CN111305968B - Fuel injection method and device for multi-fuel charge compression combustion engine - Google Patents
Fuel injection method and device for multi-fuel charge compression combustion engine Download PDFInfo
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- CN111305968B CN111305968B CN202010169477.8A CN202010169477A CN111305968B CN 111305968 B CN111305968 B CN 111305968B CN 202010169477 A CN202010169477 A CN 202010169477A CN 111305968 B CN111305968 B CN 111305968B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
- F02D41/3011—Controlling fuel injection according to or using specific or several modes of combustion
- F02D41/3017—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
- F02D41/3094—Controlling fuel injection the fuel injection being effected by at least two different injectors, e.g. one in the intake manifold and one in the cylinder
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/3809—Common rail control systems
- F02D41/3836—Controlling the fuel pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
- F02D41/38—Controlling fuel injection of the high pressure type
- F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/30—Controlling fuel injection
- F02D41/3011—Controlling fuel injection according to or using specific or several modes of combustion
- F02D41/3017—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used
- F02D2041/3052—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used the mode being the stratified charge compression-ignition mode
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- 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
Abstract
The invention discloses a fuel injection method and a device of a multi-fuel charge compression combustion engine, which relate to the technical field of internal combustion engines and comprise the following steps: sensing an operating condition of the engine; adjusting an injection strategy for directly injecting fuel into a combustion chamber of the engine during a cylinder cycle of the engine based on the operating condition of the engine; controlling an intake air temperature of an intake passage, the intake passage communicating with the combustion chamber to admit air into the combustion chamber; adjusting an injection strategy for injecting fuel into the intake port; the injection strategy comprises the injection times, the fuel injection quantity and the injection time range. The implementation of the invention can flexibly realize the concentration and activity stratification of the mixed gas in the cylinder, thereby forming the optimal fuel activity gradient, ensuring that the engine keeps the optimal thermal efficiency and the lowest emission under each working condition, and having very outstanding application value in the field of mechanical engineering, in particular in the field of automobile engines.
Description
Technical Field
The invention belongs to the technical field of internal combustion engines, and particularly relates to a fuel injection method and a fuel injection device for a multi-fuel charge compression combustion engine.
Background
The traditional diesel engine adopts a cylinder with high compression ratio, when a piston moves to the vicinity of the top dead center, fuel with high cetane number is directly injected into the cylinder, and high-temperature mixed gas is formed by utilizing the high compression ratio when the piston of the engine is compressed to the position close to the top dead center, so that the working mode of fuel spontaneous combustion and ignition is initiated, and the high-compression-ratio cylinder has the advantages of high thermal efficiency, stable work and low emission of carbon monoxide and hydrocarbon; however, the average in-cylinder mixed gas concentration is relatively thin, the mixing time of the spray and the air is short, and the fuel and the air cannot be uniformly mixed, so that a local high-temperature area and a local rich combustion area always exist in the cylinder in the combustion process, the emission of nitrogen oxides and soot is relatively high, and the emission of the nitrogen oxides and the soot cannot be simultaneously and greatly reduced. For direct injection diesel engines, a common method for reducing soot emissions is to use a particulate trap, but the particulate trap generally suffers from problems of too short system life and regeneration; the common method for reducing the emission of nitrogen oxides adopts selective catalytic reduction and other means, but the above means easily cause the problems of ammonia gas leakage and the like; therefore, the exhaust gas after-treatment device of the direct injection diesel engine has a complex structure, high cost, undesirable effect and poor reliability.
The traditional gasoline engine adopts a cylinder with low compression ratio, injects high-octane fuel through an air passage port and adopts a working mode of ignition and combustion of a spark plug, and because of the propagation process of flame, a flame front generates more nitrogen oxides.
Some gasoline engines adopt a direct injection scheme, but the scheme still has the defect of low thermal efficiency.
In order to improve the high emission problem of a diesel engine and the low thermal efficiency problem of a gasoline engine, a Homogeneous Charge Compression Ignition (HCCI) combustion mode gradually appears, wherein a Homogeneous Charge Compression Ignition combustion mode adopts a Homogeneous mixed gas and is matched with a higher Compression ratio to realize the Compression Ignition of the mixed gas. However, the ignition process of the homogeneous charge compression ignition combustion mode completely depends on the chemical reaction kinetics, and the ignition time and the heat release rate are affected by the temperature, the pressure, the physical and chemical properties of the mixed gas, and the like, so the homogeneous charge compression ignition combustion mode has the technical problem that the combustion phase and the combustion rate are difficult to control, the homogeneous charge compression ignition combustion mode is easy to ignite and unstable in small load, and the homogeneous charge compression ignition combustion mode is easy to knock in large load.
A gasoline/diesel dual fuel engine that uses port injection of a low activity fuel to form a homogeneous charge and then ignites with direct injection of a high activity fuel near top dead center has emerged after the homogeneous charge compression ignition combustion mode. Macroscopically, the gasoline/diesel dual fuel engine is a combustion mode with two fuels simultaneously intensively releasing heat, and has lower nitrogen oxide and soot emission. On one hand, because a mode of injecting low-activity fuel through an air passage opening is adopted, the pumping loss of the engine is high, the charge coefficient is reduced, the knocking tendency is increased, the emission of hydrocarbon and carbon monoxide is high, and further the thermal efficiency is lower than that of a conventional direct injection diesel engine; the excess air coefficient of the whole engine is more than 1, soot emission still exists, nitrogen oxide still exists, and the emission of hydrocarbon, carbon monoxide and nitrogen oxide can not be completely converted by adopting a three-way catalytic converter; on the other hand, because the adjustment range of the fuel injection time is limited, the fuel injection time and the fuel injection quantity cannot be regulated at any time in the whole cycle process, and further flexible and reliable concentration and activity stratification cannot be formed in a cylinder according to different working conditions of the engine, so that the requirements of maximum thermal efficiency and minimum emission state cannot be met under different working conditions.
Disclosure of Invention
In view of the above, the present invention is directed to a fuel injection method that can form flexible and reliable fuel concentration and activity stratification in a cylinder to meet the requirements of maximum thermal efficiency and minimum emission state under different engine operating conditions.
The present inventors have made extensive studies and found that in order to achieve a high thermal efficiency at a low level of engine emissions and to satisfy a wide applicable and generalizable workload range, it is necessary to optimize combustion in the engine combustion chamber. According to different working conditions of an engine, concentration and activity layering required by the in-cylinder mixed gas in corresponding working conditions are flexibly realized, so that the optimal activity gradient of fuel in different working conditions is formed, and then a combustion mode of Charge Compression Ignition is carried out, the requirements of maximum thermal efficiency and minimum emission under different working conditions can be met, wherein the combustion mode is called an Intelligent Charge Compression Ignition (ICCI) combustion mode; it would be further advantageous if in-cylinder mixture concentration and activity stratification could be achieved within one engine cycle. The optimal activity gradient refers to the stratified state of the in-cylinder fuel that can bring the engine to the optimal operating state, which means that the thermal efficiency and emissions of the engine are optimal.
To achieve the above object, the present invention discloses a fuel injection method of a multi-fuel charge compression combustion engine, comprising the steps of:
sensing an operating condition of the engine;
adjusting an injection strategy for directly injecting fuel into a combustion chamber of the engine during a cylinder cycle of the engine based on the operating condition of the engine;
controlling an intake air temperature of an intake air passage, wherein the intake air passage communicates with the combustion chamber to intake air to the combustion chamber; and adjusting an injection strategy for injecting fuel into the intake port;
wherein the injection strategy comprises the injection times, the fuel injection quantity and the injection time range.
In one aspect of the present invention, a first fuel and a second fuel are directly injected into the combustion chamber; and injecting a third fuel into the intake port.
In one aspect of the present invention, the first fuel, the second fuel, and the third fuel are injected independently of each other.
The first fuel and the second fuel are injected independently, so that the injection combination of fuels with different characteristics and concentrations can be realized, the injection combination of mixed fuels of the same type with different concentrations can also be realized, the third fuel is injected in an air inlet passage in an auxiliary mode through the injection system, and further the in-cylinder mixed gas is promoted to form any concentration and activity stratification, so that the in-cylinder mixed gas with the optimal fuel activity gradient is formed.
In the invention, the working conditions of the engine are divided, the injection system can be regulated and controlled at any time in the whole engine cycle process in the cycle period of the cylinder, and different injection strategies are adopted, thereby being beneficial to realizing the optimal distribution of fuel in the combustion chamber. The working condition of the engine can be divided into idling, starting, small load, medium load, large load or full load, and the idling working condition refers to the no-load running state of the engine; the starting working condition refers to the working condition that the output torque of the engine is within 10% of the rated torque; the low-load working condition refers to the working condition that the output torque of the engine is within 10-25% of the rated torque; the medium-load working condition refers to the working condition that the output torque of the engine is within 25% -85% of the rated torque; the high load or full load operation state refers to an operation state in which the output torque of the engine is 85% or more of the rated torque.
In order to achieve an optimal distribution of the fuel in the combustion chamber, the injection system is configured to regulate the injection of the fuel at any time during the cycle of the cylinder during the whole engine cycle, and to adopt different injection strategies for the injection of various fuels and control the temperature of the intake air entering from the intake passage according to different working conditions of the engine.
In one aspect of the present invention, when the engine is operating in an idle, start, or low load operating condition, the number of injections of the first fuel is a single, and the number of injections of the second fuel is a single, during each cycle of the cylinder.
Further, when the operating condition of the engine is idling or starting, the injection timing of the first fuel ranges from-350 ℃ A ATDC to-280 ℃ A ATDC, and the injection timing of the second fuel ranges from-50 ℃ A ATDC to-30 ℃ A ATDC; in the present invention, TDC represents the top dead center of the crankshaft, ATDC represents the crank angle after the top dead center, and ° c a represents the crank angle unit.
Further, when the engine is operated in an idling or start-up operating condition, the intake air temperature ranges from 40 ℃ to 60 ℃, or the proportion of the injection amount of the first fuel to the total fuel injection amount in the operating condition of idling or start-up ranges from 30% to 50%.
When the engine works in an idling or starting working condition, the engine is difficult to compress and catch fire and is easy to catch fire, and fuel in the engine combustion chamber can be heated by adopting an air inlet heating mode, so that the engine is beneficial to reducing the fire of the engine. The applicant has conducted experiments to obtain that it is advantageous to improve the reliability of ignition and the thermal efficiency of the engine when the intake air temperature is in the range of 40 to 60 c.
Further, when the engine is operating at a low load operating condition, the injection timing of the first fuel ranges from-350 ℃ A ATDC to-280 ℃ A ATDC, and the injection timing of the second fuel ranges from-70 ℃ A ATDC to-50 ℃ A ATDC.
Further, when the operating condition of the engine is a small load, the injection amount of the first fuel is in a range of 60% to 80% in percentage of the total fuel injection amount when the operating condition is a small load.
In one aspect of the present invention, when the operating condition of the engine is a medium load, the number of injections of the first fuel is single or two during each cycle of the cylinder.
Further, when the operating condition of the engine is medium load, the number of injections of the second fuel is single or double during each cycle of the cylinder.
Further, the injection amount of the first fuel is in a range of 70% to 90% in percentage of the total fuel injection amount at the medium load as the operation condition.
In one aspect of the present invention, when the operating condition of the engine is a large load or a full load, the number of injections of the first fuel is a single injection, and the number of injections of the second fuel is two in each cycle of the cylinder.
Further, the injection timing of the first fuel ranges from-350 ℃ A ATDC to-280 ℃ A ATDC; the injection time range of the first injection of the second fuel is-60 ℃ A ATDC to-40 ℃ A ATDC, and the injection time range of the second injection of the second fuel is-10 ℃ A ATDC to-1 ℃ A ATDC.
Further, the injection amount of the first fuel is in a range of 40% to 60% in percentage of the total fuel injection amount when the operating condition is a large load or a full load.
Further, the injection quantity of the second fuel for the first injection is in the range of 20% to 30% in percentage of the total fuel injection quantity when the operating condition is a large load or a full load, and the injection quantity of the second fuel for the second injection is in the range of 20% to 30% in percentage of the total fuel injection quantity when the operating condition is a large load or a full load.
According to the research, through the technical scheme, different concentrations and activity stratification of the mixed gas in the cylinder can be flexibly realized under different working conditions, so that the fuel stratification with the optimal fuel activity gradient is formed, and the engine can keep the optimal thermal efficiency and the lowest emission under each working condition.
In one technical scheme of the invention, the first fuel comprises a low-boiling-point and high-octane fuel; the second fuel comprises a high boiling point, high cetane fuel; the third fuel comprises a secondary fuel and/or an additive.
The low-boiling-point and high-octane fuel is fuel which can be combusted only by using a spark plug for ignition; the high boiling point, high cetane fuel refers to a fuel that can be ignited by compression by the piston of an engine.
In a preferred embodiment of the present invention, the first fuel comprises one or more of the following compounds: one or more of gasoline, methanol, ethanol, propanol, butanol and isooctane; the second fuel comprises one or more of the following compounds: diesel oil, Fischer-Tropsch synthetic diesel oil (F-T diesel oil), biodiesel, dimethyl ether, n-heptane and polyoxymethylene dimethyl ether (PODE).
The technical scheme utilizes the compression ignition characteristic of the fuel with high cetane number, so that the exothermic reaction occurs in the whole combustion chamber space, the flame propagation process is avoided, and the phenomenon of local over-concentration or local high temperature is avoided.
In one embodiment of the present invention, the injection pressure of the first fuel ranges from 20MPa to 120 MPa.
In one embodiment of the present invention, the injection pressure range of the second fuel is 120MPa or more.
The first fuel is a low activity fuel having relatively high volatility and relatively low viscosity, requiring the use of relatively low injection pressures, which if used can cause the first fuel to vaporize within the nozzle. The injection pressure of the first fuel is selected in the range of 20MPa to 120MPa depending on the specific fuel type.
The second fuel is high-activity fuel, has the characteristics of relatively low volatility and relatively high viscosity, and if the injection pressure is low, large molecular droplets are not easy to form small molecular droplets, so that the second fuel is incompletely combusted; the injection pressure of the second fuel is selected in the range of 120MPa and above depending on the specific fuel type.
According to actual tests, when the injection pressure of the first fuel ranges from 20MPa to 120MPa, the first fuel can achieve the optimal atomization effect; when the injection pressure range of the second fuel is 120MPa or more, the second fuel can be atomized optimally.
The injection time of the third fuel is adjusted according to the state of the engine; injecting the third fuel when the engine knocks particularly severely and even possibly damages the engine, the third fuel including a knock suppressant; the third fuel, which includes a cetane booster, is injected when the activity of the fuel in the engine combustion chamber is too low to compression ignite.
According to the technical scheme, the in-cylinder mixed gas with the optimal fuel activity gradient and concentration is formed in the combustion chamber in a layered mode, and an ICCI combustion mode is further performed, so that the engine has the characteristics of low emission and high thermal efficiency, and the rated output torque of the engine can be controlled by adjusting the distribution and the composition of the mixed gas, so that the transmitter has a wider working load range.
In order to achieve the above object, the present invention also discloses a fuel injection device of a multi-fuel charge compression combustion engine, comprising a direct injection system, a port injection system, and a controller, wherein:
the direct injection system comprises a first direct injection system, a second direct injection system, the first direct injection system being in communication with the combustion chamber and configured to directly inject the first fuel into the combustion chamber; the second direct injection system is in communication with the combustion chamber and is configured to directly inject the second fuel into the combustion chamber; and the port injection system is in communication with an intake port and is configured to inject the third fuel into the intake port;
the controller is configured to be able to control the direct injection system and the port injection system according to the fuel injection method described above.
In one technical scheme of the invention, an included angle between the first direct injection system and a central axis of the cylinder of the engine is more than or equal to 0 degree and less than or equal to 60 degrees; an angle between a fuel injection center axis of the second direct injection system and a center axis of the cylinder of the engine is greater than or equal to 0 ° and less than or equal to 60 °.
Further, the first and second direct injection systems are both common rail injection systems; the common rail injection system separates the fuel pressure generation from the fuel injection, and adopts an electromagnetic fuel injector controlled by an electromagnetic valve to replace a traditional mechanical fuel injector; the electric control unit acts on pulse signals of an electromagnetic valve of the electromagnetic oil injector to control the injection process of fuel, and the size of the oil injection quantity depends on the oil pressure in a fuel oil rail, the opening time of the electromagnetic valve and the liquid flow characteristic of an oil nozzle.
The first direct injection system comprises a first electric control oil injector, the second direct injection system comprises a second electric control oil injector, and the first electric control oil injector and the second electric control oil injector are arranged on the cylinder cover, so that the structural complexity of the engine can be reduced, and the development cost of the engine can be reduced; the common rail injection system is favorable for reducing the pressure fluctuation of the injection system, reducing the mutual interference of each oil injector and improving the control precision of the injection pressure and the control accuracy of the oil injection quantity.
As described above, compared with the prior art, the present invention has the following beneficial effects:
1) the invention provides a fuel injection method and a device of a multi-fuel charge compression combustion engine, which adopts two sets of mutually independent direct injection systems and one set of gas port injection system and can regulate and control each injection system at any time in the whole engine cycle process; the closed cycle control of the full working condition range and the combustion process can be realized.
2) The invention provides a fuel injection method and a device of a multi-fuel charge compression combustion engine, which disclose the injection time, the injection quantity and the injection times of various fuels under different working conditions, and form flexible and reliable concentration and activity layering in a cylinder according to different working conditions, thereby forming the optimal fuel activity gradient, improving the heat efficiency of the engine to the maximum extent, reducing the emission, and completely meeting the emission standard of the country VI due to the emission of nitric oxides, and simultaneously having wider working load range.
3) The fuel injection method and the device of the multi-fuel charge compression combustion engine provided by the invention have very outstanding application values in the field of mechanical engineering, particularly in the field of automobile engines.
Drawings
FIG. 1 is a schematic diagram of an engine employing a preferred embodiment of the present invention.
Wherein: 1-air inlet channel, 2-third electric control injector, 3-cylinder cover, 4-first electric control injector, 41-first fuel injection central axis, 5-first fuel, 6-second electric control injector, 61-second fuel injection central axis, 7-second fuel, 8-exhaust channel, 9-combustion chamber, and 91-cylinder central axis.
Detailed Description
The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.
In the drawings, structurally identical elements are represented by like reference numerals, and structurally or functionally similar elements are represented by like reference numerals throughout the several views. The size and thickness of each component shown in the drawings are arbitrarily illustrated, and the present invention is not limited to the size and thickness of each component. The thickness of the components may be exaggerated where appropriate in the figures to improve clarity.
In the description of the embodiments of the present application, it should be clear that the terms "center", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "horizontal", "upstream", "downstream", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of describing the embodiments of the present application and simplifying the description, but do not indicate or imply that the described devices or elements must have specific orientations or positional relationships, i.e., cannot be construed as limitations on the embodiments of the present application; furthermore, the terms "first," "second," and the like are used merely to facilitate description or simplify description, and do not indicate or imply importance.
FIG. 1 shows a schematic diagram of an engine employing a preferred embodiment of the present invention, including: a cylinder and cylinder head 3; a piston (not shown) disposed in the cylinder, and defining a combustion chamber 9 between the piston and the inner peripheral wall of the cylinder and the cylinder head 3; the air inlet 1 is arranged on the cylinder cover 3, and the air inlet 1 is communicated with the combustion chamber 9; the exhaust passage 8 is arranged on the cylinder cover 3, and the exhaust passage 8 is communicated with the combustion chamber 9; the system comprises a direct injection system, an air passage opening injection system and a controller (not shown in the figure), wherein the direct injection system comprises a first direct injection system and a second direct injection system, and the first direct injection system, the second direct injection system and the air passage opening injection system are mutually independent; only one combustion chamber 9 is shown in fig. 1, and the engine may be provided with a plurality of combustion chambers 9.
The first direct injection system and the second direct injection system both inject fuel into the combustion chamber 9; the gas port injection system injects fuel into the gas inlet 1; the first direct injection system comprises a first electric control oil injector 4, the second direct injection system comprises a second electric control oil injector 6, and the gas channel opening injection system comprises a third electric control oil injector 2; the third electric control oil injector 2 is arranged on the air inlet channel 1; the first electric control oil injector 4 and the second electric control oil injector 6 are arranged on the cylinder cover 3, the included angle between the first fuel injection central axis 41 of the first electric control oil injector 4 and the cylinder central axis 91 is more than or equal to 0 degree and less than or equal to 60 degrees, and the included angle between the second fuel injection central axis 61 of the second electric control oil injector 6 and the cylinder central axis 91 is more than or equal to 0 degree and less than or equal to 60 degrees.
The arrangement of the first and second electronically controlled injectors 4 and 6 described above facilitates mixing and diffusion of the fuel in the combustion chamber 9.
In some embodiments, the first direct injection system and the second direct injection system are both common rail injection systems, the fuel injected by the first direct injection system is a first fuel 5, the first fuel 5 is one or a combination of low boiling point and high octane number fuel, in some preferred embodiments, the first fuel 5 is gasoline, and the injection pressure of the first fuel 5 is in a range of 20MPa to 120 MP; the fuel injected by the second direct injection system is the second fuel 7, the second fuel 7 is one or the combination of high boiling point and high cetane number fuel, in some preferred embodiments, the second fuel 7 is diesel, and the injection pressure range of the second fuel 7 is 120MPa and above.
In some preferred embodiments, the first fuel 5 injected by the first direct injection system is a low activity fuel having relatively high volatility and relatively low viscosity, requiring the use of relatively low injection pressures, which if used are too high, would cause the first fuel 5 to vaporize in the nozzle. The injection pressure of the first direct injection system is selected in the range of 20MPa to 120MPa depending on the specific first fuel 5.
The second fuel 7 injected by the second direct injection system is high-activity fuel which has the characteristics of relatively low volatility and relatively high viscosity, and if the injection pressure is low, large molecular droplets are not easy to form small molecular droplets, so that the combustion of the second fuel 7 is incomplete; the injection pressure of the second direct injection system is selected in the range of 120MPa and above depending on the specific second fuel 7.
According to actual tests, when the injection pressure of the first direct injection system is in the range of 20MPa to 120MPa, the first fuel 5 can achieve the best atomization effect; when the injection pressure range of the second direct injection system is 120MPa or more, the second fuel 7 can be atomized optimally.
The two sets of independent direct injection systems can inject fuel at any time in the range from an intake stroke to a compression stroke, so that the injection combination of the fuel with different characteristics and concentrations is realized, the injection combination of the mixed fuel with the same type and different concentrations can also be realized, and the auxiliary injection is carried out through the air passage opening injection system; after the first fuel 5 and the second fuel 7 are fully mixed in the combustion chamber 9 to form the optimal concentration and activity stratification, when the piston is compressed, the heat release reaction is caused to occur in the whole combustion chamber 9 space by utilizing the compression ignition characteristic of the fuel with high cetane number, and the phenomena of flame propagation and local over-concentration or local high temperature are avoided.
In order to flexibly realize the concentration and activity stratification of the mixture gas in the cylinder so as to form the optimal fuel activity gradient, the following fuel injection methods are adopted in some preferred embodiments:
the working condition of the engine is sensed, and the controller can calculate the working condition of the engine according to the crankshaft position information, the camshaft position information and the in-cylinder pressure information.
During the cycle of the cylinder, the controller adopts different injection times, fuel injection amount and injection time range for each direct injection system and each gas port injection system according to different working conditions of the engine, and controls the temperature of the intake air entering through the air intake passage 1. The working condition of the engine can be divided into idling, starting, small load, medium load, large load or full load. Depending on the range of desired engine output torques, idle operating conditions and pull-off operating conditions may be combined into one category, and high load operating conditions and full load operating conditions may be combined into one category in some embodiments.
When the engine works in an idling or starting working condition, the first direct injection system injects the first fuel 5 once and the second direct injection system injects the second fuel 7 once in each cycle of the cylinder; the spraying time range of the first direct spraying system is from-350 ℃ A ATDC to-280 ℃ A ATDC; the injection quantity of the first fuel 5 is in the range of 30% to 50% of the total fuel injection quantity of the engine under the operating condition; the injection time range of the second direct injection system is from-50 ℃ A ATDC to-30 ℃ A ATDC; and meanwhile, the air inlet temperature of the air inlet channel 1 is controlled within the range of 40-60 ℃, so that the ignition reliability and the heat efficiency of the engine are improved.
When the engine works in a low-load working condition, the first direct injection system injects the first fuel 5 once and the second direct injection system injects the second fuel 7 once during each cycle of the cylinder; the spraying time range of the first direct spraying system is from-350 ℃ A ATDC to-280 ℃ A ATDC; the injection quantity of the first fuel 5 is in the range of 60% to 80% of the total fuel injection quantity of the engine under the operating condition; the injection timing of the second direct injection system ranged from-70 ℃ A ATDC to-50 ℃ A ATDC.
The first direct injection system injects the first fuel 5 once or twice and the second direct injection system injects the second fuel 7 once or twice during each cycle of the cylinder when the engine is operating at medium load operating conditions; the injection quantity of the first fuel 5 is in the range of 70% to 90% of the total fuel injection quantity of the engine under the operating condition.
When the engine is operated under a large load or full load working condition, the first direct injection system injects the first fuel 5 once and the second direct injection system injects the second fuel 7 twice during each cycle of the cylinder; the spraying time range of the first direct spraying system is from-350 ℃ A ATDC to-280 ℃ A ATDC; the spraying time range of the first spraying of the second direct spraying system is-60 ℃ A ATDC to-40 ℃ A ATDC, and the spraying time range of the second spraying of the second direct spraying system is-10 ℃ A ATDC to-1 ℃ A ATDC; the injection quantity of the first fuel 5 is in the range of 40% to 60% of the total fuel injection quantity of the engine; the injection quantity of the first injection of the second fuel 7 accounts for 20-30% of the total fuel injection quantity of the engine under the working condition, and the injection quantity of the second injection of the second fuel 7 accounts for 20-30% of the total fuel injection quantity of the engine under the working condition.
When the engine is in the above various working conditions, the auxiliary fuel or additive can be injected through the gas port injection system according to the requirements.
In some embodiments, the injection timing of the third fuel is adjusted according to the state of the engine; injecting a third fuel when the engine knocks particularly severely and even potentially damages the engine, the third fuel including a knock suppressant; when the activity in the engine combustion chamber is too low to allow compression ignition, a third fuel is injected, the third fuel including a cetane booster.
Through research, the inventor can flexibly realize concentration and activity layering of mixed gas in a cylinder by adopting the technical scheme, so that the optimal fuel activity gradient is formed, and an ICCI combustion mode is further performed, so that the optimal thermal efficiency and the lowest emission are kept under each working condition, the emission of nitrogen oxides can completely meet the emission standard of the state VI, and the working load range is wider.
The fuel injection method and the device of the multi-fuel charge compression combustion engine have very outstanding application value in the field of mechanical engineering, particularly in the field of automobile engines.
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.
Claims (16)
1. A method of fuel injection in a multi-fuel charge compression combustion engine comprising the steps of:
sensing an operating condition of the engine;
adjusting an injection strategy for directly injecting fuel into a combustion chamber of the engine during a cylinder cycle of the engine based on the operating condition of the engine;
controlling an intake air temperature of an intake air passage, wherein the intake air passage communicates with the combustion chamber to intake air to the combustion chamber; and
adjusting an injection strategy for injecting fuel into the intake port;
wherein the injection strategy comprises the injection times, the fuel injection quantity and the injection time range;
the injection strategy further comprises: injecting a first fuel and a second fuel directly into the combustion chamber; and injecting a third fuel into the intake port;
when the operating condition of the engine is idling or starting, the injection timing of the first fuel ranges from-350 ℃ A ATDC to-280 ℃ A ATDC, and the injection timing of the second fuel ranges from-50 ℃ A ATDC to-30 ℃ A ATDC;
when the operating condition of the engine is a low load, the injection timing of the first fuel ranges from-350 ℃ A ATDC to-280 ℃ A ATDC, and the injection timing of the second fuel ranges from-70 ℃ A ATDC to-50 ℃ A ATDC;
when the operating condition of the engine is a large load or a full load, the injection timing of the first fuel ranges from-350 ℃ A ATDC to-280 ℃ A ATDC; the injection time range of the first injection of the second fuel is-60 ℃ A ATDC to-40 ℃ A ATDC, and the injection time range of the second injection of the second fuel is-10 ℃ A ATDC to-1 ℃ A ATDC.
2. The method of fuel injection for a multi-fuel charge compression-ignition engine of claim 1 wherein the number of injections of the first fuel is a single and the number of injections of the second fuel is a single during each cycle of the cylinder when the operating condition of the engine is idle, start, or low load.
3. The fuel injection method for a multi-fuel charge compression-ignition engine according to claim 2, wherein the intake air temperature ranges from 40 ℃ to 60 ℃ when the operating condition of the engine is idling or off, or the injection amount of the first fuel is in a range of 30% to 50% in proportion to the total fuel injection amount when the operating condition is idling or off.
4. The fuel injection method for a multi-fuel charge compression-combustion engine according to claim 2, characterized in that when the operating condition of the engine is a small load, the injection quantity of the first fuel is in a range of 60% to 80% of the total fuel injection quantity when the operating condition is a small load.
5. The fuel injection method of a multi-fuel charge compression combustion engine of claim 1, wherein the number of injections of the first fuel is single or double during each cycle of the cylinder when the operating condition of the engine is medium load.
6. The fuel injection method of a multi-fuel charge compression combustion engine of claim 5, wherein the number of injections of the second fuel is single or double during each cycle of the cylinder when the operating condition of the engine is medium load.
7. The fuel injection method of a multi-fuel charge compression combustion engine of claim 6, wherein the injection quantity of the first fuel is in a range of 70% to 90% as a percentage of the total fuel injection quantity at medium load operating conditions.
8. The method of fuel injection for a multi-fuel charge compression ignition engine of claim 1 wherein the number of injections of the first fuel is a single and the number of injections of the second fuel is two during each cycle of the cylinder when the operating condition of the engine is a large load or a full load.
9. The method of fuel injection for a multi-fuel charge compression combustion engine of claim 8 wherein the injected quantity of the first fuel is in the range of 40% to 60% of the total fuel injected quantity at the operating conditions of large or full load.
10. The fuel injection method of a multi-fuel charge compression combustion engine of claim 8, wherein the injection quantity of the first injection of the second fuel is in a range of 20% to 30% of the total fuel injection quantity at the time of the operating condition of a large load or a full load, and the injection quantity of the second injection of the second fuel is in a range of 20% to 30% of the total fuel injection quantity at the time of the operating condition of a large load or a full load.
11. The method of fuel injection for a multi-fuel charge compression combustion engine of claim 1, wherein the first fuel comprises a low boiling, high octane fuel and the second fuel comprises a high boiling, high cetane fuel.
12. The fuel injection method of a multi-fuel charge compression combustion engine of claim 11, in which the injection pressure of the first fuel ranges from 20MPa to 120 MPa.
13. The method of fuel injection for a multi-fuel charge compression combustion engine of claim 12, wherein the injection pressure of the second fuel is in the range of 120MPa and above.
14. The method of fuel injection for a multi-fuel charge compression combustion engine of claim 1, wherein the third fuel comprises a supplemental fuel or an additive.
15. A fuel injection apparatus for a multi-fuel charge compression combustion engine comprising a direct injection system, a port injection system, and a controller, wherein:
the direct injection system comprises a first direct injection system, a second direct injection system, the first direct injection system being in communication with the combustion chamber and configured to directly inject the first fuel into the combustion chamber; the second direct injection system is in communication with the combustion chamber and is configured to directly inject the second fuel into the combustion chamber; and the port injection system is in communication with an intake port and is configured to inject the third fuel into the intake port;
the controller is configured to be able to control the direct injection system and the port injection system according to the fuel injection method of any one of claims 2 to 14.
16. The fuel injection apparatus of the multi-fuel charge compression combustion engine of claim 15, wherein the angle of the first direct injection system to the central axis of the cylinder of the engine is greater than or equal to 0 ° and less than or equal to 60 °; an angle between a fuel injection center axis of the second direct injection system and a center axis of the cylinder of the engine is greater than or equal to 0 ° and less than or equal to 60 °.
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