A fuel cell multistage jet rail anode circuit and control method

Abstract

The application discloses a kind of multistage spray rail anode loop of fuel cell, and multistage spray rail is made of several hydrogen spray rails, nozzle and ejector are equipped in the hydrogen spray rail, the output end of pressure reducing valve is connected with the input end of nozzle of hydrogen spray rail, the output end of nozzle is connected with the input end of ejector in hydrogen spray rail of same stage, the output end of ejector is connected with the input end of ejector of next stage hydrogen spray rail, the output end of ejector of last stage hydrogen spray rail is connected with the input end of fuel cell stack, the fuel cell stack is connected with drainage exhaust module, the output end of drainage exhaust module is connected with the input end of ejector of first stage hydrogen spray rail;The mode of multiple spray rail combination is used, according to demand flow, different spray rail is selected to work, so that system runs long-term and remains in the situation of higher excess ratio;Ejector effect of spray rail is improved, the excess ratio demand under the operation of system large flow is satisfied;Pressure fluctuation under specific working interval is optimized.

Description

Technical Field

[0001] This invention relates to the field of fuel cell system technology, and in particular to a multi-stage injection rail anode circuit and control method for a fuel cell. Background Technology

[0002] The continuous operation of a fuel cell system requires a continuous supply of reactant gases to the anode of the fuel cell, which is achieved through a hydrogen supply device in the fuel cell anode circuit.

[0003] A typical fuel cell system's anode circuit hydrogen supply device includes a proportional valve or a hydrogen injection rail. The hydrogen injection rail usually includes an ejector and nozzle assembly. High-pressure hydrogen gas flows through the nozzle at a high velocity, creating an ejector effect in the ejector, which in turn drives the flow of low-pressure hydrogen gas in the anode circuit, ultimately entering the fuel cell stack to meet the hydrogen consumption requirements of the fuel cell system.

[0004] The design and control method of the hydrogen injection rail will significantly affect the hydrogen excess ratio and pressure control accuracy of the fuel cell anode circuit.

[0005] The anode circuit of a fuel cell is the structure that supplies hydrogen to the fuel cell. (See also...) Figure 1 This is a schematic diagram of a typical anode circuit configuration using a hydrogen injection rail, including components such as a pressure reducing valve, hydrogen injection rail, drainage and venting module, and anode pressure sensor.

[0006] Inlet hydrogen is supplied by high-pressure hydrogen from the hydrogen tank, which is then depressurized by a pressure reducing valve. The depressurized hydrogen enters the anode circuit through a nozzle. High-velocity hydrogen mixes with low-pressure hydrogen at the anode outlet of the fuel cell stack in the ejector. The ejector action drives the flow of low-pressure hydrogen. The anode pressure sensor acquires the inlet hydrogen pressure and feeds it back to the fuel cell controller. The fuel cell controller controls the nozzle operation to maintain a stable anode pressure. Low-pressure outlet hydrogen passes through a drain and vent module to remove liquid water and impurity gases. It then mixes with high-velocity hydrogen again through the ejector before re-entering the fuel cell stack to improve hydrogen utilization. Typically, the higher the proportion of ejected outlet hydrogen in the inlet hydrogen mixed by the ejector, the greater the excess ratio of the injection path and the higher the ejection efficiency.

[0007] A typical jet rail overload ratio curve is as follows: Figure 2 As shown, when the flow rate is low, the ejection excess ratio increases rapidly with the increase of the flow rate, and reaches the optimal operating point with the maximum excess ratio at a certain flow rate; further increasing the flow rate will lead to a decrease in the excess ratio.

[0008] The following problems may be encountered in a typical fuel cell system.

[0009] 1. Because the excess hydrogen ratio is affected by the nozzle diameter and hydrogen flow rate, small-diameter nozzles have a larger excess ratio at lower flow rates, while large-diameter nozzles have a larger excess ratio at higher flow rates. When using a single nozzle, the excess ratio requirement for system operation may not be met at certain flow rates.

[0010] 2. Because the hydrogen excess ratio is affected by the hydrogen pressure exiting the reactor, the higher the pressure of the extruded hydrogen, the greater the excess ratio; the lower the pressure, the smaller the excess ratio. When the system operates at a high level, the flow rate inside the reactor increases, causing a greater gas pressure drop, which further leads to excessively low extruded hydrogen pressure and an excessively low excess ratio, failing to meet the excess ratio requirements for system operation.

[0011] 3. The opening or closing of the spray rail will cause changes in the flow rate of the anode circuit, resulting in large pressure fluctuations at the anode inlet pressure and affecting the system's operating status. Summary of the Invention

[0012] The purpose of this invention is to provide a multi-stage injection rail anode circuit and control method for fuel cells, so as to overcome the shortcomings of the prior art.

[0013] To achieve the above objectives, the present invention provides the following technical solution:

[0014] This application discloses a multi-stage injection rail anode circuit for a fuel cell, including a fuel cell stack, a multi-stage injection rail, a pressure reducing valve, a drainage and venting module, and a hydrogen source. The output end of the hydrogen source is connected to the input end of the pressure reducing valve. The multi-stage injection rail is composed of several stages of hydrogen injection rails. Each hydrogen injection rail is equipped with a nozzle and an ejector. The output end of the pressure reducing valve is connected to the input end of the nozzle of the hydrogen injection rail. The output end of the nozzle is connected to the input end of the ejector in the same stage of the hydrogen injection rail. The output end of the ejector is connected to the input end of the ejector of the next stage of the hydrogen injection rail. The output end of the ejector of the last stage of the hydrogen injection rail is connected to the input end of the fuel cell stack. The output end of the fuel cell stack is connected to the input end of the drainage and venting module. The output end of the drainage and venting module is connected to the input end of the ejector of the first stage of the hydrogen injection rail. The nozzle diameter in each stage of the hydrogen injection rail increases or decreases with each stage.

[0015] Preferably, the number of stages of the hydrogen injection track in the multi-stage injection track is greater than or equal to 2.

[0016] Preferably, the output end of the ejector of the last stage hydrogen jet is equipped with an anode pressure sensor.

[0017] This invention also discloses a control method for a multi-stage injection rail anode circuit of a fuel cell, specifically including the following steps:

[0018] S1. In the anode circuit of the multi-stage injection rail of the fuel cell, obtain the number of hydrogen injection rails a, where a is greater than or equal to 2.

[0019] S2. Determine whether the nozzle diameter in each stage of the hydrogen injection rail increases or decreases sequentially; determine the opening sequence of the nozzles.

[0020] S3. Determine the number of working modes of the multi-stage spray rail; determine each working mode of the multi-stage spray rail and the switching relationship between each working mode;

[0021] S4. Turn on the nozzle and enter each working mode of the multi-stage spray rail in sequence.

[0022] Preferably, in step S2, the nozzles are opened in sequence from smallest to largest according to their orifice diameter.

[0023] Preferably, the number of working modes of the multi-stage spray rail in step S3 is 2a-1.

[0024] Preferably, when a is 2, the various working modes of the multi-stage spray rail and the switching relationship between the various working modes in step S3 are as follows:

[0025] First-level working mode: Control nozzle X1 to work and shut down the other nozzles. When the duty cycle of nozzle X1 is greater than the threshold a1, it enters the second-level working mode.

[0026] Second-level working mode: Control nozzle X2 to work and shut down the other nozzles. When the duty cycle of nozzle X2 is greater than the threshold a2, enter the third-level working mode; when the duty cycle of nozzle X2 is less than the threshold b2, return to the first-level working mode.

[0027] Third-level working mode: Keep nozzle X1 open and control nozzle X2 to work; when the duty cycle of nozzle X2 is less than the threshold b3, return to the second-level working mode.

[0028] Where nozzle Xa is the nozzle that opens in sequence a.

[0029] Preferably, when a is greater than 2, the various working modes of the multi-stage spray rail and the switching relationship between the various working modes in step S3 are as follows:

[0030] S31, First-level working mode: Control nozzle X1 to work and close the other nozzles. When the duty cycle of nozzle X1 is greater than the threshold a1, enter the second-level working mode.

[0031] S32, Second-level working mode: Control nozzle X2 to work and turn off the other nozzles. When the duty cycle of nozzle X2 is greater than the threshold a2, enter the third-level working mode; when the duty cycle of nozzle X2 is less than the threshold b2, return to the first-level working mode.

[0032] S33, Third-level working mode: Keep nozzle X1 open and control nozzle X2 to work; when the duty cycle of nozzle X2 is greater than the threshold a3, enter the next level working mode; when the duty cycle of nozzle X2 is less than the threshold b3, return to the second-level working mode.

[0033] S34. Let the loop value be b; where b is a natural number greater than 2, and the initial value of b is 3;

[0034] S35, Level 2b-2 working mode: keep nozzles X1 to Xb-2 normally open, control the spray rail Xb to work, when the duty cycle of Xb is greater than the threshold a (2b-2), enter the next level working mode; when the duty cycle of Xb is less than b (2b-2), return to the previous level working mode;

[0035] S36, Level 2b-1 working mode: keep nozzles X1 to Xb-1 ​​normally open, control the spray rail Xb to work, when the duty cycle of Xb is greater than the threshold a (2b-1), enter S27; when the duty cycle of Xb is less than b (2b-1), return to the previous working mode.

[0036] S37. Increment the value of b by 1, and repeat steps S34 and S35 as the new working mode until b equals a, at which point the loop ends.

[0037] Where nozzle Xa is the nozzle that opens in sequence a.

[0038] The beneficial effects of this invention are:

[0039] 1. By adopting a multi-rail combination method, different rails are selected to work according to the required flow rate, so that the system can maintain a high excess ratio for a long time.

[0040] 2. By adopting a multi-rail combination method, the injection effect of the injection rail is improved, which can meet the excess ratio requirements under the high flow rate of the system.

[0041] 3. Employ a multi-rail combination approach to optimize pressure fluctuations within a specific working range.

[0042] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the anode circuit structure of a current fuel cell.

[0044] Figure 2 This is a schematic diagram of a typical jet rail excess ratio curve in existing technology;

[0045] Figure 3 This is a schematic diagram of the structure of a multi-stage injection rail anode circuit for a fuel cell according to the present invention;

[0046] Figure 4 This is a structural schematic diagram of an embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram of the excess ratio of each working stage in the embodiments of the present invention;

[0048] Figure 6 This is a schematic flowchart of the control method for the multi-stage injection rail anode circuit of a fuel cell according to Embodiment 1 of the present invention;

[0049] Figure 7 This is a schematic diagram of the control method for the multi-stage injection rail anode circuit of a fuel cell according to Embodiment 2 of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0051] See Figure 3 This invention discloses a multi-stage injection rail anode circuit for a fuel cell, comprising a fuel cell stack, a multi-stage injection rail, a pressure reducing valve, a drainage and venting module, and a hydrogen source. The output end of the hydrogen source is connected to the input end of the pressure reducing valve. The multi-stage injection rail is composed of several stages of hydrogen injection rails, each containing a nozzle and an ejector. The output end of the pressure reducing valve is connected to the input end of the nozzle of the hydrogen injection rail. The output end of the nozzle is connected to the input end of the ejector in the same stage of the hydrogen injection rail. The output end of the ejector is connected to the input end of the ejector in the next stage of the hydrogen injection rail. The output end of the ejector in the last stage of the hydrogen injection rail is connected to the input end of the fuel cell stack. The output end of the fuel cell stack is connected to the input end of the drainage and venting module, and the output end of the drainage and venting module is connected to the input end of the ejector in the first stage of the hydrogen injection rail. The nozzle diameter in each stage of the hydrogen injection rail increases or decreases progressively.

[0052] In one feasible embodiment, the output of the ejector of the last stage hydrogen jet is provided with an anode pressure sensor.

[0053] The present invention discloses a control method for a multi-stage injection rail anode circuit of a fuel cell as follows:

[0054] Determine whether the nozzle diameter increases or decreases sequentially; open the nozzles sequentially from smallest to largest according to the nozzle diameter of the spray rail.

[0055] When nozzle X1 is working, and the duty cycle is greater than the threshold a1, proceed to step 2.

[0056] When nozzle X2 is working, if the duty cycle is greater than the threshold a2, proceed to step 3; if the duty cycle is less than the threshold b2, return to step 1.

[0057] Nozzle X1 is normally open, and nozzle X2 is working. When the duty cycle is greater than the threshold a3, proceed to step 4; when the duty cycle is less than the threshold b3, return to step 2.

[0058] Nozzle X1 is normally open, and nozzle X3 is working. When the duty cycle is greater than the threshold a4, proceed to step 5; when the duty cycle is less than the threshold b4, return to step 3.

[0059] Nozzles X1 and X2 are normally open, and nozzle X3 is working. When the duty cycle is greater than the threshold a5, proceed to step 6; when the duty cycle is less than the threshold b5, return to step 6.

[0060] ...

[0061] 2n-2, Nozzles X1, X2...Xn-2 are normally open, nozzle Xn is working. When the duty cycle is greater than a(2n-2), proceed to step 2n-1; when the duty cycle is less than b(2n-2), return to step 2n-3.

[0062] 2n-1, Nozzles X1, X2...Xn-1 are normally open, nozzle Xn is working. When the duty cycle is less than b(2n-1), return to step 2n-2;

[0063] Example 1:

[0064] See Figure 4 The high-pressure hydrogen gas, after passing through the pressure reducing valve, is simultaneously supplied to nozzles A and B.

[0065] When the diameter of nozzle A is smaller than that of nozzle B, the optimal operating points for the maximum excess ratio of hydrogen injection rails A and B are different, with the optimal operating flow rate of hydrogen injection rail A being lower than that of hydrogen injection rail B. Hydrogen injection rail A operates preferentially, ensuring a higher excess ratio at lower hydrogen flow rates. When the hydrogen flow rate increases, causing the excess ratio of hydrogen injection rail B to be better than that of hydrogen injection rail A, then hydrogen injection rail B switches to operation, maintaining a higher excess ratio. Furthermore, when the excess ratio of hydrogen injection rail B is insufficient to meet system requirements, hydrogen injection rail A is kept open, increasing the pressure of the entrained hydrogen entering ejector B through ejector A, thereby increasing the excess ratio of the hydrogen fed into the reactor. The excess ratio in each operating stage is as follows: Figure 5 As shown;

[0066] By comparing the set desired anode pressure with the anode pressure fed back by the pressure sensor, the operation of hydrogen injection rails A and B is controlled so that the fed-in anode pressure is close to the set desired anode pressure, thereby achieving the purpose of controlling the reactor feed pressure.

[0067] See Figure 6 Based on the operating status of hydrogen injection rails A and B, the specific control methods are as follows:

[0068] 1. Only spray rail A operates; when the duty cycle of spray rail A is greater than the threshold a1 (this threshold is determined by the intersection of the excess ratio of spray rails A and B, usually the duty cycle of spray rail A near the intersection, such as 90%), proceed to step 2.

[0069] 2. Only spray rail B operates. When the duty cycle of spray rail B is less than the threshold b2 (this threshold is determined by the intersection of the excess ratios of spray rails A and B, usually the duty cycle of spray rail B near the intersection, such as 30%), return to step 1; when the duty cycle of spray rail B is greater than the threshold a2 (this threshold is determined by the excess ratio of spray rail B, usually the duty cycle of spray rail B when the excess ratio is lower than a certain value, such as 90%), proceed to step 3. Since the diameter of nozzle B is larger than that of nozzle A, a1 > b2.

[0070] 3. Keep spray rail A in the normally open state and control the operation of spray rail B. When the duty cycle of spray rail B is less than the threshold b3 (this threshold is determined by the working duty cycle of spray rail B when step 2 just enters step 3, and is usually lower than this duty cycle, such as 60%), return to step 2; since spray rail A provides part of the flow, a2>b3.

[0071] In this embodiment, due to the presence of the volume of spray rail B, the pressure fluctuation during the operation of spray rail A in step 1 can be reduced;

[0072] Example 2:

[0073] When the diameter of nozzle A is larger than that of nozzle B, the optimal operating points for the maximum excess ratio of hydrogen injection rails A and B differ, with the optimal operating flow rate of hydrogen injection rail A being higher than that of hydrogen injection rail B. In this case, hydrogen injection rail B operates preferentially, enabling the system to achieve a higher excess ratio at lower hydrogen flow rates. When the hydrogen flow rate increases, causing the excess ratio of hydrogen injection rail A to be superior to that of hydrogen injection rail B, hydrogen injection rail A will then operate, maintaining a higher excess ratio. Furthermore, when the excess ratio of hydrogen injection rail A is insufficient to meet system requirements, hydrogen injection rail B will be kept open. Through the action of ejector A, the pressure of the ejected hydrogen entering ejector B will be intermittently increased, thereby increasing the excess ratio of hydrogen entering the reactor.

[0074] By comparing the set desired anode pressure with the anode pressure fed back by the pressure sensor, the operation of hydrogen injection rails A and B is controlled so that the fed-back anode pressure is close to the set desired anode pressure, thereby achieving the purpose of controlling the reactor feed pressure.

[0075] See Figure 7 Based on the operating status of hydrogen injection rails A and B, the specific control methods are as follows:

[0076] 1. Only spray rail B operates. When the duty cycle of spray rail B is greater than the threshold a1 (this threshold is determined by the intersection of the excess ratio of spray rails A and B, usually the duty cycle of spray rail B near the intersection, such as 90%), proceed to step 2.

[0077] 2. Only spray rail A operates. When the duty cycle of spray rail A is less than the threshold b2 (this threshold is determined by the intersection of the excess ratios of spray rails A and B, usually the duty cycle of spray rail A near the intersection, such as 30%), return to step 1; when the duty cycle of spray rail A is greater than the threshold a2 (this threshold is determined by the excess ratio of spray rail A, usually the duty cycle of spray rail A when the excess ratio is lower than a certain value, such as 90%), proceed to step 3. Since the diameter of nozzle A is larger than that of nozzle B, a1 > b2.

[0078] 3. Keep spray rail B in the normally open state and control the operation of spray rail A. When the duty cycle of spray rail A is less than the threshold b3 (this threshold is determined by the operating duty cycle of spray rail A when entering step 3 from step 2, and is usually lower than this duty cycle, such as 60%), return to step 2. Since spray rail B provides part of the flow, a2 > b3.

[0079] In this embodiment, due to the presence of the volume of the spray rail B, the pressure fluctuation during the operation of the spray rail A in step 2 can be reduced.

[0080] This invention, through nozzle rail design and control, employs a multi-stage nozzle rail combination to ensure sufficient excess ratio to meet system operating requirements at both low and high flow rates. By designing and controlling the nozzle rail and using a multi-stage nozzle rail combination, the pressure of the entrained hydrogen is increased, meeting the excess ratio requirements during high-level system operation. Furthermore, the nozzle rail design and control, employing a multi-stage nozzle rail combination, increases flow buffering, thereby reducing pressure fluctuations during nozzle rail opening and closing.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-stage injection rail anode circuit for a fuel cell, characterized in that: The system includes a fuel cell stack, multi-stage injection rails, a pressure reducing valve, a drainage and venting module, and a hydrogen source. The output end of the hydrogen source is connected to the input end of the pressure reducing valve. The multi-stage injection rails consist of several stages of hydrogen injection rails, each containing a nozzle and an ejector. The output end of the pressure reducing valve is connected to the input end of the nozzle of the hydrogen injection rail. The output end of the nozzle is connected to the input end of the ejector in the same stage of the hydrogen injection rail. The output end of the ejector is connected to the input end of the ejector in the next stage of the hydrogen injection rail. The output end of the ejector in the last stage of the hydrogen injection rail is connected to the input end of the fuel cell stack. The output end of the fuel cell stack is connected to the input end of the drainage and venting module. The output end of the drainage and venting module is connected to the input end of the ejector in the first stage of the hydrogen injection rail. The nozzle diameter in each stage of the hydrogen injection rail increases or decreases with each stage.

2. The fuel cell multi-stage injection rail anode circuit as described in claim 1, characterized in that: The number of stages of the hydrogen jetting track in the multi-stage jetting track is greater than or equal to 2.

3. The fuel cell multi-stage injection rail anode circuit as described in claim 1, characterized in that: The output end of the ejector of the final stage hydrogen jet is equipped with an anode pressure sensor.

4. The control method for a multi-stage injection rail anode circuit of a fuel cell as described in claim 1, characterized in that, Specifically, the steps include the following: S1. In the anode circuit of the multi-stage injection rail of the fuel cell, obtain the number of stages n of the hydrogen injection rail, where n is greater than or equal to 2. S2. Determine whether the nozzle diameter in each stage of the hydrogen injection rail increases or decreases sequentially; determine the opening sequence of the nozzles. S3. Determine the number of working modes for the multi-stage spray rail; Determine the working modes of the multi-stage spray rail and the switching relationships between the working modes; S4. Turn on the nozzle and enter each working mode of the multi-stage spray rail in sequence.

5. The control method for a multi-stage injection rail anode circuit of a fuel cell as described in claim 4, characterized in that: In step S2, the nozzles are opened in sequence from smallest to largest according to their orifice diameter.

6. The control method for a multi-stage injection rail anode circuit of a fuel cell as described in claim 4, characterized in that, The number of working modes of the multi-stage spray rail in step S3 is 2n-1.

7. The control method for a multi-stage injection rail anode circuit of a fuel cell as described in claim 6, characterized in that: When n is 2, the working modes of the multi-stage spray rail and the switching relationship between the working modes in step S3 are as follows: First-level working mode: Control nozzle X1 to work and shut down the other nozzles. When the duty cycle of nozzle X1 is greater than the threshold a1, it enters the second-level working mode. Second-level working mode: Control nozzle X2 to work and shut down the other nozzles. When the duty cycle of nozzle X2 is greater than the threshold a2, enter the third-level working mode; when the duty cycle of nozzle X2 is less than the threshold b2, return to the first-level working mode. Third-level working mode: Keep nozzle X1 open and control nozzle X2 to work; When the duty cycle of nozzle X2 is less than the threshold b3, it returns to the second-level working mode; Where nozzle Xn is the nth nozzle that opens sequentially.

8. The control method for a multi-stage injection rail anode circuit of a fuel cell as described in claim 6, characterized in that: When n is greater than 2, the various working modes of the multi-stage spray rail and the switching relationship between the various working modes in step S3 are as follows: S31, First-level working mode: Control nozzle X1 to work and close the other nozzles. When the duty cycle of nozzle X1 is greater than the threshold a1, enter the second-level working mode. S32, Second-level working mode: Control nozzle X2 to work and turn off the other nozzles. When the duty cycle of nozzle X2 is greater than the threshold a2, enter the third-level working mode; when the duty cycle of nozzle X2 is less than the threshold b2, return to the first-level working mode. S33, Third-level working mode: Keep nozzle X1 open and control nozzle X2 to work; when the duty cycle of nozzle X2 is greater than the threshold a3, enter the next level working mode; when the duty cycle of nozzle X2 is less than the threshold b3, return to the second-level working mode. S34. Let the loop value be m; where m is a natural number greater than 2, and the initial value of m is 3; S35, Level 2m-2 working mode: Keep nozzles X1 to Xm-2 normally open, control nozzle Xm to work, when the duty cycle of Xm is greater than the threshold a (2m-2), enter the next level working mode; when the duty cycle of nozzle Xm is less than the threshold b (2m-2), return to the previous level working mode; S36, Level 2m-1 working mode: Keep nozzles X1 to Xm-1 normally open, control nozzle Xm to work, when the duty cycle of nozzle Xm is greater than the threshold a (2m-1), enter S27; when the duty cycle of nozzle Xm is less than the threshold b (2m-1), return to the previous working mode. S37. Increment the value of m by 1, and repeat steps S34 and S35 as the new working mode until m equals n, at which point the loop ends. Where nozzle Xn is the nth nozzle that opens sequentially.

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