Modeling and design analysis method for electromagnetic direct drive air compressor

Abstract

The invention belongs to the related technical field of electromagnetic drive and air compression, and particularly relates to a modeling and design analysis method of an electromagnetic direct drive air compressor, which comprises the following steps: establishing a mathematical model of an electromagnetic direct drive air compressor system, the mathematical model at least comprising piston dynamics, actuator efficiency and a nonlinear gas pressure model; establishing a hydrodynamic model of the system, wherein the hydrodynamic model comprises a mass conservation equation, an energy conservation equation and a momentum conservation equation; a fluid-solid coupling model of the system exhaust process is established, and a fluid-solid coupling method is used for providing data reference for exhaust valve design; and designing and analyzing an exhaust valve of the electromagnetic direct-driven air compressor, and determining optimal valve parameters. By means of the method, the optimal design parameters of the compressor under various working conditions can be determined, the efficiency and stability of the compressor are improved, and powerful support is provided for design of the electromagnetic direct-drive air compressor.

Description

Technical Field

[0001] The present invention mainly relates to the technical field related to electromagnetic drive and air compression, and specifically provides a modeling and design analysis method for an electromagnetic direct drive air compressor. Background Art

[0002] With economic development and rising living standards, people are demanding ever-higher levels of comfort and luxury in their vehicles. Meanwhile, the development of highways is placing higher demands on vehicle handling, stability, and safety. Electronic air suspension significantly impacts a vehicle's ride comfort and handling stability, but key technologies are largely controlled by foreign companies. Researching and mastering the core technologies of air suspension systems is of strategic importance for advancing technological advancements.

[0003] Rotary reciprocating air compressors are widely used, but they have problems such as complex structure, high vibration and noise, and large mechanical losses. Scholars have improved the efficiency of compressors by improving the valve and crank-connecting rod mechanism, but these solutions cannot overcome the inherent shortcomings. Since the advent of linear motors in the 1950s, direct-drive compressors have been proposed, providing higher transmission efficiency and smaller size, making them suitable for low-power, variable air volume scenarios. The electromagnetic direct-drive compressor proposed in this application uses a moving coil electromagnetic linear actuator with high power density and high response characteristics, which can improve the performance of the vehicle's active suspension system and has theoretical and engineering value.

[0004] In the research on electromagnetic direct-drive compressors, these compressors, which are directly driven by linear actuators, were originally used in space exploration. Composed of a piston, a resonant spring, and a linear motor, domestic and foreign scholars have promoted its transition from military to civilian use by optimizing its dynamic characteristic parameters. Foreign research is mainly concentrated in companies such as Sunpower and Panasonic, which have commercialized direct-drive compressors and applied them to refrigerators, significantly improving energy efficiency. Domestic research is mainly carried out by universities and research institutions, covering the structural modeling, dynamic analysis, and prototype testing of compressors, but further in-depth and breadth are needed. Studies have shown that electromagnetic efficiency is closely related to factors such as mechanical damping and resonant frequency.

[0005] Compressor fluid simulation research involves analyzing the compressor's internal flow field, which has a significant impact on the compressor's reliability and economy. Researchers at home and abroad use mathematical models and computational fluid dynamics (CFD) software to simulate pressure changes and valve disc motion characteristics during compressor operation. Domestic research mainly includes stress analysis of the compressor cylinder and piston and optimization of pulsation suppression devices. In contrast, international scholars have used fluid-structure coupling models to analyze the impact of the Bernoulli effect on intake valve dynamics. However, current research mainly focuses on steady-state calculations, with less research on the interaction between the intake valve and the internal flow field of the cylinder. Summary of the Invention

[0006] To address the shortcomings of current technology, the present invention combines existing technologies and, based on practical applications, provides a modeling and design analysis method for an electromagnetic direct-drive air compressor. This method can determine the optimal design parameters of the compressor under various operating conditions, improve the efficiency and stability of the compressor, and provide strong support for the design of electromagnetic direct-drive air compressors.

[0007] The technical solutions of the present invention are as follows:

[0008] A modeling and design analysis method for an electromagnetic direct drive air compressor includes the following steps:

[0009] S1. Establish a mathematical model of the electromagnetic direct-drive air compressor system, which at least includes piston dynamics, actuator efficiency, and nonlinear gas pressure models;

[0010] S2. Establish a fluid dynamics model of the system, which includes the mass conservation equation, energy conservation equation, and momentum conservation equation;

[0011] S3. Establish a fluid-structure coupling model for the exhaust process of the system and use the fluid-structure coupling method to provide data reference for exhaust valve design;

[0012] S4. Design and analyze the exhaust valve of the electromagnetic direct-drive air compressor and determine the optimal valve parameters.

[0013] Furthermore, in step S1, when the nonlinear gas pressure model is established, the gas state in the cylinder is simplified as follows:

[0014] (1) Treating the intake and exhaust valves as ideal valves, that is, ignoring the pressure fluctuations during the intake and exhaust process, compression, and leakage factors during the exhaust process, and assuming that the pressure during the intake and exhaust process is constant;

[0015] (2) During the operation of the compressor, the heat exchange between the gas in the cylinder and the outside world is ignored;

[0016] (3) There is no leakage during the compression, exhaust and expansion stages.

[0017] Furthermore, in step S1, the piston dynamics model expression is established as follows:

[0018]

[0019] Where u(t) is the input voltage, i is the current, and L e is the inductance, R e is the resistance, k emf is the back electromotive force, k mis the spring stiffness of the mechanical system, c is the damping of the mechanical system, m is the mass of the piston, x is the piston displacement, F g is the gas pressure, F e is the electromagnetic force;

[0020] The actuator efficiency model expression is as follows:

[0021]

[0022] Where n is the actuator efficiency, P out is the output power of the linear actuator, P in is the input work of the linear actuator, v is the piston speed;

[0023] The nonlinear gas pressure change goes through four processes: intake process, compression process, exhaust process and expansion process. The piecewise function expression of the model is as follows:

[0024]

[0025] Where A is the piston area, P s is the intake cylinder pressure, P d is the exhaust cylinder pressure, δ s , δ d are the relative intake and exhaust pressure losses, respectively, and their values ​​are selected according to the intake and exhaust pressures. V(t) is the cylinder volume, V0 is the total cylinder volume, and K is the isentropic coefficient with a value of 1.4.

[0026] Furthermore, in step S3, the fluid-solid coupling model is established as follows:

[0027] Use 3D software to create a 3D model of the fluid area of ​​the air compressor cylinder. After building the model in the 3D software, import it into the Fluent unit of ANSYS and then import it into Geometry.

[0028] Dynamic mesh technology is used in the calculation process. Hexahedral mesh is used to simulate the in-cylinder fluid flow to generate a structural mesh with regular spacing and consistent arrangement. For the complex model of the exhaust reed valve and exhaust chamber, tetrahedral mesh is used for segmentation.

[0029] After the meshing is completed, the boundaries of the fluid should be defined, transient cylinder motion should be selected, the gas should be set to ideal gas, the pressure implicit PISO algorithm should be selected, the fluid material should be set to air, the gas density should be set to ideal gas, the fluid model should use the standard K-Epsilon turbulence model, the wall should be set to adiabatic without slip, and the inlet and outlet boundaries of the compressor should be defined.

[0030] Further, step S4 specifically includes:

[0031] By simulating the pressure and velocity fields at different time points, the key areas where airflow affects the valve disc are analyzed and identified, and how these areas affect the valve disc movement and overall pressure distribution are determined. Subsequently, parametric simulations are performed on different valve thicknesses and widths to compare their effects on pressure loss and valve lift, and to determine the optimal design that balances valve performance and durability.

[0032] Furthermore, step S4 further includes:

[0033] Simulations were performed under loaded and no-load conditions to evaluate the impact of changes in exhaust pressure on valve dynamics, revealing the deformation characteristics of the valve disc under different pressures and providing data support for the optimization of electromagnetic direct-drive air compressors under actual operating conditions.

[0034] Beneficial effects of the present invention:

[0035] The modeling and analysis method provided by this invention enables in-depth simulation and analysis of the air compressor exhaust process. This method not only shortens the design cycle but also provides precise theoretical support for key design parameters such as valve plate thickness and cross-sectional width, significantly improving the efficiency and stability of the compressor. This method fills a gap in existing technology, providing valuable data and technical references for researchers in related fields, and contributing to the advancement and application of air compressor technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the schematic diagram of the electromagnetic direct drive compressor.

[0037] Figure 2 Schematic diagram of cylindrical grid.

[0038] Figure 3 This is the fluid-solid coupling model diagram of the cylinder working process.

[0039] Figure 4 This is a comparison chart of valve lift under two thicknesses.

[0040] Figure 5 This is a comparison chart of pressure loss under two thicknesses. DETAILED DESCRIPTION

[0041] The present invention will be further described with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the present application.

[0042] This embodiment provides a modeling and analysis method for an electromagnetic direct-drive air compressor. The electromagnetic direct-drive air compressor system is mainly composed of an electromagnetic linear actuator, a piston, a cylinder, an intake and exhaust valve group, etc. Its specific structure is as follows Figure 1 As shown, it includes: a cylinder 1, a piston 2, an air inlet check valve 3, an air outlet check valve 4, a sealing ring 10, a spring 5, a coil 6, an inner magnetic yoke 7, a permanent magnet 8, a coil skeleton 9, etc.

[0043] The modeling and analysis methods of electromagnetic direct-drive air compressors are mainly as follows:

[0044] Step 1: Establish a mathematical model of the electromagnetic direct-drive air compressor system, including the piston, actuator, and nonlinear gas pressure model, and dynamically design and optimize the compression parameters.

[0045] The piston dynamics model is as follows:

[0046]

[0047] Where u(t) is the input voltage, i is the current, and L e is the inductance, R e is the resistance, k emf is the back electromotive force, k m is the spring stiffness of the mechanical system, c is the damping of the mechanical system, m is the mass of the piston, x is the piston displacement, F e is the electromagnetic force, F g is the gas force, F g =PA, A is the piston area, P is the cylinder pressure.

[0048] The efficiency of a linear actuator is expressed as follows:

[0049]

[0050] Where, P out is the output power of the linear actuator, P in is the input work of the linear actuator, and v is the piston speed.

[0051] The reciprocating inertia force of the piston motion is the force generated when the moving mass moves, which can be expressed as:

[0052]

[0053] Cylinder model:

[0054] The gas state in the cylinder is simplified as follows:

[0055] (1) Treating the intake and exhaust valves as ideal valves, ignoring a series of complex factors such as pressure fluctuations during the intake and exhaust process, compression and leakage during the exhaust process, and assuming that the pressure during the intake and exhaust process is constant;

[0056] (2) The compression and expansion process is an isentropic process, that is, during the operation of the compressor, the heat exchange between the gas in the cylinder and the outside world is ignored;

[0057] (3) There is no leakage during the compression, exhaust and expansion stages.

[0058] According to the above assumptions, the pressure change in the cylinder goes through four processes: intake process, compression process, exhaust process and expansion process. The piecewise function expression of the obtained gas force is:

[0059]

[0060] Where, P s is the intake cylinder pressure, P d is the exhaust cylinder pressure, δ s , δ d are the relative intake and exhaust pressure losses, respectively, and their values ​​are selected according to the intake and exhaust pressures. V(t) is the cylinder volume, V0 is the total cylinder volume, and K is the isentropic coefficient with a value of 1.4.

[0061] Step 2: Establish a fluid dynamics model of the system to solve the fluid movement problem.

[0062] The basic conservation laws of fluid mechanics include the mass conservation equation, the energy conservation equation, and the momentum conservation equation.

[0063]

[0064] Continuity equation

[0065]

[0066] Where ρ represents density, x, y, and z are the three coordinate axes of the Cartesian coordinate system, u, v, and w are the components of the fluid velocity vector in the x, y, and z coordinate axes; and t represents time.

[0067] Energy conservation equation:

[0068]

[0069] Among them, c p is the specific heat capacity, T is the thermodynamic temperature, k is the heat transfer coefficient, S t is the viscous dissipation.

[0070] Momentum conservation equation:

[0071]

[0072] Where P is pressure, u is velocity vector, u=(u,v,w),τ ij, (i, j = x, y, z) is the viscous stress component generated by molecular viscosity, F i , (i=x,y,z) is the force on the microscopic gas.

[0073] Table 1 below is an example of some parameters of electromagnetic direct-drive air compressors.

[0074] Table 1 Main parameters

[0075]

[0076] Step 3: Establish a fluid-structure coupling model of the exhaust process and use the fluid-structure coupling method to provide a theoretical reference for exhaust valve design.

[0077] Using CATIA, a 3D model of the fluid area of ​​the air compressor cylinder was directly established. After the model was established in the 3D software, it was imported into the Fluent unit of ANSYS and then into Geometry. The preliminary established two-way fluid-solid coupling model is as follows: Figure 2 shown.

[0078] Considering that the fluid domain of the gas movement within the cylinder constantly changes with the rotation of the crankshaft, dynamic meshing technology was employed during the calculation process. Dynamic meshing technology requires precise meshing requirements; otherwise, errors may occur or the calculation results may be unsatisfactory. Therefore, the quality of the mesh for variable volume areas is superior to that for fixed volume areas. Considering the advantages of using both tetrahedral and hexahedral meshes, a hexahedral mesh was selected for the in-cylinder fluid simulation to obtain a structured mesh with regular spacing and consistent arrangement. By reconstructing the hexahedral mesh, the changing process of the fluid domain can be effectively simulated, which improves convergence speed and shortens calculation time. Due to the complexity of the exhaust reed valve and exhaust chamber models, tetrahedral meshing was used for segmentation.

[0079] Given the significant variations in gas flow through the valve gap, a separate region and smaller mesh size are required. Unstructured meshing is used for the complex disc structure, while structured meshing is used at the inlet and outlet, where gas state variations are less pronounced, to reduce computational complexity. To minimize data transmission errors at the interface, meshes between different regions use common nodes.

[0080] After the meshing is completed, the boundaries of the fluid should be defined. The accuracy of the boundary definition is the key to improving the accuracy of the simulation results. Once the cylindrical flow field model is meshed, it is imported into the setup module. Select transient cylinder motion and set the gas to ideal gas. The fluid motion in the cylinder is an unsteady compressible flow. Select the pressure implicit PISO algorithm, set the fluid material to air, and set the gas density to ideal gas. The fluid model uses the standard K-Epsilon turbulence model, and the wall is set to adiabatic no-slip. The inlet and outlet boundaries of the compressor are defined. The outlet is designated as a pressure outlet, and the pressure outlet is 1500KPa. The figure shows the boundary condition settings

[0081] In order to accurately simulate the instantaneous changes in the air flow in the air compressor and obtain a motion state consistent with the actual conditions, the flow field needs to be included in the dynamic grid. In this way, the fluid model and the grid model can be adjusted according to the changes in the flow field. Fluent provides three types of dynamic grid calculations: spring-based smoothing, dynamic layering, and local grid re-division. The upward movement of the piston is achieved through a stacked model, and the movement of the valve disc is achieved through local redrawing and elastic approximate smooth models. The motion surface type is defined as rigid body motion, and its motion is characterized by its contour. The motion grid of the FSI wall is coupled to the system, and the grid thickness of the two motion grids is set to 0.6mm and 0.3mm respectively. The grid division is as follows Figure 3 shown.

[0082] By simulating the pressure and velocity fields at different time points, the team analyzed and identified the key areas where airflow impacts the valve disc, revealing how these areas influence valve disc motion and overall pressure distribution. This provided a basis for optimal valve design. Subsequently, parametric simulations of different valve thicknesses and widths were performed to compare their effects on pressure loss and valve lift, identifying the optimal design that balances valve performance and durability. Furthermore, simulations under loaded and no-load conditions evaluated the impact of changes in exhaust pressure on valve dynamics, revealing the deformation characteristics of the valve disc under different pressures. This process laid the theoretical foundation for optimizing electromagnetic direct-drive air compressors under actual operating conditions.

[0083] like Figure 4 and Figure 5 As shown, simulation results provide important insights into the exhaust process of electromagnetic direct-drive compressors. Analysis of the pressure and velocity fields reveals that the high-pressure region significantly impacts the reed valve, affecting valve lift and the pressure distribution within the exhaust chamber. These findings emphasize the need for careful valve disc design to effectively handle dynamic pressure variations.

[0084] At an exhaust pressure of 0.7 MPa, both the relative pressure loss and valve plate displacement reach their maximum values. As exhaust pressure increases, the maximum valve lift and relative pressure loss first increase and then decrease. It is noteworthy that the curves for an exhaust pressure of 0.1 MPa differ significantly from those under other conditions. At an exhaust pressure of 0.1 MPa, the relative pressure loss and valve lift curves exhibit stable changes, primarily varying with the intake manifold gas mass flow curve. Under other operating conditions, both relative pressure loss and valve lift fluctuate during the exhaust process, with the relative pressure loss oscillation being more pronounced.

[0085] Simulation results at different exhaust pressures show that pressure conditions significantly affect valve performance. Under high load conditions, valve disc deformation is more pronounced, leading to increased pressure loss and potential backflow issues. Conversely, under no-load conditions, valve disc blockage is reduced, demonstrating improved efficiency.

[0086] Overall, these analyses guided the design of electromagnetic direct-drive compressors, achieving a balance between performance and efficiency by specifying the optimal valve thickness and width to ensure reliable operation under varying load conditions.

Claims

1. A modeling and design analysis method for an electromagnetic direct drive air compressor, characterized in that: The steps include: S1. Establish a mathematical model of the electromagnetic direct-drive air compressor system, which at least includes piston dynamics, actuator efficiency, and nonlinear gas pressure models; S2. Establish a fluid dynamics model of the system, which includes the mass conservation equation, energy conservation equation, and momentum conservation equation; S3. Establish a fluid-structure coupling model for the exhaust process of the system and use the fluid-structure coupling method to provide data reference for exhaust valve design; S4. Design and analyze the exhaust valve of the electromagnetic direct-drive air compressor and determine the optimal valve parameters.

2. The modeling and design analysis method of the electromagnetic direct drive air compressor according to claim 1, characterized in that: In step S1, when the nonlinear gas pressure model is established, the gas state in the cylinder is simplified as follows: (1) Treating the intake and exhaust valves as ideal valves, that is, ignoring the pressure fluctuations during the intake and exhaust process, compression, and leakage factors during the exhaust process, and assuming that the pressure during the intake and exhaust process is constant; (2) During the operation of the compressor, the heat exchange between the gas in the cylinder and the outside world is ignored; (3) There is no leakage during the compression, exhaust and expansion stages.

3. The modeling and design analysis method of the electromagnetic direct drive air compressor according to claim 2, characterized in that: In step S1, the piston dynamics model expression is established as follows: Where u(t) is the input voltage, i is the current, and L e is the inductance, R e is the resistance, k emf is the back electromotive force, k m is the spring stiffness of the mechanical system, c is the damping of the mechanical system, m is the mass of the piston, x is the piston displacement, F g is the gas pressure, F e is the electromagnetic force; The actuator efficiency model expression is as follows: Where n is the actuator efficiency, P out is the output power of the linear actuator, P in is the input work of the linear actuator, v is the piston speed; The nonlinear gas pressure change goes through four processes: intake process, compression process, exhaust process and expansion process. The piecewise function expression of the model is as follows: Where A is the piston area, P s is the intake cylinder pressure, P d is the exhaust cylinder pressure, δ s , δ d are the relative intake and exhaust pressure losses, respectively, and their values ​​are selected according to the intake and exhaust pressures, V(t) is the cylinder volume, V0 is the total cylinder volume, K is the isentropic coefficient and its value is 1.

4.

4. The modeling and design analysis method for an electromagnetic direct drive air compressor according to claim 1, characterized in that: In step S3, the fluid-solid coupling model is established as follows: Use 3D software to create a 3D model of the fluid area of ​​the air compressor cylinder. After building the model in the 3D software, import it into the Fluent unit of ANSYS and then import it into Geometry. Dynamic mesh technology is used in the calculation process. Hexahedral mesh is used to simulate the in-cylinder fluid flow to generate a structural mesh with regular spacing and consistent arrangement. For the complex model of the exhaust reed valve and exhaust chamber, tetrahedral mesh is used for segmentation. After the meshing is completed, the boundaries of the fluid should be defined, transient cylinder motion should be selected, the gas should be set to ideal gas, the pressure implicit PISO algorithm should be selected, the fluid material should be set to air, the gas density should be set to ideal gas, the fluid model should use the standard K-Epsilon turbulence model, the wall should be set to adiabatic without slip, and the inlet and outlet boundaries of the compressor should be defined.

5. The modeling and design analysis method for an electromagnetic direct drive air compressor according to claim 4, characterized in that: Step S4 specifically includes: By simulating the pressure and velocity fields at different time points, the key areas where airflow affects the valve disc are analyzed and identified, and how these areas affect the valve disc movement and overall pressure distribution are determined. Subsequently, parametric simulations are performed on different valve thicknesses and widths to compare their effects on pressure loss and valve lift, and to determine the optimal design that balances valve performance and durability.

6. The modeling and design analysis method for an electromagnetic direct drive air compressor according to claim 5, characterized in that: Step S4 further includes: Simulations were performed under loaded and no-load conditions to evaluate the impact of changes in exhaust pressure on valve dynamics, revealing the deformation characteristics of the valve disc under different pressures and providing data support for the optimization of electromagnetic direct-drive air compressors under actual operating conditions.

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