A fuel injection control method for a non-road engine using a low-carbon clean alternative fuel

Abstract

The present invention relates to engine technology, and in particular to a fuel injection control method for a low-carbon clean alternative fuel non-road engine. The present invention determines the operating state of the engine and uses different parameter strategies to adjust the fuel injection amount according to different states, thereby meeting the power and economy of the low-carbon clean alternative fuel non-road engine, reducing the NOX and PM emissions of the engine, and taking into account the safety of the engine, thereby effectively improving the comprehensive performance of the engine.

Description

Technical Field

[0001] The invention relates to engine technology, in particular to a fuel injection control method for a low-carbon clean alternative fuel non-road engine. Background Art

[0002] Diesel engines are widely used for their high thermal efficiency, low fuel consumption, strong power, reliability and durability. The combustion of traditional diesel engines belongs to the diffusion combustion of spray, and the nature of combustion determines that it will produce a large amount of NOX and PM emissions. The total amount of diesel consumed by diesel engines, the main power of agricultural machinery products, accounts for nearly half of the domestic non-road diesel each year. Energy conservation and emission reduction of agricultural machinery is an important part of the national energy conservation and emission reduction strategy.

[0003] Methanol is a low-carbon / zero-carbon fuel with the advantages of wide sources, low prices, low carbon and environmental protection. Methanol is liquid at room temperature and pressure, easy to store and transport, and highly safe. It is currently one of the most suitable alternative fuels for agricultural machinery. Methanol has a large latent heat of vaporization and contains oxygen in its molecular formula. The addition of methanol can effectively improve the overall formation quality of the fuel-air mixture in the cylinder, reduce the local high-temperature and over-rich areas in the cylinder, and can reduce NOX and PM emissions at the same time. Exhaust gas recirculation (EGR) technology can increase the intake temperature, help shorten the ignition delay period, slow down the initial combustion reaction rate, inhibit the rough operation of diesel engines, and increase the proportion of methanol replacing diesel.

[0004] In order to combine the excellent performance of methanol fuel, exhaust gas recirculation (EGR) technology and diesel engines, in the prior art, patent CN111206999A discloses an electronically controlled diesel-methanol dual-fuel engine control system and method based on EGR technology, which uses high-temperature exhaust gas to accelerate methanol vaporization, improve the quality of methanol mixed gas, control the temperature and pressure increase rate in the cylinder, suppress NOx emissions and knocking, and finally achieve clean and efficient combustion of the dual-fuel engine. However, the content disclosed in this patent is mainly based on the control system. For the control method, this patent does not consider the performance of the diesel-methanol dual-fuel engine from a comprehensive perspective. How to further improve the comprehensive performance of the diesel-methanol dual-fuel engine from the perspective of the control method, so as to meet the power and economy of the diesel-methanol dual-fuel engine, reduce the NOX and PM emissions of the engine, and take into account the safety of the engine, has become one of the topics worthy of in-depth study at present. Summary of the invention

[0005] In view of the problems pointed out in the background technology, the purpose of the present invention is to provide a low-carbon clean alternative fuel non-road engine fuel injection control method, which aims to increase the injection amount of low-carbon fuel methanol while reducing the injection amount of diesel, increase the proportion of methanol replacing diesel, reduce the engine's NOX and PM emissions, reduce the cost of fuel use, and improve the overall performance of the engine.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A low-carbon clean alternative fuel non-road engine fuel injection control method comprises the following steps:

[0008] Step S1, determining the current engine speed V and the current engine output torque M according to the accelerator pedal position and the crankshaft speed;

[0009] Step S2, judging whether the engine is in an idle state according to the coolant temperature T of the engine cooling system and the current engine speed V obtained in step S1; if the engine is in an idle state, executing step S8; otherwise, executing the next step;

[0010] Step S3, determine whether the current output torque M of the engine is zero, if M=0, execute step S8; otherwise, execute the next step;

[0011] Step S4, determining the maximum output torque Mmax of the engine at the current speed V, and judging the engine load state according to the relationship between the current output torque M of the engine and the maximum output torque Mmax at the current speed V; the current load state of the engine includes a low load operation state, a medium load operation state, and a high load operation state;

[0012] Step S5, determining engine operating parameters according to the engine load state obtained in step S4, in combination with the methanol-to-diesel ratio S, the EGR rate F of the engine exhaust gas recirculation system, the cycle variation rate limit α, and the engine knock limit β; the engine operating parameters include: the methanol-to-diesel fuel ratio S, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel;

[0013] Step S6, according to the operating parameters determined in step S5, controlling the methanol fuel injector and the diesel fuel injector to work simultaneously, and controlling the exhaust gas recirculation system to operate; wherein, during the operation of the methanol fuel injector and the diesel fuel injector, the fuel injection advance angle and the injection pulse width are adjusted in real time according to the current fuel injection amount and the current intake state of the engine;

[0014] Step S7: the accelerator pedal position changes, and the process returns to step S1;

[0015] Step S8, only control the diesel fuel injector to work, and the exhaust gas recirculation system to not work; until the accelerator pedal position changes, return to step S1.

[0016] In step S1, the current torque M of the engine is obtained by the following method: presetting the correspondence between the accelerator pedal position and the accelerator opening and the correspondence between the accelerator opening and the output torque; when the accelerator pedal position changes, calling the correspondence between the accelerator pedal position and the accelerator opening; determining the output torque corresponding to the accelerator pedal position through the correspondence between the accelerator opening and the output torque; the output torque is the current torque M of the engine.

[0017] In step S2, the method for determining whether the engine is in an idling state is as follows:

[0018] If the current engine speed V is less than 900 rpm / min or the coolant temperature T of the cooling system is less than or equal to 65° C., the engine is determined to be in an idling state.

[0019] In step S4, the current load state of the engine is determined by the following method:

[0020] When the current engine speed V>900rmp / min and the coolant temperature T of the cooling system>65℃, the maximum torque Mmax of the engine at the current engine speed V is determined;

[0021] If the current engine torque is 0<M≤20%Mmax, the engine is in low-load operation state;

[0022] If the current engine torque is 20%Mmax<M≤60%Mmax, the engine is in medium load operation;

[0023] If the current engine torque is 60%Mmax<M≤Mmax, the engine is in a high-load operating state.

[0024] In step S5, the knock limit value β is obtained by presetting the corresponding relationship between the cylinder vibration value and the cylinder pressure increase rate, and the corresponding relationship between the cylinder vibration value and the maximum explosion pressure in the cylinder, and determining the knock limit value β according to the maximum pressure increase rate and the maximum explosion pressure.

[0025] In step S5, the engine operating parameters are determined by the following method:

[0026] If the engine is in a low-load state, first determine the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel according to the methanol-to-diesel ratio S and the emission limit; then adjust the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel according to the cycle variation rate limit α and the knock limit β;

[0027] If the engine is in a medium load state, first determine the valve opening of the exhaust gas recirculation system according to the cycle variation rate limit α and the emission limit, and determine the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel; then, adjust the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel according to the methanol-to-diesel ratio S and the knock limit β;

[0028] If the engine is in a high-load state, the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of methanol fuel, and the injection advance angle and injection duration of diesel fuel are first determined according to the knock limit β and the emission limit; thereafter, the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of methanol fuel, and the injection advance angle and injection duration of diesel fuel are adjusted according to the methanol-to-diesel ratio S and the cycle variation rate limit α.

[0029] In step S5, when the engine is in a low load state, the methanol-to-diesel ratio S is set to S≤30%, the valve opening of the exhaust gas recirculation system maintains the EGR rate F≤10%, and the cycle variation rate limit α≤5%;

[0030] When the engine is in a medium load state, the cycle change rate limit α is α≤5%, the methanol replacement diesel fuel ratio S is 20%≤S≤60%, and the valve opening of the exhaust gas recirculation system maintains the EGR rate F at 10%<F≤20%;

[0031] When the engine is in a high load state, the proportion of methanol replacing diesel fuel S is 40%≤S≤80%, the valve opening of the exhaust gas recirculation system maintains the EGR rate F at 10%<F≤20%, and the cycle variation rate limit α≤5%.

[0032] In step S6, the injection advance angles of the methanol fuel injector and the diesel fuel injector are adjusted by the following method:

[0033] Acquire current phase information of the engine, and adjust the fuel injection advance angle of the methanol fuel injector and the diesel fuel injector according to the current engine speed V and the current phase information;

[0034] The injection pulse width of the methanol fuel injector and the diesel fuel injector is adjusted by the following method: obtaining the current intake state of the engine, i.e., the intake temperature and the intake pressure, and adjusting the injection pulse width of the methanol fuel injector and the diesel fuel injector according to the current intake state and the current actual fuel injection pressure of the engine to ensure the required fuel injection amount during the current operation.

[0035] Beneficial effects of the present invention: The present invention judges the operating state of the engine and uses different parameter strategies to adjust the fuel injection amount according to different states, thereby meeting the power and economy of low-carbon clean alternative fuel non-road engines, reducing the engine's NOX and PM emissions, and taking into account the engine's safety, thereby effectively improving the engine's comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the present invention.

[0037] Figure 2 It is a schematic diagram of the structure of the low-carbon clean alternative fuel non-road engine of the present invention.

[0038] Figure 3 It is a schematic diagram of the structure of the fuel injection system;

[0039] Figure 4 Schematic diagram of the fuel injection system installation.

[0040] In the figure: 1. engine body, 2. fuel injection system, 3. fuel injection system controller, 4. manifold intake pipe, 5. intake manifold, 6. intake pipe main pipe, 7. cylinder head, 8. cylinder head intake duct, 9. intake connecting pipe, 10. exhaust gas recirculation system, 11. EGR valve, 12. methanol fuel injector, 13. methanol fuel pressure sensor, 14. diesel fuel injector, 15. diesel fuel pressure sensor, 16. accelerator pedal position sensor, 17. crankshaft speed sensor; 18. camshaft phase sensor, 19. intake air temperature pressure sensor, 20. water temperature sensor, 21. intake system, 22. knock sensor. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] like Figure 2-4 As shown, the low-carbon clean alternative fuel non-road engine described in the present invention includes an engine body 1, a fuel injection system 2 and a fuel injection system controller 3.

[0043] The low-carbon clean alternative fuel non-road engine body 1 is provided with a manifold-type intake pipe 4 and a cylinder head 7. The manifold-type intake pipe 4 is provided with an intake pipe manifold 5 and an intake pipe main pipe 6. The end of the intake pipe manifold 5 is installed on the side of the cylinder head 7, and the intake pipe manifold 5 is connected to the cylinder head intake passage 8 in a one-to-one correspondence. The intake pipe manifold 5 is provided with a mounting hole for installing a methanol fuel injector 12; the intake pipe main pipe 6 is provided with a mounting hole for installing an intake air temperature and pressure sensor 19. The intake pipe main pipe 6 is connected to the intake connecting pipe 9, and the intake connecting pipe 9 is connected to the exhaust gas recirculation system 10 and the intake system 21. Air enters through the intake system 21, mixes with the exhaust gas after combustion in the intake connecting pipe 9, and enters the manifold-type intake pipe 4. The exhaust gas recirculation system 10 is provided with an EGR valve 11, and the valve plate opening of the EGR valve 11 is controlled by the fuel injection system controller 3 to control the amount of combustion exhaust gas entering the intake connecting pipe 9.

[0044] The fuel injection system 2 includes a methanol fuel injector 12, a methanol fuel pressure sensor 13, a diesel fuel injector 14 and a diesel fuel pressure sensor 15. The methanol fuel injector 12 is installed on the intake manifold 5, and one methanol fuel injector 12 is installed on one intake manifold 5. The methanol fuel injector 12 is installed obliquely on the intake manifold 5, and the installation angle is 8° with the horizontal direction to ensure that the methanol fuel injection direction is along the intake air flow direction, and the methanol fuel cannot hit the inner wall surface of the intake manifold 5 within the penetration distance to prevent wet wall. The injection pressure of the methanol fuel injector 12 is 7 bar. The methanol fuel is mixed with the air in the manifold intake pipe 4 and enters the cylinder head intake duct 8, and then enters the engine cylinder. The diesel fuel injector 14 is installed obliquely in the cylinder head 7, and one diesel fuel injector 14 is installed in one cylinder. The injection pressure of the diesel fuel injector 14 is 1600 bar, and the diesel fuel is directly sprayed into the engine cylinder. Before and after the engine reaches top compression dead center, the diesel is compressed and ignites, igniting the methanol and air mixture.

[0045] The fuel injection system controller 3 controls the methanol fuel injector 12 and the diesel fuel injector 14, and determines the engine operation state by monitoring the accelerator pedal position sensor 16, the crankshaft speed sensor 17, the camshaft phase sensor 18, the intake air temperature and pressure sensor 19, the water temperature sensor 20, and the knock sensor 22. The fuel injection pressure is determined by the methanol fuel pressure sensor 13 and the diesel fuel pressure sensor 15.

[0046] As attached Figure 1 As shown, a low-carbon clean alternative fuel non-road engine fuel injection control method proposed by the present invention comprises the following steps:

[0047] Step S1, determining the current engine speed V and the current engine output torque M according to the accelerator pedal position and the crankshaft speed; specifically, the fuel injection system controller 3 reads the position signal of the accelerator pedal position sensor 16 and the speed signal of the crankshaft speed sensor 17 respectively, and determines the current engine speed and the current engine output torque according to the read signals;

[0048] Step S2, judging whether the engine is in an idling state according to the coolant temperature T of the engine cooling system and the current engine speed V obtained in step S1; if the engine is in an idling state, executing step S8; otherwise executing the next step; specifically, the fuel injection system controller 3 reads the temperature signal of the water temperature sensor 20, and judges when the coolant temperature T of the engine cooling system is in an idling state according to the read signal;

[0049] Step S3, determine whether the current output torque M of the engine is zero, if M=0, execute step S8; otherwise, execute the next step;

[0050] Step S4, determining the maximum output torque Mmax of the engine at the current speed V, and judging the engine load state according to the relationship between the current output torque M of the engine and the maximum output torque Mmax at the current speed V; the current load state of the engine includes a low load operation state, a medium load operation state, and a high load operation state;

[0051] Step S5, determining engine operating parameters according to the engine load state obtained in step S4, in combination with the methanol-to-diesel ratio S, the EGR rate F of the engine exhaust gas recirculation system 10, the cycle variation rate limit α, and the engine knock limit β; the engine operating parameters include: the methanol-to-diesel fuel ratio S, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel;

[0052] Step S6, according to the operating parameters determined in step S5, controlling the methanol fuel injector 12 and the diesel fuel injector 14 to work simultaneously, and controlling the exhaust gas recirculation system 10 to operate; wherein, during the operation of the methanol fuel injector 12 and the diesel fuel injector 14, the fuel injection advance angle and the injection pulse width are adjusted in real time according to the current fuel injection amount and the current intake state of the engine;

[0053] Step S7: the accelerator pedal position changes, and the process returns to step S1;

[0054] Step S8, only the diesel fuel injector 14 is controlled to work, and the exhaust gas recirculation system 10 is not controlled to work; until the accelerator pedal position changes, return to step S1.

[0055] In step S1, the current torque M of the engine is obtained by the following method: presetting the correspondence between the accelerator pedal position and the accelerator opening and the correspondence between the accelerator opening and the output torque; when the accelerator pedal position changes, calling the correspondence between the accelerator pedal position and the accelerator opening; determining the output torque corresponding to the accelerator pedal position through the correspondence between the accelerator opening and the output torque; the output torque is the current torque M of the engine.

[0056] In step S2, the method for determining whether the engine is in an idling state is as follows:

[0057] If the current engine speed V is less than 900 rpm / min or the coolant temperature T of the cooling system is less than or equal to 65° C., the engine is determined to be in an idling state.

[0058] In step S4, the current load state of the engine is determined by the following method:

[0059] When the current engine speed V>900rmp / min and the coolant temperature T of the cooling system>65℃, the maximum torque Mmax of the engine at the current engine speed V is determined;

[0060] If the current engine torque is 0<M≤20%Mmax, the engine is in low-load operation state;

[0061] If the current engine torque is 20%Mmax<M≤60%Mmax, the engine is in medium load operation;

[0062] If the current engine torque is 60%Mmax<M≤Mmax, the engine is in a high-load operating state.

[0063] In step S5, the knock limit value β is obtained by presetting the corresponding relationship between the cylinder vibration value and the cylinder pressure increase rate, and the corresponding relationship between the cylinder vibration value and the maximum explosion pressure in the cylinder, and determining the knock limit value β according to the maximum pressure increase rate and the maximum explosion pressure.

[0064] In step S5, the engine operating parameters are determined by the following method:

[0065] If the engine is in a low-load state, firstly, the EGR valve plate opening of the exhaust gas recirculation system 10, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel are determined according to the methanol-to-diesel ratio S and the emission limit, so that the engine operates within the range specified by the emission limit according to the methanol-to-diesel ratio S; then, the EGR valve plate opening of the exhaust gas recirculation system 10, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel are adjusted according to the cycle variation rate limit α and the knock limit β, so that the engine is within the range specified by the cycle variation rate limit α and the knock limit β;

[0066] If the engine is in a medium load state, firstly, the EGR valve plate opening of the exhaust gas recirculation system is determined according to the cycle variation rate limit α and the emission limit, and the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel are determined, so that the engine operates within the range limited by the cycle variation rate limit α and the emission limit; then, the valve plate opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel are adjusted according to the methanol-to-diesel ratio S and the knock limit β, so that the engine operates within the range limited by the methanol-to-diesel ratio S and the knock limit β;

[0067] If the engine is in a high-load state, first determine the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of methanol fuel, and the injection advance angle and injection duration of diesel fuel according to the knock limit β and the emission limit, so that the engine operates within the range specified by the knock limit β and the emission limit; then, adjust the EGR valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of methanol fuel, and the injection advance angle and injection duration of diesel fuel according to the methanol-to-diesel ratio S and the cycle variation rate limit α, so that the engine operates within the range specified by the methanol-to-diesel ratio S and the cycle variation rate limit α.

[0068] In step S5, when the engine is in a low load state, the methanol-to-diesel ratio S is set to S≤30%, the EGR valve opening of the exhaust gas recirculation system 10 maintains the EGR rate F≤10%, and the cycle variation rate limit α≤5%;

[0069] When the engine is in a medium load state, the cycle change rate limit α is α≤5%, the methanol replacement diesel fuel ratio S is 20%≤S≤60%, and the EGR valve plate opening of the exhaust gas recirculation system 10 maintains the EGR rate F at 10%<F≤20%;

[0070] When the engine is in a high load state, the methanol replacement diesel fuel ratio S is 40%≤S≤80%, the valve opening of the EGR valve 11 of the exhaust gas recirculation system 10 maintains the EGR rate F at 10%<F≤20%, and the cycle variation rate limit α≤5%.

[0071] In step S6, the injection advance angles of the methanol fuel injector 12 and the diesel fuel injector 14 are adjusted by the following method:

[0072] Acquire the current phase information of the engine, and adjust the fuel injection advance angle of the methanol fuel injector 12 and the diesel fuel injector 14 according to the current engine speed V and the current phase information; specifically, the fuel injection system controller 3 reads the signals of the crankshaft speed sensor 17 and the camshaft phase sensor 18, and determines the current phase information of the engine according to the read signals;

[0073] The injection pulse width of the methanol fuel injector 12 and the diesel fuel injector 14 is adjusted by the following method: the current intake state of the engine, i.e., the intake temperature and intake pressure, is obtained, and the injection pulse width of the methanol fuel injector 12 and the diesel fuel injector 14 is adjusted according to the current intake state and the current actual fuel injection pressure of the engine to ensure the fuel injection amount required during the current operation. Specifically, the fuel injection system controller 3 reads the temperature signal and pressure signal of the intake temperature and pressure sensor 19, and judges the current intake state of the engine, i.e., the intake temperature and intake pressure, according to the read signals; the fuel injection system controller 3 reads the signal of the methanol fuel pressure sensor 13 and the signal of the diesel fuel pressure sensor 15, and judges the current actual fuel injection pressure of the engine according to the read signals.

[0074] In step S5, the valve opening of the EGR valve 11 of the exhaust gas recirculation system 10 is set by the fuel injection system controller 3; the fuel injection system controller 3 controls the fuel injection system 2 to input different fuel injection parameters to the engine under different operating conditions to meet the engine's power and emissions.

[0075] In the control method of the present invention, when the low-carbon clean alternative fuel non-road engine is running in an idle state, the fuel injection system 2 controls only the diesel fuel injector 14 to work, and at this time, the diesel injection amount is determined according to the target torque requirement. And the valve plate of the EGR valve 11 in the exhaust gas recirculation system 10 is closed, and the exhaust gas recirculation system 10 does not work.

[0076] Specifically, when the low-carbon clean alternative fuel non-road engine is running at a low load, the fuel injection system controller 3 controls the methanol fuel injector 12 and the diesel fuel injector 14 to work together. The phase information under the current operating state is determined by the crankshaft speed sensor 17 and the camshaft phase sensor 18, and the valve opening in the exhaust gas recirculation system 10 is controlled; the diesel injector 14 is controlled to inject diesel fuel, and the diesel fuel injection amount is large. The diesel injector 14 injects twice, first injects a small amount within 10°-20° before the top dead center, and then injects diesel fuel within 5°-15° before the top dead center; the methanol fuel injector 12 is controlled to inject methanol fuel, and the duration of methanol fuel injection is short, and the proportion of methanol replacing diesel fuel S≤30%.

[0077] Among them, under low load conditions, the valve opening of the EGR valve 11 in the exhaust gas recirculation system 10, the injection advance angle and injection duration of the methanol fuel and diesel fuel in the fuel injection amount are determined by the methanol replacing diesel fuel ratio S and the emission limit, and the cycle variation rate limit α and the knock limit β are secondarily determined.

[0078] When the low-carbon clean alternative fuel non-road engine is running at a medium load state, the fuel injection system controller 3 controls the methanol fuel injector 12 and the diesel fuel injector 14 to work together. The phase information under the current operating state is determined by the crankshaft speed sensor 17 and the camshaft phase sensor 18, and the valve plate opening of the EGR valve 11 in the exhaust gas recirculation system 10 is controlled; the diesel injector 14 is controlled to inject diesel fuel, and the diesel injector 14 injects twice, first injecting a small amount within 0°-15° before the top dead center, and injecting diesel fuel again near the top dead center; the methanol fuel injector 12 is controlled to inject methanol fuel, and the methanol-to-diesel fuel ratio S is 20%≤S≤60%.

[0079] Among them, under medium load conditions, the valve opening of the EGR valve 11 in the exhaust gas recirculation system 10, the injection advance angle and injection duration of the methanol fuel and diesel fuel in the fuel injection amount are determined by the cycle variation rate limit α and the emission limit, and the methanol replacement diesel fuel ratio S and the knock limit β are determined by priority.

[0080] When the low-carbon clean alternative fuel non-road engine is running at a high load, the fuel injection system controller 3 controls the methanol fuel injector 12 and the diesel fuel injector 14 to work together. The phase information under the current operating state is determined by the crankshaft speed sensor 17 and the camshaft phase sensor 18, and the valve plate opening of the EGR valve 11 in the exhaust gas recirculation system 10 is controlled; the diesel injector 14 is controlled to inject diesel fuel, and the diesel injector 14 injects twice, first injecting a small amount within 0°-15° before the top dead center, and then injecting diesel fuel again within 0°-15° after the top dead center; the methanol fuel injector 12 is controlled to inject methanol fuel, and the methanol fuel injection amount is large. The methanol fuel injector 12 is controlled to inject methanol fuel before the intake valve is opened, and the methanol replacement diesel fuel ratio S is 40%≤S≤80%.

[0081] Among them, under high load conditions, the valve opening of the EGR valve 11 in the exhaust gas recirculation system 10, the injection advance angle and injection duration of methanol fuel and diesel fuel in the fuel injection amount are determined by the knock limit β and the emission limit, and the methanol replacement diesel fuel ratio S and the cycle variation rate limit α are determined by priority.

[0082] The fuel injection system controller 3 reads the vibration signal of the knock sensor 22, and determines the current engine cylinder vibration condition based on the read signal, determines the combustion condition in the engine cylinder, and whether there is a knock condition. The present invention pre-sets the corresponding relationship between the knock sensor 22 and the cylinder pressure increase rate, and the corresponding relationship between the knock sensor 22 and the maximum explosion pressure in the cylinder, and determines the knock limit value based on the maximum pressure increase rate and the maximum explosion pressure. When the current cylinder vibration signal is obtained, the above-mentioned corresponding relationship can be directly called, and the current cylinder pressure increase rate and the maximum explosion pressure in the cylinder can be determined through the above-mentioned corresponding relationship, and then it is determined whether it exceeds the set knock limit value β based on the vibration signal data. When the read knock signal data exceeds the knock limit value β, the fuel injection system controller 3 increases the valve plate opening of the EGR valve 11 in the exhaust gas recirculation system, increases the EGR rate F, and controls the diesel secondary injection timing to move back.

[0083] The parts not described in detail in this invention are prior art.

Claims

1. A low-carbon clean alternative fuel non-road engine fuel injection control method, characterized by: The following steps are involved: Step S1, determining the current engine speed V and the current engine output torque M according to the accelerator pedal position and the crankshaft speed; Step S2, judging whether the engine is in an idle state according to the coolant temperature T of the engine cooling system and the current engine speed V obtained in step S1; if the engine is in an idle state, executing step S8; otherwise, executing the next step; Step S3, determine whether the current output torque M of the engine is zero, if M=0, execute step S8; Otherwise, proceed to the next step; Step S4, determining the maximum output torque Mmax of the engine at the current speed V, and judging the engine load state according to the relationship between the current output torque M of the engine and the maximum output torque Mmax at the current speed V; the current load state of the engine includes a low load operation state, a medium load operation state, and a high load operation state; Step S5, determining engine operating parameters according to the engine load state obtained in step S4, in combination with the methanol-to-diesel ratio S, the EGR rate F of the engine exhaust gas recirculation system, the cycle variation rate limit α, and the engine knock limit β; the engine operating parameters include: the methanol-to-diesel fuel ratio S, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel; In step S5, the engine operating parameters are determined by the following method: If the engine is in a low-load state, first determine the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel according to the methanol-to-diesel ratio S and the emission limit; then adjust the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel according to the cycle variation rate limit α and the knock limit β; If the engine is in a medium load state, first determine the valve opening of the exhaust gas recirculation system according to the cycle variation rate limit α and the emission limit, and determine the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel; then, adjust the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel according to the methanol-to-diesel ratio S and the knock limit β; If the engine is in a high-load state, the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel are first determined according to the knock limit β and the emission limit; then, the valve opening of the exhaust gas recirculation system, the injection advance angle and injection duration of the methanol fuel, and the injection advance angle and injection duration of the diesel fuel are adjusted according to the methanol-to-diesel ratio S and the cycle variation rate limit α; Step S6, according to the operating parameters determined in step S5, controlling the methanol fuel injector and the diesel fuel injector to work simultaneously, and controlling the exhaust gas recirculation system to operate; wherein, during the operation of the methanol fuel injector and the diesel fuel injector, the fuel injection advance angle and the injection pulse width are adjusted in real time according to the current fuel injection amount and the current intake state of the engine; Step S7: the accelerator pedal position changes, and the process returns to step S1; Step S8, only control the diesel fuel injector to work, and the exhaust gas recirculation system to not work; until the accelerator pedal position changes, return to step S1.

2. A low-carbon clean alternative fuel non-road engine fuel injection control method according to claim 1, characterized in that: In step S1, the current torque M of the engine is obtained by the following method: presetting the correspondence between the accelerator pedal position and the accelerator opening and the correspondence between the accelerator opening and the output torque; when the accelerator pedal position changes, calling the correspondence between the accelerator pedal position and the accelerator opening; determining the output torque corresponding to the accelerator pedal position through the correspondence between the accelerator opening and the output torque; the output torque is the current torque M of the engine.

3. A low-carbon clean alternative fuel non-road engine fuel injection control method according to claim 1, characterized in that: In step S2, the method for determining whether the engine is in an idling state is as follows: If the current engine speed V is less than 900 rpm / min or the coolant temperature T of the cooling system is less than or equal to 65° C., the engine is determined to be in an idling state.

4. A low-carbon clean alternative fuel non-road engine fuel injection control method according to claim 1, characterized in that: In step S4, the current load state of the engine is determined by the following method: When the current engine speed V>900rmp / min and the coolant temperature T of the cooling system>65℃, the maximum torque Mmax of the engine at the current engine speed V is determined; If the current engine torque is 0<M≤20%Mmax, the engine is in low-load operation state; If the current engine torque is 20%Mmax<M≤60%Mmax, the engine is in medium load operation; If the current engine torque is 60%Mmax<M≤Mmax, the engine is in a high-load operating state.

5. A low-carbon clean alternative fuel non-road engine fuel injection control method according to claim 1, characterized in that: In step S5, the knock limit value β is obtained by presetting the corresponding relationship between the cylinder vibration value and the cylinder pressure increase rate, and the corresponding relationship between the cylinder vibration value and the maximum explosion pressure in the cylinder, and determining the knock limit value β according to the maximum pressure increase rate and the maximum explosion pressure.

6. A low-carbon clean alternative fuel non-road engine fuel injection control method according to claim 5, characterized in that: In step S5, when the engine is in a low load state, the methanol-to-diesel ratio S is set to S≤30%, the valve opening of the exhaust gas recirculation system maintains the EGR rate F≤10%, and the cycle variation rate limit α≤5%; When the engine is in a medium load state, the cycle change rate limit α is α≤5%, the methanol replacement diesel fuel ratio S is 20%≤S≤60%, and the valve opening of the exhaust gas recirculation system maintains the EGR rate F at 10%<F≤20%; When the engine is in a high load state, the proportion of methanol replacing diesel fuel S is 40%≤S≤80%, the valve opening of the exhaust gas recirculation system maintains the EGR rate F at 10%<F≤20%, and the cycle variation rate limit α≤5%.

7. A low-carbon clean alternative fuel non-road engine fuel injection control method according to claim 1, characterized in that: In step S6, the injection advance angles of the methanol fuel injector and the diesel fuel injector are adjusted by the following method: Acquire current phase information of the engine, and adjust the fuel injection advance angle of the methanol fuel injector and the diesel fuel injector according to the current engine speed V and the current phase information; The injection pulse width of the methanol fuel injector and the diesel fuel injector is adjusted by the following method: obtaining the current intake state of the engine, i.e., the intake temperature and the intake pressure, and adjusting the injection pulse width of the methanol fuel injector and the diesel fuel injector according to the current intake state and the current actual fuel injection pressure of the engine to ensure the required fuel injection amount during the current operation.

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