Active control method for air type cavitation of fuel pump

Abstract

The invention discloses an active control method for air type cavitation of a fuel pump, belongs to the technical field of fuel pumps, and solves the problem that the flow pressure is suddenly reduced due to the air type cavitation phenomenon when the fuel pump conveys gas-containing fuel in a high-altitude environment. When three-dimensional models of an impeller, a volute and the like of the fuel pump are designed, a flow increasing design method is adopted, an exhaust channel is formed in an oil outlet pipeline of the volute, and air type cavitation bubbles generated in the impeller and the volute are taken away by actively sacrificing part of medium energy, so that the problem of sudden pressure drop caused by the air type cavitation phenomenon of the fuel pump is solved. And in order to avoid large pressure loss caused by the overlarge diameter of the exhaust channel, it is guaranteed that the aircraft fuel requirement is met while gas is exhausted in the mode of gradually increasing the exhaust channel and the rated flow, and the pressure loss is reduced to the maximum extent.

Description

Technical Field

[0001] The invention relates to the technical field of fuel pumps, and in particular to an active control method for air-type cavitation of a fuel pump. Background Art

[0002] Fuel pumps are widely used in aviation aircraft fuel systems, and their cavitation performance in high-altitude environments is related to the reliability and stability of platform operation. The gas content of RP-3 jet fuel is 6% to 14% at normal temperature and pressure. Due to the particularity of the conveying medium, air bubbles precipitate when the fuel pump is running at high altitude. This phenomenon is air-type cavitation. In air-type cavitation, the development, change and movement of air bubbles in the impeller channel of the fuel pump lead to dynamic phenomena such as separation of air and jet fuel, bubble breakage and coalescence. When bubbles accumulate to a certain extent in the suction chamber, impeller and other flow-through parts, forming air masses or air pockets, it will have a significant impact on the pump's head, flow rate, efficiency, etc., resulting in a decrease in the performance of the pump.

[0003] Existing methods for controlling the occurrence and development of cavitation often include active and passive methods. The active method mostly uses blade slits. For example, the patent with application number 201910919236.8 discloses a method for improving the anti-cavitation performance of the impeller. An inducer is installed in front of the first-stage impeller of the pump, and a long blade with a gap is fixed around the impeller with an Archimedean spiral, and a gradually increasing gap of 1mm to 2mm is opened at a distance from the head of the long blade. The angle between the direction of the gap and the flow direction is an acute angle. Although the anti-cavitation ability is improved, an inducer needs to be installed additionally, and the structure is complicated. The passive method is to modify the impeller inlet parameters, but because efficiency and cavitation cannot be achieved at the same time, in general, changing the blade inlet parameters can improve the anti-cavitation performance, but it will sacrifice higher efficiency. Summary of the invention

[0004] In view of the above problems in the prior art, the present invention provides a method for actively controlling air cavitation in a fuel pump, which solves the problem of sudden drop in flow pressure due to air cavitation when the fuel pump transports gas-containing fuel in a high-altitude environment.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for actively controlling air-type cavitation in a fuel pump is provided, comprising the steps of:

[0007] S1. Determine the performance parameters of the fuel pump according to the altitude and fuel demand of the aircraft. The performance parameters include the rated flow rate Q q , rated boost pressure ΔP, speed n and cavitation margin NPSH;

[0008] S2. Calculate the hydraulic parameters of the impeller and volute in the fuel pump according to the performance parameters of the fuel pump;

[0009] S3, establishing a three-dimensional model of the connection between the impeller and the volute according to the hydraulic parameters of the impeller and the volute, and modeling an exhaust pipe for communicating with the fuel tank on the volute oil outlet pipeline of the three-dimensional model;

[0010] S4, performing numerical simulation on the three-dimensional model, and continuously increasing the diameter of the exhaust pipe within a set threshold range of the exhaust pipe diameter, to obtain a boost value P at a rated flow rate for different exhaust pipe diameters;

[0011] S5, determine whether there is a boost value P greater than or equal to the rated boost ΔP, if so, proceed to step S6, otherwise increase the rated flow Q in the performance parameters of the fuel pump q And return to step S2;

[0012] S6. Obtain the exhaust pipe diameter corresponding to the boost value P, and process the fuel pump according to the minimum diameter of the exhaust pipe and the parameters of the three-dimensional model.

[0013] The working principle of this scheme is that when designing the three-dimensional model of the fuel pump impeller, volute, etc., the flow rate design method is adopted, and an exhaust channel is set on the volute oil outlet pipeline, and the air-type cavitation generated in the impeller and volute is taken away by actively sacrificing part of the medium energy, thereby improving the pressure drop problem caused by the air-type cavitation phenomenon in the fuel pump. In order to avoid a large pressure loss caused by an excessively large diameter of the exhaust channel, this scheme minimizes the pressure loss by gradually increasing the exhaust pipe and the rated flow rate to ensure that the gas is discharged while meeting the aviation fuel demand.

[0014] Furthermore, the exhaust pipe in the three-dimensional model is vertically connected to the volute oil outlet pipeline. The vertical setting of the exhaust pipe helps to improve the exhaust efficiency, ensure the effective discharge of gas in the fuel pump system, and further inhibit cavitation.

[0015] Furthermore, the range of the setting threshold d of the exhaust pipe diameter is: when the rated flow Q q ≤1500L / H, d=3~5mm; when rated flow Q q When >1500L / H, d=5~10mm.

[0016] Furthermore, the method for numerical simulation of the three-dimensional model is:

[0017] S4.1. Perform preliminary meshing of the three-dimensional model using CFD software;

[0018] S4.2, setting a turbulence model in the flow channel within the three-dimensional model;

[0019] S4.2, setting the boundary conditions of the three-dimensional model, and using JAT A Liquid to solve the single-phase flow, and obtaining the test boost value of the three-dimensional model;

[0020] S4.3, increasing the mesh density of the three-dimensional model and obtaining the test boost value of the three-dimensional model again;

[0021] S4.4, compare whether the change of the two test boost values ​​is less than 5%, if so, go to step S4.5, otherwise return to step S4.2. Step S4.4 is used to check the independence of mesh quality, so that the simulation results are no longer significantly dependent on the refinement of the mesh, ensuring the reliability of the simulation results.

[0022] S4.5. Use CFD software to simulate a three-dimensional model to simulate multiple outlet flow conditions and obtain the boost values ​​of the corresponding flow conditions, and draw a flow boost curve;

[0023] S4.6. Obtain the boost value at rated flow rate through the flow boost curve.

[0024] Furthermore, the turbulence model is the RGN k-ε turbulence model or the SST k-ω turbulence model. Both the RGN k-ε model and the SST k-ω turbulence model are based on the RANS equations. Both are suitable for steady flow simulation and are specifically used for steady-state flow problems. By solving the transport equations of turbulent kinetic energy k and dissipation rate ε, the turbulent viscosity coefficient is provided for the steady flow, thereby simulating the influence of turbulence on the steady flow. The SST k-ω turbulence model has a better simulation effect for near-wall areas and complex flows.

[0025] Furthermore, the setting of boundary conditions includes setting the boundary condition of the volute inlet as a pressure inlet, and taking the total pressure of the known fluid when entering the volute as an input parameter. By specifying the inlet pressure, the solver can calculate the flow characteristics entering the system according to the fluid dynamics equation. The boundary condition of the volute outlet is the mass flow rate. By specifying the mass flow rate, the solver can calculate the appropriate flow velocity and pressure according to the internal flow field conditions. The boundary condition of the exhaust duct outlet is the pressure outlet, and the pressure of the exhaust duct is set to be equal to the pressure of the volute inlet to ensure the physical consistency of the system. The solid wall of the volute adopts a no-slip wall. The no-slip wall condition is used to make the velocity of the fluid on the wall the same as the wall velocity, which can effectively simulate the interaction between the fluid and the solid surface and capture the formation and development of the boundary layer. The telescopic wall function method is used in the near-wall area. The telescopic wall function method is a way to approximate the turbulent flow near the wall. It describes the velocity distribution near the wall through empirical formulas or functions, thereby avoiding the use of too fine grids near the wall. It can automatically adjust according to the density of the grid to ensure the stability and accuracy of the calculation results. The frozen rotor method is used for the dynamic and static interface between the impeller and the volute. The frozen rotor method is a simplified method for dealing with the interface between the dynamic and static parts of rotating machinery. It assumes that the relative position between the impeller and the volute is fixed during the calculation process, thereby approximating a dynamic problem as a steady-state problem. This method greatly simplifies the calculation and can provide more accurate results when the speed is relatively stable.

[0026] Furthermore, the convergence accuracy of JAT ALiquid in solving the residual error is 10 -5 . High-precision convergence requirements ensure the stability and reliability of numerical simulation results and reduce errors and uncertainties.

[0027] Furthermore, the flow rates of the multiple outlet flow conditions include at least 0 times, 0.2 times, 0.4 times, 0.6 times, 0.8 times, 1.0 times and 1.2 times the rated flow rate. By simulating multiple flow conditions, it is ensured that the design can maintain good performance under different working conditions, thereby improving the robustness and adaptability of the design.

[0028] Furthermore, the hydraulic parameters of the impeller include the impeller inlet diameter, the impeller outlet diameter, the impeller outlet width, the number of blades, the blade wrap angle, the blade inlet placement angle, and the blade inlet placement angle. The above hydraulic parameter settings ensure the refinement and optimization of the impeller design and improve the overall performance and efficiency of the fuel pump.

[0029] The present invention discloses a method for actively controlling air-type cavitation in a fuel pump, which has the following beneficial effects:

[0030] The present invention adopts the flow-increasing design method when designing the three-dimensional model of the fuel pump impeller, volute, etc., and sets an exhaust channel on the volute oil outlet pipeline, and takes away the air-type cavitation generated in the impeller and volute by actively sacrificing part of the medium energy, thereby improving the pressure drop problem caused by the air-type cavitation phenomenon in the fuel pump. In order to avoid the large pressure loss caused by the large diameter of the exhaust channel, this solution ensures the discharge of gas while meeting the aviation fuel demand by gradually increasing the exhaust pipeline and the rated flow, thereby maximizing the reduction of pressure loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the active control method of air-type cavitation in a fuel pump;

[0032] Figure 2 is a schematic diagram of the structure of a fuel pump;

[0033] Figure 3 This is the flow rate pressure curve. DETAILED DESCRIPTION

[0034] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0035] Example 1

[0036] refer to Figure 1 This embodiment provides a method for actively controlling air-type cavitation in a fuel pump, comprising the steps of:

[0037] S1. Determine the performance parameters of the fuel pump according to the altitude and fuel demand of the aircraft. The performance parameters include the rated flow rate Q q , rated boost pressure ΔP, speed n and cavitation margin NPSH.

[0038] S2. Calculate the hydraulic parameters of the impeller and volute in the fuel pump based on the performance parameters of the fuel pump. The hydraulic parameters of the impeller include the impeller inlet diameter, impeller outlet diameter, impeller outlet width, number of blades, blade wrap angle, blade inlet placement angle, and blade inlet placement angle. The above hydraulic parameter settings ensure the refinement and optimization of the impeller design and improve the overall performance and efficiency of the fuel pump.

[0039] S3. A three-dimensional model of the connection between the impeller and the volute is established through the hydraulic parameters of the impeller and the volute, and an exhaust pipe for connecting to the fuel tank is modeled on the volute oil outlet pipeline of the three-dimensional model. The exhaust pipe in the three-dimensional model is vertically connected to the volute oil outlet pipeline. The vertical setting of the exhaust pipe helps to improve the exhaust efficiency, ensure the effective discharge of gas in the fuel pump system, and further suppress cavitation.

[0040] S4. Perform numerical simulation on the three-dimensional model, and continuously increase the diameter of the exhaust pipe within the set threshold range of the exhaust pipe diameter to obtain the boost value P of different exhaust pipe diameters at the rated flow rate. The range of the set threshold d of the exhaust pipe diameter is: when the rated flow rate Q q ≤1500L / H, d=3~5mm; when rated flow Q q When >1500L / H, d=5~10mm.

[0041] S5, determine whether the boost value P is greater than or equal to the rated boost ΔP, if so, proceed to step S6, otherwise increase the rated flow Q in the performance parameters of the fuel pump q And return to step S2.

[0042] S6. Obtain the exhaust pipe diameter corresponding to the boost value P, and process the fuel pump according to the minimum diameter of the exhaust pipe and the parameters of the three-dimensional model.

[0043] In this embodiment, when designing the three-dimensional model of the fuel pump impeller, volute, etc., the flow rate design method is adopted, and an exhaust channel is set on the volute oil outlet pipeline, and the air-type cavitation generated in the impeller and volute is taken away by actively sacrificing part of the medium energy, thereby improving the pressure drop problem caused by the air-type cavitation phenomenon in the fuel pump. In order to avoid a large pressure loss caused by an excessively large diameter of the exhaust channel, this solution ensures that the gas is discharged while meeting the aviation fuel demand by gradually increasing the exhaust pipeline and the rated flow rate, thereby minimizing the pressure loss.

[0044] As a further solution of this embodiment, the method for numerical simulation of the three-dimensional model is:

[0045] S4.1. Perform preliminary meshing of the three-dimensional model using CFD software.

[0046] S4.2. Set a turbulence model in the flow channel within the three-dimensional model. In this embodiment, the turbulence model is the RGN k-ε turbulence model or the SST k-ω turbulence model. Both the RGN k-ε model and the SST k-ω turbulence model are based on the RANS equations. Both are suitable for steady flow simulation and are specifically used for steady-state flow problems. By solving the transport equations of turbulent kinetic energy k and dissipation rate ε, a turbulent viscosity coefficient is provided for steady flow, thereby simulating the influence of turbulence on steady flow. The SST k-ω turbulence model has better simulation effects for near-wall areas and complex flows.

[0047] S4.2. Set the boundary conditions of the 3D model and use JAT A Liquid to solve the single-phase flow to obtain the test boost value of the 3D model. The convergence accuracy of the residual error of JAT A Liquid is 10 -5 . High-precision convergence requirements ensure the stability and reliability of numerical simulation results and reduce errors and uncertainties.

[0048] S4.3. Increase the mesh density of the three-dimensional model and obtain the test boost value of the three-dimensional model again.

[0049] S4.4, compare whether the change of the two test boost values ​​is less than 5%, if so, go to step S4.5, otherwise return to step S4.2. Step S4.4 is used to check the independence of mesh quality, so that the simulation results are no longer significantly dependent on the refinement of the mesh, ensuring the reliability of the simulation results.

[0050] S4.5. Use CFD software to simulate the three-dimensional model to simulate multiple outlet flow conditions and obtain the boost value of the corresponding flow conditions, and draw the flow boost curve. The flow sizes of multiple outlet flow conditions include at least 0 times, 0.2 times, 0.4 times, 0.6 times, 0.8 times, 1.0 times and 1.2 times the rated flow. By simulating multiple flow conditions, ensure that the design can maintain good performance under different working conditions, and improve the robustness and adaptability of the design.

[0051] S4.6. Obtain the boost value at rated flow rate through the flow boost curve.

[0052] In this embodiment, the setting of boundary conditions includes setting the boundary condition of the volute inlet as a pressure inlet, and taking the total pressure of the known fluid when entering the volute as an input parameter. By specifying the inlet pressure, the solver can calculate the flow characteristics entering the system according to the fluid dynamics equation. The boundary condition of the volute outlet is the mass flow rate. By specifying the mass flow rate, the solver can calculate the appropriate flow velocity and pressure according to the internal flow field conditions. The boundary condition of the exhaust duct outlet is the pressure outlet, and the pressure of the exhaust duct is set to be equal to the pressure of the volute inlet to ensure the physical consistency of the system. The solid wall of the volute adopts a no-slip wall surface. The no-slip wall surface condition is adopted to make the velocity of the fluid on the wall surface the same as the wall surface velocity, which can effectively simulate the interaction between the fluid and the solid surface and capture the formation and development of the boundary layer. The telescopic wall function method is used in the near-wall area. The telescopic wall function method is a method of approximating the turbulent flow near the wall surface. It describes the velocity distribution near the wall surface through empirical formulas or functions, thereby avoiding the use of too fine grids near the wall surface. It can be automatically adjusted according to the density of the grid to ensure the stability and accuracy of the calculation results. The frozen rotor method is used for the dynamic and static interface between the impeller and the volute. The frozen rotor method is a simplified method for dealing with the interface between the moving and static parts of rotating machinery. It approximates a dynamic problem as a steady-state problem by assuming that the relative position between the impeller and the volute is fixed during the calculation process. This method greatly simplifies the calculation and can provide more accurate results when the speed is relatively stable.

[0053] Example 2

[0054] This embodiment is further limited on the basis of Embodiment 1. The specific improvement lies in how to design a fuel pump air cavitation active control method for a fuel pump with a rated flow of 150L / h, a rotation speed of 9000r / min, a boost of 60kPa, and a maximum flight altitude of 10,000 meters. For other parts not mentioned, refer to Embodiment 1 or the prior art.

[0055] According to a fuel pump air type cavitation active control method, the impeller inlet diameter D1 is 8mm; the impeller outlet diameter D2 is 28mm; the impeller outlet width b2 is 2.5mm; the number of blades Z is 6; the blade wrap angle γ is 120°, the blade inlet placement angle β1 is 20°, and the blade inlet placement angle β2 is 30°; the volute base circle diameter is 29mm; the volute width is 7mm; and the volute outlet diameter is 8mm. The exhaust hole diameter is determined to be 5mm.

[0056] Set boundary conditions and simulate 9 operating conditions of 0L / h, 30L / h, 60L / h, 90L / h, 120L / h, 150L / h, 180L / h, 210L / h, 240L / h and 270L / h. The flow rate and pressure boost curves are as follows: Figure 3As shown. It can be seen that when the flow rate is 150L / h, the boost pressure is 64.1kPa, which meets the design requirements. Finally, according to the use requirements, it is designed as a pipeline fuel pump, refer to Figure 2 The inlet and outlet of the fuel pump are sealed with O-rings, and the exhaust passage is introduced into the fuel tank through a pipeline.

[0057] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A fuel pump air cavitation active control method, characterized in that: Includes steps: S1. Determine the performance parameters of the fuel pump according to the altitude and fuel demand of the aircraft. The performance parameters include the rated flow rate Q q , rated boost pressure ΔP, speed n and cavitation margin NPSH; S2. Calculate the hydraulic parameters of the impeller and volute in the fuel pump according to the performance parameters of the fuel pump; S3, establishing a three-dimensional model of the connection between the impeller and the volute according to the hydraulic parameters of the impeller and the volute, and modeling an exhaust pipe for communicating with the fuel tank on the volute oil outlet pipeline of the three-dimensional model; S4, performing numerical simulation on the three-dimensional model, and continuously increasing the diameter of the exhaust pipe within a set threshold range of the exhaust pipe diameter, to obtain a boost value P at a rated flow rate for different exhaust pipe diameters; S5, determine whether there is a boost value P greater than or equal to the rated boost ΔP, if so, proceed to step S6, otherwise increase the rated flow Q in the performance parameters of the fuel pump q And return to step S2; S6. Obtain the exhaust pipe diameter corresponding to the boost value P, and process the fuel pump according to the minimum diameter of the exhaust pipe and the parameters of the three-dimensional model.

2. The method for actively controlling air cavitation in a fuel pump according to claim 1, characterized in that: The exhaust pipe in the three-dimensional model is vertically connected to the volute oil outlet pipeline.

3. The method for actively controlling air cavitation in a fuel pump according to claim 2, characterized in that: The range of setting threshold d of exhaust pipe diameter is: when rated flow Q q ≤1500L / H, d=3~5mm; when rated flow Q q When >1500L / H, d=5~10mm.

4. The method for actively controlling air cavitation in a fuel pump according to claim 2, characterized in that: The method for numerical simulation of three-dimensional models is: S4.

1. Perform preliminary meshing of the three-dimensional model using CFD software; S4.2, setting a turbulence model in the flow channel within the three-dimensional model; S4.

2. Set the boundary conditions of the three-dimensional model, and use JAT ALiquid to solve the single-phase flow to obtain the test boost value of the three-dimensional model; S4.3, increasing the mesh density of the three-dimensional model and obtaining the test boost value of the three-dimensional model again; S4.4, compare whether the change of the two test boost values ​​is less than 5%, if so, proceed to step S4.5, otherwise return to step S4.2; S4.

5. Use CFD software to simulate a three-dimensional model to simulate multiple outlet flow conditions and obtain the boost values ​​of the corresponding flow conditions, and draw a flow boost curve; S4.

6. Obtain the boost value at rated flow rate through the flow boost curve.

5. The method for actively controlling air cavitation in a fuel pump according to claim 4, characterized in that: The turbulence model is the RGN k-ε turbulence model or the SST k-ω turbulence model.

6. The method for actively controlling air cavitation in a fuel pump according to claim 4, characterized in that: The setting of boundary conditions includes setting the boundary condition of the volute inlet to pressure inlet, the boundary condition of the volute outlet to mass flow, the boundary condition of the exhaust duct outlet to pressure outlet, the solid wall of the volute adopts the no-slip wall, the near-wall area adopts the telescopic wall function method, and the dynamic and static interface between the impeller and the volute adopts the frozen rotor method.

7. The method for actively controlling air cavitation in a fuel pump according to claim 4, characterized in that: The convergence accuracy of JAT A Liquid residual solution is 10 -5 .

8. The method for actively controlling air cavitation in a fuel pump according to claim 4, characterized in that: The flow sizes of the multiple outlet flow conditions at least include 0 times, 0.2 times, 0.4 times, 0.6 times, 0.8 times, 1.0 times and 1.2 times the rated flow.

9. The method for actively controlling air cavitation in a fuel pump according to claim 1, characterized in that: The hydraulic parameters of the impeller include the impeller inlet diameter, the impeller outlet diameter, the impeller outlet width, the number of blades, the blade wrap angle, the blade inlet placement angle, and the blade inlet placement angle.

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