A fuel cell water temperature control system and its control method

Abstract

The present invention discloses a fuel cell water temperature control system and its control method, belonging to the field of fuel cells. The fuel cell water temperature control system provided by the present invention, the fuel cell includes a stack, the stack is provided with a coolant inlet and a coolant outlet, and the water temperature control system includes: a first control valve, a heat dissipation component, a heating component, a second control valve and a water circulation power device. The coolant inlet, the heat dissipation component, the water circulation power device and the coolant outlet are sequentially connected by pipelines to form a large circulation flow path, and the coolant inlet, the heating component, the water circulation power device and the coolant outlet are sequentially connected by pipelines to form a small circulation flow path. The large circulation flow path and the small circulation flow path are connected in parallel. The present invention replaces the original thermostat by connecting the first control valve in series in the large circulation flow path and the second control valve in series in the small circulation flow path. Through the independent first control valve and the second control valve, the control coupling degree of freedom is high and the control is flexible.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to a fuel cell water temperature control system and a control method thereof. Background Art

[0002] The temperature distribution of a fuel cell stack has an important impact on the safety and life of the fuel cell. To maintain the desired temperature inside the stack, it is necessary to dissipate the heat generated by the electrochemical reaction of the stack, and heat management of the system is required. Usually, circulating coolant is used to flow between the single cells of the stack to achieve the purpose of heat dissipation and cooling. The architecture of its thermal management subsystem is as Figure 1 shown. The water pump 7 drives the coolant circulation to dissipate the heat in the stack 1. The coolant circulation is divided into large and small circulation paths. The large circulation path 4 flows through the heat dissipation component 3, and the heat dissipation component 3 rotates to force air convection to enhance heat dissipation; the small circulation path 6 does not pass through the heat dissipation component 3, and the flow rates of its large and small circulation paths are automatically adjusted by the thermostat 12 according to the water temperature to adjust the distribution.

[0003] According to the requirements of the fuel cell operating temperature conditions, heat management needs to control the coolant inlet temperature T in , the temperature difference between the inlet and outlet of the stack ∆T c =(T out -T in ). Among them, controlling the coolant inlet temperature T in can ensure the normal operation of the stack 1, especially under low temperature conditions. At the same time, to achieve a uniform temperature distribution in the stack 1, the temperature difference ∆T c should be as small as possible. However, a smaller temperature difference ∆T c will result in a larger coolant flow rate, thereby increasing the parasitic power consumption and reducing the system efficiency. On the other hand, a larger temperature difference ∆T c will result in a lower temperature to which the coolant needs to be cooled, which will be limited by the ambient temperature and the performance of the heat dissipation component 3. The temperature difference ∆T c is a variable associated with the coolant flow rate.

[0004] When the temperature of the inlet coolant does not meet the target temperature T in , the controller 9 controls and adjusts the opening of the thermostat 12 according to the algorithm to adjust the flow rate distribution relationship between the large and small circulation paths. However, although adjusting the opening can change the distribution ratio of the large and small circulation paths, when the opening changes, the flow resistance characteristics of the two paths of the large and small circulation paths change, which may cause the total flow rate of the coolant in the two paths of the large and small circulation paths to increase or decrease instantaneously, thereby causing a large fluctuation in the system temperature difference and resulting in unstable temperature and temperature difference control problems.

[0005] Therefore, there is an urgent need to provide a fuel cell water temperature control system and a control method thereof to solve the technical problem of unstable temperature and temperature difference control in the prior art. Summary of the Invention

[0006] The object of the present invention is to provide a fuel cell water temperature control system and its control method, which can solve the problem of system temperature difference fluctuation caused by the change of the total coolant flow rate during the temperature adjustment of the thermostat, and improve the temperature and temperature difference control stability of the thermal management subsystem.

[0007] To achieve the above object, the following technical solutions are provided:

[0008] The present invention provides a fuel cell water temperature control system. The fuel cell includes an electric stack, and the electric stack is provided with a coolant inlet and a coolant outlet. The water temperature control system includes: a first control valve, a heat dissipation component, a heating component, a second control valve and a water circulation power device. The coolant inlet, the heat dissipation component, the water circulation power device and the coolant outlet are sequentially connected through pipelines to form a large circulation flow path. The coolant inlet, the heating component, the water circulation power device and the coolant outlet are sequentially connected through pipelines to form a small circulation flow path. The large circulation flow path and the small circulation flow path are connected in parallel.

[0009] Further, the water circulation power device is a water pump.

[0010] Further, the fuel cell water temperature control system further includes a controller, and both the first control valve and the second control valve are communicatively connected to the controller.

[0011] Further, the fuel cell water temperature control system further includes an inlet temperature sensor arranged on the coolant inlet pipeline and an outlet temperature sensor arranged on the coolant outlet pipeline. Both the inlet temperature sensor and the outlet temperature sensor are communicatively connected to the controller.

[0012] Further, both the heat dissipation component and the heating component are communicatively connected to the controller.

[0013] Further, the heat dissipation component includes a radiator and a cooling fan.

[0014] Further, the heating component is a resistor assembly.

[0015] Further, the water pump is communicatively connected to the controller.

[0016] The present invention also provides a control method for the fuel cell water temperature control system according to any one of the above technical solutions. The control method includes the following steps:

[0017] When the temperature entering the stack does not meet the target temperature, the opening degrees of the first control valve and the second control valve are adjusted through an algorithm to ensure that the total flow rate of the parallel flow paths of the large circulation flow path and the small circulation flow path remains unchanged;

[0018] According to the pump MAP characteristics, the total resistance dP of the parallel flow path of the large circulation flow path and the small circulation flow path, and the total flow rate of the parallel flow path, calculate the corresponding pump speed, and then reversely adjust the pump speed;

[0019] Adjust the coolant inlet temperature to the target temperature, and end.

[0020] Furthermore, the algorithm is as follows:

[0021]

[0022] Among them, K1 is the resistance characteristic coefficient of the heat dissipation component and the large circulation flow path, which is close to a fixed value and can be deduced; K2 is the resistance characteristic coefficient of the heating component and the small circulation flow path, which is close to a fixed value and can be deduced; K 11 is the resistance coefficient of the large circulation flow path control valve; K 12 is the resistance coefficient of the small circulation flow path control valve; Q1 is the target value of the large circulation flow path flow rate; Q2 is the target value of the small circulation flow path flow rate; Q is the target value of the total flow rate of the parallel flow path; dP is the total resistance of the parallel flow path.

[0023] Compared with the prior art, the fuel cell water temperature control system and its control method provided by the present invention replace the original thermostat by connecting a first control valve in series in the large circulation flow path and a second control valve in series in the small circulation flow path. With independent first and second control valves, the control freedom degree is high and the control is flexible. Specifically, the controller collects the inlet temperature and temperature difference data. When the inlet temperature does not meet the target temperature: adjust the opening degrees of the first control valve and the second control valve through the algorithm, so that the flow resistance characteristics K 11 and K 12 change. Since K 11 and K 12 are independent of each other, they can be freely adjusted. It can be seen from equation (4) in the algorithm that the flow rate distribution of the large circulation flow path and the small circulation flow path changes, realizing the adjustment of the coolant inlet temperature. It can be seen from equation (1) of the algorithm that the total resistance dP of the parallel flow path also changes. In order to ensure that the total flow rate of the parallel flow path remains unchanged before and after adjustment, according to the pump characteristic curve equation (i.e., the pump MAP characteristic) of equation (3), the adjusted dP, and the total flow rate of the parallel flow path, calculate the corresponding pump speed and output it to the pump. Through the joint control of the first control valve, the second control valve and the pump, the flow rate distribution of the large and small circulation flow paths changes, and at the same time, the total flow rate of the large and small circulation flow paths remains unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of a fuel cell water temperature control system in the prior art;

[0025] Figure 2 is a schematic structural diagram of a fuel cell water temperature control system according to an embodiment of the present invention.

[0026] 1 - Stack; 101 - Coolant inlet; 102 - Coolant outlet; 2 - Inlet temperature sensor; 3 - Heat dissipation component; 301 - Radiator; 302 - Cooling fan; 4 - Large circulation flow path; 5 - Heat generating component; 6 - Small circulation flow path; 7 - Water pump; 8 - Outlet temperature sensor; 9 - Controller; 10 - First control valve; 11 - Second control valve; 12 - Thermostat. Specific embodiments

[0027] To make the technical problems solved by the present invention, the technical solutions adopted, and the achieved technical effects clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0028] As Figure 2 shown, this embodiment provides a fuel cell water temperature control system. The fuel cell includes a stack 1, and the stack 1 is provided with a coolant inlet 101 and a coolant outlet 102. The water temperature control system includes: a first control valve 10, a heat dissipation component 3, a heat generating component 5, a second control valve 11, and a water circulation power device. The coolant inlet 101, the heat dissipation component 3, the water circulation power device, and the coolant outlet 102 are sequentially connected by pipelines to form a large circulation flow path 4. The coolant inlet 101, the heat generating component 5, the water circulation power device, and the coolant outlet 102 are sequentially connected by pipelines to form a small circulation flow path 6. The large circulation flow path 4 and the small circulation flow path 6 are connected in parallel.

[0029] Preferably, the water circulation power device is a water pump 7, the heat generating component 5 is a resistor assembly, i.e., a PCT assembly, and the heat dissipation component 3 includes a radiator 301 and a cooling fan 302.

[0030] Furthermore, the fuel cell water temperature control system further includes a controller 9, an inlet temperature sensor 2 provided on the pipeline of the coolant inlet 101, and an outlet temperature sensor 8 provided on the pipeline of the coolant outlet 102. The water pump 7, the first control valve 10, the second control valve 11, the inlet temperature sensor 2, the outlet temperature sensor 8, the heat dissipation component 3, and the heat generating component 5 are all communicatively connected to the controller 9.

[0031] This embodiment also provides a control method for the fuel cell water temperature control system. The control method includes the following steps:

[0032] When the temperature entering the stack does not meet the target temperature, adjust the opening degrees of the first control valve 10 and the second control valve 11 through an algorithm to ensure that the total flow rate of the parallel flow paths of the large circulation flow path 4 and the small circulation flow path 6 remains unchanged;

[0033] According to the water pump characteristic curve equation, i.e., the water pump MAP characteristic, the total resistance dP of the parallel flow path of the large circulation flow path 4 and the small circulation flow path 6, and the total flow rate of the parallel flow path, calculate the corresponding rotational speed of the water pump 7, and then reversely adjust the rotational speed of the water pump 7;

[0034] Adjust the coolant inlet temperature to the target temperature, and the process ends.

[0035] Specifically, the above algorithm is as follows:

[0036]

[0037] Among them,K1 is the resistance characteristic coefficient of the heat dissipation component 3 and the large circulation flow path 4. It is close to a fixed value and can be deduced;K2 is the resistance characteristic coefficient of the heat generating component 5 and the small circulation flow path 6. It is close to a fixed value and can be deduced;K 11 is the resistance coefficient of the first control valve 10;K 12 is the resistance coefficient of the second control valve 11;Q1 is the target value of the flow rate of the large circulation flow path 4;Q2 is the target value of the flow rate of the small circulation flow path 6;Q is the target value of the total flow rate of the parallel flow path;dP is the total resistance of the parallel flow path.

[0038] Specifically,the target inlet temperature for a certain working condition is set as T. The controller 9 collects the inlet temperature and temperature difference data. When the inlet temperature does not meet the target temperature: adjust the opening degrees of the first control valve 10 and the second control valve 11 through the algorithm, so that the flow resistance characteristics K 11 、K 12 change.K 11 and K 12 are independent of each other and can be freely adjusted. Obtain the opening degrees of the first control valve 10 and the second control valve 11 corresponding to the required Q1 / Q2 flow rate ratio from the relational expression (4), and determine the resistance characteristic coefficients K 11 、K 12 . Thus, according to the relational expression (1), calculate the corresponding dP at this time, and the total resistance dP of the parallel flow path also changes. In order to ensure that the total flow rate Q of the parallel flow path remains unchanged before and after adjustment, according to the relational expression (3), with Q and dP known, find the corresponding target water pump rotational speed and adjust the rotational speed. The water pump MAP characteristic refers to the ability of the water pump, that is, the relationship diagram of the water pump flow rate under different headings corresponding to different rotational speeds of the water pump 7, which is usually obtained through testing. Through the joint control of the first control valve 10, the second control valve 11 and the water pump 7, the flow rate distribution of the large and small circulation flow paths is changed, and at the same time, the total flow rate of the parallel flow paths of the large and small circulation flow paths remains unchanged, realizing the adjustment of the coolant inlet temperature.

[0039] The fuel cell water temperature control system and its control method provided in this embodiment replace the original thermostat 12 by connecting a first control valve 10 in series in the large circulation flow path 4 and a second control valve 11 in series in the small circulation flow path 6. With the independent first control valve 10 and second control valve 11, the control has a high degree of coupling freedom and is flexible. Specifically, the controller 9 collects the data of the temperature entering the stack and the temperature difference. When the temperature entering the stack does not meet the target temperature: the opening degrees of the first control valve 10 and the second control valve 11 are adjusted through an algorithm, so that the flow resistance characteristics K 11 , K 12 change. Since K 11 and K 12 are independent of each other, they can be freely adjusted. As can be seen from the algorithm, the flow rate of the large circulation flow path 4 and the flow rate of the small circulation flow path 6 are redistributed to achieve the adjustment of the temperature of the coolant entering the stack. As can be seen from the algorithm, the total resistance dP of the parallel flow path also changes. In order to ensure that the total flow rate of the parallel flow path remains unchanged before and after the adjustment, according to the pump characteristic curve equation (i.e., the pump MAP characteristic) in the algorithm, the adjusted dP, and the total flow rate of the parallel flow path, the corresponding pump 7 speed is calculated and output to the pump 7. Through the joint control of the first control valve 10, the second control valve 11 and the pump 7, the flow rate distribution of the large and small circulation flow paths is changed, and at the same time, the total flow rate of the large and small circulation flow paths remains unchanged.

[0040] Note that the above is only the preferred embodiment of the present invention and the applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here, and various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A control method for a fuel cell water temperature control system, the fuel cell including a stack (1), the stack (1) being provided with a coolant inlet (101) and a coolant outlet (102), characterized in that, The water temperature control system includes: a first control valve (10), a heat dissipation component (3), a heating component (5), a second control valve (11), and a water circulation power device. The coolant inlet (101), the heat dissipation component (3), the water circulation power device, and the coolant outlet (102) are sequentially connected by pipelines to form a large circulation flow path (4). The coolant inlet (101), the heating component (5), the water circulation power device, and the coolant outlet (102) are sequentially connected by pipelines to form a small circulation flow path (6). The large circulation flow path (4) and the small circulation flow path (6) are in parallel connection; The water circulation power device is a water pump (7); It is characterized in that the control method includes the following steps: When the temperature entering the reactor does not meet the target temperature, the opening degrees of the first control valve (10) and the second control valve (11) are adjusted through an algorithm to ensure that the total flow rate of the parallel flow paths of the large circulation flow path (4) and the small circulation flow path (6) remains unchanged; According to the water pump MAP characteristics, the total resistance dP of the parallel flow paths of the large circulation flow path (4) and the small circulation flow path (6), and the total flow rate of the parallel flow paths, calculate the corresponding rotational speed of the water pump (7), and then reversely adjust the rotational speed of the water pump (7); Adjust the temperature of the coolant entering the reactor to the target temperature, and end; The algorithm is as follows: dP = K 11 Q1 2 + K1Q1 2 = K 12 Q2 2 + K2Q2 2 --(1) Q = Q1 + Q2--(2) Water pump MAP = f(Q, dP)--(3) Among them, K1 is the resistance characteristic coefficient of the heat dissipation component (3) and the large circulation flow path (4), which is close to a fixed value and can be deduced; K2 is the resistance characteristic coefficient of the heat generating component (5) and the small circulation flow path (6), which is close to a fixed value and can be deduced; K 11 is the resistance coefficient of the first control valve (10); K 12 is the resistance coefficient of the second control valve (11); Q1 is the target value of the flow rate of the large circulation flow path (4); Q2 is the target value of the flow rate of the small circulation flow path (6); Q is the target value of the total flow rate of the parallel flow path; dP is the total resistance of the parallel flow path.

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