CN109441626B - Dual-fuel engine combustion organization method adopting main and auxiliary fuel injectors and manifold for multiple injection - Google Patents

Dual-fuel engine combustion organization method adopting main and auxiliary fuel injectors and manifold for multiple injection Download PDF

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CN109441626B
CN109441626B CN201811017333.XA CN201811017333A CN109441626B CN 109441626 B CN109441626 B CN 109441626B CN 201811017333 A CN201811017333 A CN 201811017333A CN 109441626 B CN109441626 B CN 109441626B
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injection
load
oil
cylinder
oil sprayer
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CN109441626A (en
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杨立平
何永恒
王立媛
宋恩哲
姚崇
孙军
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Harbin Engineering University
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Harbin Engineering University
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B69/00Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types
    • F02B69/02Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types for different fuel types, other than engines indifferent to fuel consumed, e.g. convertible from light to heavy fuel
    • F02B69/04Internal-combustion engines convertible into other combustion-engine type, not provided for in F02B11/00; Internal-combustion engines of different types characterised by constructions facilitating use of same main engine-parts in different types for different fuel types, other than engines indifferent to fuel consumed, e.g. convertible from light to heavy fuel for gaseous and non-gaseous fuels
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D19/00Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/0639Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels
    • F02D19/0642Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions
    • F02D19/0647Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions the gaseous fuel being liquefied petroleum gas [LPG], liquefied natural gas [LNG], compressed natural gas [CNG] or dimethyl ether [DME]
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D19/00Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/0663Details on the fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02D19/0686Injectors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D19/00Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/08Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed simultaneously using pluralities of fuels
    • F02D19/081Adjusting the fuel composition or mixing ratio; Transitioning from one fuel to the other
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/30Controlling fuel injection
    • F02D41/3094Controlling 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
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/30Use of alternative fuels, e.g. biofuels

Abstract

The invention belongs to the technical field of combustion of internal combustion engines, and particularly relates to a dual-fuel engine adopting a main oil injector, an auxiliary oil injector and a manifold for multiple injection and a combustion organization method thereof. The dual-fuel engine comprises a piston, a cylinder sleeve, a cylinder cover, a main oil injector, an auxiliary oil injector, a manifold low-pressure fuel gas injection device and the like; the main oil sprayer is arranged in the center of the cylinder cover, and the diesel oil spraying proportion at low load can be controlled by changing the oil spraying pulse width of the main oil sprayer; the auxiliary oil injector is obliquely arranged on the cylinder cover, micro-sprays diesel oil at medium and high load, and ignites natural gas after the diesel oil is self-ignited near a top dead center; the manifold low-pressure gas injection valve is arranged on an air inlet manifold of each cylinder, and the injection times and the timing of the low-pressure gas injection valve are controlled when the load is medium and high, so that reasonable mixed gas concentration distribution is formed in the cylinder. According to the invention, ignition stability under different working conditions is ensured by diesel ignition, and different oil gas injection strategies are adopted under different working conditions, so that reasonable oil gas distribution is realized in a cylinder to achieve a good combustion effect, thereby improving the economy and emission of the engine.

Description

Dual-fuel engine combustion organization method adopting main and auxiliary fuel injectors and manifold for multiple injection
Technical Field
The invention belongs to the technical field of combustion of internal combustion engines, and particularly relates to a dual-fuel engine adopting a main oil injector, an auxiliary oil injector and a manifold for multiple injection and a combustion organization method thereof.
Background
The diesel/natural gas dual fuel engine can run in two fuel modes, the economy is high, and the cost of refitting is generally lower than that of the engine directly using gas fuel. At the same time, the greatest advantage of dual fuels is that NOx and PM emissions can be reduced simultaneously, which is difficult to achieve in conventional diesel engines. Relevant tests show that the NOx emission of the dual-fuel engine is lower than that of a diesel engine, the middle and low load can be reduced by about 50%, meanwhile, the particulate matter emission of the dual-fuel engine can be reduced by about 70% compared with that of the diesel engine, and the effect is obvious.
On the other hand, a dual fuel engine is higher in thermal efficiency than a spark ignition engine but lower in thermal efficiency than a diesel engine. Compared with a spark ignition engine, the diesel oil is easy to ignite at multiple points, the mixed gas is burnt quickly, the natural gas is allowed to work under the condition of a larger compression ratio, and the heat efficiency of the engine can be improved. However, since the gas passage injects natural gas, the engine charging efficiency is reduced, and therefore the thermal efficiency of the dual fuel engine is generally lower than that of the diesel engine, and is substantially equivalent to that of the diesel engine at a large load. The natural gas substitution rate of the dual-fuel engine can affect the combustion condition in the cylinder, and particularly at medium and low loads, the combustion is deteriorated due to the high natural gas substitution rate, and even the phenomena of engine fire, circulation change aggravation and the like occur. Compared with a spark plug ignition type natural gas engine, the diesel oil serving as an ignition source is widely distributed in a combustion chamber, so that the ignition energy of the natural gas is increased, the ignition stability and the combustion rate of the natural gas are improved, and the dynamic property and the thermal efficiency of the engine are further improved.
In the aspect of improving the fuel injection mode of the dual-fuel engine, some patents regulate the fuel injection quantity such as CN105020073A by setting a preset value, and the aims of reducing emission and improving combustion under different loads are fulfilled by presetting the fuel injection quantity and fuel injection timing in a control system; there are patents summarizing possible fuel injection patterns of dual-fuel engines such as CN106870186A, which implement different combustion patterns by combining different fuel injection patterns. In the aspect of improving a combustion system, a patent realizes homogeneous premixed compression ignition such as CN102996223A by injecting fuels with different octane numbers through a main nozzle and an auxiliary nozzle, and the patent provides a premixed combustion system of a diesel engine, which can ensure higher thermal efficiency; some patents have studied combustion systems comprising switchable fuel injectors, such as CN204402678U, and the combustion system comprises multiple sets of fuel supply devices, and the operating modes of the fuel supply devices are changed by the switchable fuel injectors and corresponding control systems, so as to realize the switching of the combustion modes under different working conditions. None of these patents considers which combustion mode is used under what conditions, how to organize mixture formation and high efficiency low emission combustion in the main combustion chamber, and how to improve engine stable ignition in gas mode.
Disclosure of Invention
The invention aims to provide a dual-fuel engine with high dynamic property, high economical efficiency and high emission performance and adopting a main fuel injector, an auxiliary fuel injector and a manifold for multiple injections.
A dual-fuel engine adopting a main oil injector, an auxiliary oil injector and a manifold for multiple injection comprises a piston, a cylinder sleeve, a cylinder cover, the auxiliary oil injector, the main oil injector, an air inlet valve, a manifold low-pressure fuel gas injection device, an air inlet channel and a combustion chamber; the combustion chamber consists of the upper surface of the piston, the peripheral wall of the cylinder sleeve and the lower surface of the cylinder cover; the main oil sprayer and the auxiliary oil sprayer are arranged in the cylinder cover, the main oil sprayer is positioned in the center of the cylinder cover, the axis of the main oil sprayer is overlapped with the axis of the cylinder, the auxiliary oil sprayer is arranged on the right side of the cylinder cover, and the angle formed by the axis and the lower surface of the cylinder cover is 30-70 degrees; the manifold low-pressure fuel gas injection valve is arranged on an air inlet manifold of each cylinder, and an air inlet stroke exhaust valve is closed to supply air to the cylinder during the closing period of an air inlet valve.
The main oil sprayer is a porous high-flow oil sprayer, the auxiliary oil sprayer is a small-flow oil sprayer, the two oil sprayers work independently, and the maximum flow of the auxiliary oil sprayer is only 1-5% of the maximum flow of the main oil sprayer.
The number of the spray holes of the main oil sprayer is 6-8, and the plurality of spray holes of the auxiliary oil sprayer are arranged on one side of the spray nozzle and spray a plurality of oil bundles.
The combustion chamber adopts a hemispherical structure.
The invention also aims to provide a combustion organization method of the dual-fuel engine adopting the main-auxiliary fuel injector and the manifold for multiple injection.
A dual-fuel engine combustion organization method adopting a main fuel injector, an auxiliary fuel injector and a manifold for multiple injection is characterized by comprising the following steps:
step 1, judging engine load and selecting an engine working mode;
step 2, air inlet process;
step 3, a gas compression process;
step 4, a combustion work-doing process;
and 5, exhausting.
The step 1 specifically comprises:
firstly, when the load is low, namely the load is lower than 15%, the dual-fuel engine adopts a diesel oil working mode, and a main oil sprayer is selected as an oil sprayer;
secondly, when the medium load is in accordance with 15% -70%, the dual-fuel engine adopts a natural gas working mode, and the oil injector adopts a secondary oil injector;
and thirdly, when the high load is larger than 70%, the dual-fuel engine is switched to a homogeneous gas working mode, and at the moment, the manifold low-pressure gas injection valve and the auxiliary oil injector work together.
The step 2 specifically comprises:
firstly, when the load is low, namely the load is lower than 15%, the main oil injector injects diesel oil to the cylinder within the range of 30 ℃ A before the top dead center at the end of the compression stroke;
secondly, when the load is 15-50%, the manifold low-pressure fuel gas injection valve adopts single injection, the injection timing is within the range of 10 ℃ A before and after the maximum lift range of the valve opening, the auxiliary fuel injector adopts two times of injection, the first injection timing is 70 ℃ A before the compression top dead center, the second injection timing is within the range of 0-30 ℃ A before the compression top dead center, and the diesel injection proportion accounts for 1-5% of the proportion of the whole circulating fuel under the load of 100%;
thirdly, when the load is 50-70%, the manifold low-pressure fuel gas injection valve adopts two times of injection, the first time of injection is within the range of 0-30 ℃ A after the exhaust valve is closed, the second time of injection is within the range of 10-30 ℃ A after the intake valve is opened to the maximum lift, the auxiliary fuel injector adopts two times of injection, the first time of injection is 70 ℃ A before the compression top dead center, the second time of injection is within the range of 0-30 ℃ A before the compression top dead center, and the diesel injection proportion accounts for 1-5% of the whole cycle fuel quantity proportion under 100% load;
and fourthly, when the high load is more than 70 percent, the manifold low-pressure fuel gas injection valve adopts single injection, the injection timing is in the range of 0-30 ℃ A after the exhaust valve is closed, the auxiliary fuel injector adopts single injection, diesel oil is injected into the cylinder in the range of 5-15 ℃ A before the compression top dead center, and the proportion of the injected diesel oil accounts for 1-5 percent of the proportion of the whole circulating fuel under the load of 100 percent.
The invention has the beneficial effects that:
the engine has the advantages that the reasonable matching design is made on the combustion mode of the dual-fuel engine and the oil-gas injection strategy, and different influence factors are considered under different working conditions, so that the engine has better comprehensive performance; ignition stability of natural gas under different working conditions is guaranteed through diesel oil ignition, different injection times and injection pulse widths are adopted under different working conditions through the low-pressure fuel gas injection valve and the main-auxiliary fuel injector, and oil gas concentration gradient distribution of reasonable scales is formed in the combustion chamber, so that oil gas is quickly, efficiently and low in emission combustion, flame propagation speed is accelerated, combustion time is shortened, combustion quality is improved, exhaust temperature is reduced, and the problems of fire catching and knocking of a dual-fuel engine can be solved.
Drawings
FIG. 1 is a detailed layout diagram of a dual fuel engine combustion system in an embodiment of the present invention;
FIG. 2 is a schematic diagram of the main injector spraying diesel fuel;
FIG. 3 is a schematic diagram of in-cylinder oil and gas distribution at medium load;
fig. 4 is a schematic diagram of the in-cylinder natural gas concentration distribution at high load.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
as shown in fig. 1, which is a specific layout diagram of a dual-fuel engine combustion system in an embodiment of the present invention, a dual-fuel engine combustion system structure that adopts a main-auxiliary fuel injector and a manifold for multiple injections includes: the device comprises a piston 1, a cylinder sleeve 2, a cylinder cover 3, an auxiliary fuel injector 4, a main fuel injector 5, an air inlet valve 6, a manifold low-pressure fuel gas injection device 7, an air inlet passage 8 and a combustion chamber 9. The combustion chamber consists of the upper surface of the piston, the peripheral wall of the cylinder sleeve and the lower surface of the cylinder cover; the main oil sprayer and the auxiliary oil sprayer are arranged in the cylinder cover, the main oil sprayer is positioned in the center of the cylinder cover, the axis of the main oil sprayer is overlapped with the axis of the cylinder, the auxiliary oil sprayer is arranged on the right side of the cylinder cover, and the angle formed by the axis and the lower surface of the cylinder cover is 30-70 degrees; the low-pressure gas injection valve is arranged on an air inlet manifold of each cylinder, and an air inlet stroke exhaust valve is closed to supply air to the cylinder during the closing period of an air inlet valve.
The combustion organization method is suitable for a four-stroke natural gas engine, and each cycle comprises an intake stroke, a compression stroke, a combustion power stroke and an exhaust stroke. When the load is low, namely the load is lower than 15%, the dual-fuel engine is in a diesel oil working mode, natural gas is prone to fire and other problems due to lean combustion when the load is low, only the main oil injector works at the moment, diesel oil is injected into the cylinder within the range of 30 ℃ A before the top dead center at the end of a compression stroke, the diesel oil atomization schematic diagram is shown in figure 2, the multi-hole nozzle can enable the diesel oil to form a plurality of concentration areas in the cylinder, the atomization effect is good, the injection quantity of the diesel oil is small, the combustion is slow, air is sufficient, the combustion is sufficient, and good emission performance can be achieved.
When the load is 15% -70%, the dual-fuel engine is switched to a fuel gas working mode, but natural gas concentration stratification with different scale gradients is adopted under different loads, after an intake stroke exhaust valve is closed under 15-50% of load, single injection of a low-pressure fuel gas injection valve is started, the injection timing is within a range of 10 ℃ A before and after the maximum lift of the valve opening, and at the moment, the injected natural gas can form natural gas concentration stratification with a larger scale in a cylinder; when the load is 50-70%, the low-pressure gas injection valve adopts two times of injection, the first time of injection is in the range of 0-30 ℃ A after the exhaust valve is closed, the second time of injection is in the range of 10-30 ℃ A after the intake valve is opened to the maximum lift, the gas injected for the first time forms more uniform dilute mixed gas in the cylinder, the gas injected for the second time is intensively distributed on the upper layer of the combustion chamber to form the concentration distribution of natural gas with rich top and lean bottom, the auxiliary oil injector adopts two times of injection, the first time of injection is 70 ℃ A before the top dead center of compression, the second time of injection is in the range of 0-30 ℃ A before the top dead center of compression, the injection proportion of diesel oil accounts for 1-5% of the proportion of the whole circulating fuel under 100% of load, the diesel oil forms a plurality of concentration centers after being injected into the cylinder, and forms the concentration distribution state of mixed gas with the natural gas injected by the intake stroke and, meanwhile, diesel oil sprayed by the auxiliary oil sprayer forms a plurality of ignition centers in the cylinder to realize stable ignition of mixed gas, so that quick, efficient and low-emission combustion of oil gas is realized, the flame propagation speed is accelerated, and the post-combustion period is shortened.
When the load is higher than 70%, the dual-fuel engine is switched to a homogeneous gas working mode, at the moment, the low-pressure gas injection valve and the auxiliary oil injector work together, because more gas is needed when the load is high, and meanwhile, the high-load combustion temperature and the temperature rise are high, in order to achieve a good emission effect, the gas injection valve adopts single injection, the injection timing is in the range of 0-30 ℃ A after the exhaust valve is closed, so that more uniform mixed gas can be formed in a cylinder as shown in figure 4, but the natural gas has higher ignition point and can not self-ignite, so that the auxiliary oil injector needs to micro-inject diesel oil for ignition, the auxiliary oil injector adopts single injection, the injection proportion of the diesel oil is 1-5% of the proportion of the whole cycle fuel quantity under 100% load in the range of 5-15 ℃ A before the compression top dead point, and the diesel oil can form a plurality of ignition points to ignite the mixed gas, the emission of NOx can be effectively reduced.
The invention provides a combustion organization method of a dual-fuel engine adopting a main oil injector, an auxiliary oil injector and a manifold for multiple injection. The main oil sprayer is arranged in the center of the cylinder cover and controls the diesel oil injection proportion at low load by changing the oil injection pulse width; the auxiliary oil injector is obliquely arranged on the cylinder cover, micro-sprays diesel oil at medium and high load, and ignites natural gas after the diesel oil is self-ignited near a top dead center; the low-pressure gas injection valve is arranged on an air inlet manifold of each cylinder, and when the load is medium and high, reasonable mixed gas concentration distribution is formed in the cylinder by controlling the injection times and timing of the low-pressure gas injection valve. According to the invention, ignition stability under different working conditions is ensured by diesel ignition, and oil gas is reasonably distributed in the cylinder to achieve a good combustion effect by adopting different oil gas injection strategies under different working conditions, so that the economical efficiency and the emission performance of the engine are improved.
A combustion organization method of a dual-fuel engine adopting a main-auxiliary fuel injector and manifold for multiple injection structurally comprises the following steps: the fuel injection device comprises a piston 1, a cylinder sleeve 2, a cylinder cover 3, a secondary fuel injector 4, a main fuel injector 5, an air inlet valve 6, a manifold low-pressure fuel gas injection device 7, an air inlet passage 8 and a combustion chamber 9. The dual-fuel engine adopts a dual-injector structure, namely an auxiliary injector 4 and a main injector 5, the two injectors work independently, the maximum flow of the auxiliary injector 4 is far less than that of the main injector 5, the maximum flow of the auxiliary injector 4 is only 1-5% of that of the main injector 5, the auxiliary injector 4 only works in a fuel gas mode of the dual-fuel engine, and does not work in a fuel oil mode; the main oil sprayer 5 only works under the low load of the pure diesel mode and the gas mode of the dual-fuel engine; the main oil sprayer is arranged in the center of the cylinder cover, the auxiliary oil sprayer is obliquely arranged on the right side of the cylinder cover, and a plurality of spray holes of the auxiliary oil sprayer are arranged on one side of the spray nozzle and spray a plurality of oil bundles; the combustion chamber has a hemispherical structure, and a plurality of oil beams sprayed by the oil sprayer in a gas mode are uniformly distributed in the hemispherical combustion chamber, so that the flame propagation distance can be shortened; the manifold low-pressure fuel gas injection valve is arranged on the air inlet manifold of each cylinder, and can realize multiple injection of fuel gas in the whole air inlet process in a gas mode; when the engine is in a diesel oil working mode at low load (< 15%), the main oil sprayer mainly sprays diesel oil into the cylinder at the moment, the auxiliary oil sprayer does not work at the moment, the main oil sprayer adopts single injection, and the injection timing is within the range of 10-30 ℃ A before the compression top dead center; during medium load, the engine can be switched to a gas working mode, the auxiliary oil injector and the low-pressure gas injection valve work cooperatively, the natural gas concentration gradient distribution with a large scale from top to bottom is adopted during 15-50% of medium and low load, the manifold low-pressure gas injection valve performs single injection, and the injection timing is within a range of 10 ℃ A before and after the maximum lift of the valve opening; the natural gas concentration gradient distribution from top to bottom is adopted when the load is 50-70%, the manifold low-pressure gas injection valve adopts two times of injection, the first time of injection is in the range of 0-30 ℃ A after the exhaust valve of the intake stroke is closed, the gas injected for the first time forms more uniform lean mixed gas in the cylinder, the second time of injection is in the range of 10-30 ℃ A after the maximum lift range of the opening of the intake valve, and the concentration stratification of the natural gas in the cylinder is realized by controlling the proportion and the timing of the two times of fuel injection; the auxiliary fuel injector can realize two times of injection, the first time of injection is 70 ℃ A before the compression top dead center, the injected diesel only provides an activated component for the cylinder and cannot independently ignite the mixed gas in the cylinder, the second time of injection is within the range of 0-30 ℃ A before the compression top dead center, the second time of injection starts the ignition effect, the diesel of the two times of injection is controlled to be 1-5% of the whole circulating fuel quantity under the condition that the engine operates in a diesel mode and the whole circulating fuel quantity accounts for 100% of load, the diesel injection can form a plurality of ignition centers in the cylinder to realize stable ignition, and the mixed gas concentration distribution with different scales is realized in the cylinder to realize high-efficiency low-emission combustion by controlling the injection times and the injection timing of the low-pressure fuel gas injection valve; when the load is high (> 70%), the engine is switched to a homogeneous gas working mode, gas is supplied into the cylinder mainly through a low-pressure gas injection valve at the moment, relatively uniform mixed gas is formed in the cylinder by controlling the injection timing, and the ignition is performed through micro-injection diesel, the low-pressure gas injection valve adopts single injection, the injection timing is in the range of 0-30 ℃ A after an exhaust valve is closed, the auxiliary oil injector adopts single injection, the injection timing is in the range of 5-15 ℃ A before a compression top dead center, and the injection proportion of the pilot diesel accounts for 1-5% of the proportion of the whole circulating fuel under the 100% load of a pure diesel mode. The engine can realize the flexible switching of gas mode and fuel mode to through adopting different oil gas injection strategies, make the homoenergetic of different operating modes in the jar realize that oil gas rational distribution in order to reach good combustion effect, thereby promote the economic nature and the emission nature of engine.
The main oil sprayer adopts a large-flow porous oil sprayer, the axis of the main oil sprayer is coincident with the axis of the cylinder, the number of spray holes is 6-8, the main oil sprayer works under the starting, idling and warming of a pure diesel mode and the low load of a gas mode, and does not work under the high load of the gas mode; the fuel injection quantity is small when the gas mode is low-load, and in order to ensure the ignition stability, the proportion of diesel oil in the fuel is relatively high, a main oil injector is adopted to inject the diesel oil into the cylinder, and the injected diesel oil has the double functions of igniting and doing work by combustion at the same time.
The auxiliary fuel injector is a small-flow multi-hole fuel injector, the spray holes of the auxiliary fuel injector are distributed on one side of a tangent plane passing through the central axis, the auxiliary fuel injector is obliquely arranged on the right side of the cylinder cover, the angle formed by the axis and the lower surface of the cylinder cover is 30-70 degrees, the auxiliary fuel injector works in a gas mode under high load, diesel sprayed by the auxiliary fuel injector mainly plays a role in ignition, and stops working in a diesel mode and a gas mode under low load.
The combustion chamber adopts the hemisphere combustion chamber, can shorten flame propagation distance, and the strong crowded turbulent intensity that flows and can improve near compression top dead center is favorable to oil-gas mixture process and burning.

Claims (1)

1. A dual-fuel engine combustion organization method adopting a main-auxiliary oil sprayer and manifold for multiple spraying comprises a piston, a cylinder sleeve, a cylinder cover, an auxiliary oil sprayer, a main oil sprayer, an air inlet valve, a manifold low-pressure fuel gas spraying device, an air inlet channel and a combustion chamber, wherein the main-auxiliary oil sprayer and the manifold are adopted for multiple spraying; the method is characterized in that: the combustion chamber consists of the upper surface of the piston, the peripheral wall of the cylinder sleeve and the lower surface of the cylinder cover; the main oil sprayer and the auxiliary oil sprayer are arranged in the cylinder cover, the main oil sprayer is positioned in the center of the cylinder cover, the axis of the main oil sprayer is overlapped with the axis of the cylinder, the auxiliary oil sprayer is arranged on the right side of the cylinder cover, and the angle formed by the axis and the lower surface of the cylinder cover is 30-70 degrees; the manifold low-pressure fuel gas injection valve is arranged on an air inlet manifold of each cylinder, and air is supplied to the cylinder from the closing of an air inlet stroke exhaust valve to the closing of an air inlet valve;
the main oil sprayer is a porous high-flow oil sprayer, the auxiliary oil sprayer is a small-flow oil sprayer, the two oil sprayers work independently, and the maximum flow of the auxiliary oil sprayer is only 1-5% of the maximum flow of the main oil sprayer;
the number of the spray holes of the main oil sprayer is 6-8, and a plurality of spray holes of the auxiliary oil sprayer are arranged on one side of the spray nozzle and spray a plurality of oil bundles;
the combustion chamber adopts a hemispherical structure;
the method is characterized by comprising the following steps:
step 1, judging engine load and selecting an engine working mode;
step 2, air inlet process;
step 3, a gas compression process;
step 4, a combustion work-doing process;
step 5, exhausting;
the step 1 specifically comprises:
firstly, when the load is low, namely the load is lower than 15%, the dual-fuel engine adopts a diesel oil working mode, and a main oil sprayer is selected as an oil sprayer;
secondly, when the medium load is in accordance with 15% -70%, the dual-fuel engine adopts a natural gas working mode, and the oil injector adopts a secondary oil injector;
when the load is high, namely the load is more than 70%, the dual-fuel engine is switched to a homogeneous fuel gas working mode, and at the moment, the manifold low-pressure fuel gas injection valve and the auxiliary fuel injector work together;
when the load is low, namely the load is lower than 15%, the main oil injector injects diesel oil to the cylinder within the range of 30 degrees CA before the top dead center at the end of the compression stroke;
when the load is 15-50%, the manifold low-pressure fuel gas injection valve adopts single injection, the injection timing is within the range of 10 CA degrees before and after the maximum lift of the valve opening, the auxiliary fuel injector adopts two times of injection, the first time of injection is within the range of 70 CA degrees before the top dead center of compression, the second time of injection is within the range of 0-30 CA degrees before the top dead center of compression, and the diesel injection proportion accounts for 1-5% of the proportion of the whole circulating fuel under 100% load;
when the load is 50-70%, the manifold low-pressure fuel gas injection valve adopts two times of injection, the first time of injection is in the range of 0-30 degrees CA after the exhaust valve is closed, the second time of injection is in the range of 10-30 degrees CA after the intake valve is opened to the maximum lift, the auxiliary fuel injector adopts two times of injection, the first time of injection is 70 degrees CA before the top dead center of compression, the second time of injection is in the range of 0-30 degrees CA before the top dead center of compression, and the diesel injection proportion accounts for 1-5% of the proportion of the whole circulating fuel under 100% load;
when the load is more than 70%, the manifold low-pressure fuel gas injection valve adopts single injection, the injection timing is in the range of 0-30 CA after the exhaust valve is closed, the auxiliary fuel injector adopts single injection, diesel oil is injected into the cylinder in the range of 5-15 CA before the compression top dead center, and the proportion of the injected diesel oil accounts for 1-5% of the proportion of the whole circulating fuel under the load of 100%.
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CN106870186A (en) * 2016-02-04 2017-06-20 大连理工大学 Dual fuel engine fuel injection manner

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CN106870186A (en) * 2016-02-04 2017-06-20 大连理工大学 Dual fuel engine fuel injection manner

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