A CFD-6DOF Strong Coupling Numerical Calculation Method for the Transient Self-Flow Process of Vane Pumps

Abstract

The present invention provides a CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump, including: S1: establishing a hydrodynamic geometric model file; S2: performing discretization processing and mesh division; S3: coupling the hydrodynamic control equation and the six-degree-of-freedom motion equation; S4: setting the initial boundary conditions and the inherent physical properties of the rotor rigid body structure; S5: calculating the torque generated by each grid node on the rotor structure wall surface; S6: calculating the angular velocity generated by the rotor at the time step of S5 to obtain the angular displacement; S7: updating the positions of each grid node in the rotating domain and correcting the flux field; S8: solving the flow field at the next time step of the system, iteratively correcting the flow field, and returning to S5 to perform cyclic calculations for each time step until the calculations for all time steps are completed and the results are output; S9: differentiating the angular displacements calculated for each time step. The present invention can obtain the transient evolution law of the flow field during the self-flow process of the pump, making the numerical analysis results closer to the actual engineering requirements.

Description

Technical Field

[0001] The present invention relates to the technical research field of the transient self-flow process of vane pumps, and particularly relates to a CFD (Computational Fluid Dynamics)-6DOF (Six Degrees of Freedom Motion Equation) coupling calculation method for the transient self-flow process of vane pumps. Background Art

[0002] The self-flow working condition is a relatively special operating condition in the full characteristic curve of the pump, that is, when the pump is under no drive, the impeller inlet is impacted by the liquid flow and rotates passively. Its operating characteristics are positive rotational speed, positive flow rate, and negative head. The self-flow working condition generally appears when the vane pump starts. For example, in a liquid rocket engine, when the turbopump starts with the valve open, a self-flow phenomenon will be caused under the action of the storage tank pressure and the liquid column pressure. The flow resistance, torque, etc. in the self-flow state have a relatively important impact on the stability of the turbopump in the initial stage of startup.

[0003] At present, the numerical calculation of the self-flow working condition of vane pumps at home and abroad basically obtains the impeller rotational speed by measuring torque or fitting test data. In the calculation process, the interaction between the rotor structure and the fluid is not well considered, and there is a certain error from the actual situation. The self-flow of vane pumps is usually a transient transition process. Its self-flow rotational speed rises from zero to a stable value under the action of fluid force. The existing research mainly focuses on the flow characteristics of the pump at the stable self-flow rotational speed, lacking the research on the self-flow transient process. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a CFD-6DOF coupling calculation method for the transient self-flow process of vane pumps, which can accurately calculate the rotational speed change of the rotor's passive rotation during the transient self-flow process of the pump and obtain the transient evolution of the flow field during the self-flow process of the pump.

[0005] The present invention realizes the above technical objectives through the following technical means.

[0006] A CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of vane pumps, comprising:

[0007] S1: Establish a hydrodynamic geometric model file of the pump's self-flow passive rotation system;

[0008] S2: Discretize and mesh the pump's rotating domain and stationary domain;

[0009] S3: Couple the hydrodynamic control equation and the six degrees of freedom motion equation;

[0010] S4: Set the initial boundary conditions of the flow field and the inherent physical properties of the rotor rigid body structure;

[0011] S5: Calculate the torque generated on each grid node of the rotor structure wall due to the fluid force based on the velocity-pressure values of the flow field at the current time step.

[0012] S6: Based on the force conditions on the grid nodes of the rotor wall, calculate the angular velocity of the rotor generated by the fluid action at the time step of step S5 according to the six-degree-of-freedom motion equation, and obtain the angular displacement at the current time step.

[0013] S7: Update the positions of each grid node in the rotating domain based on the angular displacement results calculated in step S6, and correct the flux field according to the grid motion.

[0014] S8: Solve the flow field of the system at the next time step according to the fluid dynamics control equation, and use the pressure correction algorithm to iteratively correct the flow field so that the velocity field satisfies the continuity equation, and then return to step S5 to perform loop calculations for each time step until all time steps are calculated, and then stop the loop and output the results.

[0015] S9: Differentiate the angular displacements calculated for each time step to obtain the change in the rotor angular velocity and the evolution law of the flow field during the transient self-flow process of the pump.

[0016] Furthermore, step S1 is specifically as follows: Based on the given geometric parameters of the vane pump, establish the flow field models of the pump rotating domain and the stationary domain in Creo, set the structural material properties, and calculate the physical parameters of the rotor rigid body structure.

[0017] Furthermore, step S2 includes:

[0018] Import the geometric model file of the pump system established in step S1 into ICEM CFD software, perform feature recognition and define the boundary surface properties, use the structured block method to perform hexahedral mesh division on each calculation domain of the pump, and encrypt the meshes at the volute tongue, blade inlet, and clearance positions.

[0019] Furthermore, step S3 is specifically as follows:

[0020] Step S3.1: Solve the flow field of the pump during the self-flow process using the Navier-Stokes equations. Its control equation set includes the mass conservation equation, the momentum conservation equation, and the energy conservation equation, where:

[0021] The mass conservation equation is as follows:

[0022]

[0023] Among them, ρ is the density of the fluid particle, t is the time, and V is the fluid velocity vector.

[0024] The momentum conservation equation is:

[0025]

[0026] Among them, p is the pressure on the fluid micro - control volume, and τ xx , τ xy , τ xz etc. are the components of the viscous stress τ on the surface of the micro - element in the x, y, and z directions. F x , F y , F z are the components of the body force in the x, y, and z directions of the micro - element;

[0027] The energy conservation equation is:

[0028]

[0029] In the formula, is the volumetric heating rate per unit mass, ρ is the fluid density, V is the fluid velocity vector, f is the body force on the fluid micro - mass per unit mass, u, v, and w are the velocity components in the x, y, and z directions respectively, and (e + V 2 ) / 2 is the sum of the internal energy and kinetic energy;

[0030] Step S3.2: Coupling the Euler dynamics equation is used to calculate the angular velocity of the impeller pump's rotor rotating passively under the impact of self - flowing. The control equation is as follows:

[0031]

[0032] Among them, L is the inertia - moment tensor, is the torque vector, is the angular - velocity vector, is the angular acceleration.

[0033] Furthermore, the specific content of step S4 is as follows:

[0034] The sliding - mesh method is adopted at the interface between the rotating domain and the stationary domain of the pump, and the boundary conditions of velocity inlet and pressure outlet are adopted at the inlet and outlet respectively;

[0035] Define the discrete format. The convective term adopts the second - order upwind format, and the pressure - velocity coupling adopts the PIMPLE algorithm;

[0036] Define the six - degree - of - freedom motion attributes of the pump rotor, set its mass, moment of inertia, motion constraints, gravity, and drag torque, and determine the rotation center and the coordinates of the rotation axis to make the rotor only rotate around the axis;

[0037] Set the dynamic - mesh reconstruction and smoothing parameters according to the maximum and minimum dimensions of the mesh.

[0038] Further, the specific steps of step S5 are as follows: Calculate the force and moment conditions of the rotor based on the pressure values at the nodes on the rotating wall surface of the rotor. In six-degree-of-freedom motion, it is necessary to convert the moment from the inertial coordinate system to the body coordinate system as follows:

[0039]

[0040] Where R is the transformation matrix as follows:

[0041]

[0042] Where, C x = cos(x), S x = sin(x), and the angles θ and ψ are Euler angles, representing the rotation angles around the z, x, and y axes respectively.

[0043] Advantages of the present invention:

[0044] Based on the CFD-6DOF strong coupling numerical calculation method, the present invention calculates the transient self-flow process of the pump. By coupling the hydrodynamic equation with the six-degree-of-freedom motion equation, it can effectively calculate the interaction between the fluid domain and the structure, obtain the angular velocity change of the rotor caused by the fluid force during the self-flow process of the pump, and provide better theoretical support for the research on the flow mechanism of the pump during the transient self-flow process. Description of the drawings

[0045] Figure 1 Is the flow chart of the CFD-6DOF coupling calculation method for the transient self-flow process of the vane pump in the embodiment of the present invention;

[0046] Figure 2 Is the curve of the rotational speed changing with time during the transient self-flow process of the pump obtained by calculation.

[0047] Figure 3 Is the curve of the rotor torque changing with time obtained by calculation.

[0048] Figure 4 Is the curve of the rotational speed changing with time during the transient self-flow process of the pump.

[0049] Figure 5 Is the evolution of the internal flow field at each moment during the transient self-flow process of the vane pump. Detailed implementation manners

[0050] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0051] Please refer to Figure 1 , a CFD-6DOF coupling calculation method for the transient self-flow process of a vane pump according to the present invention, comprising the following steps:

[0052] Step S1: Establish a hydrodynamic geometric model file of the pump self-flow passive rotation system;

[0053] Specifically, according to the given geometric parameters of the vane pump, establish a flow field model of the pump rotation domain and the stationary domain in Creo, set the structural material properties, and calculate the physical parameters of the rotor rigid body structure, such as mass, moment of inertia, and other parameters.

[0054] Step S2: Perform discretization processing and mesh generation of the pump rotation domain and the stationary domain;

[0055] Specifically, import the pump geometric model into the ICEM CFD software, identify features and define boundary surface properties, use the structured block method to perform hexahedral mesh generation on each calculation domain of the pump, and encrypt the mesh at the volute tongue, blade inlet, and clearance positions.

[0056] Step S3: Couple the hydrodynamic control equations and the six-degree-of-freedom motion equations;

[0057] Step S3.1: Use the Navier-Stokes equation to solve the flow field of the pump during the self-flow process. Its control equation set includes the mass conservation equation, the momentum conservation equation, and the energy conservation equation:

[0058] The mass conservation equation is as follows:

[0059]

[0060] Among them, ρ is the density of the fluid particle, t is the time, and V is the fluid velocity vector;

[0061] The momentum conservation equation is:

[0062]

[0063] Among them, p is the pressure on the fluid microelement control volume, τ xx , τ xy , τ xzThe like are the components τ of the viscous stress on the surface of the infinitesimal element in the x, y, and z directions, F x , F y , F z are the components of the body force of the infinitesimal element in the x, y, and z directions;

[0064] The energy conservation equation is:

[0065]

[0066] In the formula, is the volumetric heating rate per unit mass, ρ is the fluid density, V is the fluid velocity vector, f is the body force on the fluid microelement per unit mass, u, v, and w are the velocity components in the x, y, and z directions respectively, and (e + V 2 ) / 2 is the sum of the internal energy and the kinetic energy, that is, the total energy.

[0067] Step S3.2: Couple the Euler dynamics equation to calculate the angular velocity of the impeller pump when the rotor rotates passively under the impact of self-flow. The control equation is as follows:

[0068]

[0069] Among them, L is the inertia tensor, is the torque vector, is the angular velocity vector, is the angular acceleration.

[0070] Step S4: Set the initial boundary conditions of the flow field and the inherent physical properties of the rotor rigid body structure;

[0071] Specifically, the sliding mesh method is adopted at the interface between the rotating domain and the stationary domain of the pump, and the boundary conditions of velocity inlet and pressure outlet are adopted at the inlet and outlet respectively; the discretization format is defined, the second-order upwind format is adopted for the convection term, and the PIMPLE algorithm is adopted for the pressure-velocity coupling; the six-degree-of-freedom motion attributes of the pump rotor are defined, and its mass, moment of inertia, motion constraints, gravity, and resistance torque and other parameters are set, and the rotation center and the axis coordinates are determined to make the rotor only rotate around the axis; the dynamic mesh reconstruction and smoothing parameters are set according to the maximum and minimum dimensions of the mesh.

[0072] Step S5: Calculate the torque generated on each grid node of the rotor structure wall under the action of the fluid force based on the velocity-pressure values of the flow field at the current time step;

[0073] Specifically, according to the pressure values at the nodes on the rotating wall of the rotor, calculate the force and torque conditions of the rotor, and in the six-degree-of-freedom motion, it is necessary to convert the torque from the inertial coordinate system to the body coordinate system, as follows:

[0074]

[0075] where R is the transformation matrix, as follows:

[0076]

[0077] where, C x = cos(x), S x = sin(x), and the angles θ and ψ are Euler angles, representing the rotation angles about the z, x, and y axes respectively.

[0078] Step S6: Based on the force conditions on the grid nodes of the rotor wall surface, calculate the angular velocity of the rotor generated by the fluid action at the time step of Step S5 according to the six-degree-of-freedom motion equation, and obtain the angular displacement at the current time step;

[0079] Specifically, calculate the instantaneous angular velocity of the rotor according to Euler's dynamics equation, and calculate the angular displacement at the current time step through the instantaneous angular velocity to obtain the instantaneous rotation angle of the rotor.

[0080] Step S7: Update the positions of each grid node in the rotation domain based on the angular displacement result calculated in Step S6, and correct the flux field according to the grid motion;

[0081] Specifically, the rotor wall surface rotates at an angle under the action of fluid force at the current time step, and the positions of the grid nodes on the rotation domain change. The grid of the rotation domain is updated by the dynamic grid method, and the change of the rotation domain grid affects the flow field, so the flux field needs to be corrected to ensure the stability of the calculation and avoid divergence.

[0082] Step S8: Solve the flow field of the system at the next time step according to the fluid dynamics control equation, and use the pressure correction algorithm to iteratively correct the flow field so that the velocity field satisfies the continuity equation, and return to Step S5 to perform loop calculations for each time step;

[0083] Step S9: When the calculations for all time steps are completed, stop the loop and output the results; by differentiating the angular displacements calculated for each time step, obtain the change of the rotor angular velocity, and accurately obtain the flow field evolution law during the transient self-flow process of the pump.

[0084] Furthermore, the CFD-DOF strong coupling numerical calculation method for the transient self-flow process of the pump can effectively calculate the change of the rotor speed under the self-flow impact, refer to Figure 2 and obtain the fluctuation curve of the rotor torque varying with time, refer to Figure 3 ; by monitoring the pressures at the inlet and outlet of the pump, refer to Figure 4 calculate the self-flow loss of the vane pump; and can obtain the evolution of the internal flow field of the vane pump at different moments during the self-flow process, and the variation characteristics of the pulsating pressure, refer to Figure 5 .

[0085] The present invention can be applied to the calculation of the passive rotation of the impeller inlet under the impact of liquid flow when the pump has no drive, its gravity flow performance and internal flow field; for the calculation of the hydraulic performance and internal flow field of the circulation pump in the underwater vehicle cooling system under the gravity flow condition; for the calculation of the performance and flow state of the gravity self-flow fuel supply system of the aeroengine fuel pump; for the calculation of the self-flow caused by the storage tank pressure and liquid column pressure when the liquid rocket engine turbopump starts with the valve open. It provides technical guidance for the design and research and development of related special fluid machinery equipment.

[0086] The above embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump, characterized in that, Including: Step S1: Establish a hydrodynamic geometric model file for the pump self-flow passive rotation system; Step S2: Discretize and mesh the pump rotation domain and stationary domain; Step S3: Couple the hydrodynamic control equations and the six-degree-of-freedom motion equations; Step S4: Set the initial boundary conditions of the flow field and the inherent physical properties of the rotor rigid body structure; Step S5: Calculate the torque generated on each grid node of the rotor structure wall due to the action of the fluid force based on the velocity-pressure values of the flow field at the current time step; Step S6: Calculate the angular velocity of the rotor generated by the action of the fluid at the time step of Step S5 based on the six-degree-of-freedom motion equations according to the force conditions on the grid nodes of the rotor wall, and obtain the angular displacement at the current time step; Step S7: Update the positions of each grid node in the rotation domain based on the angular displacement results calculated in Step S6, and correct the flux field according to the grid motion; Step S8: Solve the flow field of the system at the next time step according to the hydrodynamic control equations, perform iterative correction on the flow field so that the velocity field satisfies the continuity equation, and return to Step S5 to perform cyclic calculations for each time step until after all time steps are calculated, stop the loop and output the results; Step S9: Differentiate the angular displacements calculated for each time step to obtain the change in the rotor angular velocity and the flow field evolution law during the pump transient self-flow process.

2. The CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump according to claim 1, wherein The specific content of Step S1 is: Based on the given geometric parameters of the vane pump, establish a flow field model of the pump rotation domain and stationary domain in Creo, set the structural material properties, and calculate the physical parameters of the rotor rigid body structure.

3. The CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump according to claim 1, characterized in that The specific content of Step S2 includes: Import the pump system geometric model file established in Step S1 into the ICEM CFD software, perform feature recognition and define the boundary surface properties, use the structured block method to perform hexahedral meshing on each calculation domain of the pump, and perform mesh encryption at the volute tongue, blade inlet, and clearance positions.

4. The CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump according to claim 1, wherein The specific content of Step S3 is: Step S3.1: Use the Navier-Stokes equations to solve the flow field during the self-flow of the pump. Its control equation set includes the mass conservation equation, momentum conservation equation, and energy conservation equation, where: The mass conservation equation is as follows: where ρ is the fluid density, t is the time, and V is the fluid velocity vector; The momentum conservation equation is: Among them, p is the pressure on the fluid microelement control volume, τ xx , τ xy , τ xz are the components of the viscous stress τ on the surface of the microelement in the x, y, and z directions, and F x , F y , F z are the components of the body force of the microelement in the x, y, and z directions; The energy conservation equation is: In the formula, is the volumetric heating rate per unit mass, ρ is the fluid density, V is the fluid velocity vector, f is the body force on the fluid parcel per unit mass, u, v, and w are the velocity components in the x, y, and z directions respectively, and (e + V 2 ) / 2 is the sum of the internal energy and the kinetic energy; Step S3.2: Couple the Euler dynamics equations to calculate the angular velocity of the vane pump when the rotor is passively rotated by the self-flow impact. The control equation is as follows: where L is the inertia tensor, is the torque vector, is the angular velocity vector, is the angular acceleration.

5. The CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump according to claim 1, characterized in that The specific content of Step S4 is: The sliding mesh method is used at the interface between the pump rotation domain and the stationary domain, and the boundary conditions of velocity inlet and pressure outlet are used at the inlet and outlet respectively; Define the discretization format, use the second-order upwind format for the convection term, and use the PIMPLE algorithm for the pressure-velocity coupling; Define the six-degree-of-freedom motion attributes of the pump rotor, set its mass, moment of inertia, motion constraints, gravity, and drag torque, determine the rotation center and the coordinates of the rotation axis, so that the rotor can only rotate around the axis; Set the dynamic mesh reconstruction and smoothing parameters according to the maximum and minimum dimensions of the mesh.

6. The CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump according to claim 1, wherein The specific content of step S5 is as follows: According to the pressure values at the nodes on the rotating wall surface of the rotor, calculate the force and moment conditions of the rotor. And in the six-degree-of-freedom motion, it is necessary to transform the moment from the inertial coordinate system to the body coordinate system as follows: where R is the transformation matrix as follows: where C x = cos(x), S x = sin(x), and the angles φ, θ, and ψ are Euler angles representing the rotation angles about the z, x, and y axes, respectively.

7. The CFD-6DOF strong coupling numerical calculation method for the transient self-flow process of a vane pump according to claim 1, characterized in that In step S8, a pressure correction algorithm is used to iteratively correct the flow field.

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