JP2003100334A - Fuel cell system and ejector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system in which an ejector has no variable mechanism, the ratio (circulation ratio) of an exhaust gas flow against an starting gas flow is kept not less than a fixed value in a wide gas flow range to obtain a high hydrogen utilization efficiency. SOLUTION: The ejector 7 has a throat for mixing the starting gas and the exhaust gas, and nozzles of small size and large size that have opening at the entrance of each throat part. A first supply inlet 9a and a second supply inlet 9b are connected to the small size nozzle and the large size nozzle respectively. Pressure control valves 6a and 6b that control the supply pressure of each starting gas are provided at the first supply inlet 9a and the second supply inlet 9b respectively. The control is carried out that the starting gas is supplied from the small size nozzle at low load operation when the output of the fuel cell system is not larger than a predetermined value, and the starting fuel gas is supplied from the large size nozzle and the small size nozzle when the output of the fuel cell system is not less than a predetermined value or during transition time when the output is increasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system and an ejector, and more particularly to a fuel cell system with improved recirculation characteristics of exhaust gas discharged from a fuel electrode and an ejector suitable for the fuel cell system.

[0002]

2. Description of the Related Art A fuel cell is one in which hydrogen is supplied as a fuel gas to a fuel electrode and air containing oxygen is supplied to an air electrode to electrochemically react hydrogen with oxygen to directly generate electricity. Yes, high power generation efficiency can be obtained even on a small scale, and it is also environmentally friendly.

Further, in recent years, by using a solid polymer ion exchange membrane as an electrolyte, a solid polymer type fuel cell capable of miniaturization and high output without using an acid aqueous solution is a fuel cell system using hydrogen gas. Is being watched as.

In this fuel cell, the exhaust gas from the fuel electrode of the fuel cell is recirculated with the aim of reducing the consumption of raw fuel gas and increasing the utilization rate of hydrogen gas to improve the output characteristics. Thus, many recirculation systems have been devised, which are mixed with raw fuel gas rich in hydrogen newly supplied from the outside and supplied to the fuel electrode of the fuel cell.

The power generation efficiency of a fuel cell depends on the amount of exhaust gas to be recirculated and the amount of raw fuel gas newly supplied from the outside.
It has been found that keeping it above a certain ratio improves it. The ejector is well known as a circulation device that mixes the flow of two gases, but since the negative pressure and drag due to the flow rate of the raw fuel gas are used as the driving force of circulation, the flow rate of the raw fuel gas and the circulated discharge It is difficult to keep the ratio with the gas flow rate above a certain level in a wide operating range.

As an example of a variable displacement ejector for expanding the ejector operating region, Japanese Patent Laid-Open Publication No. 7-185284 in which a flow passage area of the entire ejector is variable by using a slide mechanism or a needle-shaped adjusting rod is inserted into a nozzle. Japanese Patent Laid-Open No. 8-338398 discloses that the nozzle area can be changed by changing the position of the adjusting rod. However, both of them have a structure in which the variable mechanism is controlled from outside the ejector, and therefore a seal structure is added to the sliding portion. There is a need to.

[0007]

However, since hydrogen, which is a working gas of a fuel cell, has a very small molecule size, in the ejector variable mechanism of the above-mentioned prior art, when trying to seal the hydrogen gas at the sliding portion, There is a problem that not only high processing accuracy is required for the seal portion, but also friction of the seal portion increases and controllability is impaired.

In view of the above problems, an object of the present invention is to provide a ratio of the exhaust gas flow rate to be circulated to the newly supplied raw fuel gas flow rate in a wide gas flow rate range without providing a variable mechanism in the ejector circulation device. It is an object of the present invention to provide a fuel cell system capable of maintaining a high (circulation ratio) above a certain level and achieving high hydrogen gas utilization efficiency.

Another object of the present invention is to provide an ejector capable of keeping the circulation ratio above a certain level in a wide range of gas flow rate.

[0010]

The invention according to claim 1 is
In order to achieve the above object, a fuel cell body having a fuel electrode and an air electrode, an ejector for recirculating exhaust gas discharged from the fuel electrode, and newly mixing with a raw fuel gas having a high hydrogen concentration, In a fuel cell system having a flow path for supplying the fuel gas mixed by the ejector to the fuel electrode, the ejector includes one throat portion in which raw fuel gas and exhaust gas are mixed, and an inlet at the throat portion inlet. The gist of the present invention is to have two nozzles that are opened, and a pressure adjusting valve that adjusts the supply pressure of the raw fuel gas for each nozzle upstream of the two nozzles.

In order to achieve the above object, the invention according to claim 2 is the fuel cell system according to claim 1, wherein the two nozzles have different diameters, and the tip of the nozzle having a small diameter is the tip of the nozzle having a large diameter. The gist is that it is arranged closer to the entrance of the throat part than.

In order to achieve the above object, the invention according to claim 3 is the fuel cell system according to claim 1 or claim 2, wherein the two nozzles include a nozzle having a large diameter and a nozzle having a small diameter. As described above, the gist is that they are arranged coaxially.

In order to achieve the above object, the invention according to claim 4 is the fuel cell system according to any one of claims 1 to 3, wherein two pressure regulating valves are provided upstream of the nozzle. The gist is that the ratio of the raw fuel gas controllable flow rate is made substantially equal to the ratio of the opening area of the nozzle portion.

In order to achieve the above object, a fifth aspect of the invention is the fuel cell system according to any one of the second to fourth aspects, in which the output of the fuel cell system is lower than a predetermined value. Sometimes, the raw fuel gas is supplied from the small diameter nozzle of the two nozzles, and when the output of the fuel cell system is a predetermined value or more, the raw fuel gas is supplied from the large diameter nozzle in addition to the small diameter nozzle. The point is to do.

In order to achieve the above object, the invention according to claim 6 is the fuel cell system according to any one of claims 1 to 5, wherein when the output of the fuel cell system is increased, the 2 The point is to control so that raw fuel gas is supplied from both nozzles.

According to a seventh aspect of the invention, in order to achieve the above object, in the ejector for mixing the first fluid and the second fluid, one throat portion where the first fluid and the second fluid are mixed. And has two nozzles having different diameters and having one end opened at the inlet of the throat, and the tip of the nozzle having a smaller diameter is closer to the inlet of the throat than the tip of a nozzle having a larger diameter. The point is that they are arranged.

[0017]

According to the invention described in claim 1, the fuel cell main body having the fuel electrode and the air electrode, and the exhaust gas discharged from the fuel electrode are recirculated to newly generate a hydrogen-rich source gas. In a fuel cell system having an ejector for mixing with a fuel gas and a flow path for supplying the fuel gas mixed by the ejector to the fuel electrode, the ejector is one throat in which a raw fuel gas and an exhaust gas are mixed. Section and two nozzles that are respectively opened at the inlet of the throat section, and a pressure adjusting valve that adjusts the supply pressure of the raw fuel gas for each nozzle is provided upstream of the two nozzles. Since the nozzle diameter can be made variable without providing a movable part inside the ejector, the operating area of the ejector can be expanded with a simple configuration while suppressing hydrogen gas leakage. There is an effect that.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the two nozzles have different diameters, and the tip of the nozzle having a smaller diameter is the tip of the nozzle having a larger diameter. By arranging it close to the inlet of the throat part, the raw fuel gas injected from the small diameter nozzle is suppressed from being decelerated due to friction in the throat when the amount of hydrogen supply is small and the load is low, so the kinetic energy of the raw fuel gas is reduced. It can be effectively used, and at the time of high load where the raw fuel gas is injected from the large diameter nozzle in addition to the small diameter nozzle, it is possible to secure the space between the nozzle and the throat for the exhaust gas to flow in, and Since the mixing distance of the exhaust gas can be secured, there is an effect that a circulation ratio above a certain level can be obtained in a wide operating region.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, in the two nozzles, a nozzle having a large diameter includes a nozzle having a small diameter. The coaxial arrangement has an effect that the raw fuel gas injected from both nozzles can be reasonably introduced into the throat portion without interfering with each other.

According to the invention of claim 4, in addition to the effects of the invention of claims 1 to 3, the ratio of the raw fuel gas controllable flow rates in the two pressure adjusting valves arranged upstream of the nozzles Is substantially equal to the ratio of the opening area of the nozzle portion, so that it is possible to control the supply amount of the raw fuel gas in a wide operating range without impairing the controllability of the flow rate of the raw fuel gas passing through the nozzle. The effect is that

According to the invention of claim 5, in addition to the effects of the inventions of claims 2 to 4, when the output of the fuel cell system is lower than a predetermined value and the load is low, the small diameter of the two nozzles is used. The raw fuel gas is supplied from the nozzle of No. 2, and when the output of the fuel cell system is equal to or more than a predetermined value, the raw fuel gas is controlled to be supplied from the large-diameter nozzle in addition to the small-diameter nozzle. There is an effect that the controllability of the supplied raw fuel gas can be maintained while securing the circulation amount of the exhaust gas in the region.

According to the invention described in claim 6, in addition to the effects of the invention described in claims 1 to 5, the raw fuel gas is supplied from both of the two nozzles at the transition time when the output of the fuel cell system increases. Since it is controlled to supply hydrogen, the amount of hydrogen supplied to the fuel electrode can be increased in response to a sudden increase in output demand, and the pressure at the fuel electrode can be increased rapidly until the power generation amount that has increased sharply is met. There is an effect that can be.

According to the invention described in claim 7, in the ejector for mixing the first fluid and the second fluid, the ejector has one throat portion for mixing the first fluid and the second fluid,
By having coaxially two nozzles of different diameters with one end opened at the throat inlet, the tip of the small diameter nozzle is arranged closer to the throat inlet than the tip of the large diameter nozzle. The effect is that the operating area of the ejector can be expanded.

[0024]

FIG. 1 is a system configuration diagram showing the configuration of a first embodiment of a fuel cell system according to the present invention, particularly for an electric vehicle in which load fluctuation is large from idle to high speed running. It is suitable as a power source.

In FIG. 1, a fuel cell main body (hereinafter referred to as a stack) 1 includes a fuel electrode 2 and an air electrode 3. In practice, the stack 1 is equipped with cooling system piping, power output lines, various sensors, etc., but only the gas system is shown in this figure.

The fuel electrode 2 and the air electrode 3 are joined inside the stack 1 with an electrolyte membrane made of a solid polymer therebetween, and hydrogen is ionized at the fuel electrode 2 to separate into hydrogen ions and electrons. The hydrogen ions move from the fuel electrode 2 side to the air electrode 3 side in the electrolyte membrane using water as a medium, and the electrons return from the fuel electrode 2 to the air electrode 3 through the external load circuit, and hydrogen ions, electrons, and oxygen DC power generation is performed by an electrochemical reaction in which water is combined with the air electrode 3.

In this embodiment, a method of directly holding hydrogen 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 more the traveling distance per filling can be extended and the tank volume can be reduced. Since it is difficult to control the supply pressure from the high pressure of the hydrogen storage tank 4 to the stack 1 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, the hydrogen gas as the raw fuel gas is supplied to the two pressure adjusting valves 6a and 6b arranged in parallel.

The pressure adjusting valves 6a and 6b are connected to the ejector 7
Is connected to a first supply port 9a and a second supply port 9b which communicate with two nozzles provided in
By individually controlling the hydrogen gas pressure supplied to the two nozzles,
Hydrogen gas is sent to the circulation line containing the stack 1.

In the ejector 7, a fuel gas, which is a mixture of hydrogen gas supplied from the hydrogen storage tank 4 and exhaust gas having a low pressure and a low hydrogen content after passing through the fuel electrode 2 of the stack 1, is caused to flow downstream. , Then fuel gas humidifier 13
Water vapor necessary for the reaction in the electrolytic film in the stack 1 when passing through and is heated to a temperature suitable for the reaction, and then flows into the fuel electrode 2 of the stack 1.

The fuel gas 2 of the stack 1 consumes hydrogen, and the exhaust gas containing the remaining residual hydrogen is discharged from the stack 1, sent to the third supply port 11 of the ejector 7, and circulated again. A branch portion 14 is provided in the middle of the pipe from the stack 1 to the third supply port 11 of the ejector 7, and is open to the outside via a purge valve 15. If the power output demand of the stack suddenly becomes small, the hydrogen in the circulation line cannot be completely consumed by the stack. At that time, the purge valve 15 is opened to release the surplus hydrogen gas to the outside.

On the other hand, although not shown in the figure, a compressor for taking in the atmosphere, compressing it and sending it to the air line is installed upstream of the stack to the air electrode. Similarly to hydrogen, the air compressed by the compressor passes through the humidifier, is humidified to a substantially saturated state, and then flows into the air electrode 3 of the stack 1. Then, the air gas left after consuming the oxygen component in the air at the air electrode 3 passes through the pressure control valve of the air line and is discharged to the atmosphere together with the moisture produced by the reaction in the stack 1. The air pressure is controlled by the pressure control valve so that the air pressure becomes a predetermined pressure as required.

The water produced at the air electrode is recovered by a water recovery device (not shown) provided in the middle of the air line, and the recovered water is supplied to the humidifier 13 by a pressure pump.
It is reused as cooling water for the stack 1.

The pressure regulating valves 6a and 6b also have a role of controlling the flow rate of hydrogen supplied to the stack 1, and are arranged upstream of the stack 1 so that the hydrogen pressure of the fuel electrode 2 becomes a value suitable for the amount of power generation. While measuring the output value of the arranged pressure sensor 20, the amount of hydrogen existing in the hydrogen gas circulation system is adjusted so as to be a predetermined value determined according to the required load, and the amount of hydrogen consumed by power generation is replenished. Thus, while measuring the output values of the pressure sensors 19a and 19b provided downstream of the pressure adjusting valves 6a and 6b, respectively, the pressure adjusting valve 6a is adjusted to a predetermined value according to the amount of power generation.
And 6b open control is performed.

The ratio of controllable flow rates in the pressure adjusting valves 6a and 6b is such that the small diameter nozzle 21 and the large diameter nozzle 3 which will be described later will be described.
It is almost equal to the ratio of the opening area to 1.

FIG. 2 shows a sectional structure of the ejector 7 in this embodiment. In the same figure, the ejector 7
Has one throat 29 in which the raw fuel gas and the exhaust gas are mixed, and two nozzles 21 and 31 having different nozzle diameters which are respectively opened at the inlets of the throat 29. Of the two nozzles 21, 31, the tip of the small diameter nozzle 21 is arranged closer to the inlet of the throat 29 than the tip of the large diameter nozzle 31. Further, the large diameter nozzle 31 is coaxially arranged so as to include the small diameter nozzle 21.

The ejector 7 is provided with a first supply port 9a communicating with the small diameter nozzle 21, a second supply port 9b communicating with the large diameter nozzle 31, and a third supply port 11 which is a suction side connection port. The hydrogen gas, which is the raw fuel gas, is supplied from the first supply port 9a and the second supply port 9b, and the exhaust circulation gas from the fuel electrode 2 (FIG. 1) is sucked from the third supply port 11. The pipe is connected.

The parts constituting the ejector 7 are the first intake portion 22 in which the small-diameter nozzle 21 and the first supply port 9a for supplying the raw fuel gas communicate with each other, and the O-ring 2 connecting the first intake portion 22.
By assembling together with 3, the large-diameter nozzle 31 and the second intake part 26 configured to communicate with the first supply port 9a for supplying the raw fuel gas, and the second intake part 26 are connected to the O-ring 2.
When assembled together with 7, the body portion 28 forms a space that connects the third supply port 11 and the discharge port 12 through which the exhaust fuel gas circulates.

The body portion 28 has a throat 29 for mixing the raw fuel gas and the exhaust fuel gas and a diffuser 30 for reducing the flow velocity of the mixed flow to recover the pressure. Small diameter nozzle 21, or small diameter nozzle 21 and large diameter nozzle 3
The raw fuel gas flow injected from No. 1 has its flow velocity increased by being throttled in front of the throat 29, and due to this flow velocity increase, a negative pressure is generated at the third supply port 11, and the first supply port 9a and the first supply port 9a and The exhaust gas is sucked from the suction side third supply port 11 by the flow from the 2 supply port 9b, and the throat 2
A mixed flow occurs inside 9.

FIG. 3 shows the characteristics of the ejector when the diameters of the throat portion and the body portion are the same and the diameters of the nozzle portion are different, (a) the relationship between the supply gas flow rate Qin and the supply gas pressure Pin, and (b) ) The circulation ratio R (the ratio of the circulation gas flow rate Qsu and the supply gas flow rate Qin) to the supply gas flow rate Qin is shown.

FIG. 3B is a diagram showing the relationship of the circulation ratio R to the supply gas flow rate Qin in the ejector.
The case of a small diameter nozzle is shown by a thin line, and the case of a large diameter nozzle is shown by a thick line. The supply gas flow rate Qin at which the circulation starts decreases as the nozzle diameter decreases, and the maximum value of the circulation ratio R also increases when the supply gas flow rate Qin increases.

However, as shown in FIG. 3 (a), the supply pressure of the hydrogen gas supply system is regulated by a system such as a pressure reducing valve, and while the gas flow rate is secured by the pressure adjusting valve, the first and second The maximum pressure that can be supplied to the supply port is limited by Pinmax. Therefore, from the viewpoint of the circulation ratio, the smaller the nozzle diameter is, the better the characteristic is, but the amount of gas that can be supplied is reduced.

Therefore, the flow rate range from the hydrogen gas supply Qmin at the time of load required in the system idle state when the vehicle is stopped to the amount Qmax of supply hydrogen gas at the maximum load of the system required at high speed running or acceleration is very large. Since it is wide, the circulation ratio R required to maintain a good power generation state of the stack
Maintaining min is difficult with one nozzle.

FIG. 4 shows the characteristics when the ejector used in this embodiment is used, as in FIG. First, the small diameter nozzle 2 is operated at the maximum pressure Pinmax that can be applied to the ejector upstream from the gas flow rate Qmin corresponding to the minimum operation load of the system.
From 1 to the gas flow rate Q1 that can be supplied to the circulation system, the pressure regulating valve 6a is controlled to be opened to supply the raw fuel gas. At that time, the circulation ratio R shown by the thin line in FIG. 4 is obtained, and the circulation ratio equal to or higher than the minimum required value Rmin of the stack can be obtained.

When the required power generation amount increases and the required supply amount of the raw fuel gas exceeds Q1, the supply amount Q from the small diameter nozzle 21.
In addition to 1, the pressure control valve 6b is controlled to be opened to control the second supply port 9b.
The gas pressure is increased to supply the insufficient raw fuel gas from the large diameter nozzle 31. At this time, the large diameter nozzle 31 is
The pressures of the supply port 9a and the second supply port 9b are both Pinma.
In the case of x, the diameter is set so that the raw fuel gas amount Qmax required at the time of requesting the maximum power generation amount can be supplied.

The circulation ratio R when the pressure control valve 6b is controlled to be open is the sum of the circulation by the flow from the small diameter nozzle 21 shown by the thin broken line and the circulation by the flow from the large diameter nozzle 31 shown by the thick broken line. Since it becomes a certain thick line, it is possible to secure the necessary circulation ratio Rmin in all stack operating regions.

Pressure regulating valve 6 arranged upstream of the ejector 7.
In order to improve the accuracy of pressure control, a and 6b are set so that when they are controlled to be fully opened, the amount of raw fuel gas required is a constant pressure controlled by the pressure reducing valve 5. Is desired. Further, the nozzle diameter of the ejector is set so that the flow in the nozzle section becomes sonic when the supply gas amount increases, so that a high circulation ratio can be obtained.

Accordingly, the ratio of the raw fuel gas controllable flow rates in the two pressure regulating valves 6a, 6b arranged upstream of the ejector 7 is made substantially equal to the ratio of the actual opening area of the small diameter nozzle 8a and the large diameter nozzle 8b. A high circulation ratio can be obtained without impairing the controllability of the raw fuel gas flow rate.

Next, the control contents of the pressure regulating valves 6a and 6b in this embodiment will be described with reference to FIGS.
FIG. 5 shows how to calculate the valve downstream pressure tPrsHeA of the pressure regulating valve 6a and the valve downstream value tPrsHeB of the pressure regulating valve 6b in order to realize the target power generation value tPWR of the fuel cell given from various vehicle conditions. FIG. 6 is a control flowchart showing whether or not the control is performed, and FIG. 6 is a graph showing an example of various tables referred to in the control flowchart.

First, in step S10, the generated power target value tPWR separately calculated based on the required load is read, and the measured value tPrsH0 of the pressure sensor 20 and the pressure sensor 19a are read.
Measured value tPrsHeA0 of the pressure sensor 19b
Read. Next, in step S12, the fuel gas pressure target value tPrsH at the fuel electrode of the fuel cell is calculated based on the power generation target value tPWR of the fuel cell. This operation is
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 the fuel gas pressure at the fuel electrode increases as the power generation target value of the fuel cell, that is, the load increases. Is set.

Next, in step S14, step S1
The fuel gas pressure target value tPrsH at the fuel electrode 2 obtained in 2 and the current fuel gas pressure tPrsH0 at the fuel electrode 2 obtained from the pressure sensor 20 and the differential pressure tPrsHd = tPrsH-tPrsH0 are calculated to adjust the pressure. The condition value is used to determine the basic pattern of control of the valves 6a and 6b.

Step S16 is a step of determining whether or not the load demand on the fuel cell has increased sharply. If the differential pressure tPrsHd is equal to or greater than a predetermined value tPrsHdH, it is determined as a rapid acceleration state and the process proceeds to step S18 to adjust the pressure. The target openings tArVA and tArVB of the valves 6a and 6b are set to the maximum values tARVAmax and tArVBmax that can be set, respectively.

When it is judged at step S16 that tPrsHd <tPrsHdL, the routine proceeds to step S20, at which tPrsHd exceeds a predetermined negative value tPrsHdL, that is, the load demand is reduced, and the purge valve 15 is controlled to open. It is determined whether it is necessary to do. tPrsHd where tPrsHd is a predetermined negative value
If it is less than L, the process proceeds to step S22, and the pressure adjusting valve 6a
The target openings tArVa and tArVB of 6 and 6b are set to the settable minimum values tArVamin and tArVBmin, respectively, and the open control information is transmitted to the control sequence of the purge valve 15.

If it is determined in step S20 that tPrsHd> tPrsHdL, it is determined that the normal control state is set, and step S24 is performed.
Then, it is determined whether or not hydrogen gas is supplied from the large diameter nozzle 31. In step S24, when tPrsH is smaller than the predetermined switching pressure tPrsH1 and the pressure value tPrsHeA0 of the first supply port 9a measured by the pressure sensor 30a is smaller than the maximum supplyable pressure tPrsHemax, the small-diameter nozzle 21 outputs It is determined that the range is only for supplying hydrogen gas, and the process proceeds to step S26.

In step S26, the generated power target value tPWR
Target value tPrsH at fuel electrode 2 required to achieve
So that the target pressure value tPrsHeA at the first supply port 9a is
Is being calculated. The target pressure value tPrsHeA is the pressure control valve 1
It is necessary to calculate the pressure loss in the fuel gas flow path from 9a to the fuel electrode 2 of the stack 1 in advance according to the flow rate, and to calculate the pressure loss as a value added to the target gas pressure of the fuel electrode 2. Therefore, as shown in FIG. 6B, it is better to use a format that is calculated in advance and referred to as a table value.

Next, at step S28, the throttle area tArVam of the basic pressure adjusting valve 6a is calculated according to tPrsHeA so that the fuel gas flow rate according to the fuel load can be obtained.
In the embodiment, it is given by a table as shown in FIG. 6C, and the throttle area tArVAm increases as the target pressure value tPrsHeA increases.
Also increases.

In step S30, the actual pressure tPrsHeA0 of the first supply port 9a measured by the pressure sensor 19a, the measured value tPrsH0 of the pressure sensor 20 indicating the fuel gas pressure supplied to the fuel electrode 2 and the value determined in step S12 are determined. A final throttle area tAr is added so that the pressure at the first supply port 9a becomes the target value tPrsHeA by adding the correction term α determined from the deviation from the target value tPrsH.
VA is calculated and the throttle area tArVB of the pressure adjusting valve 6b that controls the pressure of the second supply port 9b on the large diameter nozzle side is set to the minimum value tArVBmin.

At step S24, tPrsH is tPrsH1 or more,
Alternatively, when it is determined that tPrsHeA0 is equal to or larger than tPrsHemax, it is determined that hydrogen gas needs to be supplied from the large diameter nozzle 31 in addition to the small diameter nozzle 21, and the process proceeds to step S32.

In steps S32 and S34, step S2
6 and FIG. 6E, respectively, as in S6 and S28.
Refer to the table of, the throttle area of the pressure control valve 8b
Calculate tArVBm.

Next, in step S36, the pressure sensor 1
Actual pressure at second supply port 9b measured at 9b tPrsHeB0
And a correction term β determined from the deviation between the measured value tPrsH0 of the pressure sensor 20 and the target value tPrsH determined in step S12, and the final throttle area is adjusted so that the pressure at the second supply port 9b becomes the target value tPrsHeB. tArVB is calculated and the throttle area tArVA of the pressure adjustment valve 6a on the small diameter nozzle side is tAVAm which is the maximum value.
Set to ax.

Above, step S18, step S22,
The throttle areas of the pressure adjusting valves 6a and 6b are determined by either step S30 or step S36, information is transmitted to the pressure adjusting mechanism controller in step S38, and the control flow ends.

With the configuration described above, the required exhaust gas circulation amount can be secured for the supply gas flow rate corresponding to the wide load range, and the stable operation of the fuel cell becomes possible.

The ejector used in this embodiment is not limited to the fuel cell system, but may be the first fluid (gas or liquid).
A high mixing ratio (flow rate of the second fluid / flow rate of the first fluid) can be obtained in a wide operating range without providing a moving part in the ejector in any application for mixing the fluid with the second fluid (gas or liquid). It is clear that you can get it. In this case, an adjusting valve for adjusting the pressure or flow rate of the first fluid is provided upstream of the two nozzles of the ejector for each nozzle.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing a configuration of an embodiment of a fuel cell system according to the present invention.

FIG. 2 is a cross-sectional view showing the internal structure of the ejector in the embodiment.

FIG. 3A is a diagram illustrating supply gas pressure characteristics with respect to supply gas flow rates of a small diameter nozzle and a large diameter nozzle.
(B) It is a figure explaining the circulation ratio characteristic with respect to the supply gas flow rate of a small diameter nozzle and a large diameter nozzle.

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 control flowchart illustrating pressure control valve control in the embodiment.

6 is a graph showing an example of various tables referred to in the control flowchart of FIG.

[Explanation of symbols]

1 ... Fuel cell body (stack) 2 ... Fuel pole 3 ... Air electrode 4 ... Hydrogen storage tank 5 ... Pressure reducing valve 6a, 6b ... Pressure regulating valve 7 ... Ejector 8 ... Branch 9a ... 1st supply port 9b ... Second supply port 11 ... Third supply port 12 ... outlet 13 ... Humidifier 14 ... Branch 15 ... Purge valve 19a, 19b ... Pressure sensor 20 ... Pressure sensor

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/04 H01M 8/04 N

Claims (7)

[Claims] 1. A fuel cell main body having a fuel electrode and an air electrode, and recirculating exhaust gas discharged from the fuel electrode,
In a fuel cell system having an ejector that newly mixes with a raw fuel gas having a high hydrogen concentration, and a flow path that supplies the fuel gas mixed by the ejector to the fuel electrode, the ejector is a raw fuel gas and an exhaust gas. Mixed with 1
One throat section and two nozzles opened at the inlet of the throat section, and a pressure adjusting valve for adjusting the supply pressure of the raw fuel gas for each nozzle is provided upstream of the two nozzles. A fuel cell system characterized by the above. 2. The two nozzles having different diameters, and the tip of a nozzle having a small diameter is arranged closer to the throat inlet than the tip of a nozzle having a large diameter. Fuel cell system. 3. The fuel cell system according to claim 1, wherein the two nozzles are coaxially arranged such that a nozzle having a large diameter includes a nozzle having a small diameter. . 4. The ratio of the raw fuel gas controllable flow rates of the two pressure regulating valves arranged upstream of the nozzle is made substantially equal to the ratio of the opening area of the nozzle portion. Item 4. The fuel cell system according to any one of items 3. 5. The raw fuel gas is supplied from a nozzle having a smaller diameter among the two nozzles when the output of the fuel cell system is lower than a predetermined value, and when the output of the fuel cell system is equal to or greater than a predetermined value, the nozzle having the small diameter. The fuel cell system according to any one of claims 2 to 4, wherein the fuel cell system is controlled so that the raw fuel gas is also supplied from a large-diameter nozzle. 6. The fuel cell system according to claim 1, wherein the raw fuel gas is controlled to be supplied from both of the two nozzles during a transition of increasing output of the fuel cell system. Fuel cell system. 7. An ejector for mixing a first fluid and a second fluid, wherein the ejector has one throat part for mixing the first fluid and the second fluid, and one end is opened at an inlet of the throat part. 2 with different diameter
An ejector having two nozzles coaxially, wherein the tip of the nozzle having a smaller diameter is arranged closer to the inlet of the throat portion than the tip of the nozzle having a larger diameter.