Blower for pumping hydrogen in a fuel cell system of a motor vehicle

Abstract

Blower for conveying hydrogen in a fuel cell system of a motor vehicle, with a flow housing (10) which has a flow housing cover (16), an inlet (30) and an outlet (44) which are formed on the flow housing (10) a conveying channel (36, 38) arranged in the flow housing (10) which fluidically connects the inlet (30) with the outlet (44), an impeller (48) rotatably mounted in the flow housing (10) and a drive shaft (14) on which the wheel (48) is arranged, wherein the flow casing cover (16) is arranged geodesically below the impeller (48) and a cover surface (64) of the flow casing cover (16) facing the impeller (48) is formed closed, wherein a space (62) is formed between the cover surface (64) and a first impeller surface (56) facing the cover surface (64), characterized in that the lid surface (64) is at least partially funnel-shaped, with the radial interior of the lid surface (64) being geodesically arranged at the lowest position.

Description

[0001] The invention relates to a blower for conveying hydrogen in a fuel cell system of a motor vehicle, comprising a flow housing which has a flow housing cover, an inlet and an outlet which are formed on the flow housing, a conveying channel arranged in the flow housing which fluidically connects the inlet with the outlet, an impeller rotatably mounted in the flow housing and a drive shaft on which the impeller is arranged.

[0002] These types of blowers are typically designed as side-channel blowers. They circulate hydrogen, usually with a high water content, in the anode gas circuits of fuel cell systems in motor vehicles. These fuel cell systems convert the chemical reaction energy of a continuously supplied fuel, particularly hydrogen, and an oxidizer, usually oxygen, into electrical energy, which can be used, for example, to power vehicles. These blowers are usually driven by electric motors, which, when operating in vehicles, are powered by the vehicle's battery.

[0003] Similar blowers are disclosed in DE 22 23 762 A and EP 0 011 983 A1.

[0004] When fuel cell systems are switched off, water condenses on the system's piping and on the rotating parts of the fan, such as bearings, shaft, and impeller, at low ambient temperatures. If the fuel cell system is restarted, excessive ice bridge formation can cause the motor to seize, making starting the system difficult, delayed, or even completely impossible.

[0005] To solve this problem, it was initially proposed to drive the water out of the system using a dry purge gas. Such a method is described, for example, in DE 103 14 820 A1.

[0006] To prevent the need to transport additional purge gases, which leads to undesirable additional costs, especially in mobile applications, various methods have been developed to prevent or break up ice bridge formation without the use of additional purge gases. A distinction must be made between methods that aim to eliminate ice formation before the system is started and those that perform corresponding procedures when the system is shut down.

[0007] Alternatively, to avoid increased procedural effort, it is known to prevent ice bridge formation through appropriate structural adjustments.

[0008] For example, DE 10 2009 053 499 A1 describes a fuel cell system with an anode gas circuit in which an integrated liquid separator is arranged on the blower and can be emptied via a line. However, it does not disclose how this separator can be specifically implemented on the blower.

[0009] A specific design of an anode gas recirculation blower in the form of a side-channel blower for preventing ice bridging is known from EP 2 168 193 B1. A channel leads from the cup-shaped area between the inlet and outlet of the blower towards a recess formed in the housing cover. A drain opening is centrally located in this recess, through which water can be discharged from the blower housing. While this prevents ice bridging between the side of the impeller facing the cover and the cover itself, it does not prevent ice bridging on the opposite side of the impeller, where water can still accumulate. Furthermore, additional lines are required for water drainage.

[0010] DE 10 2007 053 162 A1 also discloses a blower for a fuel cell system with a heated housing component designed to prevent ice bridging. This necessitates additional heating components, which consume additional energy.

[0011] The object of the invention is therefore to provide a blower for conveying hydrogen in a fuel cell system of a motor vehicle, which prevents the impeller of the blower from freezing on both sides without requiring additional components or increasing assembly effort. In particular, piping should be eliminated compared to known designs. Accordingly, hydrogen should be conveyed without a warm-up time immediately after the fuel cell system is started.

[0012] This problem is solved by a blower for conveying hydrogen in a fuel cell system of a motor vehicle with the features of main claim 1.

[0013] By positioning the flow casing cover geodesically below the impeller and having a closed surface facing the impeller, with a gap between this surface and a first impeller surface facing the cover, a water reservoir is created. This reservoir allows water from the entire flow casing to collect without coming into contact with rotating parts. Furthermore, the cover surface is funnel-shaped, at least in sections, with the radial interior of the surface geodesically positioned at the lowest point. Consequently, the water collects centrally below the shaft end of the drive shaft. This allows the blower to start immediately when the fuel cell system starts up, eliminating the need for additional drainage.

[0014] Preferably, the impeller has an inclined second impeller surface facing away from the cover surface, wherein the inclined second impeller surface is fluidically connected to the intermediate space via at least one through-opening. Thus, the water that is located on the top of the impeller or between the impeller and the second flow housing part attached to the cover after the fuel cell system is switched off can flow across the inclined surface to the through-opening and from there through the through-opening to the intermediate space, i.e., into the water reservoir, so that ice bridge formation between the top of the impeller and the housing is reliably prevented.

[0015] In a further embodiment, at least one through-opening is formed at a geodetically lowest position of the inclined second impeller surface, thereby ensuring that the water present on the top side can flow into the space as completely as possible.

[0016] It is particularly advantageous if three through-openings evenly distributed around the circumference are formed on the wheel, so that, regardless of any inclination of the vehicle, a large part of the water flows into the space forming the water reservoir.

[0017] Preferably, the inclined second impeller surface is funnel-shaped essentially up to a central impeller hub, with the transition from the funnel-shaped surface to the impeller hub forming the lowest geodetic position of the second impeller surface. Accordingly, the impeller surface acts as a water collector, with openings formed at its lowest point to allow water to flow off the surface.

[0018] In a particularly advantageous embodiment, the volume of the intermediate space, formed geodetically entirely below the impeller, is larger than the volume of water expected in the flow casing after the fuel cell system is switched off. Such an expected water volume can be calculated by a person skilled in the art. By appropriately selecting the size of the intermediate space volume, it is ensured that the water does not come into contact with the impeller and thus no ice bridges can form between the water and the rotating parts.

[0019] In a further advantageous embodiment of the invention, the distance between an impeller surface facing the lid surface and the lid surface increases from radially outward to radially inward, and the lid surface is flat below the impeller hub. In the event of a slight incline of the vehicle, space is thus provided below the impeller for a constant volume of water without the water coming into contact with the impeller.

[0020] In order to store as much water as possible in the smallest possible space and at the same time avoid contact between the impeller and this water, the inclination of the impeller surface facing the lid surface corresponds to a maximum expected inclination of the flow housing, which occurs when the vehicle is in a correspondingly inclined position.

[0021] Additionally, the slope of the lid surface should be greater than the maximum expected slope of the flow housing, thus preventing water from flowing radially outwards.

[0022] Furthermore, it is advantageous if the volume formed entirely below the impeller in the space between the impeller and the water reservoir, at the maximum expected inclination of the flow housing, essentially corresponds to the volume formed in the space below the impeller when the flow housing is not inclined. This also ensures the smallest possible installation space despite the required water storage capacity and thus prevents ice bridge formation even when the vehicle is parked on an incline.

[0023] It is particularly preferred to design the blower as a side-channel blower, in which the inclined surfaces are arranged radially inside the impeller blades. Sufficient storage space is available in the side channels, so that ice bridging, which is usually a concern in side-channel blowers, occurs between the cover and the adjacent closed impeller surface, a problem prevented by this arrangement.

[0024] This creates a blower for conveying hydrogen in a vehicle's fuel cell system, which reliably prevents ice bridging between the impeller and the housing cover without requiring additional components or lines. This is achieved using a minimal amount of installation space. This function is maintained even if the vehicle is tilted, allowing for an immediate system restart.

[0025] An embodiment of a blower according to the invention for conveying hydrogen in a fuel cell system of a motor vehicle is described below with reference to the figures. Fig. Figure 1 shows a section of a side view of a blower according to the invention in a cutaway representation. Fig. Figure 2 shows a perspective interior view of the flow housing cover of the blower according to the invention. Fig. 1. Fig. Figure 3 shows a perspective view of the impeller of the blower according to the invention. Fig. 1.

[0026] The one in Fig. Figure 1 shows a blower for the recirculation of hydrogen in the anode gas circuit of a fuel cell system, consisting of a two-part flow housing 10, which comprises a bearing housing 12 in which a drive shaft 14 of the blower is mounted, and a flow housing cover 16. The flow housing cover 16 has an annular projection 18 at its axial end facing the bearing housing 12 in the radially outer region, which engages the axial end of the bearing housing 12 facing the flow housing cover 16.In the area radially adjacent to the annular projection 18, the flow housing cover 16 has a contact surface 20 for the bearing housing 12. This surface, like the corresponding contact surface of the bearing housing, has at least one bore 22 in which a pin 24 is arranged. This pin 24 provides pre-fixation of the flow housing cover 16 to the bearing housing 12, thus defining the rotational position of the two flow housing parts 12 and 16 relative to each other. The flow housing cover 16 is fastened to the bearing housing 12 by several axial screws 26 in the area of ​​the annular projection 18.

[0027] On the side of the flow housing cover 16 facing away from the bearing housing, several additional threaded blind holes 28 are provided, through which the blower is attached to the vehicle. This attachment is always arranged such that, in the horizontal position of the vehicle in which the fuel cell system is located, the axis of the drive shaft 14 is also vertical and the flow housing cover 16 is geodesically positioned below the bearing housing 12.

[0028] The flow housing cover 16 has an inlet 30 which is fluidically connected via two inlet openings 32, 34 to two conveying channels 36, 38. The first of these conveying channels 36 is a side channel formed in the bearing housing 12, the second is a side channel 38 formed in the flow housing cover 16. Both conveying channels 36, 38 extend in a known manner over a large part of the circumference of the flow housing 10 to an outlet opening 40, which is formed both in the annular projection 18 of the flow housing cover 16 and in the radially adjacent boundary wall 42 of the bearing housing 12. Accordingly, the second inlet opening 34, which opens into the side channel 38 of the flow housing cover 16, is formed in the annular projection 18, while the first inlet opening 32 penetrates both the annular projection 18 and the boundary wall 42 of the bearing housing 12.An outlet 44 extending from the outlet opening 40 is provided in the flow housing cover 16.

[0029] A hub 46 of an impeller 48 of the blower is attached to the end of the drive shaft 14, which is located in the Fig.Figure 3 shows the impeller 48 located between the bearing housing 12 and the flow housing cover 16. On its radially outer region, the impeller blades 50 interact in a known manner with the two axially opposite conveying channels 36, 38 in the installed state. As the impeller 48 rotates, a helical flow occurs through the spaces between the blades and the opposite conveying channel 36, 38 between the inlet 30 and the outlet 44. This flow is interrupted by a breaker section 52, in which the walls facing the impeller 48 are formed directly adjacent to the impeller 48. This increases the flow resistance to such an extent that the conveyed fluid can no longer flow through the conveying channels 36, 38, but instead exits the flow housing 10 via the outlet 44.

[0030] The radially outer impeller blades 50 are connected to the impeller hub 46 via an impeller disc 54 with a first impeller surface 56, which faces the flow housing cover 16 and a second impeller surface 58, which faces the bearing housing 12.

[0031] According to the invention, the second impeller surface 58 is designed with an inclination towards the impeller hub 46, so that water present on the second impeller surface 58 flows towards the impeller hub 46 due to gravity. The hub is geodesically positioned lower than the impeller blades 50, thereby achieving the inclination of the impeller surface 58 according to the invention. The impeller surface 58 thus has a funnel shape, so that the water collects radially inside.

[0032] In this area adjacent to the impeller hub 46, three through-openings 60 are formed, evenly distributed around the circumference of the impeller 48, which penetrate the impeller 48 axially from the second impeller surface 58 to the first impeller surface 56. It follows that the water collected on the second impeller surface 58 flows through the through-openings 60 into a space 62 between the first impeller surface 56 and a cover surface 64 facing the impeller.

[0033] This cover surface 64, formed axially below the disk 54 of the impeller 48, is also inclined on all sides towards the center, i.e., funnel-shaped, with the inclination being greater than that of the first impeller surface 56, so that the axial distance between the impeller surface 56 and the cover surface 64 increases in the direction of the axis of rotation up to the impeller hub 46. Below the impeller hub 46 at its lowest geodetic point, the cover surface 64 is flat, i.e., it extends essentially perpendicular to a gravitational force vector.

[0034] Due to this arrangement and shape, water from the second impeller surface, water from the first impeller surface that drips onto the cover surface, and water present in the outer area of ​​the cover surface after the fuel cell and blower have been switched off all collect in the radially inner area of ​​the space 62, which thus serves as a water reservoir. The distance between the cover surface 64 and the first impeller surface 56, and between the drive shaft 14 and the impeller hub 46 and the flat surface of the cover surface 64, is chosen such that the volume between the water-covered cover surface and the water level is always below the rotating parts, i.e., the drive shaft and the impeller 48.

[0035] For this purpose, the maximum expected amount of water is calculated that can accumulate in an anode gas circuit after the fuel cell system is switched off, due to condensation of the water vapor normally present in the anode gas circuit in the blower, and which can freeze there at temperatures below freezing. This calculated volume is then provided accordingly in the intermediate space.

[0036] It should also be noted that a parked vehicle may be parked on a slope, i.e., tilted in one direction, which also tilts the axis of the blower. As a result, the water surface of the water collected in the space 62 is no longer parallel to the flat surface below the impeller hub 46, but inclined to it. Accordingly, the inclination of the cover surface 64 and the distance of the impeller surface 56 to the cover surface 64 are adjusted so that, even with a given maximum inclination to the gravitational force vector, the volume available for the water corresponds to the volume of the maximum amount of water that condenses, without any rotating parts coming into contact with it.For this to happen, it is necessary that the inclination of the lid surface is at least slightly greater than the expected vehicle inclination and that the distance between the first wheel surface and the lid surface increases towards the center.

[0037] This creates a blower for conveying hydrogen in a vehicle's fuel cell system. After the fuel cell is switched off, the water that condenses in the blower is completely captured and collected in the flow housing cover, without the water coming into contact with the shaft or impeller. This prevents ice bridges from forming between stationary and rotating parts of the blower at low temperatures. When the fuel cell system restarts, the blower can be started normally without having to overcome any clamping force. The water collected in the blower then evaporates or is transported out of the blower.

[0038] It should be clear that the scope of protection of the main claim is not limited to the described embodiment. Such blowers can be advantageously used wherever problems due to ice bridging are expected, for example, in the transport of humid air. Furthermore, the angles of inclination and shapes of the parts forming the water reservoir can be modified without departing from the scope of protection of the main claim. Other design modifications are also conceivable.

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