Aviation fuel gear pump performance prediction method based on lumped parameters

Abstract

The invention discloses an aviation fuel gear pump performance prediction method based on lumped parameters. The method comprises the following steps: 1, dividing internal control volumes of the gear pump and analyzing communication relations of the control volumes; 2, establishing a gear pump dynamic mathematical model by combining the internal pressure and flow characteristics of the gear pump and the geometric structure characteristics of the gear pump; step 3, establishing a gear pump 3D model based on UG and measuring related data, storing the data in a 1D table as the input of a gear pump Amesim lumped parameter model, and simulating the change relation of the gear cavity volume and the area of each throttling channel along with the rotation of the gear pump; and 4, establishing a gear pump lumped parameter performance model based on Amesim, inputting data according to oil liquid characteristics and the gear pump 3D model, setting corresponding parameters, performing gear pump multi-working-condition performance simulation, and analyzing and predicting pressure characteristics and flow characteristics of the gear pump under different working conditions. According to the method, a gear pump lumped parameter performance model is built based on Amesim modeling software and UG geometric modeling software, so that the internal flow pressure characteristic and the output pressure flow characteristic of the gear pump are predicted.

Description

Technical Field

[0001] The invention relates to the technical field of aviation engine fuel gear pumps, and in particular to a performance prediction method for aviation fuel gear pumps based on concentrated parameters. Background Art

[0002] The external gear pump is a positive displacement oil pump, which is often used as the main fuel pump of aircraft engines. Its working performance and stability are key factors affecting the performance of aircraft engines. Domestic research on external gear pumps focuses on flow pressure characteristics, cavitation phenomenon, oil entrapment phenomenon, etc. Most of them use CFD models based on distributed parameter ideas to analyze the performance characteristics of gear pumps, and the research on concentrated parameter models is not rich enough.

[0003] Since the internal geometric relationship and component motion relationship of the fuel gear pump are relatively complex and contain a wide variety of physical phenomena, it is difficult to use the distributed parameter concept to model the gear pump as a whole; the gear pump simulation model based on the distributed parameter concept mostly uses commercial software such as Fluent and Pumplinx, and uses dynamic mesh technology to numerically simulate the internal flow field of the external meshing gear pump to analyze the pressure distribution, flow change and other performance characteristics of the internal flow field; this method is relatively cumbersome for the simulation modeling of the overall flow domain of the gear pump, requires a large number of grids, is highly dependent on boundary conditions, and is complex to solve. Summary of the invention

[0004] In order to overcome the above technical problems, the purpose of the present invention is to provide a performance prediction method for aviation fuel gear pumps based on concentrated parameters, taking into account the geometric structure of the gear pump, the internal oil flow relationship and the influencing factors of leakage, studying the gear pump tooth cavity pressure characteristics and the gear pump flow characteristics, and establishing a gear pump dynamic mathematical model; based on Amesim modeling software and UG geometric modeling software, a concentrated parameter performance model of the gear pump is built to predict the internal flow pressure characteristics and output pressure flow characteristics of the gear pump.

[0005] The technical solution adopted by the present invention is:

[0006] A method for predicting performance of an aviation fuel gear pump based on concentrated parameters comprises the following steps;

[0007] Step 1: The division of the internal control volume of the gear pump and the analysis of the interconnection relationship between each control volume are used to study the pressure characteristics of the gear chamber and the flow characteristics of the flow field in the gear pump;

[0008] Step 2: Combine the internal pressure and flow characteristics of the gear pump and the geometric structure characteristics of the gear pump to establish a gear pump dynamic mathematical model, which is used to select appropriate components and sub-models in the Amesim component library to simulate its pressure and flow characteristics;

[0009] Step 3: Based on UG, a 3D model of the gear pump is established and relevant data is measured. The data is saved in a 1D table as the input of the Amesim concentrated parameter model of the gear pump to simulate the relationship between the volume of the gear cavity and the area of ​​each throttling channel as the gear pump rotates;

[0010] Step 4: Establish a concentrated parameter performance model of the gear pump based on Amesim, input data according to the oil characteristics and the gear pump 3D model, set the corresponding parameters, perform multi-condition performance simulation of the gear pump, and analyze and predict the pressure characteristics and flow characteristics of the gear pump under different working conditions.

[0011] The step 1 is specifically as follows:

[0012] The external gear pump is a positive displacement oil pump that relies on the pressure formed between the pump cylinder and the meshing gears. Working volume The gear pump is divided into four control volumes (CV): high pressure area HP, low pressure area LP, active gear cavity V, and gear pump cavity V. 1,j , driven gear cavity V 2,j ;The density and pressure of the oil in the control volume are considered to be consistent properties that only change with time, that is, only with the rotation of the gear pump;

[0013] There is mutual flow of oil between each control volume, among which there is axial and radial throttling between the tooth cavity and the high-pressure area and the low-pressure area; i,j+1 、V i,j-1 There is oil flow due to top gap leakage and end face leakage; there is oil flow between the driving gear cavity and the driven gear cavity in the meshing area.

[0014] The step 2 is specifically as follows:

[0015] The gear pump dynamics mathematical model includes the gear chamber pressure characteristic equation and the flow characteristic equation:

[0016] 1. Analysis of tooth cavity pressure characteristics

[0017] Regarding the analysis of the pressure characteristics in the tooth cavity, it is mainly affected by the bulk elastic modulus K of the oil. The expression of the bulk modulus is:

[0018]

[0019] There are two definitions of bulk modulus K within the tooth cavity control volume:

[0020] (1) There is no mass exchange between the internal and external control volume of the tooth cavity, that is, there is no inflow or outflow of fluid, the internal flow mass remains unchanged, and the control volume changes. At this time,

[0021]

[0022] (2) The tooth cavity control volume does not change, but there is mass exchange between the control volume and the outside world, that is, there is fluid inflow and outflow, and the internal flow rate changes ΣM in -ΣM out , at this time:

[0023]

[0024] For the active gear cavity V 1,j , driven gear cavity V 2,j In the process of gear rotation, both of these control volumes have flow in and out with other control volumes, and the volume of the control volume also changes due to the meshing of the gears. That is, the above two definitions of bulk modulus exist in the tooth cavity control volume, so the pressure characteristics in the tooth cavity can be described as:

[0025]

[0026] The first term on the right side of formula (4) represents the mass change of flow caused by the oil in the control volume and the inflow and outflow of other control volumes, and the second term represents the volume change caused by the compressibility of the oil in the control volume.

[0027] Where K can be expressed as Combining formula (4), the characteristic equation of pressure change in a single tooth chamber volume can be expressed as:

[0028]

[0029] Where: p i is the instantaneous pressure inside the tooth chamber volume, ρ i is the oil density inside the tooth chamber volume, V0 is the initial volume of the tooth chamber volume, V i is the instantaneous volume of the inter-tooth space, Σm in is the mass of fluid flowing into the inter-tooth volume per unit time, Σm out It is the mass of fluid flowing out of the inter-tooth volume per unit time.

[0030] The characteristic equation of the pressure characteristics of a single tooth chamber volume is formula (5), which describes the relationship between the pressure change inside the tooth chamber volume caused by the rotation of the gear pump, the flow mass exchange between the tooth chamber control volume and other control volumes, and the volume change caused by the gear meshing;

[0031] 2. Gear pump flow characteristics analysis

[0032] Due to the different types of oil flow channels between the control volumes, the corresponding flow characteristic equations are also different. Regarding the gap flow, that is, the end gap flow and the top gap flow, since the gap is very small, the oil film thickness and the oil film length-bandwidth ratio are negligible, so the oil flow can be regarded as laminar flow, and the flow calculation formula can be expressed as:

[0033]

[0034] Where: b is the width of the oil film, h is the thickness of the oil film, L is the length of the oil film, Δp is the pressure difference, η is the dynamic viscosity of the oil, u is the oil film shear velocity of the gap, the oil flow in the flow area of ​​the tooth cavity and the high and low pressure areas and the meshing area is turbulent, and the flow rate is calculated using the throttling equation:

[0035]

[0036] In the formula, C d is the flow coefficient, A is the throttling area, and ρ is the oil density.

[0037] The step three is specifically as follows:

[0038] The gear pump was 3D modeled using UG software. The gear pump and the housing were subtracted by Boolean operations to obtain the flow field of the gear pump. The gear pump tooth cavity volume and the area of ​​each throttling channel were measured using the "measurement" command. After the relevant data were measured, the driving gear and the driven gear were rotated by the "move" command in UG. The tooth cavity volume, the area of ​​each throttling channel and other data were measured again after each rotation of 1° until the driving and driven gears rotated one circle. The measured data were saved in a 1D table as the input of the concentrated parameter performance model of the gear pump.

[0039] The step 4 is specifically as follows:

[0040] A gear pump centralized parameter performance model was built using Amesim's hydraulic library, mechanical library, and signal library components. The main process is:

[0041] 1. High and low pressure area control volume model

[0042] The control body Amesim model of the low-pressure oil suction area and high-pressure oil discharge area of ​​the gear pump. The TK000 element is a hydraulic oil tank that provides a constant pressure to simulate the inlet and outlet pressures;

[0043] The HYDORF0 element is a symmetrical orifice. It is used as a throttle to simulate the suction and discharge resistance of the oil. It can also set the relevant parameters of the element to provide boundary conditions for the size and shape of the oil inlet and discharge ports in the low and high pressure areas.

[0044] 2. Tooth cavity control volume model

[0045] The tooth chamber control body consists of two parts: a tooth chamber volume pressure change model and a tooth chamber throttling channel model. The tooth chamber volume pressure change model is used to simulate the change of the tooth chamber volume with the rotation of the gear pump. The BHC11 element is used to calculate the tooth chamber pressure characteristics according to the tooth chamber volume change input by the BAP12 element and the flow relationship of the oil. In addition to the above-mentioned tooth chamber volume pressure change model, the active tooth chamber control body Amesim model also includes the throttling channels between the tooth chamber and the high-pressure area, the low-pressure area, the driven tooth chamber, and the front and rear tooth chambers.

[0046] The HYDVORF0 element is an adjustable flow nozzle, and the change of its throttle area can be used to represent the change of the actual throttle area. The laminar throttling of the inter-tooth volume through the tooth top gap and the gear end face in the non-meshing area is simulated by the laminar flow element BRF02. The laminar flow includes shear flow and pressure difference flow. The input speed signal is used below to simulate the shear velocity of the shear flow, and the pressure on the upper side simulates the pressure difference flow.

[0047] Compared with the driving gear tooth cavity model, the driven gear tooth cavity model has a flow throttling channel between the driving gear and the two driven gears in front and behind it in the driven gear tooth cavity control volume model. The rest of the model is consistent with the driving gear model. After the driving and driven gear tooth cavity control volume models are built, they are packaged into super components for easy connection with other partial models.

[0048] 3. Gear pump motion analysis model

[0049] Gear pump motion analysis model, PM000 element is a constant speed prime mover, used to simulate the speed of the gear pump; MECADS0B element is an angular displacement sensor, which converts the speed (rev / min) input by PM000 into an angular displacement signal and outputs it to each tooth cavity model;

[0050] 4. Gear pump Amesim concentrated parameter performance model

[0051] According to the internal geometric structure and oil flow characteristics of the gear pump, the above-mentioned models are connected accordingly, and the relevant parameters are set to complete the establishment of the Amesim concentrated parameter performance model of the gear pump.

[0052] Beneficial effects of the present invention:

[0053] The present invention relates to the technical field of aviation engine fuel gear pumps, and provides a modeling method for a concentrated parameter performance model of an aviation fuel gear pump. Based on the idea of ​​concentrated parameters, the method divides the internal flow field of the gear pump into multiple control volumes, and ignores the distribution characteristics of variables in the space within a control volume, keeps consistency everywhere inside the control volume, and simplifies the simulation calculation model of the gear pump; the method does not need to mesh the internal flow field of the gear pump, but uses the corresponding elements in the Amesim element library to simulate the flow and pressure characteristics of each control volume of the gear pump, and UG establishes the gear pump 3D model to measure the relevant data, which is used to simulate the volume change of the tooth cavity and the area change of the throttling channel between the control volumes, thereby realizing the simulation of the overall flow domain of the gear pump, reducing the difficulty of solving. The present invention builds a concentrated parameter performance model for a fuel gear pump, which is used to analyze the multi-condition performance characteristics of the gear pump and predict the output characteristics of the fuel gear pump, providing certain theoretical help and driving force for the development and innovation of aviation gear pumps. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is an invention technology flow chart.

[0055] Figure 2 It is a division diagram of the internal control volume of the gear pump.

[0056] Figure 3 Diagram of the connectivity between control volumes.

[0057] Figure 4 Schematic diagram of top gap leakage TLN and end face leakage BPN.

[0058] Figure 5 Schematic diagram of the tooth cavity, high and low pressure areas, and throttling channels in the meshing area.

[0059] Figure 6 Gear pump 3D model Figure 7 3D model diagram of the gear pump flow field.

[0060] Figure 8 Schematic diagram of the rotation operation of the master and driven gears.

[0061] Fig. 9 Flowchart for building a centralized parameter model for a gear pump.

[0062] Fig.10 Schematic diagram of the AMEsim model of the oil inlet control body in the low-pressure area.

[0063] Fig.11 Schematic diagram of the AMEsim model of the oil outlet control body in the high-pressure area.

[0064] Fig.12 Schematic diagram of the tooth cavity volume pressure change model.

[0065] Fig.13 Schematic diagram of the active gear tooth cavity model.

[0066] Fig.14 Schematic diagram of the driven gear tooth cavity model.

[0067] Fig.15 Schematic diagram of the gear pump motion analysis model.

[0068] Fig.16 Schematic diagram of the lumped parameter performance model of a gear pump.

[0069] Fig.17 This is the instantaneous output flow curve of the gear pump when n=6000r / min.

[0070] Fig.18 Graph of average output flow of a gear pump at different speeds. DETAILED DESCRIPTION

[0071] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0072] A method for predicting performance of an aviation fuel gear pump based on concentrated parameters comprises the following steps;

[0073] Part 1: Division of the internal control volume of the gear pump and analysis of the interconnection relationship between the control volumes:

[0074] The external gear pump is a positive displacement oil pump that relies on the change and movement of the working volume formed between the pump cylinder and the meshing gears to transport liquid or increase its pressure. Combined with the idea of ​​​​lumped parameters, the interior of the gear pump is divided into multiple control volumes to describe its internal flow characteristics. Figure 2 The interior of the gear pump is mainly divided into four control volumes (CV): high pressure area HP, low pressure area LP, active gear cavity V 1,j The density, pressure and other properties of the oil in the control volume are considered to be consistent and only change with time, that is, only with the rotation of the gear pump.

[0075] There is mutual flow of oil between each control volume, from the active gear cavity V 1,j , driven gear cavity V 2,j Starting from the geometric structure and flow relationship of the gear pump, the flow of oil is represented by a straight line, and the throttle valve icon represents the throttling channel between the control volumes, such as Figure 3The tooth cavity is connected to the high pressure area through the axial throttling channel HG and the radial throttling channel HV; it is connected to the low pressure area through the axial throttling channel LG and the radial throttling channel LV; the tooth cavity is connected to the front and rear tooth cavities V i,j+1 、V i,j-1 Due to the top gap leakage and end face leakage, there is oil flow. The throttling channels for the oil to flow to the front and rear tooth chambers through the end face gap are BPP and BPN respectively; the throttling channels for the oil to flow to the front and rear tooth chambers through the tooth top gap are TLP and TLN respectively; in the meshing area, there is oil flow between the active tooth chamber and the driven tooth chamber through the meshing gap, and the corresponding throttling channel is FG.

[0076] Table 1 Meaning of throttling channel between control volumes

[0077]

[0078] Part II: Establishment of mathematical model of gear pump dynamics:

[0079] The gear pump dynamics mathematical model includes the gear chamber pressure characteristic equation and the flow characteristic equation:

[0080] 1. Analysis of tooth cavity pressure characteristics:

[0081] Regarding the analysis of the pressure characteristics in the tooth cavity, it is mainly affected by the bulk elastic modulus K of the oil. The expression of the bulk modulus is:

[0082]

[0083] There are two definitions of bulk modulus K within the tooth cavity control volume:

[0084] (1) There is no mass exchange between the internal and external parts of the tooth cavity control volume, that is, there is no inflow or outflow of fluid, the internal flow mass remains unchanged, and the control volume changes. At this time:

[0085]

[0086] (2) The tooth cavity control volume does not change, but there is mass exchange between the control volume and the outside world, that is, there is fluid inflow and outflow, and the internal flow rate changes ΣM in -∑M out . At this time, there are:

[0087]

[0088] For the active gear cavity V 1,j , driven gear cavity V 2,jIn the process of gear rotation, both of these control volumes have flow in and out of other control volumes, and due to the meshing of the gears, the volume of the control volume also changes, that is, the above two definitions of bulk modulus exist in the tooth cavity control volume. Therefore, the pressure characteristics in the tooth cavity can be described as:

[0089]

[0090] The first term on the right side of formula (4) represents the flow mass change caused by the oil in the control volume and the flow out of other control volumes, and the second term represents the volume change caused by the compressibility of the oil in the control volume.

[0091] Where K can be expressed as Combining formula (4), the characteristic equation of pressure change in a single tooth chamber volume can be expressed as:

[0092]

[0093] Where: p i is the instantaneous pressure inside the tooth chamber volume, ρ i is the oil density inside the tooth chamber volume, V0 is the initial volume of the tooth chamber volume, V i is the instantaneous volume of the inter-tooth space, ∑m in is the mass of fluid flowing into the inter-tooth volume per unit time, ∑m out It is the mass of fluid flowing out of the inter-tooth volume per unit time.

[0094] The characteristic equation of the pressure characteristic of a single tooth chamber volume, namely formula (5), describes the relationship between the pressure change inside the tooth chamber volume caused by the rotation of the gear pump, the flow mass exchange between the tooth chamber control volume and other control volumes, and the volume change caused by the gear meshing.

[0095] 2. Gear pump flow characteristics analysis:

[0096] Due to the different types of oil flow channels between the control volumes, the corresponding flow characteristic equations are also different. Regarding the gap flow, that is, the end gap flow and the top gap flow, as shown in Figure 4 , because the gap is very small, the oil film thickness and the oil film length-width ratio can be ignored, so the oil flow can be regarded as laminar flow, and the flow calculation formula can be expressed as:

[0097]

[0098] Where: b is the width of the oil film, h is the thickness of the oil film, L is the length of the oil film, Δp is the pressure difference, η is the dynamic viscosity of the oil, and u is the oil film shear velocity of the gap. Figure 5The throttling channels between the tooth cavity and the high-pressure area are shown as HV and HG; the throttling channels between the tooth cavity and the low-pressure area are shown as LG and LV, and the throttling channel between the meshing area is shown as FG.

[0099] The oil flow in this area is turbulent, and the flow rate is calculated using the throttling equation:

[0100]

[0101] In the formula, C d is the flow coefficient, A is the throttling area, and ρ is the oil density.

[0102] Part 3: Establish a 3D model of the gear pump based on UG and measure relevant data:

[0103] Use UG software to perform 3D modeling of gear pumps. Figure 6 Through Boolean operation, the gear pump and the housing are subtracted to obtain the flow field of the gear pump as follows: Figure 7 . Use the "measure" command to measure the volume of the gear pump tooth cavity and the area of ​​each throttling channel. When the relevant data are measured, use the "move" command in UG to rotate the driving gear and the driven gear, such as Figure 8 As shown in the figure, the volume of the tooth cavity, the area of ​​each throttling channel and other data are measured again after each rotation of 1° until the master and slave gears rotate one circle. The measured data are saved in a 1D table as the input of the gear pump concentrated parameter performance model.

[0104] Part 4: Establishing the concentrated parameter performance model of gear pump based on Amesim:

[0105] The present invention uses the hydraulic library, mechanical library, and signal library components of Amesim to build a gear pump centralized parameter performance model. The main process is as follows: Fig. 9 .

[0106] 1. High and low pressure area control volume model

[0107] The Amesim model of the control body of the low-pressure oil suction area and the high-pressure oil discharge area of ​​the gear pump is as follows Fig.10 and Fig.11 As shown, the TK000 component is a hydraulic oil tank that can provide constant pressure to simulate the inlet and outlet pressure. The HYDORF0 component is a symmetrical orifice that is used as a throttle to simulate the suction and discharge resistance. At the same time, the relevant parameters of the component can also be set to provide boundary conditions such as the inlet and outlet size and shape for the low and high pressure areas.

[0108] 2. Tooth cavity control volume model:

[0109] The tooth cavity control body consists of two parts: the tooth cavity volume pressure change model and the tooth cavity throttling channel model. Fig.12The figure shows the tooth chamber volume pressure change model, which is used to simulate the change of the tooth chamber volume with the rotation of the gear pump. The BHC11 element is used to calculate the tooth chamber pressure characteristics according to the tooth chamber volume change input by the BAP12 element and the flow relationship of the oil.

[0110] Amesim model of active tooth cavity control body Fig.13 As shown in the figure, the throttling channel is expanded on the basis of the tooth chamber volume pressure change model, and the throttling channel models of the tooth chamber and the high and low pressure areas, the front and rear tooth chambers, and the driven tooth chamber are added. The HYDVORF0 element is an adjustable flow nozzle, and the change in its throttling port area can be used to represent the change in the actual throttling area. The laminar throttling of the inter-tooth volume through the tooth top gap and the gear end face in the non-meshing area is simulated by the laminar flow element BRF02. The laminar flow includes shear flow and pressure difference flow. The input velocity signal is used below to simulate the shear velocity of the shear flow, and the upper pressure simulates the pressure difference flow.

[0111] like Fig.14 The figure shows the driven gear tooth cavity model. Compared with the driving gear tooth cavity model, the driven gear inter-tooth volume control volume model does not have a flow throttling channel between the driving gear and the two driven gears in front and behind it. The rest of the model is consistent with the driving gear model. After the driving and driven gear tooth cavity control volume models are built, they are packaged into super components for easy connection with other partial models.

[0112] 3. Gear pump motion analysis model:

[0113] Gear pump motion analysis model Fig.15 As shown, the PM000 component is a constant speed prime mover used to simulate the speed of the gear pump; the MECADS0B component is an angular displacement sensor that converts the speed (rev / min) input by PM000 into an angular displacement signal and outputs it to each tooth cavity model.

[0114] 4. Gear pump Amesim concentrated parameter performance model:

[0115] Gear pump AMEsim centralized parameter model such as Fig.16 As shown, according to the internal geometric structure of the gear pump and the oil flow characteristics, the above-mentioned models are connected accordingly. The gear pump motion analysis part converts the rotational speed into an angle signal and inputs it into each tooth cavity super element; each tooth cavity super element is connected to the high-pressure area, low-pressure area and corresponding tooth cavity according to the oil flow, and the oil-related parameters are set to complete the establishment of the gear pump Amesim concentrated parameter performance model.

[0116] Part V: Examples:

[0117] The advantages of the present invention can be further illustrated by the following simulation experiment:

[0118] 1. Simulation parameters

[0119] Tables 2 and 3 give the key physical properties and values ​​of a certain type of aviation kerosene and the key structural parameters of a certain type of gear pump.

[0120] Table 2 Gear pump related parameters

[0121]

[0122] Table 3 Oil parameters

[0123]

[0124] The present invention uses the gear pump concentrated parameter performance model established based on Amesim and the Amesim cavitation model to simulate the pressure and flow characteristics of the gear pump. During the simulation, the gear pump is rotated fully twice, and the convergent and stable simulation results are taken for analysis and research.

[0125] 2. Simulation results

[0126] Set the inlet pressure to 0 bar and the outlet pressure to 20 bar, and set the oil physical parameters in combination with the Amesim oil element. When the gear pump speed is 6000r / min, the instantaneous output flow pulsation curve is as follows: Fig.17 As shown. After the simulation stabilizes, the maximum instantaneous flow rate q of the gear pump max =19.98L / min, minimum instantaneous flow rate q min =10.10L / min, average output flow q = 16.04L / min, flow pulsation coefficient is 0.616, volumetric efficiency is greater than 80%. Other conditions remain unchanged, change the gear pump speed 3000-8000r / min, Δn = 1000r / min, perform multiple simulations, and obtain the relationship between the average output flow of the gear pump and the speed at different speeds. Fig.18 As shown in the figure, the output flow rate increases with the increase of speed. When the speed is 8000r / min, the average output flow rate is low, and its flow pulsation rate is 0.835. As the speed increases, the higher speed brings higher pressure, which leads to more drastic changes in the internal pressure of the gear pump, causing stronger pressure pulsation, which in turn leads to an increase in the amplitude of flow pulsation and a decrease in the volumetric efficiency of the gear pump.

[0127] The centralized parameter idea can reduce the dimension of the system, reduce the system's degree of freedom, simplify the system model, and is more conducive to establishing a systematic model containing multiple parts. The centralized parameter model is more advantageous in studying the overall performance characteristics of gear pumps.

Claims

1. A method for predicting the performance of an aviation fuel gear pump based on concentrated parameters, characterized in that: The steps include: Step 1: The division of the internal control volume of the gear pump and the analysis of the interconnection relationship between each control volume are used to study the pressure characteristics of the gear chamber and the flow characteristics of the flow field in the gear pump; Step 2: Combine the internal pressure and flow characteristics of the gear pump and the geometric structure characteristics of the gear pump to establish a gear pump dynamic mathematical model, which is used to select appropriate components and sub-models in the Amesim component library to simulate its pressure and flow characteristics; Step 3: Based on UG, a 3D model of the gear pump is established and relevant data is measured. The data is saved in a 1D table as the input of the Amesim concentrated parameter model of the gear pump to simulate the relationship between the volume of the gear cavity and the area of ​​each throttling channel as the gear pump rotates; Step 4: Establish a concentrated parameter performance model of the gear pump based on Amesim, input data according to the oil characteristics and the gear pump 3D model, set the corresponding parameters, perform multi-condition performance simulation of the gear pump, and analyze and predict the pressure characteristics and flow characteristics of the gear pump under different working conditions.

2. The method for predicting the performance of an aviation fuel gear pump based on concentrated parameters according to claim 1, characterized in that: The step 1 is specifically as follows: The external gear pump is a positive displacement oil pump that relies on the change and movement of the working volume formed between the pump cylinder and the meshing gears to transport liquid or increase its pressure. The gear pump is divided into multiple control volumes to describe its internal flow characteristics. The gear pump is divided into four control volumes (CV): high pressure area HP, low pressure area LP, active gear cavity V 1,j , driven gear cavity V 2,j ;The density and pressure of the oil in the control volume are considered to be consistent properties that only change with time, that is, only with the rotation of the gear pump; There is mutual flow of oil between each control volume, among which there is axial and radial throttling between the tooth cavity and the high-pressure area and the low-pressure area; i,j+1 、V i,j-1 There is oil flow due to top gap leakage and end face leakage; there is oil flow between the driving gear cavity and the driven gear cavity in the meshing area.

3. The method for predicting the performance of an aviation fuel gear pump based on concentrated parameters according to claim 1, characterized in that: The step 2 is specifically as follows: The gear pump dynamics mathematical model includes the gear chamber pressure characteristic equation and the flow characteristic equation: 1). Analysis of tooth cavity pressure characteristics Regarding the analysis of the pressure characteristics in the tooth cavity, it is affected by the bulk elastic modulus K of the oil. The expression of the bulk modulus is: There are two definitions of bulk modulus K within the tooth cavity control volume: (1) There is no mass exchange between the internal and external control volume of the tooth cavity, that is, there is no inflow or outflow of fluid, the internal flow mass remains unchanged, and the control volume changes. At this time, (2) The tooth cavity control volume does not change, but there is mass exchange between the control volume and the outside world, that is, there is fluid inflow and outflow, and the internal flow rate changes ΣM in -ΣM out , at this time: For the active gear cavity V 1,j , driven gear cavity V 2,j In the process of gear rotation, both control volumes have flow in and out with other control volumes, and the volume of the control volume also changes due to the meshing of the gears. That is, the above two definitions of bulk modulus exist in the tooth cavity control volume, so the pressure characteristics in the tooth cavity can be described as: The first term on the right side of formula (4) represents the mass change of flow caused by the oil in the control volume and the inflow and outflow of other control volumes, and the second term represents the volume change caused by the compressibility of the oil in the control volume. Where K is represented by Combining formula (4), the characteristic equation of pressure change in a single tooth chamber volume can be expressed as: Where: p i is the instantaneous pressure inside the tooth chamber volume, ρ i is the oil density inside the tooth chamber volume, V0 is the initial volume of the tooth chamber volume, V i is the instantaneous volume of the inter-tooth space, Σm in is the mass of fluid flowing into the inter-tooth volume per unit time, Σm out is the mass of fluid flowing out of the inter-tooth volume per unit time; The characteristic equation of the pressure characteristics of a single tooth chamber volume is formula (5), which describes the relationship between the pressure change inside the tooth chamber volume caused by the rotation of the gear pump, the flow mass exchange between the tooth chamber control volume and other control volumes, and the volume change caused by the gear meshing; 2). Gear pump flow characteristics analysis Regarding the gap flow, that is, the end gap flow and the top gap flow, if the oil flow is regarded as laminar flow, the flow calculation formula is expressed as: Where: b is the width of the oil film, h is the thickness of the oil film, L is the length of the oil film, Δp is the pressure difference, η is the dynamic viscosity of the oil, u is the oil film shear velocity of the gap, the oil flow in the flow area of ​​the tooth cavity and the high and low pressure areas and the meshing area is turbulent, and the flow rate is calculated using the throttling equation: In the formula, C d is the flow coefficient, A is the throttling area, and ρ is the oil density.

4. The method for predicting the performance of an aviation fuel gear pump based on concentrated parameters according to claim 1, characterized in that: The step three is specifically as follows: The gear pump was 3D modeled using UG software. The gear pump and the housing were subtracted through Boolean operations to obtain the flow field of the gear pump. The gear pump tooth cavity volume and the area of ​​each throttling channel were measured using the "measurement" command. After the relevant data were measured, the driving gear and the driven gear were rotated using the "move" command in UG. The tooth cavity volume and the area of ​​each throttling channel were measured again after each rotation of 1° until the driving and driven gears rotated one circle. The measured data were saved in a 1D table as the input of the concentrated parameter performance model of the gear pump.

5. The method for predicting the performance of an aviation fuel gear pump based on concentrated parameters according to claim 1, characterized in that: The step 4 is specifically as follows: The gear pump centralized parameter performance model was built using Amesim's hydraulic library, mechanical library, and signal library components. The process is as follows: 1). High and low pressure area control volume model The control body Amesim model of the low-pressure oil suction area and high-pressure oil discharge area of ​​the gear pump. The TK000 element is a hydraulic oil tank that provides a constant pressure to simulate the inlet and outlet pressures; The HYDORF0 element is a symmetrical orifice. It is used as a throttle to simulate the suction and discharge resistance of the oil. It can also set the relevant parameters of the element to provide boundary conditions for the size and shape of the oil inlet and discharge ports in the low and high pressure areas. 2). Tooth cavity control volume model The tooth chamber control body consists of two parts: a tooth chamber volume pressure change model and a tooth chamber throttling channel model. The tooth chamber volume pressure change model is used to simulate the change of the tooth chamber volume with the rotation of the gear pump. The BHC11 element is used to calculate the tooth chamber pressure characteristics according to the tooth chamber volume change input by the BAP12 element and the flow relationship of the oil. In addition to the above-mentioned tooth chamber volume pressure change model, the active tooth chamber control body Amesim model also includes the throttling channels between the tooth chamber and the high-pressure area, the low-pressure area, the driven tooth chamber, and the front and rear tooth chambers. The HYDVORF0 element is an adjustable flow nozzle, and the change of its throttle area represents the change of the actual throttle area. The laminar throttling of the inter-tooth volume through the tooth top gap and the gear end face in the non-meshing area is simulated by the laminar flow element BRF02. The laminar flow includes shear flow and pressure difference flow. The input speed signal is used below to simulate the shear velocity of the shear flow, and the pressure on the upper side simulates the pressure difference flow. Compared with the driving gear tooth cavity model, the driven gear tooth cavity volume control volume model does not have a flow throttling channel between the driving gear and its two driven gears in front and behind it. The rest of the model is consistent with the driving gear model. After the driving and driven gear tooth cavity control volume models are built, they are packaged into super components to facilitate connection with other partial models. 3). Gear pump motion analysis model Gear pump motion analysis model, PM000 element is a constant speed prime mover, used to simulate the speed of the gear pump; MECADS0B element is an angular displacement sensor, which converts the speed (rev / min) input by PM000 into an angular displacement signal and outputs it to each tooth cavity model; 4). Amesim concentrated parameter performance model for gear pumps According to the internal geometric structure and oil flow characteristics of the gear pump, the above-mentioned models are connected accordingly, and the relevant parameters are set to complete the establishment of the Amesim concentrated parameter performance model of the gear pump, and the pressure characteristics and flow characteristics of the gear pump under different working conditions are analyzed and predicted.

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