FR2843898A1 - DEVICE FOR RECOVERING LIQUID FROM A DIPHASIC FLUID AND FUEL CELL COMPRISING SUCH A DEVICE - Google Patents

Abstract

The invention relates to a device for recovering liquid (10) contained in a two-phase fluid (14), of the type comprising a cylindrical envelope of revolution (16) of generally vertical axis (A) closed at the top by an upper transverse wall (18 ), an upper end (26) of which has a tangential orifice (30) for injecting the compressed two-phase fluid (14), and the bottom (20) of which has a funnel shape converging into a lower axial orifice (22) d liquid flow (24), and comprising a gas discharge orifice (32) axially passing through the upper transverse wall (18), and of the type in which the envelope (16) is surrounded externally by a cooling circuit ( 48) comprising an inlet orifice (50) and an outlet orifice (52) for a cooling fluid, characterized in that the gas evacuation orifice (32) is connected to gas expansion means (54), which after expansion constitute the fluid of r cooling of the cooling circuit (48).

Description

! "Device for recovering liquid in a two-phase fluid and battery

  with a fuel 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 with a generally vertical axis closed towards i0 upwards by an upper transverse wall, one upper end of which has a tangential orifice for injection under pressure of the two-phase fluid, and whose the bottom has the shape of a funnel converging downwards into a lower axial liquid flow orifice, and comprising a gas evacuation orifice 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 comprises an inlet port and an outlet port for a fluid ex dull cooling. 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 through 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 loaded

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 redox 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.

  Fuel cells used to provide energy

  electric on board motor vehicles are generally of the solid electrolyte type, in particular a polymer electrolyte.

  Such a cell uses in particular hydrogen (H2) and oxygen (02) as fuel and oxidizer 10 respectively.

  Unlike heat engines which reject a significant quantity of polluting substances with the exhaust gases, the fuel cell offers in particular the advantage of only rejecting water which is produced by the reduction reaction at the cathode. In addition, a battery of the type described above can use ambient air including oxygen

(02) is reduced.

  The oxidant is generally humidified before being injected into 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 outlet.

  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 the 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 10 must therefore be frequently supplied with water and there may be malfunctions in the turbines used to expand

the exhaust gas.

  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.

  To solve these problems, the invention proposes a

  device of the type described above, characterized in that the gas discharge orifice is connected to gas expansion means, which after expansion constitute the external cooling fluid injected into the inlet opening of the cooling circuit .

  According to another characteristic of the invention, the means

  gas expansion valves have 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 two-phase pressurized flow which is discharged by an exhaust orifice, characterized in that that it includes such a device, the exhaust port of the battery being connected to the orifice

  tangential of injection 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 supply gas in particular from the cathode of the fuel cell. Other features and advantages will become apparent

  during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings

  among 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 shows schematically the application of the water recovery device of the figure applied to a fuel cell; - Figure 4 shows another application of the device

  to recover water from a fuel cell.

  Figure 1 shows a liquid recovery device 10 for separating the liquid and gaseous phases of a

two-phase fluid.

  The recovery device 10 is here arranged at the outlet

  cathode 12 of a fuel cell. For the purposes of the description, only the cathode 12 of the fuel cell has been

  shown in Figures 1, 2 and 4.

  The cathode 12 includes in particular an orifice

  exhaust 13 of a two-phase fluid 14 comprising mainly oxidizer, and in particular air, and water in the vapor or liquid state.

  The recovery device 10 is here intended to separate

  generally water, in liquid phase, from air.

  The liquid recovery device 10 mainly comprises a cylindrical envelope of revolution 16 of 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 of 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 has a tangential orifice 30 for injecting the two-phase fluid 14 inside the envelope 16. The tangential arrangement of the injection orifice 30 is intended to give the 0o fluid 14 which is injected into the envelope 16, a vortex movement around the axis of revolution A. This arrangement is illustrated in FIG. 2. The injection orifice 30 being located in the upper part 26 of the envelope 16, the fluid 14 follows a vortex current 15 descending along the internal cylindrical axial wall 28, which is represented by the arrowed line referenced 14 'in Figures 1 and 2. The upper transverse wall 18 has an orifice

  axial 32 for evacuating "dry" gases, that is to say containing no more liquid.

  An inner tube 34 concentric with the envelope 16 extends

  from the discharge port 32 downward, generally up to the height of the casing 16. The tube 34 is open at its first upper end 36 which is connected to the discharge port 25, and at its second lower end 38.

  The tube 34 is intended to channel a swirling upward current of "dry" gases 14 "leaving through the discharge orifice 32 and to separate it from the swirling downward current of two-phase fluid 14 'injected through the injection orifice 30 30 The tube 34 will therefore be called the evacuation tube in the following.

from the description.

  The device 10 also comprises 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 evacuation 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 vortex current of fluid 14 'directly towards the upward vortex current

  14 ", that is to say to the exhaust tube 34.

  The axial wall 28 of the casing 16 is here externally surrounded 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 16. For this purpose, I ' enclosure 48 has an inlet port 50 and an outlet port 52 for the cooling fluid. The inlet port 50 is here located in an upper part of the cooling enclosure 48 and the outlet port 52 is located in a lower part of the cooling enclosure

cooling 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 up to to the inlet orifice 50 of the cooling enclosure 48, via a

cooling manifold 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. case in a circuit of

cooling closed.

  In another embodiment, not shown, the expansion of the gases before being conducted to the enclosure of q 1 cooling 48, is carried out by an expansion means such

than 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 16 and it then follows a vortex current 15 descending 14 "along the axial wall 28 and around the tube

  34, clockwise according to Figure 2.

  The liquid water 24 is then projected against the axial wall 28 in the casing 16 in the form of drops of water by centrifugation effect. The drops of water flow by gravity along the axial wall 28 to the bottom 20 of the envelope 16. The water flows

  then via the drain 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 25 adjacent to the axial wall 28 is cooled until it reaches its dew point. The water vapor then condenses on the axial wall 28 and flows to the tank 60 by

through the plug 22.

  The downward eddy current 14 "is broadly divided into a first internal layer mainly consisting of" dry "gases and a second external layer which is denser because it also has elements in the liquid phase which are pushed towards the axial wall 28 by the

centrifugal force.

  7 l 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.

  level of the lower end 38 of the evacuation tube 34, a convection movement causes the downward "dry" vortex current 14 "to take an upward vortex movement which penetrates into the evacuation tube 34 which conducts the gas 10 to at the gas exhaust port 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 continues a downward movement until it reaches the bottom 20 of the envelope 16 The centrifugal effect which projects 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 upward vortex 20 "14" adjacent to the vertical axis A towards the lower end 38 from the drain tube 34 then to

the gas discharge orifice 32.

  The "dry" gases are evacuated through 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 16. For this purpose, the axial wall 28 is advantageously made with a thermally material non-insulating, i.e. 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 5 which is intended for moisten the oxidizer upstream of the cathode 12. In another variant of the application of the

  recovery 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 of course given by way of nonlimiting examples. The mechanical energy produced by the expansion of the gases in the turbine 54 can thus be recovered for other applications.

Claims (4)

  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 (16) with a generally vertical axis (A) closed upwards by an upper transverse wall (18), one upper end (26) of which has a tangential orifice (30) for injecting two-phase fluid under pressure (14), and the bottom (20) of which has a shape 10 funnel converging downwards into a lower axial liquid flow orifice (22), and comprising a gas discharge orifice (32) axially passing through the upper transverse wall (18), and of the type in which the casing (16) is surrounded externally by a cooling circuit 15 (48) of the device (10) which comprises an inlet orifice (50) and an outlet orifice (52) of an external cooling fluid, characterized in that the gas exhaust port (32)   is connected to gas expansion means (54), which after expansion constitute the external cooling fluid injected into the inlet orifice (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), 30 characterized in that it comprises a device (10) according to one   any one of claims 1 or 2, the exhaust port (13) of the cell being connected to the tangential injection port (30) of the device (10).   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 the cathode (12) of the fuel cell.   generally vertical A. The casing 16 is delimited upwards by an upper transverse wall 18, and downwards by a bottom 20 in the form of a funnel which converges downwards into an axial bung 22 through which liquid 24, and especially liquid water, is likely to flow. The upper part 26 of the axial wall 28 of the envelope 16 has a tangential orifice 30 for injecting the two-phase fluid 14 inside the envelope 16. The tangential arrangement of the injection orifice 30 is intended to give the fluid 14 which is injected into the envelope 16, a vortex movement around the axis of revolution A. This arrangement is illustrated in FIG. 2. The injection orifice 30 being located in the upper part 26 of the envelope 16, the fluid 14 follows a vortex current 15 descending along the internal cylindrical axial wall 28, which is represented by the arrowed line referenced 14 'in Figures 1 and 2. The upper transverse wall 18 has an orifice   axial 32 for evacuating "dry" gases, that is to say containing no more liquid.   An inner tube 34 concentric with the envelope 16 extends   from the discharge port 32 downward, generally up to the height of the casing 16. The tube 34 is open at its first upper end 36 which is connected to the discharge port 25, and at its second lower end 38.   The tube 34 is intended to channel a swirling upward current of "dry" gases 14 "leaving through the discharge orifice 32 and to separate it from the swirling downward current of two-phase fluid 14 'injected through the injection orifice 30 30 The tube 34 will therefore be called an evacuation tube in the following. from the 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