A dynamic metering method and device based on coordinated control of electric fuel pump flow

Abstract

The present invention discloses a pump-cylinder composite dynamic metering method and device for closed-loop control of the fuel quantity of an electric fuel pump, which belongs to the field of fuel metering control. It includes a metering device controller, a metering pump and its servo motor, an unloaded hydraulic cylinder, an over-limit protection bypass port, a two-way return spring, etc. On the basis of fully utilizing the high-frequency dynamic flow measurement capability of the pump-cylinder composite metering, the over-travel protection bypass port and the two-way return spring are used to avoid the occurrence of the cylinder-pushing phenomenon of the unloaded hydraulic cylinder, and through the coordinated control of the metering pump servo motor and the electric pump motor speed, the electric pump motor speed is used as the metering pump servo motor feedforward, thereby improving the metering pump response speed and widening the flow metering range. Compared with the prior art, the method and device of the present invention have better dynamic metering characteristics and a more reliable structure, which can better meet the needs of closed-loop control of the flow of electric fuel pumps.

Description

Technical Field

[0001] The present invention relates to a dynamic metering method and device based on coordinated control of electric fuel pump flow, belonging to the technical field of fuel flow metering control. Background Art

[0002] Accurate flow measurement is not only a crucial component of science and technology but also a hallmark of modern society's progress. It's widely used in industries such as hydraulics, chemicals, engineering machinery, metallurgy, and water conservancy. While components for measuring steady-state flow have become increasingly mature and standardized in the market, the challenge of accurately measuring dynamic flow remains a challenge. To date, no ideal instrument or device for high-frequency dynamic flow measurement has emerged on the market.

[0003] With the rapid development of modern electrical and electronic technologies, the concept of new multi- and fully electrified powertrains has profoundly transformed the landscape of modern powertrains. In the field of aircraft engines, multi-electric engines have become a key development direction for advanced aircraft engine technology. As a key control component, the electric fuel pump has a significant impact on the performance of multi-electric engines. For the electric fuel pump to deliver fuel according to engine demand at all times, a controller is required to provide closed-loop flow control of the electric fuel pump, enabling rapid response across a wide flow range. Therefore, a high-precision, dynamic fuel metering method is required to accurately and quickly measure the fuel flow of the electric fuel pump.

[0004] Among the existing disclosed patent technology solutions, the invention patent with publication number CN104583733B proposes a gear flowmeter for measuring fluid flow. The gear flowmeter has a gear chamber, and at least two measuring gears are engaged with each other and arranged in the gear chamber. The flow through the gear chamber can be determined according to the gear speed. Based on this measurement principle, a gear pump actively controlled by a servo motor can also measure the flow.

[0005] Patent publication number CN107882786A proposes a closed-loop pump-controlled, single-rod hydraulic cylinder static and dynamic flow real-time matching system. This proposed system also connects the pump and hydraulic cylinder in parallel, with a controller collecting the hydraulic cylinder piston position and controlling the gear pump. However, this patent design is an electro-hydraulic control system and does not involve flow measurement methods. Patent publication numbers CN105952607B and CN109060057A both use hydraulic cylinders and metering pumps in parallel, but neither proposes using this system for flow measurement in electric fuel pumps.

[0006] In the papers "New Dynamic Flowmeter with a Pump-Cylinder Composite Structure" published in December 2015 and "Measurement Model of a Composite Flowmeter" published in April 2022, Liu Tao and other scholars from Yanshan University designed a composite dynamic flowmeter for measuring dynamic flow with continuous bias, established a physical model, and conducted experimental research. This composite flowmeter consists solely of a metering pump and an unloaded hydraulic cylinder in parallel, and is used to measure the high-frequency pulsating bias flow of an electro-hydraulic servo valve. However, the metering pump speed of this composite flowmeter is controlled solely by the displacement of the unloaded hydraulic cylinder piston, making it incapable of measuring complex dynamic flow changes. The hydraulic cylinder can cause a phenomenon called "cylinder push-up" when the flow rate varies over a wide range. Furthermore, the measuring range is limited by the size of the hydraulic cylinder, making it impossible to measure a wide range of flow. Summary of the Invention

[0007] The present invention aims to overcome the difficulties of existing high-frequency dynamic flow measurement and solve the closed-loop control problem of electric fuel pump flow. It provides a dynamic metering method and device based on the coordinated control of electric fuel pump flow. The method utilizes the dynamic performance of an unloaded hydraulic cylinder to measure high-frequency dynamic flow, while the metering pump's continuous reciprocating metering capability measures low-frequency steady-state flow, achieving accurate metering of complex high-frequency dynamic flow rates from electric fuel pumps. Furthermore, the unloaded hydraulic cylinder features an innovative design that adds over-limit protection during flow metering to prevent hydraulic cylinder overshooting. A bidirectional return spring is also added to broaden the metering range of the fuel metering device.

[0008] The technical solution adopted by the present invention is as follows: a dynamic metering method and device based on coordinated control of the flow of an electric fuel pump, which is characterized by including an electric fuel pump, a metering pump, an unloaded hydraulic cylinder, an over-limit protection bypass port, a two-way return spring, an LVDT, and a piston; wherein the metering pump is connected in parallel with the hydraulic cylinder, the piston is placed inside the hydraulic cylinder and connected to the two-way return spring, the over-limit protection bypass port is integrated into the outside of the hydraulic cylinder, and the LVDT is installed at the end of the piston rod. The inlet of the fuel metering device is connected to the electric fuel pump, and the outlet is connected to the fuel nozzle; the dynamic flow metering method dynamically meters the fuel flow by measuring the rotational speed of the metering pump and the displacement of the hydraulic cylinder piston.

[0009] Furthermore, in the active metering pump control process, during closed-loop flow control of the electric fuel pump, the controller obtains the electric fuel pump speed through feedback from the speed sensor. Based on the displacement of the electric fuel pump and the metering pump, it calculates the metering pump speed command n1. During the metering process, the controller uses the displacement of the hydraulic cylinder piston relative to the center position via the LVDT and uses this as the input for PID control to calculate the speed command n2. The sum of n1 and n2 serves as the speed command for the active metering pump control. Based on this control logic, the metering pump's response speed is improved, and the flow metering range is expanded.

[0010] Furthermore, the bidirectional return spring is installed on both sides of the piston and connected to the side of the hydraulic cylinder. When the piston moves, the displacement generated is always proportional to the elastic force received. The bidirectional return spring first determines that the dynamic balance position is always the center of the hydraulic cylinder and will not change, which is convenient for the formulation of the control plan. At the same time, during the metering process, the pressure difference on both sides of the hydraulic cylinder can be calculated by the stiffness of the bidirectional return spring and the acceleration of the piston. It is used to calculate the leakage flow of the hydraulic cylinder and the metering pump through the leakage model, making the metering more accurate. In addition, when the control exceeds the limit, the piston moves to open the bypass port. At this time, the pressure difference force on both sides of the bypass port is the elastic force received by the piston. When the metering pump is freed from the limit, the spring force can provide an external force to close the bypass port and restore the normal metering state.

[0011] Furthermore, the over-limit protection bypass port is integrated into the hydraulic cylinder, and its distance from the center of the hydraulic cylinder is the maximum stroke of the piston. When the metering pump and the hydraulic cylinder are metering normally, the piston moves within the maximum stroke and the over-limit protection bypass port does not open, allowing for accurate dynamic flow metering. If a control error or equipment problem occurs and normal metering cannot be achieved, an excessive pressure differential is generated on both sides of the hydraulic cylinder, pushing the piston to open the over-limit protection bypass port, allowing fluid on both sides of the hydraulic cylinder to flow through the bypass port, preventing the hydraulic cylinder from pushing the cylinder up, and providing over-limit protection for metering control.

[0012] Compared with the prior art, the advantages of the present invention are:

[0013] 1) Since most flowmeter products are designed primarily to measure steady-state flow under various operating conditions, they are unlikely to have good dynamic flow metering performance and cannot meet the closed-loop control requirements of electric fuel pumps. However, by using the unloaded hydraulic cylinder of this device to measure high-frequency dynamic flow and the metering pump to measure low-frequency steady-state flow, accurate dynamic metering of a large range of electric fuel pumps can be achieved, enabling high-precision closed-loop control of the fuel flow of the electric fuel pump, greatly improving the actual performance of the electric fuel pump.

[0014] 2) The coordinated control of the electric fuel pump servo motor and the metering pump servo motor, as well as the closed-loop control composed of the metering pump and the unloaded hydraulic cylinder, can effectively improve the response speed of the metering pump and broaden the flow metering range.

[0015] 3) By designing an over-limit protection bypass port and a bidirectional return spring, the center position of the hydraulic cylinder can be set to the dynamic balance position, providing over-limit protection for metering control and preventing the hydraulic cylinder from pushing the cylinder up. During the metering process, the pressure differential across the hydraulic cylinder can be calculated using the stiffness of the bidirectional return spring and the acceleration of the piston. This is used to calculate the leakage flow rate between the hydraulic cylinder and the metering pump using a leakage model, resulting in more accurate metering.

[0016] 4) The pressure loss of fuel after passing through the dynamic fuel metering device is small, and the maximum pressure loss can be calculated based on the stroke.

[0017] 5) No differential pressure sensor is required during the metering process, which greatly reduces the fuel metering device's dependence on the number and performance of sensors and significantly improves the reliability of fuel metering. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Attachment Figure 1 This is a structural design diagram of a dynamic metering method and device based on coordinated control of electric fuel pump flow rate according to the present invention;

[0019] Attachment Figure 2 This is a closed-loop control block diagram of the fuel flow of an electric fuel pump based on the dynamic metering method and device for coordinated control of the flow of an electric fuel pump of the present invention;

[0020] Attachment Figure 3 It is the hydraulic system AMESim model of the dynamic metering method and device based on the coordinated control of the electric fuel pump flow rate of the present invention;

[0021] Attachment Figure 4 It is a controller Simulink model of the dynamic metering method and device based on the coordinated control of the flow rate of the electric fuel pump of the present invention;

[0022] Attachment Figure 5 This is the simulation result of the metering pump control based on the dynamic metering method and device of the electric fuel pump flow coordinated control of the present invention

[0023] Attachment Figure 6 The present invention discloses a dynamic metering method and device for coordinated control of electric fuel pump flow rate, and fuel flow rate metering results and errors.

[0024] Figure 1 1 is the electric fuel pump, 2 is the metering pump, 3 is the no-load hydraulic cylinder, 4 is the over-limit protection bypass port, 5 is the two-way return spring, 6 is the LVDT, 7 is the piston, and 8 is the nozzle. DETAILED DESCRIPTION

[0025] The technical solutions of the present invention are further described below with reference to the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and are not to be construed as limiting the present invention.

[0026] It should be understood that in the description of the present invention, various terms indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation and be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or a direct integrated combination connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0028] like Figure 1 The dynamic fuel metering device based on an electric fuel pump shown in the figure is characterized by comprising an electric fuel pump 1, a metering pump 2, an unloaded hydraulic cylinder 3, an over-limit protection bypass port 4, a two-way return spring 5, an LVDT 6, a piston 7, and a nozzle 8; wherein the metering pump 2 is connected in parallel with the unloaded hydraulic cylinder 3, the piston 7 is placed inside the unloaded hydraulic cylinder (3) and is connected to the two-way return spring 5, the over-limit protection bypass port 4 is integrated outside the hydraulic cylinder 3, the LVDT 6 is installed at the end of the piston 7 rod, the inlet of the fuel metering device is connected to the electric fuel pump 1, and the outlet is connected to the fuel nozzle 8:

[0029] like Figure 2 The electric fuel pump's fuel flow closed-loop control and metering pump active control system shown in the figure incorporates a flow closed-loop in addition to the motor speed closed-loop. The calculated flow rates of the metering pump, unloaded hydraulic cylinder, and leakage compensation flow rate are used as feedback, improving the practical performance of the electric fuel pump. During the electric fuel pump's closed-loop flow control, the controller obtains the electric fuel pump's speed through feedback from the electric pump encoder. The metering pump's speed command, n1, is calculated based on the displacements of the electric fuel pump and metering pump. During the metering process, the controller uses the LVDT to measure the displacement of the hydraulic cylinder's piston relative to its center position. This is used as an input for PID control to calculate the metering pump's speed command, n2. The sum of n1 and n2 serves as the speed command for the metering pump's active control. The metering pump's closed-loop control objective is to ensure equal pressure on both sides of the hydraulic cylinder and return the piston to its center position in the unloaded cylinder. This control logic improves the metering pump's response speed and broadens the flow metering range.

[0030] The bidirectional return springs are mounted on either side of the piston and connected to the sides of the hydraulic cylinder. When the piston moves, the displacement generated is always proportional to the elastic force applied. Since the piston displacement is controlled by the controller to adjust the metering pump speed, the center of the hydraulic cylinder becomes the equilibrium position of the piston under the combined action of the metering pump and the bidirectional return springs. By selecting the stiffness of the bidirectional return springs, the maximum pressure drop of the fuel metering device can be calculated as follows:

[0031]

[0032] Where K is the stiffness of the bidirectional return spring, L is the distance between the bypass port and the center of the piston, that is, the piston stroke, D is the diameter of the piston, and d is the diameter of the piston rod. Similarly, this pressure difference is also the maximum pressure difference on both sides of the hydraulic cylinder when the pressure does not exceed the limit during the metering process. Pressure difference during metering:

[0033]

[0034] Where x is the piston displacement, M is the total mass of the piston, and a is the piston's acceleration. By calculating the pressure differential and establishing an accurate leakage model based on the structural parameters and testing of the metering pump and unloaded hydraulic cylinder, the amount of leakage during the metering process can be accurately calculated and compensated for, resulting in more accurate metering results. When a control overrun or equipment error occurs, the piston moves until the bypass port opens. At this time, the pressure differential force on both sides of the bypass port is the elastic force acting on the piston. When the fuel metering device is cleared of the overrun, the spring force provides the external force to close the bypass port, restoring normal metering. Without a bidirectional return spring, the bypass port cannot be closed by controlling the metering pump alone after it is opened.

[0035] The over-limit protection bypass port is integrated into the hydraulic cylinder, and its distance from the center of the hydraulic cylinder is the maximum stroke of the piston movement. When the metering pump and the hydraulic cylinder are metering normally, the piston movement is within the maximum stroke and the over-limit protection bypass port will not be opened, so the flow rate can be accurately and dynamically metered. When a control error or equipment problem occurs and normal metering cannot be achieved, an excessive pressure difference is generated on both sides of the hydraulic cylinder, pushing the piston to open the over-limit protection bypass port, causing the bypass port to have a certain opening. This opening can be fed back through the LVDT, allowing the fluid on both sides of the hydraulic cylinder to flow through the bypass port, forming a conduction similar to a throttle port, and the pressure difference force generated is the spring force. The design of the over-limit protection bypass port avoids the phenomenon of the hydraulic cylinder pushing the cylinder and the flow path being blocked, and sets over-limit protection for metering control.

[0036] In order to further illustrate the reliability of the design and the effectiveness of flow measurement of this embodiment, the following Figure 3The modeling of the pump-controlled cylinder hydraulic circuit based on AMEsim software can show the specific physical structure of the pump-controlled cylinder circuit and reflect the flow of the measured flow inside the system. Components such as metering pumps, sensors, and oil sources are directly obtained from the hydraulic library and mechanical library, while the hydraulic cylinder is built using some modules in the HCD library and mechanical library to simulate the leakage inside the cylinder. At the same time, a compressible pressure body module is selected to connect the inlet and outlet of the metering pump with the oil chamber of the hydraulic cylinder to simulate the process of the metering pump sucking and discharging oil inside the hydraulic cylinder cavity. In addition, the speed of the metering pump cannot be directly obtained during the actual measurement process. This fact is also followed in the simulation model. The motor speed is used as a substitute when calculating the test flow. At the same time, considering the influence of inertia on the speed change, the moment of inertia and damping model are added between the metering pump and the motor. This example is aimed at the closed-loop control of the electric fuel pump flow. The geometric parameters of the above components are shown in Table 1:

[0037] Table 1 Main parameters of hydraulic system

[0038]

[0039] like Figure 4 The controller modeling based on Simulink uses a first-order inertial system to simulate the motor model, and adds a delay system between the metering pump and the fuel pump to represent the delay of the system reading and following. The flow rate is calculated by reading the speed of the metering pump and the displacement of the unloaded hydraulic cylinder. Figure 5 Figure 6 The results shown are the joint simulation results of AMESim and Simulink, where Figure 5 It can be seen that the specific adjustment process of the fuel metering device is that when the fuel command changes, the speed of the electric fuel pump changes, and the metering pump adjusts according to the speed change of the electric fuel pump. At this time, due to the different flow rates passing through the metering pump and the electric fuel pump, a pressure difference is generated on both sides of the no-load hydraulic cylinder, causing the piston to move, and then adjusting the speed of the metering pump to balance the pressure on both sides of the no-load hydraulic cylinder. Figure 6 It can be seen that although inertial filtering and leakage compensation are not performed, there will be certain errors in the measurement results when the pressure difference is large. However, it can be seen that the dynamic composite fuel metering device can accurately measure the flow rate of the electric fuel pump and has good dynamic performance.

[0040] The above descriptions are merely embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent structure or equivalent process transformation made using the contents of this specification and the drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A dynamic metering device based on coordinated control of flow of an electric fuel pump, characterized in that it comprises an electric fuel pump (1), a metering pump (2), an unloaded hydraulic cylinder (3), an over-limit protection bypass port (4), a two-way return spring (5), an LVDT (6), a piston (7), and a nozzle (8); wherein the metering pump (2) is connected in parallel with the unloaded hydraulic cylinder (3), the piston (7) is placed inside the unloaded hydraulic cylinder (3) and connected to the two-way return spring (5), the over-limit protection bypass port (4) is integrated outside the hydraulic cylinder (3), the LVDT (6) is installed at the end of the piston (7) rod, the inlet of the fuel metering device is connected to the electric fuel pump (1), and the outlet is connected to the nozzle (8); by measuring the speed (2) of the metering pump and the displacement of the piston (7), and establishing a leakage model, the flow rate is calculated according to the following formula (1), and the leakage amount is calculated according to formula (2), characterized in that The speed of the metering pump (2) is actively controlled based on the speed of the electric fuel pump (1) and the displacement of the piston (7), thereby ensuring the accuracy and real-time performance of measuring the fuel flow rate. Where L is the displacement of the metering pump, n is the speed of the metering pump, V is the speed of the piston in the hydraulic cylinder, π is the pi, D is the diameter of the piston, d is the diameter of the piston rod, γ is the leakage coefficient, ΔP is the pressure difference on both sides of the hydraulic cylinder, K is the stiffness of the bidirectional return spring, x is the displacement of the piston, M is the total mass of the piston, and a is the acceleration of the piston.

2. According to claim 1, a dynamic metering device based on coordinated control of the flow of an electric fuel pump is characterized in that the speed of the servo motor of the electric fuel pump (1) is used as a feedforward quantity, and the displacement of the piston (7) is used as a feedback quantity to perform closed-loop control on the speed of the metering pump (2), thereby improving the response speed of the metering pump, reducing the requirements for the size of the hydraulic cylinder during the metering process, and significantly widening the range of fuel metering, thereby better meeting the requirements of the closed-loop control of the electric fuel pump (1).

3. A dynamic metering device based on coordinated control of electric fuel pump flow according to claim 1, characterized in that An over-limit protection bypass port (4) is integrated on the unloaded hydraulic cylinder (3). During the flow metering process, even if the metering pump (2) is controlled incorrectly, the fluid can flow out through the over-limit protection bypass port (4), thereby preventing the piston from pushing against the cylinder and preventing the flow path from being blocked.

4. A dynamic metering device based on coordinated control of electric fuel pump flow according to claim 1, characterized in that A bidirectional return spring (5) is installed on the piston (7) inside the no-load hydraulic cylinder (3), that is, both sides of the piston (7) are connected to the left and right inner walls of the no-load hydraulic cylinder (3) through mechanical springs, and the compression length thereof is proportional to the pressure received. Its function is to always use the center position of the no-load hydraulic cylinder (3) as the equilibrium position of the piston (7), widen the measuring range of the fuel metering device, and provide external force to close the over-limit protection bypass port (4).

5. A dynamic metering method for a dynamic metering device based on coordinated flow control of an electric fuel pump according to claims 1-4, wherein the specific adjustment process of the dynamic metering method and the method for preventing piston-to-cylinder displacement is as follows: 1) When the electric fuel pump (1) is started and begins to supply fuel, the controller reads the speed of the electric fuel pump (1) through the speed sensor, obtains the speed instruction 1 of the metering pump (2) based on the displacement of the fuel pump (1) and the metering pump (2), and simultaneously reads the displacement measured by the LVDT (6) on the piston (7) in the unloaded hydraulic cylinder (3) and obtains the speed instruction 2 of the metering pump (2) through PID control. The controller outputs the sum of the speed instruction 1 and the speed instruction 2 as the speed instruction of the metering pump (2), and then feeds back the actual speed of the metering pump (2) through the speed sensor. Based on the stiffness of the bidirectional return spring (5) and the acceleration of the piston (7), the pressure difference on both sides of the unloaded hydraulic cylinder (3) can be calculated. The leakage flow rate is calculated by the constructed leakage model, making the metering more accurate. Under the condition of not exceeding the limit, the dynamic flow rate can be calculated based on the speed and displacement of the metering pump (2) and the displacement and speed of the piston (7) in the entire adjustment process, and the fuel flow rate is dynamically metered; 2) When the metering pump is controlled incorrectly or the equipment has problems, when the electric fuel pump (1) is started, the metering pump (2) cannot follow the speed and flow, and the unloaded hydraulic cylinder (3) will exceed the limit. The piston (7) moves until the over-limit protection bypass port (4) is opened, so that the flow that cannot pass through is discharged from the over-limit protection bypass port, avoiding the situation where the unloaded hydraulic cylinder (3) is blocked or the piston (7) pushes the cylinder. When the controller detects that the piston displacement exceeds the limit, it will issue an error alarm, and the equipment needs to be checked. When the problem is solved, since the over-limit protection bypass port (4) balances the pressure difference at both ends, the two-way return spring (5) will actively close the over-limit protection bypass port (4), and correct metering pump control and fuel metering are performed.

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