CN101482599A - Current distribution measuring method and apparatus for fuel cell - Google Patents

Abstract

The invention discloses a method and apparatus for measuring the fuel cell internal current distribution, belonging to the technical field of the clean energy proton exchanging film fuel battery test. When measuring the current distribution of the fuel cell, fixing the measuring control plate on the surface of the fuel cell; exerting the energized sine exciting current outputted by the exciting source on a energizing coil of a magnetic ring to generate a saturated alternating magnetic field in the magnetic ring; overlapping the magnetic field generated by the fuel cell interior distribution current on the magnetic ring to enable the excited waveform and harmonic of the magnetic field alternating-current component in the saturation state to be changed; obtaining the overlapped exterior magnetic field through measuring the change by the coil; then demodulating the current size of the area corresponding to the magnetic ring by the formula in the measuring principle. The method of the invention can be used for monitoring whether the local bad change exists or not, can prevent the fault and the danger of total current caused by overlarge local current density under normal range. The measuring apparatus has characteristics of simple structure, low cost and being easy to make.

Description

A kind of fuel cell current distribution measurement method and device

Technical field

The invention belongs to clean energy resource Proton Exchange Membrane Fuel Cells technical field of measurement and test, be particularly related to a kind of fuel cell internal current distribution measurement method and device, relating to specifically distributes to the Proton Exchange Membrane Fuel Cells internal current with the method in magnetic field measures.

Background technology

Proton Exchange Membrane Fuel Cells (PEMFC) is a kind of device that chemical energy is converted into electric energy.Here in conjunction with the accompanying drawings its structure and principle of work are briefly described:

As shown in Figure 1, Proton Exchange Membrane Fuel Cells is made up of parts such as membrane electrode and bipolarity collector plate.Wherein membrane electrode comprises PEM 101, cathode catalyst layer 102, cathode diffusion layer 103, anode catalyst layer 105, anode diffusion layer 106; Bipolarity collector plate (being called for short bipolar plates or collector plate) then is respectively cathode collector plate 104 and anode current collector plate 107, is used for conduction and water conservancy diversion.

Supply with fuel (hydrogen) by hydrogen inlet 109 anode during operation of fuel cells, supply with oxygenant (air) to negative electrode by air intake 108.Under the Pt catalyst action, hydrogen molecule is decomposed into hydrogen ion (proton) and electronics at anode catalyst layer 105, and hydrogen ion is moved to cathode side by PEM 101, produces electromotive force.When external load circuit was connected, electronics was then moved to negative electrode by external load circuit, and under the effect of cathod catalyst, airborne oxygen molecule absorbs electronics with the hydrogen ion that arrives at negative electrode, at cathode catalyst layer 102 water generation reactions.A series of reaction impels electronics constantly to flow through external circuit and exports electric energy.

Electrochemical reaction is carried out on the whole surface of diffusion layer, catalyst layer and PEM, so protolysis all has generation on whole PEM, and also just forming all has electric current to penetrate on the whole exchange membrane.In this process, because factors such as reacting gas concentration that catalyst distribution degree of uniformity, catalyst activity difference, flow field and diffusion layer consistance cause and pressure distribution difference, hydro-thermal skewness, each interlayer contact resistance maldistribution, all can influence the distribution of PEM both sides interfacial electrochemistry reaction, also just influence the penetrating current density (amount of charge that penetrates in the unit interval on the unit area) of inside battery each several part, that is to say that often there is uneven phenomenon in each regional distribution of current of fuel cell.

This unevenness of battery has limited fuel cell output power, may cause producing in the battery local inverse current, local temperature too high (local focus) in the time of serious, and PEM such as penetrates at problem.

Therefore, be necessary to study the measuring method and the on-Line Monitor Device of electric current distribution.

At present, Proton Exchange Membrane Fuel Cells internal current distribution measuring technology mainly contains following several:

People such as Liu Zhixiang have used sub-battery method to measure the distribution of Proton Exchange Membrane Fuel Cells internal current.This technology utilizes copper coin, anode carbon paper etc. to transform anode flow field board, anode diffusion layer and catalyst layer, and membrane electrode is assembled into monocell with having anode flow field board and the undivided cathode flow field plate that sub-battery cuts apart, carry out the dependence test of current density.This method complex manufacturing technology, difficulty of processing is big, and the cost of manufacture height uses inconvenience, and measurement mechanism can not be independent of original Proton Exchange Membrane Fuel Cells.

People such as Noponen have adopted to be cut apart the runner method and studies distribution of current.This technology is to adopt the PVC plastics as the flow field substrate, carves groove and packs the steel bar collected current at frosting.The shortcoming that the runner technology is cut apart in employing is: difficulty of processing is big, uses complexity, collaborates mutually between runner, can not be independent of the Proton Exchange Membrane Fuel Cells body.

Distribution of current is measured in the temperature field that people such as Partridge utilize the infrared sensor that is arranged on outside batteries to measure inside battery indirectly.Because there is thermal effect in electric current, so the inhomogeneous meeting of distribution of current causes the variation in temperature field.This method need be reequiped the seal casinghousing of battery, and employing can see through the material of infrared radiation, normally changes into and sees through ultrared windowpane.There are some shortcomings in this method: one, and glass intensity is low, fragility is big, need be careful its security; Its two because there is thermal inertia in material, electric current is very slow to the response speed of temperature, it postpones to be difficult to reflect the distribution of current of transient changing generally in level second.For on-line monitoring, just can not in time prevent for fault, often produce the consequence of destructive malfunction.

As seen, the shortcoming of above-mentioned these distributed current measuring methods mainly comprises:

(1) cost of manufacture height, difficulty of processing is big;

(2) use inconvenience;

(3) electrode of Proton Exchange Membrane Fuel Cells is transformed;

(4) measurement component is not a device that is independent of Proton Exchange Membrane Fuel Cells.

In order to address these problems, the author has proposed a kind of magnetic effect of electric current of utilizing and has measured method and the corresponding measurement mechanism that the Proton Exchange Membrane Fuel Cells internal current distributes.

Summary of the invention

The objective of the invention is to propose to utilize the magnetic effect of electric current to measure a kind of fuel cell internal current distribution measurement method and the device that the Proton Exchange Membrane Fuel Cells internal current distributes.It is characterized in that described fuel cell internal current distribution measurement method is to utilize Magnetic Sensor to measure the distribution situation of magnetic field and electric current; Concrete steps are:

1) the encapsulation soft magnetic material of no use of affirmation fuel cell, easy magnetization material are as cover plate; A plurality of Magnetic Sensors are arranged in certain plane parallel with fuel cell surface;

2) sensor and fuel cell enter duty, measure the Distribution of Magnetic Field of fuel cell surface;

3), resolve the distribution of current of fuel cell surface according to DISTRIBUTION OF MAGNETIC FIELD;

It is to open driving source that described sensor and fuel cell enter duty, and driving source output drive sinusoidal excitation electric current is added on the magnet ring field coil of Magnetic Sensor, produces in magnet ring and makes it saturated alternating magnetic field; Fuel cell is following in working order, and the magnetic field superposition that the distributed current of fuel battery inside produces influences the degree of saturation of magnet ring to the magnet ring field coil, causes that waveform and the harmonic wave of measuring the induced electromotive force in the coil change,

Induced electromotive force in the described measurement coil is delivered to data acquisition processing system by the measurement coil of magnet ring and is handled, by the magnetic induction density of any current element Idl in the generation of P point place

$\mathrm{dB}=\frac{{\mathrm{\μ}}_0}{4\mathrm{\π}}\frac{\mathrm{Idl}\sin \mathrm{\θ}}{r^{\′2}};$

Then alive I, length is that the magnetic induction density B that the carrying flow direct conducting wire of L produces at P point place is:

$B={\mathrm{\&mu;}}_r{B}_0=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="4"\; label="r\; I"\; filenames="A200810116164E00142.png"\; state="\{\{state\}\}">r</figure-callout>}}I}{4\mathrm{\&pi;r}}(\cos {\mathrm{\&theta;}}_1-\cos {\mathrm{\&theta;}}_2)$

μ wherein ₀Be permeability of vacuum, μ _rRelative permeability for magnetic medium.

Demodulate the size of current of magnet ring corresponding region.

Described fuel cell current apparatus for measuring distribution is included in to measure on the control panel 4 and is distributed with Magnetic Sensor 1, measure control panel 4 and be placed on fuel cell 7 exterior top surface, connect load 5 on the electrode 6 of fuel cell 7, the field coil of Magnetic Sensor 1 connects driving source 2, and the measurement coil of Magnetic Sensor 1 connects the analog digital modular converter of data acquisition process 3.

Described data acquisition process 3 is made of analog digital modular converter, microprocessor, digital-to-analogue conversion and driver;

Coil is measured in one group of coiling on the magnet ring of described Magnetic Sensor 1, and the distribution that is used for measuring fuel cell current under the current intelligence at this moment, if need to measure static distribution of current, then needs the fuel cell load current AC compounent of modulating or superpose;

Two groups of coils of coiling on the magnet ring of described Magnetic Sensor 1, one group is field coil, one group for measuring coil, it is saturated that drive coil adopts AC excitation to arrive, if superposeed in the magnet ring external magnetic field time, the waveform and the harmonic wave of magnetic field AC compounent of the state of saturation of excitation changed, measure the external magnetic field that this variation can record stack, that is to say to have recorded the constant or variation magnetic field that the battery distributed current produces by measuring coil.

The invention has the beneficial effects as follows to need not the original structure of Proton Exchange Membrane Fuel Cells is transformed, can measure the distribution of current of fuel battery inside easily.Can accomplish thus:

(1) in the fuel cell development process, can be used for detecting and study that local deficency, hydro-thermal skewness, loose contact, catalyst distribution are inhomogeneous, whether even run off problem such as;

(2) in the fuel cell manufacture manufacture process, can locally stop up the local deficency that causes in order to find whether to exist, whether have the hydro-thermal skewness, whether have loose contact, in order to avoid the monolithic battery that the part is bad is thought by mistake is the normal monolithic pile of packing into, causes whole fuel cell system performance to descend.

(3) in the fuel cell operation process, can be used for online monitoring and whether have local bad variation, prevent under the total current normal range situation, owing to the excessive fault that causes of local current densities, danger.

Simultaneously, this measurement mechanism have simple in structure, cost is low, the characteristics that are easy to make.The present invention is conceived to on-line monitoring, so that in time fault is prevented, has very high practical value.

Description of drawings

Fig. 1 is the proton exchange membrane fuel cell structure synoptic diagram.

Fig. 2 is for Proton Exchange Membrane Fuel Cells internal current distribution situation and flow to synoptic diagram.

Fig. 3 places Magnetic Sensor at outside batteries to measure inside battery distribution of current and magnetic field mathematical model synoptic diagram.

Fig. 4 is a magnetic direction synoptic diagram in magnet ring.

Fig. 5 is the magnetic direction synoptic diagram that battery current produces at the magnet ring center.

The magnetic direction synoptic diagram that Fig. 6 produces in magnet ring for battery current.

The magnetic direction synoptic diagram that Fig. 7 inducts on the magnet ring axis for battery current.

Fig. 8 is a fuel cell current apparatus for measuring distribution synoptic diagram.

Embodiment

The present invention proposes the magnetic effect of utilizing electric current and measure a kind of fuel cell internal current distribution measurement method and the device that the Proton Exchange Membrane Fuel Cells internal current distributes.In fuel cell current apparatus for measuring distribution synoptic diagram shown in Figure 8, on measurement control panel 4, be distributed with Magnetic Sensor 1, measure control panel 4 and be placed on fuel cell 7 exterior top surface, connect load 5 on the electrode 6 of fuel cell 7, the field coil of Magnetic Sensor 1 connects driving source 2, and the measurement coil of Magnetic Sensor 1 connects the data-converting block of data acquisition process 3.Described data acquisition process 3 is made of analog digital modular converter, microprocessor, digital-to-analogue conversion and driver;

It is as follows to utilize the fuel cell current apparatus for measuring distribution to measure the principle of distribution of current of fuel battery inside,

The present invention utilizes the magnetic effect of electric current to measure the distribution of current of fuel battery inside.We know that electric current produces magnetic field around it, so the distribution of current of fuel battery inside, can measure by according to certain rule the plurality of magnetic sensor being set at outside batteries.

The current distributions of fuel battery inside and flowing to as shown in Figure 2, if the current density in a certain zone is big, the magnetic field of regional area also should be bigger.Can consider to measure the size of local current by the measurement of local magnetic field power.Fuel cell is divided into some zonules, and the electric current that passes each zonule can be reduced to the electric current by the carrying flow direct conducting wire in this axle center, zonule; Electric current to outside extraction electrode in the pole plate is simplified horizontal carrying flow direct conducting wire.Distribution of current in the entire cell then can be reduced to some carrying flow direct conducting wires with right-angled bend, as long as the zone is enough little, and the distribution situation that then can accurately approach actual current.

At the location arrangements magnetic field sensor of zonule correspondence,, just can determine the size of current of this zonule indirectly according to the size of the output signal of magnetic field sensor.Utilize magnetic field sensor to measure the electric current in its respective cell territory in many places, just can learn the overall condition that fuel cell internal current distributes.

As shown in Figure 3, place Magnetic Sensor at outside batteries and measure in inside battery distribution of current and the magnetic field mathematical model synoptic diagram, according to electromagnetics knowledge as can be known, current element Idl at the magnetic induction density dB of P point place generation is arbitrarily:

$\mathrm{dB}=\frac{{\mathrm{\&mu;}}_0}{4\mathrm{\&pi;}}\frac{\mathrm{Idl}\sin \mathrm{\&theta;}}{r^{\&prime;2}}$

Then alive I, length is that the magnetic induction density B that the carrying flow direct conducting wire of L produces at P point place is:

$B={\mathrm{\&mu;}}_r{B}_0=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="4"\; label="r\; I"\; filenames="A200810116164E00142.png"\; state="\{\{state\}\}">r</figure-callout>}}I}{4\mathrm{\&pi;r}}(\cos {\mathrm{\&theta;}}_1-\cos {\mathrm{\&theta;}}_2)$

μ wherein ₀Be permeability of vacuum, μ _rRelative permeability for magnetic medium.

Magnetic Sensor 1 is the magnet ring that a kind of employing is wound with coil, and the current distributions of fuel battery inside as shown in Figure 2 can be reduced to a series of current carrying conductors with right-angled bend; So place Magnetic Sensor (shown in Fig. 3,5,6,7) at outside batteries.

It is the current carrying conductor coaxial with magnet ring that the electric current of interior zone that magnet ring covers can be simplified abstract, and the current carrying conductor of two vertical magnet ring axis (electric current corresponding to leading to exit is parallel to bipolar plate surfaces).The current carrying conductor coaxial with magnet ring can evoke the toroidal magnetic field in magnet ring, if this changes of magnetic field, the coil on the magnet ring will produce induced electromotive force.When cell area bigger, it is less relatively to measure coil dimension, the approximate lead of seeing two endless as in two magnetic field of in magnet ring, evoking perpendicular to the current carrying conductor of magnet ring axis (from the magnet ring axis up to the infinite distance) then, one is far away apart from magnet ring, and one is nearer apart from magnet ring.In view of the above, can be similar to and obtain magnet ring P point place induction level and be:

$B={\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="A200810116164E00122.png,A200810116164E00142.png"\; state="\{\{state\}\}">B</figure-callout>}}_1+B_2+{\mathrm{<figure-callout\; id="3"\; label="B"\; filenames="A200810116164E00142.png"\; state="\{\{state\}\}">B</figure-callout>}}_3=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="1"\; label="r\; I"\; filenames="A200810116164E00122.png,A200810116164E00142.png"\; state="\{\{state\}\}">r</figure-callout>}}{I}_{}{}_1}{4\mathrm{\&pi;}{r}_1}(\cos {\mathrm{\&theta;}}_1-\cos {\mathrm{\&theta;}}_2)+\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_r{I}_2}{4\mathrm{\&pi;}{r}_2}+\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="3"\; label="r\; I"\; filenames="A200810116164E00142.png"\; state="\{\{state\}\}">r</figure-callout>}}{I}_{}{}_3}{4\mathrm{\&pi;}{\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="A200810116164E00142.png"\; state="\{\{state\}\}">r</figure-callout>}}_3}$

$=\frac{{\mathrm{\&mu;}}_0{\mathrm{\&mu;}}_{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="A200810116164E00142.png"\; state="\{\{state\}\}">r</figure-callout>}}}{4\mathrm{\&pi;}}[\frac{I_1}{r_1}(\cos {\mathrm{\&theta;}}_1-\cos {\mathrm{\&theta;}}_2)+(\frac{I_2}{r_2}+\frac{I_3}{r_3})]$

Coaxial current carrying conductor and the influence of vertical current carrying conductor to magnetic-field measurement about simplification obtains have following discussion:

(1) as Fig. 4, the magnetic field B that evokes in magnet ring 602 perpendicular to the current carrying conductor 601 of magnet ring axis (parallel with magnet ring end face) is a reverse symmetry, the magnetic direction one-in-and-one-out, zone 603 vertical papers inwards, zone 604 vertical papers are outside, if the unidirectional even coiling of the coil on the magnet ring, then this current in wire changes the induced electromotive force that causes and can cancel out each other substantially in coil; Magnetic direction is vertical with the closed-loop path direction of magnet ring in addition, so the magnetic field of evoking in magnet ring is also very little, based on these two reasons, so can think that this parallel wire induced electromotive force in the unidirectional winding on magnet ring can ignore.

(2) as shown in Figure 5, if battery current exit 704 is configured in phase the same side (about membrane electrode 701 symmetries), current opposite in direction then, the magnetic field B that the magnet ring place of two transverse currents (be parallel to the magnet ring end face, perpendicular to the magnet ring axis) above battery the produces part of also can cancelling each other;

As shown in Figure 6, if battery current exit 804 is configured in an opposite side (about membrane electrode 801 antisymmetry), and is though electric current is in the same way, described by (1), the magnetic field that every section horizontal equivalent current carrying conductor evokes in magnet ring all is antisymmetric, so also can ignore its influence.Homonymy configuration fuel cell current terminal also has same effect, so wherein the transverse current the action of a magnetic field of inducting is more obvious.

(3) as shown in Figure 7, the distributed current of outside, 901 overlay areas of magnet ring, area occupied is bigger, can be reduced to infinity, so further think on the statistical significance distribution of current symmetry (particularly for the magnet ring that is positioned at the middle part) substantially, but the magnetic field symmetry of therefore inducting on the magnet ring axis direction opposite (903 magnetic fields that produce at the vertical paper in axis place inwards, 904 magnetic fields that produce are outside at the vertical paper in axis place) can be thought and offset basically; The electric current of corresponding battery surface according to top analysis, easily know symmetry substantially, and direction is opposite, so also can roughly offset.

In case of necessity, can be in the outside influence that increases magnetic shielding device with the extra-regional electric current of further shielding magnet ring of magnet ring.

In sum, can roughly obtain conclusion: the magnetic field of being inducted in the magnet ring, mainly relevant with the penetrating current of magnet ring institute overlay area, other regional current affects is less, can consider in the rough measure analysis to ignore.

Certainly, in actual measurement, magnetic field in the magnet ring and institute overlay area current related the time, still be subjected to the influence of other regional distribution of current.If will obtain result more accurately, we can calibrate the influence of magnet ring being measured with other areal distribution electric current of further elimination.

From above-mentioned principle introduction as can be seen, the core of this measuring method is the corresponding relation between electric current and magnetic field, and electric current is synchronous variation substantially to magnetic field, so response speed can be very fast.In addition, the direct linear relationship of electric current and magnetic induction density, image current is complicated like that to effect of nonlinear relation between the infrared radiation, so that measurement might be accomplished is more accurate.As seen, the advantage of this method is fairly obvious.

Embodiment

The test process of measuring the distribution of current of fuel battery inside is:

The encapsulation soft magnetic material of no use of affirmation fuel cell 7, easy magnetization material are as cover plate;

When measuring the distribution of current of fuel cell, the surface that control panel 4 is fixed on fuel cell 7 will be measured;

During measurement, driving source 2 output drive sinusoidal excitation electric currents are added on the field coil of magnet ring, in magnet ring, produce and make it saturated alternating magnetic field, the magnetic field superposition that the fuel battery inside distributed current produces is to magnet ring, influence the degree of saturation of magnet ring, the waveform and the harmonic wave of the induced electromotive force in the coil measured in influence.

The induced electromotive force of measuring in the coil is delivered in the data acquisition process 3, handles;

Demodulate the size of current of magnet ring corresponding region.

Coil is measured in one group of coiling on the magnet ring of described Magnetic Sensor 1, and the distribution that is used for measuring fuel cell current under the current intelligence at this moment, if need to measure static distribution of current, then needs the fuel cell load current AC compounent of modulating or superpose;

Two groups of coils of coiling on the magnet ring of described Magnetic Sensor 1, one group is field coil, one group for measuring coil, it is saturated that drive coil adopts AC excitation to arrive, if superposeed in the magnet ring external magnetic field time, the waveform and the harmonic wave of magnetic field AC compounent of the state of saturation of excitation changed, measure the external magnetic field that this variation can record stack by measuring coil, that is to say to have recorded the constant or variation magnetic field that the battery distributed current produces, utilize formula in the above-mentioned measuring principle to demodulate the size of current of magnet ring corresponding region then.

Claims (6)

1. a fuel cell internal current distribution measurement method is characterized in that, this measuring method is to utilize Magnetic Sensor to measure the distribution situation of magnetic field and electric current; Concrete steps are:

1) a plurality of Magnetic Sensors is arranged in certain plane parallel with fuel cell surface;

2) sensor and fuel cell enter duty, measure the Distribution of Magnetic Field of fuel cell surface;

3) resolve the distribution of current of fuel cell surface/inside according to the strength distribution in magnetic field.

2. according to the described fuel cell internal current distribution measurement method of claim 1, it is characterized in that, it is to open driving source that described sensor and fuel cell enter duty, driving source output drive sinusoidal excitation electric current is added on the magnet ring field coil of Magnetic Sensor, in magnet ring, produces and make it saturated alternating magnetic field; Fuel cell is following in working order, and the magnetic field superposition that the distributed current of fuel battery inside produces influences the degree of saturation of magnet ring to the magnet ring field coil, causes that waveform and the harmonic wave of measuring the induced electromotive force in the coil change.

3. according to the described fuel cell internal current distribution measurement method of claim 1, it is characterized in that, induced electromotive force in the described measurement coil is delivered to data acquisition processing system by the measurement coil of magnet ring and is handled, the vertical current element of part, fuel cell plane produces the principle in stronger relatively magnetic field in the part, demodulate the size of current of magnet ring corresponding region.

4. fuel cell current apparatus for measuring distribution, it is characterized in that, this measurement mechanism is included in to measure on the control panel (4) and is distributed with Magnetic Sensor (1), measure control panel (4) and be placed on fuel cell (7) exterior top surface, the electrode (6) of fuel cell (7) is gone up and is connected load (5), the field coil of Magnetic Sensor (1) connects driving source (2), and the measurement coil of Magnetic Sensor (1) connects the analog digital modular converter of data acquisition process (3).

5. according to the described fuel cell internal current apparatus for measuring distribution of claim 4, it is characterized in that, coiling is measured coil for one group on the magnet ring of described Magnetic Sensor, be used for measuring the distribution of fuel cell current under the current intelligence, at this moment, if need to measure static distribution of current, then need the fuel cell load current AC compounent of modulating or superpose.

6. according to the described fuel cell internal current apparatus for measuring distribution of claim 4, it is characterized in that, two groups of coils of coiling on the magnet ring of described Magnetic Sensor, one group is field coil, one group for measuring coil, it is saturated that drive coil adopts AC excitation to arrive, if superposeed in the magnet ring external magnetic field time, the waveform and the harmonic wave of magnetic field AC compounent of the state of saturation of excitation changed, measure the external magnetic field that this variation can record stack by coil, that is to say to record the constant or variation magnetic field that the battery distributed current produces.

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