the outer surface of the bearing journal 12 radially to the axis of rotation 4. The drive 6 can be designed as an axial field electric motor 6 which has the stator 11 and the rotor assembly 17, wherein the stator 11 runs in the direction of the axis of rotation 4 next to the rotor assembly.

[0046] CORRECTED SHEET (RULE 91) ISA / EP group 17. In addition, the side channel compressor 1 has the cylindrical bearing journal 12, wherein the bearing journal 12 runs in the direction of the axis of rotation 4 such that its outer surface runs circumferentially around the axis of rotation 4. The first bearing 27 and / or the second bearing 47 are in contact with the outer surface of the bearing journal 12 radially to the axis of rotation 4.

[0047] Furthermore, Fig. 1 shows that the compressor wheel 2 has the hub disk 23 on its inner diameter. The compressor wheel 2 is connected to a hub 9 in the area of ​​the hub disk 23. The hub 9 has an inner bore 20 in the inner bore 20. The inventive design of the side channel compressor 1 provides that at least one sensor 18 is located in the housing 3 of the side channel compressor 1, wherein the measured variable wall shear stress is determined by means of the sensor 18, in particular by means of a surface hot film method, and wherein the sensor 18 is located in the interrupter region 15 of the compressor chamber 30 of the side channel compressor 1. The sensor 18 can be located in the area of ​​a first end face 24 and / or a second end face 26 between the compressor wheel 2 and the housing 3. The end faces 24, 26 run radially to the axis of rotation 4 between the compressor wheel 2 and the housing 3.In an exemplary advantageous embodiment, the sensor 18 is located in an area of ​​a small gap between the compressor wheel 2 and the housing 3, wherein the sensor 18 is arranged as close as possible to or directly in the area of ​​a respective first axial gap 28 between the compressor wheel 2 and the housing 3. The respective first axial gap 28 is located in the area of ​​the inner diameter of the blades 5 facing the axis of rotation 4, while a respective second axial gap 32 is located in the area of ​​the outer diameter of the blades 5 facing away from the axis of rotation 4. In a further exemplary embodiment of the side channel compressor 1, the sensor 18 can be located in the area of ​​a shroud surface 34 of the housing 3.

[0048] The object of the invention is to use the side channel compressor 1 to provide defined conditions for the sensor 18 so that the anode gas composition can be easily measured. The measured value is the wall shear stress, which depends on the viscosity and the velocity of the medium. The viscosity is related to the gas composition.

[0049] REVISED SHEET (RULE 91) ISA / EP variable. Any water contained in the gaseous medium is either separated beforehand by the high radial forces or expelled through the gas outlet opening 16.

[0050] Fig. 2 shows a section, designated AA in Figure 1, of the side channel compressor 1 according to a first exemplary embodiment. The gaseous medium is supplied to the side channel compressor 1, in particular to the compressor wheel 2 and / or the respective side channel 19, 21, via the gas inlet opening 14. The gaseous medium is compressed by the compressor wheel 2 rotating in a direction of rotation 41 and leaves the side channel compressor 1 at a higher pressure via the gas outlet opening 16. In the interrupter region 15 there is a short-circuit path at which the pressure difference between the outlet and inlet is reduced. This pressure difference and the narrow gap create a shear flow that is driven by the rotation of the compressor wheel 2.The sensor 18 measures the wall shear stress on a surface hot film at this point, and the viscosity of the gaseous medium is determined from the known variables of pressure difference and speed of the compressor wheel 2. The sensor 18 can be embedded in the area of ​​a recess 35 in the housing 3. It is also shown that the sensor 18 can be located in the immediate vicinity of and / or in the area of ​​the first axial gap 28.

[0051] Fig. 3 shows a section, designated II in Figure 2, of a combined measuring channel-cover arrangement 33 of the side channel compressor 1 according to a second exemplary embodiment in a side view. It is shown that the sensor 18 is arranged in a channel 25, in particular a measuring channel 25, in a base body 36. The channel 25 is closed by means of a cover 22, wherein the cover 22 defines the channel 25. The sensor 18 and the cover 22 are designed as a combined measuring channel-cover arrangement 33, which can be pre-assembled and / or introduced as a structural unit 33 into the recess 35 of the housing 3. The gaseous medium flows through the channel 25 in a flow direction 10 past the sensor 18, wherein the flow 10 is present as a laminar flow 38 due to the geometric shape, in particular the diameter of the channel 25.

[0052] REVISED SHEET (RULE 91) ISA / EP Furthermore, in the embodiment of the side channel compressor 1 according to the invention, a method for producing a combined measuring channel-cover arrangement 33 is claimed, comprising the following steps:

[0053] Providing a base body 36,

[0054] Inserting and connecting a sensor 18 into the base body 36 by means of a form-fitting, material-fitting or force-fitting process,

[0055] Attaching the cover 22 to cover and / or cover the sensor 18 and to form the channel 25,

[0056] Installation of the measuring channel cover assembly 33 in the side channel compressor 1, particularly in the interrupter area 15.

[0057] Fig. 4 shows a perspective view of the side channel compressor 1 according to a third exemplary embodiment. The sensor 18 is located in the region of a shroud surface 34 between the compressor wheel 2 and the housing 3. The shroud surface 34 is formed on the housing 3, particularly in the lower housing part 8, axially to the rotational axis 4 between the compressor wheel 2 and the housing 3.

[0058] In Fig. 5, rectangles 51 to 56 and arrows arranged between them show in a highly simplified manner how the multi-stage method for operating the side channel compressor 1 can proceed. In a first method step 51, a wall shear stress is measured by means of the sensor 18. In a second method step 52, a rotational speed n of the compressor wheel 2 of the side channel compressor 1 is measured by means of a control unit 43 or by means of an optional rotational speed sensor 45. In a third method step 53, a flow velocity of the gaseous medium is calculated, in particular by means of the control unit 43 based on the determined rotational speed n.In a fourth method step 54, the known and / or measured pressure difference Ap or measurement by means of at least one optional pressure sensor 49 between the gas inlet opening 14 and the gas outlet opening 16 and a known flow geometry, for example the channel 25 and / or the interrupter region 15, is used. In a fifth method step 55, the viscosity of the gaseous medium at a specific time T is determined. In an optional sixth method step 56.

[0059] REVISED SHEET (RULE 91) ISA / EP a calculation of a change in the composition of the gaseous medium by delta calculation of several measuring points Tn by means of the control unit 43 and control of a purge valve 40.

[0060] Fig. 6 shows an arrangement of various components of the side channel compressor 1 and / or the fuel cell system 31. The arrangement is a schematic diagram of the elements sensor 18, control unit 43, optional speed sensor 45, optional pressure sensor 49 and purge valve 40. The control unit 43 and the purge valve 40 do not necessarily have to be arranged in or on the side channel compressor 1, but can alternatively be located in a further area of ​​the fuel cell system 31, in particular in an anode circuit. The side channel compressor 1 can be arranged in an anode circuit of the fuel cell system 31. The components sensor 18 and / or speed sensor 45 and / or optional pressure sensor 49 can supply measured values ​​and data to the control unit 43, wherein the control unit 43 controls the purge valve 40 depending on a stored algorithm for evaluating the data.The purge valve 40 is only opened by means of a control of the control unit 43 when the gaseous medium has a high concentration of nitrogen and / or other components that are not hydrogen.

[0061] REVISED SHEET (RULE 91) ISA / EP

Claims

Claims 1 . Side channel compressor (1) for a fuel cell system (31) for conveying and / or compressing a gaseous medium, in particular hydrogen, comprising a housing (3) and a drive (6), wherein the housing (3) has an upper housing part (7) and a lower housing part (8), with a compressor chamber (30) extending in the housing (3) circumferentially around a rotational axis (4) and having at least one circumferential side channel (19, 21), with a compressor wheel (2) located in the housing (3), which is arranged rotatably about the rotational axis (4) and is driven by the drive (6), wherein the compressor wheel (2) has blades (5) arranged on its circumference in the region of the compressor chamber (30) and each having a gas inlet opening (14) and a gas outlet opening (16) formed on the housing (3), which are fluidically connected to one another via the compressor chamber (30), in particular the at least one side channel (19, 21),wherein the compressor chamber (30) and the at least one side channel (19, 21) have an interrupter region (15), characterized in that at least one sensor (18) is located in the housing (3) of the side channel compressor (1), wherein the measured value of wall shear stress is determined by means of the sensor (18), in particular by means of a surface hot film method, and wherein the sensor (18) is located in the interrupter region (15) of the compressor chamber (30) of the side channel compressor (1).

2. Side channel compressor (1) according to claim 1, characterized in that the sensor (18) is arranged in the region of a first end face (24) and / or a second end face (26) between the compressor wheel (2) and the housing (3), wherein in particular the end faces (24, 26) are formed radially to the axis of rotation (4) between the compressor wheel (2) and the housing (3).

3. Side channel compressor (1) according to claim 1 or 2, characterized in that the sensor (18) is arranged as close as possible to or directly in the region of an axial gap (28) between the compressor wheel (2) and the housing (3). REVISED SHEET (RULE 91) ISA / EP 4. Side channel compressor (1) according to claim 1, characterized in that the sensor (18) is arranged in the region of a shroud surface (34) between the compressor wheel (2) and the housing (3), wherein in particular the shroud surface (34) is formed axially to the axis of rotation (4) between the compressor wheel (2) and the housing (3) on the housing (3).

5. Side channel compressor (1) according to one of the preceding claims, characterized in that the sensor (18) is arranged in a channel (25), in particular a measuring channel (25), in the housing (3), wherein the channel (25) is closed by means of a cover (22), wherein the cover (22) defines the channel (25).

6. Side channel compressor (1) according to claim 5, characterized in that the sensor (18) and the cover (22) are designed as a combined measuring channel-cover arrangement (33) which can be pre-assembled and / or introduced as a structural unit (33) into a recess (35) of the housing (3).

7. Side channel compressor (1) according to one of the preceding claims, characterized in that the side channel compressor (1) has, in addition to the sensor (18), a speed sensor (45) and / or at least one pressure sensor (49) and / or a control unit (43) and / or a purge valve (40) 8. Fuel cell system (31) with a side channel compressor (1) according to one of claims 1 to 7, wherein the side channel compressor (1) is arranged in an anode circuit of the fuel cell system (31) and wherein the fuel cell system (31) has the control unit (43) and / or the purge valve (40).

9. A method for operating a side channel compressor (1) and / or a fuel cell system (31) according to one of the preceding claims, comprising the following steps: Measuring the wall shear stress (51) using the sensor (18) REVISED SHEET (RULE 91) ISA / EP - detecting (52) the speed n of the compressor wheel (2) of the side channel compressor (1) by means of the control unit (43) or by means of the optional speed sensor (45), - Calculation (53) of a flow velocity of the gaseous medium by means of the control device (43) based on the determined rotational speed n, - Using (54) the known pressure difference Ap or measuring (54) pressure difference Ap, in particular by means of at least one optional pressure sensor (49), between the gas inlet opening (14) and the gas outlet opening (16) and a known flow geometry, for example a channel (25) and / or the interrupter region (15), - Determination (55) of the viscosity of the gaseous medium at a given time T1.

10. A method for operating a side channel compressor (1) and / or a fuel cell system (31) according to claim 9, comprising the following additional step Calculation (56) of a change in the composition of the gaseous medium by delta calculation of several measuring points Tn by means of the control unit (43) and control of a purge valve (40).

11. A method for producing a combined measuring channel cover assembly (33) according to claim 6, comprising the following steps: Providing a base body (36), Inserting and connecting a sensor (18) into the base body (36) by means of a form-fitting, material-fitting or force-fitting process, Attaching the cover (22) to cover (22) and / or cover the sensor (18) and to form the channel (25), Installation of the measuring channel cover arrangement (33) in the side channel compressor (1), particularly in the interrupter area (15). REVISED SHEET (RULE 91) ISA / EP

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