WO2004020106A1

WO2004020106A1 - Device for collecting liquid from a two-phase fluid and fuel cell comprising one such device

Info

Publication number: WO2004020106A1
Application number: PCT/FR2003/002491
Authority: WO
Inventors: David Corgier; Luc Rouveyre
Original assignee: Renault S.A.S.
Priority date: 2002-08-30
Filing date: 2003-08-08
Publication date: 2004-03-11
Also published as: FR2843898B1; FR2843898A1

Abstract

The invention relates to a device that is used to collect liquid (10) contained in a two-phase fluid (14). The invention is of the type that comprises a rotating cylindrical casing (16) having an essentially vertical axis (A), which is closed at the top thereof by means of an upper transverse wall (18). The upper end (26) of said casing defines a first tangential hole (30) for the injection of the compressed two-phase fluid (14) while the base (20) thereof takes the form of a funnel that converges into a second lower axial hole (22) for the passage of the liquid (24). In addition, a third gas outlet (32) cuts through the aforementioned upper transverse wall (18) in an axial manner. Moreover, the invention is of the type in which the casing (16) is surrounded externally by a cooling circuit (48) which defines a fourth inlet (50) and a fifth outlet (52) for a cooling fluid. The invention is characterised in that the third gas outlet (32) is connected to means (54) of expanding gases which, after expansion, constitute the cooling fluid of the cooling circuit (48).

Description

Device for recovering liquid in a two-phase fluid and fuel cell comprising such a device

The invention relates to a device for recovering liquid, and in particular liquid water, contained in a two-phase fluid.

The invention relates more particularly to a device for recovering liquid, and in particular liquid water, contained in a two-phase fluid, of the type comprising a cylindrical envelope of revolution of generally vertical axis closed upwards by an upper transverse wall, of which an upper end defines a first tangential orifice for injection under pressure of the two-phase fluid, and the bottom of which has a funnel-shaped shape converging downwards into a second lower axial orifice for the flow of liquid, and defines a third orifice evacuation of gases axially passing through the upper transverse wall, and of the type in which the envelope is surrounded externally by a cooling circuit of the device which defines a fourth inlet port and a fifth outlet port of an external cooling fluid. The invention also relates to the application of such a device to a fuel cell of the type comprising a cathode and an anode supplied by a supply orifice, and in at least one of which circulates a two-phase flow under pressure which is discharged by an exhaust port. Fuel cells are used in particular to provide electrical energy necessary for the propulsion of motor vehicles. The fuel cell is then taken on board the vehicle.

A fuel cell consists mainly of two electrodes, an anode and a cathode, which are separated by an electrolyte. This type of battery allows the direct conversion into electrical energy of the energy produced by the following oxidation-reduction reactions: - an oxidation reaction of a fuel, or fuel, which feeds the anode continuously; and

- a reduction reaction of an oxidizer which feeds the cathode continuously. The fuel cells used to supply electrical energy on board motor vehicles are generally of the solid electrolyte type, in particular of polymer electrolyte. Such a cell uses in particular hydrogen (H ₂ ) and oxygen (0 ₂ ) as fuel and oxidizer respectively. Unlike thermal engines which reject with ies exhaust gas a non-negligible quantity of polluting substances, the fuel cell offers in particular the advantage of rejecting only water which is produced by the reduction reaction at the cathode. In addition, a battery of the type described above can use ambient air whose oxygen (0 ₂ ) is reduced.

The oxidizer is generally humidified before being injected at the cathode so that the membrane of polymer material is not damaged, for example by drying. This humidification operation is also applied to the fuel when. the latter emerges from the anode via an anode discharge orifice.

The water necessary for humidifying the membrane is generally recovered at the outlet of the cell, and in particular at the outlet of the cathode in which the reduction reaction produces water.

The recovery of water at the outlet of the cathode has the advantage of not having to frequently renew the water reserves of the vehicle. In addition, the vehicle does not need to be equipped with a large volume water tank if enough water can be collected to moisten the membrane.

In addition, the exhaust gases from the cathode are generally under pressure and pass through at least one turbine. The fact that the gases contain liquid water causes malfunctions such as for example cavitation effects in turbines.

To recover the water produced at the cathode, it is known to interpose coalescing filters in the cathode outlet stream. However, their efficiency is insufficient and liquid water remains in the exhaust gases of the cell. The vehicle must therefore be supplied with water frequently and malfunctions can occur in the turbines used to relax the exhaust gases. It is also known to use condensers instead of coalescing filters. These condensers use water in a closed circuit as heat transfer liquid. However, the heat to be dissipated being high, the water cooling system must be large in order for its efficiency to be satisfactory. This solution is therefore not applicable for a fuel cell on board a motor vehicle. A proposal in the same technical field has already been the subject of a patent EP 2002162021, in which the gases pass through a plurality of small tubes of a cooling chamber filled with water.

The object of the present invention is to provide a device and a method which could improve the recovery of liquid in a two-phase fluid and to provide a fuel cell comprising such a device. The present invention provides a device of the type described above, characterized in that the third gas discharge orifice is connected to gas expansion means, which after expansion constitute the external cooling fluid injected into the fourth inlet orifice of the cooling circuit. According to another characteristic of the invention, the gas expansion means comprise a turbine.

The invention also relates to a fuel cell of the type comprising a cathode and an anode supplied by a supply orifice and in at least one of which flows a flow pressure two-phase which is discharged through an exhaust port, characterized in that it comprises such a device, the battery exhaust port being connected to the tangential injection port of the device. According to another characteristic of the fuel cell, the mechanical energy produced by the expansion of the gases in the turbine is communicated to a compressor which is in particular intended to compress a feed gas, in particular from the cathode of the fuel cell. The present invention also provides in a vehicle a process for recovering liquid, and in particular liquid water, contained in a two-phase fluid, by a device comprising a cylindrical envelope of revolution of generally vertical axis closed upwards by an upper transverse wall. , the process operating by injecting two-phase fluid under pressure through a first tangential orifice defined by an upper end of said device; by flowing the liquid onto said device, the bottom of which has a funnel-shaped shape converging downwards by defining a second lower axial orifice; by evacuating the gases through a third gas evacuation orifice, of said device defining said third gas evacuation orifice passing through the upper transverse wall; by cooling the envelope surrounded externally by a cooling circuit of said device, which defines a fourth inlet port and a fifth outlet port of an external cooling fluid; by expanding the gases by gas expansion means connected to the third gas discharge orifice; and by injecting into the fourth inlet orifice of the cooling circuit, the gases which, after expansion, constitute the external cooling fluid. The method can include a step of gas expansion by a turbine.

The invention can be applied to a vehicle comprising said liquid recovery device, or said fuel cell, or else using said liquid recovery method. The present invention will be better understood from the study of an embodiment taken by way of nonlimiting example and illustrated by the appended drawings, in which:

- Figure 1 is a schematic view of a water recovery device produced according to the teachings of the invention which is shown in axial section along a vertical plane;

- Figure 2 schematically shows the water recovery device according to the section plane 2-2 of Figure 1;

- Figure 3 schematically shows the application of the water recovery device ia figure applied to a fuel cell;

- Figure 4 shows another application of the water recovery device to a fuel cell.

Figure 1 shows a liquid recovery device 1 0 for separating the liquid and gas phases of a two-phase fluid.

The recovery device 10 is here arranged at the outlet of the cathode 12 of a fuel cell. For the purposes of the description, only the cathode 12 of the fuel cell has been shown in FIGS. 1, 2 and 4.

The cathode 12 comprises in particular an exhaust orifice 13 of a two-phase fluid 14 comprising mainly oxidizer, and in particular air, and water in the state of vapor or liquid. The recovery device 1 0 is here intended to globally separate the water, in liquid phase, from the air.

The liquid recovery device 1 0 mainly comprises a cylindrical envelope of revolution 1 6 with a generally vertical axis A. The envelope 16 is delimited upwards by an upper transverse wall 18, and downwards by a bottom 20 in the form funnel which converges downwards into an axial plug 22 through which liquid 24, and in particular liquid water, is liable to flow. The upper part 26 of the axial wall 28 of the envelope 16 defines a tangential orifice 30 for injecting the two-phase fluid 14 inside the envelope 1 6. The tangential arrangement of the injection orifice 30 is intended to impart to the fluid 14 which is injected into the envelope 16, a vortex movement around the axis of revolution A.

This arrangement is illustrated in Figure 2. The injection orifice 30 being located in the upper part 26 of the casing 1 6, the fluid 14 follows a vortex current descending ie iong of the internal cylindrical axial wall 28, which is represented by the arrowed line referenced 14 ′ in FIGS. 1 and 2.

The upper transverse wall 1 8 defines an axial orifice 32 for discharging "dry" gases, that is to say no longer comprising any liquid. An internal tube 34 concentric with the envelope 16 extends from the discharge orifice 32 downward, generally up to halfway up the envelope 16. The tube 34 is open at its first upper end 36 which is connected to the discharge orifice 32, and at its second lower end 38. The tube 34 is intended to channel an eddying eddy current of "dry" gases 14 "leaving by the evacuation orifice 32 and to separate it of the downward swirling current of two-phase fluid 14 'injected through the injection orifice 30. The tube 34 will therefore be called an evacuation tube in the following description.

The device 10 also includes a cylindrical ring 40 which concentrically surrounds the lower end 38 of the evacuation tube 34. The ring 40 has a diameter intermediate between the diameter of the evacuation tube 34 and that of the envelope 16. The ring 40 is here fixed to the discharge tube 34 by means of four radial fins, two of which, 42 and 44, are shown in FIG. 1. The four fins 42, 44 do not, however, obstruct the passage of the fluid 14 between the ring 40 and the tube 34. The ring 40 is in particular intended to deflect the "dry" gases contained in the downward eddy flow of fluid 14 'directly towards the upward eddy current 14 ", that is to say towards the discharge tube 34. The axial wall 28 of the casing 1 6 is here surrounded on the outside by a closed cylindrical enclosure 48. The enclosure 48 is intended to contain an external fluid for cooling the axial wall 28 of the casing 1 6. For this purpose, the enclosure 48 has an inlet orifice 50 and an outlet orifice 52 for the cooling fluid The inlet orifice 50 is here located in an upper part of the cooling enclosure 48 and the outlet orifice 52 is located in a lower part of the cooling enclosure 48.

The gas evacuation orifice 32 is here connected to a turbine 54 by means of an evacuation pipe 56. The turbine 54 is in particular intended to relax the gases which, after expansion, are advantageously guided to the inlet orifice 50 of the cooling enclosure 48, by means of a cooling pipe 58. The gases are cooled in proportion to their pressure drop. They can thus be used as cooling fluid in the cooling enclosure 48. Thus the problem posed by the cooling of the cooling fluid does not arise because the cooling fluid is not reused, as is usually the case in a closed cooling circuit.

In another embodiment, not shown, the expansion of the gases before being led to the cooling enclosure 48 is carried out by an expansion means such as a back-pressure valve.

We will now describe the operation of the liquid recovery device 10 applied to the cathode 12 of the fuel cell. The cathode 12 rejects through the exhaust orifice 13 a two-phase fluid 14, in particular composed of liquid water, water vapor and air, at a pressure generally between 2 and 4 bars. This two-phase fluid 14 is directly injected into the injection orifice 30 of the casing 16.

FIG. 2 shows in arrowed lines the flow of injected two-phase fluid 14. The stream of pressurized fluid 14 follows the circular cylindrical shape of the internal axial wall 28 of the casing 1 6 and it then follows a downward swirl current 14 "ie iong of the axial wall 28 and around the evacuation tube 34, clockwise as shown in Figure 2.

The liquid water 24 is then projected against the axial wall 28 in the casing 1 6 in the form of drops of water by centrifugation effect. The water drops flow by gravity along the axial wall 28 to the bottom 20 of the casing 1 6. The water then flows through the bung 22 to a water tank 60.

The axial wall 28 is cooled by the cooling fluid circulating in the cooling enclosure 48 outside the envelope 16. Thus, the swirling water vapor adjacent to the axial wall 28 is cooled until reaching its dew point. The water vapor then condenses on the axial wall 28 and flows to the reservoir 60 via the bung 22.

The downward eddy current 14 "is generally divided into a first internal layer mainly consisting of" dry "gases and a second external layer which is denser because it still has elements in the liquid phase which are pushed towards the axial wall 28 by the centrifugal force. Thus, the first internal annular layer of the downward vortex current 14 "which is adjacent to the evacuation tube 34 rushes into the annular chamber between the ring 40 and the evacuation tube 34. This first layer is mainly made up of dry air. Arriving at level of the lower end 38 of the evacuation tube 34, a convection movement causes the downward vortex current "dry" 14 '"to take an upward vortex movement which enters the evacuation tube 34 which conducts the gas to the gas discharge orifice 32.

The second annular layer of downdraft 14 ', which is denser than the first, is adjacent to the axial wall 28 in the envelope 16 and it continues a downward movement until it reaches the bottom 20 of the envelope 16. The centrifugation effect which projects the water against the axial wall 28 therefore continues.

A convection movement entrains the fluid 14 now mainly consisting of air and, in a less significant proportion of water vapor, in an ascending eddy current 14 "adjacent to the vertical axis A in the direction of the lower end 38 from the evacuation tube 34 then to the gas evacuation orifice 32.

The “dry” gases are evacuated by the evacuation orifice 32 under a pressure of between 2 and 4 bars, and they are led to the turbine 54 at the outlet of which they are expanded. Their temperature then dropped in proportion to their pressure.

The cooled gases are then led to the cooling enclosure 48 in which they form cooling fluid. The cooled gases are then externally in contact with the axial wall 28 through which they cool the water vapor circulating inside the envelope 1 6. For this purpose, the axial wall 28 is advantageously made with a thermally material non-insulating, that is to say with good thermal conductivity.

Advantageously, the turbine 54 is mechanically connected to a pump 62, as shown in FIG. 3. The mechanical energy produced by the expansion of the gases thus makes it possible to pump the water contained in the tank 60 towards a device 64 which is intended for moisten the oxidizer upstream of the cathode 12. In another variant of application of the recovery device 10, the turbine 54 is associated with a compressor 66 which compresses the oxidizer upstream of the cathode 12 intended to supply the cathode 12 through a supply orifice 68. These applications are indeed sure given as nonlimiting examples. The mechanical energy produced by the expansion of the gases in the turbine 54 can thus be recovered for other applications.

Claims

1. Device for recovering liquid (10), and in particular liquid water (24), contained in a two-phase fluid (14), of the type comprising a cylindrical envelope of revolution (1 6) of generally vertical axis (A) closed towards the top by an upper transverse wall (18), of which an upper end (26) defines a first tangential orifice (30) for injection under pressure of the two-phase fluid (14), and the bottom (20) of which has a shape of funnel converging downwards into a second lower axiai orifice (22) for liquid flow (24), and defining a third gas evacuation orifice (32) axially passing through the upper transverse wall (1 8), and of the type wherein the casing (1 6) is surrounded externally by a cooling circuit (48) of the device (1 0) which defines a fourth inlet port (50) and a fifth outlet port (52) of a fluid external cooling, characterized in that the third orific e gas evacuation (32) is connected to gas expansion means (54), which after expansion constitute the external cooling fluid injected into the fourth inlet port (50) of the cooling circuit (48).

2. Device (10) according to the preceding claim, characterized in that the gas expansion means comprise a turbine (54).

3. Fuel cell of the type comprising a cathode (12) and an anode supplied by a supply orifice (68) and in at least one of which circulates a two-phase flow (14) under pressure which is evacuated by an exhaust orifice (13), characterized in that it comprises a device (1 0) according to any one of claims 1 or 2, the exhaust orifice (13) of the cell being connected to the tangential injection orifice (30) of the device (1 0).

4. Fuel cell according to the preceding claim, characterized in that the mechanical energy produced by the expansion of the gases in the turbine (54) is communicated to a compressor (66) which is in particular intended to compress a supply gas in particular of the cathode (1 2) of the fuel cell.

5. Method for recovering liquid, and in particular liquid water (24), contained in a two-phase fluid (14), by a device (10) comprising a cylindrical envelope of revolution (1 6) with a generally vertical axis ( A) closed upwards by an upper transverse wall (18), the process operating

- By injecting two-phase fluid (14) under pressure through a first tangential orifice (30) defined by an upper end (26) of said device (1 0);

- by flowing the liquid (24) on said device (1 0) whose bottom (20) has a funnel shape converging downwards by defining a second lower axial orifice (22);

- by evacuating the gases through a third gas evacuation orifice (32), said device (10) defining said third gas evacuation orifice (32) passing through the upper transverse wall (18);

- by cooling the envelope (1 6) surrounded externally by a cooling circuit (48) of said device (10), which defines a fourth inlet port (50) and a fifth outlet port (52) of a fluid external cooling;

- by expanding the gases by means of gas expansion (54) connected to the third gas discharge orifice (32); and

- by injecting into the fourth inlet orifice (50) of the cooling circuit (48), the gases which, after expansion, constitute the external cooling fluid.

6. Method according to claim 5, comprising a step of expansion of the gases by a reel (54).

7. Vehicle comprising a recovery device according to one of claims 1 or 2 or a fuel cell according to one of claims 3 or 4 or using a liquid recovery method according to one of claims 5 or 6.