DE102020108650A1 - Ejector - Google Patents

Abstract

The invention relates to an ejector with a suction nozzle (100) and a propulsion nozzle (102), with a needle (108) which is arranged within the propulsion nozzle (102) and axially adjustable along a longitudinal axis of the needle and is designed to set a flow cross-section of the propulsion nozzle (102) , for which purpose the needle (108) comprises a needle body (106) with a body section (110) tapering to a needle point (122), and with a heating means for heating an ejector part. The heating medium is introduced into the needle body (106) or the needle body (106) forms part of the heating medium.

Description

The invention relates to an ejector, in particular an ejector for a fuel cell system, with a suction nozzle and a propulsion nozzle, with a needle arranged within the propulsion nozzle and axially adjustable along a needle longitudinal axis, which is designed to set a flow cross-section of the propulsion nozzle, for which purpose the needle has a needle body comprises a body portion tapering to a needle point. The ejector also includes heating means for heating an ejector part.

Fuel cells use the chemical conversion of a fuel with oxygen into water to generate electrical energy. For this purpose, fuel cells contain the so-called membrane electrode assembly (MEA for "membrane electrode assembly") as a core component, which is a composite of a proton-conducting membrane and an electrode (anode and cathode) arranged on both sides of the membrane. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane-electrode unit on the sides of the electrodes facing away from the membrane. As a rule, a fuel cell stack is formed by a large number of MEAs arranged in a stack, together with bipolar plates, the electrical powers of which add up. When the fuel cell is in operation, the fuel, in particular hydrogen H ₂ or a hydrogen-containing gas mixture, is fed to the anode, where an electrochemical oxidation of H ₂ to H ⁺ takes place with the release of electrons. ^{A (water-bound or anhydrous) transport of the protons H +} from the anode space into the cathode space takes place via the electrolyte or the membrane, which separates the reaction spaces from one another in a gas-tight manner and electrically insulates them. The electrons provided at the anode are fed to the cathode via an electrical line. Oxygen or an oxygen-containing gas mixture is fed to the cathode, so that a reduction of O ₂ to O ^2- takes place while absorbing the electrons. At the same time, these oxygen anions react in the cathode compartment with the protons transported across the membrane to form water. By converting chemical energy directly into electrical energy, fuel cells achieve improved efficiency compared to other electricity generators due to the bypassing of the Carnot factor.

Since the anode reaction is usually operated with a stoichiometric dimensioning of the fuel, there is no complete reaction of the entire fuel supplied in the fuel cell stack. Nor does a complete reaction of the oxygen take place. For efficient use of the fuel, it is therefore often fed (recirculated) into an anode circuit / anode loop, with the fuel being enriched again to such an extent that the fuel is again overstoichiometric and the reaction can take place before the fuel is returned to the fuel cell stack.

For this purpose, an ejector (suction jet pump) can be used in the anode circuit, which recirculates the anode gas from a fuel tank using the potential energy of the hydrogen. This makes it possible to dispense with a recirculation fan that requires more energy and space. However, the efficiency of an ejector depends heavily on its geometry and particularly on the size of the propellant nozzle and the size of the mixing tube. The optimum ejector geometry is dependent on the respective operating conditions of the fuel cell, which change during the operation of a vehicle, which is why controllable ejectors are known whose usable flow cross-section of the propellant nozzle can be changed by axially adjusting a needle.

If the fuel cell system is switched off, the axially adjustable needle typically completely closes the propellant nozzle, but for the desired tightness of the system, part of the needle body, in particular the needle tip, protrudes beyond the propellant nozzle and into the suction nozzle area. If water condenses on this part and freezes due to low temperatures, there is a risk that the needle can no longer be adjusted axially, which means that no fresh fuel can be supplied to the fuel cells and the fuel that has not been consumed in the fuel cells can not be recirculated.

To counter this problem, the DE 10 2004 002 021 A1 an adjustable ejector mentioned at the beginning, which is equipped with a heating device for heating its nozzle body. For this purpose, the heating device is arranged in an outer wall of the nozzle body.

In the JP 2006 169 977 A Also described are adjustable ejectors for a fuel cell system, which is equipped either with a PTC heating element attached to the outer wall of the nozzle body or with a line section also provided on its outer wall for the passage of heated coolant.

Furthermore also describes the JP 2006 294 347 A an adjustable ejector for a fuel cell system with a heating means arranged on the ejector housing, sensors being present to detect the temperature of the housing. In this way it can be determined whether the ejector needs to be heated.

It is therefore the object of the present invention to provide an ejector, the heating means of which provides the heating power in a more targeted manner at that point in that ejector area where it is required for the ejector to function properly.

This object is achieved by an ejector with the features of claim 1. Advantageous configurations with expedient developments of the invention are specified in the dependent claims.

The ejector according to the invention is particularly characterized in that the heating means is introduced into the needle body or the needle body forms part of the heating means.

In this way, the heating power can be provided directly where it is needed in the case of frost conditions, namely on the needle itself, so that any ice that may be present on the propellant nozzle or on the needle body is melted efficiently, quickly and effectively in a frost start mode . The frost start procedure is significantly shortened in the adjustable ejector according to the invention compared to the adjustable ejectors known from the prior art.

The heating means is preferably formed as an, in particular rod-shaped, electrical heating element which is inserted into a cavity in the needle body. By using an electrical heating element, the ejector can be kept compact, because there is usually an electrical supply for an actuator for adjusting the needle, which can be effectively supplemented by the electrical supply for the heating element.

A resistance heating element, for example, can be used as the heating element. Alternatively, the heating element can also be designed as a PTC heating element (PTC for “positive temperature coefficient”). The PTC heating element is a temperature-dependent resistor that conducts the current better at low temperatures than at high temperatures. Thus, the heating element is designed in such a way that heating only takes place when such is actually needed; especially at low temperatures or in case of frost.

In order to reduce or avoid the risk of a fuel leak, it is advantageous if the heating element is arranged in a fluid-tight manner insulated from those ejector areas in which or through which fuel flows during operation.

It is thus possible that the needle body also comprises a first section which is in contact with the fuel during operation of the ejector, and that the needle body comprises a second section which is complementary to the first section and which is not in contact with the fuel during operation of the ejector stands. In this way it is possible for the heating element to be introduced into or integrated into the needle body in such a way that no separate seal has to be provided for the heating element.

In addition, for additional safety, the needle body can preferably be adjusted axially guided through a fluid-tight passage. The leadthrough can be designed as a, in particular radial, bearing for the needle body. The implementation can also include at least one additional seal.

It is advantageous if the cavity is in the form of a longitudinal bore extending along the longitudinal axis of the needle. The heating element can be inserted into this longitudinal bore, with the result that the dimensions of the longitudinal bore are selected such that the heating element can be received in the longitudinal bore.

Alternatively, the cavity can also be in the form of a longitudinal slot extending parallel to the longitudinal axis of the needle, which can simplify the assembly of the ejector. Attention must be paid to the required tightness of those areas of the ejector in which fuel flows during operation of the ejector. Such a longitudinal slot can, however, also be used if a longitudinal bore has been selected for receiving the heating element, because then the longitudinal slot can be used for the passage of electrical lines for the electrical supply of the heating element.

For improved functionality of the heating element, it is advantageous if there are lines for the electrical supply of the heating element, which are connected at one end to a first connection pair of the heating element and the other end are connected to a second electrical connection pair.

The lines are led out of the cavity, for example at a coupling between the needle body and an axial control element of an actuator used to adjust the needle.

In a further development, however, the second electrical connection pair is present within the actuator used to adjust the needle. In this way, the ejector can be designed to be particularly compact, because the heating element can be supplied electrically with the actuator. It is avoided that the electrical lines of the heating element have to be led out of the ejector. The axial adjustment of the actuator for actuating the needle can, however, be independent of one The heating element is heated in order to not cause any parasitic power losses due to the then unnecessary heating with the heating element in normal operation - for example after completion of a frost start operation.

For example, a linear motor, a stepping motor or a magnetic actuator can be used as the actuator.

There is the possibility that the lines are led out of the hollow space of the needle and that the second connection pair is present in a connection sleeve that is closed on one side. This connecting sleeve can serve as a capsule from which no fuel can escape into the surroundings or the other constituents of the fuel cell system. The inner dimensions of the connecting sleeve are adapted to the outer dimensions of the needle so that the needle can at least partially penetrate into the connecting sleeve. In this way it is possible for the needle to be fully inserted into an ejector area in which fuel can be present during operation, because the connecting sleeve ensures the fluid-tight insulation of the heating element positioned in the cavity of the needle body. The connecting sleeve may have at least one further seal. In order to provide sufficient electrical insulation, the connecting sleeve is preferably formed from an electrically non-conductive material, for example from plastic.

For reasons of simplified assembly, however, there is the possibility that the connection sleeve is present as a “real” sleeve and thus not closed on one side. The connecting sleeve can then be assigned a sleeve cap which is applied, for example screwed or plugged, to the end of the connecting sleeve facing away from the needle tip. In this context, it makes sense if the lines are led out of the hollow space of the needle and if the second connection pair is present in the sleeve cap of the connection sleeve. This concept of the sleeve cap makes additional seals on moving parts of the electrical supply of the heating element obsolete.

The second connection pair is glued, cast, welded or pressed into the connection sleeve, which is closed on one side, or in the sleeve cap of the unclosed connection sleeve; if necessary, each with the aid of an additional seal. In this way, the contacts of the second connection pair are firmly and fluid-tightly introduced into the connection sleeve or in the sleeve cap.

There is the possibility that the heating means comprises at least one coil and is designed to inductively heat the needle body. In this way, the needle body itself becomes part of the heating means. It is advantageous if there is at least one second coil which is designed to axially adjust the needle body, which realizes a magnetic actuator for axially actuating the needle.

The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination, but also in other combinations or alone, without the scope of the Invention to leave. Thus, embodiments are also to be regarded as encompassed and disclosed by the invention, which are not explicitly shown or explained in the figures, but which emerge and can be generated from the explained embodiments by means of separate combinations of features.

• 1 eine Schnittansicht eines schematisch dargestellten Ejektors,
• 2 eine Schnittansicht eines schematisch dargestellten zweiten Ejektors,
• 3 eine Schnittansicht eines schematisch dargestellten dritten Ejektors,
• 4 eine Schnittansicht eines schematisch dargestellten vierten Ejektors, und
• 5 eine schematische Darstellung einer einseitig geschlossenen Anschlusshülse für einen Ejektor nach 4,
• 6 eine schematische Darstellung einer Anschlusshülse mit Hülsenkappe für einen Ejektor nach 4, und
• 7 eine Schnittansicht eines schematisch dargestellten fünften Ejektors.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and on the basis of the drawings. Show:

• 1 a sectional view of a schematically illustrated ejector,
• 2 a sectional view of a schematically illustrated second ejector,
• 3 a sectional view of a schematically illustrated third ejector,
• 4th a sectional view of a schematically illustrated fourth ejector, and
• 5 a schematic representation of a connection sleeve closed on one side for an ejector according to FIG 4th ,
• 6th a schematic representation of a connection sleeve with sleeve cap for an ejector according to 4th , and
• 7th a sectional view of a schematically illustrated fifth ejector.

In the 1 until 4th and 7th an ejector is shown which has a suction nozzle 100 , a propulsion nozzle 102 as well as a mixing tube 104 having. The ejector shown is connected to the mixing tube 104 also a diffuser 114 at. The propulsion nozzle 102 is fluid mechanically via a connection 116 connectable to a fuel storage device, not shown, so that through the connection 116 fresh fuel via the propellant nozzle 102 into the mixing tube 104 can be given. The suction nozzle 100 in contrast, has a connection 118 on, through which the recirculated fuel is introduced or sucked in, which was not consumed in a fuel cell stack not shown in detail.

Inside the propellant nozzle 102 , especially concentric to this, is a needle 108 arranged that a needle body 106 with a tapering towards the nozzle opening 120 the propulsion nozzle 102 rejuvenating body section 110 has that in a needle point 122 transforms. Also the propulsion nozzle 102 itself is facing towards the nozzle opening 120 tapered nozzle section 124 designed. Through the needle 108 a flow cross-section of the propellant nozzle 102 vary. For this is the needle 108 axially adjustable so that when the needle is adjusted 108 towards the nozzle opening 120 the flow cross-section of the propellant nozzle 102 is decreased. With an axial adjustment of the needle 108 in one of the nozzle openings 120 in the opposite direction, the flow cross-section is enlarged and a larger proportion of fresh fuel can enter the mixing tube 104 reach. To adjust the needle 108 is an actuator 112 provided, which is formed, for example, as a linear drive, as a stepper motor or as a magnetic actuator. Also the suction nozzle 100 is having a look towards the mixing tube 104 tapered nozzle section 126 educated. The flow cross-section of the mixing tube 104 is fixed in the present case. However, there is also the possibility that the flow cross-section can be varied by means of a suitable adjustment device.

The ejector according to the invention comprises a heating means for heating an ejector part, the heating means being in the needle body 106 is introduced or the needle body 106 itself forms part of the heating means.

With the ejector from the 1 until 4th is the heating means as an electrical heating element 128 formed into a cavity 132 of the needle body 106 is used. The cavity 132 is in the present case in the form of a longitudinal bore extending along the longitudinal axis of the needle. Alternatively, there is the possibility that the cavity 132 is in the form of a longitudinal slot extending parallel to the longitudinal axis of the needle, so that the heating element 128 laterally into the needle body 106 can be used. In both cases there is the possibility that the cavity 132 after inserting the heating element 128 is sealed and is then sealed, the electrical supply of the heating element 128 is maintained or guaranteed. Therefor there are lines for the electrical supply of the heating element 128 present, the one end at a first pair of connections 134 of the heating element 128 are connected and the other end to a second electrical connection pair 136 are connected.

The heating element 128 itself is arranged in a fluid-tight manner insulated from those ejector areas in which or through which fuel flows during operation.

Such isolation is evidenced by the ejectors 1 until 3 achieved in that the needle body 106 a first section which is in contact with the fuel during operation of the ejector, and a second section which is complementary to the first section and which is not in contact with the fuel during operation of the ejector. That's what the needle body is for 106 through a fluid-tight implementation 142 adjustable axially guided therethrough. The implementation 142 is present as a storage for the needle body 106 educated. The implementation 142 can also include at least one additional seal, as shown in FIG 2 is indicated illustratively.

In 1 are the lines on a coupling between the needle body 106 and an axial actuator one of the adjustment of the needle 108 serving actuator 112 out of the cavity 132 led out. The second pair of electrical connections 136 is therefore on the outside, on the ejector body, the lines being guided through the ejector body or the ejector housing in such a way that an axial adjustment of the heating element 128 along with the needle 108 remains possible without the two connection pairs 134 , 136 electrically separated from each other.

In 2 are the lines on one in the needle body 106 formed longitudinal slot from the cavity 132 led out so that the lines can "slide" within this slot when the needle 108 is adjusted axially. This embodiment dispenses with an additional clutch. The second electrical connection pair can also be used here 136 on the outside, on the ejector body, the lines being guided through the ejector body or the ejector housing in such a way that an axial adjustment of the heating element 128 along with the needle 108 remains possible without the two connection pairs 134 , 136 electrically separated from each other.

In 3 is the second pair of electrical connections 136 within the adjustment of the needle 108 serving actuator 112 before. Thus it can be used for the electrical supply of the heating element 128 the already existing electrical supply of the actuator 112 can be used, whereby it is ensured by a suitable interconnection that the electrical supply for the needle adjustment takes place independently of the electrical supply of the heating element.

A fluid-tight insulation of the heating element 128 is evidenced by the ejectors 4th and 7th achieved in that the lines from the cavity 132 the needle 108 are led out, and that the second pair of connections 136 in a connection sleeve 138 is present.

This connecting sleeve 138 can serve as a capsule from which no fuel can escape into the surroundings or the other constituents of the fuel cell system. The inside dimensions of the connecting sleeve 138 are based on the external dimensions of the needle 108 adapted so that this at least partially in the connecting sleeve 138 can penetrate. In this way it is possible for the needle 108 is completely introduced into an ejector area, in which fuel can be present during operation, because the connecting sleeve 138 ensures the fluid-tight insulation of the in the cavity 132 of the needle body 106 positioned heating element 128 . If necessary, the connecting sleeve 138 at least one other seal. In order to provide sufficient electrical insulation, the connecting sleeve 138 preferably formed from an electrically non-conductive material, for example from plastic.

In 5 is this connecting sleeve 138 designed as a monolith, closed on one side, the second pair of connections 136 at the bottom of the connection sleeve, which is closed on one side 138 is present.

In 6th is the connecting sleeve 138 a sleeve cap 140 assigned to that of the needle tip 122 remote end of the connecting sleeve 138 applied, for example. Screwed or plugged. The second pair of connections 136 is in the case cap 140 the connecting sleeve 138 arranged. Through this concept of the sleeve cap 136 are additional seals on moving parts of the electrical supply to the heating element 128 obsolete.

The second pair of connections 136 is in the connection sleeve, which is closed on one side 138 or in the sleeve cap 140 the unclosed connection sleeve 138 glued in, cast in, welded or pressed in; if necessary, each with the aid of an additional seal. This is how the contacts of the second pair of connections are 136 firmly and fluid-tight in the connecting sleeve 138 or in the sleeve cap 140 brought in.

In 7th an ejector is shown, its actuator 112 is designed as a solenoid actuator. So with that the needle 108 adjust axially by means of an electromagnet. In this embodiment, the heating means comprises at least one coil 130 and is designed the needle body 106 inductive heating. So this is how the needle body becomes 106 itself a component of the heating medium.

For reliable axial adjustment / resetting of the needle 108 and / or the heating element 128 is the needle 108 and / or the heating element 128 axially backwards, i.e. at the tip of the needle 122 remote side supported by a spring.

As a result, in the event of frost, the ejector according to the invention can be heated very quickly at the point where the heating power is required in order to melt any ice that may be present.

List of reference symbols

100

Suction nozzle

102

Propulsion nozzle

104

Mixing tube

106

Needle body

108

needle

110

Body section (tapering)

112

Actuator

114

Diffuser

116

Connection (fresh fuel)

118

Connection (recirculated fuel)

120

Nozzle opening (propulsion nozzle)

122

Needle point

124

Nozzle section (propulsion nozzle)

126

Nozzle section (suction nozzle)

128

Heating element

130

Coil (heating means)

132

cavity

134

first pair of connections

136

second pair of connections

138

Connecting sleeve

140

Sleeve cap

142

execution

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102004002021 A1 [0006]
• JP 2006169977 A [0007]
• JP 2006294347 A [0008]

Claims (10)

Ejector with a suction nozzle (100) and a propulsion nozzle (102), with a needle (108) arranged within the propulsion nozzle (102) and axially adjustable along a longitudinal axis of the needle, which is designed to set a flow cross-section of the propulsion nozzle (102), including the needle (108) comprises a needle body (106) with a body section (110) tapering to a needle point (122), and with a heating means for heating an ejector part, characterized in that the heating means is introduced into the needle body (106) or the needle body (106) forms part of the heating means. Ejector after Claim 1 , characterized in that the heating means is formed as an electrical heating element (128) which is inserted into a cavity (132) of the needle body (106). Ejector after Claim 2 , characterized in that the heating element (128) is arranged in a fluid-tight manner insulated from those ejector areas in which or through which fuel flows during operation. Ejector after Claim 3 , characterized in that the cavity (132) is in the form of a longitudinal bore extending along the longitudinal axis of the needle. Ejector after Claim 3 , characterized in that the cavity (132) is in the form of a longitudinal slot extending parallel to the longitudinal axis of the needle. Ejector according to one of the Claims 1 until 5 , characterized in that there are lines for the electrical supply of the heating element (128), which are connected at one end to a first connection pair (134) of the heating element (128) and the other end are connected to a second electrical connection pair (136). Ejector after Claim 6 , characterized in that the second pair of electrical connections (136) is present within an actuator (112) serving to adjust the needle (108). Ejector after Claim 6 , characterized in that the lines are led out of the cavity (132) of the needle (108), and that the second connection pair (136) is present in a connection sleeve (138) which is closed on one side. Ejector after Claim 6 , characterized in that the lines are led out of the cavity (132) of the needle (108), and that the second connection pair (136) is present in a sleeve cap (140) of a connection sleeve (138). Ejector according to one of the Claims 1 until 9 , characterized in that the heating means comprises at least one coil (130) and is designed to inductively heat the needle body (106).

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