Method for determining equivalent pressure in activation process of liquid storage type reserve battery

Abstract

The invention discloses a method for determining equivalent pressure in an activation process of a liquid storage type reserve battery, which comprises the following steps of: modeling a rotational symmetric flow field: setting a geometric center of the liquid storage type reserve battery in the activation process as an original point of a cylindrical coordinate system, and setting a rotational symmetric axis of the liquid storage type reserve battery as an axial direction of the cylindrical coordinate system, the radial direction of the cylindrical coordinate system coincides with the geometric radial direction of the porous electrode to obtain a rotational symmetric flow field of the electrolyte rotating along with the battery; obtaining equivalent density: calculating to obtain the electrolyte equivalent density according to the electrolyte density, the air density and the real-time electrolyte integral number; equivalent speed acquisition: according to the speed of the electrolyte under the Cartesian coordinate system, calculating to obtain the equivalent speed of the electrolyte under the cylindrical coordinate system, including the radial speed and the circumferential speed; and equivalent pressure intensity determination: according to the equivalent density and the equivalent speed, calculating to obtain the required equivalent pressure intensity by adopting a centrifugation-kinetic energy composite pressure intensity integral model. The equivalent pressure intensity determination method is high in efficiency and good in precision.

Description

Technical Field

[0001] The invention relates to the technical field of numerical simulation of liquid storage type reserve batteries, and in particular to a method for determining the equivalent pressure during an activation process of a liquid storage type reserve battery. Background Art

[0002] Liquid-storage backup batteries are a unique class of primary batteries with irreplaceable application value. Their exceptionally long shelf life (>10 years) makes them the only power source of choice for electromechanical systems in military equipment, aerospace engineering, and other fields requiring extremely high lifespan and reliability. The key to achieving this long shelf life lies in their design architecture, which isolates the electrode active material from the electrolyte. This prevents electrochemical reactions between the active material and the electrolyte during long-term storage, resulting in a theoretically near-infinite lifespan. Liquid-storage backup batteries utilize a conventional liquid electrolyte encapsulated in an electrolyte bottle isolated from the electrodes. When overloads during launch or flight (such as launch acceleration and impact loads) exceed a preset threshold, a mechanical structure ruptures the electrolyte bottle, allowing the electrolyte to reach the electrode interface and soak the electrodes, triggering battery activation and discharge. This complex multi-physics-responsive battery activation process can be divided into three sequential, cascaded, and coupled sub-processes: liquid infusion, soaking, and activation.

[0003] Electromechanical systems in military and aerospace equipment require timely activation to obtain system and environmental status information as quickly as possible. Delayed battery activation can lead to the loss of critical data, compromising high-precision, high-transient operations such as orbital adjustments and rendezvous and docking. Studying the activation process of liquid-reservoir-type backup batteries through mathematical modeling and digital simulation has significant application value in addressing the issue of rapid activation.

[0004] However, the activation process of liquid storage battery is highly transient and coupled, and existing research has significant limitations in modeling the activation process of liquid storage battery. First, the electrolyte in the activation process of liquid storage battery involves highly dynamic transient material transport processes such as flowing in and infiltrating porous electrodes; second, the activation time scale of liquid storage battery is relatively low, the coupling of multiple physical fields is stronger, and the dynamic modeling and simulation calculations are extremely difficult. Among them, in the transient process of activation caused by the rupture of the electrolyte bottle, the equivalent pressure formed by the electrolyte inflow sub-process is the core initial condition that determines the wetting state of the porous electrode. How to efficiently and accurately determine the equivalent pressure formed by the inflow sub-process is crucial.

[0005] Existing studies typically assume that a uniform and stable pressure field forms immediately after the electrolyte bottle breaks, using fixed values as static boundary conditions. This ignores the non-equilibrium pressure distribution characteristics caused by the combined effects of mechanical impact, fluid inertia, and rotating centrifugal force at the moment of bottle rupture. As a result, the time-varying characteristics of the infiltration pressure are simplified to a constant value, which fails to reflect the real-time regulation mechanism of the infiltration rate by the dynamic evolution of the electrolyte distribution field, severely restricting the physical authenticity of the solution. Secondly, traditional models ignore the physical property changes of the gas-liquid two-phase mixed fluid, fail to correct the equivalent density parameter by volume fraction, and simplify the mixed medium of electrolyte and air into a single liquid phase flow, resulting in a significant deviation between the calculated density value and the actual working conditions, further amplifying the prediction error of the infiltration liquid surface front. More critically, existing methods, lacking a data transfer mechanism across physical fields, separate the inflow and wetting subprocesses into independent models. This makes it impossible to establish a dynamic boundary condition connection between the two subprocesses, and the simultaneous solution of multiple field coupling issues such as fragmentation, flow, and infiltration faces enormous computational complexity. Ultimately, this results in only static analysis of a single process, making it difficult to capture the temporal cascade effects of the entire activation process. Furthermore, the high computational resource consumption makes the existing model impractical in both accuracy and efficiency, becoming a core bottleneck restricting the optimization of activation performance for liquid storage backup batteries.

[0006] In summary, the problems existing in the prior art are: the determination of the equivalent pressure during the activation process of the liquid storage type reserve battery is inefficient and has poor accuracy. Summary of the Invention

[0007] The object of the present invention is to provide a method for determining the equivalent pressure during the activation process of a liquid storage type reserve battery, which has high efficiency and good precision.

[0008] The technical solution for achieving the purpose of the present invention is:

[0009] A method for determining the equivalent pressure during the activation process of a liquid storage type reserve battery comprises the following steps:

[0010] Rotationally symmetric flow field modeling: The geometric center of the liquid storage battery during activation is set as the origin of the cylindrical coordinate system, and the rotational symmetry axis of the liquid storage battery is set as the axial direction of the cylindrical coordinate system. The radial direction of the cylindrical coordinate system coincides with the geometric radial direction of the porous electrode of the liquid storage battery, thereby obtaining a rotationally symmetric flow field of the liquid storage battery electrolyte as the battery rotates;

[0011] Equivalent density acquisition: The electrolyte equivalent density is calculated based on the electrolyte density, air density and real-time electrolyte liquid volume fraction;

[0012] Equivalent velocity acquisition: Based on the velocity of the electrolyte in the Cartesian coordinate system, its equivalent velocity in the cylindrical coordinate system is calculated, including radial velocity and circumferential velocity;

[0013] Determination of equivalent pressure: Based on the equivalent density and equivalent velocity, a centrifugal-kinetic energy composite pressure integral model is used to calculate the required equivalent pressure.

[0014] Compared with the prior art, the present invention has the following significant advantages:

[0015] 1. Good accuracy: The present invention solves the equivalent pressure in the rotating flow field in real time and uses it as a time-varying boundary condition. It also incorporates the equivalent density correction into the pressure calculation, thereby accurately characterizing the dynamic coupling relationship between electrolyte movement and electrode penetration. The calculation accuracy is higher, effectively avoiding the problem of excessive errors caused by traditional calculation methods.

[0016] 2. High Efficiency: To address the computational complexity of multi-field coupled problems such as electrolyte bottle breakage, flow transport, and porous media seepage, this invention implements dynamic parameter transfer between the inflow and infiltration sub-processes through a modular interface. This allows each sub-process to be solved independently, avoiding the enormous computational complexity of simultaneously solving multi-field coupled problems such as breakage, flow, and seepage. While ensuring accuracy, this invention improves overall computational efficiency, providing technical support for rapid engineering-level multi-condition assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the main flow chart of the method for determining the equivalent pressure during the activation process of the liquid storage type reserve battery of the present invention.

[0018] Figure 2 is an example graph of the electrolyte volume fraction changing over time.

[0019] Figure 3 is an example graph of the radial equivalent velocity changing with time.

[0020] Figure 4 is an example graph of equivalent pressure changing with time. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the method for determining the equivalent pressure during the activation process of the liquid storage type reserve battery of the present invention comprises the following steps:

[0023] S10, rotationally symmetric flow field modeling: the geometric center of the liquid storage battery during the activation process is set as the origin O of the cylindrical coordinate system, the rotational symmetry axis of the liquid storage battery is set as the axial direction of the cylindrical coordinate system, i.e., the Z axis, the radial direction of the cylindrical coordinate system, i.e., the r direction, coincides with the geometric radial direction of the porous electrode of the liquid storage battery, and the circumferential rotation angle θ of the porous electrode is obtained to obtain the rotationally symmetric flow field of the electrolyte of the liquid storage battery as the battery rotates;

[0024] Specifically, in the ammunition launch / flight environment, the rotational symmetry axis of the battery system is set to the Z axis, and the origin O is located at the geometric center of the battery (i.e., the intersection of the rotation axis and the cross section of the battery). The radial direction r extends from the origin O in a direction perpendicular to the Z axis, pointing to the radial position of the porous electrode (the electrodes are distributed in a ring around the Z axis, r = 0 corresponds to the axis, r = 0 corresponds to the axis, and r = 0 corresponds to the axis). max The circumferential θ represents the rotation angle around the Z axis, which characterizes the tangential motion of the electrolyte as the battery rotates.

[0025] This step adjusts the Cartesian coordinate system to a cylindrical coordinate system. This is because when the battery rotates at high speed, the electrolyte migration is dominated by centrifugal force, and the direction of centrifugal acceleration is always radially outward (r direction). The radial component r of the cylindrical coordinate system directly corresponds to the direction of centrifugal force, while the circumferential θ component naturally describes the rotational tangential motion, strictly matching the laws of physics. At the same time, this step ensures that subsequent steps (such as speed conversion and pressure integration) are based on the same coordinate system, avoiding parameter conversion errors between different reference frames and ensuring the accuracy of the entire calculation process.

[0026] S20, equivalent density acquisition: the electrolyte equivalent density is calculated based on the electrolyte density, the air density and the real-time electrolyte liquid volume fraction.

[0027] The equivalent density of the electrolyte is calculated as follows:

[0028] ρ eff =EVF·ρ1+(1-EVF)·ρ air (1);

[0029] Among them, ρ eff is the equivalent density of the electrolyte, ρ1 is the density of the electrolyte, ρ air is the air density, EVF is the electrolyte volume fraction, and the electrolyte density is obtained by testing actual samples.

[0030] The electrolyte liquid volume fraction is extracted in real time based on the two-phase flow distribution after the electrolyte bottle is broken, and its value ranges from 0 to 1. The physical meaning of the electrolyte liquid volume fraction is the distribution field data of the electrolyte and air mixture output through the liquid inlet sub-process, representing the liquid phase proportion of the gas-liquid two-phase mixture at the current moment.

[0031] The schematic diagram of the electrolytic liquid volume fraction is as follows Figure 2 shown. Figure 2 The figure shows how the volume fraction of a portion of the electrolyte changes over time. As can be seen from the figure, it is highly transient and closely related to the movement of the electrolyte, which cannot be described by simple laws. If only the unidirectional flow assumption is used, subsequent calculation errors will increase significantly.

[0032] This step is used to determine the equivalent density, eliminate the density calculation deviation caused by the gas phase medium, and ensure the accuracy of subsequent calculations.

[0033] S30, equivalent velocity acquisition: according to the velocity of the electrolyte in the Cartesian coordinate system, the equivalent velocity in the cylindrical coordinate system is calculated, including radial velocity and circumferential velocity.

[0034] The step of obtaining the equivalent speed in step S30 is specifically as follows:

[0035] The radial velocity of the electrolyte in the cylindrical coordinate system is calculated as follows:

[0036]

[0037] The circumferential velocity of the electrolyte in the cylindrical coordinate system is calculated as follows:

[0038]

[0039] In the above two equations, x and y represent the position coordinates of the electrolyte in the Cartesian coordinate system, V x and V y Represents the velocity components of the electrolyte in different directions in the Cartesian coordinate system, V y V r is the radial velocity of the electrolyte in the cylindrical coordinate system, V θ is the circumferential velocity of the electrolyte in the cylindrical coordinate system.

[0040] Radial velocity V r Characterizes the migration rate of the electrolyte from the rotation center (origin O) to the porous electrode (radial r direction). It is the circumferential velocity V θ , characterizes the tangential velocity of the electrolyte around the Z axis and is directly related to the magnitude of the centrifugal force.

[0041] The electrolyte distribution field data is obtained through the liquid inlet process, and the velocity component V of the electrolyte in the Cartesian coordinate system is extracted in real time. x and V y , and reconstruct its velocity field based on equations (2) and (3).

[0042] The schematic diagram of the reconstructed radial velocity changing with time is shown in Figure 3 As shown in the figure, in the initial stage (0.8-5ms), the electrolyte is accelerated by centrifugal force. At this time, fluid resistance is not yet significant, and the net acceleration remains positive. When the centrifugal force and resistance are in dynamic equilibrium, the velocity reaches its peak. In the subsequent stage, the resistance increases nonlinearly due to the dissipation of kinetic energy caused by the viscosity of the electrolyte and the increase in radial displacement.

[0043] This step is used to determine the equivalent velocity, which can establish a direct relationship between the rotational flow field parameters and the permeation dynamics of porous media.

[0044] S40, determining equivalent pressure: Based on the equivalent density and equivalent speed, a centrifugal-kinetic energy composite pressure integral model is used to calculate the required equivalent pressure.

[0045] The step of determining the equivalent pressure in step S40 is specifically as follows:

[0046] Calculate the required equivalent pressure according to the following formula:

[0047]

[0048] Among them, P wetting is the equivalent pressure, is the centrifugal force gradient term, quantifying the static pressure accumulation effect of the rotation drive, is the inertial kinetic energy term, V3 is the axial velocity, which is the same as the component of the electrolyte in the z direction in the Cartesian coordinate system.

[0049] P wetting The equivalent pressure represents the time-varying infiltration pressure calculated by integrating along the preset path; the centrifugal force gradient term quantifies the static pressure accumulation effect driven by rotation; and the inertial kinetic energy term characterizes the accelerating effect of fluid migration on electrode penetration.

[0050] This step is used to determine the equivalent pressure. The formula for calculating the equivalent pressure is the centrifugal-kinetic energy composite pressure integral model. This allows for accurate characterization of the dynamic coupling relationship between electrolyte movement and electrode penetration, avoiding the large errors caused by traditional calculation methods.

[0051] The example of equivalent pressure changing with time obtained by this method is shown in the figure below: Figure 4 As shown in the figure, the equivalent pressure also shows strong transient characteristics, and generally changes in the same way as the equivalent velocity of the electrolyte. After the electrolyte velocity reaches the critical point, the viscous dissipation effect of the electrolyte increases, and the local density fluctuation of the electrolyte causes the kinetic energy to decrease. Due to the spatiotemporal coupling of multiple parameters, the pressure curve shows complex, non-monotonic, transient changes. If the time-varying characteristics of the infiltration pressure are simplified to a constant value, the calculation error will increase significantly.

[0052] This invention ensures computational accuracy by obtaining equivalent pressure and using it as a time-varying boundary condition, while also incorporating corrections to equivalent density. Furthermore, a modular interface enables dynamic parameter transfer between the inflow and infiltration subprocesses, avoiding the enormous computational complexity associated with simultaneously solving multiple coupling problems, such as fragmentation, flow, and penetration. While ensuring the accuracy of the infiltration process, this method improves computational efficiency and provides a high-precision solution tool for studying the activation process of liquid storage backup batteries.

Claims

1. A method for determining the equivalent pressure during the activation process of a liquid storage type reserve battery, characterized in that: The steps include: S10, rotationally symmetric flow field modeling: the geometric center of the liquid storage battery during the activation process is set as the origin of the cylindrical coordinate system, the rotational symmetry axis of the liquid storage battery is set as the axial direction of the cylindrical coordinate system, and the radial direction of the cylindrical coordinate system coincides with the geometric radial direction of the porous electrode of the liquid storage battery, thereby obtaining a rotationally symmetric flow field of the electrolyte of the liquid storage battery as the battery rotates; S20, equivalent density acquisition: calculating the electrolyte equivalent density according to the electrolyte density, air density and real-time electrolyte liquid volume fraction; S30, equivalent velocity acquisition: according to the velocity of the electrolyte in the Cartesian coordinate system, the equivalent velocity in the cylindrical coordinate system is calculated, including radial velocity and circumferential velocity; S40, determining equivalent pressure: according to the equivalent density and equivalent speed, a centrifugal-kinetic energy composite pressure integral model is used to calculate the required equivalent pressure.

2. The method for determining the equivalent pressure during activation according to claim 1, characterized in that: The step of obtaining the equivalent density in step S20 is specifically as follows: the equivalent density of the electrolyte is calculated by the following formula: r eff =EVF·ρ1+(1-EVF)·ρ air (1); Where, ρ eff is the equivalent density of the electrolyte, ρ1 is the density of the electrolyte, ρ air is the air density, and EVF is the electrolyte volume fraction.

3. The method for determining the equivalent pressure during activation according to claim 2, wherein: The step of obtaining the equivalent speed in step S30 includes: S31, radial velocity calculation: Calculate the radial velocity of the electrolyte in the cylindrical coordinate system according to the following formula: S32, Circumferential velocity calculation: Calculate the circumferential velocity of the electrolyte in the cylindrical coordinate system according to the following formula: In the above two equations, x and y represent the position coordinates of the electrolyte in the Cartesian coordinate system, V x and V y Represents the velocity components of the electrolyte in different directions in the Cartesian coordinate system, V y V r is the radial velocity of the electrolyte in the cylindrical coordinate system, V e is the circumferential velocity of the electrolyte in the cylindrical coordinate system.

4. The method for determining the equivalent pressure during activation according to claim 3, wherein: The step of determining the equivalent pressure in step S40 is specifically to calculate the required equivalent pressure according to the following formula: Where, P wetting is the equivalent pressure, is the centrifugal force gradient term, is the inertial kinetic energy term, and V3 is the axial velocity, which is the same as the component of the electrolyte in the z direction in the Cartesian coordinate system.

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