Numerical analysis method for performance study of squeeze supply system

Abstract

The present invention discloses a numerical analysis method for studying the performance of an extrusion supply system. The method includes initializing each part of the grid according to a given extrusion supply system model size to obtain grid units, assigning storage information to the corresponding grid units, and setting an analysis time. The state flux on the adjacent interfaces of the grid units is calculated by the AUSMDV method. The fluid information inside the grid units is calculated by the continuity equation, the momentum equation, and the energy equation. The fluid information at the next moment is calculated within a given time range using the Euler prediction and correction formula based on the fluid information inside the grid units at a certain moment. The state flux on the adjacent interfaces of the grid units is calculated back until the total calculation time step reaches the set analysis time, and the change of the fluid information at each position over time is obtained. The numerical analysis method of the present invention can effectively improve the calculation efficiency and more efficiently detect the change of the fluid parameters at each position of the system during the flow process.

Description

Technical Field

[0001] The present invention belongs to the field of energy and power, and also relates to a numerical analysis method for studying the performance of an alternative supply system. Background Art

[0002] The thermal power system is the "heart" of the underwater vehicle, and its performance is closely related to various motion indicators of the underwater vehicle. Figure 1 As shown, the energy supply system is an important component of the underwater vehicle's thermal power system, which is used to ensure that the propellant is transported to the combustion chamber quickly and stably in a certain proportion within a specified time for combustion. If the specified pressure cannot be established in front of the fuel pump within the specified time, the underwater vehicle will deviate from the starting condition or even fail to start.

[0003] To ensure that a vehicle can operate properly underwater, its manufacturer must demonstrate its feasibility through experimental testing or computer numerical simulation. Experimental testing is the most direct method, conducted entirely under natural conditions. However, this method is costly and cannot simulate the various extreme or unexpected conditions encountered by a vehicle. Consequently, numerical simulation software has become a supporting tool for calculating the internal flow fields of alternative supply systems. Advanced simulation methods can also be used to cost-effectively simulate flow conditions under various extreme conditions. Under these conditions, a class of commercial flow field simulation software using Fluent, CFX, and Star-ccm has gradually developed. However, its simulation of alternative supply systems often relies on a large number of grids and high-performance computers, making it difficult to use for numerical simulation tests of a large number of different models or to quickly detect flow information in a specified cross-section in a short period of time. Summary of the Invention

[0004] The purpose of the present invention is to provide a numerical analysis method for the performance study of a displacement supply system, which can effectively improve the calculation efficiency and more efficiently detect the changes in fluid parameters at various positions in the displacement supply system during the flow process.

[0005] The technical solution adopted by the present invention is a numerical analysis method for studying the performance of a displacement supply system, which is specifically implemented in the following steps:

[0006] Step 1: Initialize each grid according to the given size of the alternative supply system model to obtain grid cells, assign storage information to the corresponding grid cells, and set the analysis time;

[0007] Step 2: Calculate the state flux on the adjacent interfaces of the grid cells using the AUSMDV method;

[0008] Step 3: Calculate the fluid information inside the grid cell using the continuity equation, momentum equation, and energy equation;

[0009] Step 4: Based on the fluid information inside the grid cell at a certain moment, the Euler prediction correction formula is used to calculate the fluid information at the next moment within a given time range;

[0010] Step 5: Return to step 2 until the total calculation time step reaches the set analysis time to obtain the changes in fluid information at each position over time.

[0011] The present invention is also characterized in that:

[0012] In step 1, the specific process of initializing the grids of each part according to the given size of the squeeze-substitute supply system model is as follows: the squeeze-substitute supply system model is discretized into multiple grid cells using the finite volume method.

[0013] The initialization assignment process for the corresponding grid cell is as follows: assign storage information according to the position information of each grid cell. The storage information includes boundary conditions, time step, center position coordinates, interface position coordinates, average value of fluid information, and time derivatives of grid cell mass momentum and energy.

[0014] The specific process of step 2 is as follows: assuming that the fluid information in the grid cell changes linearly, the state average value in the grid cell is used to interpolate the fluid information initialized in the grid cell onto the inner surface of the grid cell to obtain the mass, momentum, and energy flow states on both sides of the left and right ends of the inner surface of each grid cell, that is, the state flux on the adjacent interfaces of the grid cell. The interpolation is performed separately for the fluid information on the adjacent interfaces of the grid cell, and the obtained fluid information is integrated to become the state flux on the adjacent interfaces.

[0015] Fluid information includes grid cell density, velocity, temperature, pressure, internal energy, and speed of sound.

[0016] The continuity equation in step 3 is expressed as:

[0017]

[0018] Where u x is the velocity component in the axial direction; t is time; ρ is density, represents the time-varying mass fraction within a grid cell, It represents the mass flowing in and out of the adjacent interfaces of the grid cells in the axial direction.

[0019] The momentum equation in step 3 is expressed as:

[0020]

[0021] Where p is the pressure inside the grid unit, τ is the component of the viscous stress τ acting on the surface of the microelement due to molecular viscosity, and f is the unit mass force.

[0022] The energy equation in step 3 is expressed as:

[0023]

[0024] Where E is the total energy inside the grid unit, including the sum of internal energy, kinetic energy and potential energy. h is enthalpy; Where T ref =298.15K;k eff is the effective heat transfer coefficient, k eff =k+k t , k t is the turbulent heat transfer coefficient.

[0025] The Euler prediction correction formula in step 4 is expressed as:

[0026]

[0027]

[0028] Where x is the spatial step size of the grid cell, Contains the mass, momentum, and energy within the control volume j unit; Contains the mass flux, momentum flux, and energy flux on the j±1 / 2 unit walls in front and behind the control volume; The mass, momentum, and energy stored in the control body are obtained from the state parameters inside the control body calculated in the previous iteration.

[0029] The beneficial effects of the present invention are:

[0030] The numerical analysis method used in the present invention for studying the performance of an alternative supply system can quickly and accurately calculate the fluid information parameters at each position in the system, and can achieve the purpose of rapid calculation by changing the system size, greatly saving time and cost compared to traditional fluid simulation software. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a principle block diagram of the substitution supply system provided by the present invention;

[0032] Figure 2 It is a flow chart for realizing the simulation method provided by the present invention;

[0033] Figure 3 It is a two-dimensional structural diagram of the extrusion supply system provided by the present invention;

[0034] Figure 4 The present invention provides a user exchange interface based on MATLAB;

[0035] Figure 5 is the pressure change curve of the high-pressure gas cabin terminal obtained by simulation of the present invention;

[0036] Figure 6 This is the pressure change curve of the propellant compartment terminal obtained by simulation of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The numerical analysis method for the performance study of the replacement supply system of the present invention is specifically implemented according to the following steps:

[0039] Step 1: Based on the given size of the displacement supply system model, the displacement supply system model is discretized into multiple grid cells using the finite volume method to obtain grid cells, and storage information is assigned according to the position information of each grid cell. The storage information includes boundary conditions, time step, center position coordinates, interface position coordinates, average value of fluid information, and time derivatives of grid cell mass, momentum, and energy, and the analysis time is set. The fluid information includes grid cell density, velocity, temperature, pressure, internal energy, and speed of sound;

[0040] Step 2: Calculate the state flux on the adjacent interfaces of the grid cells using the AUSMDV method. The specific process is as follows: Assuming that the fluid information within the grid cell changes linearly, the state average value within the grid cell is used to interpolate the fluid information initialized within the grid cell onto the inner surface of the grid cell. The mass, momentum, and energy flow state on both the left and right ends of the inner surface of each grid cell are obtained, that is, the state flux on the adjacent interfaces of the grid cell. Interpolation is performed separately for the fluid information on the adjacent interfaces of the grid cell. The obtained fluid information is integrated and converted into the state flux on the adjacent interfaces. For example, the density on either side of the inner surface is obtained through nonlinear interpolation using the following expression:

[0041]

[0042]

[0043]

[0044]

[0045] Among them, (Δ-) j and (Δ+) j There are two ways to estimate the density slope of the grid (control volume) j, x j-1、x j 、x j+1 is the center point position corresponding to mesh (control volume) j-1, j, j+1. If the two density slopes have the same sign, the MINMOD limiter function will select the density function with the minimum magnitude, otherwise it returns zero.

[0046] Step 3: Calculate the density, velocity, temperature, pressure, internal energy, and speed of sound inside the grid cell using the continuity equation, momentum equation, and energy equation;

[0047] The continuity equation is expressed as:

[0048]

[0049]

[0050] Where u x is the velocity component in the axial direction; t is time; ρ is density, represents the time-varying mass fraction within a grid cell, It represents the mass flowing in and out of the adjacent interfaces of the grid cells in the axial direction.

[0051] The momentum equation is expressed as:

[0052]

[0053] Where p is the pressure inside the grid unit, τ is the component of the viscous stress τ acting on the surface of the microelement due to molecular viscosity, and f is the unit mass force.

[0054] The energy equation is expressed as:

[0055]

[0056] Where E is the total energy inside the grid unit, including the sum of internal energy, kinetic energy and potential energy. h is enthalpy; Where T ref =298.15K;.k eff is the effective heat transfer coefficient, k eff =k+k t , k t is the turbulent heat transfer coefficient.

[0057] The mass, momentum, and energy within the grid cell calculated according to the momentum equation, energy equation, and continuity equation can be used to update the fluid information within the grid cell:

[0058] ρ j =u mass,j

[0059]

[0060]

[0061] where u mass,j 、u momentum,j 、u energy,j are the mass, momentum and energy on the j grid unit respectively; v j is the velocity of the fluid on the unit grid, e j is the specific internal energy of the fluid on the grid unit. Nitrogen in the substitution system can be considered as a thermally perfect gas, so its specific internal energy is proportional to the temperature and can be expressed as:

[0062]

[0063] Among them, c v is the constant volume specific heat capacity of the gas, and then the pressure can be calculated based on the solved density and temperature using the ideal gas state equation:

[0064] p j =ρ j RT j

[0065] Where R is the gas constant.

[0066] The speed of sound is:

[0067]

[0068] Among them, a j is the speed of sound on the grid element, and γ is the specific heat ratio.

[0069] Step 4: Based on the fluid information inside the grid cell at a certain moment (fluid information includes grid cell density, velocity, temperature, pressure, internal energy, and speed of sound), the Euler prediction correction formula is used to calculate the grid cell density, velocity, temperature, pressure, internal energy, and speed of sound at the next moment within a given time range;

[0070] The Euler prediction correction formula is expressed as:

[0071]

[0072]

[0073] Where x is the spatial step size of the grid cell, Contains the mass, momentum, and energy within the control volume j unit; Contains the mass flux, momentum flux, and energy flux on the j±1 / 2 unit walls in front and behind the control volume; The mass, momentum, and energy stored in the control body are obtained from the state parameters inside the control body calculated in the previous iteration.

[0074] Step 5. Return to step 2 until the total calculation time step reaches the set analysis time, and obtain the changes of density, velocity, temperature, pressure, internal energy, and sound speed at each position over time.

[0075] Example

[0076] like Figure 1 As shown, the energy supply system is an important component of the underwater vehicle's thermal power system, which is used to ensure that the propellant is transported to the combustion chamber quickly and stably in a certain proportion within a specified time for combustion. If the specified pressure cannot be established in front of the fuel pump within the specified time, the underwater vehicle will deviate from the starting condition or even fail to start.

[0077] A fast numerical simulation method for an extrusion supply system. This numerical simulation technology can be implemented using Matlab programming and run on a computer to simulate the flow state inside the extrusion supply system.

[0078] The simulation conditions are:

[0079] Diameter of high-pressure gas chamber: 35e-3m Length of high-pressure gas chamber: 1.6m

[0080] Valve diameter: 6e-3m Valve length: 6e-3m

[0081] Pipeline 1 diameter: 15e-3m Pipeline 1 length: 50e-3m

[0082] Pipeline 2 diameter: 20e-3m Pipeline 2 length: 500e-3m

[0083] Propellant tank volume: 0.024L

[0084] Initial pressure: 0.1MPa Initial temperature: 300K

[0085] High-pressure chamber pressure: 20MPa High-pressure chamber temperature: 300K

[0086] like Figure 2 As shown in the figure, after determining the model size, the equation is simplified according to the structural characteristics of the model. Figure 3 The model shown is discretized into adjacent grid cells, and the initialized fluid information is assigned to the center point of the grid. After calculating the state flux of the grid interface through the AUSMDV method, the fluid information in each grid cell is calculated through the continuity equation, momentum equation, and energy equation. Finally, the fluid information parameters in the grid cell at the next moment are calculated through the Euler prediction correction formula.

[0087] Based on this program, Figure 4 The simple user interface shown is used to modify the process of obtaining the internal fluid flow of the system under different sizes. After calculation, the final result is as follows Figure 5 and Figure 6 The pressure curves at the end of the high-pressure gas tank and the middle of the push-pull cabin of the system model are shown.

[0088] Figure 5 and Figure 6 It is a curve of pressure change at different positions over time calculated by the program. Compared with traditional commercial software, it is fast in calculation and has accurate numerical values.

[0089] Through the above-mentioned method, the numerical analysis method of the present invention for studying the performance of the extrusion supply system can quickly and accurately calculate the fluid information parameters at each position of the system, and can achieve the purpose of fast calculation by changing the system size, which greatly saves time cost compared with traditional fluid simulation software.

Claims

1. A numerical analysis method for the performance study of a replacement supply system, characterized in that: Please follow the steps below to implement it: Step 1: Initialize each grid according to the given size of the alternative supply system model to obtain grid cells, assign storage information to the corresponding grid cells, and set the analysis time; The stored information includes boundary conditions, time steps, center position coordinates, interface position coordinates, average values ​​of fluid information, and time derivatives of grid cell mass momentum and energy; Step 2: Calculate the state flux on the adjacent interfaces of the grid cells using the AUSMDV method; Step 3: Calculate the fluid information inside the grid cell using the continuity equation, momentum equation, and energy equation; Step 4: Based on the fluid information inside the grid cell at a certain moment, the Euler prediction correction formula is used to calculate the fluid information at the next moment within a given time range; Step 5: Return to step 2 until the total calculation time step reaches the set analysis time to obtain the changes in fluid information at each position over time.

2. The numerical analysis method for performance research of a replacement supply system according to claim 1 is characterized in that: The specific process of initializing each part of the grid according to the given size of the squeeze-substitute supply system model described in step 1 is: using the finite volume method to discretize the squeeze-substitute supply system model into multiple grid units.

3. The numerical analysis method for performance research of a replacement supply system according to claim 1, characterized in that: The process of initializing and assigning values ​​to the corresponding grid units is as follows: assigning storage information according to the position information of each grid unit.

4. The numerical analysis method for performance research of a replacement supply system according to claim 3 is characterized in that: The specific process of step 2 is as follows: assuming that the fluid information in the grid cell changes linearly, the fluid information assigned by the initialization in the grid cell is interpolated onto the inner surface of the grid cell using the state average value in the grid cell to obtain the flow state of mass, momentum and energy on both sides of the left and right ends of the inner surface of each grid cell, that is, the state flux on the adjacent interface of the grid cell.

5. The numerical analysis method for performance research of a replacement supply system according to claim 1, 3 or 4, characterized in that: The fluid information includes grid cell density, velocity, temperature, pressure, internal energy, and speed of sound.

6. The numerical analysis method for performance research of a replacement supply system according to claim 5 is characterized in that: The continuity equation in step 3 is expressed as: ， Where, is the velocity component in the axial direction; For time; is the density, represents the time-varying mass fraction within a grid cell, It represents the mass flowing in and out of the adjacent interfaces of the grid cells in the axial direction.

7. The numerical analysis method for performance research of a replacement supply system according to claim 6, characterized in that: The momentum equation in step 3 is expressed as: , Where, is the pressure inside the grid cell; The effect caused by molecular viscosity on the surface of the microelement x Viscous stress in the direction τ in x The direction of the component, The effect caused by molecular viscosity on the surface of the microelement x Viscous stress in the direction τ in y The direction of the component, The effect of molecular viscosity on the surface of the microelement x Viscous stress in the direction τ in z Directional component; is the force per unit mass.

8. The numerical analysis method for performance research of a replacement supply system according to claim 7, characterized in that: The energy equation in step 3 is expressed as: , Where, is the total energy inside the grid cell, including the sum of internal energy, kinetic energy and potential energy, ; is enthalpy; ,in =298.15K; is the effective heat transfer coefficient, , is the turbulent heat transfer coefficient.

9. The numerical analysis method for performance research of a replacement supply system according to claim 1, characterized in that: The Euler prediction correction formula described in step 4 is expressed as: in, x is the spatial step size of the grid cell, Contains control body j Mass, momentum, and energy within the unit cell; Including the control body before and after Mass flux, momentum flux, and energy flux on the cell wall; The mass, momentum, and energy stored in the control body are obtained from the state parameters inside the control body calculated in the previous iteration.

Images