Numerical simulation method and device for piston oil injection cooling process

Abstract

The invention relates to the technical field of numerical simulation, in particular to a numerical simulation method and device for a piston oil injection cooling process, and the method comprises the steps: building a large-density-ratio gas-liquid two-phase flow SPH calculation model; establishing a heat flux boundary heat transfer calculation model; establishing a calculation model of the pressure type outlet boundary, including establishment of a buffer area, arrangement of seed points, introduction and updating of virtual mass, generation of a particle mechanism and deletion of a particle mechanism; the seed points are used for representing templates of generated particles; and performing numerical simulation on the piston oil injection cooling process based on a large-density-ratio gas-liquid two-phase flow SPH calculation model, a heat flux boundary heat transfer calculation model and a pressure type outlet boundary calculation model. According to the method, the weak compressibility assumption can be adopted to perform numerical simulation on the piston oil injection cooling process, and the calculation amount of numerical simulation is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of numerical simulation, and in particular to a numerical simulation method and device for a piston oil spray cooling process. Background Art

[0002] In the aerospace industry, the cylinder pushes the piston to vibrate at high frequency and high speed. The mixture of oil and air flows inside the piston, and the heat dissipation characteristics of its oil injection are of great concern. When a closed boundary is used, the large-scale reciprocating vibration of the piston causes a large range of changes in the particle volume, which in turn affects the weak compressibility assumption in the traditional SPH numerical simulation process.

[0003] The existing solution is to make the external dimensions of the piston vibration pipe much larger than the box of the pipe, so that the volume change caused by the piston vibration will not cause a large-scale change in the volume of particles in the overall calculation domain, so that it still complies with the weak compressibility assumption. However, this solution will lead to a sharp increase in the amount of calculation, and even make it impossible to simulate the piston oil injection cooling process. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a method and device for numerical simulation of the piston oil spray cooling process, which can use the weak compressibility assumption to numerically simulate the piston oil spray cooling process, thereby reducing the amount of calculation of the numerical simulation.

[0005] In a first aspect, an embodiment of the present application provides a numerical simulation method for a piston oil spray cooling process, the method comprising: A SPH calculation model for gas-liquid two-phase flow with a large density ratio is established; the continuity equation between similar fluids in the SPH calculation model for gas-liquid two-phase flow with a large density ratio adopts a simplified delta term smoothing pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model for gas-liquid two-phase flow with a large density ratio is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and background pressure term; Establish a heat flux boundary heat transfer calculation model; Establishing a calculation model of a pressure-type outlet boundary, the calculation model of the pressure-type outlet boundary includes the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the template of the generated particles; The piston oil injection cooling process is numerically simulated based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the pressure-type outlet boundary calculation model.

[0006] In a possible implementation manner, the continuity equation in the large density ratio gas-liquid two-phase flow SPH calculation model is established by the following steps: By introducing the multiphase delta term, the continuity equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is obtained: ; ; in, is the dissipation term of the density of the ith particle, is a constant, is the arithmetic mean of the smooth length of the i-th particle and the smooth length of the j-th particle searched in the computational domain, is the arithmetic mean of the sound velocity of the ith particle and the sound velocity of the jth particle searched in the computational domain, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, is the density of the ith particle, is the density of the jth particle searched in the computational domain, is the physical property relationship between the ith particle and the jth particle searched in the computational domain, is the physical property of the ith particle, is the physical property of the jth particle searched in the computational domain.

[0007] In a possible implementation manner, the momentum equation in the large density ratio gas-liquid two-phase flow SPH calculation model includes: The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is expressed by the following formula for the discretization of the pressure gradient term: ; in, is the pressure gradient term of the ith particle, is the pressure of the ith particle, is the first The pressure of a particle.

[0008] The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is expressed by the following formula for the velocity change: ; in, is the change in velocity of the ith particle caused by the artificial viscosity term, is a constant, is the velocity vector difference between the velocity vector of the i-th particle and the velocity vector of the j-th particle searched in the computational domain.

[0009] In a possible implementation manner, the connection between the density term and the pressure term in the large density ratio gas-liquid two-phase flow SPH calculation model is established through the following steps: The Tait equation of state EOS is introduced to obtain the relationship between the density term and the pressure term in the SPH calculation model of the large density ratio gas-liquid two-phase flow: ; ; ; in, is the pressure of the particle, is the reference density, is the reference sound speed, is the adiabatic coefficient of the particle, is the density of the particle, is the background pressure, , is the density change of the particle, is the maximum speed in the piston spraying scenario, is the maximum pressure in the piston oil injection scenario.

[0010] In a possible implementation, the heat flux boundary heat transfer calculation model includes: Calculate the surface identification parameters of particles in the piston spray scene ; If the surface identification parameters of particles in the piston spray scene If it is less than the preset value, the i-th particle is a solid surface particle; The temperature change caused by the heat flux input or output from the solid boundary is calculated based on the solid surface particles.

[0011] In a possible implementation, the calculation model of the pressure-type outlet boundary includes: The area pointed to by the positive normal of the pressure-type outlet boundary is the buffer area; the area pointed to by the opposite direction corresponding to the positive normal of the pressure-type outlet boundary is the internal area; Extending a preset distance from the pressure outlet boundary in the direction pointed by the corresponding positive normal , a particle adding and deleting layer is obtained; seed points are arranged in the particle adding and deleting layer, and the spacing distance of the seed points is positively correlated with the size of the particles.

[0012] In a possible implementation, the particle deletion mechanism includes: Calculate the position vector of the i-th particle The position vector of the center point of the pressure profile outlet boundary The difference between ; The rotation matrix R of the pressure outlet boundary, the vector difference , map the i-th particle to the standard plane, and obtain the position coordinates of the i-th particle on the standard plane ( , , ); According to the position coordinates on the standard plane ( , , ), determine the area where the i-th particle is located; If the region where the i-th particle is located is outside the particle adding and deleting layer, the i-th particle is deleted.

[0013] In a possible implementation, the particle generation mechanism includes: Assign a virtual mass M to each seed point s, where the initial value of the virtual mass M of the seed point s is 0; The velocity at the interpolation point I is obtained by interpolating the flow field around the pressure-type outlet boundary through the density, volume and velocity of all particles at the pressure-type outlet boundary. and density ; According to the velocity at the interpolation point I and density , the virtual mass of the seed point s at the current time step , generates the virtual mass of the seed point s at the next time step ; like , then the position information and flow field information of the new particle Q are generated according to the position information of the seed point s; wherein, for Round down, for Round down.

[0014] In a second aspect, the embodiment of the present application further provides a numerical simulation device for a piston oil spray cooling process, the numerical simulation device for a piston oil spray cooling process comprising: Establishing a module for establishing a SPH calculation model for gas-liquid two-phase flow with a large density ratio; the continuity equation between similar fluids in the SPH calculation model for gas-liquid two-phase flow with a large density ratio adopts a simplified delta term smoothing pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model for gas-liquid two-phase flow with a large density ratio is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and background pressure term; The establishment module is also used to establish a heat flux boundary heat transfer calculation model; The establishment module is further used to establish a calculation model of the pressure-type outlet boundary, wherein the calculation model of the pressure-type outlet boundary includes the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the template of the generated particles; The numerical simulation module is used to perform numerical simulation on the piston oil injection cooling process based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the pressure type outlet boundary calculation model.

[0015] In a possible implementation, a module is established, specifically for establishing a continuity equation in the SPH calculation model of a large density ratio gas-liquid two-phase flow through the following steps: introducing a multiphase delta term to obtain the continuity equation in the SPH calculation model of a large density ratio gas-liquid two-phase flow: ; ;in, is the dissipation term of the density of the ith particle, is a constant, is the arithmetic mean of the smooth length of the i-th particle and the smooth length of the j-th particle searched in the computational domain, is the arithmetic mean of the sound velocity of the ith particle and the sound velocity of the jth particle searched in the computational domain, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, is the density of the ith particle, is the density of the jth particle searched in the computational domain, is the physical property relationship between the ith particle and the jth particle searched in the computational domain, is the physical property of the ith particle, is the physical property of the jth particle searched in the computational domain.

[0016] In a third aspect, an embodiment of the present application further provides an electronic device, comprising: a processor, a storage medium and a bus, wherein the storage medium stores machine-readable instructions executable by the processor, and when the electronic device is running, the processor communicates with the storage medium via the bus, and the processor executes the machine-readable instructions to perform the steps of the numerical simulation method of the piston oil injection cooling process as described in any one of the first aspects.

[0017] In a fourth aspect, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the numerical simulation method of the piston oil spray cooling process as described in any one of the first aspects are executed.

[0018] The embodiment of the present application provides a numerical simulation method and device for a piston oil injection cooling process, the method comprising: establishing a large density ratio gas-liquid two-phase flow SPH calculation model; the continuity equation between similar fluids in the large density ratio gas-liquid two-phase flow SPH calculation model adopts a simplified delta term smoothing pressure field, the momentum equation introduces an artificial viscosity term, and the connection between the density term and the pressure term is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and background pressure term; establishing a heat flux boundary heat transfer calculation model; establishing a calculation model for a pressure-type outlet boundary, including the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the templates of the generated particles; based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the calculation model of the pressure-type outlet boundary, the piston oil injection cooling process is numerically simulated. Through the present application, the weak compressibility assumption can be used to perform numerical simulation on the piston oil injection cooling process, reducing the amount of calculation of the numerical simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A flow chart showing a numerical simulation method for a piston oil spray cooling process provided by an embodiment of the present application is shown; Figure 2 A schematic diagram of the structure of the pressure-type outlet boundary provided in an embodiment of the present application is shown; Figure 3A schematic structural diagram of a numerical simulation device for a piston oil spray cooling process provided by an embodiment of the present application is shown; Figure 4 A schematic structural diagram of an electronic device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the drawings in the present application only serve the purpose of explanation and description and are not used to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn in real proportion. The flowchart used in this application shows the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowchart can be implemented out of sequence, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art can add one or more other operations to the flowchart under the guidance of the content of the present application, or remove one or more operations from the flowchart.

[0022] In addition, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0023] In order to enable those skilled in the art to use the content of this application, the following implementation is provided in conjunction with the specific application scenario "the field of numerical simulation technology". For those skilled in the art, the general principles defined herein can be applied to other embodiments and application scenarios without departing from the spirit and scope of this application. Although this application is mainly described around the "field of numerical simulation technology", it should be understood that this is only an exemplary embodiment.

[0024] It should be noted that the term "comprising" will be used in the embodiments of the present application to indicate the existence of the features declared thereafter, but does not exclude the addition of other features.

[0025] A numerical simulation method for a piston oil spray cooling process provided in an embodiment of the present application is described in detail below.

[0026] Reference Figure 1As shown, it is a flow chart of a numerical simulation method of a piston oil spray cooling process provided by an embodiment of the present application, and each step is described in detail below: S101. Establish a SPH calculation model for gas-liquid two-phase flow with large density ratio.

[0027] In the implementation mode of the present application, the continuity equation between similar fluids in the SPH calculation model of gas-liquid two-phase flow with large density ratio adopts a simplified delta term to smooth the pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model of gas-liquid two-phase flow with large density ratio is explicitly established by adopting the weak compressibility assumption and introducing the Tait state equation and the background pressure term. The continuity equation between similar fluids in the SPH calculation model of gas-liquid two-phase flow with large density ratio, the connection between the density term and the pressure term, the discretization of the momentum equation for the pressure gradient term, and the momentum equation for the velocity change are established for the particles in the internal area.

[0028] Specifically, the continuity equation in the large density ratio gas-liquid two-phase flow SPH calculation model is established through the following steps: By introducing the multiphase delta term, the continuity equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is obtained: ; ; in, is the dissipation term of the density of the ith particle, is a constant (usually 0.1), is the arithmetic mean of the smooth length of the i-th particle and the smooth length of the j-th particle searched in the computational domain, is the arithmetic mean of the sound velocity of the ith particle and the sound velocity of the jth particle searched in the computational domain, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, is the density of the ith particle, is the density of the jth particle searched in the computational domain, is the physical property relationship between the ith particle and the jth particle searched in the computational domain, is the physical property of the ith particle, is the physical property of the jth particle searched in the computational domain.

[0029] Specifically, the momentum equation in the SPH calculation model of large density ratio gas-liquid two-phase flow includes: Step 1: The momentum equation in the SPH calculation model of large density ratio gas-liquid two-phase flow is discretized for the pressure gradient term by the following formula: ; in, is the pressure gradient term of the ith particle, is the pressure of the ith particle, is the first The pressure of a particle.

[0030] Step 2: The momentum equation in the SPH calculation model of large density ratio gas-liquid two-phase flow is expressed by the following formula for velocity change: ; in, is the change in velocity of the ith particle caused by the artificial viscosity term, is a constant (usually 0.05), is the velocity vector difference between the velocity vector of the i-th particle and the velocity vector of the j-th particle searched in the computational domain.

[0031] Specifically, the connection between the density term and the pressure term in the SPH calculation model of the large density ratio gas-liquid two-phase flow is established through the following steps: By introducing the Tait equation of state EOS, the relationship between the density term and the pressure term in the SPH calculation model of gas-liquid two-phase flow with large density ratio is obtained: ; ; ; in, is the pressure of the particle, is the reference density, is the reference sound speed, is the adiabatic coefficient of the particle, is the density of the particle, is the background pressure, (This condition is used to satisfy the compressibility assumption), is the density change of the particle, is the maximum speed in the piston spraying scenario, is the maximum pressure in the piston oil injection scenario.

[0032] In the embodiments of the present application, generally, for liquid particles, The value is 7, and for gas particles, the γ value is 1.4.

[0033] S102. Establish a heat flux boundary heat transfer calculation model.

[0034] Specifically, the heat flux boundary heat transfer calculation model includes: Step 1: Calculate the surface recognition parameters of particles in the piston spray scene ; If the surface recognition parameters of particles in the piston spray scene If it is less than a preset value (e.g., 2.25), the i-th particle is a solid surface particle; Specifically, the surface recognition parameters of particles in the piston spraying scenario are calculated by the following formula: : ; in, is the surface particle identification parameter of the ith particle, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain.

[0035] Step 2: Calculate the temperature change caused by the heat flux input or output from the solid boundary based on the solid surface particles.

[0036] Specifically, the temperature change caused by the heat flux input or output from the solid boundary is calculated based on the solid surface particles using the following formula: ; ; ; in, For the The heat flux of a particle on a solid surface, The heat flux to or from a solid boundary, is the temperature change caused by the heat flux input or output to the solid boundary, For the The density of particles on a solid surface, is the specific heat capacity, For the The area of ​​the solid surface particles, For the The mass of particles on the solid surface, For the The Hamiltonian operator of a particle on a solid surface, For the The kernel function between the solid surface particles and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, For the The volume of particles on a solid surface.

[0037] In the embodiment of the present application, after the surface area is determined, the heat flux is defined by , we can get the formula for the temperature change caused by the heat flux input or output from the solid boundary. Among them, is the heat transfer coefficient (the amount of energy per unit area flowing into or out of a solid domain through a surface), is the temperature gradient of the particle, is the normal vector of the particle, The heat flux into or out of the boundary.

[0038] S103. Establish a calculation model for the pressure-type outlet boundary.

[0039] In the implementation mode of the present application, the calculation model of the pressure-type outlet boundary includes the establishment of the buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, the deletion of particle mechanisms, the continuity equation between similar fluids, the connection between density terms and pressure terms, the discretization of the momentum equation for the pressure gradient term, and the momentum equation for the velocity change. Among them, the continuity equation between similar fluids, the connection between density terms and pressure terms, the discretization of the momentum equation for the pressure gradient term, and the momentum equation for the velocity change in the calculation model of the pressure-type outlet boundary are established for the particles in the buffer area.

[0040] Here, in the calculation model of the pressure-type outlet boundary, the area pointed to by the positive normal of the pressure-type outlet boundary is the buffer area; the area pointed to by the opposite direction corresponding to the positive normal of the pressure-type outlet boundary is the internal area; the area extending from the pressure-type outlet boundary along the direction pointed by the corresponding positive normal is the preset distance. , get the particle adding and deleting layer; arrange seed points in the particle adding and deleting layer, and the spacing of the seed points is positively correlated with the size of the particles. Because it is related to the kernel function W, it is usually taken as 2 or 3. is the smooth length. Figure 2 Shown is a schematic structural diagram of a pressure-type outlet boundary provided in an embodiment of the present application.

[0041] Specifically, the continuity equation between similar fluids in the calculation model of the pressure-type outlet boundary, the connection between the density term and the pressure term, and the formula corresponding to the momentum equation for velocity change are the same as the continuity equation between similar fluids in the SPH calculation model of the large density ratio gas-liquid two-phase flow, the connection between the density term and the pressure term, and the momentum equation for velocity change; Specifically, the discretization of the pressure gradient term in the calculation model of the pressure-type outlet boundary is expressed by the following formula: ; in, It is the set pressure value at the pressure type outlet boundary.

[0042] Specifically, the calculation model of the pressure-type outlet boundary also includes a velocity correction formula to eliminate the influence of the tangential velocity: ; in, is the velocity vector calculated by the momentum equation for the velocity change at step n in the calculation model of the pressure outlet boundary, is the positive normal direction of the outlet boundary. is the corrected velocity vector.

[0043] Specifically, the particle deletion mechanism includes: Step 1: Calculate the position vector of the i-th particle Position vector with the center point of the pressure outlet boundary The difference between .

[0044] Specifically, the rotation matrix R is determined by the following steps: The rotation matrix for setting the pressure outlet boundary to rotate along the x-axis once is: , the rotation matrix for a single rotation along the y-axis is , the rotation matrix for a single rotation along the z-axis is ; ; ; ; ; in, is the rotation matrix of the pressure outlet boundary, is the rotation angle of the pressure outlet boundary.

[0045] Here, the above formula represents the rotation matrix It is the matrix multiplication of a series of single-degree-of-freedom rotation matrices. Since it involves specific operation steps and has no unified form, the subscript, number and corresponding angle of the right-hand rotation matrix are not indicated.

[0046] Step 2: Use the rotation matrix R and vector difference of the pressure outlet boundary , map the ith particle to the standard plane and obtain the position coordinates of the ith particle on the standard plane ( , , ).

[0047] Specifically, the rotation matrix R of the pressure outlet boundary, the vector difference , map the ith particle to the standard plane and obtain the position coordinates of the ith particle on the standard plane ( , , ),include: The rotation matrix R of the pressure outlet boundary and the vector difference Substitute the following formula to obtain the position coordinates of the i-th particle on the standard plane ( , , ); ; in, is the position coordinate vector of the ith particle after being mapped to the standard plane, is the unit vector of the x-axis of the local coordinate system on the standard plane, is the local coordinate system on the standard plane The unit vector of the axis, is the unit vector of the z-axis of the local coordinate system on the standard plane.

[0048] Step 3: According to the position coordinates on the standard plane ( , , ), determine the region where the i-th particle is located.

[0049] Specifically, according to the position coordinates on the standard plane ( , , ), determine the area where the i-th particle is located, including: Assume that the position z=0 is the position of the pressure outlet boundary, let S be the projection range of the shape of the pressure outlet boundary on the plane z=0, if , then the area where the i-th particle is located is the buffer area; among them, is the shape function determined by the shape of the pressure-type outlet boundary, It is used to measure the distance from the projection point of the ith particle on the plane z=0 to the outer contour of the pressure-type outlet boundary; if , then the area where the i-th particle is located is outside the particle addition and deletion layer; if the i-th particle is not in the buffer area and is not outside the particle addition and deletion layer, then the area where the i-th particle is located is the internal area.

[0050] Step 4: If the area where the i-th particle is located is outside the particle addition and deletion layer, delete the i-th particle.

[0051] Specifically, the particle generation mechanism includes: Step 1: Assign a virtual mass M to each seed point s, and the initial value of the virtual mass M of the seed point s is 0.

[0052] Step 2: Interpolate the flow field around the pressure outlet boundary through the density, volume and velocity of all particles at the pressure outlet boundary to obtain the velocity at the interpolation point I. and density .

[0053] Specifically, the density, volume and velocity of all particles at the pressure outlet boundary are interpolated to obtain the velocity at the interpolation point I: and density ,include: Substitute the density, volume and velocity of all particles at the pressure outlet boundary into the following formula to obtain the velocity at interpolation point I and density : ; in, , , is the velocity of the jth particle, is the density of the jth particle, is the kernel function between the interpolation point I and the jth particle, is the volume of the jth particle.

[0054] Step 3: According to the speed at the interpolation point I and density , the virtual mass of the seed point s at the current time step , generates the virtual mass of the seed point s at the next time step .

[0055] Specifically, according to the velocity at the interpolation point I and density , the virtual mass of the seed point s at the current time step , generates the virtual mass of the seed point s at the next time step ,include: The velocity at the interpolation point I and density , the virtual mass of the seed point s at the current time step Substitute into the following formula to obtain the virtual mass of the seed point s at the next time step: ; ; in, is the current time step, is the area of ​​the interpolation point, and Positively correlated, is the size of the particle, dim is the spatial dimension, is the time step.

[0056] Step 4: If , then the position information and flow field information of the new particle Q are generated according to the position information of the seed point s; where, for Round down, for Round down.

[0057] Specifically, the position information and flow field information of the new particle Q are generated according to the position information of the seed point s, including: Substitute the position information of the seed point s into the following formula to obtain the position information and flow field information of the new particle Q; ; in, is the position information of the new particle Q, is the location information of the seed point s, is the particle size, is the current time step, is the velocity of the new particle Q, is the velocity of interpolation point I, is the density of interpolation point I, is the temperature of interpolation point I, is the temperature of the new particle Q, is the density of the new particle Q, is the pressure of the new particle Q, is the state equation, and the flow field information of the new particle Q includes , , , .

[0058] S104. Numerical simulation of the piston oil injection cooling process is performed based on the SPH calculation model of large density ratio gas-liquid two-phase flow, the heat flux boundary heat transfer calculation model, and the pressure type outlet boundary calculation model.

[0059] In the implementation mode of the present application, the pressure outlet boundary position set by the numerical simulation user for the fluid calculation domain in the piston injection scenario, the solid geometric model of the piston (supporting formats such as stl, stp and obj) and the motion form (including speed setting and displacement setting) are obtained; based on the establishment process of the buffer area in the pressure outlet boundary, a buffer area is established in the fluid calculation domain of the solid geometric model; the fluid calculation domain is discretized into particles; at the initial moment, the particles in the internal area are searched from the discretized particles; and the target particles in the particles in the internal area are externally moved along the direction indicated by the positive normal of the pressure outlet boundary. The particles in the buffer area are obtained by pushing; the particles to be numerically simulated are generated at the pressure-type outlet boundary; the neighboring particles of each particle are searched and a linked list is established; the SPH calculation model of the large density ratio gas-liquid two-phase flow, the heat flux boundary heat transfer calculation model, and the calculation model of the pressure-type outlet boundary are called, and the time derivative term of the control equation of each particle is calculated based on the established linked list; the particles are leapfrog time-stepped and deleted according to the particle deletion mechanism; particles are generated according to the particle generation mechanism; if the current time is less than the end time of the numerical simulation, the process jumps to the generation of particles to be numerically simulated at the pressure-type outlet boundary and continues to execute.

[0060] Here, for list-type input, first determine the interval range to which the motion time t belongs and , and then use Lagrange interpolation to get the input value of the motion form: .

[0061] in, is the speed of step n, is the time of step n, is the time for step n+1, is the speed of step n+1, For the time range [ , ] within the interpolation speed.

[0062] Here, the mathematical form of leapfrog time stepping is as follows: ; .

[0063] Among them, the superscript represents the time step, the fraction represents the physical quantity of the intermediate time step, and the variable with subscript 0 represents the variable defined in the intermediate time step.

[0064] Based on the same inventive concept, an embodiment of the present application also provides a numerical simulation device for the piston oil spray cooling process corresponding to the numerical simulation method for the piston oil spray cooling process. Since the principle of solving the problem by the device in the embodiment of the present application is similar to the numerical simulation method for the piston oil spray cooling process in the embodiment of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0065] Reference Figure 3 FIG. 1 is a schematic diagram of a numerical simulation device for a piston oil spray cooling process provided by an embodiment of the present application, and the numerical simulation device for a piston oil spray cooling process includes: Establishing module 301, used for establishing a SPH calculation model for gas-liquid two-phase flow with a large density ratio; the continuity equation between similar fluids in the SPH calculation model for gas-liquid two-phase flow with a large density ratio adopts a simplified delta term smoothing pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model for gas-liquid two-phase flow with a large density ratio is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and background pressure term; The establishment module 301 is also used to establish a heat flux boundary heat transfer calculation model; The establishment module 301 is also used to establish a calculation model of the pressure-type outlet boundary, which includes the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the template of the generated particles; The numerical simulation module 302 is used to perform numerical simulation on the piston oil injection cooling process based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the pressure type outlet boundary calculation model.

[0066] In a possible implementation, the module 301 is established, specifically for establishing the continuity equation in the SPH calculation model of the gas-liquid two-phase flow with a large density ratio through the following steps: introducing a multiphase delta term to obtain the continuity equation in the SPH calculation model of the gas-liquid two-phase flow with a large density ratio: ; ;in, is the dissipation term of the density of the ith particle, is a constant, is the arithmetic mean of the smooth length of the i-th particle and the smooth length of the j-th particle searched in the computational domain, is the arithmetic mean of the sound velocity of the ith particle and the sound velocity of the jth particle searched in the computational domain, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, is the density of the ith particle, is the density of the jth particle searched in the computational domain, is the physical property relationship between the ith particle and the jth particle searched in the computational domain, is the physical property of the ith particle, is the physical property of the jth particle searched in the computational domain.

[0067] In a possible implementation manner, the momentum equation in the large density ratio gas-liquid two-phase flow SPH calculation model includes: The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is expressed by the following formula for the discretization of the pressure gradient term: ; in, is the pressure gradient term of the ith particle, is the pressure of the ith particle, is the first The pressure of a particle.

[0068] The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is expressed by the following formula for the velocity change: ; in, is the change in velocity of the ith particle caused by the artificial viscosity term, is a constant, is the velocity vector difference between the velocity vector of the i-th particle and the velocity vector of the j-th particle searched in the computational domain.

[0069] In a possible implementation, the module 301 is established, specifically for establishing the relationship between the density term and the pressure term in the SPH calculation model of the gas-liquid two-phase flow with a large density ratio through the following steps: introducing the Tait state equation EOS to obtain the relationship between the density term and the pressure term in the SPH calculation model of the gas-liquid two-phase flow with a large density ratio: ; ; ; in, is the pressure of the particle, is the reference density, is the reference sound speed, is the adiabatic coefficient of the particle, is the density of the particle, is the background pressure, , is the density change of the particle, is the maximum speed in the piston spraying scenario, is the maximum pressure in the piston oil injection scenario.

[0070] In a possible implementation, the module 301 is established to establish a heat flux boundary heat transfer calculation model by the following steps: calculating the surface identification parameters of particles in the piston spraying scene ; If the surface recognition parameters of particles in the piston spray scene If the value is less than a preset value, the ith particle is a solid surface particle; and the temperature change caused by the heat flux input or output from the solid boundary is calculated based on the solid surface particle.

[0071] In a possible implementation, a module 301 is established, which is specifically used to establish a calculation model of the pressure-type outlet boundary through the following steps, including: the area pointed to by the positive normal of the pressure-type outlet boundary is the buffer area; the area pointed to by the opposite direction corresponding to the positive normal of the pressure-type outlet boundary is the internal area; starting from the pressure-type outlet boundary, a preset distance is extended in the direction pointed by the corresponding positive normal. , a particle adding and deleting layer is obtained; seed points are arranged in the particle adding and deleting layer, and the spacing distance of the seed points is positively correlated with the size of the particles.

[0072] In a possible implementation, the establishment module 301 is specifically used to establish the particle deletion mechanism through the following steps, including: calculating the position vector of the i-th particle The position vector of the center point of the pressure profile outlet boundary The difference between ; Through the rotation matrix R of the pressure outlet boundary, the vector difference , map the i-th particle to the standard plane, and obtain the position coordinates of the i-th particle on the standard plane ( , , ); According to the position coordinates on the standard plane ( , , ), determine the area where the i-th particle is located; if the area where the i-th particle is located is outside the particle addition and deletion layer, delete the i-th particle.

[0073] In a possible implementation, the module 301 is established, specifically for establishing the particle generation mechanism through the following steps, including: assigning a virtual mass M to each seed point s, where the initial value of the virtual mass M of the seed point s is 0; interpolating the surrounding flow field of the pressure-type outlet boundary through the density, volume and velocity of all particles at the pressure-type outlet boundary to obtain the velocity at the interpolation point I. and density ; According to the speed at the interpolation point I and density , the virtual mass of the seed point s at the current time step , generates the virtual mass of the seed point s at the next time step ;like , then the position information and flow field information of the new particle Q are generated according to the position information of the seed point s; wherein, for Round down, for Round down.

[0074] The present application provides a numerical simulation device for piston oil injection cooling process, the device comprising: establishing a module 301, for establishing a SPH calculation model of a gas-liquid two-phase flow with a large density ratio; the continuity equation between similar fluids in the SPH calculation model of a gas-liquid two-phase flow with a large density ratio adopts a simplified delta term smoothing pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model of a gas-liquid two-phase flow with a large density ratio is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and the background pressure term; establishing The module 301 is established, and is also used to establish a heat flux boundary heat transfer calculation model; the module 301 is established, and is also used to establish a calculation model for a pressure-type outlet boundary, and the calculation model for the pressure-type outlet boundary includes the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the template of the generated particles; the numerical simulation module 302 is used to perform numerical simulation of the piston oil injection cooling process based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the pressure-type outlet boundary calculation model. Through this application, the weak compressibility assumption can be used to perform numerical simulation of the piston oil injection cooling process, reducing the amount of calculation for numerical simulation.

[0075] like Figure 4As shown, an electronic device 400 provided in an embodiment of the present application includes: a processor 401, a memory 402 and a bus, wherein the memory 402 stores machine-readable instructions executable by the processor 401. When the electronic device is running, the processor 401 communicates with the memory 402 through the bus, and the processor 401 executes the machine-readable instructions to perform the steps of the numerical simulation method of the piston oil injection cooling process as described above.

[0076] Specifically, the memory 402 and the processor 401 can be general-purpose memories and processors, which are not specifically limited here. When the processor 401 runs the computer program stored in the memory 402, it can execute the numerical simulation method of the piston oil injection cooling process.

[0077] Corresponding to the numerical simulation method of the above-mentioned piston oil spray cooling process, an embodiment of the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the numerical simulation method of the above-mentioned piston oil spray cooling process are executed.

[0078] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, the specific working process of the system and device described above can refer to the corresponding process in the method embodiment, and will not be repeated in this application. In the several embodiments provided in this application, it should be understood that the disclosed system, device and method can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0079] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0080] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0081] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the information processing method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard drives, ROM, RAM, magnetic disks, or optical disks.

[0082] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A numerical simulation method for piston oil spray cooling process, characterized in that: The method comprises: A SPH calculation model for gas-liquid two-phase flow with a large density ratio is established; the continuity equation between similar fluids in the SPH calculation model for gas-liquid two-phase flow with a large density ratio adopts a simplified delta term smoothing pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model for gas-liquid two-phase flow with a large density ratio is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and background pressure term; Establish a heat flux boundary heat transfer calculation model; Establishing a calculation model of a pressure-type outlet boundary, the calculation model of the pressure-type outlet boundary includes the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the template of the generated particles; The piston oil injection cooling process is numerically simulated based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the pressure-type outlet boundary calculation model.

2. The numerical simulation method for piston oil spray cooling process according to claim 1, characterized in that: The continuity equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is established by the following steps: By introducing the multiphase delta term, the continuity equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is obtained: ； ； in, is the dissipation term of the density of the ith particle, is a constant, is the arithmetic mean of the smooth length of the i-th particle and the smooth length of the j-th particle searched in the computational domain, is the arithmetic mean of the sound velocity of the ith particle and the sound velocity of the jth particle searched in the computational domain, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, is the density of the ith particle, is the density of the jth particle searched in the computational domain, is the physical property relationship between the ith particle and the jth particle searched in the computational domain, is the physical property of the ith particle, is the physical property of the jth particle searched in the computational domain.

3. The numerical simulation method for piston oil spray cooling process according to claim 2 is characterized in that: The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow includes: The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is expressed by the following formula for the discretization of the pressure gradient term: ； in, is the pressure gradient term of the ith particle, is the pressure of the ith particle, is the first The pressure of a particle; The momentum equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is expressed by the following formula for the velocity change: ； in, is the change in velocity of the ith particle caused by the artificial viscosity term, is a constant, is the velocity vector difference between the velocity vector of the i-th particle and the velocity vector of the j-th particle searched in the computational domain.

4. The numerical simulation method for piston oil spray cooling process according to claim 1, characterized in that: The connection between the density term and the pressure term in the SPH calculation model of the large density ratio gas-liquid two-phase flow is established through the following steps: The Tait equation of state EOS is introduced to obtain the relationship between the density term and the pressure term in the SPH calculation model of the large density ratio gas-liquid two-phase flow: ； ； ； in, is the pressure of the particle, is the reference density, is the reference sound speed, is the adiabatic coefficient of the particle, is the density of the particle, is the background pressure, , is the density change of the particle, is the maximum speed of the piston in the oil injection scenario, is the maximum pressure in the piston oil injection scenario.

5. The numerical simulation method for piston oil spray cooling process according to claim 1, characterized in that: The heat flux boundary heat transfer calculation model includes: Calculate the surface identification parameters of particles in the piston spray scene ; If the surface identification parameters of particles in the piston spray scene If it is less than the preset value, the i-th particle is a solid surface particle; The temperature change caused by the heat flux input or output from the solid boundary is calculated based on the solid surface particles.

6. The numerical simulation method for piston oil spray cooling process according to claim 1, characterized in that: The calculation model of the pressure-type outlet boundary includes: The area pointed to by the positive normal of the pressure-type outlet boundary is the buffer area; the area pointed to by the opposite direction corresponding to the positive normal of the pressure-type outlet boundary is the internal area; Extending a preset distance from the pressure outlet boundary in the direction pointed by the corresponding positive normal , a particle adding and deleting layer is obtained; seed points are arranged in the particle adding and deleting layer, and the spacing distance of the seed points is positively correlated with the size of the particles.

7. The numerical simulation method for piston oil spray cooling process according to claim 6, characterized in that: The particle deletion mechanism includes: Calculate the position vector of the i-th particle The position vector of the center point of the pressure profile outlet boundary The difference between ; The rotation matrix R of the pressure outlet boundary, the vector difference , map the i-th particle to the standard plane, and obtain the position coordinates of the i-th particle on the standard plane ( , , ); According to the position coordinates on the standard plane ( , , ), determine the area where the i-th particle is located; If the region where the i-th particle is located is outside the particle adding and deleting layer, the i-th particle is deleted.

8. The numerical simulation method for piston oil spray cooling process according to claim 6, characterized in that: The particle generation mechanism includes: Assign a virtual mass M to each seed point s, where the initial value of the virtual mass M of the seed point s is 0; The velocity at the interpolation point I is obtained by interpolating the flow field around the pressure-type outlet boundary through the density, volume and velocity of all particles at the pressure-type outlet boundary. and density ; According to the velocity at the interpolation point I and density , the virtual mass of the seed point s at the current time step , generates the virtual mass of the seed point s at the next time step ; like , then the position information and flow field information of the new particle Q are generated according to the position information of the seed point s; wherein, for Round down, for Round down.

9. A numerical simulation device for piston oil spray cooling process, characterized in that: The device comprises: Establishing a module for establishing a SPH calculation model for gas-liquid two-phase flow with a large density ratio; the continuity equation between similar fluids in the SPH calculation model for gas-liquid two-phase flow with a large density ratio adopts a simplified delta term smoothing pressure field; the momentum equation in the SPH calculation model introduces an artificial viscosity term; the connection between the density term and the pressure term in the SPH calculation model for gas-liquid two-phase flow with a large density ratio is explicitly established by adopting a weak compressibility assumption and introducing the Tait state equation and background pressure term; The establishment module is also used to establish a heat flux boundary heat transfer calculation model; The establishment module is further used to establish a calculation model of the pressure-type outlet boundary, wherein the calculation model of the pressure-type outlet boundary includes the establishment of a buffer area, the arrangement of seed points, the introduction and update of virtual mass, the generation of particle mechanisms, and the deletion of particle mechanisms; the seed points are used to characterize the template of the generated particles; The numerical simulation module is used to perform numerical simulation on the piston oil injection cooling process based on the large density ratio gas-liquid two-phase flow SPH calculation model, the heat flux boundary heat transfer calculation model, and the pressure type outlet boundary calculation model.

10. The numerical simulation device for piston oil spray cooling process according to claim 9, characterized in that: The establishment module is specifically used to establish the continuity equation in the large density ratio gas-liquid two-phase flow SPH calculation model through the following steps: By introducing the multiphase delta term, the continuity equation in the SPH calculation model of the large density ratio gas-liquid two-phase flow is obtained: ； ； in, is the dissipation term of the density of the ith particle, is a constant, is the arithmetic mean of the smooth length of the i-th particle and the smooth length of the j-th particle searched in the computational domain, is the arithmetic mean of the sound velocity of the ith particle and the sound velocity of the jth particle searched in the computational domain, is the distance vector difference between the i-th particle and the j-th particle searched in the computational domain, is the Hamiltonian operator of the ith particle, is the kernel function between the ith particle and the jth particle searched in the computational domain, is the volume of the jth particle searched in the computational domain, is the density of the ith particle, is the density of the jth particle searched in the computational domain, is the physical property relationship between the ith particle and the jth particle searched in the computational domain, is the physical property of the ith particle, is the physical property of the jth particle searched in the computational domain.

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