Exhaust circulation system and method, fuel cell system and vehicle

Abstract

The invention relates to an exhaust gas circulation system, an exhaust gas circulation method, a fuel cell system and a vehicle. The system comprises a fuel cell stack, a first circulation loop and a second circulation loop, wherein the fuel cell stack comprises a stack inlet end and a stack outlet end. The first circulation loop comprises a first pipeline, a first-stage compressor and a second-stage compressor, wherein a first part of waste gas output from the outlet end of the electric pile flows back to the inlet end of the electric pile through the first pipeline, the first-stage compressor and the second-stage compressor. The second circulation loop comprises a second pipeline and a second-stage compressor; and a second part of the waste gas output from the outlet end of the electric pile flows back to the inlet end of the electric pile through the second pipeline and the second-stage compressor. According to the scheme provided by the embodiment of the invention, two different waste gas circulation loops are introduced into the two-stage pressurization system, so that the energy of the waste gas discharged from the outlet end of the electric pile can be effectively utilized, and the utilization rate of the waste gas is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of fuel cell systems, and more particularly to an exhaust gas circulation system, an exhaust gas circulation method, a fuel cell system and a vehicle. Background Art

[0002] A fuel cell system is a system that generates electricity through a chemical reaction between hydrogen at the anode and oxygen-containing gas at the cathode, and includes a proton exchange membrane. The fuel cell system has the advantages of high energy conversion efficiency and pollution-free emissions, and has important applications in many fields. For example, in the field of new energy vehicles, proton exchange membrane fuel cells using hydrogen as fuel have become a widely used type of automotive power battery.

[0003] For proton exchange membrane fuel cells, the cathode oxygen-containing gas is usually air. Since the oxygen content in the air needs to be adjusted and a gas with a certain pressure is needed to purge the water in the pipeline, the cathode exhaust gas is usually circulated for reuse. Therefore, the fuel cell system is not only provided with a cathode supply path for delivering the oxygen-containing gas to the cathode chamber of the fuel cell, but also provided with a cathode exhaust gas circulation path for leading the cathode exhaust gas out of the cathode chamber. Summary of the invention

[0004] The embodiments of the present disclosure provide an exhaust gas circulation system, an exhaust gas circulation method, a fuel cell system and a vehicle. In the embodiments of the present disclosure, by introducing two different exhaust gas circulation loops in a two-stage supercharging system, the exhaust gas energy discharged from the outlet of the fuel cell stack can be effectively utilized, thereby improving the exhaust gas utilization rate.

[0005] In a first aspect of the present disclosure, an exhaust circulation system is provided, which includes a fuel cell stack, the fuel cell stack including a stack inlet end and a stack outlet end; a first circulation loop, including a first pipeline, a first-stage compressor and a second-stage compressor, wherein a first portion of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the first pipeline, the first-stage compressor and the second-stage compressor; and a second circulation loop, including a second pipeline and a second-stage compressor, wherein a second portion of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the second pipeline and the second-stage compressor.

[0006] In a second aspect of the present disclosure, an exhaust circulation method is provided, the method comprising: providing a first circulation loop coupled to a fuel cell stack, wherein the fuel cell stack comprises a stack inlet end and a stack outlet end, the first circulation loop comprises a first pipeline, a first compressor and a second compressor, and wherein a first portion of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the first pipeline, the first compressor and the second compressor; providing a second circulation loop coupled to the fuel cell stack, wherein the second circulation loop comprises a second pipeline and a second compressor, and wherein a second portion of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the second pipeline and the second compressor.

[0007] In a third aspect of the present disclosure, a fuel cell system is provided, comprising the exhaust gas circulation system provided according to any one of the above aspects.

[0008] In a fourth aspect of the present disclosure, a vehicle is provided, comprising the fuel cell system provided according to the seventh aspect of the present disclosure.

[0009] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, wherein:

[0011] Figure 1A shows a schematic diagram of a fuel cell system in which various embodiments of the present disclosure may be implemented;

[0012] Figure 1B shows a schematic diagram of an exhaust gas circulation system according to some embodiments of the present disclosure;

[0013] Figure 1C A schematic diagram showing a cycle process based on an exhaust gas circulation system when a fuel cell stack is in operation according to some embodiments of the present disclosure is shown;

[0014] Figure 2 shows a schematic diagram of an exhaust gas circulation system according to other embodiments of the present disclosure;

[0015] Figure 3 shows a schematic diagram of an exhaust gas circulation system according to other embodiments of the present disclosure;

[0016] Figure 4 A flow chart of an exhaust gas circulation method according to some embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0017] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein, but rather these embodiments are provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure. The embodiments of the present disclosure described below with reference to the accompanying drawings are only for exemplary purposes.

[0018] In the description of the embodiments of the present disclosure, the term "including" and similar terms should be understood as open inclusion, that is, "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0019] The inventors of the present disclosure have discovered that the exhaust gas recirculation (EGR) system of the current fuel cell system needs to use an electrically driven compressor to pump the stack exhaust gas into the compressor, for example, by driving the compressor with a motor, and then transporting the exhaust gas at the stack outlet to the stack inlet. This circulation method not only has a low exhaust gas utilization rate, but also loses most of the exhaust gas energy in vain. In addition, it not only requires additional power supply and control strategy for the drive motor, but also brings potential risk of damage by liquid water to the compressor system. How to improve the utilization of exhaust gas energy, make the control of the stack exhaust gas circulation system easier, and improve the safety of the entire system is a problem that urgently needs to be solved.

[0020] To this end, an embodiment of the present disclosure proposes an exhaust circulation system, which includes a fuel cell stack, and the fuel cell stack includes a stack inlet end and a stack outlet end. The system also includes a first circulation loop, the first circulation loop includes a first pipeline, a first-stage compressor and a second-stage compressor, and the first part of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the first pipeline, the first-stage compressor and the second-stage compressor. In addition, the system also includes a second circulation loop, the second circulation loop includes a second pipeline and a second-stage compressor, and the second part of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the second pipeline and the second-stage compressor. The scheme of the present disclosure, by introducing two different exhaust gas circulation loops in the two-stage supercharging system, can effectively utilize the exhaust gas energy discharged from the stack outlet end, thereby improving the exhaust gas utilization rate.

[0021] Figure 1ASchematic diagram of an example fuel cell system 10 in which various embodiments of the present disclosure may be implemented is shown. Taking a simple fuel cell system structure as an example, the concepts of the embodiments of the present disclosure may be applied regardless of the fuel cell topology. Figure 1A As shown, in the fuel cell system 10, an anode chamber 6, a membrane electrode 7 and a cathode chamber 5 are included. The membrane electrode 7 is located between the anode chamber 6 and the cathode chamber 5, and is a semipermeable membrane used to conduct protons and isolate reactants located in the anode chamber 6 and the cathode chamber 5. The anode chamber 6, the membrane electrode 7 and the cathode chamber 5 together form a fuel cell, and the hydrogen in the anode chamber 6 and the oxygen in the cathode chamber 5 react on the membrane electrode 7 to generate current, which can be supplied to other devices through the power converter 8, such as powering a motor, charging a battery, etc.

[0022] The fuel cell system 10 also includes an anode inlet 3 and an anode outlet 4 coupled to the anode loop, a cathode inlet 1 and a cathode outlet 2 coupled to the cathode loop, which together with the anode chamber 6, the membrane electrode 7 and the cathode chamber 5 form a fuel cell system. The anode loop is used to provide hydrogen to the anode 6, and the hydrogen flows from the anode inlet 3 into the anode chamber 6. The cathode loop can provide air to the cathode chamber 5, and the oxygen in the air can react at the membrane electrode 7. The remaining waste gas, mainly nitrogen, can be discharged through the cathode outlet 2. It should be understood that Figure 1A The fuel cell system 10 shown is merely an example of an embodiment of the present disclosure and is not intended to be limiting of the present disclosure.

[0023] When adjusting the output voltage of the fuel cell, it is usually necessary to adjust the oxygen content of the air in the cathode loop, and the cathode loop also needs to maintain sufficient airflow to remove water from the pipeline, and cathode exhaust gas recirculation can meet the requirements of adjusting the oxygen content and removing water from the pipeline. However, this requires an additional drive motor to drive the compressor to pump the exhaust gas from the outlet of the battery stack into the intake pipeline. Accordingly, it is necessary to provide the drive motor with additional power supply and flexible control strategies. In addition, the exhaust gas energy cannot be utilized, and the exhaust gas energy is lost in vain. In order to achieve exhaust gas circulation, minimize the increase in the complexity of the fuel cell system, and at the same time effectively utilize the energy in the exhaust gas, the present disclosure proposes an exhaust gas circulation system, an exhaust gas circulation method, a fuel cell system and a vehicle.

[0024] Figure 1BA schematic diagram of an exhaust circulation system according to some embodiments of the present disclosure is shown. The exhaust circulation system 100 includes a fuel cell stack 104, and the fuel cell stack 104 includes a stack inlet end 115 and a stack outlet end 116. The exhaust circulation system 100 includes a first circulation loop L1 and a second circulation loop L2, and the first circulation loop L1 includes a first pipeline 118, a first compressor 102 and a second compressor 103. The second circulation loop L2 includes a second pipeline 119 and a second compressor 103. According to the gas flow direction, the intake pipeline of the exhaust circulation system 100 includes an intake end 101, a first compressor 102, and a second compressor 103 in sequence. The intake end 101 can receive gas from the outside, and the first compressor 102 is configured to perform a first compression on the gas input by the first compressor 102, and the second compressor 103 is configured to perform a second compression on the gas input by the second compressor 103. The gas enters the intake pipeline from the intake end 101, then enters the primary compressor 102 from the inlet of the primary compressor 102 for primary compression, and after being output from the outlet of the primary compressor 102, enters the inlet of the secondary compressor 103 for secondary compression, and after being output from the outlet of the secondary compressor 103, enters the stack inlet end 115 of the fuel cell stack 104. In the fuel cell stack 104, the cathode gas and the anode gas undergo a chemical reaction, and the generated exhaust gas is discharged from the stack outlet end 116 to the exhaust pipeline. The exhaust pipeline of the exhaust circulation system 100 is the pipeline between the stack outlet end 116 and the exhaust end 105. After the generated exhaust gas flows out from the stack outlet end 116, it is returned to the intake pipeline. On the one hand, a part of the output exhaust gas can be returned to the inlet of the secondary compressor 103 through the second circulation loop 119, and on the other hand, a part of the output exhaust gas can be returned to the inlet of the primary compressor 102 through the first circulation loop 118.

[0025] The position where the exhaust gas output from the stack outlet 116 is led back by the first circulation loop L1 and the second circulation loop L2 can be set at any set position of the exhaust pipeline as needed. For example, two nodes can be set on the exhaust pipeline. The form of the node is, for example, a tee pipe, a four-way pipe, etc., and the present disclosure is not limited to this. The present disclosure is illustrated by setting the first node and the second node as an example. In some embodiments, on the one hand, the mass flow rate of the exhaust gas output from the first node is obtained from the first node of the exhaust pipeline and delivered to the inlet of the first compressor 102. At this time, the first part of the exhaust gas output from the stack outlet 116 flows back to the stack inlet 115 via the first pipeline 118, the first compressor 102, and the second compressor 103. On the other hand, the mass flow rate of the exhaust gas output from the second node is obtained from the second node of the exhaust pipeline and delivered to the inlet of the second compressor 103. At this time, the second part of the exhaust gas output from the stack outlet 116 flows back to the stack inlet 115 via the second pipeline 119 and the second compressor 103. The fuel cell stack 104 includes a cathode chamber 117 and an anode chamber, and the stack inlet end 115 and the stack outlet end 116 can be arranged in the cathode chamber 117 or in the anode chamber, and the present disclosure does not limit this. In this embodiment, the cathode chamber 117 includes the stack inlet end 115 and the stack outlet end 116 as an example for explanation. The gas is a gas containing an oxidant, which can be oxygen, air, or a mixture of oxygen and a gas containing oxygen, etc., and the present disclosure does not limit this. As needed, the exhaust circulation system 100 may also include other components not shown, such as pressure sensors, temperature sensors, humidity sensors, etc., which are not limited in the present disclosure. The embodiment of the present disclosure can make more full use of the different pressure differences between the exhaust gas of different pressure levels discharged from the outlet end of the stack and the gas of different pressure levels in the intake pipeline, so that the exhaust gas of different pressure levels can be passively entered into the corresponding compressor without providing additional driving force and control strategy to pump the exhaust gas into the compressor. The embodiments of the present disclosure not only more effectively improve the exhaust gas energy utilization rate, but also reduce the control difficulty of the exhaust gas circulation loop, thereby reducing the system cost.

[0026] Figure 1C FIG. 1 shows a schematic diagram of a cycle process based on an exhaust gas circulation system when a fuel cell stack is running according to some embodiments of the present disclosure, corresponding to Figure 1B. In some embodiments, when the fuel cell stack 104 of the exhaust circulation system 100 is in operation, the first circulation loop L1 is a passive circulation loop, the connection point between the first pipeline 118 and the intake pipeline is the third node, and the pressure value P8 of the gas in the first pipeline 118 is greater than the pressure value in the intake pipeline at the third node. For ease of explanation, in some embodiments, the pressure value P8 of the gas in the first pipeline 118 is greater than the pressure value P1 of the gas in the intake end 101 as an example. This embodiment is described by taking cathode gas air as an example. According to the gas flow direction, air with pressure P, humidity H, and temperature T circulates in the intake pipeline, and exhaust gas with pressure P', humidity H', and temperature T' flows out from the stack outlet 116 and is respectively introduced back into the intake pipeline along the first circulation loop L1 and the second circulation loop L2. The gas pressure is exemplified as follows: the air pressure at the intake end 101 is P1, and the gas pressure at the stack inlet end that meets the requirements of the fuel cell stack 104 is P5, and P5 is greater than P1. After the air and the anode gas react inside the fuel cell stack 104, the pressure of the exhaust gas output from the stack outlet 116 is P10, which is usually less than P5 and greater than P1. The specific working process of the first circulation loop L1 is as follows: after the air with a pressure of P1 enters the intake pipeline from the intake end 101, it is transported to the primary compressor inlet of the primary compressor 102 along the intake pipeline. At the same time, the pressure of the exhaust gas output from the stack outlet 116 in the first circulation loop L1 in the first pipeline 118 is P8, and the exhaust gas with a pressure of P8 is also transported to the primary compressor inlet of the primary compressor 102.

[0027] In the embodiment of the present disclosure, P8 is greater than P1, and there is a pressure difference between high and low pressures, forming a pressure gradient, thereby generating a horizontal pressure gradient force that causes the gas to flow from the high pressure area to the low pressure area. Under the action of the horizontal pressure gradient force, the exhaust gas at P8 pressure flows from the high pressure area to the low pressure area. At this time, at the inlet of the first compressor of the first compressor 102, the air at P1 pressure is pumped into the inlet of the first compressor of the first compressor 102 by the exhaust gas at P8 pressure, and forms an airflow with a pressure of P2. The value of P2 is between P8 and P1, so the airflow at pressure P2 is pressurized under the operation of the first compressor 102, and an airflow with a pressure of P3 is output at the outlet of the first compressor, and P3 is greater than P2. Therefore, under the action of the horizontal pressure gradient force, the first compressor 102 passively completes the pumping action of the air at P1 pressure and the exhaust gas at P8 pressure, and this process does not require additional motor drive and control. In this embodiment, there is no specific limitation on the pressure difference between P8 and P1, as long as it can form a horizontal pressure gradient force to realize the passive first circulation loop L1.

[0028] In some embodiments, the second circulation loop L2 is a passive circulation loop, the connection point between the second pipeline 119 and the intake pipeline is the fourth node, and the pressure value P9 of the gas in the second pipeline 119 is greater than the pressure value in the intake pipeline at the fourth node. For ease of explanation, in some embodiments, the pressure value P9 of the gas in the second pipeline 119 is greater than the pressure value P3 of the gas output from the first compressor outlet 113 of the first compressor 102 as an example. According to the gas flow direction, the gas at the pressure of P3 is further transported to the secondary compressor inlet of the secondary compressor 103 along the intake pipeline. At the same time, the pressure of the exhaust gas output from the stack outlet 116 in the second circulation loop L2 in the second pipeline 119 is P9, and the exhaust gas at the pressure of P9 is also transported to the secondary compressor inlet of the secondary compressor 103 along the second circulation loop L2. In this embodiment, P9 is greater than P3, and there is a pressure difference between high and low pressures, which generates a horizontal pressure gradient force. Similar to the principle of the previous embodiment, the exhaust gas at P9 pressure flows from a place with high pressure to a place with low pressure under the action of the horizontal pressure gradient force. At this time, at the secondary compressor inlet of the secondary compressor 103, the gas at P3 pressure is pumped into the secondary compressor inlet of the secondary compressor 103 by the exhaust gas at P9 pressure, and forms an airflow at pressure P4. The pressure value of P4 is between P9 and P3, so that the airflow at pressure P4 is pressurized under the operation of the secondary compressor 103, and an airflow at pressure P5 is output at the outlet of the secondary compressor, and P5 is greater than P4. Therefore, under the action of the horizontal pressure gradient force, the secondary compressor 103 passively completes the pumping action of the gas at P3 pressure and the exhaust gas at P9 pressure without the need for additional motor drive and control. Therefore, the intake pipe, the exhaust pipe, the first circulation loop L1 and the second circulation loop L2 cooperate with each other to change the air with P1 pressure, certain temperature, humidity and oxygen content into an airflow with P5 pressure, predetermined temperature, humidity and oxygen content that can meet the requirements of the stack inlet 115 of the fuel cell stack 104, and input it into the stack inlet 115.

[0029] The fuel cell stack 104 is a closed system. In order to ensure the full reaction of the cathode gas and the anode gas and to improve the life of the stack, a filter may be provided at the air inlet end 101 to filter the input air or oxidant gas. In some embodiments, the exhaust circulation system 100 further includes a filter, which is coupled between the air inlet end 101 and the first-stage compressor 102 and is configured to receive a pressure value of the gas in the first pipeline 118 from the outside greater than the pressure value of the gas output from the filter outlet of the filter, thereby realizing a passive first circulation loop L1.

[0030] In some embodiments, the pressure value P9 of the gas in the second pipeline 119 is greater than the pressure value P8 of the gas in the first pipeline 118. The present disclosure can also be implemented as the relatively high-pressure exhaust gas output from the stack outlet 116 is taken out through the second node, and is led back to the stack inlet 115 via the second pipeline 119, the fourth node, and the secondary compressor 103. The present disclosure can also be implemented as the relatively low-pressure exhaust gas output from the stack outlet 116 is taken out through the first node, and is returned to the stack inlet 115 via the first pipeline 118, the third node, the first compressor 102, and the second compressor 103. This can further ensure that the pressure value of the gas in the first pipeline 118 is greater than the pressure value of the gas in the intake end 101 or the filter outlet, and the pressure value of the gas in the second pipeline 119 is greater than the pressure value of the gas output from the first compressor outlet 113 of the first compressor 102, thereby realizing the passive first circulation loop L1 and the second circulation loop L2. Therefore, the embodiment of the present disclosure can more fully utilize the different pressure differences between the exhaust gas of different pressure levels discharged from the stack outlet 116 and the gas of different pressure levels in the intake pipe, so that the exhaust gas of different pressure levels can passively enter the corresponding compressor without providing additional driving force to pump the exhaust gas into the compressor. The embodiment of the present disclosure, while more effectively improving the exhaust gas energy utilization rate, also reduces the control difficulty of the exhaust gas circulation loop, thereby reducing the system cost.

[0031] In the embodiments of the present disclosure, each physical quantity is only given for illustration and cannot be a limitation of the embodiments of the present disclosure. For example, the pressure of the gas may include the pressure exerted by the gas on the pipe wall, or the force exerted uniformly and vertically on a unit area by the gas, which may also be referred to as pressure intensity or simply pressure, with units of Pa or Pascals, Newtons, bar, etc. The energy of the exhaust gas may include the pressure, pressure, and airflow velocity of the exhaust gas, and may also include the humidity and temperature in the exhaust gas.

[0032] Figure 2Schematic diagrams of exhaust gas circulation systems according to other embodiments of the present disclosure are shown. The first circulation loop L21 of the exhaust gas circulation system 200 also includes a turbine 220, and the first part of the exhaust gas output from the stack outlet 216 flows back to the stack inlet 215 via the turbine 220, the first pipeline 218, the first compressor 202, and the second compressor 203. The turbine 220 is coupled to the first compressor 202 through a shaft 223. In some embodiments, according to the gas flow direction, the intake pipeline includes the intake end 201, the filter 207, the first compressor 202, and the second compressor 203 in sequence. Air enters the air intake line from the air intake end 201, is first filtered by the filter 207 and output to the filter 207 outlet 211, then enters the first compressor 202 from the first compressor inlet 212 of the first compressor 202 for first-stage supercharging, and is output from the first compressor outlet 213; then enters the second compressor 203 from the second compressor inlet 214 for second-stage supercharging, and is output from the second compressor outlet 210; then enters the fuel cell stack inlet 215 of the fuel cell stack 204. The first compressor 202 includes a turbine 220, which allows the high-pressure exhaust gas discharged from the stack outlet 216 to reduce its pressure after passing through the turbine 220, so as to reduce the pressure of the exhaust gas discharged from the stack outlet 216. The turbine 220 can be coupled to the compressor through a connecting shaft, or it can be an independent turbine component, which is not limited in the present disclosure. In some embodiments, the coupling of the turbine 220 with the compressor 202 through the connecting shaft 223 is used as an example for explanation. The turbine 220 is coupled to the exhaust pipeline, and the exhaust pipeline is used to transport part or all of the exhaust gas discharged from the stack outlet 216 to the exhaust end 205. In the exhaust pipeline, part of the exhaust gas is led back to the secondary compressor inlet 214 of the secondary compressor 203 through the second circulation loop L22, and part of the exhaust gas is led back to the primary compressor inlet 212 of the primary compressor 202 through the first circulation loop L21, that is, the exhaust gas discharged from the stack outlet 216 is transported to the turbine inlet 221 of the turbine 220, and is led back from the turbine outlet 222 of the turbine 220 to the primary compressor inlet 212 of the primary compressor 202 through the second pipeline 218. Through the scheme disclosed in the present invention, on the one hand, passive circulation loops L21 and L22 are realized to make better use of the different pressure differences between exhaust gases of different pressure levels and gases of different pressure levels in the intake pipe. On the other hand, when the exhaust gas flows through the turbine 220, the high-pressure exhaust gas drives the turbine 220 to rotate, and then drives the first-stage compressor 202 to operate through the shaft 223, thereby further recovering the energy of the exhaust gas, thereby further improving the boosting efficiency of the first-stage compressor 202, thereby further improving the efficiency of the system 200.

[0033] In some embodiments, a mass flow controller may be provided in the intake pipeline, the exhaust pipeline, the first circulation loop L21, and the second circulation loop L22 to adjust the mass flow in the corresponding pipelines, for example, it may be implemented as a valve or a similar device with a regulating function. For example, V21 is provided in the intake pipeline and the two circulation loops, and the air volume flow is delivered or not delivered to the fuel cell stack 204 by opening or closing the valve V21; the required different gas mass flow and pressure are achieved by fully opening or partially opening the valve V21, and the gas mass flow that meets the requirements of the stack is delivered to the fuel cell stack 204. For example, V22 is provided in the exhaust pipeline and the two circulation loops, and the exhaust gas in the fuel cell stack 204 can be discharged, and the pressure and exhaust flow in the fuel cell stack 204 can be adjusted by fully opening, partially opening or closing the valve V22. V21 and V22 can be implemented by a two-position three-way valve, or they can be independent valve devices provided in the air pipeline. In some embodiments, valves V28 and V29 are provided in the circulation loop, which can realize flexible distribution of the ratio of the exhaust gas mass flow rate in the circulation loop and the air at the intake end 201, so as to adjust the total gas flow rate, pressure, temperature, humidity, oxygen content, etc. entering the fuel cell stack 204. Valves V28 and V29 can be implemented by two-position three-way valves, or they can be independent valve devices provided in the circulation loop, or one of them is a two-position three-way valve, and the other is a stop valve in the pipeline, and the present disclosure does not limit this. In the embodiments of the present disclosure, the mass flow rate can include the volume of the gas, the mass of the gas, or the amount of the substance of the gas, etc., which are only given schematically and cannot be a limitation on the embodiments of the present disclosure.

[0034] Figure 3 Schematic diagrams of exhaust gas circulation systems according to other embodiments of the present disclosure are shown. Figure 2 Similar to the embodiment, the first circulation loop L31 of the exhaust gas circulation system 300 may further include a turbine 320, and the first part of the exhaust gas output from the stack outlet 316 flows back to the stack inlet 315 via the turbine 320, the first pipeline 318, the first compressor 302, and the second compressor 303. Figure 2The embodiment is different in that the turbine 320 is coupled to the secondary compressor 303 through the shaft 323. In some embodiments, according to the gas flow direction, the intake pipeline includes the intake end 301, the filter 307, the primary compressor 302, and the secondary compressor 303 in sequence. The air enters the intake pipeline from the intake end 301, is first filtered by the filter 307 and output to the outlet 311 of the filter 307, then enters the primary compressor 302 from the primary compressor inlet 312 of the primary compressor 302 for primary supercharging, and is output from the primary compressor outlet 313; then enters the secondary compressor 303 from the secondary compressor inlet 314 for secondary supercharging, and is output from the secondary compressor outlet 310; then enters the fuel cell stack inlet 315 of the fuel cell stack 304. Among them, the primary compressor 302 includes a turbine 320, and the turbine 320 allows the high-pressure exhaust gas discharged from the fuel cell stack outlet 316 to reduce its pressure after passing through the turbine 320, so as to reduce the pressure of the exhaust gas discharged from the fuel cell stack outlet 316. The turbine 320 can be coupled to the compressor through a connecting shaft, or it can be an independent turbine component, which is not limited in the present disclosure. In some embodiments, the turbine 320 is coupled to the compressor 303 through a connecting shaft 323 as an example for explanation. The turbine 320 is coupled in an exhaust pipeline, and the exhaust pipeline is used to transport part or all of the exhaust gas discharged from the stack outlet 316 to the exhaust end 305. In the exhaust pipeline, part of the exhaust gas is led back to the secondary compressor inlet 314 of the secondary compressor 303 through the second circulation loop L32, and part of the exhaust gas is led back to the primary compressor inlet 312 of the primary compressor 302 through the first circulation loop L31, that is, the exhaust gas discharged from the stack outlet 316 is transported to the turbine inlet 321 of the turbine 320, and is led back to the primary compressor inlet 312 of the primary compressor 302 from the turbine outlet 322 of the turbine 320 through the second pipeline 318.

[0035] Through the scheme disclosed in the present invention, on the one hand, passive circulation loops L31 and L32 are realized to fully utilize the different pressures between exhaust gas at different pressure levels and gas at different pressure levels in the intake pipe, thereby more effectively improving the recovery of exhaust gas energy. On the other hand, when the exhaust gas flows through the turbine 320, the high-pressure exhaust gas drives the turbine 320 to rotate, and then drives the secondary compressor 303 to operate through the shaft 323, thereby further recovering the exhaust gas energy. In this way, the boosting efficiency of the secondary compressor 303 can be further improved, thereby further improving the efficiency of the system 300.

[0036] In some embodiments, a mass flow controller may be provided in the intake pipeline, the exhaust pipeline, the first circulation loop L31, and the second circulation loop L32 to adjust the mass flow in the corresponding pipelines, for example, it may be implemented as a valve or a similar device with a regulating function. For example, V31 is provided in the intake pipeline and the two circulation loops, and the air volume flow is delivered or not delivered to the fuel cell stack 304 by opening or closing the valve V31; the required different gas mass flow and pressure are achieved by fully opening or partially opening the valve V31, and the gas mass flow that meets the requirements of the stack is delivered to the fuel cell stack 304. For example, V32 is provided in the exhaust pipeline and the two circulation loops, and the exhaust gas in the fuel cell stack 304 can be discharged and the pressure and exhaust flow in the fuel cell stack 304 can be adjusted by fully opening, partially opening or closing the valve V32. In some embodiments, a bypass pipeline valve V37 connected in parallel with the fuel cell stack 304 can also be provided to reduce the mass flow through the fuel cell stack 304, and the bypass pipeline valve V37 can cooperate with the valve V31 to realize the required gas mass flow at the compressor outlet to the fuel cell stack 304. V31, V32, and V37 can be realized by a two-position three-way valve, or they can be independent valve devices arranged in the air pipeline. In some embodiments, valves V38 and V39 are arranged in the circulation loop, which can realize the flexible distribution of the ratio of the exhaust gas mass flow in the circulation loop and the air at the intake end 301, so as to adjust the total gas flow, pressure, temperature, humidity, oxygen content, etc. entering the fuel cell stack 304. Valves V38 and V39 can be realized by a two-position three-way valve, or they can be independent valve devices arranged in the circulation loop, or one of them is a two-position three-way valve, and the other is a stop valve in the pipeline, which is not limited by the present disclosure.

[0037] The present disclosure does not limit the number of turbines. In some embodiments, two turbines can also be provided, for example, respectively coupled to the first compressor 302 and the second compressor 303, so as to allow the high-pressure exhaust gas discharged from the stack outlet 316 to still meet the passive first circulation loop L31 after two decompressions. The present disclosure can make full use of the different pressure differences between the exhaust gas of different pressure levels discharged from the stack outlet 316 and the gas of different pressure levels in the intake pipe by providing two passive circulation loops in the two-stage supercharging system, so that the exhaust gas of different pressure levels can passively enter the corresponding compressor without providing additional driving force to pump the exhaust gas into the compressor, thereby making the utilization rate of the exhaust gas energy higher, and the exhaust gas can be recirculated to the stack inlet 215 of the fuel cell stack 204 without the need for additional motor drive and control to pump the exhaust gas.

[0038] Alternatively or additionally, the present disclosure is also applicable to a fuel cell system with three or more stages of supercharging. Taking the three-stage supercharging system as an example, the exhaust circulation system of the present disclosure also includes a third circulation loop, and the third circulation loop also includes a third pipeline and a three-stage compressor, wherein the third part of the exhaust gas output from the outlet of the stack flows back to the inlet of the stack via the third pipeline and the three-stage compressor. According to different system topologies of the fuel cell system, the third circulation loop can be arranged in the outer layer of the first circulation loop, or in the inner layer of the second circulation loop, or in the middle layer of the first circulation loop and the second circulation loop, and the present disclosure does not limit it.

[0039] In some embodiments, the exhaust circulation system also includes a pressure sensor for sensing the pressure of the intake line, the exhaust line, the first circulation loop, the second circulation loop, and the cathode chamber and the anode chamber in the stack. The exhaust circulation system may also include a humidity sensor for sensing the humidity of the intake line, the exhaust line, the first circulation loop, the second circulation loop, and the cathode chamber and the anode chamber in the stack. In addition, a temperature sensor may be provided to sense the temperature of the intake line, the exhaust line, the first circulation loop, the second circulation loop, and the cathode chamber and the anode chamber in the stack. The exhaust circulation system in the embodiment of the present disclosure can be used in a fuel cell system, and the fuel cell system can also be other types of fuel cell systems, which is not limited by the present disclosure. The fuel cell system in the embodiment of the present disclosure can not only be used in new energy battery vehicles to provide an energy source for the vehicle, but can also be used in other scenarios where energy needs to be provided, such as petrochemicals, etc., which is not limited by the present disclosure.

[0040] Figure 4 A flow chart of an exhaust circulation method 400 according to some embodiments of the present disclosure is shown. In some embodiments, the exhaust circulation method includes the following steps: In frame 402, the method 400 provides a first circulation loop coupled to the fuel cell stack, the fuel cell stack includes a stack inlet end and a stack outlet end, the first circulation loop includes a first pipeline, a first compressor, and a second compressor, and a first portion of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the first pipeline, the first compressor, and the second compressor. In frame 404, the method 400 provides a second circulation loop coupled to the fuel cell stack, the second circulation loop includes a second pipeline and a second compressor, and a second portion of the exhaust gas output from the stack outlet end flows back to the stack inlet end via the second pipeline and the second compressor. The exhaust circulation method of this embodiment will Figure 1BThe exhaust gas circulation system 100 shown is used as an example of a carrier for explanation. First, a first circulation loop L1 coupled to a fuel cell stack 104 is provided, the fuel cell stack 104 includes a stack inlet 115 and a stack outlet 116, the first circulation loop L1 includes a first pipeline 118, a primary compressor 102 and a secondary compressor 103, and a first part of the exhaust gas output from the stack outlet 116 flows back to the stack inlet 115 via the first pipeline 118, the primary compressor 102 and the secondary compressor 103. Then a second circulation loop L2 coupled to the fuel cell stack 104 is provided, the second circulation loop L2 includes a second pipeline 119 and a secondary compressor 103, and a second part of the exhaust gas output from the stack outlet 116 flows back to the stack inlet 115 via the second pipeline 119 and the secondary compressor 103.

[0041] In some embodiments, the exhaust circulation method further includes providing an oxidant gas to the primary compressor inlet of the primary compressor 102. When the fuel cell stack 104 is in operation, the first circulation loop L1 and the second circulation loop L2 are passive circulation loops, the pressure value of the gas in the first pipeline 118 is greater than the pressure value of the oxidant gas in the air inlet 101, and the pressure value of the gas in the second pipeline 119 is greater than the pressure value of the gas output from the primary compressor outlet 113 of the primary compressor 102. The pressure value of the gas in the second pipeline 119 is greater than the pressure value of the gas in the first pipeline 118.

[0042] The embodiments of the present disclosure can more fully utilize the different pressure differences between the exhaust gases of different pressure levels discharged from the outlet of the fuel cell stack and the gases of different pressure levels in the intake line, so that the exhaust gases of different pressure levels can all passively enter the corresponding compressors, thereby making the utilization rate of the exhaust gas energy higher. The embodiments of the present disclosure do not need to provide additional driving force to pump the exhaust gas into the compressor, thereby reducing the difficulty of controlling the exhaust gas circulation loop, thereby reducing the system cost. When the scheme of the present disclosure is applied in the new energy vehicle scenario, it can also meet the requirements of the fuel cell stack operating at low power and the fuel cell stack outputting low voltage when the vehicle is required to idle, thereby better protecting the stack and extending the life of the stack.

[0043] The functions described above herein may be performed at least in part by one or more hardware logic components. For example, without limitation, exemplary types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chip systems (SOCs), load programmable logic devices (CPLDs), and the like.

[0044] The program code for implementing the method of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code may be executed entirely on the machine, partially on the machine, partially on the machine and partially on a remote machine as a stand-alone software package, or entirely on a remote machine or server.

[0045] In the context of the present disclosure, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In addition, although each operation is depicted in a specific order, this should be understood as requiring such operations to be performed in the specific order shown or in a sequential order, or requiring that all illustrated operations should be performed to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Certain features described in the context of separate embodiments can also be implemented in a single implementation in combination. On the contrary, the various features described in the context of a single implementation can also be implemented in multiple implementations individually or in any suitable sub-combination.

[0046] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. An exhaust gas circulation system (100, 200, 300), comprising: A fuel cell stack (104, 204, 304), comprising a stack inlet (115, 215, 315) and a stack outlet (116, 216, 316); A first circulation loop (L1, L21, L31), comprising a first pipeline (118, 218, 318), a first compressor (102, 202, 302) and a second compressor (103, 203, 303), wherein a first portion of the exhaust gas output from the stack outlet (116, 216, 316) flows back to the stack inlet (115, 215, 315) via the first pipeline (118, 218, 318), the first compressor (102, 202, 302) and the second compressor (103, 203, 303); and The second circulation loop (L2, L22, L32) comprises a second pipeline (119, 219, 319) and the secondary compressor (103, 203, 303), wherein a second part of the exhaust gas output from the outlet end (116, 216, 316) of the fuel cell stack flows back to the inlet end (115, 215, 315) of the fuel cell stack via the second pipeline (119, 219, 319) and the secondary compressor (103, 203, 303).

2. The exhaust gas recirculation system (100, 200, 300) according to claim 1, wherein: The primary compressor (102, 202, 302) is configured to perform primary compression on the gas inputted by the primary compressor (102, 202, 302); and The secondary compressor (103, 203, 303) is configured to perform secondary compression on the gas inputted into the secondary compressor (103, 203, 303).

3. The exhaust gas recirculation system (100, 200, 300) according to claim 1, further comprising: An air inlet (101, 201, 301) configured to receive an oxidant gas from the outside; When the fuel cell stack (104, 204, 304) is in operation, the first circulation loop (L1, L21, L31) is a passive circulation loop, and the pressure value of the gas in the first pipeline (118, 218, 318) is greater than the pressure value of the gas at the intake end (101, 201, 301).

4. The exhaust gas recirculation system (100, 200, 300) according to claim 3, wherein: The second circulation loop (L2, L22, L32) is a passive circulation loop, and the pressure value of the gas in the second pipeline (119, 219, 319) is greater than the pressure value of the gas output from the first-stage compressor outlet (113, 213, 313) of the first-stage compressor (102, 202, 302).

5. The exhaust gas recirculation system (100, 200, 300) according to claim 4, wherein: The pressure value of the gas in the second pipeline (119, 219, 319) is greater than the pressure value of the gas in the first pipeline (118, 218, 318).

6. The exhaust gas recirculation system (100, 200, 300) according to claim 3, further comprising: A filter coupled between the air inlet (101, 201, 301) and the first-stage compressor (102, 202, 302), and configured to filter an oxidant gas received from the outside, wherein the oxidant gas includes air or oxygen; The pressure value of the gas in the first pipeline (118, 218, 318) is greater than the pressure value of the gas output from the filter outlet of the filter.

7. The exhaust gas circulation system (100, 200, 300) according to claim 1, wherein the first circulation loop (L1, L21, L31) further comprises: A turbine (220, 320), wherein the first part of the exhaust gas output from the stack outlet (116, 216, 316) flows back to the stack inlet (115, 215, 315) via the turbine (220, 320), the first pipeline (118, 218, 318), the first compressor (102, 202, 302), and the second compressor (103, 203, 303); The turbine (220, 320) is coupled to at least one of the primary compressor (102, 202, 302) and the secondary compressor (103, 203, 303) via a shaft (223, 323).

8. The exhaust gas recirculation system (100, 200, 300) according to claim 1, wherein at least one of the first pipeline (118, 218, 318) and the second pipeline (119, 219, 319) comprises: The mass flow controller is configured to adjust the mass flow in the corresponding pipeline.

9. The exhaust gas recirculation system (100, 200, 300) according to claim 1, further comprising: A third circulation loop, the third circulation loop also includes a third pipeline and a three-stage compressor, wherein a third portion of the exhaust gas output from the stack outlet (116, 216, 316) flows back to the stack inlet (115, 215, 315) via the third pipeline and the three-stage compressor.

10. The exhaust gas recirculation system (100) according to claim 1, wherein: The fuel cell stack (104, 204, 304) includes a cathode chamber (117, 217, 317), and the cathode chamber (117, 217, 317) includes the stack inlet end (115, 215, 315) and the stack outlet end (116, 216, 316).

11. An exhaust gas circulation method (400), comprising: A first circulation loop (L1, L21, L31) coupled to a fuel cell stack (104, 204, 304) is provided, wherein the fuel cell stack (104, 204, 304) includes a stack inlet end (115, 215, 315) and a stack outlet end (116, 216, 316), and the first circulation loop (L1, L21, L31) includes a first pipeline (118, 218, 318), a first compressor ( 102, 202, 302) and a secondary compressor (103, 203, 303), wherein a first portion of the exhaust gas output from the stack outlet (116, 216, 316) flows back to the stack inlet (115, 215, 315) via the first pipeline (118, 218, 318), the primary compressor (102, 202, 302), and the secondary compressor (103, 203, 303); A second circulation loop (L2, L22, L32) coupled to the fuel cell stack (104, 204, 304) is provided, wherein the second circulation loop (L2, L22, L32) includes a second pipeline (119, 219, 319) and the secondary compressor (103, 203, 303), and wherein a second portion of the exhaust gas output from the stack outlet (116, 216, 316) flows back to the stack inlet (115, 215, 315) via the second pipeline (119, 219, 319) and the secondary compressor (103, 203, 303).

12. The exhaust gas recycle method (400) according to claim 11, further comprising: An oxidant gas is provided to a first-stage compressor inlet of the first-stage compressor (102, 202, 302), wherein when the fuel cell stack (104, 204, 304) is in operation, the first circulation loop (L1, L21, L31) and the second circulation loop (L2, L22, L32) are passive circulation loops, the pressure value of the gas in the first pipeline (118, 218, 318) is greater than the pressure value of the oxidant gas, and the pressure value of the gas in the second pipeline (119, 219, 319) is greater than the pressure value of the gas output from the first-stage compressor outlet (113, 213, 313) of the first-stage compressor (102, 202, 302).

13. The exhaust gas recycle method according to claim 12, wherein: The pressure value of the gas in the second pipeline (119, 219, 319) is greater than the pressure value of the gas in the first pipeline (118, 218, 318).

14. A fuel cell system (10), comprising the exhaust gas circulation system (100, 200, 300) according to any one of claims 1-10.

15. A vehicle comprising the fuel cell system (10) according to claim 14.

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