JP2004146240A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent rapid the temperature reduction of a fuel cell stack, and suppress the generation of condensed water. <P>SOLUTION: In a fuel cell system in which the fuel cell stack is cooled and heated cooling water is cooled by means of heat radiation in a radiator (cooling device) and circulated to the fuel cell stack, an estimation means 3 of a calorific value of the fuel cell to estimate the calorific value of the fuel cell stack based on the amount of power generation generated in the fuel cell stack and an estimation means 4 of the calorific value to estimate a heat radiation amount in the radiator are installed, and the calorific value in a target amount of power generation required for the fuel cell stack and the heat radiation amount in the radiator are compared. Then, when the heat radiation amount in the radiator is larger than the calorific value in the target amount of power generation by a prescribed amount, the amount of the power generation, in which a corrected power generation amount calculated by a difference between the calorific value and the heat radiation amount is added to the target amount of power generation, is made to be generated in the fuel cell stack. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel cell system including a fuel cell stack, and more particularly to a technique for preventing water clogging in a fuel cell called flooding.
[0002]
[Prior art]
2. Description of the Related Art Fuel cell technology that enables clean exhaust and high energy efficiency has attracted attention as a countermeasure against environmental problems in recent years, in particular, problems such as air pollution caused by automobile exhaust gas and global warming caused by carbon dioxide. 2. Description of the Related Art A fuel cell is an energy conversion system that supplies hydrogen or a hydrogen-rich reformed gas and air as a fuel to an electrolyte-electrode catalyst composite, causes an electrochemical reaction, and converts chemical energy into electric energy. Above all, solid polymer electrolyte fuel cells using solid polymer membranes as electrolytes are low-cost, easy to make compact, and have a high output density, so they are used as power sources for mobiles such as automobiles. Is expected.
[0003]
In the solid polymer electrolyte fuel cell, the solid polymer membrane not only functions as an ion conductive electrolyte by being saturated with water, but also has a function of separating hydrogen and oxygen. If the water content of the solid polymer membrane is insufficient, the ionic resistance will increase, and hydrogen and oxygen will be mixed, making it impossible to generate power as a fuel cell. Therefore, it is necessary to supply moisture from the outside and actively humidify the solid polymer film. For example, some humidifying means such as humidifying the supplied air is provided.
[0004]
However, depending on the operating conditions, part of the moisture contained in the humidified air may condense into water droplets, or water generated at the air electrode may remain and become droplets, which may adhere to the electrode surface. As a result, water clogging (so-called flooding) in the fuel cells constituting the fuel cell stack is caused. Flooding is a phenomenon in which the diffusion of gas to the electrode is inhibited by water droplets attached to the electrode surface, and causes a voltage drop and a power drop.
[0005]
One of the causes of such flooding is a sharp drop in the temperature of the cooling water for cooling the fuel cell stack when the amount of power generation is reduced. When the temperature of the cooling water rapidly decreases and the temperature of the fuel cell stack rapidly decreases, condensed water is generated in the fuel cell, and the fuel cell is clogged with water.
[0006]
Therefore, a technique for maintaining the fuel cell operating temperature at an appropriate operating temperature has been proposed with the aim of preventing a rapid decrease in the temperature of the fuel cell cooling water (for example, see Patent Document 1). According to the technique described in Patent Document 1, in order to maintain the fuel cell operating temperature at an appropriate operating temperature, the difference between the cooling water temperature at the fuel cell stack inlet and the cooling water temperature at the fuel cell stack outlet becomes zero. In addition, the cooling water bypasses the radiator, and a part of the power generation of the fuel cell stack is supplied to the cooling water heating heater to heat the cooling water.
[0007]
[Patent Document 1]
JP-A-2002-83621
[0008]
[Problems to be solved by the invention]
In the prior art described in Patent Document 1, as a power supply condition to a cooling water heating heater for heating fuel cell cooling water, a difference between a cooling water temperature at a fuel cell stack inlet and a cooling water temperature at a fuel cell stack outlet is zero. The judgment is made based on the case that the condition has been met.
[0009]
However, the method of making a determination based on the difference in cooling water temperature does not consider fluctuations in the flow rate of cooling water at all, and cannot be said to be sufficient as a flood countermeasure. For example, the fluctuation speed of the flow rate of the cooling water is extremely slower than the fluctuation speed of the power generation amount of the fuel cell stack, and when the output of the fuel cell stack is rapidly decreased from the high output operation, the cooling water flow rate becomes the target. It takes a certain amount of time to reach the flow rate. During that time, the cooling water is rapidly cooled by the radiator, and excessively cools the fuel cell stack. When the temperature of the cooling water for cooling the fuel cell stack falls below the air temperature at the humidifier outlet or the temperature of pure water at the humidifier inlet, condensed water is generated in the fuel cell, and the fuel cell becomes clogged with water. There is a possibility that a high output cannot be taken out stably.
[0010]
Further, in the related art described in Patent Document 1, a cooling water heating heater for heating the cooling water is required. However, the addition of the cooling water heating heater is a factor that complicates the structure of the fuel cell system. Not only that, but it also increases costs.
[0011]
An object of the present invention is to solve these problems of the prior art. That is, the present invention makes it possible to accurately control the cooling by the cooling water with respect to the change in the amount of heat generated in the fuel cell stack, to prevent a rapid temperature drop of the fuel cell stack, and to suppress the generation of condensed water. An object of the present invention is to prevent water clogging of a fuel cell. It is another object of the present invention to improve the efficiency of the system, stabilize the output from the fuel cell stack, and provide a fuel cell system capable of stably extracting a high output.
[0012]
[Means for Solving the Problems]
The fuel cell system of the present invention is based on the premise that the cooling water heated by cooling the fuel cell stack is cooled by heat radiation in the cooling device and circulated to the fuel cell stack. In such a fuel cell system, a heat generation amount estimating unit that estimates a heat generation amount of the fuel cell stack based on a power generation amount of the fuel cell stack, and a heat radiation amount estimation unit that estimates a heat radiation amount in the cooling device are provided. The calorific value of the fuel cell stack estimated from the power generation amount required for the fuel cell stack is compared with the heat radiation amount of the cooling device. Here, when the heat release amount of the cooling device exceeds the heat release amount of the fuel cell stack by a predetermined amount, for example, a correction value is calculated from the difference between the heat release amount and the heat release amount, and the correction value is requested to the fuel cell stack. The power generation amount obtained by adding the correction amount to the generated power amount is generated by the fuel cell stack.
[0013]
Further, in a fuel cell system including a humidifier for humidifying the fuel cell stack, a humidifier outlet air temperature detecting means for detecting an air temperature at a humidifier outlet flowing into the fuel cell stack, and a cooling water temperature at a fuel cell stack inlet. And a fuel cell inlet cooling water temperature detecting means for detecting whether or not the cooling water temperature at the fuel cell stack inlet falls below a predetermined range based on the humidifier outlet air temperature. May be added. In this case, the correction value is calculated based on a value obtained by subtracting the cooling water temperature at the fuel cell stack inlet and a predetermined amount from the air temperature at the humidifier outlet.
[0014]
If the power generation amount obtained by adding the correction amount to the power generation amount required for the fuel cell stack is generated by the fuel cell stack, the heat generation amount in the fuel cell stack increases, and the cooling water flow reaches the target flow rate. Even if a certain amount of time is required until this, the increase in the amount of generated heat suppresses a decrease in the temperature of the cooling water during that time. Therefore, a rapid decrease in the temperature of the fuel cell stack is prevented, the generation of condensed water is suppressed, and water clogging of the fuel cell is eliminated.
[0015]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of condensed water can be prevented by preventing the rapid temperature fall of a fuel cell stack, and the water clogging of a fuel cell can be eliminated. Therefore, the output from the fuel cell stack can be stabilized, and a high output can be stably taken out. In addition, since it is not necessary to add a mechanical component such as a heater and it is possible to cope with it only by improving the control system, the structure of the fuel cell system is not complicated, and the cost does not increase. .
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a fuel cell system to which the present invention is applied will be described in detail with reference to the drawings.
[0017]
(1st Embodiment)
FIG. 1 shows a basic configuration of the fuel cell system of the present embodiment. The fuel cell system according to the present embodiment includes a fuel cell power generation unit 1 including a fuel cell stack and a fuel cell target power generation amount for setting a power generation amount (hereinafter, referred to as a target power generation amount) required for the fuel cell power generation unit 1. A calculating means 2, a fuel cell calorific value estimating means 3 for estimating a calorific value of the fuel cell stack in the fuel cell power generating means 1, a cooling device heat radiation amount estimating means 4 for estimating a heat radiation amount of a cooling device for cooling the cooling water, A calorific value / radiation amount comparing means 5 for comparing the calorific value and the heat radiation amount estimated by these, and a fuel cell power generation correction amount calculation for computing a correction amount based on a comparison result of the calorific value / radiation amount comparing means 5 Means 6. The cooling device heat radiation amount estimating means 4 includes a vehicle speed detecting means 7, an outside air temperature detecting means 8, and a cooling device inlet temperature detecting device for detecting a cooling water temperature at a cooling device inlet as information sources for estimating the heat radiation amount. Means 9 are provided.
[0018]
In the fuel cell system having the above configuration, the fuel cell target power generation amount calculation means 2 calculates the target power generation amount by adding the power generation amount for the drive request from the driver and the power generation amount for the auxiliary equipment consumption. At this time, the fuel cell heat generation amount estimating means 3 estimates the heat generation amount in the fuel cell power generation means 1 based on the target power generation amount. At the same time, the heat radiation amount estimating means 4 is based on the vehicle speed information outputted from the vehicle speed detecting means 7, the outside air temperature data outputted from the outside air temperature detecting means 8, and the cooling water temperature data outputted from the cooling device inlet temperature detecting means 9. To estimate the amount of heat radiated by the cooling device.
[0019]
Then, the calorific value estimated by the fuel cell calorific value estimating means 3 and the heat radiation amount estimated by the cooling device heat radiation amount estimating means 4 are compared by the calorific value / radiation amount comparing means 5. As a result, when it is determined that the amount of heat radiation exceeds the amount of heat generation and that the difference exceeds a predetermined amount, the information is sent to the fuel cell power generation correction amount calculating means 6. The fuel cell power generation correction amount calculating means 6 calculates a required power generation correction amount from the difference between the estimated heat generation amount and the heat release amount based on this information. The calculated power generation correction amount is input to the fuel cell power generation means 1, and the fuel cell stack generates power by adding the power generation correction amount to the target power generation amount calculated by the fuel cell target power generation amount calculation means 2.
[0020]
The above is the basic configuration of the fuel cell system of the present embodiment. Next, the specific configuration of the fuel cell power generation means 1 will be described. 2 and 3 show a specific configuration of the fuel cell power generation means 1 of the present embodiment. FIG. 2 shows a state of output control by the controller 14, and FIG. 3 shows a state of cooling control by the controller 14. Show. The controller 14 has a function of controlling each part constituting the fuel cell power generation means 1 and also has the above-described fuel cell target power generation amount calculation means 2, fuel cell calorific value estimating means 3, cooling device heat radiation amount estimating means 4 It also has a function as a calorific value / radiation amount comparing means 5 and a fuel cell power generation correction amount calculating means 6. That is, the above-described fuel cell target power generation amount calculation means 2, fuel cell heat generation amount estimation means 3, cooling device heat radiation amount estimation means 4, heat generation / heat radiation amount comparison means 5, and fuel cell power generation correction amount calculation means 6 are specifically described. Are implemented as a controller 14.
[0021]
First, as shown in FIG. 2, the fuel cell power generation means 1 includes a fuel cell stack 11, a fuel supply system for supplying hydrogen (or hydrogen-rich gas) as fuel to the fuel cell stack 11, and an oxidant (air). The air supply system supplies air, and the drive unit 12 is driven by the output from the fuel cell stack 11. The fuel cell stack 11 is provided with a cell voltage detecting device 13 for detecting the voltage of a fuel cell or a group of fuel cells, and further incorporates the output from the cell voltage detecting device 13 and is built in. A controller 14 for controlling the driving of various actuators based on the control software is provided.
[0022]
The fuel cell stack 11 has a structure in which power generation cells in which a fuel electrode to which hydrogen is supplied and an air electrode to which oxygen (air) is supplied are stacked with an electrolyte / electrode catalyst composite interposed therebetween are multi-tiered, The chemical energy is converted into electric energy by an electrochemical reaction. At the fuel electrode, when hydrogen is supplied, hydrogen is dissociated into hydrogen ions and electrons. The hydrogen ions pass through the electrolyte, and the electrons generate electric power through an external circuit and move to the air electrode. At the air electrode, oxygen in the supplied air reacts with the hydrogen ions and the electrons to produce water, which is discharged to the outside.
[0023]
As the electrolyte of the fuel cell stack 11, for example, a solid polymer electrolyte is used in consideration of high energy density, low cost, light weight, and the like. The solid polymer electrolyte is made of an ion (proton) conductive polymer membrane such as a fluororesin ion exchange membrane, and functions as an ion conductive electrolyte when saturated with water. In the case of 11, it is necessary to supply water and humidify.
[0024]
The fuel supply system includes a high-pressure hydrogen tank 21, a variable valve 22, an ejector 23, a hydrogen supply pipe 24, and a hydrogen circulation pipe 25. Then, the hydrogen gas supplied from the high-pressure hydrogen tank 21 as the hydrogen supply source is sent to the hydrogen supply pipe 24 through the variable valve 22 and the ejector 23, and is humidified in the humidifier 15, and then the fuel cell stack 11 Is supplied to the fuel electrode. The humidifier 15 is provided with a pure water path 16 for humidification and a pure water pump 17, and the humidification amount of hydrogen gas is controlled by the flow rate and temperature of the pure water.
[0025]
Not all the supplied hydrogen gas is consumed in the fuel cell stack 11, and the remaining hydrogen gas (hydrogen gas discharged from the fuel cell stack 11) is circulated by the ejector 23 through the hydrogen circulation pipe 25, The hydrogen gas is mixed with the newly supplied hydrogen gas and supplied to the fuel electrode of the fuel cell stack 11 again. A purge valve 26 and a purge pipe 27 are provided on the outlet side of the fuel cell stack 11. Impurities, nitrogen, and the like are accumulated in the hydrogen circulation pipe 25 by circulating hydrogen, which may lower the hydrogen partial pressure and reduce the efficiency of the fuel cell 11 in some cases. Therefore, by providing a purge valve 26 and a purge pipe 27 on the outlet side of the fuel cell stack 11, impurities, nitrogen and the like can be removed from the hydrogen circulation pipe 25.
[0026]
In the fuel supply system, a hydrogen pressure sensor 28 and a hydrogen flow sensor 29 are provided in the middle of the hydrogen supply pipe 24, and the pressure of hydrogen supplied to the fuel electrode of the fuel cell stack 11 is monitored by these. ing.
[0027]
The air supply system includes a compressor 31 for feeding air, an air supply pipe 32, and a throttle 33. The air as the oxidant supplied by the compressor 31 is supplied to the air electrode of the fuel cell stack 11 from the air supply pipe 32 through the humidifier 15 similarly to the hydrogen gas. Oxygen not consumed in the fuel cell stack 11 and other components in the air are discharged from the fuel cell stack 11 through the throttle 33.
[0028]
Also in this air supply system, an air pressure sensor 34 and an air flow sensor 35 are provided in the middle of the air supply pipe 32, and the pressure and flow rate of the air supplied to the fuel cell stack 11 are monitored by these. .
[0029]
In the fuel cell power generation means 1 shown in FIG. 2, air is compressed by the compressor 31 and sent to the humidifier 15. In the humidifier 15, the air is humidified by pure water supplied by the pure water pump 17, and the humidified air is sent to the fuel cell stack 11. In the fuel supply system, the flow rate is controlled by the variable valve 22 to set the fuel electrode (hydrogen electrode) pressure of the fuel cell stack 11 to a desired value. In addition, the ejector 23 merges with the reflux hydrogen, and is then sent to the humidifier 15. In the humidifier 15, hydrogen is humidified by pure water supplied by a pure water pump 17 like air, and the humidified hydrogen is sent to the fuel cell stack 11.
[0030]
The fuel cell stack 11 reacts the supplied air with hydrogen to generate electric power, and supplies electric current (electric power) to the drive unit 12 of the vehicle. The remaining air used for the reaction in the fuel cell stack 11 is discharged out of the fuel cell stack 11. At this time, pressure control is performed by the throttle 33. The remaining hydrogen used for the reaction is also discharged to the outside of the fuel cell stack 11, but is returned to the upstream of the humidifier 15 by the ejector 23 and reused for power generation.
[0031]
When the fuel cell stack 11 is operated, an air pressure sensor 34 for detecting the air pressure at the inlet of the fuel cell stack 11, an air flow sensor 35 for detecting the air flow rate, a hydrogen pressure sensor 28 for detecting the hydrogen pressure, and a hydrogen flow rate are detected. The output from the hydrogen flow sensor 29 and the cell voltage detector 13 is monitored by the controller 14, and each detected value is read by the controller 14. The controller 14 controls the compressor 31, the throttle 33, and the variable valve 22 so that each of the read detection values becomes a predetermined target value determined from the target power generation amount at that time. At the same time, an output (current value) to be taken out from the fuel cell stack 11 to the drive unit 12 is instructed in accordance with the pressure and flow rate actually realized with respect to the target value.
[0032]
In the fuel cell power generation means 1 described above, in addition to the above configuration, a cooling means for cooling the fuel cell stack 11 is provided as shown in FIG. 3, and the controller 14 also controls the cooling means. Is supposed to do it.
[0033]
The solid polymer electrolyte type fuel cell stack 11 has a relatively low operating temperature of about 60 ° C. to 100 ° C., and needs to be cooled when overheated. Therefore, the fuel cell power generation means 1 is provided with a cooling mechanism for cooling the fuel cell stack 11. The cooling mechanism has a cooling water circulation pipe 41 that circulates a refrigerant to the fuel cell stack 11, cools the fuel cell stack 11 with the cooling water, and maintains the cooling cell at an optimum temperature.
[0034]
A radiator (cooling device) 42 having a radiator fan 43 is provided in the cooling water circulation pipe 41 of the cooling mechanism, and the cooling water heated by cooling the fuel cell stack 11 is cooled here. The cooling water circulation pipe 41 is branched by a three-way valve 44 and a three-way valve 45, and a bypass pipe 46 is provided in parallel with the radiator 42. The flow rate of the cooling water flowing through the bypass pipe 46 is controlled by adjusting the three-way valve 44 and the three-way valve 45.
[0035]
In the above-described cooling mechanism, heat generated in the fuel cell stack 11 is carried away by the cooling water flowing through the cooling water circulation pipe 41 and is released outside by the radiator 42. A heat exchanger 47 is provided downstream of the radiator 42 installation position of the cooling water circulation pipe 41, between the pure water for humidification circulated through the humidifier 15 and the cooling water flowing through the cooling water circulation pipe 41. Heat exchange is performed as needed.
[0036]
In this cooling mechanism, a temperature sensor 51 for detecting the temperature of the cooling water at the inlet of the fuel cell stack 11, a temperature sensor 52 for detecting the temperature of the cooling water at the outlet of the fuel cell stack 11, and a temperature sensor for detecting the temperature of the cooling water at the inlet of the radiator 42 53, a temperature sensor 54 for detecting the temperature of the cooling water at the outlet of the radiator 42 is provided. Further, a temperature sensor 55 for detecting the air temperature at the inlet of the fuel cell stack 11 is provided in the air supply system, and a temperature sensor 56 for detecting the pure water temperature at the inlet of the humidifier 15 is installed in the humidifier.
[0037]
The controller 14 controls the cooling mechanism based on the temperatures detected by the temperature sensors 51 to 56, and further corrects the amount of power generated by the fuel cell power generation means 1. That is, the heat generation amount of the fuel cell stack 11 is compared with the heat radiation amount of the radiator 42. If the heat radiation amount of the radiator exceeds the heat generation amount of the fuel cell by a predetermined amount or more, the heat generation correction amount is calculated from the difference. Then, the fuel cell stack 11 generates power by adding the target power generation amount. Hereinafter, an operation flow of the fuel cell system according to the present embodiment will be described.
[0038]
FIG. 4 shows a main flow in the operation flow of the fuel cell system. The processing content shown in this main flow is executed every predetermined time (for example, every 10 ms) from the start of operation of the fuel cell stack 11.
[0039]
When operating the fuel cell system, first, the calorific value of the fuel cell stack 11 is estimated based on the power generation amount of the fuel cell stack 11 (step S1). At the same time, the amount of heat radiation from the radiator 42 is estimated (step S2). Then, based on the respective results estimated in steps S1 and S2, it is determined whether or not the amount of heat radiated by the radiator 42 exceeds the amount of heat generated by the fuel cell stack 11 by a predetermined amount or more (step S3). Here, when the heat release amount of the radiator 42 exceeds the heat generation amount of the fuel cell stack 11 by a predetermined amount or more, the heat release amount of the fuel cell stack 11 and the predetermined amount are subtracted from the heat release amount of the radiator 42. Is calculated as the heat generation correction amount (step S4). If the amount of heat radiation from the radiator 42 does not exceed the amount of heat generated by the fuel cell stack 11 by a predetermined amount or more, the amount of heat generation correction is set to zero (step S5).
[0040]
Next, based on the calculation result in step S4 or step S5, a power generation amount required to realize the heat generation correction amount is calculated (step S6). Then, based on the calculation result in step S6, the power generation amount corresponding to the heat generation correction amount is added to the target power generation amount (step S7), and the added power generation amount is generated by the fuel cell stack 11 (step S8).
[0041]
In the above flow, when the amount of heat generated by the radiator (cooling device) 42 exceeds the heat generation amount at the target power generation amount by a predetermined amount, the radiator fan 43, which is a device for increasing the cooling capacity of the radiator 42, is used. It is preferred to reduce the capacity.
[0042]
Here, the process of estimating the calorific value of the fuel cell stack 11 in step S1 of the main flow will be described with reference to a flowchart shown in FIG.
[0043]
In order to estimate the heat generation amount of the fuel cell stack 11, a target power generation amount of the fuel cell stack 11 is calculated by adding an auxiliary machine consumption amount to a drive request amount from a driver (step S11), and the fuel cell stack is subjected to an experiment or the like in advance. The relationship between the target power generation amount of the stack 11 and the calorific value is determined, and the calorific value of the fuel cell stack 11 is estimated based on the relationship (step S12).
[0044]
Alternatively, for example, in the fuel cell power generation means 1 shown in FIG. 3, the cooling water temperature at the inlet of the fuel cell stack 11, the cooling water temperature at the outlet of the fuel cell stack 11, the specific heat of the cooling water, and the cooling water detected by the temperature sensors 51 and 52. The calorific value of the fuel cell stack 11 can be estimated from the flow rate and the specific weight of the cooling water. In addition, the number of moles of hydrogen flowing into the fuel cell stack 11 is calculated from the internal volume of the fuel cell stack 11, the hydrogen pressure and the temperature, and the ideal power generation amount and the target calculated assuming that all of them are replaced by the power generation amount. It is also possible to estimate the calorific value of the fuel cell stack 11 by calculating the difference from the amount of power generation and calculating the calorific value from this value.
[0045]
Next, the process of estimating the amount of heat radiation in the radiator 42 in step S2 of the main flow described above will be described with reference to the flowchart of FIG.
[0046]
When estimating the heat radiation amount in the radiator 42, the outside air temperature and the vehicle speed are detected from the outside air temperature detecting means 8 and the vehicle speed detecting means 7 (step S21), and the cooling water temperature at the inlet of the radiator 42 is further detected from the temperature sensor 53. (Step 22). On the other hand, the heat radiation characteristics of the radiator 42 are determined in advance by experiments or the like, and based on the heat radiation characteristics, the outside air temperature, the vehicle speed, the cooling water temperature at the inlet of the radiator 42, and the rotation of the radiator fan 43 detected in steps S21 and S22. The heat radiation amount in the radiator 42 is estimated from the number (step S23).
[0047]
Here, the cooling water temperature at the outlet of the fuel cell stack 11 detected by the temperature sensor 52 can be used for estimating the heat radiation amount, instead of the cooling water temperature at the radiator inlet detected by the temperature sensor 53. However, in this case, from the fuel cell stack 11 outlet to the radiator 42 inlet, which is obtained from the amount of heat exchange between the fuel cell stack 11 and the radiator 42 in the cooling water circulation pipe 41 from the outside air temperature and the flow rate of the cooling water. It is necessary to consider the time to reach the cooling water until.
[0048]
Other methods for estimating the amount of heat radiation in the radiator 42 include, for example, the outside air temperature, the vehicle speed, the cooling water temperature at the inlet of the radiator 42, the cooling water flow rate of the fuel cell stack 11, and the radiator 42 detected from the temperature sensor 54. It is also possible to calculate from the cooling water temperature at the outlet and the cooling water specific weight.
[0049]
Finally, a method of calculating the heat generation correction amount in step S4 of the main flow described above will be described.
[0050]
In the calculation of the heat generation correction amount, when the heat release amount of the radiator 42 is variously changed with respect to the heat generation amount A of a certain fuel cell stack 11 by an experiment or the like, the fuel cell is stable without water clogging. Then, the heat radiation amount B of the radiator 42 from which the output can be taken out is obtained. Here, radiator heat release amount B−fuel cell stack heat release amount A = predetermined amount C, and the heat release amount A ′ of the fuel cell stack 11 and the heat release amount of the radiator 42 estimated in steps S1 and S2 of the main flow described above. Compared with B ′, when the heat radiation amount B ′ of the radiator 42 exceeds the heat generation amount A ′ of the fuel cell stack 11 by a predetermined amount C ′ or more, (radiator heat radiation amount B ′ − (fuel cell The heat generation correction amount is calculated by setting the stack heat generation amount A ′ + the predetermined amount C ′)) × (the predetermined ratio X / 100) = the heat generation correction amount.
[0051]
FIG. 7 shows a state of correction when the heat generation amount of the fuel cell stack 11 is smaller than the heat release amount of the radiator 42 minus the predetermined amount. When the power generation amount of the fuel cell stack 11 decreases due to the deceleration, the calorific value of the fuel cell stack 11 rapidly decreases. At this time, the amount of heat radiated by the radiator 42 is moderate compared to the decrease in the amount of heat generated by the fuel cell stack 11, although the amount of heat passing through the radiator 42 decreases. Therefore, the calorific value of the fuel cell stack 11 is lower than the line of the amount of heat radiated by the radiator 42 minus the predetermined amount. Therefore, the power generation amount in the fuel cell stack 11 is corrected according to the above-described flow. As a result, the calorific value of the fuel cell stack 11 to which the calorific value has been added is maintained at a level exceeding the line of the radiator 42 minus the amount of heat radiation.
[0052]
FIG. 8 shows a state in which the heat release amount of the fuel cell stack 11 exceeds the heat release amount of the radiator 42 minus the predetermined amount. In this case, after the power generation amount of the fuel cell stack 11 is reduced, the heat generation amount of the fuel cell stack 11 exceeds the line of the heat release amount of the radiator 42 minus the predetermined amount without any correction. Therefore, in this case, the correction is not performed with the heat generation correction amount set to zero.
[0053]
As described above, in the present embodiment, the heat release amount of the fuel cell stack 11 and the heat release amount of the radiator 42 are estimated, and the heat release amount of the radiator 42 exceeds the heat release amount of the fuel cell stack 11 by a predetermined amount or more. In this case, the fuel cell stack 11 generates power by adding a correction amount calculated from a difference between the heat release amount and the heat generation amount to the target power generation amount, so that a rapid temperature drop of the cooling water can be prevented. As a result, a rapid decrease in the temperature of the fuel cell stack 11 can be suppressed. Therefore, water clogging in the fuel cell unit can be effectively suppressed, the output from the fuel cell stack 11 can be stabilized, and a high output can be stably taken out.
[0054]
(Second embodiment)
The present embodiment compares the amount of heat generated by the fuel cell stack 11 with the amount of heat radiated by the radiator 42. In the case where the amount of heat radiated by the radiator 42 exceeds the amount of heat generated by the fuel cell stack 11 by a predetermined amount or more, If the temperature of the cooling water at the inlet of the fuel cell stack 11 falls below a predetermined range with reference to the temperature of the air at the outlet of the humidifier 15, a heat generation correction amount is calculated from the difference, and the power generation amount corresponding to the heat generation correction amount is calculated. Is added to the target power generation amount to cause the fuel cell stack 11 to generate power. The configuration of the fuel cell power generation means 1 is the same as that of the first embodiment shown in FIGS. 2 and 3, and the description thereof is omitted here.
[0055]
FIG. 9 shows an operation flow in the fuel cell system of the present embodiment. In the present embodiment, first, the heat generation amount of the fuel cell stack 11 is estimated (step S31), and the heat radiation amount of the radiator 42 is further estimated (step S32). Then, based on the respective results estimated in step S31 and step S32, it is determined whether or not the heat radiation amount of the radiator 42 exceeds the heat generation amount of the fuel cell stack 11 by a predetermined amount or more (step S33). Here, when the amount of heat radiated by the radiator 42 exceeds the calorific value of the fuel cell stack 11 by a predetermined amount or more, the air temperature at the outlet of the humidifier 15 further raises the cooling water temperature at the inlet of the fuel cell stack 11 by a predetermined amount or more. It is determined whether or not it exceeds (step S34).
[0056]
If the air temperature at the outlet of the humidifier 15 is higher than the cooling water temperature at the inlet of the fuel cell stack 11 by a predetermined amount or more, the cooling water temperature at the inlet of the fuel cell stack 11 and the predetermined amount are subtracted from the air temperature at the outlet of the humidifier 15. The calculated value is calculated as a heat generation correction amount (step S35). Further, when it is determined in step S33 that the heat radiation amount in the radiator 42 does not exceed the heat generation amount of the fuel cell stack 11 by a predetermined amount or more, or in step S34, the air temperature at the outlet of the humidifier 15 If it is determined that the cooling water temperature is not higher than the predetermined amount, the heat generation correction amount is set to zero (step S36).
[0057]
Next, based on the calculation result in step S35 or S36, the amount of power generation required to realize the heat generation correction amount is calculated (step S37). Then, based on the calculation result in step S37, the power generation amount corresponding to the heat generation correction amount is added to the target power generation amount (step S38), and the added power generation amount is generated by the fuel cell stack 11 (step S39).
[0058]
Here, a method of calculating the heat generation correction amount in step S37 of the above flow will be described. Similar to step S4 in the first embodiment, a certain humidifier 15 may be used in a case where the amount of heat radiated by the radiator 42 exceeds a value obtained by adding a predetermined amount to the amount of heat generated by the fuel cell stack 11 through experiments or the like in advance. When the temperature of the cooling water at the inlet of the fuel cell stack 11 is variously changed with respect to the air temperature D at the outlet, the temperature of the cooling water at the inlet of the fuel cell stack 11 can stably take out the output without causing water clogging of the fuel cells. Find E. Here, humidifier outlet air temperature D-fuel cell stack inlet cooling water temperature E = predetermined amount F, air temperature D ′ at humidifier 15 outlet detected by temperature sensor 55 and temperature sensor 51, and fuel cell stack 11 inlet From the cooling water temperature E ′, the heat generation correction amount is calculated by setting (humidifier outlet air temperature D ′ − (fuel cell inlet cooling water temperature E ′ + predetermined amount F ′)) × predetermined ratio = heat generation correction amount. .
[0059]
The humidifier 15 outlet air temperature detected by the temperature sensor 55 is substantially equivalent to the humidifier 15 inlet pure water temperature detected by the temperature sensor 56. It is also possible to realize the above calculation by substituting the 15 inlet pure water temperature. If the temperature of the pure water at the inlet of the humidifier 15 corresponding to the air temperature at the outlet of the humidifier 15 is used as the temperature detection medium, the system cost can be reduced accordingly.
[0060]
FIG. 10 shows that the amount of heat released by the radiator 42-the predetermined amount exceeds the heat generation amount of the fuel cell stack 11, and the cooling water temperature at the inlet of the fuel cell stack 11 falls below a predetermined range based on the air temperature at the outlet of the humidifier 15. 9 shows a state of correction in the case. When the power generation amount of the fuel cell stack 11 decreases due to the deceleration, the calorific value of the fuel cell stack 11 rapidly decreases. At this time, the amount of heat radiated by the radiator 42 is moderate compared to the decrease in the amount of heat generated by the fuel cell stack 11, although the amount of heat passing through the radiator 42 decreases. Therefore, the calorific value of the fuel cell stack 11 is lower than the line of the amount of heat radiated by the radiator 42 minus the predetermined amount. At this time, the temperature of the cooling water at the inlet of the fuel cell stack 11 is also rapidly decreasing, and is lower than the line of the humidifier 15 outlet air temperature minus a predetermined amount. Therefore, the power generation amount in the fuel cell stack 11 is corrected according to the above-described flow. As a result, the calorific value of the fuel cell stack 11 to which the calorific value has been added is maintained at a level exceeding the line of the radiator 42 minus the amount of heat radiation.
[0061]
FIG. 11 shows that the heat generation amount of the fuel cell stack 11 is lower than the heat release amount of the radiator 42-the predetermined amount, but the cooling water temperature at the inlet of the fuel cell stack 11 exceeds the predetermined range based on the humidifier 15 outlet air temperature. This shows a situation in which it does not fall below. In this case, since the temperature of the cooling water at the inlet of the fuel cell stack 11 is not lower than the line of the humidifier 15 air temperature minus the predetermined amount, the heat generation correction amount is set to zero and no correction is performed.
[0062]
According to the present embodiment, when the cooling water temperature at the inlet of the fuel cell stack 11 is lower than a predetermined range based on the air temperature at the outlet of the humidifier 15, the amount of heat generated by the fuel cell stack 11 is reduced by the amount of heat radiated by the radiator 42. When the amount exceeds the predetermined amount, the power generation amount to which the correction amount is added is generated by the fuel cell stack 11, so that the generation of condensed water near the inlet of the fuel cell stack 11 can be effectively prevented. Therefore, water clogging in the fuel cell unit can be effectively suppressed, the output from the fuel cell stack 11 can be stabilized, and a high output can be stably taken out.
[0063]
(Third embodiment)
In the present embodiment, the power generation correction amount is consumed by battery charging or other electric loads. Although the configuration of the fuel cell system and the operation flow of the fuel cell system are the same as those in the first embodiment, in this embodiment, the controller 14 has a function of detecting the state of charge of the battery (battery state detecting means). Have.
[0064]
The processing contents of this embodiment will be described based on the flowchart shown in FIG. In the present embodiment, first, the presence or absence of the power generation correction amount is determined by referring to the power generation correction amount calculated from the necessary heat generation correction amount in step S6 of the main flow shown in FIG. 4 (step S41). If the power generation correction amount is equal to or greater than zero, it is determined whether the battery charge state is at the upper limit (step S42). If the battery charge state is lower than the upper limit, power generation correction is performed. The corresponding amount is charged to the battery (step S43). If it is determined in step S42 that the state of charge of the battery is at the upper limit value, the power generation correction amount is consumed by the electric load, for example, the compressor 31 for supplying air (step S44). If it is determined in step S41 that the power generation correction amount is zero, the process ends.
[0065]
According to the present embodiment, when the battery charge state is detected and the battery charge state has not reached the upper limit value, and when the heat release amount of the radiator 42 exceeds the heat generation amount of the fuel cell stack 11 by a predetermined amount, By charging the battery with the power generation amount of the fuel cell stack 11 corresponding to the correction amount calculated from the difference between the heat release amount and the heat generation amount, the fuel can be effectively used. When the battery charge state has reached the upper limit value and the heat release amount of the radiator 42 exceeds the heat release amount of the fuel cell stack 11 by a predetermined amount, calculation is performed based on the difference between the heat release amount and the heat release amount. By consuming the power generation amount of the fuel cell stack 11 corresponding to the correction amount to be used by the electric load such as the compressor 31, it is possible to effectively prevent a rapid decrease in the cooling water.
[0066]
(Fourth embodiment)
The present embodiment controls the flow rates of the cooling water passing through the radiator 42 and the cooling water passing through the bypass pipe 42, and exchanges the cooling water passing through the radiator 42 with humidifying water for humidifying the fuel cell stack 11. After the heat exchange in the heater 47, the coolant is mixed with the cooling water passed through the bypass pipe 42 so that the cooling water temperature at the inlet of the fuel cell stack 11 exceeds a predetermined range based on the air temperature at the humidifier 15 outlet. Is to control the flow rate. The configuration of the fuel cell system and the operation flow of the fuel cell system are basically the same as those of the second embodiment.
[0067]
The processing content of this embodiment will be described based on the flowchart shown in FIG. In the present embodiment, first, the same determination as step S34 in the flowchart (FIG. 9) of the second embodiment is performed (step S51). As a result, the humidifier 15 outlet air temperature is compared with the fuel cell stack 11 inlet When the cooling water temperature is lower than the predetermined amount F, the three-way valves (flow control means) 44 and 45 are opened by the predetermined amount G to pass through the radiator 42 and exchange heat with pure water for humidification. The flow rate entering the vessel 47 and the flow rate bypassing the radiator 42 are controlled (step S52). Conversely, when the cooling water temperature at the inlet of the fuel cell stack 11 is higher than the air temperature at the outlet of the humidifier 15, the three-way valves 44 and 45 are closed by a predetermined amount H to pass through the radiator 42 and pass through the humidifying pure water. The flow rate entering the heat exchanger 47 and the flow rate bypassing the radiator 42 are controlled (Step S53).
[0068]
Here, an example of a method of calculating the opening degrees of the three-way valves 44 and 45 in step S52 of the above flow will be described. For example, by setting the predetermined opening G as an arbitrary constant, (the humidifier outlet air temperature− (fuel cell inlet cooling water temperature + the predetermined amount F)) × the predetermined opening G = the three-way valve opening, the three-way valve 44, 45 can be calculated. In addition, there is a method of calculating the degree of opening of the three-way valves 44 and 45 from the temperature and flow rate of the cooling water and the temperature and flow rate of the pure water for humidification in consideration of the amount of heat exchange in the heat exchanger 47.
[0069]
Further, an example of a method for calculating the opening of the three-way valves 44 and 45 in step S53 of the above-described flow will be described. In this case as well, for example, as in the case of step S52, the predetermined opening H is set to an arbitrary constant. , (Humidifier outlet air temperature− (fuel cell inlet cooling water temperature + predetermined amount F)) × predetermined opening H = three-way valve opening, whereby the opening of three-way valves 44 and 45 can be calculated. . The other calculation methods are the same as in the case of step S52.
[0070]
In the present embodiment, by controlling the degree of opening of the three-way valves 44 and 45, the flow rate of the cooling water passing through the radiator 42 and the bypass pipe 46 for bypassing the radiator 42 is controlled, and the flow rate of the cooling water passing through the radiator 42 is controlled. Then, the heat exchange between the cooling water, which has been cooled to a low temperature, and the pure water for humidification for humidifying the air flowing into the fuel cell stack 11, passes through the radiator 42 and the heat exchanger 47. The obtained cooling water is mixed with the cooling water that has passed through the bypass pipe 46. Here, the bypass piping is set such that the relationship between the cooling water temperature at the inlet of the fuel cell stack 11 and the air temperature at the outlet of the humidifier 15 is such that the cooling water temperature exceeds a predetermined range based on the air temperature at the humidifier 15 outlet. By controlling the flow rate of the cooling water passing through 46, the relationship between the pure water temperature for humidification and the cooling water temperature at the inlet of the fuel cell stack 11 can be maintained such that the temperature of the pure water for humidifying <the cooling water temperature at the fuel cell stack 11 inlet. it can. Therefore, generation of condensed water near the inlet of the fuel cell stack 11 can be effectively prevented, water clogging in the fuel cell can be effectively suppressed, and the output from the fuel cell stack 11 can be stabilized. It is possible to take out the output stably.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of a fuel cell system of the present invention.
FIG. 2 is a diagram showing a configuration example of a fuel cell power generation means provided in the fuel cell system.
FIG. 3 is a diagram showing a state in which a cooling mechanism is incorporated in the fuel cell power generation means.
FIG. 4 is a flowchart illustrating an operation flow of the fuel cell system according to the first embodiment.
FIG. 5 is a flowchart illustrating a flow of a process of estimating a calorific value of the fuel cell stack.
FIG. 6 is a flowchart illustrating a flow of a process of estimating a heat radiation amount in a radiator.
FIG. 7 is a diagram showing a state of correction when a heat generation amount of the fuel cell stack is lower than a heat radiation amount of the radiator minus a predetermined amount.
FIG. 8 is a diagram showing a case where the heat release amount of the fuel cell stack does not fall below a predetermined amount by a heat release amount of the radiator.
FIG. 9 is a flowchart illustrating an operation flow of the fuel cell system according to the second embodiment.
FIG. 10 shows the amount of heat released from the radiator—correction when the predetermined amount exceeds the heat generation amount of the fuel cell stack and the temperature of the cooling water at the fuel cell stack inlet falls below a predetermined range with reference to the humidifier outlet air temperature. It is a figure showing a situation.
FIG. 11 shows a case where the heat release amount of the fuel cell stack is lower than the heat radiation amount in the radiator-predetermined amount, but the fuel cell inlet cooling water temperature is not lower than a predetermined range based on the humidifier outlet air temperature. It is a figure showing a situation.
FIG. 12 is a flowchart illustrating a flow of a process of consuming a power generation correction amount in the fuel cell system according to the third embodiment.
FIG. 13 is a flowchart illustrating a flow of a process for controlling a flow rate of cooling water passing through a bypass pipe in the fuel cell system according to the fourth embodiment.
[Explanation of symbols]
1 Fuel cell power generation means
2 Fuel cell target power generation amount calculation means
3 Fuel cell calorific value estimation means
4 Radiation amount estimation means
6 Fuel cell power generation correction amount calculation means
7 Vehicle speed detection means
8 Outside temperature detection means
9 Cooling water cooling device inlet temperature detection means
11 Fuel cell stack
14 Controller
15 Humidifier
31 Compressor
41 Cooling water circulation piping
42 radiator
43 Radiator fan
46 Bypass piping
47 heat exchanger

Claims (16)

In a fuel cell system for cooling a fuel cell stack and cooling the heated cooling water by heat radiation in a cooling device and circulating the cooled water to the fuel cell stack,
A calorific value estimating means for estimating a calorific value of the fuel cell stack based on a power generation amount of the fuel cell stack;
A heat radiation amount estimating means for estimating a heat radiation amount in the cooling device,
If the heat release amount estimated by the heat release amount estimating unit exceeds the heat release amount estimated by the heat release amount estimating unit based on the power generation amount required for the fuel cell stack by a predetermined amount or more, the request is issued. A fuel cell system characterized in that a power generation amount obtained by adding a correction amount to a power generation amount is generated by the fuel cell stack. 2. The fuel cell according to claim 1, wherein the correction value is calculated based on a difference between a heat value estimated by the heat value estimating unit and a heat amount estimated by the heat amount estimating unit. 3. system. Vehicle speed detection means for detecting the speed of a vehicle on which the fuel cell stack is mounted,
An outside air temperature detecting means for detecting an outside air temperature;
A cooling water cooling device inlet temperature detecting means for detecting a temperature of cooling water flowing into the cooling device,
The heat radiation amount estimating unit calculates a heat radiation amount in the cooling device based on an output from the vehicle speed detecting unit, an output from the outside air temperature detecting unit, and an output from the cooling water cooling device inlet temperature detecting unit. The fuel cell system according to claim 1, wherein the estimation is performed. A humidifier for humidifying the fuel cell stack;
Humidifier outlet air temperature detecting means for detecting the air temperature of the humidifier outlet flowing into the fuel cell stack,
A fuel cell inlet cooling water temperature detecting means for detecting a cooling water temperature at the fuel cell stack inlet,
When the temperature detected by the fuel cell inlet cooling water temperature detecting means is lower than a predetermined range based on the temperature detected by the humidifier outlet air temperature detecting means, and a request is issued to the fuel cell stack. The heat generation amount estimated by the heat generation amount estimating means based on the generated electric power amount, and when the heat radiation amount estimated by the heat radiation amount estimating means exceeds a predetermined amount or more, a correction amount is added to the required power generation amount. The fuel cell system according to any one of claims 1 to 3, wherein the added power generation amount is generated by the fuel cell stack. The correction value is calculated based on a value obtained by subtracting a predetermined amount from the temperature detected by the fuel cell inlet cooling water temperature detecting means from the temperature detected by the humidifier outlet air temperature detecting means. The fuel cell system according to claim 4, wherein The fuel cell system according to any one of claims 1 to 5, wherein a battery is charged by a power generation amount corresponding to the correction amount. The battery further includes a battery state-of-charge detecting means for detecting a state of charge of the battery,
7. The fuel cell system according to claim 6, wherein when the battery state of charge detected by the battery state of charge detection unit does not reach the upper limit, the battery is charged by the amount of power generation corresponding to the correction amount. 8. 8. The fuel cell system according to claim 7, wherein when the battery state of charge detected by the battery state of charge detection unit has reached an upper limit, the amount of power generation corresponding to the correction amount is consumed by an electric load. . The fuel cell system according to claim 8, wherein the electric load is a compressor that supplies air to the fuel cell stack. Providing a bypass path that bypasses the cooling device to divide the cooling water,
The cooling water that has passed through the cooling device is heat-exchanged with humidifying water for humidifying the fuel cell stack in a heat exchanger, and then mixed with the cooling water that has passed through the bypass path. 10. The fuel cell system according to any one of claims 9 to 9. Flow rate control means for controlling the flow rate of the cooling water passing through the cooling device and the flow rate of the cooling water passing through the bypass path,
After the cooling water that has passed through the cooling device is heat-exchanged with humidifying water for humidifying the fuel cell stack in a heat exchanger, the humidifier outlet air is mixed with the cooling water that has passed through the bypass path. The fuel cell system according to claim 10, wherein the flow rate control means controls the flow rate of each cooling water so that the cooling water temperature at the fuel cell stack inlet exceeds a predetermined range based on the temperature. . When the cooling water cooling device inlet temperature detecting means is provided apart from the cooling device inlet, in a pipe from the position where the cooling water cooling device inlet temperature detecting means is provided to the cooling device inlet. 4. The fuel cell system according to claim 3, wherein a temperature of the cooling water flowing into the cooling device is estimated by calculating a heat exchange amount. 13. The fuel cell system according to claim 12, wherein the cooling water cooling device inlet temperature detecting means is provided at a cooling water outlet of the fuel cell stack. The fuel cell system according to claim 4, wherein the humidifier outlet air temperature detecting means detects the humidifier outlet air temperature using pure water flowing into the humidifier as a temperature detection medium. The heat generation amount estimated by the heat generation amount estimating means based on the power generation amount required for the fuel cell stack, when the heat radiation amount estimated by the heat radiation amount estimating means exceeds a predetermined amount or more, the cooling device of 15. The fuel cell system according to claim 1, wherein the capacity of the device for increasing the cooling capacity is reduced. The fuel cell system according to claim 15, wherein the cooling device is a radiator, and the device that increases the cooling capacity of the cooling device is a radiator fan.

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