A method for fast prediction of fuel cell stack flow distribution

Abstract

The application discloses a method for quickly predicting fuel cell stack flow distribution, comprising the following steps: S1, establishing a three-dimensional stack fluid geometry model, determining the resistance relationship of each part of the fluid flowing through different branches, and obtaining the resistance coefficient of each part; S2, building a flow network model of the stack, regarding each part of the monomer structure of each branch as a node by analyzing the relationship among mass flow, flow resistance and resistance drop, and establishing the flow network model of the stack based on the continuity equation and the energy conservation equation; S3, according to the flow network model of the stack, an analytical model for calculating the flow distribution in the stack is established, iterative solving is carried out, and the iterative variables, such as the resistance drop of the inlet and outlet common channels, the resistance drop of each section of the single cell and the flow parameters of each section of the single cell, are updated until convergence, and the calculation result of the flow distribution of the stack is output. The method has universality in engineering application, and can effectively serve as a reference for the design of the fuel cell stack.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a method for rapidly predicting the flow distribution of a fuel cell stack. Background Technology

[0002] In recent years, fuel cells, as a clean energy technology, have attracted widespread attention due to their advantages such as high efficiency, high power density, fast cold start, zero emissions, and low operating temperature, and are poised to play a crucial role in future global energy utilization. Individual fuel cells typically have low voltages, ranging from 0.6 to 0.7V. To meet the demands of high power output, many individual cells are often connected in series to form a fuel cell stack. Since the flow rate of reactants is highly sensitive to fuel cell performance, ensuring flow uniformity among the individual cells in the fuel cell stack is essential. Therefore, establishing a corresponding flow distribution model during the design and development cycle of the fuel cell stack is particularly important, as it can save significant human and material resources and improve development efficiency.

[0003] In existing technologies, the flow distribution calculation method for fuel cell stacks typically employs CFD (Computational Fluid Dynamics) to construct a three-dimensional model of the fuel cell stack and then calculate and analyze the flow and pressure distribution. However, large fuel cell stacks contain a large number of cells, and each calculation for stacks with different numbers of cells requires large-scale meshing and consumes a significant amount of computation time, resulting in a longer design cycle. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention discloses a method for rapidly predicting the flow distribution of a fuel cell stack, specifically including the following steps:

[0005] S1: Establish a three-dimensional fluid geometry model of the fuel cell stack, determine the resistance relationship of each part as the fluid flows through different branches, and obtain the resistance coefficient of each part;

[0006] S2: Construct a flow network model for the fuel cell stack. By analyzing the relationship between mass flow rate, flow resistance, and resistance drop, each individual component of each branch is regarded as a node. Based on the continuity equation and the energy conservation equation, a flow network model for the fuel cell stack is established.

[0007] S3: Based on the fuel cell stack flow network model, establish an analytical model for calculating the flow distribution within the stack, perform iterative solutions, update the iterative variables such as the resistance drop of the common inlet and outlet channels, the resistance drop of each individual cell, and the flow parameters of each individual cell until convergence, and output the calculation results of the fuel cell stack flow distribution.

[0008] S1 adopts the following method:

[0009] S11: Establish the relationship between mass flow rate Q and the resistance drop ΔP of a single battery cell.

[0010] △P=aQ2 +bQ (1)

[0011] Establish a three-dimensional geometric model of a single cell battery, and fit a quadratic relation with an intercept of 0 through fluid calculations of three or more single cells batteries to determine the resistance relationship of a single cell battery and obtain the resistance coefficients a and b of the single cell battery in the above formula (1).

[0012] S12: Establish the relationship between mass flow rate Q and the resistance drop ΔP of the common channel of a single battery cell.

[0013] △P=cQ 2 +dQ (2)

[0014] Establish a three-dimensional geometric model of the common channel of a single battery cell. Through fluid calculations of three or more common channels of a single battery cell, fit a quadratic relation with an intercept of 0 to determine the resistance relationship of the common channel of a single battery cell and obtain the resistance coefficients c and d of the common channel of a single battery cell in the above formula (2).

[0015] S13: Establish the relationship between mass flow rate Q and the shunt corner resistance drop ΔP of a single battery cell.

[0016] △P=eQ 2 +fQ (3)

[0017] Establish a three-dimensional geometric model of the shunt corner of a single cell battery. Through fluid calculations of the shunt corners of three or more single cells, fit a quadratic relation with an intercept of 0 to determine the resistance relationship of the shunt corner of a single cell battery and obtain the resistance coefficients e and f of the shunt corner of a single cell battery in the above formula (3).

[0018] S14: Establish the relationship between mass flow rate Q and the corner resistance drop ΔP of a single battery cell.

[0019] △P=gQ 2 +hQ (4)

[0020] By calculating the fluid flow at the junction of three or more single-cell batteries using the S13 process geometric model, a quadratic relation with an intercept of 0 is fitted to determine the resistance relationship at the junction of the single-cell batteries and obtain the resistance coefficients g and h of the junction of the single-cell batteries in the above formula (4).

[0021] The fluid components in each branch of the fuel cell stack flow network model satisfy the following conditions based on the continuity equation and the energy conservation equation:

[0022] The fluid flowing into any node is equal to the fluid flowing out of the node; each fluid segment has a corresponding resistance drop, which is a function of the mass flow rate through that segment; the algebraic sum of the resistance drops around any closed loop must be 0;

[0023] Based on the above conditions, the following relationship is obtained:

[0024] The fluid in each cell of the fuel cell stack satisfies the following relationship:

[0025] △P n =a(q n ) 2 +b(q n (5);

[0026] Q n-1 =∑(q n-1 (6);

[0027] The fluid in the common inlet channel of the fuel cell stack satisfies the following relationship:

[0028] △P in(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+e(q n-1 ) 2 +f(q n-1 (7);

[0029] The fluid in the common channel at the fuel cell stack outlet satisfies the following relationship:

[0030] △P out(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+g(q n-1 ) 2 +h(q n-1 (8);

[0031] The following relationship applies to any closed-loop fluid in the fuel cell stack:

[0032] △P n =△P in(n-1) +△P n-1 +△P out(n-1) (9)

[0033] When establishing an analytical model of the flow distribution within the stack for calculations of fuel cell stack fluid distribution:

[0034] S31: The total inlet flow rate Q of the fuel cell stack n The flow rate is evenly distributed to each individual pool, at which point the flow rate of each individual pool is q. n =Q n / n; then calculate the resistance drop ΔP1 of the first single pool at this time according to formula (1);

[0035] S32: Calculate the resistance drop of the common access channel at each location at this time.

[0036] △P in(n-1) =c(Qn-1 ) 2 +d(Q n-1 )+e(q n-1 ) 2 +f(q n-1 (10);

[0037] △P out(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+g(q n-1 ) 2 +h(q n-1 (11);

[0038] S33: Calculate the single-cell resistance drop of other sections of the fuel cell stack at this time:

[0039] △P n =△P in(n-1) +△P n-1 +△P out(n-1) (12);

[0040] Then, based on the relationship in equation (1), update the flow rate q of each single pool. n ';

[0041] S33: Introduce the error factor ERR = ∑((q n '-q n ) / q n ) 2 The above process S32-S33 is iteratively solved, and the iterative variables, such as the resistance drop of the common channel between the inlet and outlet, the resistance drop of each single pool, and the flow rate of each single pool, are updated. If the error requirements are met, the calculation is stopped, and the calculation results of the stack flow distribution are output.

[0042] By employing the above-mentioned technical solution, this invention provides a method for rapidly predicting the flow distribution of a fuel cell stack. This method first establishes a corresponding three-dimensional fluid geometry model of the stack, performing CFD calculations on the common channel of a single cell, the entire plate of a single cell, and the corner of the common channel of a single cell, determining the resistance relationships of each part, and obtaining the resistance coefficients of each part. Then, by analyzing the relationship between mass flow rate, flow resistance, and pressure difference, a flow network model of the stack is constructed for iterative solution. This method can predict the flow distribution and pressure distribution between individual cells in fuel cell stacks with different numbers of cells in the early design stage, providing guidance for the design and analysis of the stack. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating the calculation process of the fuel cell stack flow distribution method of the present invention.

[0045] Figure 2 This is a schematic diagram of the fuel cell stack model in this invention;

[0046] Figure 3 This is a schematic diagram of the fuel cell stack flow network model in this invention;

[0047] Figure 4 This is the result of the flow distribution uniformity calculation for the 200 fuel cell stacks in this invention;

[0048] Figure 5 This is the result of the flow distribution uniformity calculation for the 300 fuel cell stacks in this invention;

[0049] Figure 6 This is the result of the flow distribution uniformity calculation for the 370 fuel cell stacks in this invention. Detailed Implementation

[0050] To make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention:

[0051] like Figure 1 The method for rapidly predicting the flow distribution of a fuel cell stack, as shown, specifically includes the following steps:

[0052] A realistic fluid geometry model of the fuel cell stack was established to determine the resistance relationships of each component and obtain the resistance coefficients for each component. The fluid geometry of a U-shaped fuel cell stack is shown in [reference needed]. Figure 2 The fuel cell stack consists of three parts: 1. an inlet common channel, 2. individual cells in each section of the stack, and 3. an outlet common channel. Gas and coolant flow in through the inlet common channel, gradually branching out to the individual cells in each section. The fluids in each cell converge at the outlet common channel and finally flow out of the stack. Therefore, the fluid flow resistance of the fuel cell stack mainly consists of three parts: frictional losses along the flow direction in the inlet and outlet common channels, local resistance losses at corners due to branching and confluence, and individual cell resistance losses due to the complex structure of each cell.

[0053] Establish the relationship between mass flow rate Q and the resistance drop ΔP of a single battery cell.

[0054] △P=aQ 2 +bQ (1)

[0055] Re-establish Figure 2 The geometric model of a single cell battery in the real 2-cell battery is used to fit a quadratic relation with an intercept of 0 through three or more sets of single cell battery fluid calculations to determine the resistance relationship of the single cell battery and obtain the resistance coefficients a and b of the single cell battery in the above formula (1).

[0056] Establish the relationship between mass flow rate Q and the resistance drop ΔP of the common channel for a single battery cell.

[0057] △P=cQ 2 +dQ (2)

[0058] Re-establish Figure 2 The geometric model of the common channel of a single battery in the real 4-cell battery is used to fit a quadratic relation with an intercept of 0 by three or more sets of fluid calculations of the common channel of a single battery to determine the resistance relationship of the common channel of a single battery and obtain the resistance coefficients c and d of the common channel of a single battery in the above formula (2).

[0059] Establish the relationship between mass flow rate Q and the shunt corner resistance drop ΔP of a single battery cell.

[0060] △P=eQ 2 +fQ (3)

[0061] Re-establish Figure 2 The geometric model of the shunt corner of a single battery in China is used to calculate the process fluid of three or more single battery shunt corners ① and fit a quadratic relation with an intercept of 0 to determine the resistance relationship of the single battery shunt corner and obtain the resistance coefficients e and f of the single battery shunt corner in the above formula (3).

[0062] Establish the relationship between mass flow rate Q and the corner resistance drop ΔP of a single battery cell.

[0063] △P=gQ 2 +hQ (4)

[0064] Then, through the above C process geometric model, three or more sets of single-cell battery busbar corners ② process fluid calculations are performed to fit a univariate quadratic relation with an intercept of 0, so as to determine the resistance relationship of the single-cell battery busbar corner and obtain the resistance coefficients g and h of the single-cell battery busbar corner in the above formula (4).

[0065] By analogy with power grids, we can build a flow network model for fuel cells.

[0066] By analyzing the relationship between mass flow rate, flow resistance, and resistance drop, a flow network model for a U-shaped fuel cell stack is established. Figure 3 The fluid in any network satisfies the following relationship according to the continuity equation and the energy conservation equation:

[0067] The fluid flowing into any node is equal to the fluid flowing out of the node;

[0068] Each fluid segment has a corresponding resistance drop, which is a function of the mass flow rate through that segment;

[0069] The algebraic sum of the resistance drops around any closed loop must be 0.

[0070] Therefore, the following relationship can be obtained for each cell in the fuel cell stack:

[0071] △P n =a(q n ) 2 +b(q n (5);

[0072] Q n-1 =∑(q n-1 (6);

[0073] For the shared access channel for fuel cell stack inlets:

[0074] △P in(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+e(q n-1 ) 2 +f(q n-1 (7);

[0075] For the fuel cell stack outlet common channel:

[0076] △P out(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+g(q n-1 ) 2 +h(q n-1 (8);

[0077] For any closed loop: ΔP n =△P in(n-1) +△P n-1 +△P out(n-1) (9)

[0078] Based on the fuel cell stack flow network model, the fuel cell stack fluid distribution calculation is performed.

[0079] First, adjust the fuel cell stack air intake Q. nThe gas volume is equally allocated to each individual tank section, at which point the gas volume of each individual tank section is q. n =Q n / n; then calculate the resistance drop ΔP1 of the first single pool at this time according to formula (1);

[0080] Calculate the resistance drop of the common access channel at this time:

[0081] △P in(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+e(q n-1 ) 2 +f(q n-1 (10);

[0082] △P out(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+g(q n-1 ) 2 +h(q n-1 (11);

[0083] At this time, the gas volume per cell in each section of the fuel cell stack is:

[0084] △P n =P in(n-1) +△P n-1 +△P out(n-1) (12);

[0085] Then, based on the relationship in equation (1), update the gas volume q of each single pool section. n ';

[0086] Perform error analysis: Introduce the error factor ERR = ∑((q) n '-q n ) / q n ) 2 If the error requirement is met, the calculation stops and the flow rate of each section of the fuel cell stack is output; otherwise, the iterative calculation continues according to steps B to E until the calculation error is met, at which point the calculation stops.

[0087] The calculation results of this patented method and the CFD method for different number of cells in the stack are shown below. Figures 4-6 The accuracy of the method in this patent is verified to be high.

[0088] This invention discloses a method for rapidly predicting the flow distribution of a fuel cell stack. This method is universal in engineering applications and can serve as an effective reference for the design of fuel cell stacks.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for rapidly predicting flow distribution in a fuel cell stack, characterized in that... include: S1: Establish a three-dimensional fluid geometry model of the fuel cell stack, determine the resistance relationship of each part as the fluid flows through different branches, and obtain the resistance coefficient of each part; S2: Construct a flow network model for the fuel cell stack. By analyzing the relationship between mass flow rate, flow resistance, and resistance drop, each individual component of each branch is regarded as a node. Based on the continuity equation and the energy conservation equation, a flow network model for the fuel cell stack is established. S3: Based on the fuel cell stack flow network model, establish an analytical model for calculating the flow distribution within the stack, and perform iterative solutions, updating the iterative variables such as the resistance drop of the common inlet and outlet channels, the resistance drop of each section's single pool, and the flow parameters of each section's single pool until convergence, and output the calculation results of the fuel cell stack flow distribution. S1 adopts the following method: S11: Establish the relationship between mass flow rate Q and the resistance drop ΔP of a single battery cell. △P=aQ 2 +bQ(1) Establish a three-dimensional geometric model of a single cell battery, and fit a quadratic relation with an intercept of 0 through fluid calculations of three or more single cells batteries to determine the resistance relationship of a single cell battery and obtain the resistance coefficients a and b of the single cell battery in the above formula (1). S12: Establish the relationship between mass flow rate Q and the resistance drop ΔP of the common channel of a single battery cell. △P=cQ 2 +dQ(2) Establish a three-dimensional geometric model of the common channel of a single battery cell. Through fluid calculations of three or more common channels of a single battery cell, fit a quadratic relation with an intercept of 0 to determine the resistance relationship of the common channel of a single battery cell and obtain the resistance coefficients c and d of the common channel of a single battery cell in the above formula (2). S13: Establish the relationship between mass flow rate Q and the shunt corner resistance drop ΔP of a single battery cell. △P=eQ 2 +fQ(3) Establish a three-dimensional geometric model of the shunt corner of a single cell battery. Through fluid calculations of the shunt corners of three or more single cells, fit a quadratic relation with an intercept of 0 to determine the resistance relationship of the shunt corner of a single cell battery and obtain the resistance coefficients e and f of the shunt corner of a single cell battery in the above formula (3). S14: Establish the relationship between mass flow rate Q and the corner resistance drop ΔP of a single battery cell. △P=gQ 2 +hQ(4) By calculating the fluid flow at the junction of three or more single-cell batteries using the S13 process geometric model, a quadratic relation with an intercept of 0 is fitted to determine the resistance relationship at the junction of the single-cell batteries and obtain the resistance coefficients g and h of the junction of the single-cell batteries in the above formula (4).

2. The method for rapidly predicting fuel cell stack flow distribution according to claim 1, characterized in that... The fluid components in each branch of the fuel cell stack flow network model satisfy the following conditions based on the continuity equation and the energy conservation equation: The fluid flowing into any node is equal to the fluid flowing out of the node; each fluid segment has a corresponding resistance drop, which is a function of the mass flow rate through that segment; the algebraic sum of the resistance drops around any closed loop must be 0; Based on the above conditions, the following relationship is obtained: The fluid in each cell of the fuel cell stack satisfies the following relationship: △P n =a(q n ) 2 +b(q n )(5); Q n-1 =∑(q n-1 ) (6); The fluid in the common inlet channel of the fuel cell stack satisfies the following relationship: △P in(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+e(q n-1 ) 2 +f(q n-1 )(7); The fluid in the common channel at the fuel cell stack outlet satisfies the following relationship: △P out(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+g(q n-1 ) 2 +h(q n-1 )(8); The following relationship applies to any closed-loop fluid in the fuel cell stack: △P n =△P in(n-1) +△P n-1 +△P out(n-1) (9) 。 3. The method for rapidly predicting fuel cell stack flow distribution according to claim 2, characterized in that... When establishing an analytical model of the flow distribution within the stack for calculations of fuel cell stack fluid distribution: S31: The total inlet flow rate Q of the fuel cell stack n The flow rate is evenly distributed to each individual pool, at which point the flow rate of each individual pool is q. n =Q n / n; then calculate the resistance drop ΔP1 of the first single pool according to formula (1); S32: Calculate the resistance drop of the common access channel at each location at this time. △P in(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+e(q n-1 ) 2 +f(q n-1 )(10); △P out(n-1) =c(Q n-1 ) 2 +d(Q n-1 )+g(q n-1 ) 2 +h(q n-1 )(11); S33: Calculate the single-cell resistance drop of other sections of the fuel cell stack at this time: △P n =△P in(n-1) +△P n-1 +△P out(n-1) (12); Then, based on the relationship in equation (1), update the flow rate q of each single pool. n ’ ; S33: Introduce the error factor ERR=∑((q n ’ -q n ) / q n ) 2 The above process S32-S33 is iteratively solved, and the iterative variables, such as the resistance drop of the common channel between the inlet and outlet, the resistance drop of each single cell, and the flow rate of each single cell, are updated. If the error requirements are met, the calculation is stopped, and the calculation results of the stack flow distribution are output.

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