CN110513178B - Fuel injection control system and method for DPF active regeneration - Google Patents

Fuel injection control system and method for DPF active regeneration Download PDF

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CN110513178B
CN110513178B CN201910744760.6A CN201910744760A CN110513178B CN 110513178 B CN110513178 B CN 110513178B CN 201910744760 A CN201910744760 A CN 201910744760A CN 110513178 B CN110513178 B CN 110513178B
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fuel
module
injection
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dpf
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CN110513178A (en
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韩虎
程欢
周杰敏
张衡
朱丹丹
张鑫
谢文
蒋学锋
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Dongfeng Commercial Vehicle Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Processes For Solid Components From Exhaust (AREA)

Abstract

A fuel injection control system and method for DPF active regeneration, the control system includes sensor module, signal acquisition module, working mode division module, mode dispatch management module, order driving module, executor module and DPF regeneration judgement module, the sensor module is connected with the signal acquisition module, the signal acquisition module is connected with the mode dispatch management module, the mode dispatch management module is connected with the order driving module, the order driving module is connected with the executor module, the working mode division module is connected with the mode dispatch management module, the DPF regeneration judgement module is connected with the mode dispatch management module; the method comprises the following steps: entering a maintenance mode, entering a pressure build-up mode, entering an injection mode, entering a self-cleaning mode and finishing a self-cleaning function. The active regeneration function of the DPF is realized; the nozzle and the fuel pipeline on the side of the exhaust pipe can be automatically cleaned, and the problem that the nozzle and the nearby pipelines are blocked due to high-temperature cracking of fuel remained in the pipelines is avoided.

Description

Fuel injection control system and method for DPF active regeneration
Technical Field
The invention relates to a fuel injection system for DPF, in particular to a fuel injection control system and method for DPF active regeneration, and belongs to the technical field of automobile parts.
Background
Particulate matter PM and nitrogen oxide NOx are two main pollutants of a diesel engine, and in order to deal with the problem of environmental pollution, China has a strict national six-diesel-engine emission regulation in history. Currently, diesel particulate filter (dpf) technology is considered to be the most effective means for solving the problem of diesel particulate emission, and a honeycomb-shaped ceramic carrier structure filters and traps particulate matters in diesel exhaust through diffusion, deposition and impact mechanisms. However, during the filtering and trapping process, as the particulate matter continues to accumulate in the DPF, the exhaust back pressure of the diesel engine rises, resulting in deterioration of the diesel engine performance; therefore, it is necessary to periodically remove the particulate matter in the DPF to restore the DPF to an initial state and regenerate the DPF.
For a heavy diesel engine, to realize the active regeneration of the DPF, fuel oil is mainly injected into the front end of a Diesel Oxidation Catalyst (DOC) installed in an exhaust pipe, and a large amount of heat is released through the oxidation action of the DOC to raise the exhaust temperature inside the DPF at the downstream so as to achieve the purpose of high-temperature oxidation of particulate matters. In order to realize this function, it is necessary to provide a control system and a control method for injecting fuel into an exhaust pipe.
Chinese invention patent system and method for controlling exhaust gas temperature during regeneration of a particulate matter filter (patent No. 201110007431.7, publication No. CN 102305118B) discloses a system and method for controlling exhaust gas temperature during regeneration of a particulate matter filter, wherein an engine control system includes an injection determination module that determines a desired amount of hydrocarbons to be injected into exhaust gas produced by an engine based on an exhaust flow rate, a correction factor determination module that determines a correction factor for the desired amount of HC based on an engine speed and an engine load, and a regeneration control module that controls injection of an adjusted amount of HC into the exhaust gas during regeneration of the particulate matter filter, wherein the adjusted amount of HC is based on the desired amount of HC and the correction factor. The system is suitable for engines which adopt in-cylinder injection to realize DPF active regeneration, but for heavy-duty diesel engines, the adoption of the system and the method can bring about the problem of engine oil dilution.
Chinese patent invention device for regeneration, temperature loading and/or thermal management and associated injection valve and method (patent No. 200780018911.5, publication No. CN 101454546B) discloses a device for regeneration, temperature loading and/or thermal management and associated injection valve and method having at least one injection valve, preferably injecting a fluid, in particular a fuel, into the exhaust system in an oscillating operation, for example, depending on the pressure of the fluid fed, for the active regeneration function of a DPF. The utility model discloses a though can realize realizing the initiative regeneration function through the mode that sprays fuel to the blast pipe and realize DPF, this regeneration fuel sprays the pipeline and does not have self-cleaning function, arouses the jam of blast pipe side nozzle and pipeline easily.
Disclosure of Invention
The invention aims to provide a fuel injection control system and method for DPF active regeneration, aiming at the defects that the existing DPF active regeneration technology can cause engine oil dilution, or a fuel injection pipeline has no self-cleaning function, and the like.
In order to achieve the purpose, the technical solution of the invention is as follows: a fuel injection control system for DPF active regeneration is used in a fuel injection system, the fuel injection system comprises a fuel tank, a low-pressure fuel pump, a nozzle, an air compressor and a gas storage tank, the fuel tank is connected with the nozzle through the low-pressure fuel pump, a fuel filter is connected on a pipeline connected with the low-pressure fuel pump and the nozzle, the air compressor is connected with the gas storage tank, the gas storage tank is connected with the nozzle, the fuel injection control system comprises a sensor module, a signal acquisition module, a working mode division module, a mode scheduling management module, an instruction driving module, an actuator module and a DPF regeneration judgment module, the sensor module is connected with the signal acquisition module, the signal acquisition module is connected with the mode scheduling management module, the mode scheduling management module is connected with the instruction driving module, the DPF regeneration judging module is connected with the mode scheduling management module;
the sensor module comprises a fuel temperature sensor and an upstream fuel pressure sensor and a downstream fuel pressure sensor, the actuator module comprises three actuators of a pressure regulating valve, a metering valve and a cleaning valve, the metering valve is arranged on a pipeline for connecting a low-pressure oil pump and a nozzle, the cleaning valve is arranged on a pipeline for connecting an air storage tank and the nozzle, the fuel temperature sensor is arranged on a fuel filter or the fuel filter, the upstream fuel pressure sensor is arranged on a pipeline for connecting the fuel filter and the metering valve, the downstream fuel pressure sensor is arranged on a pipeline for connecting the metering valve and the nozzle, and the pressure regulating valve is arranged on a pipeline for connecting the fuel filter and the metering valve;
the signal acquisition module is used for acquiring a fuel temperature signal, an upstream fuel pressure signal and a downstream fuel pressure signal, the acquired fuel temperature signal is used for correcting the fuel injection quantity and improving the fuel injection quantity control precision, and the acquired fuel pressure signal is used for controlling the fuel injection quantity and diagnosing system faults;
the working mode dividing module comprises a maintenance mode, a pressure building mode, an injection mode and a self-cleaning mode, and compressed air purging is periodically performed on an injection pipeline and a nozzle in the maintenance mode to prevent the blockage of an exhaust pipe side fuel pipeline and the nozzle; establishing a stable injection pressure required when the DPF is actively regenerated in a pressure establishing mode; outputting the oil injection amount required by DPF regeneration in an injection mode, ensuring that the actual oil injection amount and the required oil amount are within an error allowable range, and ensuring the execution precision of oil injection; the self-cleaning mode is used for performing a self-cleaning function on the fuel pipeline and the nozzle after the injection mode is finished, so that the problem of blockage of the fuel pipeline and the nozzle on the exhaust side due to fission of residual fuel is solved;
the mode scheduling management module is used for managing switching control logic, required oil quantity calculation and required oil quantity conversion control signals among four modes in the working mode dividing module, and realizing a fuel injection control function and a fuel pipeline self-cleaning function;
the instruction driving module is used for realizing a control instruction output function of the actuator module;
the actuator module is used for executing a corresponding control command to complete corresponding fuel injection and pipeline self-cleaning operation;
the DPF regeneration judging module is used for sending a DPF regeneration starting signal, a DPF regeneration interrupting signal and a DPF regeneration ending signal.
A fuel injection control method for active regeneration of a DPF, comprising the steps of:
the method comprises the following steps that firstly, a mode scheduling management module detects whether a DPF regeneration judging module meets DPF active regeneration triggering conditions or not and sends a DPF regeneration starting signal or not, if the DPF regeneration judging module does not meet the DPF active regeneration triggering conditions or sends no DPF regeneration starting signal, a maintenance mode is entered, at the moment, an instruction driving module sends an instruction to enable a pressure regulating valve and a metering valve to be in a closed state, and a cleaning valve is opened and closed periodically;
step two, when the mode scheduling management module detects that the DPF regeneration judgment module meets the active regeneration triggering condition of the DPF and sends a DPF regeneration opening signal, the pressure building mode is entered, at the moment, the instruction driving module sends an instruction to enable the cleaning valve to be in a closed state, the instruction driving module controls the pressure regulating valve to be in an open state, after the calibration time, the instruction driving module controls the metering valve to be opened, after the calibration time is continued, the instruction driving module controls the metering valve to be closed, so that fuel oil is filled in a fuel oil pipeline between the pressure regulating valve and a nozzle, at the moment, the pressure measured by the upstream fuel oil pressure sensor is a stable fuel oil supply pressure value, so that stable injection pressure required by DPF active regeneration is built, and the purpose of pressure building is achieved;
step three, when the mode scheduling management module detects that the pressure building is finished, the injection mode is entered, and the mode scheduling management module determines a demand control signal of a metering valve according to a fuel supply pressure value, the injection oil quantity required by DPF regeneration and the fuel temperature to finish the control of the injection oil quantity;
step four, when the mode scheduling management module detects that the injection mode is about to end, closing the pressure regulating valve, and closing the metering valve after corresponding delay time;
and step five, after the mode scheduling management module detects that the DPF regeneration judgment module sends a DPF regeneration interruption signal or a DPF regeneration ending signal, the self-cleaning mode is started, the pressure regulating valve and the metering valve are closed at the moment, the driving module is instructed to control the cleaning valve to be opened and control the cleaning valve to be in an open state for a proper time, and compressed air blows fuel oil remained at a fuel oil pipeline and a nozzle into an exhaust pipe through the cleaning valve to complete the self-cleaning function.
And in the third step, two measures of fuel temperature correction and metering valve grading control are adopted to improve the control precision of the injection oil quantity, the control precision of the metering valve on the injection required oil quantity is optimized, and the injection required oil quantity of the DPF regeneration after the fuel temperature correction is Q.
The fuel temperature correction measure refers to the influence of the fuel temperature on the injection required oil quantity, and the injection required oil quantity Q of the DPF regeneration after the fuel temperature correction is as follows:
Q＝α·Qreq
wherein alpha is a fuel temperature correction coefficient, is a linear function of the fuel temperature, is determined by the fuel characteristics and is obtained through a bench calibration test; qreqThe amount of fuel injected that is actually required for active regeneration of the DPF.
The actually required injection oil quantity QreqThe following equation (1) is used:
Figure BDA0002165192520000041
wherein delta is an oil mass calculation coefficient, and can be determined by inquiring a calibrated oil mass calculation coefficient table according to the DOC inlet actual temperature and the exhaust mass flow;
Figure BDA0002165192520000042
the unit of the theoretical required oil injection quantity is kg/h;
theoretical required fuel injection quantity
Figure BDA0002165192520000043
The following equation (2) is used to obtain:
Figure BDA0002165192520000044
wherein c ispConstant pressure heat capacity is taken as exhaust ratio, constant is 1.004, and unit is kJ/(kg. K); qmThe unit is kg/h, and the exhaust mass flow is shown as the exhaust mass flow; Δ T is an exhaust temperature rise value, which is the difference between the DPF inlet regeneration set target temperature and the DPF inlet actual temperature, in units of K; the regeneration setting target temperature of the DPF inlet is an artificially set temperature, and the actual temperature of the DPF inlet is acquired according to a sensor installed in the post-processing system; hfuelThe calorific value of the fuel oil is constant 4260, unit kJ/kg.
The metering valve grading control measure comprises the following steps:
firstly, the control stage of the metering valve is divided into two stages, one stage is a working period control stage, the other stage is a duty ratio control stage, and the demarcation threshold value of the two stages is QLim，QLimA look-up table function of the fuel pressure difference Δ p, which is the difference between the upstream fuel pressure and the pressure at the DOC inlet, QLimObtained by test calibration;
secondly, when the injection required oil quantity Q is smaller than the boundary threshold value QLimAnd then, entering a working period control stage: the duty ratio is fixed, the working period is adjusted, and the control on the oil injection quantity is realized; when the required oil quantity Q is more than or equal to the demarcation threshold value QLimAnd then, entering a duty ratio control stage: the duty ratio is adjusted by fixing the working period, and the control of the oil injection amount is realized.
Compared with the prior art, the invention has the beneficial effects that:
the invention realizes the active regeneration function of the DPF, and can not generate the problem of engine oil dilution; meanwhile, the nozzle and the fuel pipeline on the side of the exhaust pipe can be automatically cleaned, and the problem that the nozzle and the nearby pipelines are blocked due to high-temperature cracking of fuel remained in the pipelines is avoided.
Drawings
Fig. 1 is a block diagram of a fuel injection control system according to the present invention.
FIG. 2 is a flow chart of the method of the present invention.
Fig. 3 is a schematic view of the fuel injection system of the present invention.
In the figure, a fuel temperature sensor 1, an upstream fuel pressure sensor 2, a downstream fuel pressure sensor 3, a pressure regulating valve 4, a metering valve 5, a cleaning valve 6, a fuel tank 7, an air compressor 8, an air storage tank 9, a one-way valve 10, an exhaust pipe 11, a nozzle 12, a fuel filter 13 and a low-pressure oil pump 14 are arranged.
Detailed Description
The invention is described in further detail below with reference to the following description of the drawings and the detailed description.
Detailed description of the preferred embodiment
Referring to fig. 1, a fuel injection control system for DPF active regeneration includes a sensor module, a signal acquisition module, a working mode division module, a mode scheduling management module, an instruction driving module, an actuator module, and a DPF regeneration determination module, where the sensor module is connected to the signal acquisition module, the signal acquisition module is connected to the mode scheduling management module, the mode scheduling management module is connected to the instruction driving module, the instruction driving module is connected to the actuator module, the working mode division module is connected to the mode scheduling management module, and the DPF regeneration determination module is connected to the mode scheduling management module.
Referring to fig. 1, the sensor module comprises a fuel temperature sensor 1, an upstream fuel pressure sensor 2 and a downstream fuel pressure sensor 3, and the actuator module comprises three actuators of a pressure regulating valve 4, a metering valve 5 and a purge valve 6.
Referring to fig. 3, the fuel injection control system is used in a fuel injection system, the fuel injection system comprises a fuel tank 7, a low-pressure oil pump 14, a nozzle 12, an air compressor 8 and a gas storage tank 9, the fuel tank 7 is connected with the nozzle 12 through the low-pressure oil pump 14, a fuel filter 13 is connected to a pipeline connecting the low-pressure oil pump 14 and the nozzle 12, the air compressor 8 is connected with the gas storage tank 9, and the gas storage tank 9 is connected with the nozzle 12. Metering valve 5 set up on the pipeline that low pressure oil pump 14 and nozzle 12 are connected, clean valve 6 set up on the pipeline that gas holder 9 and nozzle 12 are connected, fuel temperature sensor 1 install on oil tank 7 or fuel filter 13, upstream fuel pressure sensor 2 installs on the pipeline that fuel filter 13 and metering valve 5 are connected, downstream fuel pressure sensor 3 install on the pipeline that metering valve 5 and nozzle 12 are connected, air-vent valve 4 sets up on the pipeline that fuel filter 13 and metering valve 5 are connected.
Referring to fig. 1, the signal acquisition module is used for acquiring a fuel temperature signal, an upstream fuel pressure signal and a downstream fuel pressure signal, the acquired fuel temperature signal is used for correcting a fuel injection amount and improving fuel injection amount control accuracy, and the acquired fuel pressure signal is used for controlling the fuel injection amount and diagnosing system faults.
Referring to fig. 1, the working mode division module includes four modes, i.e., a maintenance mode, a pressure build-up mode, an injection mode and a self-cleaning mode, in which compressed air purging is periodically performed on the injection pipeline and the nozzle 12 in the maintenance mode to prevent the fuel pipeline at the exhaust pipe 11 side and the nozzle 12 from being blocked; establishing a stable injection pressure required when the DPF is actively regenerated in a pressure establishing mode; outputting the oil injection amount required by DPF regeneration in an injection mode, ensuring that the actual oil injection amount and the required oil amount are within an error allowable range, and ensuring the execution precision of oil injection; the self-cleaning mode is used for performing a self-cleaning function on the fuel pipeline and the nozzle 12 after the injection mode is finished, and the problem of blockage of the fuel pipeline and the nozzle 12 on the exhaust side 11 due to fission of residual fuel is solved.
Referring to fig. 1, the mode scheduling management module is configured to manage switching control logic, required oil amount calculation, and a required oil amount conversion control signal among four modes in the working mode division module, so as to implement a fuel injection control function and a fuel pipeline self-cleaning function.
Referring to fig. 1, the command driver module is configured to implement a control command output function for the actuator module.
Referring to fig. 1, the actuator module is configured to execute a corresponding control command to perform a corresponding fuel injection and a corresponding pipeline self-cleaning operation.
Referring to fig. 1, the DPF regeneration determination module is configured to send a DPF regeneration start signal, a DPF regeneration stop signal, and a DPF regeneration end signal.
Detailed description of the invention
Referring to fig. 1 to 3, a fuel injection control method for DPF active regeneration, which is controlled based on the above control system, includes the following steps:
the first step is that the mode scheduling management module detects whether the DPF regeneration determination module meets the DPF active regeneration triggering condition and sends a DPF regeneration start signal, and if the DPF regeneration determination module does not meet the DPF active regeneration triggering condition and sends no DPF regeneration start signal, the mode enters a maintenance mode, at this time, the instruction driving module sends an instruction to enable the pressure regulating valve 4 and the metering valve 5 to be in a closed state, the cleaning valve 6 is periodically opened and closed, the opening duration of the cleaning valve 6 is t1, the closing duration is t2, t1 and t2 can be manually set according to actual needs, for example, t1 is 15s, and t2 is 200 s. In this mode, the injection line and the nozzle 12 are periodically purged with compressed air, and clogging of the fuel line and the nozzle 12 on the exhaust pipe 11 side is prevented.
And step two, when the mode scheduling management module detects that the DPF regeneration judgment module meets the active regeneration triggering condition of the DPF and sends a DPF regeneration opening signal, the pressure building mode is entered, at the moment, the instruction driving module sends an instruction to enable the cleaning valve 6 to be in a closed state, the instruction driving module controls the pressure regulating valve 4 to be in an opening state, and fuel oil passes through the low-pressure oil pump 14 and the fuel oil filter 13 from the oil tank 7 and flows through the pressure regulating valve 4 to enter an injection pipeline. After the calibration time t3, the command driving module controls the metering valve 5 to open; the calibration time t3 is a time period, for example, 0.5s, which is determined by a calibration test from the time when the regulator valve 4 is opened until the upstream fuel pressure sensor 2 reaches a set threshold (for example, 7 atmospheres), and is related to the length of the line. After the calibration time t4 lasts, the instruction driving module controls the metering valve 5 to close, so that the fuel oil fills the fuel oil pipeline between the pressure regulating valve 4 and the nozzle 12, and the pressure measured by the upstream fuel oil pressure sensor 2 is a stable fuel oil supply pressure value, so that the stable injection pressure required by the DPF active regeneration is established, and the purpose of pressure establishment is achieved; the calibration time t4 is a time period, for example, 0.5s, which is determined by a calibration test from the time when the metering valve 5 is opened until the downstream fuel pressure sensor 3 reaches a set threshold (for example, 4 atm), and is related to the length of the line.
And step three, when the mode scheduling management module detects that the pressure build-up is finished, the injection mode is entered, and the mode scheduling management module determines a demand control signal of the metering valve 5 according to the fuel supply pressure value, the injection oil quantity required by DPF regeneration and the fuel temperature to finish the control of the injection oil quantity. The injection required oil quantity can be converted into a required control signal by searching a MAP calibrated in advance, the calibrated MAP is input into the fuel supply pressure and the injection required oil quantity, and is output into the required control signal; in the actual calibration process, the fuel supply pressure is kept unchanged, and different control signals are changed to obtain different fuel injection demands.
Step four, when the mode scheduling management module detects that the injection mode is about to end, closing the pressure regulating valve 4, and closing the metering valve 5 after a delay time t 5; therefore, the pressure of the fuel supply pipeline is reduced to the maximum extent, and the burden of a cleaning mode is shortened. The delay time t5 is set artificially, and may be set to any time between 0 and 1 s.
And step five, after the mode scheduling management module detects that the DPF regeneration judging module sends a DPF regeneration interrupt signal or a DPF regeneration end signal, the self-cleaning mode is started, the pressure regulating valve 4 and the metering valve 5 are closed at the moment, the driving module is instructed to control the cleaning valve 6 to be opened, the cleaning valve 6 is controlled to be in an open state and is kept for t6 duration, the compressed air is enabled to blow residual fuel at the fuel pipeline and the nozzle 12 into the exhaust pipe 11 through the cleaning valve 6, the self-cleaning function is completed, and the problem of blockage of the fuel pipeline and the nozzle 12 on the exhaust side 11 due to fission of the residual fuel is solved. The state holding t6 can be set manually, for example, 10 s.
Referring to fig. 3, further, in the third step, two measures, namely fuel temperature correction and metering valve 5 stepped control, are adopted to improve the control accuracy of the injected fuel quantity, and the control accuracy of the metering valve 5 on the fuel quantity required for injection is optimized; the injection required oil amount for DPF regeneration after fuel temperature correction is Q.
Specifically, the fuel temperature correction measure refers to the influence of the fuel temperature on the injection required oil quantity, and the injection required oil quantity Q of the DPF regeneration after the fuel temperature correction is as follows:
Q＝α·Qreq
wherein alpha is a fuel temperature correction coefficient, is a linear function of the fuel temperature, is determined by the fuel characteristics and is obtained through a bench calibration test; qreqThe amount of fuel injected that is actually required for active regeneration of the DPF.
Further, the actually required injection oil quantity QreqThe following equation (1) is used:
Figure BDA0002165192520000071
wherein delta is an oil mass calculation coefficient, and can be determined by inquiring a calibrated oil mass calculation coefficient table according to the DOC inlet actual temperature and the exhaust mass flow;
Figure BDA0002165192520000072
the unit of the theoretical required oil injection quantity is kg/h.
And the theoretical required fuel injection quantity
Figure BDA0002165192520000073
The following equation (2) is used to obtain:
Figure BDA0002165192520000074
wherein c ispConstant pressure heat capacity is taken as exhaust ratio, constant is 1.004, and unit is kJ/(kg. K); qmThe unit is kg/h for exhaust gas mass flow. Δ T is an exhaust temperature rise value, which is the difference between the DPF inlet regeneration set target temperature and the DPF inlet actual temperature, in units of K; the regeneration set target temperature of the DPF inlet is an artificially set temperature, and the actual temperature of the DPF inlet is acquired according to a sensor installed on the aftertreatment system. HfuelIs the low heat value of the fuel oil, and is constant 4260 with kJ/kg.
Specifically, the metering valve 5 graded control measures comprise:
firstly, the control stage of the metering valve 5 is divided into two stages, one stage is a work period control stage, the other stage is a duty ratio control stage, and the demarcation threshold value of the two stages is QLim。QLimA look-up table function of the fuel pressure difference Δ p, which is the difference between the upstream fuel pressure and the pressure at the DOC inlet, QLimObtained by test calibration; in practical application, QLimObtained by the calibration of an engine bench test. The working period is the time of a single pulse of the metering valve 5, and the duty ratio is the proportion of the electrifying time of the metering valve 5 relative to the working period.
Secondly, when the injection required oil quantity Q is smaller than the boundary threshold value QLimAnd then, entering a working period control stage: fixing duty ratio and adjusting work period; the duty ratio is kept constant, the working period is adjusted, the metering valve 5 is controlled, the control of the oil injection amount is achieved, and the oil injection precision is improved. When the required oil quantity Q is more than or equal to the demarcation threshold value QLimAnd then, entering a duty ratio control stage: fixing the working period and adjusting the duty ratio; the duty ratio is adjusted to control the metering valve 5 to realize the control of the injection oil quantity and improve the injection precision.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention relates, several simple deductions or substitutions may be made without departing from the spirit of the invention, and the above-mentioned structures should be considered as belonging to the protection scope of the invention.

Claims (3)

1. A fuel injection control method for DPF active regeneration is realized by a fuel injection control system for DPF active regeneration, the fuel injection control system is used in the fuel injection system, the fuel injection system comprises a fuel tank (7), a low-pressure oil pump (14), a nozzle (12), an air compressor (8) and a gas storage tank (9), the fuel tank (7) is connected with the nozzle (12) through the low-pressure oil pump (14), a fuel filter (13) is connected on a pipeline connecting the low-pressure oil pump (14) and the nozzle (12), the air compressor (8) is connected with the gas storage tank (9), the gas storage tank (9) is connected with the nozzle (12), the fuel injection control system comprises a sensor module, a signal acquisition module, a working mode division module, a mode scheduling management module, an instruction driving module, an actuator module and a DPF regeneration judgment module, the sensor module is connected with the signal acquisition module, the signal acquisition module is connected with the mode scheduling management module, the mode scheduling management module is connected with the instruction driving module, the instruction driving module is connected with the actuator module, the working mode dividing module is connected with the mode scheduling management module, and the DPF regeneration judgment module is connected with the mode scheduling management module;
the sensor module comprises a fuel temperature sensor (1), an upstream fuel pressure sensor (2) and a downstream fuel pressure sensor (3), the actuator module comprises three actuators of a pressure regulating valve (4), a metering valve (5) and a cleaning valve (6), the metering valve (5) is arranged on a pipeline which is connected with the low-pressure oil pump (14) and the nozzle (12), the cleaning valve (6) is arranged on a pipeline connected with the air storage tank (9) and the nozzle (12), the fuel temperature sensor (1) is arranged on the fuel tank (7) or the fuel filter (13), the upstream fuel pressure sensor (2) is arranged on a pipeline connected with the fuel filter (13) and the metering valve (5), the downstream fuel pressure sensor (3) is arranged on a pipeline connected with the metering valve (5) and the nozzle (12), the pressure regulating valve (4) is arranged on a pipeline connected with the fuel filter (13) and the metering valve (5);
the signal acquisition module is used for acquiring a fuel temperature signal, an upstream fuel pressure signal and a downstream fuel pressure signal, the acquired fuel temperature signal is used for correcting the fuel injection quantity and improving the fuel injection quantity control precision, and the acquired fuel pressure signal is used for controlling the fuel injection quantity and diagnosing system faults;
the working mode dividing module comprises a maintenance mode, a pressure building mode, an injection mode and a self-cleaning mode, and compressed air purging is periodically performed on an injection pipeline and a nozzle (12) in the maintenance mode to prevent the blockage of an oil pipeline and the nozzle (12) on the side of the exhaust pipe (11); establishing a stable injection pressure required when the DPF is actively regenerated in a pressure establishing mode; outputting the oil injection amount required by DPF regeneration in an injection mode, ensuring that the actual oil injection amount and the required oil amount are within an error allowable range, and ensuring the execution precision of oil injection; the self-cleaning mode is used for performing a self-cleaning function on the fuel pipeline and the nozzle (12) after the injection mode is finished, so that the problem of blockage of the fuel pipeline and the nozzle (12) on the side of the exhaust pipe (11) due to fission of residual fuel is solved;
the mode scheduling management module is used for managing switching control logic, required oil quantity calculation and required oil quantity conversion control signals among four modes in the working mode dividing module, and realizing a fuel injection control function and a fuel pipeline self-cleaning function;
the instruction driving module is used for realizing a control instruction output function of the actuator module;
the actuator module is used for executing a corresponding control command to complete corresponding fuel injection and pipeline self-cleaning operation;
the DPF regeneration judging module is used for sending a DPF regeneration starting signal, a DPF regeneration interrupting signal and a DPF regeneration ending signal;
characterized in that the fuel injection control method comprises the following steps:
the method comprises the following steps that firstly, a mode scheduling management module detects whether a DPF regeneration judging module meets DPF active regeneration triggering conditions or not and sends a DPF regeneration starting signal or not, if the DPF regeneration judging module does not meet the DPF active regeneration triggering conditions or does not send the DPF regeneration starting signal, a maintenance mode is entered, at the moment, an instruction driving module sends an instruction to enable a pressure regulating valve (4) and a metering valve (5) to be in a closed state, and a cleaning valve (6) is opened and closed periodically;
step two, when the mode scheduling management module detects that the DPF regeneration judgment module meets the active regeneration triggering condition of the DPF and sends a DPF regeneration opening signal, the pressure building mode is entered, at the moment, the instruction driving module sends an instruction to enable the cleaning valve (6) to be in a closed state, the instruction driving module controls the pressure regulating valve (4) to be in an open state, after the calibration time, the instruction driving module controls the metering valve (5) to be opened, after the calibration time continues, the instruction driving module controls the metering valve (5) to be closed, so that fuel oil is filled in a fuel oil pipeline between the pressure regulating valve (4) and the nozzle (12), at the moment, the pressure measured by the upstream fuel oil pressure sensor (2) is a stable fuel oil supply pressure value, the stable injection pressure required by the DPF active regeneration is built, and the purpose of pressure building is achieved;
step three, when the mode scheduling management module detects that the pressure build-up is finished, the injection mode is entered, and the mode scheduling management module determines a demand control signal of a metering valve (5) according to a fuel supply pressure value, the injection oil quantity required by DPF regeneration and the fuel temperature to finish the control of the injection oil quantity; in the step, two measures of fuel temperature correction and metering valve (5) grading control are adopted to improve the control precision of the injection oil quantity, the control precision of the metering valve (5) on the injection required oil quantity is optimized, and the injection required oil quantity of DPF regeneration after the fuel temperature correction is Q; the metering valve (5) stage control measure comprises the following steps: firstly, the control phase of the metering valve (5) is divided into two stages, one stage is a work period control phase, the other stage is a duty ratio control phase, and the demarcation threshold value of the two stages is QLim，QLimA look-up table function of the fuel pressure difference Δ p, which is the difference between the upstream fuel pressure and the pressure at the DOC inlet, QLimObtained by test calibration; secondly, when the injection required oil quantity Q is smaller than the boundary threshold value QLimAnd then, entering a working period control stage: the duty ratio is fixed, the working period is adjusted, and the control on the oil injection quantity is realized; when the required oil quantity Q is more than or equal to the demarcation threshold value QLimAnd then, entering a duty ratio control stage: fixing the working period, adjusting the duty ratio and realizing the control of the injected oil quantity;
step four, when the mode scheduling management module detects that the injection mode is about to end, the pressure regulating valve (4) is closed, and after the corresponding delay time, the metering valve (5) is closed again;
and step five, after the mode scheduling management module detects that the DPF regeneration judging module sends a DPF regeneration interruption signal or a DPF regeneration ending signal, the self-cleaning mode is started, the pressure regulating valve (4) and the metering valve (5) are closed at the moment, the driving module is instructed to control the cleaning valve (6) to be opened and control the cleaning valve (6) to be in an opening state for keeping a proper time, and compressed air blows fuel oil remained at the fuel oil pipeline and the nozzle (12) into the exhaust pipe (11) through the cleaning valve (6), so that the self-cleaning function is completed.
2. A fuel injection control method for DPF active regeneration according to claim 1, characterized in that: the fuel temperature correction measure refers to the influence of the fuel temperature on the injection required oil quantity, and the injection required oil quantity Q of the DPF regeneration after the fuel temperature correction is as follows:
Q＝α·Qreq
wherein alpha is a fuel temperature correction coefficient, is a linear function of the fuel temperature, is determined by the fuel characteristics and is obtained through a bench calibration test; qreqThe amount of fuel injected that is actually required for active regeneration of the DPF.
3. A fuel injection control method for DPF active regeneration according to claim 2, characterized in that: the actually required injection oil quantity QreqThe following equation (1) is used:
Figure FDA0003216734490000031
wherein delta is an oil mass calculation coefficient, and can be determined by inquiring a calibrated oil mass calculation coefficient table according to the DOC inlet actual temperature and the exhaust mass flow;
Figure FDA0003216734490000032
the unit of the theoretical required oil injection quantity is kg/h;
theoretical required fuel injection quantity
Figure FDA0003216734490000033
The following equation (2) is used to obtain:
Figure FDA0003216734490000034
wherein c ispConstant pressure heat capacity is taken as exhaust ratio, constant is 1.004, and unit is kJ/(kg. K); qmThe unit is kg/h, and the exhaust mass flow is shown as the exhaust mass flow; Δ T is an exhaust temperature rise value, which is the difference between the DPF inlet regeneration set target temperature and the DPF inlet actual temperature, in units of K; the regeneration setting target temperature of the DPF inlet is an artificially set temperature, and the actual temperature of the DPF inlet is acquired according to a sensor installed in the post-processing system; hfuelThe calorific value of the fuel oil is constant 4260, unit kJ/kg.
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