JP2024038636A - fuel cell system - Google Patents

Abstract

The present invention provides a fuel cell system that can improve scavenging performance. The fuel gas system includes an ejector in the fuel gas supply path, and a temperature control device that controls the temperature of the fuel gas supplied to the fuel cell according to the fuel gas supply amount requested by the fuel cell. fuel cell system. [Selection diagram] Figure 2

Description

The present disclosure relates to fuel cell systems.

Various studies have been conducted on fuel cells (FC).
For example, Patent Document 1 discloses a fuel cell system that employs an ejector in a hydrogen supply system.

JP2021-099935A

When using an ejector in the fuel gas system of a fuel cell system, the circulating gas flow rate ratio (circulating gas flow rate/supplied fuel gas amount) is uniquely determined by the usage conditions, so the circulating gas flow rate can be temporarily increased during scavenging, etc. In order to achieve this, it is necessary to increase the amount of fuel gas supplied, which leads to deterioration of fuel efficiency.
In addition, since the ejector generates a circulating gas flow rate only when fuel gas is supplied, it is necessary to supply fuel gas also when scavenging the fuel cell, and supply fuel gas that is not required for power generation to the fuel cell. There is a concern that this will worsen fuel efficiency.

The present disclosure has been made in view of the above circumstances, and provides a fuel that can increase the volumetric flow rate at the inlet of the fuel cell by increasing the temperature of the fuel gas supplied to the fuel cell, thereby improving scavenging performance. The main purpose is to provide battery systems.

In the present disclosure, the fuel gas system includes an ejector in the fuel gas supply path,
A fuel cell system is provided that includes a temperature control device that controls the temperature of fuel gas supplied to a fuel cell according to the amount of fuel gas supplied from the fuel cell.

The present disclosure can provide a fuel cell system that can improve scavenging performance.

FIG. 1 is a graph showing an example of the relationship between the supply gas temperature and the rate of change in circulation flow rate (20° C. standard) when the power generation amount is constant and the ejector (ejector) circulation characteristics are constant. FIG. 2 is a schematic configuration diagram showing an example of the fuel cell system of the present disclosure.

Embodiments according to the present disclosure will be described below. Note that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of a fuel cell system that do not characterize the present disclosure) are It can be understood as a matter of design by a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the content disclosed in this specification and the common general knowledge in the field.
Furthermore, the dimensional relationships (length, width, thickness, etc.) in the figures do not reflect the actual dimensional relationships.
In this specification, "~" indicating a numerical range is used to include the numerical values written before and after it as the lower limit and upper limit.
Furthermore, any combination of upper and lower limits in the numerical range can be adopted.

In the present disclosure, the fuel gas system includes an ejector in the fuel gas supply path,
A fuel cell system is provided that includes a temperature control device that controls the temperature of fuel gas supplied to a fuel cell according to the amount of fuel gas supplied from the fuel cell.

The fuel cell system of the present disclosure has a configuration in which a temperature control device such as a heater is provided in the fuel gas system, and when the circulating gas flow rate request temporarily increases in the case of humidification, scavenging, etc., the fuel cell system supplies the fuel gas to the fuel cell. By warming the fuel gas and lowering the density of the fuel gas, the duty ratio of the injector (INJ) and the opening degree of the linear solenoid valve (LSV) are increased, and the ejector circulation gas flow rate is increased for operation.

The fuel cell system of the present disclosure can vary the fuel gas density by controlling (heating) the temperature of the fuel gas supplied to the fuel cell.
An example of control of the fuel cell system of the present disclosure is as follows.
If the circulating gas flow rate request is higher than normal (for example, if water accumulates in the cell and needs to be scavenged, or if the FC is at a high temperature and the internal humidification requirement increases), the supplied fuel gas is warmed by a temperature control device such as a heater. By warming the fuel gas, the volumetric flow rate at the fuel cell inlet can be increased, improving scavenging performance. In order to satisfy the fuel gas supply amount required by the fuel cell, the INJ valve opening time and LSV opening degree are controlled. Since the density of the supplied fuel gas decreases, the INJ ON time and LSV opening degree are increased during operation.

FIG. 1 is a graph showing an example of the relationship between the supply gas temperature and the rate of change in circulation flow rate (20° C. standard) when the power generation amount is constant and the ejector (ejector) circulation characteristics are constant. The circulating flow rate change rate is the ratio of the circulating gas flow rate to the supplied fuel gas amount.
- INJ: Since the ON time (=time during which the circulating gas flow rate is generated) becomes longer, the circulating gas flow rate increases.
・LSV: As the LSV opening degree increases, the pressure inside the nozzle increases, which increases the dynamic pressure effect of the ejector and increases the circulating gas flow rate (same effect as INJ).
As shown in FIG. 1, when the supplied gas temperature rises, the ratio of the circulating gas flow rate to the supplied fuel gas amount (=FC power generation amount) can be increased, and the humidification amount and fuel gas recirculation amount can be increased.

In this disclosure, the fuel gas and the oxidant gas are collectively referred to as a reaction gas. The reactive gas supplied to the anode is a fuel gas (anode gas), and the reactive gas supplied to the cathode is an oxidizing gas (cathode gas). The fuel gas is a gas mainly containing hydrogen, and may be hydrogen. The oxidant gas is a gas containing oxygen, and may be air or the like.

The fuel cell system of the present disclosure may be mounted on a moving body such as a vehicle. The vehicle may be a fuel cell vehicle, etc. Examples of moving bodies other than vehicles include trains, ships, and aircraft.
Furthermore, the fuel cell system of the present disclosure may be mounted on and used in a mobile object such as a vehicle that can also run on power from a secondary battery.
A mobile object may include the fuel cell system of the present disclosure. The mobile object may have a drive unit such as a motor, an inverter, a hybrid control system, and the like.
The hybrid control system may be capable of running a mobile object using both the output of the fuel cell and the power of the secondary battery.

The fuel cell system of the present disclosure includes an ejector in the fuel gas supply path (anode gas passage) in the fuel gas system, and supplies fuel gas to the fuel cell according to the fuel gas supply amount requested from the fuel cell. It has a temperature control device that controls the temperature, and connects the relief valve, injector, linear solenoid valve, gas-liquid separator, exhaust drainage valve, anode off gas passage, and anode gas passage and anode off gas passage as necessary. It may also include a circulation path or the like.
The fuel gas system has a relief valve and an ejector in this order upstream of the fuel cell (anode gas passage), and at least one of an injector and a linear solenoid valve is arranged downstream of the relief valve and upstream of the ejector. The temperature control device may be located downstream of the relief valve, upstream of the injector, upstream of the linear solenoid valve, or downstream of the fuel cell. The fuel gas may be provided with a gas-liquid separator and an exhaust drainage valve in the anode off-gas passageway, and the ejector and the gas-liquid separator may be connected by a circulation path so that the fuel gas can be circulated within the fuel gas system. When having both an injector and a linear solenoid valve, the injector and the linear solenoid valve may be arranged in parallel, and the temperature control device may be provided upstream of the injector and the linear solenoid valve. When having two injectors, the two injectors may be arranged in parallel.
The fuel cell system of the present disclosure includes a fuel gas system, and typically includes an oxidant gas system and a cooling system. The fuel gas system supplies fuel gas to at least the anode of the fuel cell, and if necessary circulates fuel off gas (anode off gas), which is reacted fuel gas discharged from the anode of the fuel cell, within the fuel gas system. Or discharge it out of the fuel gas system. The oxidizing gas system supplies oxidizing gas to at least the cathode of the fuel cell, and converts the oxidizing off gas (cathode off gas), which is the reacted oxidizing gas discharged from the cathode of the fuel cell, into oxidizing gas as necessary. Discharge outside the system. The cooling system supplies a cooling medium to at least the fuel cell, circulates the cooling medium inside and outside the fuel cell as necessary, and adjusts the temperature of the fuel cell.
The fuel off-gas may include fuel gas that has passed unreacted at the anode, water generated at the cathode, and water that has reached the anode. The fuel off-gas may include corrosive substances generated in the catalyst layer, electrolyte membrane, etc., and oxidizing gas that may be supplied to the anode during scavenging.

The ejector draws in the circulating gas flow rate by the dynamic pressure effect of the fuel gas supplied from the injector or linear solenoid valve. If the ejector has a fixed shape, the circulation ratio (circulation gas flow rate/supplied fuel gas flow rate) is uniquely determined when the operating conditions are determined.
The temperature control device controls the temperature of the fuel gas supplied to the fuel cell according to the amount of fuel gas supplied from the fuel cell. Examples of the temperature control device include a heater. The temperature control device may be provided upstream of the injector.
Examples of the fuel supply device include an injector, a linear solenoid valve, and the like.
The injector controls the amount of fuel supplied through ON-OFF times.
The linear solenoid valve controls the amount of fuel supplied by the opening degree.

The relief valve is a mechanism that releases gas such as fuel gas to the atmosphere when the primary pressure becomes excessive due to permeation of fuel gas from the pressure reducing valve. In order to prevent gas from being unnecessarily released to the atmosphere, the opening pressure of the relief valve is usually set higher than the normal primary pressure.

The fuel cell system of the present disclosure may include a control section.
Physically, the control unit includes, for example, an arithmetic processing unit such as a CPU (central processing unit), a ROM (read only memory) that stores control programs and control data processed by the CPU, and mainly a control unit. It has a storage device such as a RAM (random access memory) used as various work areas for processing, and an input/output interface. Further, the control unit may be, for example, a control device such as an electronic control unit (ECU).
The control unit may be electrically connected to an ignition switch that may be mounted on a moving object such as a vehicle. The control unit may be operable by an external power source even when the ignition switch is turned off.

The fuel cell system of the present disclosure may include a fuel cell. The fuel cell may have only one single cell, or may be a fuel cell stack, which is a laminate in which a plurality of single cells are stacked.
In this disclosure, both single cells and fuel cell stacks may be referred to as fuel cells.
The number of stacked single cells is not particularly limited, and may be, for example, from 2 to several hundreds.

A single cell of a fuel cell includes at least a membrane electrode gas diffusion layer assembly.
The membrane electrode gas diffusion layer assembly includes an anode gas diffusion layer, an anode catalyst layer, an electrolyte membrane, a cathode catalyst layer, and a cathode gas diffusion layer in this order.

The cathode (oxidant electrode) includes a cathode catalyst layer and a cathode side gas diffusion layer.
The anode (fuel electrode) includes an anode catalyst layer and an anode side gas diffusion layer.
The cathode catalyst layer and the anode catalyst layer are collectively referred to as a catalyst layer. Examples of the anode catalyst and cathode catalyst include Pt (platinum) and Ru (ruthenium), and examples of the carrier supporting the catalyst include carbon materials such as carbon.

The cathode side gas diffusion layer and the anode side gas diffusion layer are collectively referred to as a gas diffusion layer.
The gas diffusion layer may be a conductive member or the like having gas permeability.
Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous bodies such as metal mesh and foamed metal.

The electrolyte membrane may be a solid polymer electrolyte membrane. Examples of solid polymer electrolyte membranes include fluorine-based electrolyte membranes such as perfluorosulfonic acid thin films containing water, hydrocarbon-based electrolyte membranes, and the like. The electrolyte membrane may be, for example, a Nafion membrane (manufactured by DuPont).

The single cell may be provided with two separators that sandwich both sides of the membrane electrode gas diffusion layer assembly, if necessary. One of the two separators is an anode side separator and the other is a cathode side separator. In this disclosure, the anode side separator and the cathode side separator are collectively referred to as separators.
The separator may have holes constituting a manifold such as supply holes and discharge holes for allowing fluids such as reaction gas and cooling medium to flow in the stacking direction of the unit cells.
As the cooling medium, for example, a mixed solution of ethylene glycol and water can be used to prevent freezing at low temperatures.
Examples of the supply holes include fuel gas supply holes, oxidant gas supply holes, and coolant supply holes.
Examples of the exhaust hole include a fuel gas exhaust hole, an oxidant gas exhaust hole, and a coolant exhaust hole.
The separator may have a reactive gas flow path on the surface in contact with the gas diffusion layer. Further, the separator may have a cooling medium flow path for keeping the temperature of the fuel cell constant on the surface opposite to the surface in contact with the gas diffusion layer.
The separator may be a gas-impermeable conductive member or the like. The conductive member may be, for example, dense carbon made gas impermeable by compressing carbon, or a press-formed metal (eg, iron, aluminum, stainless steel, etc.) plate. Further, the separator may have a current collecting function.

The fuel cell stack may have manifolds, such as an inlet manifold with which each supply hole communicates, and an outlet manifold with which each discharge hole communicates.
Examples of the inlet manifold include an anode inlet manifold, a cathode inlet manifold, and a coolant inlet manifold.
Examples of the outlet manifold include an anode outlet manifold, a cathode outlet manifold, and a coolant outlet manifold.

FIG. 2 is a schematic configuration diagram showing an example of the fuel cell system of the present disclosure. In the fuel cell system shown in FIG. 2, the description of the oxidizing gas system and cooling system is omitted for convenience.
The fuel cell system shown in FIG. 2 includes a fuel cell (FC) stack and a fuel gas system. The fuel gas system includes a relief valve upstream of the fuel cell (anode gas passage), two injectors arranged in parallel, and an ejector in this order, and a heater is provided downstream of the relief valve and upstream of the two injectors. , a circulation system that has a gas-liquid separator and an exhaust drainage valve downstream of the fuel cell (anode off-gas passage), the ejector and the gas-liquid separator are connected by a circulation path, and the fuel gas can be circulated within the fuel gas system. A system has been constructed.

Claims (1)

In the fuel gas system, the fuel gas supply path has an ejector,
A fuel cell system includes a temperature control device that controls the temperature of fuel gas supplied to a fuel cell according to the amount of fuel gas supplied from the fuel cell.