Control method and control system for injection quantity of methanol dual-fuel engine

Abstract

The invention discloses a control method and a control system for the injection quantity of a methanol dual-fuel engine. The control method mainly comprises the following steps: firstly, acquiring fuel temperature, fuel rail pressure, fuel pressure difference, basic injection rate and required fuel injection quantity; obtaining a first correction coefficient according to the fuel oil temperature; according to the fuel rail pressure and the fuel pressure difference, a second correction coefficient is obtained from the differential pressure rail pressure correction coefficient MAP; the first correction coefficient and the second correction coefficient are used for correcting the basic injection rate to obtain a flow correction coefficient, and the flow correction coefficient is equal to the product of the basic injection rate, the first correction coefficient and the second correction coefficient; the power-up time is obtained according to the required fuel injection amount and the flow correction coefficient; and controlling the fuel injector according to the power-up time. Therefore, the power-up time can be controlled through three physical quantities, namely the fuel pressure difference, the fuel rail pressure and the alternative fuel temperature, so that more accurate alternative fuel supply is realized, and the performance of the methanol dual-fuel engine is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and particularly to a control method and a control system for the injection quantity of a methanol dual-fuel engine. Background Art

[0002] In a methanol dual-fuel engine, accurately controlling the injection quantity of the alternative fuel is crucial for the fuel substitution rate, which affects the combustion stability, power performance, economy and even the NVH level of the engine. The demand for the alternative fuel under different working conditions is obtained through actual calibration. The engine electronic control system controls the energization time to open and close the alternative fuel injector, thereby realizing the injection of different calibrated quantities of the alternative fuel under different working conditions.

[0003] In the existing methanol dual-fuel control system, the energization time is obtained by dividing the demand for the alternative fuel by the flow correction coefficient, and this flow correction coefficient is only related to two physical quantities, namely the pressure difference of the alternative fuel and the temperature of the alternative fuel. However, in actual control, due to the structure and working principle of the alternative fuel system itself, the energization time is affected by three physical quantities, namely the rail pressure of the alternative fuel, the pressure difference of the alternative fuel and the temperature of the alternative fuel. The calculation method of the flow coefficient that only includes two physical quantities, namely the pressure difference of the alternative fuel and the temperature of the alternative fuel, cannot meet the precise control of the alternative fuel quantity, resulting in difficulty in further optimizing the consistency of the alternative fuel and the performance of the engine. Summary of the Invention

[0004] Aiming at the above deficiencies, the technical problem to be solved by the present invention is: to provide a control method and a control system for the injection quantity of a methanol dual-fuel engine, which can control the energization time through three physical quantities, namely the fuel pressure difference, the fuel rail pressure and the fuel temperature, thereby realizing more precise supply of the alternative fuel and optimizing the performance of the methanol dual-fuel engine.

[0005] To solve the above technical problem, the technical solution of the present invention is:

[0006] A control method for the injection quantity of a methanol dual-fuel engine includes the following steps:

[0007] S1. Obtain the fuel temperature, the fuel rail pressure, the fuel pressure difference, the basic injection rate and the required fuel injection quantity;

[0008] S2. Obtain a first correction coefficient according to the fuel temperature;

[0009] S3. Obtain a second correction coefficient from the calibrated pressure difference-rail pressure correction coefficient MAP according to the fuel rail pressure and the fuel pressure difference;

[0010] S4. Use the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain a flow correction coefficient, and the flow correction coefficient is equal to the product of the basic injection rate, the first correction coefficient and the second correction coefficient;

[0011] S5. Obtain the power-on time according to the required fuel injection quantity and the flow correction coefficient.

[0012] S6. Control the fuel injector according to the power-on time.

[0013] Preferably, the S1 further includes:

[0014] Obtain the supercharging pressure.

[0015] Calculate the fuel pressure difference, where the fuel pressure difference = fuel rail pressure - supercharging pressure.

[0016] Preferably, the S2 includes: Obtain the first correction coefficient from the calibrated temperature correction coefficient curve according to the fuel temperature.

[0017] Preferably, obtaining the required fuel injection quantity in the S1 includes the following steps:

[0018] Obtain the engine speed, supercharging pressure, temperature after intercooling, and engine displacement.

[0019] Input the engine speed, pressure after intercooling, temperature after intercooling, and engine displacement into a pre-set fresh air calculation model to calculate the fresh air quantity.

[0020] Then input the engine speed and the fresh air quantity into a pre-set fuel injection quantity calculation model to calculate the required fuel injection quantity.

[0021] Preferably, when calibrating the differential rail pressure correction coefficient MAP, it includes the following steps:

[0022] Step 1. Construct a three-dimensional coordinate system, with the pressure difference as the X-axis, the fuel rail pressure as the Y-axis, and the second correction coefficient as the Z-axis.

[0023] Step 2. Keep the basic injection rate and the fuel rail pressure unchanged, change the engine speed and load, and obtain the corresponding supercharging pressure and the second correction coefficient.

[0024] Step 3. Adjust the fuel rail pressure, and repeat Step 2 until the differential rail pressure correction coefficient MAP is obtained.

[0025] A control system for the injection quantity of a methanol dual-fuel engine, comprising an electronic control unit and a parameter acquisition unit, a first correction unit, a second correction unit, and a flow coefficient correction unit that are electrically connected to the electronic control unit respectively; the parameter acquisition unit is used to acquire fuel temperature, fuel rail pressure, supercharging pressure, basic injection rate, and required fuel injection quantity; the first correction unit is used to obtain a first correction coefficient from a calibrated temperature correction coefficient curve according to the fuel temperature and transmit it to the flow coefficient correction unit; the second correction unit is used to calculate a fuel pressure difference according to the fuel rail pressure and the supercharging pressure, where the fuel pressure difference is equal to the difference between the fuel rail pressure and the supercharging pressure, and then obtain a second correction coefficient from a calibrated pressure difference-rail pressure correction coefficient MAP according to the fuel pressure difference and the fuel rail pressure, and transmit it to the flow coefficient correction unit; the flow coefficient correction unit uses the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain a flow coefficient correction, and then calculates the energization time by using the required fuel injection quantity and the flow coefficient correction, and transmits the energization time to the electronic control unit; the electronic control unit controls the fuel injector according to the energization time.

[0026] Preferably, the parameter acquisition unit includes a temperature detection unit and a pressure detection unit; the temperature detection unit is used to detect the methanol temperature and the temperature after intercooling, and transmit the corresponding temperature signals to the electronic control unit; the pressure detection unit is used to detect the fuel rail pressure and the supercharging pressure in the common rail pipe, and transmit the corresponding pressure signals to the electronic control unit; the electronic control unit then transmits the temperature signals and the pressure signals to the first correction unit, the second correction unit, and the flow coefficient correction unit.

[0027] Preferably, the parameter acquisition unit further includes a rotational speed detection unit, an engine displacement detection unit, and a fuel calculation unit; the rotational speed detection unit is used to detect the engine rotational speed; the engine displacement detection unit is used to detect the engine displacement; the fuel calculation unit is used to input the engine rotational speed, the pressure after intercooling, the supercharging pressure, and the engine displacement into a pre-set fresh air calculation model to calculate the fresh air quantity, and then transmit the engine rotational speed and the fresh air quantity to a pre-set fuel injection quantity calculation model to calculate the required fuel injection quantity.

[0028] Preferably, the temperature detection unit includes a methanol temperature sensor and a temperature sensor after intercooling, and the pressure detection unit includes a rail pressure detection sensor and a pressure sensor after intercooling; the methanol temperature sensor and the rail pressure detection sensor are installed on the common rail pipe; the temperature sensor after intercooling and the pressure sensor after intercooling are installed in the air cavity after intercooling.

[0029] Preferably, the system further includes a preset unit for calibrating a temperature correction coefficient curve and a differential pressure rail pressure correction coefficient MAP, and the preset unit is also used for presetting a fresh air calculation model and a fuel injection amount calculation model.

[0030] After adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0031] Since the control method and control system for the injection amount of the methanol dual-fuel engine of the present invention mainly obtain the fuel temperature, fuel rail pressure, fuel differential pressure, basic injection rate, and required fuel injection amount first; obtain the first correction coefficient according to the fuel temperature; obtain the second correction coefficient from the calibrated differential pressure rail pressure correction coefficient MAP according to the fuel rail pressure and fuel differential pressure; use the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain a flow correction coefficient, and the flow correction coefficient is equal to the product of the basic injection rate, the first correction coefficient, and the second correction coefficient; obtain the power-on time according to the required fuel injection amount and the flow correction coefficient; and control the fuel injector according to the power-on time. It can be seen that the control method and control system for the injection amount of the methanol dual-fuel engine of the present invention can control the power-on time through three physical quantities of fuel differential pressure, fuel rail pressure, and fuel temperature, thereby realizing a more precise supply of alternative fuel and optimizing the performance of the methanol dual-fuel engine. Description of the Drawings

[0032] Figure 1 is the logical relationship diagram of the control method for the injection amount of the methanol dual-fuel engine in the present invention;

[0033] Figure 2 is the schematic diagram of the control system for the injection amount of the methanol dual-fuel engine in the present invention;

[0034] In the figure: 1 - common rail pipe, 2 - post-intercooler air cavity, 3 - fuel injector, 4 - methanol temperature sensor, 5 - rail pressure detection sensor, 6 - post-intercooler temperature sensor, 7 - post-intercooler pressure sensor. Detailed Embodiments

[0035] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] It should be noted that in the description of the present invention, the terms indicating the direction or positional relationship such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the direction or positional relationship shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0037] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] The alternative fuel involved in the present invention refers to other types of energy that can replace traditional fuels (such as gasoline, diesel, etc.) and is used to drive an internal combustion engine or a similar power system. Common alternative fuels include methanol, ethanol, biodiesel, liquefied petroleum gas, compressed natural gas, etc.

[0039] The power-on time involved in the present invention refers to the length of time that the solenoid valve of the fuel injector is powered on, which directly controls the fuel injection amount. The power-on time is adjusted by the engine electronic control unit (ECU) according to the engine operating conditions (such as speed, load, temperature, etc.) to ensure appropriate fuel supply and maintain the efficient and stable operation of the engine.

[0040] The basic injection rate involved in the present invention refers to the injection rate of the fuel injector obtained by the fuel injector supplier under a certain environment by applying a specified supply pressure, which is an inherent characteristic of the injector under certain environmental conditions.

[0041] The alternative fuel injector involved in the present invention is connected to the alternative fuel common rail pipe at one end and has a nozzle at the other end, which extends into the intake manifold. There is a solenoid valve inside the injector, and the ECU powers on the solenoid valve to open the solenoid valve to achieve fuel injection.

[0042] The alternative fuel system in the present invention includes a fuel supply system, a fuel delivery pipe, a fuel common rail pipe, and a fuel injector. The fuel supply system is responsible for pumping the fuel out of the storage tank and pressurizing it to transport it into the common rail pipe. The common rail pressure is always maintained greater than the engine boost pressure so that the alternative fuel can be injected into the intake manifold through the injector.

[0043] In the present invention, the alternative fuel pressure difference is the difference between the alternative fuel rail pressure and the supercharging pressure. To enable the alternative fuel to be injected into the intake manifold, the rail pressure needs to be greater than the supercharging pressure, so there is a pressure difference. During the actual operation of the engine, the pressure difference fluctuates, and a pressure difference correction coefficient is required to calculate the reasonable power-on time.

[0044] It should be specifically noted that: in this application, the alternative fuel temperature is simply referred to as the fuel temperature, the alternative fuel rail pressure is simply referred to as the fuel rail pressure, and the alternative fuel pressure difference is simply referred to as the fuel pressure difference.

[0045] Embodiment 1:

[0046] As Figure 1 shown, a control method for the injection quantity of a methanol dual-fuel engine includes the following steps:

[0047] Step S1: Obtain the fuel temperature, fuel rail pressure, fuel pressure difference, basic injection rate, and required fuel injection quantity; in this embodiment, step S1 further includes obtaining the supercharging pressure; calculate the fuel pressure difference, where the fuel pressure difference = fuel rail pressure - supercharging pressure;

[0048] It should be noted that: the control method for the injection quantity of the methanol dual-fuel engine of the present invention can be applied to the control system for the injection quantity of the methanol dual-fuel engine described in Embodiment 2. Refer to Figure 2 , the fuel temperature can be detected by the methanol temperature sensor 4 provided on the common rail pipe 1, the fuel rail pressure can be detected by the rail pressure detection sensor 5 provided on the common rail pipe 1, the supercharging pressure can be detected by the post-intercooler pressure sensor 7 provided in the post-intercooler air chamber 2, the basic injection rate is a preset value, and the required fuel injection quantity can be a calibrated value or calculated according to the real-time working conditions of the engine.

[0049] Step S2: Obtain the first correction coefficient according to the fuel temperature;

[0050] Step S3: Obtain the second correction coefficient from the calibrated pressure difference rail pressure correction coefficient MAP according to the fuel rail pressure and fuel pressure difference;

[0051] Step S4: Use the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain the flow correction coefficient. The flow correction coefficient is equal to the product of the basic injection rate, the first correction coefficient, and the second correction coefficient; specifically, the flow correction coefficient = basic injection rate × first correction coefficient × second correction coefficient, where the first correction coefficient is related to the fuel temperature, and the second correction coefficient is related to the fuel pressure difference and fuel rail pressure. At this time, the flow correction coefficient is corrected in relation to three physical quantities: the fuel pressure difference, fuel rail pressure, and fuel temperature.

[0052] Step S5: Obtain the power-on time according to the required fuel injection quantity and the flow correction coefficient;

[0053] Specifically, the power-on time = required fuel injection quantity / flow correction coefficient, that is, the power-on time is equal to the required fuel injection quantity divided by the flow correction coefficient. Since the flow correction coefficient is corrected by three material quantities: fuel pressure difference, fuel rail pressure, and fuel temperature, the power-on time is accurately controlled.

[0054] Step S6: Control the fuel injector according to the power-on time.

[0055] The control method for the injection quantity of the methanol dual-fuel engine of the present invention mainly uses the real-time fuel temperature to determine a correction coefficient, and then uses the real-time fuel pressure difference and fuel rail pressure to determine another correction coefficient. Since the fuel pressure difference is the difference between the fuel rail pressure and the supercharging pressure, finally, the two correction coefficients are used to correct the flow correction coefficient simultaneously, obtaining a reasonable power-on time. Through the precise control of the power-on time, the accurate control of the corresponding fuel injection quantity is realized. It can be seen that by adopting the control method of the present invention, the flow correction coefficient can be corrected by three physical quantities: fuel temperature, fuel rail pressure, and fuel pressure difference, and the supply of alternative fuels can be realized more accurately to optimize the performance of the methanol dual-fuel engine; moreover, the control method of the present invention is simple to operate and easy to implement.

[0056] As Figure 1 shown, the step S2 of the control method for the injection quantity of the methanol dual-fuel engine in this embodiment specifically includes:

[0057] According to the fuel temperature, look up the first correction coefficient from the calibrated temperature correction coefficient curve.

[0058] The temperature correction coefficient curve involved in the present invention is calibrated as follows:

[0059] The basic injection rate of the methanol injector under a certain fixed methanol supply pressure (fuel rail pressure) can be obtained by the methanol injector supplier through a pressure test and simulation injection test on the factory test bench. Then, by changing the methanol supply pressure (fuel rail pressure) and methanol temperature (fuel temperature), the corresponding temperature correction coefficient curve is obtained. The abscissa is the fuel temperature, and the ordinate is the first correction coefficient. During actual use, the corresponding first correction coefficient at different fuel temperatures is queried.

[0060] The differential pressure rail pressure correction coefficient MAP of the present invention is calibrated as follows:

[0061] Step 1: Construct a three-dimensional coordinate system, with the pressure difference as the X-axis, the fuel rail pressure as the Y-axis, and the second correction coefficient as the Z-axis;

[0062] Step 2: Keep the basic injection rate and fuel rail pressure unchanged, change the engine speed and load, and obtain the corresponding supercharging pressure and second correction coefficient;

[0063] Step 3: Adjust the fuel rail pressure, and then repeat Step 2 until the differential pressure rail pressure correction coefficient MAP is obtained.

[0064] As can be seen from the above steps, in the differential pressure rail pressure correction coefficient MAP of the present invention, the X-axis is the differential pressure, the Y-axis is the rail pressure, and the Z-axis is the correction coefficient; combined with the basic injection rate provided by the manufacturer, fixing a certain fuel rail pressure A, changing the engine operating speed and load, the second correction coefficient between the fuel rail pressure and the boost pressure under the fuel rail pressure A is obtained; then when the fuel rail pressure is adjusted to B, continue to change the engine operating speed and load to obtain the second correction coefficient between the fuel rail pressure and the boost pressure under the fuel rail pressure B; through multiple adjustments under the working fuel rail pressure allowed by the injector, the accurate differential pressure rail pressure correction coefficient MAP suitable for the engine under different operating conditions and different fuel rail pressures can be obtained. It can be seen that the present invention can control the fuel injection quantity more accurately and optimize the calculation method of the flow correction coefficient.

[0065] In the control method of the methanol dual-fuel engine injection quantity in this embodiment, in step S1 of obtaining the required fuel injection quantity, the following steps are included:

[0066] Obtain the engine speed, boost pressure, temperature after intercooling, and engine displacement.

[0067] Input the engine speed, pressure after intercooling, temperature after intercooling, and engine displacement into a pre-set fresh air calculation model to calculate the fresh air quantity; the fresh air calculation model can be calculated using the following formula, fresh air quantity calculation method: (speed × displacement / (stroke number / 2)) × standard state air density × (temperature and pressure correction after intercooling).

[0068] Then input the engine speed and fresh air quantity into a pre-set fuel injection quantity calculation model to calculate the required fuel injection quantity. The fuel injection quantity calculation model can determine the actual load of the engine based on the engine speed and fresh air quantity. By measuring with a bench actual fuel consumption meter, the actual fuel injection quantity can be obtained, and this value is calibrated into the electronic control unit (ECU) as the basic value of the required fuel injection quantity. Then, through the deviation between the speed and the set speed, the corrected injection quantity during speed fluctuation is obtained through PID calculation. The two added together are the required fuel injection quantity.

[0069] In summary, based on the temperature correction coefficient curve, the present invention adds a differential pressure rail pressure correction coefficient MAP composed of fuel differential pressure and fuel rail pressure, realizes the control of the power-on time through three physical quantities of fuel differential pressure, fuel rail pressure, and fuel temperature, so as to more accurately realize the supply of alternative fuels and optimize the performance of the methanol dual-fuel engine.

[0070] Embodiment 2:

[0071] As Figure 2As shown, a control system for the injection quantity of a methanol dual-fuel engine can apply the control method described in Embodiment 1. The control system of this embodiment includes an electronic control unit and a parameter acquisition unit, a first correction unit, a second correction unit, a flow coefficient correction unit, and a preset unit that are electrically connected to the electronic control unit respectively. The preset unit is used to calibrate the temperature correction coefficient curve and the pressure difference-rail pressure correction coefficient MAP, and the preset unit is used to preset the fresh air calculation model and the fuel injection quantity calculation model.

[0072] In the present invention, the parameter acquisition unit is used to acquire the fuel temperature, fuel rail pressure, supercharging pressure, basic injection rate, and required fuel injection quantity; the parameter acquisition unit transmits the corresponding electrical signals to the electronic control unit, and the electronic control unit then transmits them to the first correction unit, the second correction unit, and the flow coefficient correction unit.

[0073] In this embodiment, the parameter acquisition unit includes a temperature detection unit and a pressure detection unit; the temperature detection unit is used to detect the methanol temperature and the temperature after the intercooler, and transmits the corresponding temperature signals to the electronic control unit; the pressure detection unit is used to detect the fuel rail pressure and the supercharging pressure in the common rail pipe 1, and transmits the corresponding pressure signals to the electronic control unit; the electronic control unit then transmits the temperature signals and / or pressure signals to the first correction unit, the second correction unit, and / or the flow coefficient correction unit.

[0074] In this embodiment, the temperature detection unit includes a methanol temperature sensor 4 and a temperature sensor 6 after the intercooler, and the pressure detection unit includes a rail pressure detection sensor 5 and a pressure sensor 7 after the intercooler; the methanol temperature sensor 4 and the rail pressure detection sensor 5 are installed on the common rail pipe 1; the temperature sensor after the intercooler and the pressure sensor 7 after the intercooler are installed in the air chamber 2 after the intercooler.

[0075] In this embodiment, the parameter acquisition unit further includes a rotation speed detection unit, an engine displacement detection unit, and a fuel calculation unit that are electrically connected; the rotation speed detection unit is used to detect the engine rotation speed; the engine displacement detection unit is used to acquire the engine displacement; the fuel calculation unit is used to input the engine rotation speed, the pressure after the intercooler, the supercharging pressure, and the engine displacement into the preset fresh air calculation model to calculate the fresh air quantity, and then transmits the engine rotation speed and the fresh air quantity to the preset fuel injection quantity calculation model to calculate the required fuel injection quantity.

[0076] It should be noted that the fresh air calculation model can be calculated using the following formula. The calculation method of the fresh air volume is: (rotation speed × displacement / (stroke number / 2)) × air density under standard conditions × (temperature and pressure correction after intercooling). The fuel injection volume calculation model can determine the actual load of the engine using the rotation speed and the fresh air volume. By measuring with a bench actual fuel consumption meter, the actual fuel injection volume can be obtained. This value is calibrated into the ECU as the basic value of the required fuel injection volume. Then, through the deviation between the rotation speed and the set rotation speed, and through PID calculation, the corrected injection volume during rotation speed fluctuation is obtained. The sum of the two is the required fuel injection volume.

[0077] In the present invention, the first correction unit is used to obtain a first correction coefficient from the calibrated temperature correction coefficient curve according to the fuel temperature and transmit it to the flow coefficient correction unit.

[0078] In the present invention, the second correction unit is used to calculate the fuel pressure difference according to the fuel rail pressure and the supercharging pressure. The fuel pressure difference is equal to the difference between the fuel rail pressure and the supercharging pressure. Then, according to the fuel pressure difference and the fuel rail pressure, a second correction coefficient is obtained from the calibrated pressure difference - rail pressure correction coefficient MAP and transmitted to the flow coefficient correction unit.

[0079] In the present invention, the flow coefficient correction unit uses the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain the flow coefficient correction. Specifically, the flow coefficient correction = basic injection rate × first correction coefficient × second correction coefficient. Refer to Figure 1 , and then calculate the energization time using the required fuel injection volume and the flow coefficient correction. Specifically, the energization time = required fuel injection volume / flow coefficient correction, and transmit the energization time to the electronic control unit; the electronic control unit controls the fuel injector 3 according to the energization time.

[0080] As Figure 2 shown, in the control system for the injection volume of the methanol dual - fuel engine of the present invention, methanol is supplied from an external fuel supply device to the methanol common rail pipe 1, and then the methanol in the common rail pipe 1 is transported to the methanol injectors (fuel injector 3) installed on the intake manifolds of each cylinder.

[0081] The rail pressure detection sensor 5 on the common rail pipe 1 detects the real - time fuel rail pressure and transmits it to the electronic control unit. The methanol temperature sensor 4 on the common rail pipe 1 detects the real - time fuel temperature and transmits it to the electronic control unit. The electronic control unit transmits the fuel rail pressure and the fuel temperature to the required units respectively, such as transmitting them to the first correction unit, the second correction unit, and / or the flow coefficient correction unit to obtain the corresponding first correction coefficient.

[0082] The post - intercooling temperature sensor 6 of the post - intercooling air chamber 2 detects the real - time post - intercooling temperature and transmits it to the electronic control unit. The post - intercooling pressure sensor 7 detects the real - time post - intercooling pressure (boost pressure) and transmits it to the electronic control unit. The electronic control unit transmits the boost pressure to the second correction unit to obtain the corresponding second correction coefficient.

[0083] The parameter acquisition unit calculates the fresh air quantity according to the engine speed, engine displacement, etc., and then calculates the required fuel injection quantity according to the engine speed and the fresh air quantity, and transmits the required fuel injection quantity to the flow coefficient correction unit. After being corrected by the flow coefficient correction unit, the real - time power - on time is obtained, and the fuel injector 3 is controlled by using this power - on time.

[0084] It can be seen that for the control system of the injection quantity of the methanol dual - fuel engine of the present invention, first, the first correction coefficient is obtained by using the fuel temperature. Then, the fuel pressure difference is calculated by using the boost pressure and the fuel rail pressure, and the second correction coefficient is obtained by looking up in the pressure - difference rail - pressure correction coefficient MAP. Then, the first correction coefficient and the second correction coefficient are used to correct the flow correction coefficient to calculate a reasonable and accurate power - on time. Finally, the fuel injection quantity is accurately controlled by using this power - on time, thereby optimizing the performance of the methanol dual - fuel engine. Therefore, the control system of the present invention realizes the control of the power - on time through three physical quantities: fuel pressure difference, fuel rail pressure, and fuel temperature, so as to more accurately realize the supply of alternative fuels.

[0085] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for the injection quantity of a methanol dual-fuel engine, characterized in that It includes the following steps: S1. Obtain the fuel temperature, fuel rail pressure, fuel pressure difference, basic injection rate, and required fuel injection quantity; S2. Obtain the first correction coefficient according to the fuel temperature; S3. Obtain the second correction coefficient from the calibrated pressure difference - rail pressure correction coefficient MAP according to the fuel rail pressure and fuel pressure difference; S4. Use the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain a flow correction coefficient, where the flow correction coefficient is equal to the product of the basic injection rate, the first correction coefficient, and the second correction coefficient; S5. Obtain the power - on time according to the required fuel injection quantity and the flow correction coefficient; S6. Control the fuel injector according to the power - on time.

2. The control method for the injection quantity of a methanol dual-fuel engine according to claim 1, wherein The step S1 further includes: Obtain the boost pressure; Calculate the fuel pressure difference, where the fuel pressure difference = fuel rail pressure - boost pressure.

3. The control method for the injection quantity of a methanol dual-fuel engine according to claim 1, characterized in that, The step S2 includes: Obtain the first correction coefficient by looking up from the calibrated temperature correction coefficient curve according to the fuel temperature.

4. The control method for the injection quantity of a methanol dual-fuel engine according to claim 1, characterized in that, Obtaining the required fuel injection quantity in the step S1 includes the following steps: Obtain the engine speed, boost pressure, temperature after inter - cooler, and engine displacement; Input the engine speed, pressure after inter - cooler, temperature after inter - cooler, and engine displacement into a pre - set fresh air calculation model to calculate the fresh air quantity; Then input the engine speed and the fresh air quantity into a pre - set fuel injection quantity calculation model to calculate the required fuel injection quantity.

5. The control method for the injection quantity of a methanol dual-fuel engine according to claim 2, characterized in that, When calibrating the pressure difference - rail pressure correction coefficient MAP, it includes the following steps: Step 1. Construct a three - dimensional coordinate system, with the pressure difference as the X - axis, the fuel rail pressure as the Y - axis, and the second correction coefficient as the Z - axis; Step 2. Keep the basic injection rate and the fuel rail pressure unchanged, change the engine speed and load, and obtain the corresponding boost pressure and the second correction coefficient; Step 3. Adjust the fuel rail pressure, and repeat Step 2 until the pressure difference - rail pressure correction coefficient MAP is obtained.

6. A control system for the injection quantity of a methanol dual-fuel engine, characterized in that, It includes an electronic control unit and a parameter acquisition unit, a first correction unit, a second correction unit, and a flow coefficient correction unit that are electrically connected to the electronic control unit respectively; The parameter acquisition unit is used to obtain the fuel temperature, fuel rail pressure, boost pressure, basic injection rate, and required fuel injection quantity; The first correction unit is used to obtain the first correction coefficient from the calibrated temperature correction coefficient curve according to the fuel temperature and transmit it to the flow coefficient correction unit; The second correction unit is used to calculate the fuel pressure difference according to the fuel rail pressure and the boost pressure, where the fuel pressure difference is equal to the difference between the fuel rail pressure and the boost pressure, and then obtain the second correction coefficient by looking up from the calibrated pressure difference - rail pressure correction coefficient MAP according to the fuel pressure difference and the fuel rail pressure, and transmit it to the flow coefficient correction unit; The flow coefficient correction unit uses the first correction coefficient and the second correction coefficient to correct the basic injection rate to obtain a flow coefficient correction, then calculates the power - on time using the required fuel injection quantity and the flow coefficient correction, and transmits the power - on time to the electronic control unit; The electronic control unit controls the fuel injector according to the power - on time.

7. The control system for the injection quantity of a methanol dual-fuel engine according to claim 6, characterized in that, The parameter acquisition unit includes a temperature detection unit and a pressure detection unit; The temperature detection unit is used to detect the methanol temperature and the temperature after inter - cooler, and transmit the corresponding temperature signals to the electronic control unit; The pressure detection unit is used to detect the fuel rail pressure and the supercharging pressure in the common rail pipe, and transmit the corresponding pressure signals to the electronic control unit; The electronic control unit then transmits the temperature signal and the pressure signal to the first correction unit, the second correction unit and the flow coefficient correction unit.

8. The control system for the injection quantity of a methanol dual-fuel engine according to claim 7, characterized in that, The parameter acquisition unit further includes a rotational speed detection unit, an engine displacement detection unit and a fuel calculation unit; The rotational speed detection unit is used to detect the engine rotational speed; The engine displacement detection unit is used to detect the engine displacement; The fuel calculation unit is used to input the engine rotational speed, the pressure after the intercooler, the supercharging pressure and the engine displacement into a pre-set fresh air calculation model to calculate the fresh air quantity, and then transmit the engine rotational speed and the fresh air quantity to a pre-set fuel injection quantity calculation model to calculate the required fuel injection quantity, and transmit it to the electronic control unit, and the electronic control unit then transmits it to the flow coefficient correction unit.

9. The control system for the injection quantity of a methanol dual-fuel engine according to claim 7, characterized in that, The temperature detection unit includes a methanol temperature sensor and a temperature sensor after the intercooler, and the pressure detection unit includes a rail pressure detection sensor and a pressure sensor after the intercooler; The methanol temperature sensor and the rail pressure detection sensor are installed on the common rail pipe; The temperature sensor after the intercooler and the pressure sensor after the intercooler are installed in the air cavity after the intercooler.

10. The control system for the injection quantity of a methanol dual-fuel engine according to claim 8, characterized in that, The system further includes a pre-setting unit, which is used to calibrate the temperature correction coefficient curve and the differential pressure-rail pressure correction coefficient MAP, and the pre-setting unit is also used to pre-set the fresh air calculation model and the fuel injection quantity calculation model.

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