JP3601493B2 - Fuel cell system and ejector circulation device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system and an ejector circulating device suitable for a fuel cell, and more particularly to a fuel cell system and an ejector circulating device having improved exhaust gas circulating performance over a wide operating range.
[0002]
[Prior art]
Fuel cells supply hydrogen as fuel gas to the fuel electrode and supply oxygen-containing air to the air electrode to electrochemically react hydrogen and oxygen to generate electricity directly. High power generation efficiency is obtained and the environment is excellent.
[0003]
In recent years, the use of solid polymer ion-exchange membranes as electrolytes has made it possible to increase the size and output, and solid polymer fuel cells that do not require an aqueous acid solution have attracted attention as fuel cell systems using hydrogen gas. Have been.
[0004]
In a fuel cell, a fuel gas containing hydrogen and an air containing oxygen are supplied to a fuel electrode and an air electrode opposed to each other with a solid polymer membrane interposed therebetween. With the aim of reducing the consumption of raw fuel gas in this fuel cell and improving the output characteristics by reducing the utilization rate of hydrogen gas, the exhaust gas from the fuel electrode of the fuel cell is recirculated and Many recirculation systems have been devised which are mixed with a newly supplied hydrogen-rich fuel gas and supplied to the fuel electrode of a fuel cell.
[0005]
It has been found that the power generation efficiency of the fuel cell is improved by maintaining the amount of exhaust gas to be recirculated and the amount of fuel gas newly supplied from the outside at a certain ratio or more. Ejectors are well known as a circulating device that mixes two flows.However, since the negative pressure and the drag due to the flow rate of the supplied fuel gas are used as the driving force for circulation, the amount of supplied fuel gas and the circulating gas flow rate can be widened. It is difficult to keep it above a certain level in the area.
[0006]
As an example of a variable capacity ejector for expanding an ejector operating area, Japanese Patent Application Laid-Open No. Hei 7-185284, in which a slide mechanism is used to make the entire flow path area of the ejector variable, or a needle-shaped adjusting rod inserted into a nozzle, Japanese Unexamined Patent Publication No. 8-338398 discloses that the nozzle area can be changed by changing the position of the ejector. However, since both have a structure in which the variable mechanism is controlled from the outside of the ejector, it is necessary to add a seal structure to the sliding portion. .
[0007]
[Problems to be solved by the invention]
However, since hydrogen, which is the working gas of a fuel cell, has a very small molecular size, when sealing the hydrogen gas at the sliding portion of the ejector equipped with the above-described conventional variable mechanism, high working accuracy is required for the sealing portion. In addition to the requirement, there is a problem that the friction of the seal portion is increased and controllability is impaired.
[0008]
In view of the above problems, an object of the present invention is to provide an ejector circulating device capable of mixing a raw fuel gas and an exhaust circulating gas at a constant mixing ratio in an operating region having a wide gas flow rate without providing a variable mechanism in the ejector. Another object of the present invention is to provide a fuel cell system having improved fuel gas circulation performance using the ejector circulation device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is to mix a fuel cell body having a fuel electrode and an air electrode with a discharge circulating gas discharged from the fuel electrode and a raw fuel gas having a high hydrogen concentration. A fuel cell system having an ejector circulating device for supplying fuel gas mixed with the ejector circulating device to the fuel electrode, the ejector circulating device includes a first supply port, a second supply port, The fluid supplied from at least two of the supply port and the third supply port is mixed and discharged from the discharge port, and the first nozzle connected to the first supply port opens toward the first mixing chamber. A second supply port is opened in the first mixing chamber, and a second nozzle having a larger cross-sectional area than the first nozzle is provided from the first mixing chamber toward the second mixing chamber in front of the ejection direction of the first nozzle; A third supply port in the second mixing chamber The second mixing chamber communicates with the discharge port through a throat section and a diffuser section to supply the raw fuel gas to the first supply port, and the raw fuel gas and the exhaust circulating gas are supplied to the second supply port. The main point is that any one of the above is switchably supplied, and control is performed such that when the raw fuel gas is supplied to the second supply port, the exhaust circulating gas is supplied to the third supply port.
[0010]
According to a second aspect of the present invention, in the fuel cell system according to the first aspect, when the output of the fuel cell system is lower than a predetermined value and the load is low, the raw fuel gas is supplied from the first supply port. Operating in the first state, in which the exhaust gas is supplied from the second supply port and the pipe for supplying the exhaust gas to the third supply port is cut off, and at a high load when the output of the fuel cell system is equal to or more than a predetermined value. The gist is to operate in a second state in which raw fuel gas is supplied from at least one of the first supply port and the second supply port and exhaust circulating gas is supplied from the third supply port.
[0011]
In order to achieve the above object, a third aspect of the invention is directed to the fuel cell system according to the second aspect, in which the fuel cell system is operated in the second state during a transition when the output of the fuel cell system increases.
[0012]
According to a fourth aspect of the present invention, there is provided a fuel cell system according to any one of the first to third aspects, wherein the first supply port has a first supply port for supplying raw fuel gas. And a second pressure regulating valve is provided in the pipe for supplying the raw fuel gas to the second supply port, and the pressure of the raw fuel gas supplied to the first supply port and the pressure supplied to the second supply port are increased. And that the pressure of the raw fuel gas to be controlled can be controlled independently.
[0013]
In order to achieve the above object, the invention according to claim 5 is an ejector circulation device that mixes fluids supplied from at least two of the first supply port, the second supply port, and the third supply port and discharges the mixed fluid from the discharge port. An apparatus, wherein a first nozzle connected to a first supply port opens toward a first mixing chamber, a second supply port opens in the first mixing chamber, and a second mixing chamber extends from the first mixing chamber. A second nozzle having a larger cross-sectional area than the first nozzle is opened toward the first nozzle, a third supply port is opened in the second mixing chamber, and the second mixing chamber is connected to the discharge port through a throat section and a diffuser section in this order. It is assumed that the connection has been made.
[0014]
【The invention's effect】
According to the first aspect of the present invention, a fuel cell body having a fuel electrode and an air electrode, and the exhaust gas circulated from the fuel electrode and a raw fuel gas having a high hydrogen concentration are mixed to form a fuel gas. In a fuel cell system having an ejector circulation device and a flow path for supplying a fuel gas mixed by the ejector circulation device to the fuel electrode, the ejector circulation device includes a first supply port, a second supply port, and a second supply port. (3) mixing fluid supplied from at least two of the supply ports and discharging the mixed fluid from the discharge port, wherein a first nozzle connected to the first supply port opens toward the first mixing chamber, and And a second nozzle having a larger cross-sectional area than the first nozzle is provided substantially coaxially with the first nozzle from the first mixing chamber toward the second mixing chamber. The third supply port is opened and the second supply port is opened. The joint room is connected to the outlet through a throat section and a diffuser section in order, supplies raw fuel gas to the first supply port, and switches either the raw fuel gas or the exhaust circulating gas to the second supply port. And when the raw fuel gas is supplied to the second supply port, the discharge circulating gas is controlled to be supplied to the third supply port. Therefore, depending on the operation state of the fuel cell, the first nozzle or the second nozzle of the ejector circulation device is controlled. One of the nozzles can be selectively used as a driving flow source, and there is an effect that the operating area of the ejector circulation device can be expanded while suppressing leakage of hydrogen gas.
[0015]
According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, when the output of the fuel cell system is at a low load lower than a predetermined value, the raw fuel gas is supplied from the first supply port, The fuel cell system is operated in the first state in which the exhaust gas is supplied from the supply port and the pipe for supplying the exhaust gas to the third supply port is shut off. Since the fuel cell system is operated in the second state in which the raw fuel gas is supplied from at least one of the supply port and the second supply port and the exhaust circulating gas is supplied from the third supply port, the nozzle is operated in accordance with the load of the fuel cell system. Since the diameter and the throat diameter can be appropriately selected, there is an effect that a high exhaust gas circulating gas amount can be maintained over the entire system operating region.
[0016]
According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, the fuel cell system is operated in the second state during a transient when the output of the fuel cell system increases, so that the amount of hydrogen supplied to the stack is increased. And the pressure of the stack fuel electrode can be quickly increased until the amount of generated power increases.
[0017]
According to the fourth aspect of the invention, in addition to the effects of the first to third aspects, the first pressure regulating valve is provided on the pipe for supplying the raw fuel gas to the first supply port. (2) A second pressure regulating valve is provided in a pipe for supplying the raw fuel gas to the supply port, and the pressure of the raw fuel gas supplied to the first supply port and the pressure of the raw fuel gas supplied to the second supply port are independent. Has the effect that the circulating amount of the exhaust circulating gas can be maintained in a wide operating region while maintaining the controllability of the supply amount of the raw fuel gas satisfactorily.
[0018]
According to the fifth aspect of the present invention, there is provided an ejector circulation device that mixes fluids supplied from at least two of the first supply port, the second supply port, and the third supply port and discharges the mixed fluid from the discharge port, A first nozzle connected to the first supply port opens toward the first mixing chamber, a second supply port opens in the first mixing chamber, and a second nozzle opens from the first mixing chamber in the ejection direction of the first nozzle. A second nozzle having a larger cross-sectional area than the first nozzle is provided toward the mixing chamber. A third supply port is opened in the second mixing chamber, and the second mixing chamber is discharged through a throat section and a diffuser section. When the first fluid is supplied from the first supply port and the second fluid is supplied from the second supply port, the first nozzle is activated, and the first fluid is supplied from the second supply port to the first supply port. When the second fluid is supplied from the third supply port and the first fluid is supplied, the first fluid is supplied. Since the second nozzle cross sectional area than the nozzle is greater acts as an ejector circulation unit having two different characteristics of activated, there is an effect that it is possible to enlarge the operation flow area of the ejector circulation unit.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a system configuration diagram showing a main configuration of a fuel cell system according to the present invention, and is particularly suitable as a power source for an electric vehicle having a large load variation from idling to high-speed running.
[0020]
In FIG. 1, a fuel cell body (hereinafter, referred to as a stack) 1 includes a fuel electrode 2 and an air electrode 3. Actually, a cooling system pipe, a power supply line, various sensors, and the like are incorporated in the stack 1, but only the gas system is shown in this drawing.
[0021]
The fuel electrode 2 and the air electrode 3 are joined inside the stack 1 with an electrolyte membrane made of a solid polymer separated therebetween. At the fuel electrode 2, hydrogen is ionized and separated into hydrogen ions and electrons. Hydrogen ions move from the fuel electrode 2 side to the air electrode 3 side in the electrolyte membrane using moisture as a medium, electrons return from the fuel electrode 2 to the air electrode 3 through an external load circuit, and hydrogen ions, electrons and oxygen are removed. DC power generation is performed by an electrochemical reaction that becomes water by being combined at the air electrode 3.
[0022]
In the present embodiment, a method in which hydrogen is directly held as fuel is shown. Hydrogen gas is compressed and held in the hydrogen storage tank 4 in a high pressure state. The higher the filling pressure of the hydrogen storage tank 4, the longer the travelable distance per filling and the smaller the tank volume, so that the hydrogen storage tank 4 usually reaches several tens MPa or more. Since it is difficult to control the supply pressure to the stack 1 from the high pressure of the hydrogen storage tank 4 at a time, the downstream pressure can be substantially controlled downstream of the hydrogen storage tank 4 via the pressure reducing valve 5. After the pressure is reduced to a constant value, hydrogen gas as raw fuel gas is supplied to the pressure regulating valve 6 disposed further downstream. A pressure sensor 19 for measuring the hydrogen gas pressure after the pressure adjustment is provided downstream of the pressure adjustment valve 6, and a branch portion 8 branched in two directions is provided downstream of the pressure sensor 19. A first supply port 9 provided in an ejector circulation device (hereinafter, abbreviated as “ejector”) 7 is connected to one downstream side of the branch portion 8, and hydrogen gas whose pressure is adjusted by the pressure adjustment valve 6 is supplied. .
[0023]
The ejector 7 is provided with a second nozzle in addition to a first nozzle connected to the first supply port 9 as described later, and a second supply nozzle is provided downstream of the first nozzle and upstream of the second nozzle. The downstream side of the second nozzle is connected to the third supply port 11, and the gases supplied from the supply ports 9, 10, 11 are mixed and discharged from the discharge port 12. ing.
[0024]
The second supply port 10 of the ejector 7 is connected to a hydrogen gas supply pipe connected from the other downstream side of the branch portion 8 via a shutoff valve 18, and a three-way valve 16 for discharging exhaust gas from the fuel electrode 2 of the stack 1. And a discharge circulation gas pipe which is supplied via a gas outlet. With this configuration, by switching between the shutoff valve 18 and the three-way valve 16, the gas supplied to the second supply port 10 can be switched from a hydrogen storage tank to a reduced pressure hydrogen gas or a discharge circulation gas.
[0025]
Further, the ejector 7 has a third supply port 11 to which the other side of the three-way valve 16 is connected, so that the exhaust circulating gas can be supplied.
[0026]
The discharge port 12 of the ejector 7 is connected to a humidifier 13, and the fuel gas mixed by the ejector 7 is humidified almost to a water vapor saturated state. The humidified fuel gas is supplied to the fuel electrode 2 of the stack 1 and part of hydrogen is consumed by power generation. An exhaust circulating gas containing hydrogen that has not been used for power generation is discharged from the outlet of the fuel electrode 2, and the fuel electrode outlet is connected to a branch portion 14 that branches in two directions. A three-way valve 16 is connected to one of the branch portions 14, and the other of the branch portion 14 is opened to the outside via a purge valve 15. If the power output demand of the stack suddenly decreases, the hydrogen in the circulation line cannot be consumed by the stack. At that time, the purge valve 15 is opened to discharge the excess hydrogen gas to the outside.
[0027]
From the above configuration, in the ejector 7, the hydrogen gas coming from the hydrogen storage tank 4 and the exhaust circulating gas having a low pressure after passing through the fuel electrode 2 of the stack 1 are mixed and flow downstream. When the mixed gas passes through the humidifier 13, it is humidified with water vapor necessary for the reaction in the electrolytic membrane in the stack, heated to a temperature suitable for the reaction, and then flows into the fuel electrode 2 of the stack 1.
[0028]
Then, hydrogen is consumed in the fuel electrode 2 of the stack 1, and surplus residual hydrogen gas is discharged from the stack 1 and sent to the ejector 7 again.
[0029]
On the other hand, although not shown in the drawing, a compressor that takes in the air, compresses the air, and sends it to the air line is installed upstream of the stack. The air compressed by the compressor also passes through the humidifier similarly to hydrogen, is humidified to a substantially saturated state, and then flows into the stack 1. The excess air gas that has consumed the oxygen content in the air at the air electrode 3 of the stack 1 is released to the atmosphere through the pressure control valve of the air line together with the water produced by the reaction in the stack. The air pressure is controlled by a pressure control valve so as to be a predetermined pressure as required.
[0030]
Although not shown in FIG. 1, water generated at the air electrode is recovered by a water recovery device provided in the air line, and the recovered water is supplied to the humidifier 13 by a pressure pump. , Is reused as cooling water for the stack 1.
[0031]
Further, the pressure regulating valve 6 has a role of controlling the flow rate of hydrogen supplied to the stack, and the output value of the pressure sensor 20 arranged upstream of the stack 1 so that the hydrogen pressure of the fuel electrode becomes a value suitable for the amount of power generation. While adjusting the amount of hydrogen present in the hydrogen gas circulation system so as to be a predetermined value predetermined according to the required load, and branching the pressure regulating valve 6 so as to replenish the amount of hydrogen consumed by power generation. While measuring the output value of the pressure sensor 19 provided in the section 8, the opening degree of the pressure regulating valve 6 is controlled so as to be a predetermined value determined in advance according to the amount of power generation.
[0032]
FIG. 2 shows a cross-sectional structure of the ejector 7 in the present embodiment. The ejector 7 is an ejector circulating device that mixes fluids supplied from at least two of the first supply port 9, the second supply port 10, and the third supply port 11 and discharges the fluid through the discharge port 12. The first nozzle 21 connected to the supply port 9 opens toward the first mixing chamber 31, the second supply port 10 opens in the first mixing chamber 31, and is separated from the first mixing chamber 31 by the partition wall 24. A second nozzle 25 having a larger cross-sectional area than the first nozzle 21 is opened toward the second mixing chamber 32, a third supply port 11 is opened in the second mixing chamber 32, and the second mixing chamber 32 is It is connected to the outlet 12 via the diffuser 30 in order.
[0033]
The components constituting the ejector 7 are assembled by assembling the first intake section 22 with the first nozzle 21 and the first connection port 9 for supplying the raw fuel gas and the first intake section 22 together with the O-ring 23. A second intake section 26 configured so that an upstream of a cylindrical second nozzle 25 provided integrally with the partition wall 24 communicates with the second supply port 10 for supplying raw fuel gas or exhaust circulation gas; By assembling the two intake portions 26 together with the O-ring 27, it is composed of a body portion 28 that forms a space communicating the third supply port 11 and the discharge port 12 through which the exhaust circulating gas circulates.
[0034]
The body portion 28 is provided with a throat 29 for mixing the raw fuel gas and the exhaust circulation gas, and a diffuser 30 for reducing the flow velocity of the mixed flow to recover the pressure.
[0035]
In the first state in which the shut-off valve 18 is closed and the three-way valve 16 is controlled to communicate with the second supply port 10, the second nozzle 25 is the raw fuel gas injected from the first nozzle 21. The flow is increased by the flow being throttled in front of the second nozzle 25, and the cylindrical shape of the second nozzle 25 becomes a throat portion with respect to the first nozzle 21. And the exhaust circulating gas is sucked by the flow from the first nozzle 21, and a mixed flow is generated inside the second nozzle 25. This mixed flow passes through the throat 29 as it is, and is discharged from the discharge port 12 while recovering the pressure by the diffuser 30.
[0036]
On the other hand, in the second state in which the shut-off valve 18 is opened and the three-way valve 16 is controlled to communicate with the third supply port 11 side, hydrogen gas is ejected from the second nozzle 25 and substantially It functions as a nozzle part, sucks the exhaust circulation gas from the third supply port 11, generates a mixed flow by the throat 29, and discharges the mixed flow from the discharge port 12 as in the first state.
[0037]
3A and 3B illustrate differences in ejector characteristics between a small ejector and a large ejector having different diameters of a throat portion and a nozzle portion. FIG. 3A shows a relationship between a supply gas flow rate Qin and a supply gas pressure Pin. In FIG. 3B, the circulation ratio R (the ratio of the circulation gas flow rate Qsu to the supply gas flow rate Qin) with respect to the supply gas flow rate Qin is indicated by a thin line for the characteristics of the small ejector, and the thick line is indicated for the characteristics of the large ejector.
[0038]
FIG. 3B is a diagram showing the relationship between the circulation ratio R and the supply gas flow rate Qin in the ejector. In the case of a small ejector having a small-diameter nozzle and a small-diameter throat, the case of a small-diameter nozzle and a large-diameter nozzle and a large-diameter throat are illustrated. The case of a large ejector is shown by a thick line. The supply gas flow rate Qin at which circulation starts decreases as the diameter decreases, but the maximum value of the circulation rate R when the supply gas flow rate Qin increases tends to increase as the diameter increases.
[0039]
Further, as shown in FIG. 3A, the supply pressure of the hydrogen gas supply system is regulated by the system, and the maximum pressure that can be supplied to the supply side connection port is restricted by Pinmax while securing the gas flow rate. become. Therefore, from the viewpoint of reducing the supply flow rate at the start of circulation to a lower flow rate side, a smaller diameter shows better characteristics, but a sufficient supplyable gas amount cannot be secured.
[0040]
Therefore, the flow rate range from the supply hydrogen gas flow rate Qmin at the time of minimum load of the system required during an idle state such as when the vehicle is stopped to the supply hydrogen gas flow rate Qmax at the time of maximum load of the system required during high-speed running or acceleration is within a range. In a very wide case, it is difficult for one nozzle to maintain the circulation ratio Rmin required to maintain a good power generation state of the stack.
[0041]
FIG. 4 shows the characteristics of the ejector used in the present embodiment, similarly to FIG. First, from the gas flow rate Qmin corresponding to the minimum operation load of the system to the gas flow rate Q1 that can be supplied to the circulation system from the first nozzle 21 at the maximum pressure Pinmax that can be applied upstream of the ejector, as a first state, a broken line in FIG. The circulation ratio R indicated by is secured.
[0042]
When the required power generation amount increases and the required supply amount of the raw fuel gas exceeds Q1, as a second state, the raw fuel gas is supplied to the second supply port 10 and the gas pressure in the second supply port 10 is controlled. By doing so, the raw fuel gas that is insufficient in the first nozzle 21 is supplied from the second nozzle 25 that functions as a large-diameter nozzle. At this time, the second nozzle 25 has a diameter capable of supplying the raw fuel gas amount Qmax required at the time of the maximum power generation request when the pressures of the first supply port 9 and the second supply port 10 are both Pinmax.
[0043]
Since the circulation ratio R in the case of the second state has the value indicated by the one-dot chain line, it is necessary in all the stack operation areas by switching the first and second states according to the load required of the system. The circulation ratio Rmin can be secured.
[0044]
Next, a control flow of the flow path switching valve and the pressure adjusting valve in the present embodiment will be described with reference to FIGS. FIG. 5 shows how to control the valve downstream pressure tPrsHe of the pressure regulating valve 6 and the state of the flow path switching in order to realize the target value tPWR of the generated power of the fuel cell given from various vehicle conditions. FIG. 6 is a graph showing an example of various tables referred to in the control flow.
[0045]
First, in step S10, the generated power target value tPWR separately calculated based on the required load is read, and the measured value tPrsHO of the pressure sensor 19 and the measured value tPrsHeO of the pressure sensor 20 are read. Next, in step S12, a target fuel gas pressure value tPrsH at the fuel electrode of the fuel cell is calculated based on the target power generation value tPWR of the fuel cell. In this calculation, the fuel gas pressure target value tPrsH for the generated power target value tPWR as shown in FIG. 6A is given in a table, and as the power generation target value of the fuel cell, that is, the load increases, the fuel gas at the fuel electrode increases. The pressure is set to increase.
[0046]
Next, at step S14, the difference between the target fuel gas pressure value tPrsH at the fuel electrode 2 obtained at step S12 and the current fuel gas pressure tPrsHO at the fuel electrode 2 obtained from the pressure sensor 20, and the differential pressure tPrsHd = tPrsH-tPrsHO. Is calculated as a condition value for determining a basic pattern of control of the pressure regulating valve 6.
[0047]
Step S16 is a step of determining whether or not the load request for the fuel cell has increased rapidly. If the differential pressure tPrsHd is equal to or greater than a predetermined value tPrsHdH, the state is set to a rapid acceleration state, and the process proceeds to step S18. The target opening degree tArV is set to a settable maximum value tArVmax, then, in step S20, a signal tSV for performing the opening / closing control of the shutoff valve 18 is set to a state value serving as an opening command, and the switching command value t3WV of the three-way valve 16 is set to an ejector. The information is transmitted to the flow path switching sequence so as to be in the second state, as a state value serving as a command to communicate with the third supply port 11 side 7.
[0048]
If it is determined in step S16 that tPrsHd <tPrsHdH, the process proceeds to step S22, and it is determined whether the load request decreases and it is necessary to control the purge valve 15 to open. If tPrsHd is equal to or less than the predetermined negative value tPrsHdL, the process proceeds to step S24, where the target opening degree tArV of the pressure regulating valve 6 is set to a settable minimum value tArVmin, and the purge valve 15 is controlled to open in the control sequence. Then, in step S26, the signal tSV for performing the opening / closing control of the shutoff valve 18 is set to a state value serving as a closing command, and the switching command value t3WV of the three-way valve 16 is sent to the second supply port 10 side of the ejector 7. Information is transmitted to the flow path switching sequence so as to be in the first state as a state value serving as a communication command.
[0049]
If it is determined in step S22 that tPrsHd> tPrsHdL, it is determined that the control state is the normal control state, and the process proceeds to step S28 to determine whether or not the flow path switching state is the first state. When tPrsH is smaller than a predetermined switching pressure tPrsH1 and the value tPrsHeO of the raw fuel gas pressure at the first supply port 9 measured by the pressure sensor 19 is smaller than tPrsHemax, which is the maximum supplyable pressure, the gas flow path is switched It is determined that the state is 1, and the process proceeds to step S30.
[0050]
In step S30, the target pressure value tPrsHe at the first supply port 9 is calculated such that the target pressure value tPrsH at the fuel electrode necessary for realizing the target generated power value tPWR is obtained. The pressure target value tPrsHe is calculated in advance according to the flow rate of the pressure loss in the fuel gas flow path from the pressure regulating valve 6 to the fuel electrode 2 cell of the stack 1 according to the flow rate. It is necessary to calculate as a value added to the gas pressure, and a format in which the value is calculated in advance and referred to as a table value as shown in FIG. 6B is better.
[0051]
Next, in step S32, a basic throttle area tArVm of the pressure regulating valve 6 is calculated according to tPrsHe so that a fuel gas flow rate corresponding to the fuel load is obtained. This calculation is given by a table as shown in FIG. 6C, and the throttle area tArVm increases as the target pressure value tPrsHe increases.
[0052]
Next, in step S34, the signal tSV for performing the opening / closing control of the shut-off valve 18 is set to a state value serving as a closing command, and the switching command value t3WV of the three-way valve 16 is provided as a command for communicating with the second supply port 10 side of the ejector 7. Information is transmitted to the flow path switching sequence so as to be in the first state as the state value, and the process proceeds to step S42 described later.
[0053]
On the other hand, if it is determined in step S28 that tPrsH is equal to or greater than tPrsH1 or that tPrsHO is equal to tPrsHemax, it is determined that the flow path switching state is the second state, and the process proceeds to step S36.
[0054]
In step S36, as in step S30, the calculation of tPrsH is performed using the map, and the calculation of tPrsHe is performed. As shown in FIG. 6C, the map used in FIG. It is compatible. Next, in step S38, similarly to step S32, the basic throttle area tArVm of the pressure regulating valve 6 is calculated according to tPrsHe so that a fuel gas flow rate corresponding to the fuel load is obtained. The table referred to here is a table as shown in FIG. 6E corresponding to the increase in the nozzle diameter.
[0055]
In step S40, similarly to step S20, the signal tSV for performing the opening / closing control of the shutoff valve 18 is set to a state value serving as an opening command, and the switching command value t3WV of the three-way valve 16 is sent to the third supply port 11 side of the ejector 7. Information is transmitted to the flow path switching sequence so as to be in the second state as a state value serving as a communication command, and the process proceeds to step S42.
[0056]
In step S42, for the tArVm calculated in step S32 or step S36, the actual pressure tPrsHeO of the first supply port 9 measured by the pressure sensor 19, the measured value of the pressure sensor 20, and the target value tPrsH determined in step S12. Then, a final correction area tArV is calculated such that the pressure at the first supply port 9 becomes a target value by adding a correction term α determined from the deviation from the above.
[0057]
As described above, the throttle area of the pressure adjusting valve 6 is determined by any one of Steps S18, S24, and S42, and the control information of the pressure adjusting valve 6 is transmitted to the pressure adjusting mechanism control device in Step S44, and the control flow ends. I do.
[0058]
In this embodiment, the valve 18 is a shut-off valve. However, if this valve is a pressure regulating valve, it acts as the second pressure regulating valve of claim 4, and the raw fuel gas pressure of the first nozzle section and the second nozzle section. Can be individually controlled, and the exhaust circulating gas amount can be maintained in a wide operating range while maintaining the controllability of the supply amount of the raw fuel gas.
[0059]
Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the shutoff valve 18 and the three-way valve 16 are used to switch the supply of the raw fuel gas and the exhaust circulating gas to the second supply port 10, whereas in the second embodiment, one switching valve 39 is used. By using this, the flow path switching similar to that of the first embodiment can be performed, and the flow path switching control can be easily performed.
[0060]
The switching valve 39 includes a body portion 40 having four connection ports, and a ball portion 41 having two flow paths 42 and 43 formed therein and rotatably contained inside the body portion 40.
[0061]
The four connection ports of the body section 40 include a connection port 44a for supplying raw fuel gas connected to the branch section 8 and a connection port for supplying exhaust circulation gas connected to the branch section 14 downstream of the fuel electrode 2. 44b, a gas discharge connection port 45a connected to the second supply port 10 of the ejector 7, and a gas discharge connection port 45b connected to the third supply port 11 of the ejector 7 are provided.
[0062]
In the first state, as shown in FIG. 7A, the flow path 42 of the ball portion 41 allows the connection port 44b and the connection port 45a to communicate with each other. Supply. At this time, the flow path 43 is arranged at a position where the remaining connection ports 44a and 45b of the body 40 are closed.
[0063]
On the other hand, in the second state, as shown in FIG. 7B, control is performed so that the ball portion 41 is rotated to the left by 90 °. At this time, the flow path 42 connects the connection port 44a and the connection port 45a, and supplies hydrogen gas to the second supply port 10 of the ejector 7, and the flow path 43 connects the connection port 44b and the connection port 45b. The exhaust circulating gas can be supplied to the third supply port 11 of the ejector 7.
[0064]
With the above configuration, the flow path switching similar to that of the first embodiment can be performed by one operation only by controlling the rotational position of the ball portion 41 with respect to the body portion 40.
[0065]
As described above, according to the present invention, a required amount of exhaust gas circulation can be secured for a supply gas flow rate corresponding to a wide load range, and stable fuel cell operation is possible.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram illustrating a configuration of a first embodiment of a fuel cell system according to the present invention.
FIG. 2 is a sectional view showing an internal structure of an ejector according to the embodiment.
FIG. 3 (a) is a diagram illustrating a supply gas pressure characteristic with respect to a supply gas flow rate of a small ejector and a large ejector. (B) is a diagram for explaining the circulation ratio characteristics of the small ejector and the large ejector with respect to the supply gas flow rate.
FIG. 4A is a diagram illustrating a supply gas pressure characteristic with respect to a supply gas flow rate in the ejector of the embodiment. (B) It is a figure explaining the circulation ratio characteristic with respect to the supply gas flow rate in the ejector of embodiment.
FIG. 5 is a flowchart illustrating a first state and a second state switching control of the pressure regulating valve and the gas flow path according to the first embodiment.
FIG. 6 is a graph showing an example of various tables referred to in the control flow.
FIG. 7A is a configuration diagram illustrating a main part of a first state in a second embodiment. (B) It is a lineblock diagram explaining the important section of the 2nd state in a 2nd embodiment.
[Explanation of symbols]
1. Fuel cell body (stack)
2. Fuel electrode
3 ... Air electrode
4: Hydrogen storage tank
5 ... Reducing valve
6 ... Pressure regulating valve
7. Ejector circulation device
9 ... First supply port
10: Second supply port
11 ... third supply port
12 ... outlet
13. Humidifier
14 ... Branch
15 ... Purge valve
16 ... 3-way valve
17 ... Branch
18 ... shut-off valve
19 ... Pressure sensor
20 ... Pressure sensor

Claims (5)

A fuel cell body having a fuel electrode and an air electrode, an ejector circulating device that mixes an exhaust circulating gas discharged from the fuel electrode and a raw fuel gas having a high hydrogen concentration to produce a fuel gas, and an ejector circulating device. A fuel cell system having a flow path for supplying the mixed fuel gas to the fuel electrode,
The ejector circulation device mixes fluids supplied from at least two of the first supply port, the second supply port, and the third supply port, and discharges the mixed fluid from the discharge port;
A first nozzle connected to the first supply port opens toward the first mixing chamber,
A second supply port is opened in the first mixing chamber, and a second nozzle having a larger cross-sectional area than the first nozzle is provided from the first mixing chamber toward the second mixing chamber ahead of the ejection direction of the first nozzle,
A third supply port is opened in the second mixing chamber, and the second mixing chamber communicates with the discharge port through a throat portion and a diffuser portion sequentially,
The raw fuel gas is supplied to the first supply port, and either the raw fuel gas or the exhaust circulating gas is switchably supplied to the second supply port. When the raw fuel gas is supplied to the second supply port, the raw fuel gas is supplied to the third supply port. A fuel cell system characterized by controlling to supply exhaust circulation gas. When the output of the fuel cell system is low and the load is lower than a predetermined value, the pipe supplies the raw fuel gas from the first supply port, supplies the exhaust circulating gas from the second supply port, and supplies the exhaust circulating gas to the third supply port. Driving in the first state of shutting off
At the time of high load at which the output of the fuel cell system is equal to or more than a predetermined value, a second state in which raw fuel gas is supplied from at least one of the first supply port and the second supply port and exhaust circulating gas is supplied from the third supply port. The fuel cell system according to claim 1, wherein the fuel cell system is operated on a fuel cell. 3. The fuel cell system according to claim 2, wherein the fuel cell system operates in the second state during a transition when the output of the fuel cell system increases. A first pressure regulating valve is provided in a pipe for supplying raw fuel gas to a first supply port, and a second pressure regulating valve is provided in a pipe for supplying raw fuel gas to a second supply port. The fuel according to any one of claims 1 to 3, wherein the pressure of the raw fuel gas supplied and the pressure of the raw fuel gas supplied to the second supply port can be controlled independently. Battery system. An ejector circulation device that mixes fluids supplied from at least two of a first supply port, a second supply port, and a third supply port and discharges the fluid through a discharge port,
A first nozzle connected to the first supply port opens toward the first mixing chamber,
A second supply port is opened in the first mixing chamber, and a second nozzle having a larger cross-sectional area than the first nozzle is opened from the first mixing chamber toward the second mixing chamber,
An ejector circulation device, wherein a third supply port is opened in the second mixing chamber, and the second mixing chamber is connected to the discharge port via a throat section and a diffuser section in this order.

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