A small flow fuel precise control method

Abstract

This invention discloses a method for precise control of low-flow-rate fuel. It involves real-time measurement of fuel pressure and temperature, with the control module calculating fuel density and viscosity based on these parameters. The theoretical flow rate is then calculated and compared with the target flow rate. Finally, a control algorithm drives the flow regulation mechanism to achieve precise control. This method solves the problem of insufficient accuracy caused by environmental parameters in traditional low-flow-rate control. It offers advantages such as simple and convenient control, making it suitable for low-flow-rate, high-precision fluid control applications. Furthermore, it boasts advantages such as high control accuracy, fast response speed, and strong environmental adaptability.

Description

Technical Field

[0001] This invention belongs to the field of engine technology, specifically relating to a method for precise control of low-flow fuel. Background Technology

[0002] Traditional low-flow fuel control methods often rely on mechanical valves or simple volumetric calculations, which have the following drawbacks: 1) The physical properties of fuel, such as the effects of changes in viscosity and density with pressure and temperature on flow rate, were not taken into account, resulting in control accuracy deviations of more than 15% under different operating conditions.

[0003] 2) Using a fixed coefficient to calculate flow rate cannot compensate for the influence of environmental parameters, especially in high-pressure and wide-temperature-range (-40℃ to 70℃) scenarios where the error is significant.

[0004] 3) The lack of a real-time feedback correction mechanism makes it difficult to meet the precise control requirements of modern precision systems for fuel injection quantity and combustion efficiency.

[0005] Furthermore, modern small turbojet engines and pulse engines require a short time to achieve stable start-up, while also meeting the requirements of high altitude and wide temperature ranges during the start-up process. Precise fuel flow control is crucial to adapt to the low-flow requirements of turbojet engines. Traditional open-loop control methods cannot meet these requirements; therefore, a real-time, effective, and simple method for precise low-flow fuel control is urgently needed. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a method for precise control of low-flow-rate fuel. It involves real-time measurement of fuel pressure and temperature, with the control module calculating fuel density and viscosity based on these parameters. This theoretical flow rate is then calculated and compared with the target flow rate. Finally, a control algorithm drives the flow regulation mechanism to achieve precise control. This method solves the problem of insufficient accuracy caused by environmental parameters in traditional low-flow-rate control. It offers advantages such as simple and convenient control, making it suitable for low-flow-rate, high-precision fluid control applications. Furthermore, it boasts advantages such as high control accuracy, fast response speed, and strong environmental adaptability.

[0007] The technical solution adopted by this invention to solve its technical problem is as follows: Step 1: Construct a low-flow fuel control system; The low-flow fuel control system includes a control module, a fuel tank, a fuel pump, a pressure-temperature composite sensor, and a fuel injector outlet. The fuel tank draws fuel from the fuel pump and outputs it to the fuel injector outlet via the fuel line; the pressure-temperature composite sensor is installed on the fuel line at the front end of the fuel injector outlet; the control module is connected to the pressure-temperature composite sensor and the fuel pump. The control module has a built-in flow calculation algorithm and control algorithm, and outputs a pulse width modulation (PWM) signal to control the speed of the fuel pump. Step 2: Modeling fuel physical parameters; Fuel density calculation: Based on the fuel state equation, establish the functional relationship between fuel density and temperature. (1) In the formula, Fuel density in relation to temperature; fuel temperature coefficient , The density of aviation kerosene at 15°C; Step 3: Flow rate theoretical calculation; Under the conditions of a fixed structure in a low-flow fuel control system and a determined pipeline outlet diameter, the theoretical flow rate formula is: (2) In the formula, Theoretical fuel flow rate, Fuel flow coefficient; The pressure difference of the fluid after the fuel pump P_out is the ambient pressure, and P is the fuel pressure; Step 4: Flow coefficient calibration; Under the same fuel supply system, the fuel flow rate at different temperatures and pressures is tested in real time, and the fuel flow coefficient is calculated according to the theoretical flow formula. Then, the arithmetic mean of the fuel flow coefficients at different temperatures and pressures is the fuel flow coefficient of the small flow fuel control system. Step 5: Fuel pressure and temperature data acquisition; A pressure-temperature composite sensor is used to measure fuel pressure and temperature. The formulas for calculating fuel pressure and temperature are as follows: (3) (4) In the formula and These are the pressure voltage and temperature voltage sampled by the pressure-temperature composite sensor, respectively. , All of these are fixed coefficients for the pressure signal of the pressure-temperature composite sensor. , All are fixed coefficients for the temperature signal of the pressure-temperature composite sensor; Step 6: Fuel Regulation Control Model; The control module receives fuel pressure and temperature data, controls the fuel pump output through PWM signals, and thus controls the fuel flow rate. Use the pump voltage conversion The formula for using PWM signals instead of PWM signals for control is: (5) In the formula The measured power supply voltage, Pulse width; The formula for calculating fuel flow rate is as follows: (6) In the formula, For target pressure, This serves as a reference upper limit for pressure control. This serves as a reference lower limit for pressure control. The empirical coefficient for the fuel pump, It is a control cycle. To convert pump voltage The correction amount.

[0008] Preferably, the control module has a control cycle of 1ms, and performs pressure and temperature composite sensor sampling and fuel pump voltage calculation in each cycle; and sends current status data every 10ms or 100ms.

[0009] Preferably, the microprocessor of the control module has a main frequency of ≥100MHz.

[0010] Preferably, the control module controls the speed of the fuel pump with a control accuracy of ±10 rpm.

[0011] Preferably, the fuel pump is a precision gear oil pump with a volumetric efficiency of over 95%, a minimum displacement of 0.01 mL / r, and a gear blade tip clearance with micron-level precision and a tolerance of ±0.001 mm.

[0012] Preferably, the density of the aviation kerosene at 15°C is... The value is 0.78 kg / m 3 .

[0013] Preferably, the empirical coefficient of the fuel pump Take 8-15.

[0014] Preferably, the control algorithm is a PID control algorithm.

[0015] The beneficial effects of this invention are as follows: This invention is the first to incorporate the effects of pressure and temperature on fuel density and viscosity into the flow control model, overcoming the limitations of traditional single-parameter control. By calibrating the pressure-temperature correction coefficient with the actual flow coefficient, calculation accuracy is ensured under different operating conditions. Combining PID regulation of the fuel pump speed with predictive real-time closed-loop control of the flow model, the control cycle is less than 10ms, and the response speed is improved by more than three times. The overall device has a simple structure, small size, and reduced cost, while being easy to install and operate, meeting the needs of miniaturized applications. Through built-in control algorithms and programs, the control module can automatically calculate and adjust the flow rate based on pressure and temperature data, eliminating the need for manual operation and additional adjustment equipment, achieving convenient and automated low-flow control. The low-flow control method based on pressure and temperature correction is suitable for the starting process of micro turbojet engines, meeting the application requirements of engines in different environments and providing a convenient control solution for reliable engine starting. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the low-flow fuel control system of the present invention.

[0017] Figure reference numerals: 1. Control module; 2. Fuel tank; 3. Fuel pump; 4. Pressure-temperature composite sensor; 5. Fuel injector outlet. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] This invention provides a method for precise control of low-flow fuel, which achieves flow control accuracy within ±2% by coupling real-time pressure and temperature measurements with a fluid dynamics model.

[0020] Reference Figure 1 This invention designs a low-flow fuel control system, which is used in the fuel supply control system of a small turbojet engine.

[0021] Fuel is drawn from the fuel tank, pressurized by the fuel pump, and then enters the fuel supply line of the turbojet engine. A fuel circuit test point is designed in the fuel pump line to monitor the fuel pressure and temperature upstream of the injector outlet in real time. The control program inside the control module controls the small flow rate of fuel.

[0022] 1. Design of a low-flow fuel control system; a) Sensor Module: The pressure sensor and temperature sensor are combined into one, designed as a pressure-temperature composite sensor. The pressure sensor has an accuracy of ±0.1%FS, a response time of 5ms, and acquires fuel pressure P in real time, in Pa. The temperature sensor has an accuracy of ±0.5℃ and acquires fuel temperature T in real time, in K.

[0023] b) Control Module: Microprocessor with a main frequency ≥100MHz, built-in flow calculation algorithm and PID control algorithm. Outputs PWM signal to control the speed of the fuel pump, with a speed control accuracy of ±10rpm.

[0024] c) Execution module: Precision gear oil pump with a volumetric efficiency of over 95%, a minimum displacement of 0.01 mL / r, and micron-level precision for gear diameter and gear blade tip clearance, with a tolerance of ±0.001 mm.

[0025] 2. Core algorithm flow; Step 1: Modeling fuel physical parameters; Fuel density calculation: Based on the fuel state equation, establish the functional relationship between density and temperature. (1) Step 2: Flow rate theoretical calculation; Under the conditions of a fixed structure in a low-flow fuel control system and a determined pipeline outlet diameter, the theoretical flow rate formula is: (2) Step 3: Flow coefficient calibration; By measuring fuel flow rates at different temperatures and pressures in an actual flow system, the fuel flow coefficient is calculated using the flow formula. For example, measured data shows a calibration coefficient of 0.255 at 0.2 MPa, 0.249 at 0.4 MPa, and 0.240 at 0.5 MPa. The arithmetic mean of these flow coefficients under different conditions is then calculated, resulting in a fuel flow coefficient of 0.248 for the system.

[0026] Step 4: Fuel pressure and temperature data acquisition; The voltage signals output by the fuel pressure and temperature sensors after the fuel pump are linearly related to the measured actual fuel pressure and temperature. These signals can be directly acquired by the microcontroller's AD converter and used to calculate the current fuel pressure and temperature in real time. The formulas for fuel pressure and temperature are as follows: (3) (4) Step 5: Fuel regulation control model; The control module receives commands and information from the upper level via a serial port, provides feedback on the current operating status of the fuel system, and controls the fuel pump output through PWM signals, thereby controlling the fuel flow. When performing PWM control, if pulse width... To control the output power of the fuel pump, which is significantly affected by changes in the power supply voltage, a method based on the pump voltage is used. pump Replace pulse width To perform control, the calculation formula is: (5) Within the normal fuel flow range of the engine, the target pressure after the pump is calculated based on the target flow rate, and then the conversion voltage of the fuel pump is adjusted according to the relationship between the target pressure and the current pressure, thereby precisely controlling the target flow rate.

[0027] Convert pump voltage pump The formula for calculating the correction amount is as follows: (6) Based on the characteristics of the fuel pump and through actual verification, the coefficients in equation (6) The value is determined to be 12.

[0028] This invention has been successfully applied to the fuel supply control of an engine and to an aircraft, enabling precise engine control and maintaining a remarkably stable low-flow fuel output across different temperature ranges and altitudes, demonstrating significant application value. It boasts advantages such as high control accuracy (±2%), fast response speed (≤10ms), and strong environmental adaptability.

Claims

1. A method for precise control of low-flow fuel, characterized in that, Includes the following steps: Step 1: Construct a low-flow fuel control system; The low-flow fuel control system includes a control module, a fuel tank, a fuel pump, a pressure-temperature composite sensor, and a fuel injector outlet. The fuel tank draws fuel from the fuel pump and outputs it to the fuel injector outlet via the fuel line; the pressure-temperature composite sensor is installed on the fuel line at the front end of the fuel injector outlet; the control module is connected to the pressure-temperature composite sensor and the fuel pump. The control module has a built-in flow calculation algorithm and control algorithm, and outputs a pulse width modulation (PWM) signal to control the speed of the fuel pump. Step 2: Modeling fuel physical parameters; Fuel density calculation: Based on the fuel state equation, establish the functional relationship between fuel density and temperature. （1） In the formula, Fuel density in relation to temperature; fuel temperature coefficient , The density of aviation kerosene at 15°C; Step 3: Flow rate theoretical calculation; Under the conditions of a fixed structure in a low-flow fuel control system and a determined pipeline outlet diameter, the theoretical flow rate formula is: （2） In the formula, Theoretical fuel flow rate, Fuel flow coefficient; The pressure difference of the fluid after the fuel pump P_out is the ambient pressure, and P is the fuel pressure; Step 4: Flow coefficient calibration; Under the same fuel supply system, the fuel flow rate at different temperatures and pressures is tested in real time, and the fuel flow coefficient is calculated based on the theoretical flow rate formula. Then, the arithmetic mean of the fuel flow coefficients at different temperatures and pressures is the fuel flow coefficient of the small flow fuel control system. Step 5: Fuel pressure and temperature data acquisition; A pressure-temperature composite sensor is used to measure fuel pressure and temperature. The formulas for calculating fuel pressure and temperature are as follows: (3) (4) In the formula and These are the pressure voltage and temperature voltage sampled by the pressure-temperature composite sensor, respectively. , All of these are fixed coefficients for the pressure signal of the pressure-temperature composite sensor. , All are fixed coefficients for the temperature signal of the pressure-temperature composite sensor; Step 6: Fuel Regulation Control Model; The control module receives fuel pressure and temperature data, controls the fuel pump output through PWM signals, and thus controls the fuel flow rate. Use the pump voltage conversion The formula for using PWM signals instead of PWM signals for control is: (5) In the formula The measured power supply voltage, Pulse width; The formula for calculating fuel flow rate is as follows: (6) In the formula, For target pressure, This serves as a reference upper limit for pressure control. This serves as a reference lower limit for pressure control. The empirical coefficient for the fuel pump, It is a control cycle. To convert pump voltage The correction amount.

2. The method for precise control of low-flow fuel according to claim 1, characterized in that, The control module has a control cycle of 1ms, during which pressure and temperature composite sensor sampling and fuel pump voltage calculation are performed; current status data is sent every 10ms or 100ms.

3. The method for precise control of low-flow fuel according to claim 1, characterized in that, The microprocessor of the control module has a main frequency of ≥100MHz.

4. The method for precise control of low-flow fuel according to claim 1, characterized in that, The control module controls the speed of the fuel pump with a control accuracy of ±10 rpm.

5. The method for precise control of low-flow fuel according to claim 1, characterized in that, The fuel pump is a precision gear oil pump with a volumetric efficiency of over 95%, a minimum displacement of 0.01 mL / r, and a gear blade tip clearance with micron-level precision and a tolerance of ±0.001 mm.

6. The method for precise control of low-flow fuel according to claim 1, characterized in that, The density of aviation kerosene at 15°C The value is 0.78 kg / m 3 .

7. The method for precise control of low-flow fuel according to claim 1, characterized in that, The empirical coefficient of the fuel pump Take 8-15.

8. The method for precise control of low-flow fuel according to claim 1, characterized in that, The control algorithm is a PID control algorithm.

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