COMPRESSOR

Description

[0001] The invention relates to a compressor with a rotatably mounted compressor wheel, wherein the compressor wheel has a radially inner inlet area and a radially outer outlet area, wherein the inlet area is connected to the outlet area via flow channels extending from the inlet area to the outlet area, wherein the flow channels form flow outlets in the outlet area which are spaced apart from the axis of rotation of the compressor wheel, wherein the flow channels each have a flow cross-section extending in the circumferential direction of the compressor wheel, wherein the flow channels have a channel length extending from the inlet area to the outlet area and wherein the flow channels have a minimum flow channel cross-section along the channel length.

[0002] Compressors in a wide variety of designs are known from the prior art. An example of a turbo compressor is shown in EP 3 421 825 A1. These turbo compressors use a compressor wheel mounted on a drive shaft. To generate high pressure and high mass flow rates, such compressors are designed as radial or centrifugal compressors. The compressor wheel draws in the air to be compressed centrally at its inlet area in the axial direction. The drawn-in air then enters the flow channels via the flow inlets. Within the flow channels, the air is guided and, as the compressor wheel rotates, is forced radially outwards by the centrifugal forces. The compressed air then exits the flow channel at the flow outlet.

[0003] Reference is also made to KR 2018 0056118 A9, WO 96 / 08655 A1, RU 93 476 U1 and US 2010 / 322771 A1. These documents reveal compressors with relatively small flow channel cross-sections.

[0004] For certain applications, it may now be required to provide a compressor that is suitable for generating high pressure, but only provides a small mass flow rate.

[0005] For example, an application according to the invention may require a compressor that conveys a fluid with a very low mass flow rate (for example, in the range of 1-10 g / s) while simultaneously operating at high pressure ratios (differential pressure between the pressure in the outflow area and the inflow area greater than 2 bar). These very specific requirements can result from an application of the compressor according to the invention in which ambient air is compressed to supply it to a compressed air-operated cleaning system for lidar sensors. The use of such a cleaning system can, for example, be provided for in autonomous vehicles equipped with lidar sensors, according to the invention.

[0006] The required pressure ratio can be achieved in conjunction with a turbo compressor and a corresponding peripheral speed at the compressor wheel's outlet. Due to the limited rotational speed of the drive (approximately 100,000 rpm) that powers the compressor wheel (for example, an electric motor), achieving these high pressure ratios presents a challenge. The necessary peripheral speed can therefore only be realized through large compressor wheel outlet diameters. This results in a design with a very low diameter-specific flow rate. This diameter-specific flow rate of turbo compressors is essentially determined by the flow cross-section between the blades, the rotor hub, and the casing contour, and can only be varied to a limited extent through design considerations.When designing for a very low diameter-specific flow rate, the duct cross-section must be dimensioned accordingly small. In extreme cases, this leads to an unfavorable ratio between the blade height and the gap height between the compressor wheel and the housing. Ultimately, the duct height cannot be less than the gap height. If, in the limiting case, the duct height equals the gap height, there is no longer any installation space for the rotor blades, and the compressor can no longer function. If the diameter-specific flow rate in this hypothetical case is still greater than the requirement, the design of such a turbo compressor is technically impossible. Even before reaching the described limiting case, reducing the blade height results in a very unfavorable surface-to-volume ratio.This results in virtually no free flow cross-section due to the boundary layers, making a technically sensible design impossible.

[0007] The object of the invention is to provide a compressor which has a very low diameter-specific throughput, but nevertheless achieves high pressure ratios and exhibits stable operating behavior.

[0008] This problem is solved by using the distance of the flow outlet furthest from the axis of rotation of the compressor wheel as a radius for calculating a circular area, and by ensuring that the sum of the minimum flow channel cross-sections of all flow channels of the compressor wheel, relative to this circular area, is less than 0.01, preferably less than 0.008.

[0009] In other words, the following applies: min Querschnittsfl ä che Kan ä le Fl ä che resultierend aus maximalen Durchmesser < 0 , 01 , vorzugsweise < 0,008 .

[0010] In contrast to known turbo compressors, the flow rate through the compressor wheel in the solution according to the invention is limited by the design of the flow channels. Only small mass flow rates are conveyed, while at the same time the compressor principle used in radial compressors is retained in order to achieve the desired high pressure ratio.

[0011] The compression ratio can be adjusted by varying the distance of the flow outlets from the axis of rotation. The flow rate can be adjusted by modifying the number and cross-section of the flow channels. This allows the compressor to be scalable in both relevant dimensions (flow rate and pressure ratio). The compressor can then be operated reliably and stably. Stable operation is characterized by the fact that the operating points lie within the two operating limits (pump and choke limits).

[0012] For example, the solution according to the invention makes it possible to create compressors with which dimensionless speed characteristics σ in the range between 0.01 and 0.05, preferably between 0.01 and 0.03, can be achieved, wherein σ is calculated according to the formula: σ = V × 2 × π ÷ Δ p / ρ × 2 3 / 4

[0013] The following applies: Δp = differential pressure between the pressure in the outflow area and the pressure in the inflow area ρ = density of the pumped fluid V = volume flow rate of the pumped fluid.

[0014] Additionally or alternatively, compressors can be created, for example, with the solution according to the invention, with which dimensionless diameter parameters δ in the range between 20 and 100, preferably 20 and 70, can be achieved, wherein δ is calculated according to the formula: δ = Δ p ρ × 2 ÷ V 2 4 × π ÷ 2

[0015] The following applies: Δp = differential pressure between the pressure in the outflow area and the pressure in the inflow area ρ = density of the pumped fluid V = volume flow rate of the pumped fluid.

[0016] Such dimensionless speed and / or diameter parameters lead to completely new types of machinery, which were previously unknown in the state of the art.

[0017] According to one possible embodiment of the invention, it may be provided that the volume occupied by the compressor wheel is at least 3 times larger than the sum of the channel volumes of the flow channels, and / or that the maximum opening width of the flow outlets or at least a part of the flow outlets of the compressor wheel extends circumferentially over a maximum central angle of 10°.

[0018] The volume of the compressor wheel is determined from the outer contour of the compressor wheel, while internal cavities, such as recesses or hollow spaces within the compressor wheel, are disregarded.

[0019] The impeller volume is many times larger than the sum of the volumes of the compressor wheel's flow channels. The compression ratio can be adjusted by changing the outer diameter of the compressor wheel. The flow rate can be adjusted by changing the number and cross-section of the flow channels. This allows the compressor to be scaled in both relevant dimensions (flow rate and pressure ratio).

[0020] Preferably, the volume occupied by the compressor wheel can be at least six times, preferably at least eight times, larger than the sum of the channel volumes of the flow channels, and / or the maximum opening width of the flow outlets, or at least a portion of the flow outlets of the compressor wheel, extends circumferentially over a maximum central angle of 0.5° to 10°, preferably over a maximum central angle of 1° to 7°, and / or the maximum opening width of the flow inlets of the flow channels, or at least a portion of the flow inlets of the flow channels of the compressor wheel, extends circumferentially over a maximum central angle of 3° to 20°, preferably over a maximum central angle of 6° to 14°. These designs are particularly suitable for the effective cleaning of sensor surfaces.

[0021] According to a preferred embodiment of the invention, at least some of the flow channels may be designed as circumferentially closed cavities, at least in certain areas. In contrast to known turbo compressors, this solution does not use blades. Therefore, this solution does not present a limiting case between the possible blade height and the necessary gap. Rather, the cross-sectional area determining the flow rate can be adjusted both by modifying the cross-sectional areas of the cavities and by changing the number of cavities.

[0022] A preferred embodiment of the invention is such that the size of the flow cross-section of at least a portion of the flow channels does not change, at least in certain regions, along the length of the channel. This design of a compressor wheel is easy to manufacture. Preferably, at least a portion of the flow channels in a region between the flow inlet and outlet may have the form of a cylindrical bore. For example, the bores can then simply be drilled into a compressor wheel. The bores can run radially or be inclined in or opposite to the direction of rotation of the compressor wheel.

[0023] Within the scope of the invention, it is also conceivable that the size of the flow cross-section of at least a portion of the flow channels changes, at least in certain regions, along the length of the channel. This can further influence the mass flow rate through the flow channel and, in particular, the pressure ratio generated at a given rotational speed.

[0024] Preferably, it can be provided that in at least some of the flow channels the flow cross-section tapers radially outwards in a region between the flow inlet and the flow outlet.

[0025] This effectively compensates for the increase in the density of the pumped fluid in the flow channel.

[0026] A compressor according to the invention can be configured such that the flow outlet of at least some of the flow channels is offset relative to the flow inlet in the circumferential and / or axial direction. This allows for the adjustment of flow deviations at the flow inlet as well as the outflow angle at the compressor wheel outlet, in order to influence the compressor, for example, with regard to operational stability and pressure head. This can be further or alternatively improved by having at least some of the flow channels curved in the circumferential direction in a region between the flow inlet and the flow outlet.

[0027] An offset in the axial direction allows the compressor wheel to be designed in a space-optimized manner.

[0028] If at least part of the flow channels are formed in the area between two interconnected components, even complex flow channel configurations can be easily manufactured. It is particularly advantageous for one of the components to have a groove running along the length of the channel, defining its boundaries, while the other component completes or covers at least part of the groove. The groove can be easily machined into the component in the desired shape, for example, by milling.

[0029] According to one possible embodiment of the invention, it can be provided that the cross-sectional area of ​​at least one flow channel at the flow inlet and / or at the flow outlet is at least 0.5 mm² and at most 15 mm², preferably at least 1 mm² and at most 5 mm², in order to achieve the desired conveying effect.

[0030] The object of the invention is also achieved with an assembly, in particular for a land vehicle or a watercraft or an aircraft, comprising an optical sensor, in particular a lidar sensor, and a compressor according to one of claims 1 to 12, wherein a channel connection is arranged between the compressor wheel and the sensor in order to direct the fluid compressed by the compressor wheel, in particular air, to a surface of the sensor for cleaning purposes.

[0031] The invention will be explained in more detail below with reference to exemplary embodiments illustrated in the drawings. The drawings show: Figure 1 in perspective partial representation a compressor, Figure 2 the compressor according to Figure 1 in full cut, Figure 3 a compressor wheel for a full-cut compressor and along the in Figure 4 with section line marked III-III, Figure 4 the compressor wheel according to Figure 3 along the in Figure 3with section line marked IV-IV and Figures 5a-5f various design variants of compressor wheels.

[0032] Figure 1 The figure shows a compressor that can be used, for example, in a cleaning system where compressed air is used for cleaning. This cleaning system can be used, for instance, to clean the optical surface of a sensor, particularly a lidar sensor.

[0033] Figure 2 The figure shows the compressor in detail and in full section. As this illustration demonstrates, the compressor has a drive unit, which can be, for example, an electric motor 41. The electric motor 41 has a motor rotor 44, to which a motor stator 45 is assigned. The motor rotor 44 is connected to a drive shaft 42. The drive shaft 42 and the motor rotor 41 can form an integral component. The drive shaft 42 is rotationally fixed to a compressor wheel 10.

[0034] The motor stator 45 of the electric motor 41 is housed in a casing with a casing part 40. The casing part 40 can be closed off by means of a bearing part 30. The bearing part 30 has a bearing receptacle 32 in which a bearing 33 for supporting the drive shaft 42 is received. The bearing part 30 is sealed against the casing part 40 (seals 34).

[0035] The compressor wheel 10 can preferably be manufactured in one piece. However, it is also conceivable that the compressor wheel 10 is made of multiple parts, in particular two parts.

[0036] The compressor wheel 10 has a hub 12 to which the compressor wheel 10 is rotationally fixed to the drive shaft 42. For this purpose, the compressor wheel 10 can be connected to the drive shaft 42, in particular clamped, by means of a nut 43 which is screwed onto a thread of the drive shaft 42. In the present embodiment, a spacer sleeve 18 is arranged between the nut 43 and a support surface of the hub 12.

[0037] A sealing bushing 35 can be arranged between the compressor wheel 10 and the bearing 33, sealing the bearing 33 against the flow channel. Furthermore, a support washer 31 can be provided to secure the bearing 33, for example a ball bearing, at its outer ring.

[0038] The compressor wheel 10 has a central inlet area 11, which can be formed as a recess in the compressor wheel 10 in the area of ​​an inlet side 16. Flow channels 15, formed as cavities, are integrated into the compressor wheel 10 from the inlet area 11. These cavities are completely surrounded on all sides by the geometry of the compressor wheel 10.

[0039] The inflow area 11 can be designed such that it is at least partially bounded by a circumferential inner wall 13. The inner wall 13 has openings which are formed in the form of flow inlets 15.1 of the flow channels 15.

[0040] In the area of ​​its outer circumference, the compressor wheel 10 has an outflow area 14. The flow channels 15 each open there with a flow outlet 15.2.

[0041] According to the invention, the flow channels 15 have a flow cross-section that varies or remains constant along the channel length. The volume of a flow channel 15 is calculated accordingly from the channel length and the flow cross-section. The flow channels 15, which are formed as cavities in the compressor wheel 10, have a total channel volume. The compressor wheel occupies a compressor wheel volume. According to the invention, the compressor wheel volume is an integer multiple larger than the channel volume. As mentioned above, the compressor wheel volume is determined by the outer boundary of the compressor wheel 10.

[0042] The flow channels 15 are arranged at circumferential intervals. The angular distance in the area of ​​the flow outlet 15.2 and / or in the area of ​​the flow inlet 15.1 is at least 18°.

[0043] Figure 2Figure 1 further illustrates that a housing can be provided with at least one housing part 20 which has or forms a spiral channel 22. This spiral channel 22 opens in the outflow area 14 on the circumferential side of the compressor wheel 10. Thus, the flow channels 15 open into the spiral channel 22 at their flow outlet 15.2.

[0044] Downstream of the spiral channel 22, a compressed air connection 24 is provided to which a compressed air line can be connected. The compressed air connection 24 is preferably integrally connected to the housing or housing part 20. Furthermore, the housing or housing part 20 may have a connection nozzle 23 that forms an intake channel 23.1. The intake channel 23.1 leads to the inlet area 11. An air supply line can be connected to the connection nozzle 23 so that the compressor wheel 10 can draw air via the intake channel 23.1 to the flow inlets 15.1 of the flow channels 15.

[0045] Figure 2 This illustrates that the housing part 20 can have a centering receptacle 21 on which the housing part 20 is aligned relative to the housing part 40 or relative to the bearing part 30.

[0046] Finally, it is possible that the housing part 20 forms a wheel receptacle 25 in which the compressor wheel 10 is at least partially received. In the present embodiment, the wheel receptacle 25 is bounded by the housing part 20 and the housing of the electric motor 41, in this case by the bearing part 30 of the electric motor 41.

[0047] According to a preferred embodiment, the compressor wheel 10 is received in a wheel housing 25, which is sealed against the environment except for the intake air opening (intake duct 23.1) and the exhaust air opening (spiral duct 22). In the present embodiment, seals 34 are provided between the bearing part 30 and the housing part 40 for this purpose.

[0048] Figure 3 shows a possible design variant of a compressor wheel, as used, for example, in the compressor according to the Figure 1 and 2This can be used. As this illustration shows, the compressor wheel 10 has flow channels 15 that run radially and are incorporated into the material of the compressor wheel 10 in the form of conical bores. The flow channels 15 taper continuously or discontinuously outwards in the radial direction. It is also conceivable that cylindrical bores could be used for the flow channels 15.

[0049] Furthermore, it is also conceivable that flow channels 15 are used whose flow cross-section expands continuously or discontinuously along the channel length and in the flow direction, at least in partial areas.

[0050] The Figures 3 and 4illustrate that the compressor wheel 10 can again have a hub 12, which has an inflow area 11 in the area of ​​an inflow side 16 and can have a drive side 17 opposite the inflow side 16, for connection with a drive shaft 42, for example of an electric motor 41. Figure 3 Figure 1 shows that all flow outlets of the flow channels 15 are spaced uniformly from the axis of rotation of the compressor wheel 10 by a distance R, where R is preferably the radius of the outer circumference of the compressor wheel 10. The circular area, which can be calculated using the radius R, is A mm². The flow channels 15 have a minimum cross-sectional area in the region of the flow outlets. The sum of these minimum cross-sectional areas of all flow channels 15 of the compressor wheel 10 is B mm². According to the invention: B / A < 0,005 .

[0051] The compressor wheel 10 occupies a space with a volume of its outer contour. This volume is determined without taking into account any cavities or recesses in the compressor wheel 10. In other words, the volume of the compressor wheel 10 is the volume that surrounds it. This volume is at least three times larger than the sum of the volumes of the flow channels 15.

[0052] Figure 4 This illustrates that the maximum opening width of the flow outlets of the flow channels 15 of the compressor wheel 10 extends circumferentially over a maximum central angle of 10°.

[0053] The Figures 5A Figure 5F shows various design variants of compressor wheels 10. The compressor wheels 10 correspond in principle in their construction to the compressor wheels 10 as described in relation to the Figures 1-4These have already been described. To avoid repetition, reference is made to the preceding explanations. The following section will only explain the differences between these compressor wheels.

[0054] The design options according to the Figures 5a to 5f differ in terms of the arrangement and design of their flow channels 15.

[0055] Figure 5a shows a compressor wheel 10 with radially extending flow channels 15, which are designed in the form of cylindrical bores.

[0056] Figure 5b Figure 1 shows a compressor wheel 10 with radially extending flow channels 15. The flow cross-sections of these flow channels 15 taper continuously outwards in the radial direction along the channel length.

[0057] The Figures 5c and 5d The compressor wheels 10 have flow channels 15 that are curved along the length of the channel. According to... Figure 5cFlow channels 15 are provided which are curved in the opposite direction of rotation ω. Fig. 5b shows flow channels 15 that are curved in the direction of rotation ω.

[0058] It is also possible that the flow channels 15 have regions that are curved both in and against the direction of rotation ω. It is also conceivable that the flow channels 15 have a constant flow cross-section along their length or a varying flow cross-section.

[0059] The Figures 5e and 5f To illustrate that, within the scope of the invention, the flow channels 15 can be designed such that the flow inlet 15.1 is arranged offset from the flow outlet 15.2 in the direction of rotation Omega. This feature can be used in all compressor wheels 10 according to the invention, in particular in the compressor wheels according to the Figures 5a to 5d be realized.

[0060] It may be that the flow inlet 15.1 is offset backwards in the direction of rotation ω relative to the flow outlet 15.2 (5e) or that the flow outlet 15.1 is offset backwards in the direction of rotation Omega relative to the flow inlet 15.2 ( Figure 5 f) .

Claims

1. Compressor with a rotatably mounted compressor wheel (10), the compressor wheel (10) having a radially inner inflow region (11) and a radially outer outflow region (14), the inflow region (11) being connected to the outflow region (14 ) via flow channels (15) which run from the inflow region (11) to the outflow region (14), the flow channels (15) forming flow inlets (15.1) in the inflow region (11), the flow channels (15) forming flow outlets (15.2) in the outflow region (14), which are arranged at a distance from the axis of rotation of the compressor wheel, the flow channels (15) each having a flow cross-section extending in the circumferential direction of the compressor wheel (10), the flow channels (15) having a channel length running from the inflow region (11) to the outflow region (14), and the flow channels (15) having a minimum flow channel cross section along the channel length, characterized in that the distance of the flow outlet that is furthest from the axis of rotation of the compressor wheel (10) forms a radius for calculating a circular area, in that the sum of the minimum flow channel cross sections of all flow channels (15) of the compressor wheel (10) is less than 0.01, preferably less than 0.008, relative to this circular area.

2. Compressor according to claim 1, characterized in that the compressor wheel volume which the compressor wheel (10) occupies is at least three times greater than the sum of the channel volumes of the flow channels (15), and / or that the maximum opening width of the flow outlets or at least some of the flow outlets of the compressor wheel (10) extends in the circumferential direction over a maximum central angle of 10°.

3. Compressor according to claim 1 or 2, characterized in that at least some of the flow channels (15) are designed at least in some regions as cavities that are closed peripherally.

4. Compressor according to one of claims 1 to 3, characterized in that the magnitude of the flow cross-section of at least some of the flow channels (15) does not change in the direction of the channel length, at least in some regions, wherein it is preferably provided for at least some of the flow channels (15) to have the shape of a cylindrical bore in a region between the flow inlet (15.1) and the flow outlet (15.2).

5. Compressor according to one of claims 1 to 4, characterized in that the size of the flow cross-section of at least some of the flow channels (15) changes in the direction of the channel length, at least in some regions, wherein it is preferably provided that in at least some of the flow channels (15), the flow cross-section narrows in a region between the flow inlet (15.1) and the flow outlet (15.2) in the radial outward direction.

6. Compressor according to one of claims 1 to 5, characterized in that the flow outlet (15.2) of at least some of the flow channels (15) is arranged offset with respect to the flow inlet (15.1) in the circumferential direction of the compressor wheel (10) and / or in the axial direction of the compressor wheel (10).

7. Compressor according to one of claims 1 to 6, characterized in that at least some of the flow channels (15) run in a curved manner in the circumferential direction in a region between the flow inlet (15.1) and the flow outlet (15.2).

8. Compressor according to one of claims 1 to 7, characterized in that at least some of the flow channels (15) are formed in the region between two interconnected components, wherein it is preferably provided that one of the components has a groove running in the direction of the channel length, which groove delimits the flow channel and the other component completes or covers the groove at least in some areas.

9. Compressor according to one of claims 1 to 8, characterized in that the compressor wheel (10) has a central opening or a central recess in the region of its axis of rotation, and in that the opening or the central recess is in fluid-conducting communication, in the inflow region (11), with the flow inlets of the flow channels (15).

10. Compressor according to one of claims 1 to 9, characterized in that the volume occupied by the compressor wheel (10) is at least six times, preferably at least eight times, greater than the sum of the channel volumes of the flow channels (15), and / or that the maximum opening width of the flow outlets or at least some of the flow outlets of the compressor wheel (10) extends in the circumferential direction over a maximum central angle of 0.5° to 10°, preferably over a maximum central angle of 1° to 7°.

11. Compressor according to one of claims 1 to 10, characterized in that the magnitude of the cross-sectional area of at least one flow channel (15) at the flow inlet (15.1) and / or at the flow outlet is at least 0.5 mm2 and at most 15 mm2, and / or that the magnitude of the cross-sectional area of at least one flow channel (15) at the flow inlet (15.1) and / or at the flow outlet (15.2) is at least 1 mm2 and at most 5 mm2.

12. Compressor according to one of claims 1 to 11, characterized in that a housing with a spiral channel is arranged in the region of the outer circumference of the compressor wheel (10), and in that the flow channels (15) open into the spiral channel.

13. Compressor according to one of the claims 1 to 12, characterized in that the compressor wheel is coupled to a drive, for example to an electric motor, via a drive shaft.

14. Assembly, in particular for a vehicle or a watercraft or an aircraft, with an optical sensor, in particular a lidar sensor, and a compressor according to any one of claims 1 to 12, wherein a channel connection is arranged between the compressor wheel (10) and the sensor, in order to supply the compressed air generated by the compressor wheel (10) to a surface of the sensor for cleaning purposes.