Methanol-diesel oil dual-fuel engine mixed injection system and cooperative control method thereof

Abstract

The invention discloses a methanol-diesel oil dual-fuel engine mixed injection system and a cooperative control method thereof, and belongs to the technical field of diesel oil engines. The mixed injection system comprises a low-pressure methanol injection system, a high-pressure methanol injection system, a high-pressure diesel injection system, an integrated controller and a direct-current power source. The low-pressure methanol injection system injects methanol into an intake manifold in the intake stroke of an engine to form premixed methanol mixed gas with air. The high-pressure methanol injection system directly injects high-pressure methanol into the air cylinder in the power stroke of the engine; the high-pressure diesel injection system directly injects high-pressure diesel into a cylinder for igniting methanol or directly works in a pure diesel mode; the mixed injection system is combined with the cooperative control method, cooperative operation of the mixed injection system in multiple working modes self-adaptive to engine working conditions and environment conditions can be achieved, the advantages of the different working modes are comprehensively utilized, and efficient and clean combustion of the engine under the high methanol substitution rate is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel engines, and in particular to a methanol-diesel dual-fuel engine mixed injection system and a coordinated control method thereof. Background Art

[0002] Faced with the opportunities and challenges brought by the dual carbon goals, traditional internal combustion engines are moving towards fuel diversification. Replacing traditional fossil fuels with e-fuels such as green hydrogen, green ammonia and green alcohol obtained from renewable energy is an important path to achieve carbon neutrality in internal combustion engines, but there are still many technical bottlenecks that need to be broken through for different fuels. Compared with other fuels, methanol is a low-carbon alternative fuel for diesel engines with good application prospects. Methanol has the advantages of low cost, convenient transportation and wide sources. Methanol can be produced from coal, natural gas, biomass, wood, agricultural products and urban waste, and can also be synthesized from green hydrogen and CO2 from direct air carbon capture to become a carbon-neutral fuel.

[0003] At present, methanol-diesel dual-fuel control technology is one of the effective technical measures to achieve methanol substitution for diesel, mainly including two technical solutions: methanol intake port injection and methanol direct injection. Methanol intake port injection is an earlier way to achieve diesel-methanol dual-fuel control technology. By forming a premixed air-methanol mixture in the intake port and then igniting it with diesel directly injected into the cylinder, it can achieve a reactive control compression working mode that simultaneously improves engine thermal efficiency and reduces NOx and PM emissions. However, the methanol substitution rate of methanol intake port injection is not high, and can only reach a methanol substitution rate of about 60% under some engine conditions. Methanol direct injection technology injects methanol into the cylinder during the combustion process to achieve methanol diffusion combustion, which can expand the diesel-methanol dual-fuel mode to a large load area and achieve a high methanol substitution rate. The highest substitution rate can reach more than 90%, but the pollutant emissions of the methanol direct injection solution are higher than those of the methanol intake port injection solution.

[0004] Therefore, the current methanol-diesel dual-fuel control technology cannot achieve efficient and clean combustion of the methanol-diesel dual-fuel mode in the entire diesel engine operating range through a single control method. It is necessary to provide a methanol-diesel dual-fuel engine mixed injection system and a coordinated control method, which comprehensively utilizes the advantages of the two technical solutions of methanol intake port injection and methanol direct injection, and solves the problem of optimized operation of the methanol-diesel dual-fuel engine under a high methanol substitution rate. Summary of the invention

[0005] The purpose of the present invention is to provide a methanol-diesel dual-fuel engine mixed injection system and a coordinated control method thereof, which can couple and control the subsystems of the mixed injection system according to the engine operating conditions and environmental conditions, realize multiple working modes, comprehensively utilize the advantages of different working modes, realize multi-mode coordinated operation of the methanol-diesel dual-fuel engine within the full operating range, and optimize the engine's operating performance.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0007] A methanol-diesel dual-fuel engine mixed injection system, the system comprising: a low-pressure methanol injection system, a high-pressure methanol injection system, a high-pressure diesel injection system, an integrated controller 19 and a DC power supply 20;

[0008] The low-pressure methanol injection system comprises: a low-pressure methanol nozzle 2, a low-pressure methanol common rail 3, a constant pressure valve 4, a low-pressure methanol pump 5, and a methanol fuel tank 6;

[0009] Specifically, the low-pressure methanol nozzle 2 is installed on the engine intake manifold and connected to the low-pressure methanol common rail 3, the low-pressure methanol common rail 3 is connected to the constant pressure valve 4, the constant pressure valve 4 is connected to the low-pressure methanol pump 5, the low-pressure methanol pump 5 is connected to the methanol fuel tank 6, and the fuel return end of the constant pressure valve 4 is connected to the methanol fuel tank 6;

[0010] The injection pressure of the low-pressure methanol injection system is controlled by a constant pressure valve 4. When the pressure in the low-pressure methanol common rail exceeds the constant pressure valve threshold of 0.45 MPa, the low-pressure methanol will flow back to the methanol tank through the fuel return end of the constant pressure valve, thereby maintaining the methanol injection pressure in the low-pressure methanol common rail.

[0011] The high-pressure methanol injection system comprises: a methanol fuel tank 6, a high-pressure methanol pump 10, a high-pressure methanol common rail 8, a high-pressure methanol nozzle 7, a high-pressure methanol common rail pressure sensor 9, a high-pressure methanol pump 10, a methanol metering device 11 and a methanol cooling device 12;

[0012] Specifically, the high-pressure methanol nozzle 7 is installed on the high-pressure methanol nozzle mounting hole of the engine 1, the mounting hole is communicated with the combustion chamber of the engine 1, the input end of the high-pressure methanol nozzle 7 is connected to the output end of the high-pressure methanol common rail 8, the fuel return end of the high-pressure methanol nozzle 7 is connected to the methanol cooling device 12, and the high-pressure methanol common rail 8 is equipped with a high-pressure methanol common rail pressure sensor 9 for collecting the high-pressure methanol injection pressure in the high-pressure methanol common rail 8; the input end of the high-pressure methanol common rail 8 is connected to the output end of the high-pressure methanol pump 10, and the high-pressure methanol pump 10 is equipped with a methanol metering device 11, and the amount of methanol entering the methanol common rail can be adjusted by controlling the methanol metering device 11, thereby realizing accurate control of the high-pressure methanol injection pressure; the input end of the high-pressure methanol pump 10 is connected to the methanol fuel tank 6, and the fuel return end of the high-pressure methanol pump is connected to the methanol cooling device 12;

[0013] The injection pressure of the high-pressure methanol injection system is closed-loop controlled by the integrated controller 19; the control method of the high-pressure methanol injection pressure is stored and run in the integrated controller 19, and the control method of the high-pressure methanol injection pressure includes: high-pressure methanol injection pressure target value calculation and high-pressure methanol injection pressure controller; wherein, the high-pressure methanol injection pressure target value calculation contains a high-pressure methanol injection pressure MAP, the input is the engine speed and the accelerator pedal opening, the output is the high-pressure methanol target injection pressure, and the appropriate target injection pressure can be determined according to the engine operating conditions; the MAP is a way to store and calculate parameters in the controller, and the MAP is a data table in the controller, and its axis points and parameter values ​​can be preset in the MAP. When the controller is running, the corresponding parameter values ​​can be quickly determined according to the input value of the MAP; the high-pressure methanol injection pressure controller adopts a PID controller, which can close-loop adjust the PWM parameters of the high-pressure methanol injection pressure, and the PWM parameters include: duty cycle and frequency;

[0014] The high-pressure diesel injection system includes: an injector 13, a high-pressure diesel common rail 14, a high-pressure diesel common rail 15, a high-pressure diesel pump 16, a diesel metering device 17, and a diesel tank 18;

[0015] Specifically, the high-pressure diesel injector 13 is installed in the diesel injector mounting hole at the center position of the cylinder head of the engine 1, and the mounting hole is connected to the combustion chamber of the engine 1. The input end of the high-pressure diesel injector 13 is connected to the output end of the high-pressure diesel common rail 14. A high-pressure diesel common rail pressure sensor 15 is installed on the high-pressure common rail 14 to collect the high-pressure diesel injection pressure in the high-pressure diesel common rail 15; the input end of the high-pressure common rail 14 is connected to the output end of the high-pressure diesel pump 16, and a diesel metering device 17 is installed on the high-pressure diesel pump 16. By controlling the diesel metering device 17, the amount of diesel entering the high-pressure diesel common rail can be adjusted, thereby realizing precise control of the high-pressure diesel injection pressure; the input end and the return oil end of the high-pressure diesel pump 16 are both connected to the diesel tank 18.

[0016] The injection pressure of the high-pressure diesel injection system is closed-loop controlled by the integrated controller 19; the control method of the high-pressure diesel injection pressure is stored and runs in the integrated controller 19, and the control method of the high-pressure diesel injection pressure includes: high-pressure diesel injection pressure target value calculation and high-pressure diesel injection pressure controller; the high-pressure diesel injection pressure target value calculation contains a high-pressure diesel injection pressure MAP, the input is the engine speed and the accelerator pedal opening, the output is the high-pressure diesel target injection pressure, and the appropriate high-pressure diesel target injection pressure is determined according to the engine working condition; the high-pressure diesel injection pressure controller adopts a PID controller, which can close-loop adjust the high-pressure diesel injection pressure PWM parameters;

[0017] The integrated controller 19 is electrically connected to the high-pressure methanol common rail pressure sensor 9, the high-pressure methanol metering device 11, the high-pressure diesel common rail pressure sensor 15, the high-pressure diesel metering device 17, the low-pressure methanol nozzle 2, the high-pressure methanol nozzle 7, the high-pressure diesel injector 13, the DC power supply 20 and other engine sensors respectively; the integrated controller 19 is responsible for controlling the fuel injection pressure and fuel injection process of each subsystem of the mixed injection system (low-pressure methanol injection system, high-pressure methanol injection system, high-pressure diesel injection system);

[0018] Specifically, the integrated controller 19 includes: a sensor signal conditioning module 201, a low-pressure methanol injection drive module 202, a high-pressure methanol injection drive module 203, a high-pressure diesel injection drive module 204, a microprocessor 205 and a power supply module 206;

[0019] The sensors in the sensor signal conditioning module 201 include but are not limited to a crankshaft position sensor, a camshaft position sensor, an intake air temperature sensor, a coolant temperature sensor, an atmospheric pressure sensor, a high-pressure methanol pressure sensor, a high-pressure diesel pressure sensor, an oil pressure sensor, and an oil temperature sensor; the sensor signal conditioning module 201 conditions the signals of each sensor and transmits the signals to the microprocessor 205 for real-time monitoring and control of the engine;

[0020] Furthermore, the integrated controller 19 accurately identifies the engine phase through the engine crankshaft position sensor and the camshaft position sensor, and provides a unified injection start point reference for the low-pressure methanol injection system, the high-pressure methanol injection system, and the high-pressure diesel injection system;

[0021] The low-pressure methanol injection drive module 202 controls the low-pressure methanol nozzle to quickly open at the specified low-pressure methanol injection start point according to the injection parameters and accurately controls the opening time of the low-pressure methanol nozzle 2 (low-pressure methanol injection pulse width). The injection pulse width determines the injection amount of low-pressure methanol. The longer the pulse width, the more low-pressure methanol is injected into the intake manifold. The injection parameters include: injection start point and injection pulse width;

[0022] The high-pressure methanol injection drive module 203 controls the methanol injection pressure in the high-pressure methanol common rail 8 according to the high-pressure methanol metering device 11, and controls the high-pressure methanol nozzle 7 to quickly open at the specified high-pressure methanol injection starting point according to the injection parameters and accurately controls the nozzle opening time (high-pressure methanol injection pulse width), thereby accurately controlling the high-pressure methanol injection amount;

[0023] The high-pressure methanol drive module 203 generates a correct PWM drive signal according to the PWM parameters to control the high-pressure methanol metering device 11, thereby adjusting the amount of methanol entering the high-pressure methanol common rail 8 from the high-pressure methanol pump 10 to stabilize the pressure in the high-pressure methanol common rail 8; the target injection pressure of the high-pressure methanol injection system can be pre-set in the high-pressure methanol injection pressure MAP according to the engine operating conditions, ranging from 40 to 160 MPa; in order to prevent methanol from vaporizing during the reflux process, the methanol refluxed from the high-pressure methanol nozzle and the high-pressure methanol pump is cooled by the cooling device 12 and then refluxed to the methanol fuel tank.

[0024] The high-pressure diesel injection drive module 204 controls the injector 13 to open quickly at the specified injection start point according to the injection parameters and accurately controls the opening time of the injector 13 (high-pressure diesel injection pulse width), thereby accurately controlling the high-pressure diesel injection amount;

[0025] The high-pressure diesel drive module 204 generates a correct PWM drive signal according to the PWM parameters to control the high-pressure methanol metering device 17, so that the pressure in the high-pressure diesel common rail 14 is stabilized at the high-pressure diesel target injection pressure; the injection pressure of the high-pressure diesel injection system can be pre-set according to the engine operating conditions, ranging from 40 to 160 MPa.

[0026] The microprocessor 205 stores and runs a working mode calculation, which includes a working mode MAP. The input of the working mode MAP is the engine speed and the throttle opening, and the output value of the MAP is the working mode status word.

[0027] The power supply module 206 is electrically connected to the DC power supply 20 to supply power to all drive modules of the integrated controller 19 and sensors on the engine.

[0028] A coordinated control method for a methanol-diesel dual-fuel engine mixed injection system;

[0029] Furthermore, the collaborative control method controls the injection parameters of each injection system by storing and running the hybrid injection system collaborative control method in the microprocessor 206, and can realize four working modes, and the specific steps are:

[0030] S1: Determine the working mode according to the engine working condition;

[0031] The working mode status word is a binary number, wherein the working mode status word 00 represents a pure diesel working mode, 01 represents a reactive controlled compression combustion working mode of methanol intake port injection + in-cylinder diesel ignition, 10 represents a diffusion combustion working mode of direct in-cylinder diesel injection + high-pressure methanol injection, and 11 represents a mixed combustion working mode of methanol intake port injection + in-cylinder direct in-cylinder diesel ignition + high-pressure methanol injection;

[0032] The working mode MAP can be used to pre-set the appropriate working mode during the engine operation according to the engine working conditions; it should be noted that in the starting condition, the 00 pure diesel working mode is used by default to ensure the smooth start of the engine;

[0033] S2, calculating injection parameters according to the working mode, engine operating conditions and environmental conditions;

[0034] The injection parameters include: injection start point and injection pulse width; wherein the injection start point refers to the crankshaft angle from the engine crankshaft position corresponding to the fuel injection moment to the engine compression top dead center position; the injection pulse width refers to the time from the start of fuel injection to the end of fuel injection; the environmental conditions include: intake air temperature, coolant temperature and atmospheric pressure;

[0035] It should be noted that if the injection pulse width is 0, the corresponding injection system will not inject the corresponding fuel. By controlling the injection start point and injection pulse width of each injection system, different working modes of the mixed injection system can be achieved.

[0036] Specifically, in the 00 working mode, the injection start point and injection pulse width of low-pressure methanol are both 0, the injection start point and injection pulse width of high-pressure methanol are both 0, and only high-pressure diesel is injected; the injection start point and injection pulse width of high-pressure diesel are calculated according to the 00 working mode by the high-pressure diesel injection parameter calculation method;

[0037] In the 01 working mode, the injection start point and injection pulse width of high-pressure methanol are both 0, and only low-pressure methanol and high-pressure diesel are injected. The injection start point and injection pulse width of low-pressure methanol are calculated by the low-pressure methanol injection parameter calculation method according to the 01 working mode; the injection start point and injection pulse width of high-pressure diesel are calculated by the high-pressure diesel injection parameter calculation method according to the 01 working mode;

[0038] In the 10 working mode, the injection start point and injection pulse width of low-pressure methanol are both 0, and only high-pressure methanol and high-pressure diesel are injected. The injection start point and injection pulse width of high-pressure methanol are calculated according to the 10 working mode by the high-pressure methanol injection parameter calculation method. The injection start point and injection pulse width of high-pressure diesel are calculated according to the 10 working mode by the high-pressure diesel injection parameter calculation method.

[0039] In the 11 dual fuel mode, low pressure methanol, high pressure methanol and high pressure diesel are all injected. The injection start point and injection pulse width of low pressure methanol are calculated by the low pressure methanol injection parameter calculation method according to the 11 working mode; the injection start point and injection pulse width of high pressure methanol are calculated by the high pressure methanol injection parameter calculation method according to the 11 working mode; the injection start point and injection pulse width of high pressure diesel are calculated by the high pressure diesel injection parameter calculation method according to the 11 working mode;

[0040] The low-pressure methanol injection parameter calculation method includes: low-pressure methanol injection starting point calculation and low-pressure methanol injection pulse width calculation, and both include 01 working mode and 11 working mode, and the corresponding working mode is selected according to the working mode status word to calculate the injection parameters during operation;

[0041] In the 01 working mode and the 11 working mode, the low-pressure methanol injection starting point calculation includes: the low-pressure methanol injection starting point basic value calculation and the low-pressure methanol injection starting point correction value calculation;

[0042] The calculation of the low-pressure methanol injection starting point base value includes a low-pressure methanol injection starting point base value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the low-pressure methanol injection starting point base value;

[0043] The calculation of the correction value of the starting point of low-pressure methanol injection includes: a correction base value MAP and a correction value curve. The correction base value MAP includes: an intake temperature correction MAP, a coolant correction MAP and an atmospheric pressure correction MAP, and all of them take the engine speed and the accelerator pedal opening as inputs. The correction base value of the starting point of low-pressure methanol injection under the corresponding environmental conditions is output;

[0044] The correction curves include: an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and the intake air temperature, coolant temperature and atmospheric pressure are respectively used as inputs, and the correction coefficient of the low-pressure methanol injection starting point under the corresponding environmental conditions is output;

[0045] The product of the low-pressure methanol injection starting point correction base value and the low-pressure methanol injection starting point correction coefficient is the low-pressure methanol injection starting point correction value under the corresponding environmental conditions; the sum of the low-pressure methanol injection starting point base value and the low-pressure methanol injection starting point correction value is the low-pressure methanol injection starting point.

[0046] The low-pressure methanol injection pulse width calculation includes: low-pressure methanol substitution rate calculation, low-pressure methanol injection amount calculation and low-pressure methanol injection pulse width calculation; in the 01 working mode and the 11 working mode, the low-pressure methanol substitution rate calculation includes: low-pressure methanol substitution rate basic value calculation and low-pressure methanol substitution rate correction value; in the low-pressure methanol substitution rate basic value calculation, there is a low-pressure methanol substitution rate basic value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the low-pressure methanol substitution rate basic value;

[0047] The calculation of the low-pressure methanol substitution rate correction value includes: correction value MAP and correction value curve. The low-pressure methanol substitution rate correction value MAP includes intake temperature correction MAP, coolant correction MAP and atmospheric pressure correction MAP, and all of them take engine speed and accelerator pedal opening as input, and the low-pressure methanol substitution rate correction basic value under the corresponding environmental conditions is output.

[0048] The low-pressure methanol substitution rate correction curve includes: an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and the intake air temperature, coolant temperature and atmospheric pressure are respectively used as inputs, and the low-pressure methanol substitution rate correction coefficient under the corresponding environmental conditions is output;

[0049] The product of the low-pressure methanol substitution rate correction base value and the low-pressure methanol substitution rate correction coefficient is the low-pressure methanol substitution rate correction value under the corresponding environmental conditions; the sum of the low-pressure methanol substitution rate base value and the low-pressure methanol substitution rate correction value is the low-pressure methanol substitution rate.

[0050] The low-pressure methanol injection amount is calculated based on the low-pressure methanol replacement rate. The specific calculation method of the methanol injection amount is:

[0051]

[0052] In the formula, q Lm is the low-pressure methanol injection amount, q cyc is the cycle injection amount, is the low-pressure methanol substitution rate, Q d is the calorific value of diesel, Q m is the calorific value of methanol; the circulating injection amount q cyc It is the amount of fuel injection required for each cylinder in each working cycle during the operation of the engine, and its size can be determined according to the size of the accelerator pedal opening. During vehicle driving, the change in the accelerator pedal opening is reflected as the change in the cycle fuel injection amount. Therefore, the methanol injection amount will change with the change in the cycle fuel injection amount to maintain the desired methanol substitution rate.

[0053] The low-pressure methanol injection pulse width calculation includes the low-pressure methanol injection pulse width MAP. The input of MAP is the low-pressure methanol injection pressure and the low-pressure methanol injection amount, and the output is the low-pressure methanol injection pulse width. The value of the low-pressure methanol injection pulse width MAP can be preset in the MAP according to the characteristics of the low-pressure methanol nozzle. During the operation of the engine, the corresponding low-pressure methanol injection pulse width can be determined according to the low-pressure methanol pressure and the low-pressure methanol injection amount.

[0054] The integrated controller low-pressure methanol injection driver performs low-pressure methanol injection according to the injection starting point and injection pulse width of the low-pressure methanol.

[0055] The high-pressure methanol injection parameter calculation method includes: injection start point calculation and injection pulse width calculation, and both include 10 working modes and 11 working modes. During operation, the corresponding working mode is selected according to the working mode status word to calculate the injection parameters;

[0056] In both the 10th working mode and the 11th working mode, the high-pressure methanol injection start point calculation includes: the high-pressure methanol injection start point basic value calculation and the high-pressure methanol injection start point correction value calculation; the basic value calculation includes a high-pressure methanol injection start point basic value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the high-pressure methanol injection start point basic value;

[0057] The calculation of the correction value of the start point of high-pressure methanol injection includes a correction base value MAP and a correction value curve. The correction base value MAP of the start point of high-pressure methanol injection includes: intake temperature correction MAP, coolant correction MAP and atmospheric pressure correction MAP, and all of them take the engine speed and accelerator pedal opening as inputs, and the correction base value of the start point of high-pressure methanol injection under the corresponding environmental conditions is output;

[0058] The high-pressure methanol injection starting point correction curve includes: an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and takes the intake air temperature, coolant temperature and atmospheric pressure as inputs respectively, and the high-pressure methanol injection starting point correction coefficient under the corresponding environmental conditions is output.

[0059] The product of the high-pressure methanol injection starting point correction base value and the high-pressure methanol injection starting point correction coefficient is the high-pressure methanol injection starting point correction value corresponding to the environmental conditions;

[0060] The sum of the high-pressure methanol injection starting point basic value and the high-pressure methanol injection starting point correction value is the high-pressure methanol injection starting point;

[0061] The high-pressure methanol injection pulse width calculation includes the high-pressure methanol replacement rate calculation, the high-pressure methanol injection amount calculation and the high-pressure methanol injection pulse width calculation;

[0062] In working mode 10 and working mode 11, the high-pressure methanol substitution rate calculation includes the high-pressure methanol substitution rate base value calculation and the high-pressure methanol substitution rate correction value;

[0063] The high-pressure methanol substitution rate basic value calculation includes a high-pressure methanol substitution rate basic value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the high-pressure methanol substitution rate basic value;

[0064] The high-pressure methanol substitution rate correction value calculation includes a correction value MAP and a correction value curve. The high-pressure methanol substitution rate correction value MAP includes an intake temperature correction MAP, a coolant correction MAP and an atmospheric pressure correction MAP, and all of them take the engine speed and the accelerator pedal opening as inputs. The high-pressure methanol substitution rate correction base value under the corresponding environmental conditions is output;

[0065] The high-pressure methanol substitution rate correction curve includes an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and the intake air temperature, coolant temperature and atmospheric pressure are respectively used as inputs, and the high-pressure methanol substitution rate correction coefficient under the corresponding environmental conditions is output;

[0066] The product of the high-pressure methanol substitution rate correction base value and the high-pressure methanol substitution rate correction coefficient is the high-pressure methanol substitution rate correction value under the corresponding environmental conditions;

[0067] The sum of the basic value of high-pressure methanol substitution rate and the revised value of high-pressure methanol substitution rate is the high-pressure methanol substitution rate;

[0068] The high-pressure methanol injection amount is calculated based on the low-pressure methanol replacement rate. The high-pressure methanol injection amount is calculated as follows:

[0069]

[0070] In the formula, q Hm is the high-pressure methanol injection amount, q cyc is the cycle injection amount, is the high-pressure methanol substitution rate, Q d is the calorific value of diesel, Q m is the calorific value of methanol;

[0071] The high-pressure methanol injection pulse width calculation includes the high-pressure methanol injection pulse width MAP. The input of MAP is the high-pressure methanol injection pressure and the high-pressure methanol injection amount, and the output is the high-pressure methanol injection pulse width. The value of the high-pressure methanol injection pulse width MAP can be preset in the high-pressure methanol injection pulse width MAP according to the characteristics of the high-pressure methanol nozzle. During the operation of the engine, the corresponding high-pressure methanol injection pulse width can be determined according to the high-pressure methanol injection pressure and the high-pressure methanol injection amount.

[0072] The integrated controller high-pressure methanol injection drive module performs high-pressure methanol injection according to the high-pressure methanol injection starting point and injection pulse width.

[0073] The high-pressure diesel injection parameter calculation method includes: injection start point calculation and injection pulse width calculation, wherein the injection start point calculation includes: 00 working mode, 01 working mode, 10 working mode and 11 working mode, and the corresponding working mode is selected according to the working mode status word to calculate the injection start point during operation;

[0074] In all working modes, the high-pressure diesel injection start point calculation includes: high-pressure diesel injection start point basic value calculation and high-pressure diesel injection start point correction value calculation;

[0075] The high-pressure diesel injection starting point basic value calculation includes a high-pressure diesel injection starting point basic value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the high-pressure diesel injection starting point basic value;

[0076] The high-pressure diesel injection start point correction value calculation includes a correction base value MAP and a correction value curve. The high-pressure diesel injection start point correction base value MAP includes an intake temperature correction MAP, a coolant correction MAP and an atmospheric pressure correction MAP, and all of them take the engine speed and the accelerator pedal opening as inputs. The high-pressure diesel injection start point correction base value under the corresponding environmental conditions is output;

[0077] The high-pressure diesel injection start point correction curve includes: an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and the intake air temperature, coolant temperature and atmospheric pressure are respectively used as inputs, and the high-pressure diesel injection start point correction coefficient under the corresponding environmental conditions is output;

[0078] The product of the high-pressure diesel injection start point correction base value and the high-pressure diesel injection start point correction coefficient is the high-pressure diesel injection start point correction value corresponding to the environmental conditions;

[0079] The sum of the high-pressure diesel injection start point basic value and the high-pressure diesel injection start point correction value is the high-pressure diesel injection start point;

[0080] The high-pressure diesel injection pulse width calculation includes the high-pressure diesel injection amount calculation and the high-pressure methanol injection pulse width calculation. Since the diesel injection amount mainly depends on the methanol substitution amount, there is no need to perform mode-based control on the high-pressure diesel injection amount. The high-pressure diesel injection amount calculation calculates the diesel injection amount based on the low-pressure methanol substitution rate and the high-pressure methanol substitution rate. The specific calculation method is:

[0081]

[0082] In the formula, q d is the high-pressure diesel injection amount, q cyc is the cycle injection amount, is the low-pressure methanol substitution rate, is the high-pressure methanol substitution rate;

[0083] The high-pressure diesel injection pulse width calculation includes a high-pressure diesel injection pulse width MAP, the input of MAP is the high-pressure diesel injection pressure and the high-pressure diesel injection amount, and the output is the high-pressure diesel injection pulse width; the value of the high-pressure diesel injection pulse width MAP can be preset in the MAP according to the characteristics of the high-pressure diesel nozzle, and during the operation of the engine, the corresponding high-pressure methanol injection pulse width can be determined according to the high-pressure diesel injection pressure and the high-pressure diesel injection amount;

[0084] The integrated controller high pressure diesel injection drive module performs high pressure diesel injection according to the high pressure diesel injection start point and injection pulse width.

[0085] Beneficial effects of the present invention

[0086] 1. The mixed injection system of the present invention can distribute methanol fuel through a low-pressure methanol injection system and a high-pressure methanol injection system to achieve a high methanol substitution rate, and can be flexibly controlled according to the engine operating conditions.

[0087] 2. The mixed injection system of the present invention can realize multiple working modes, and can pre-match the best control parameters for each working mode in the control method, so that the engine can obtain the best operating performance in the corresponding working mode.

[0088] 3. The mixed injection system of the present invention combined with the collaborative control method of the present invention can set a suitable working mode according to the engine operating conditions, realize the collaborative operation of multiple working modes within the full range of operating conditions, make full use of the advantages of different working modes, and improve the operating performance of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Figure 1 Schematic diagram of the structure and principle of the mixed injection system of the present invention;

[0090] Figure 2 A schematic diagram of the structure of the integrated controller of the present invention;

[0091] Figure 3 A schematic diagram of the working mode of the mixed injection system of the present invention;

[0092] Figure 4 Schematic diagram of the method for calculating the high-pressure methanol injection pressure control parameters of the present invention;

[0093] Figure 5 Schematic diagram of the method for calculating the high-pressure diesel injection pressure control parameters of the present invention;

[0094] Figure 6 Schematic diagram of the method for calculating low-pressure methanol injection parameters of the present invention;

[0095] Figure 7 Schematic diagram of the method for calculating high-pressure methanol injection parameters of the present invention;

[0096] Figure 8 Schematic diagram of the method for calculating high-pressure diesel injection parameters of the present invention;

[0097] Engine-1, low-pressure methanol nozzle-2, low-pressure methanol common rail-3, constant pressure valve-4, low-pressure methanol pump-5, methanol fuel tank-6, high-pressure methanol nozzle-7, high-pressure methanol common rail-8, high-pressure methanol common rail pressure sensor-9, high-pressure methanol pump-10, methanol metering device-11, methanol cooling device-12, injector-13, high-pressure diesel common rail-14, high-pressure diesel common rail pressure sensor-15, high-pressure diesel pump-16, diesel metering device-17, diesel tank-18, integrated controller-19, DC power supply-20. DETAILED DESCRIPTION

[0098] The present invention is further described in detail below in conjunction with specific embodiments.

[0099] like Figure 1 As shown, a methanol-diesel dual-fuel engine mixed injection system includes: a low-pressure methanol injection system, a high-pressure methanol injection system, a high-pressure diesel injection system, an integrated controller 19 and a DC power supply 20.

[0100] The low-pressure methanol injection system comprises: a low-pressure methanol nozzle 2, a low-pressure methanol common rail 3, a constant pressure valve 4, a low-pressure methanol pump 5, and a methanol fuel tank 6;

[0101] Specifically, the low-pressure methanol nozzle 2 is installed on the engine intake manifold and connected to the low-pressure methanol common rail 3, the low-pressure methanol common rail 3 is connected to the constant pressure valve 4, the constant pressure valve 4 is connected to the low-pressure methanol pump 5, the low-pressure methanol pump 5 is connected to the methanol fuel tank 6, and the fuel return end of the constant pressure valve 4 is connected to the methanol fuel tank 6.

[0102] The high-pressure methanol injection system comprises: a methanol fuel tank 6, a high-pressure methanol pump 10, a high-pressure methanol common rail 8, a high-pressure methanol nozzle 7 and a methanol cooling device 12;

[0103] Specifically, the high-pressure methanol nozzle 7 is installed on the high-pressure methanol nozzle installation hole of the engine 1, the input end of the high-pressure methanol nozzle 7 is connected to the output end of the high-pressure methanol common rail 8, the fuel return end of the high-pressure methanol nozzle 7 is connected to the methanol cooling device 12, and the high-pressure methanol common rail 8 is equipped with a high-pressure methanol common rail pressure sensor 9 for collecting the high-pressure methanol injection pressure in the high-pressure methanol common rail (8); the input end of the high-pressure methanol common rail 8 is connected to the output end of the high-pressure methanol pump 10, and the high-pressure methanol pump 10 is equipped with a methanol metering device 11, and the amount of methanol entering the methanol common rail can be adjusted by controlling the methanol metering device 11, thereby realizing accurate control of the high-pressure methanol injection pressure; the input end of the high-pressure methanol pump 10 is connected to the methanol fuel tank 6, and the fuel return end of the high-pressure methanol pump is connected to the methanol cooling device 12;

[0104] The high-pressure diesel injection system includes: an injector 13, a high-pressure diesel common rail 14, a high-pressure diesel pump 16, and a diesel tank 18;

[0105] Specifically, the high-pressure diesel injector 13 is installed in the diesel injector installation hole at the center position of the cylinder head of the engine 1, and the input end of the high-pressure diesel injector 13 is connected to the output end of the high-pressure diesel common rail 14. A high-pressure diesel common rail pressure sensor 15 is installed on the high-pressure common rail 14 to collect the high-pressure diesel injection pressure in the high-pressure diesel common rail 15; the input end of the high-pressure common rail 14 is connected to the output end of the high-pressure diesel pump 16, and a diesel metering device 17 is installed on the high-pressure diesel pump 16. By controlling the diesel metering device 17, the amount of diesel entering the high-pressure diesel common rail can be adjusted, thereby realizing precise control of the high-pressure diesel injection pressure; the input end and the return oil end of the high-pressure diesel pump 16 are both connected to the diesel tank 18.

[0106] The integrated controller 19 is electrically connected to the high-pressure methanol common rail pressure sensor 9, the high-pressure methanol metering device 11, the high-pressure diesel common rail pressure sensor 15, the high-pressure diesel metering device 17, the low-pressure methanol nozzle 2, the high-pressure methanol nozzle 7, the high-pressure diesel injector 13, the DC power supply 20 and other sensors of the engine respectively; the integrated controller 19 is responsible for controlling the fuel injection pressure and fuel injection process of each subsystem of the mixed injection system;

[0107] like Figure 2 As shown, the integrated controller 19 includes a sensor signal conditioning module 201, a low-pressure methanol injection drive module 202, a high-pressure methanol injection drive module 203, a high-pressure diesel injection drive module 204, a microprocessor 205 and a power supply module 206;

[0108] The sensor signal conditioning module 201 conditions the sensor signal and transmits the signal to the microprocessor for real-time monitoring and control of the engine. The sensors include but are not limited to crankshaft position sensor, camshaft position sensor, intake air temperature sensor, coolant temperature sensor, atmospheric pressure sensor, high-pressure methanol pressure sensor, high-pressure diesel pressure sensor, oil pressure sensor, and oil temperature sensor. The integrated controller accurately identifies the engine phase through the engine crankshaft position sensor and camshaft position sensor, and can provide a unified injection start point reference for the low-pressure methanol injection system, the high-pressure methanol injection system, and the high-pressure diesel injection system. The low-pressure methanol injection system injects methanol during the engine intake stroke, and its injection start point range is 180 to 360° CABTDC. The high-pressure methanol injection system injects methanol during the power stroke, and its injection start point range is 0 to -180° CABTDC. The injection start point range of the high-pressure diesel injection system is 180 to -180° CABTDC.

[0109] The low-pressure methanol injection drive module 202 controls the low-pressure methanol nozzle to open quickly at the specified low-pressure methanol injection starting point according to the injection parameters, and accurately controls the opening time of the low-pressure methanol nozzle 2 (low-pressure methanol injection pulse width). The injection pulse width determines the injection amount of low-pressure methanol. The longer the pulse width, the more low-pressure methanol is injected into the intake manifold.

[0110] The high-pressure methanol driving module 203 controls the methanol injection pressure in the high-pressure methanol common rail according to the high-pressure methanol metering device 11, and controls the high-pressure methanol nozzle to open quickly at the specified high-pressure methanol injection starting point according to the injection parameters, and accurately controls the nozzle opening time (high-pressure methanol injection pulse width), thereby accurately controlling the high-pressure methanol injection amount;

[0111] The high-pressure diesel injection drive module 204 controls the diesel injection pressure in the high-pressure diesel common rail 14 by controlling the high-pressure diesel metering device 17, and controls the injector 13 to open quickly at the specified injection start point according to the injection parameters, and accurately controls the opening time of the injector 13 (high-pressure diesel injection pulse width), thereby accurately controlling the high-pressure diesel injection amount;

[0112] The injection pressure of the low-pressure methanol injection system is controlled by a constant pressure valve. When the pressure in the low-pressure methanol common rail exceeds the constant pressure valve threshold of 0.45Mpa, the low-pressure methanol will flow back to the methanol tank through the fuel return end of the constant pressure valve, thereby maintaining the methanol injection pressure in the low-pressure methanol common rail.

[0113] The injection pressure of the high-pressure methanol injection system is closed-loop controlled by an integrated controller; a control method for the high-pressure methanol injection pressure is stored and executed in the integrated controller, including high-pressure methanol injection pressure target value calculation and a high-pressure methanol injection pressure controller, such as Figure 3 As shown;

[0114] The high-pressure methanol injection pressure controller adopts a PID controller, which can close-loop adjust the PWM parameters of the high-pressure methanol injection pressure, and the PWM parameters include duty cycle and frequency; the high-pressure methanol drive module 203 generates a correct PWM drive signal according to the PWM parameters to control the high-pressure methanol metering device 11, thereby adjusting the amount of methanol entering the high-pressure methanol common rail 8 from the high-pressure methanol pump 10, so that the pressure in the high-pressure methanol common rail 8 is stabilized at the high-pressure methanol target injection pressure; the target injection pressure of the high-pressure methanol injection system can be pre-set in the high-pressure methanol injection pressure MAP according to the engine working conditions, ranging from 40 to 160Mpa. In order to prevent the methanol from vaporizing during the reflux process, the methanol refluxed from the high-pressure methanol nozzle and the high-pressure methanol pump is cooled by the cooling device 12 and then refluxed to the methanol fuel tank.

[0115] The injection pressure of the high-pressure diesel injection system is closed-loop controlled by an integrated controller. The control method of the high-pressure diesel injection pressure is stored and run in the integrated controller, including the high-pressure diesel injection pressure target value calculation and the high-pressure diesel injection pressure controller, such as Figure 4 As shown. The high-pressure diesel injection pressure target value calculation includes a high-pressure diesel injection pressure MAP, the input is the engine speed and the accelerator pedal opening, and the output is the high-pressure diesel target injection pressure. The appropriate high-pressure diesel target injection pressure can be determined according to the engine operating conditions. The high-pressure diesel injection pressure controller adopts a PID controller, which can adjust the high-pressure diesel injection pressure PWM parameters in a closed loop. The high-pressure diesel drive module 204 generates a correct PWM drive signal according to the PWM parameters to control the high-pressure methanol metering device 17, so that the pressure in the high-pressure diesel common rail 14 is stabilized at the high-pressure diesel target injection pressure. The injection pressure of the high-pressure diesel injection system can be pre-set according to the engine operating conditions, ranging from 40 to 160Mpa.

[0116] The power supply module 206 is electrically connected to the DC power supply 20 to supply power to all drive modules of the integrated controller 19 and sensors on the engine.

[0117] A methanol-diesel dual-fuel engine mixed injection system coordinated control method, by storing and running the mixed injection system coordinated control method in the microprocessor 206 to control the injection parameters of each injection system, can achieve four working modes, the specific steps are:

[0118] S1: Determine the working mode according to the engine working condition;

[0119] Specifically, a working mode calculation is stored and executed in the microprocessor 205, and the working mode calculation includes a working mode MAP, the input of the working mode MAP is the engine speed and the throttle opening, and the output value of the MAP is the working mode status word;

[0120] The working mode status word is a binary number, which is used to select the working mode in the injection parameter calculation method; wherein the working mode status word 00 represents the pure diesel working mode, 01 represents the reactive controlled compression combustion working mode of methanol intake port injection + in-cylinder diesel ignition, 10 represents the diffusion combustion working mode of in-cylinder direct injection diesel + high-pressure methanol injection, and 11 represents the mixed combustion working mode of methanol intake port injection + in-cylinder direct injection diesel ignition + high-pressure methanol injection;

[0121] The working mode MAP can be used to pre-set the appropriate working mode during the engine operation according to the engine working conditions; it should be noted that in the starting condition, the 00 pure diesel working mode is used by default to ensure the smooth start of the engine;

[0122] S2. Calculate the injection parameters according to the working mode, engine working condition and environmental conditions. The injection parameters include: injection start point and injection pulse width; the injection start point refers to the crankshaft angle from the engine crankshaft position corresponding to the fuel injection moment to the engine compression top dead center position; the injection pulse width refers to the time from the start of fuel injection to the end of fuel injection. It should be noted that if the injection pulse width is 0, the corresponding injection system will not inject the corresponding fuel. By controlling the injection start point and injection pulse width of each injection system, different working modes of the mixed injection system can be realized, such as Figure 5 As shown;

[0123] Specifically, in the 00 working mode, the injection start point and injection pulse width of low-pressure methanol are both 0, the injection start point and injection pulse width of high-pressure methanol are both 0, and only high-pressure diesel is injected; the injection start point and injection pulse width of high-pressure diesel are calculated according to the 00 working mode by the high-pressure diesel injection parameter calculation method;

[0124] In the 01 working mode, the injection start point and injection pulse width of high-pressure methanol are both 0, and only low-pressure methanol and high-pressure diesel are injected. The injection start point and injection pulse width of low-pressure methanol are calculated by the low-pressure methanol injection parameter calculation method according to the 01 working mode; the injection start point and injection pulse width of high-pressure diesel are calculated by the high-pressure diesel injection parameter calculation method according to the 01 working mode;

[0125] In the 10 working mode, the injection start point and injection pulse width of low-pressure methanol are both 0, and only high-pressure methanol and high-pressure diesel are injected. The injection start point and injection pulse width of high-pressure methanol are calculated according to the 10 working mode by the high-pressure methanol injection parameter calculation method. The injection start point and injection pulse width of high-pressure diesel are calculated according to the 10 working mode by the high-pressure diesel injection parameter calculation method.

[0126] In the 11 dual fuel mode, low pressure methanol, high pressure methanol and high pressure diesel are all injected. The injection start point and injection pulse width of low pressure methanol are calculated by the low pressure methanol injection parameter calculation method according to the 11 working mode. The injection start point and injection pulse width of high pressure methanol are calculated by the high pressure methanol injection parameter calculation method according to the 11 working mode. The injection start point and injection pulse width of high pressure diesel are calculated by the high pressure diesel injection parameter calculation method according to the 11 working mode.

[0127] like Figure 6As shown, the low-pressure methanol injection parameter calculation method includes injection start point calculation and injection pulse width calculation, and both include 01 working mode and 11 working mode. During operation, the corresponding working mode is selected according to the working mode status word to calculate the injection parameters. In 01 working mode and 11 working mode, the low-pressure methanol injection start point calculation includes low-pressure methanol injection start point basic value calculation and low-pressure methanol injection start point correction value calculation. The basic value calculation includes a low-pressure methanol injection start point basic value MAP, whose input is the engine speed and accelerator pedal opening, and the MAP output value is the low-pressure methanol injection start point basic value. The low-pressure methanol injection start point correction value calculation includes a correction base value MAP and a correction value curve. The low-pressure methanol injection start point correction base value MAP includes an intake temperature correction MAP, a coolant correction MAP and an atmospheric pressure correction MAP, and both use the engine speed and the accelerator pedal opening as inputs, and the low-pressure methanol injection start point correction base value under the corresponding environmental conditions is output. The low-pressure methanol injection starting point correction curve includes an intake temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and takes the intake temperature, coolant temperature and atmospheric pressure as inputs respectively, and the low-pressure methanol injection starting point correction coefficient under the corresponding environmental conditions is output. The product of the low-pressure methanol injection starting point correction base value and the low-pressure methanol injection starting point correction coefficient is the low-pressure methanol injection starting point correction value under the corresponding environmental conditions. The sum of the low-pressure methanol injection starting point base value and the low-pressure methanol injection starting point correction value is the low-pressure methanol injection starting point.

[0128] The low-pressure methanol injection pulse width calculation includes low-pressure methanol substitution rate calculation, low-pressure methanol injection amount calculation and low-pressure methanol injection pulse width calculation. In the 01 working mode and the 11 working mode, the low-pressure methanol substitution rate calculation includes the low-pressure methanol substitution rate base value calculation and the low-pressure methanol substitution rate correction value module. There is a low-pressure methanol substitution rate base value MAP in the low-pressure methanol substitution rate base value calculation, and its input is the engine speed and the accelerator pedal opening, and the MAP output value is the low-pressure methanol substitution rate base value. The low-pressure methanol substitution rate correction value calculation includes the correction value MAP and the correction value curve. The low-pressure methanol substitution rate correction value MAP includes the intake temperature correction MAP, the coolant correction MAP and the atmospheric pressure correction MAP, and all of them take the engine speed and the accelerator pedal opening as input, and the low-pressure methanol substitution rate correction base value under the corresponding environmental conditions is output. The low-pressure methanol substitution rate correction curve includes the intake temperature correction curve, the coolant temperature correction curve and the atmospheric pressure correction curve, and takes the intake temperature, the coolant temperature and the atmospheric pressure as input respectively, and the low-pressure methanol substitution rate correction coefficient under the corresponding environmental conditions is output. The product of the low-pressure methanol substitution rate correction base value and the low-pressure methanol substitution rate correction coefficient is the low-pressure methanol substitution rate correction value under the corresponding environmental conditions. The sum of the low-pressure methanol substitution rate base value and the low-pressure methanol substitution rate correction value is the low-pressure methanol substitution rate.

[0129] The low-pressure methanol injection amount is calculated based on the low-pressure methanol replacement rate. The specific calculation method of the methanol injection amount is:

[0130]

[0131] In the formula, q Lm is the low-pressure methanol injection amount, q cyc is the cycle injection amount, is the low-pressure methanol substitution rate, Q d is the calorific value of diesel, Q m is the calorific value of methanol.

[0132] Cycle injection quantity q cyc It is the amount of fuel injection required for each cylinder in each working cycle during the operation of the engine. Its size can be determined according to the size of the accelerator pedal opening. During vehicle driving, changes in the accelerator pedal opening are reflected in changes in the cycle injection amount. Therefore, the methanol injection amount will change with the change in the cycle injection amount to maintain the desired methanol substitution rate.

[0133] The low-pressure methanol injection pulse width calculation includes the low-pressure methanol injection pulse width MAP. The input of MAP is the low-pressure methanol injection pressure and the low-pressure methanol injection amount, and the output is the low-pressure methanol injection pulse width. The value of the low-pressure methanol injection pulse width MAP can be preset in the MAP according to the characteristics of the low-pressure methanol nozzle. During the operation of the engine, the corresponding low-pressure methanol injection pulse width can be determined according to the low-pressure methanol pressure and the low-pressure methanol injection amount.

[0134] The integrated controller low-pressure methanol injection drive module performs low-pressure methanol injection according to the injection starting point and injection pulse width of the low-pressure methanol.

[0135] like Figure 7As shown, the high-pressure methanol injection parameter calculation method includes injection start point calculation and injection pulse width calculation, and both include 10 working modes and 11 working modes. During operation, the corresponding working mode is selected according to the working mode status word to calculate the injection parameters. In working modes 10 and 11, the high-pressure methanol injection start point calculation includes high-pressure methanol injection start point basic value calculation and high-pressure methanol injection start point correction value calculation. The basic value calculation includes a high-pressure methanol injection start point basic value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the high-pressure methanol injection start point basic value. The high-pressure methanol injection start point correction value calculation includes a correction base value MAP and a correction value curve. The high-pressure methanol injection start point correction base value MAP includes an intake temperature correction MAP, a coolant correction MAP, and an atmospheric pressure correction MAP, and both use the engine speed and the accelerator pedal opening as inputs, and the high-pressure methanol injection start point correction base value under the corresponding environmental conditions is output. The high-pressure methanol injection start point correction curve includes an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and takes the intake air temperature, coolant temperature and atmospheric pressure as inputs respectively, and the high-pressure methanol injection start point correction coefficient under the corresponding environmental conditions is output. The product of the high-pressure methanol injection start point correction base value and the high-pressure methanol injection start point correction coefficient is the high-pressure methanol injection start point correction value under the corresponding environmental conditions. The sum of the high-pressure methanol injection start point base value and the high-pressure methanol injection start point correction value is the high-pressure methanol injection start point.

[0136] The high-pressure methanol injection pulse width calculation includes the high-pressure methanol substitution rate calculation, the high-pressure methanol injection amount calculation and the high-pressure methanol injection pulse width calculation. In the 10 working mode and the 11 working mode, the high-pressure methanol substitution rate calculation includes the high-pressure methanol substitution rate base value calculation and the high-pressure methanol substitution rate correction value module. There is a high-pressure methanol substitution rate base value MAP in the high-pressure methanol substitution rate base value calculation, and its input is the engine speed and the accelerator pedal opening, and the MAP output value is the high-pressure methanol substitution rate base value. The high-pressure methanol substitution rate correction value calculation includes the correction value MAP and the correction value curve. The high-pressure methanol substitution rate correction value MAP includes the intake temperature correction MAP, the coolant correction MAP and the atmospheric pressure correction MAP, and all of them take the engine speed and the accelerator pedal opening as input, and the high-pressure methanol substitution rate correction base value under the corresponding environmental conditions is output. The high-pressure methanol substitution rate correction curve includes the intake temperature correction curve, the coolant temperature correction curve and the atmospheric pressure correction curve, and takes the intake temperature, the coolant temperature and the atmospheric pressure as input respectively, and the high-pressure methanol substitution rate correction coefficient under the corresponding environmental conditions is output. The product of the high-pressure methanol substitution rate correction base value and the high-pressure methanol substitution rate correction coefficient is the high-pressure methanol substitution rate correction value under the corresponding environmental conditions. The sum of the high-pressure methanol substitution rate base value and the high-pressure methanol substitution rate correction value is the high-pressure methanol substitution rate.

[0137] The high-pressure methanol injection amount is calculated based on the low-pressure methanol replacement rate. The high-pressure methanol injection amount is calculated as follows:

[0138]

[0139] Among them, q Hm is the high-pressure methanol injection amount, q cyc is the cycle injection amount, is the high-pressure methanol substitution rate, Q d is the calorific value of diesel, Q m is the calorific value of methanol.

[0140] The high-pressure methanol injection pulse width calculation includes the high-pressure methanol injection pulse width MAP. The input of MAP is the high-pressure methanol injection pressure and the high-pressure methanol injection amount, and the output is the high-pressure methanol injection pulse width. The value of the high-pressure methanol injection pulse width MAP can be preset in the MAP according to the characteristics of the high-pressure methanol nozzle. During the operation of the engine, the corresponding high-pressure methanol injection pulse width can be determined according to the high-pressure methanol injection pressure and the high-pressure methanol injection amount.

[0141] The integrated controller high-pressure methanol injection drive module performs high-pressure methanol injection according to the high-pressure methanol injection starting point and injection pulse width.

[0142] like Figure 8 As shown, the high-pressure diesel injection parameter calculation method includes injection start point calculation and injection pulse width calculation, wherein the injection start point calculation includes 00 working mode, 01 working mode, 10 working mode and 11 working mode, and the corresponding working mode is selected according to the working mode status word to calculate the injection start point during operation. In all working modes, the high-pressure diesel injection start point calculation includes high-pressure diesel injection start point basic value calculation and high-pressure diesel injection start point correction value calculation. The basic value calculation includes a high-pressure diesel injection start point basic value MAP, whose input is the engine speed and the accelerator pedal opening, and the MAP output value is the high-pressure diesel injection start point basic value. The high-pressure diesel injection start point correction value calculation includes a correction base value MAP and a correction value curve. The high-pressure diesel injection start point correction base value MAP includes an intake temperature correction MAP, a coolant correction MAP and an atmospheric pressure correction MAP, and all of them take the engine speed and the accelerator pedal opening as inputs, and the high-pressure diesel injection start point correction base value under the corresponding environmental conditions is output. The high-pressure diesel injection start point correction curve includes an intake air temperature correction curve, a coolant temperature correction curve and an atmospheric pressure correction curve, and takes the intake air temperature, coolant temperature and atmospheric pressure as inputs respectively, and the high-pressure diesel injection start point correction coefficient under the corresponding environmental conditions is output. The product of the high-pressure diesel injection start point correction base value and the high-pressure diesel injection start point correction coefficient is the high-pressure diesel injection start point correction value under the corresponding environmental conditions. The sum of the high-pressure diesel injection start point base value and the high-pressure diesel injection start point correction value is the high-pressure diesel injection start point.

[0143] The high-pressure diesel injection pulse width calculation includes the high-pressure diesel injection amount calculation and the high-pressure methanol injection pulse width calculation. Since the diesel injection amount mainly depends on the methanol substitution amount, there is no need to perform mode-based control on the high-pressure diesel injection amount. The high-pressure diesel injection amount calculation calculates the diesel injection amount based on the low-pressure methanol substitution rate and the high-pressure methanol substitution rate. The specific calculation method is:

[0144]

[0145] In the formula, q d is the high-pressure diesel injection amount, q cyc is the cycle injection amount, is the low-pressure methanol substitution rate, is the high-pressure methanol substitution rate.

[0146] The integrated controller high pressure diesel injection drive module performs high pressure diesel injection according to the high pressure diesel injection start point and injection pulse width.

[0147] Through the above-mentioned collaborative control method, by controlling the injection parameters, the methanol-diesel mixed injection system can achieve 4 working modes. The appropriate working mode can be set according to the engine working condition. In each working mode, the best control parameters can be matched according to the engine working condition and environmental conditions, so that the engine can adapt to the working condition and environmental conditions in multiple working modes to achieve optimized operation. The mixed injection system and collaborative control method provided by the present invention can comprehensively utilize the advantages of different working modes to achieve efficient and clean combustion of the methanol-diesel engine at the highest possible methanol substitution rate.

[0148] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A methanol-diesel dual-fuel engine mixed injection system, characterized in that: The system comprises a low-pressure methanol injection system, a high-pressure methanol injection system, a high-pressure diesel injection system, an integrated controller (19), and a direct current power supply (20). The low-pressure methanol injection system injects methanol into an intake manifold during an intake stroke of an engine; the high-pressure methanol injection system can directly inject high-pressure methanol into a cylinder during a power stroke of an engine; the high-pressure diesel injection system directly injects high-pressure diesel into a cylinder for igniting methanol or directly operating in a pure diesel mode; the low-pressure methanol injection system, the high-pressure methanol injection system, and the high-pressure diesel injection system are all electrically connected to the integrated controller, and the integrated controller (19) is electrically connected to the direct current power supply (20).

2. A methanol-diesel dual-fuel engine mixed injection system according to claim 1, characterized in that: The low-pressure methanol injection system comprises: a low-pressure methanol nozzle (2), a low-pressure methanol common rail (3), a constant pressure valve (4), a low-pressure methanol pump (5), and a methanol fuel tank (6); the low-pressure methanol nozzle (2) is installed on the engine intake manifold and connected to the low-pressure methanol common rail (3), the low-pressure methanol common rail (3) is connected to the constant pressure valve (4), the constant pressure valve (4) is connected to the low-pressure methanol pump (5), and the low-pressure methanol pump (5) is connected to the methanol fuel tank (6).

3. A methanol-diesel dual-fuel engine mixed injection system according to claim 1, characterized in that: The high-pressure methanol injection system comprises: a methanol fuel tank (6), a high-pressure methanol nozzle (7), a high-pressure methanol common rail (8), a high-pressure methanol common rail pressure sensor (9), a high-pressure methanol pump (10), a methanol metering device (11), and a methanol cooling device (12); the high-pressure methanol nozzle (7) is installed in a high-pressure methanol nozzle installation hole on a cylinder head of an engine (1) and is connected to the high-pressure methanol common rail (8); the high-pressure methanol common rail (8) is connected to the high-pressure methanol pump (10), and the high-pressure methanol pump (10) is connected to a methanol tank (6); the methanol refluxed from the high-pressure methanol nozzle (7) and the high-pressure methanol pump (10) is cooled by the methanol cooling device (12) and then refluxed to the methanol fuel tank (6); the high-pressure methanol common rail (8) is equipped with a high-pressure methanol common rail pressure sensor (9), and the high-pressure methanol pump (10) is equipped with a methanol metering device (11).

4. A methanol-diesel dual-fuel engine mixed injection system according to claim 1, characterized in that: The high-pressure diesel injection system comprises: an injector (13), a high-pressure diesel common rail (14), a high-pressure diesel common rail pressure sensor (15), a high-pressure diesel pump (16), a diesel metering device (17), and a diesel tank (18); the injector (13) is mounted on a cylinder head of an engine (1) and connected to the high-pressure diesel common rail (14); the high-pressure diesel common rail (14) is connected to the high-pressure diesel pump (16); the high-pressure diesel pump (16) is connected to the diesel tank (18); the oil return pipes of the injector (13) and the high-pressure diesel pump (16) are both connected to the diesel tank (18); the high-pressure diesel common rail (14) is equipped with a high-pressure diesel common rail pressure sensor (15); the high-pressure diesel pump (16) is equipped with a diesel metering device (17).

5. A methanol-diesel dual-fuel engine mixed injection system according to claim 1, characterized in that: The integrated controller (19) comprises: a sensor signal conditioning module (201), a low-pressure methanol injection system driving module (202), a high-pressure methanol injection system driving module (203), a high-pressure diesel injection system driving module (204), a microprocessor (205) and a power supply module (206); The sensor signal conditioning module (201) conditions the sensor signal and transmits it to the microprocessor (205); A low-pressure methanol injection system drive module (202), a high-pressure methanol injection system drive module (203), and a high-pressure diesel injection system drive module (204) control fuel injectors of corresponding systems according to injection parameters; The power supply module (206) is electrically connected to the DC power supply 20.

6. A coordinated control method for a methanol-diesel dual fuel mixed injection system, characterized in that: The methanol-diesel dual fuel mixed injection system is as described in any one of claims 1 to 5 above, and the coordinated control method comprises the following steps: S1. determining a working mode according to the working condition of the engine (1); S2. Calculate injection parameters according to working mode, engine operating conditions and environmental conditions.

7. The coordinated control method of a methanol-diesel dual fuel mixed injection system according to claim 6, characterized in that: The working mode is represented by a working mode status word, including: 00, 01, 10, 11; among which 00 represents a pure diesel working mode, 01 represents a reactive controlled compression combustion working mode in which methanol intake port injection and in-cylinder diesel ignition are performed together, 10 represents a diffusion combustion working mode in which direct injection of diesel and high-pressure methanol injection work together, and 11 represents a mixed combustion working mode in which methanol intake port injection, direct injection of diesel and high-pressure methanol injection work together.

8. The coordinated control method of a methanol-diesel dual fuel mixed injection system according to claim 7, characterized in that: The specific method for calculating the injection parameters according to the working mode, engine operating conditions and environmental conditions is as follows: In the 00 working mode, the injection start point and the injection pulse width of low-pressure methanol are both 0, the injection start point and the injection pulse width of high-pressure methanol are both 0, only high-pressure diesel is injected, and the injection start point and the injection pulse width of high-pressure diesel are calculated according to the 00 working mode by the high-pressure diesel injection parameter calculation method; In the 01 working mode, the injection start point and the injection pulse width of high-pressure methanol are both 0, and only low-pressure methanol and high-pressure diesel are injected. The injection start point and the injection pulse width of low-pressure methanol are calculated by the low-pressure methanol injection parameter calculation method according to the 01 working mode, and the injection start point and the injection pulse width of high-pressure diesel are calculated by the high-pressure diesel injection parameter calculation method according to the 01 working mode; In the 10 working modes, the injection start point and the injection pulse width of low-pressure methanol are both 0, and only high-pressure methanol and high-pressure diesel are injected. The injection start point and the injection pulse width of high-pressure methanol are calculated by the high-pressure methanol injection parameter calculation method according to the 10 working modes, and the injection start point and the injection pulse width of high-pressure diesel are calculated by the high-pressure diesel injection parameter calculation method according to the 10 working modes; In the 11 working mode, low-pressure methanol, high-pressure methanol and high-pressure diesel are all injected, the injection starting point of low-pressure methanol and the injection pulse width of low-pressure methanol are calculated by the low-pressure methanol injection parameter calculation method according to the 11 working mode, the injection starting point of high-pressure methanol and the injection pulse width of high-pressure methanol are calculated by the high-pressure methanol injection parameter calculation method according to the 11 working mode, and the injection starting point of high-pressure diesel and the injection pulse width of high-pressure diesel are calculated by the high-pressure diesel injection parameter calculation method according to the 11 working mode.

9. The coordinated control method of a methanol-diesel dual fuel mixed injection system according to claim 8, characterized in that: The low-pressure methanol injection parameter calculation method includes: injection start point calculation and injection pulse width calculation, both of which include 01 working mode and 11 working mode; In the 01 working mode and the 11 working mode, the low-pressure methanol injection starting point calculation includes the low-pressure methanol injection starting point basic value calculation and the low-pressure methanol injection starting point correction value calculation; the sum of the low-pressure methanol injection starting point basic value and the low-pressure methanol injection starting point correction value is the low-pressure methanol injection starting point; The low-pressure methanol injection pulse width is calculated based on the methanol injection amount according to the low-pressure methanol replacement rate, and then the required low-pressure methanol injection pulse width is determined according to the low-pressure methanol injection amount; the specific calculation method of the low-pressure methanol injection amount is: In the formula, q Lm is the low-pressure methanol injection amount, q cyc is the cycle injection amount, is the low-pressure methanol substitution rate, Q d is the calorific value of diesel, Q m is the calorific value of methanol; The high-pressure methanol injection parameter calculation method includes high-pressure methanol injection start point calculation and high-pressure methanol injection pulse width calculation, both of which include 10 working modes and 11 working modes; The high-pressure methanol injection start point calculation includes the high-pressure methanol injection start point basic value calculation and the high-pressure methanol injection start point correction value calculation in both the 10 working mode and the 11 working mode. The high-pressure methanol injection start point basic value and the high-pressure methanol injection start point correction value are the high-pressure methanol injection start point. The high-pressure methanol injection pulse width calculation includes the high-pressure methanol substitution rate calculation, the high-pressure methanol injection amount calculation and the high-pressure methanol injection pulse width calculation. In the 10 working mode and the 11 working mode, the high-pressure methanol substitution rate calculation includes the high-pressure methanol substitution rate base value calculation and the high-pressure methanol substitution rate correction value calculation. The high-pressure methanol injection amount calculation calculates the high-pressure methanol injection amount according to the high-pressure methanol substitution rate, and then determines the required high-pressure methanol injection pulse width according to the high-pressure methanol injection amount. The specific calculation method of the high-pressure methanol injection amount is: In the formula, q Hm is the high-pressure methanol injection amount, q cyc is the cycle injection amount, is the high-pressure methanol substitution rate, Q d is the calorific value of diesel, Q m is the calorific value of methanol; The high-pressure diesel injection parameter calculation method includes high-pressure diesel injection start point calculation and high-pressure diesel injection pulse width calculation, wherein the high-pressure diesel injection start point calculation includes 00 working mode, 01 working mode, 10 working mode and 11 working mode, while the high-pressure diesel injection pulse width calculation does not distinguish between working modes; The high-pressure diesel injection start point calculation includes the high-pressure diesel injection start point basic value calculation and the high-pressure diesel injection start point correction value calculation in all working modes. The sum of the high-pressure diesel injection start point basic value and the high-pressure diesel injection start point correction value is the high-pressure diesel injection start point. The high-pressure diesel injection pulse width calculation includes the high-pressure diesel injection amount calculation and the high-pressure methanol injection pulse width calculation. The high-pressure diesel injection amount calculation calculates the diesel injection amount according to the low-pressure methanol substitution rate and the high-pressure methanol substitution rate. The high-pressure diesel injection pulse width calculation determines the required high-pressure diesel injection pulse width according to the high-pressure diesel injection amount. The high-pressure diesel injection amount calculation method is specifically as follows: In the formula, q d is the high-pressure diesel injection amount, q cyc is the cycle injection amount, is the low-pressure methanol substitution rate, is the high-pressure methanol substitution rate.

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