WO2013045040A1

WO2013045040A1 - Gas jet pump for delivering a main gas stream

Info

Publication number: WO2013045040A1
Application number: PCT/EP2012/003909
Authority: WO
Inventors: Matthias Jesse; Thomas Winkeler
Original assignee: Daimler Ag
Priority date: 2011-10-01
Filing date: 2012-09-19
Publication date: 2013-04-04
Also published as: DE102011114716A1

Abstract

The invention relates to a gas jet pump (9) for delivering a main gas stream (A) using a metered propellant gas stream (H2), comprising a gas feed for the main gas stream (A), at least one nozzle (12) for the propellant gas stream (H2), an outflow region (19) for the mixed gas streams and an accelerating chamber (16), which is arranged in line with the outflow region (19) on the same axis (17) and into which the gas feed and the at least one nozzle (12) open out. The invention is characterized in that the at least one nozzle (12) opens out into the accelerating chamber (16) in the axial direction of the outflow region (19), and in that the at least one nozzle (12) is arranged in a central region of the accelerating chamber (16) lying opposite the outflow region (19), and in that the gas feed opens out into the accelerating chamber (16) substantially perpendicularly to the axial direction of the outflow region (19).

Description

Gas jet pump for conveying a main gas flow

The invention relates to a gas jet pump for promoting a main gas stream according to the closer defined in the preamble of claim 1. The invention also relates to the use of such a gas jet pump.

Gas jet pumps are known from the general state of the art. They are often referred to as pulse exchange machines, ejectors or, based on the English term, as a jet pump. They always serve to promote a main gas stream by acceleration and / or pressure build-up in the main gas stream is achieved via a propellant gas flow. The two gas streams then arrive mixed in the area in which they are to be promoted.

From the generic DE 10 2008 003 033 A1 is such

Impulse exchange machine for a gas supply system described. It consists of a gas supply for the main gas flow, which is referred to here as the main gas, and at least one nozzle for the propellant gas stream, which is referred to here as Zusatzgasdüse. The gas supply and the nozzle open into a common acceleration space, from which the gases mixed out flow through a discharge area again. The nozzles are arranged in the prior art shown here so that they in particular evenly around the gas supply of the

Main gas stream are arranged distributed and are injected with at least one direction component in the flow direction of the main gas stream. This results in a momentum exchange between the particles of the supplied via the nozzle

Propellant gas stream and the main gas stream, whereby the main gas stream is accelerated. The gas streams then go together after the acceleration space in a discharge area. Now, the inventors have shown that the structure described in the generic state of the art has a decisive disadvantage. Presumably, this is because the propellant gas flow is parallel to the walls of the gas supply of the

Main gas flow is aligned and thus close to the walls of the

Acceleration space flows. As a result, frictional forces between the

Propellant gas flow and the wall of the acceleration chamber, which reduce the effect and thus the transmitted to the main gas flow acceleration

or belittle the pressure build-up generated in the region of the main gas flow.

The object of the present invention is now to avoid this disadvantage and to provide a highly efficient gas jet pump.

According to the invention this object is achieved by the features mentioned in the characterizing part of claim 1. Further advantageous embodiments of

solution according to the invention arise from the remaining dependent

Subclaims and from the inventive use of the gas jet pump.

The gas jet pump according to the invention is now constructed as a pulse exchange machine so that the at least one nozzle in the axial direction of the outflow area opens into the acceleration chamber. It also opens in a region of the acceleration chamber opposite the outflow region. This is

ensures that the comparatively energy-intensive propellant gas flows centrally and far away from the walls of the at least one nozzle

Acceleration space in these open. The main gas stream is then in

Substantially perpendicular to the axial direction of the discharge area in this

Acceleration space supplied. In particular, this acceleration space may be formed as an annular space open in the circumferential direction, which on all sides of the

Main gas flow is flowing around. This design, with a central injection of the propellant gas stream or streams oriented perpendicular to the main gas stream, achieves the maximum pressure build-up or the maximum acceleration of the main gas stream, since negative influences on the propellant gas stream, such as friction with the

Walls of the acceleration space, can be avoided. It has been shown that with the gas jet pump according to the invention a significantly higher pressure build-up is possible, as with the generic described above

Impulse exchange machine.

In a further very favorable and advantageous embodiment of the construction according to the invention, it is provided that the at least one nozzle has at least two nozzle openings. The use of several nozzle openings with a correspondingly small cross-section allows a comparatively high

Flow rate of the added propellant gas flow through the use of several smaller nozzle openings. As a result, the energy input in the

Main gas flow further increased and it can be achieved a further improvement in flow rate.

In a further very favorable and advantageous embodiment thereof, it is further provided that the at least two nozzle openings are individually supplied with the propellant gas stream, wherein in at least one of the supply lines of the propellant gas stream to the individual nozzle openings, a valve device is arranged. Such

Valve means allows the driving of at least one of the nozzle openings separately from the one or the other. In principle, it is possible to do all of this

Equip nozzle openings with its own valve device. At least all of the nozzle openings may have one such valve device except for one. Then it is possible to adjust the volume flow so that for the idling operation of the metered through the nozzle opening volume flow is sufficient. Depending on the load condition and the required delivery rate, further nozzle openings can then be flown in, so that it is possible to regulate the power of the gas jet pump easily and efficiently. In addition to the valve devices, which may be formed for example as simple solenoid valves, no moving parts are necessary here. The structure is therefore correspondingly simple and efficient. Since the solenoid valves can be arranged at a distance from the actual nozzle openings, a very compact construction of the gas jet pump itself is also possible. The solenoid valves can be arranged for example in a valve block outside of the gas jet pump, which is connected via corresponding supply lines to the individual nozzle openings.

In a further very favorable and advantageous embodiment of the gas jet pump according to the invention, it is provided that the nozzle openings are surrounded by an annular nozzle cap. Such an annular nozzle cap in Outside the nozzle around the nozzle openings allows the or the individual propellant gas streams after exiting the nozzle a certain distance, namely the distance that results from the axial extent of the nozzle cap to flow before they come into contact with the main gas stream. This ensures even better momentum exchange. In particular, however, this also ensures that any impurities or undesirable substances which are transported via the main gas stream, for example moisture entrained in the main gas stream, do not reach the area of the nozzle openings and thus can not pollute or clog them.

According to an advantageous embodiment thereof, it is further provided that the nozzle cap at least one opening perpendicular to the flow direction of the

Propellant gas stream has. Such an opening, such as a notch or the like, can also counteract contamination, for example, by in the interior of the nozzle cap collecting water, which is typically unavoidable due to slight backflow in the nozzle cap, can pass through this opening.

The gas jet pump according to the invention can be constructed highly compact and allows a very efficient delivery of a main gas stream via a dosed

LPG stream. This construction is especially for use in

Suitable fuel cell systems in which exhaust gas is to be promoted as a main gas stream via a metered educt for the fuel cell as a propellant gas stream. This is particularly suitable for a cathode or anode recirculation in one

Fuel cell system.

The particularly preferred use lies in the use of the gas jet pump according to the invention in the region of an anode recirculation of a fuel cell system. In particular, in fuel cell systems, which are used in vehicles for generating electric drive power, is an energy-efficient and

Reliable recirculation of anode exhaust gas, if used, is of crucial importance. The compact and simple construction is decisive. All this can be realized by the gas jet pump according to the invention, since this can be realized extremely compact with high flow rate. It is therefore particularly suitable for the specified use. Further advantageous embodiments of the gas jet pump according to the invention will become apparent from the remaining dependent claims and together with a fuel cell system according to the invention with reference to the following

Embodiment described in more detail.

Showing:

1 shows an exemplary fuel cell system in a vehicle. and

Fig. 2 is a sectional view from above through a gas jet pump according to the invention.

In the representation of FIG. 1, a fuel cell system 1 in an indicated vehicle 2 can be seen purely by way of example and in a very highly schematic manner. The

Fuel cell system 1 essentially has a fuel cell 3, which in turn has an anode compartment 4 and a cathode compartment 5. The fuel cell 3 should be designed as a stack of PEM fuel cells. The cathode compartment 5 of the fuel cell 3 is supplied via an air conveyor 6 with air as an oxygen supplier. The exhaust air from the cathode chamber 5 passes in the illustrated here

Embodiment to the environment. Here, in principle, a post-processing, for example, an afterburner, a turbine or the like could be arranged. However, this is not of interest for the present invention, so that a representation has been omitted.

The anode chamber 4 of the fuel cell 3 is supplied with hydrogen H ₂ , which originates from a compressed gas reservoir 7. From the region of the anode chamber 4, exhaust gas A passes from the anode chamber 4 via a recirculation line 10 back into the area of the gas jet pump 9, and is considered to be secondary therefrom by means of a pressure regulating device 8 and a gas jet pump 9 explained in greater detail below Aspirated gas stream and fed back into the anode chamber 4. This principle of an anode recirculation is known from the general state of the art. It serves to the anode chamber 4 with an excess

Hydrogen H ₂ supply in order to make the best possible use of its active area. The remaining in the exhaust gas from the anode chamber 4 residual hydrogen is then together with inert gases, which through the membranes from the cathode compartment 5 in the

Anodenraum 4 are diffused and a small part of the product water, which arises in the anode chamber 4, fed back via the recirculation line 10 and the Anode space 4 mixed with the fresh hydrogen H ₂ supplied again. Since in such an anode recirculation over time, inert gases and water accumulate and thereby the hydrogen concentration decreases, it is necessary, for example from time to time, to discharge water and gas from the anode recirculation. For this purpose, a drain valve 11 is indicated in principle in the illustration of FIG.

In order now to the pressure losses in the region of the anode compartment 4 and in the region of

It is necessary to compensate a recirculation line 10

Provide recirculation conveyor for the recirculated exhaust gas from the anode compartment 4. As a recirculation conveyor is shown in the here

Embodiment of Figure 1, the aforementioned gas jet pump 9 is provided.

In the illustration of Figure 2, this can be seen in a sectional view in view from above the intended use. The gas jet pump 9 consists of a nozzle 12, which is fed here via two separate supply lines 13, and ideally in each case separate valve devices 14, hydrogen H ₂ from the compressed gas storage 7 as a primary gas stream. Via nozzle openings 15, this hydrogen H ₂ passes from the nozzle 12 into an acceleration space 16, which is designed substantially as a cylindrical disk about a central axis 17 of the gas jet pump 9. This design of the gas jet pump 9 designed as a pulse exchange machine thus differs significantly from the structure of a "sucking" gas jet pump, which is a Venturi tube with a cross-sectional constriction and a subsequent

Cross-sectional widening uses to build a vacuum and so suck the recirculated exhaust gas.

The acceleration space 16 is open at one or more locations around its circumference and communicates with an exhaust stream A from the anode chamber 4 and the recirculation line 10, respectively. The structure may in particular be such that the acceleration space 16 is designed in the form of a cylindrical disk which is open on the circumference. Via a taper 18, the acceleration space 16 then merges into an outflow region 19, which is formed with a constant cross section. The acceleration chamber 16 and the outflow region 19 are formed in alignment with each other about the central axis 17 of the gas jet pump 9. On the side facing away from the discharge area 19 of the acceleration chamber 16 while the nozzle 12 is arranged. This is arranged centrally, so that through the nozzle openings 15th exiting propellant gas flows in the central region, arranged around the axis 17, to flow into the acceleration space 16. Perpendicular to flows through one or more openings in the peripheral region of the acceleration chamber 16, the exhaust stream A from the anode chamber 4 a. By the propellant gas streams from the nozzle openings 15 of this main gas stream of the anode exhaust gas A is correspondingly accelerated, as it comes to an exchange of pulses between the main gas stream A and the or the propellant gas streams. The structure thus enables an acceleration of the main gas flow A or a pressure build-up in the main gas flow and can promote the two gas flows mixed via the outflow region 19 back to the anode compartment 4.

In particular, in a fuel cell system 1, it is now so that by the

Exhaust stream A moisture and water droplets can be entered into the acceleration chamber 16. To wetting the nozzle openings 15 and the risk of freezing of the nozzle openings 15 after stopping the

Fuel cell system 1 at temperatures below freezing, to prevent, in the area of the nozzle 12 an optional nozzle cap 20 is provided. The nozzle cap 20 shields an outlet region 21 of the hydrogen H ₂ from the main gas stream A. It is formed substantially annular and surrounds the outlet region 21 so that the flowing through the recirculation lines 10 exhaust gas A is deflected from this area. From the exhaust gas A with transported water is thereby kept away from the critical outlet area 21, in which it could clog the nozzle openings 15 and freeze in their area.

This task of keeping liquid away from the exit region 21 of the nozzle 12 fulfills the nozzle cap 20 with its annular structure very efficiently and with very simple structural means. However, such a nozzle cap 20 typically causes dead zones of the flow within the nozzle cap 20, which in turn may lead to water accumulation in the region of these dead zones. In order to prevent this, in the case of the nozzle cap shown in FIG. 2, in the intended use in the direction of gravity, an opening 22 is arranged at the bottom, which is embodied here as a notch tapering in the direction of the outlet region 21. On the one hand, this opening 21 prevents the formation of dead zones in the flow and, on the other hand, allows the water collecting in the interior of the annular nozzle cap 20 to escape. Since the opening 21, if only one is present, in the direction of gravity in the

arranged according to the intended use, the water can through the Expire gravity. Further openings 22 around the circumference of the nozzle cap 20 are in principle conceivable and possible, they then serve not only the water drain, but also the reduction of dead zones of the flow.

Claims

claims

1. Gas jet pump (9) for conveying a main gas stream (A) by a

dosed propellant gas stream (H ₂ ) with a gas supply for the main gas stream (A), at least one nozzle (12) for the propellant gas stream (H ₂ ), a discharge area (19) for the mixed gas streams and a flush to the outflow area (19) on the same Axis (17) arranged acceleration space (16) into which the gas supply and the at least one nozzle (12) open,

characterized in that

the at least one nozzle (12) opens into the acceleration chamber (16) in the axial direction of the outflow region (19), and that the at least one nozzle (12) is arranged in a central region of the acceleration chamber (16) opposite the outflow region (19), and that the gas supply in

Essentially perpendicular to the axial direction of the discharge area (19) opens into the acceleration space (16).

2. gas jet pump (9) according to claim 1,

characterized in that

the at least one nozzle (12) has at least two nozzle openings (15).

3. gas jet pump (9) according to claim 2,

characterized in that

the at least two nozzle openings (15) are individually supplied with the propellant gas stream (H ₂ ), wherein a valve device (14) is arranged in at least one of the supply lines (13) of the propellant gas stream (H ₂ ) to the individual nozzle openings (15).

4. gas jet pump (9) according to claim 1, 2, or 3,

characterized in that

the flow-through cross section tapers in the area (18) of the transition from the acceleration space (16) to the discharge area (19).

5. gas jet pump (9) according to one of claims 1 to 4,

characterized in that

the outflow region (19) has a constant flow-through cross-section.

6. gas jet pump (9) according to one of claims 2 to 5,

characterized in that

the nozzle openings (15) are surrounded by an annular nozzle cap (20).

7. gas jet pump (9) according to claim 6,

characterized in that

the nozzle cap (20) at least one opening (22) perpendicular to

Flow direction of the propellant gas stream (H ₂ ).

8. gas jet pump (9) according to one of claims 1 to 7,

characterized in that

the acceleration space (16) substantially as cylindrical in

Circumferentially formed outward open space.

9. The use of the gas jet pump (9) according to one of claims 1 to 8, in a fuel cell system (1) for recirculation of exhaust gas from a fuel cell (3) of the fuel cell system (1), wherein the exhaust gas (A) forms the main gas stream and one of Fuel cell (2) supplied educt forms the propellant gas stream.

10. Use according to claim 9,

characterized in that

the exhaust gas (A) is formed by the anode exhaust gas of the fuel cell (3), and that the propellant gas stream is formed by hydrogen (H ₂ ).