CN116291907A - Multi-point low-pressure injection ammonia and diesel dual-fuel engine and combustion organization method - Google Patents

Multi-point low-pressure injection ammonia and diesel dual-fuel engine and combustion organization method Download PDF

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Publication number
CN116291907A
CN116291907A CN202310091070.1A CN202310091070A CN116291907A CN 116291907 A CN116291907 A CN 116291907A CN 202310091070 A CN202310091070 A CN 202310091070A CN 116291907 A CN116291907 A CN 116291907A
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liquid ammonia
injection
ammonia
fuel
air inlet
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杨立平
王豪杰
王立媛
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Harbin Engineering University
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Harbin Engineering University
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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
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling 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
    • F02D19/0602—Control of components of the fuel supply system
    • F02D19/0607—Control of components of the fuel supply system to adjust the fuel mass or volume flow
    • F02D19/061—Control of components of the fuel supply system to adjust the fuel mass or volume flow by controlling fuel injectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0645—Details related to the fuel injector or the fuel spray
    • F02B23/0663—Details related to the fuel injector or the fuel spray having multiple injectors per combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
    • F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
    • F02B23/0672—Omega-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder center axis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B31/00—Modifying induction systems for imparting a rotation to the charge in the cylinder
    • F02B31/02—Modifying induction systems for imparting a rotation to the charge in the cylinder in engines having inlet valves arranged eccentrically to cylinder axis
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B69/00—Internal-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
    • F02B69/02—Internal-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
    • F02B69/04—Internal-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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling 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
    • F02D19/0602—Control of components of the fuel supply system
    • F02D19/0613—Switch-over from one fuel to another
    • F02D19/0615—Switch-over from one fuel to another being initiated by automatic means, e.g. based on engine or vehicle operating conditions
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling 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
    • F02D19/0639—Controlling 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
    • F02D19/0642—Controlling 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
    • F02D19/0644—Controlling 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 hydrogen, ammonia or carbon monoxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling 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
    • F02D19/0663—Details on the fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02D19/0686—Injectors
    • F02D19/0689—Injectors for in-cylinder direct injection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling 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
    • F02D19/0663—Details on the fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02D19/0686—Injectors
    • F02D19/0692—Arrangement of multiple injectors per combustion chamber
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling 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
    • F02D19/08—Controlling 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
    • F02D19/081—Adjusting the fuel composition or mixing ratio; Transitioning from one fuel to the other
    • 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
    • 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
    • Y02T10/30—Use of alternative fuels, e.g. biofuels

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Fuel-Injection Apparatus (AREA)

Abstract

The invention aims to provide a multi-point low-pressure ammonia injection and diesel dual-fuel engine and a combustion organization method, the multi-point low-pressure ammonia injection and diesel dual-fuel engine comprises a cylinder sleeve, a cylinder cover, a piston, a fuel tank, a liquid ammonia storage tank, a high-pressure common rail pipe and a liquid ammonia common rail pipe, wherein the cylinder sleeve, the cylinder cover and the piston form a combustion chamber, a main oil injector, an auxiliary oil injector, an air inlet valve and an air outlet valve are arranged on the cylinder cover, the combustion chamber is connected with an air inlet channel through the air inlet valve, the combustion chamber is connected with the air outlet channel through the air outlet valve, a liquid ammonia injection valve is arranged in the air inlet channel, the fuel tank is connected with the high-pressure common rail pipe through a low-pressure oil supply pump, a first pressure relief valve and a high-pressure oil pump, the high-pressure common rail pipe is respectively connected with the main oil injector and the auxiliary oil injector, the liquid ammonia storage tank is connected with the liquid ammonia common rail pipe through a pressure relief valve and a flowmeter, and the liquid ammonia common rail pipe is connected with the liquid ammonia injection valve. The invention organizes the mixed gas to form reasonable active concentration gradient layering, and ensures the reliable ignition and stable combustion of the dual-fuel engine under each load working condition, thereby improving the power performance and the emission performance of the dual-fuel engine.

Description

Multi-point low-pressure injection ammonia and diesel dual-fuel engine and combustion organization method
Technical Field
The invention relates to a dual-fuel engine, in particular to a dual-fuel engine and a combustion organization method thereof.
Background
The ammonia gas has high energy density, easy liquefaction and good antiknock performance, and is completely combusted to only produce clean and pollution-free water and nitrogen, thus being an ideal carbon-free alternative fuel. However, ammonia has the problems of low flame speed, high ignition point, high minimum ignition energy and the like, and diesel oil is used as an ignition agent and a combustion improver of ammonia fuel, so that the flame propagation speed of the ammonia can be effectively improved, the combustion duration is shortened, and the combustion efficiency and the emission performance of an engine are improved.
For a diesel/ammonia dual-fuel engine, the problems of large diesel injection proportion, low ammonia substitution rate and high escape rate exist under the medium-low load working condition, and the problems of poor flame stability, easy knocking and high NOx emission exist under the high load working condition. In order to ensure that the diesel/ammonia dual-fuel engine keeps good dynamic property and economy under various working conditions, a reasonable dual-fuel combustion system and a reasonable combustion method need to be constructed. The ignition diesel oil in the diesel oil/ammonia dual-fuel engine is ignited simultaneously in a plurality of points, and the distribution state of the diesel oil and the ammonia in the cylinder has important influence on the whole ignition stage, the combustion process and even the subsequent emission, so that different mixed fuel gas distribution effects can be formed in the cylinder by changing the air inlet condition and the injection strategy (fuel injection quantity, injection times and injection angles) according to different operation conditions, and the control optimization of the combustion and emission performance of the dual-fuel engine is realized.
On a diesel oil/ammonia dual-fuel engine oil gas injection control device, publication No. CN113202637A provides a liquid ammonia-diesel oil dual-fuel injection device, liquid ammonia is connected with a liquid ammonia injector through a high-pressure ammonia pipe, and the liquid ammonia injector is connected with a liquid ammonia storage tank through an ammonia return pipe, so that parallel injection of liquid ammonia and diesel oil is realized. Publication number CN113202638A provides a liquid ammonia-diesel dual fuel supply system, installs low-pressure pump, high-pressure pump, temperature controller on the outlet line of liquid ammonia holding vessel, realizes the high-low pressure injection of liquid ammonia. However, none of the above patents relates to the realization of organizing the mixture concentration layering state by optimizing the ammonia/diesel dual fuel injection strategy to match the combustion system structure, thereby achieving the purpose of improving the stable ignition and the reliable combustion of the mixture in the cylinder.
Disclosure of Invention
The invention aims to provide a multi-point low-pressure injection ammonia and diesel dual-fuel engine and a combustion organization method which can meet the requirements of power performance, economic performance and emission performance of the engine under different loads.
The purpose of the invention is realized in the following way:
the invention relates to a multi-point low-pressure injection ammonia and diesel dual-fuel engine, which is characterized in that: including cylinder jacket, cylinder head, piston, fuel tank, liquid ammonia holding vessel, high pressure common rail pipe, liquid ammonia common rail pipe, the cylinder jacket, cylinder head and piston form the combustion chamber, set up main fuel injector on the cylinder head, vice fuel injector, the admission valve, discharge valve, the combustion chamber passes through the admission valve and connects the intake duct, the combustion chamber passes through discharge valve and connects the exhaust duct, install the liquid ammonia injection valve in the intake duct, the fuel tank passes through low pressure fuel feed pump, first relief valve, high pressure oil pump connects high pressure common rail pipe, main fuel injector and vice fuel injector are connected respectively to high pressure common rail pipe, the liquid ammonia common rail pipe is connected through the relief valve, the flowmeter, liquid ammonia common rail pipe connection liquid ammonia injection valve.
The multi-point low-pressure injection ammonia and diesel dual-fuel engine of the invention can also comprise:
1. the high-pressure common rail pipe is connected with the fuel tank through a second relief valve.
2. The liquid ammonia injection valve is obliquely arranged on the air inlet channel, and the included angle between the central axis of the liquid ammonia injection valve and the central axis of the air inlet channel is 30-60 degrees.
3. The main oil sprayer is vertically arranged in the cylinder cover, the central axis of the main oil sprayer coincides with the axis of the cylinder, the auxiliary oil sprayer is obliquely arranged in the cylinder cover, and the inclined included angle between the central axis of the auxiliary oil sprayer and the axis of the cylinder is 15-35 degrees.
4. The main oil injector is a large-flow porous oil injector, the spray holes are uniformly distributed on the oil injector, the auxiliary oil injector is a small-flow porous oil injector, the spray holes are intensively distributed on one side surface of the oil injector, which is close to the axis of the cylinder, and the spray flow of the auxiliary oil injector is 5-10% of the spray flow of the main oil injector under the same spray pulse width.
5. The top of the combustion chamber is round; the piston is deep omega-shaped, the pit at the top of the piston is deep, and the caliber of the piston is contracted.
6. The air inlet is a tangential air inlet, the inclined included angle between the central line of the air passage near the air inlet valve and the axis of the air cylinder is 10-25 degrees, and the ammonia mixed gas in the air inlet enters along the circumferential tangential direction of the air cylinder and collides and separates with the air valve and the air cylinder wall, so that large-scale rolling flow and small-scale vortex flow are formed in the air cylinder, and the formation of the mixed gas is further promoted through the synergistic mixing effect of the air inlet rolling flow and the air inlet vortex flow on ammonia and air.
The invention relates to a method for organizing the combustion of a multi-point low-pressure injection ammonia and diesel dual-fuel engine, which is characterized by comprising the following steps: in the stage of the air intake stroke, the liquid ammonia injection valve injects liquid ammonia at low pressure along the central axis to the inner wall of the air inlet channel, a free jet flow area, an impact coanda area and a reflection jet flow area are constructed in the air inlet channel, the free jet flow area is an area in which the liquid ammonia is sprayed from the spray hole to the impact coanda, and in the free jet flow area, the liquid ammonia jet flow is wedge-shaped along the injection axis; the collision coanda area is an area formed by collision contact of liquid ammonia and the wall surface of the air inlet passage, in the collision coanda area, liquid ammonia jet flow collides with the wall surface to accelerate crushing, part of liquid ammonia is gasified and flows along the wall surface, and an adhesive vortex structure is continuously formed; the reflection jet flow area is an area formed by reflecting liquid ammonia from a wall back to the air inlet channel, in the reflection jet flow area, the liquid ammonia jet flow is continuously sucked into the air under the dominant action of air flow, and the gasification, diffusion and entrainment processes of the liquid ammonia are enhanced through the synergistic action of the collision wall, the adherence and the reflection flow of the liquid ammonia jet flow, so that the mixing rate of the ammonia and the air is improved.
The method for organizing the combustion of the multi-point low-pressure injection ammonia and diesel dual-fuel engine also comprises the following steps:
1. when the engine is in a stable working state, the liquid ammonia injection valve is controlled to inject liquid ammonia into the air inlet channel once after the exhaust valve is closed, and when the engine is in a transient acceleration non-stable working state, the liquid ammonia injection valve is controlled to inject liquid ammonia into the air inlet channel twice after the exhaust valve is closed, uniform lean mixture is formed in the cylinder after the liquid ammonia injected for the first time is premixed with air, and the liquid ammonia injected for the second time is premixed with air and then is intensively distributed on the upper layer of the combustion chamber to form the concentration distribution of the ammonia mixture with upper concentration and lower lean concentration.
2. When the engine is in a starting, idling and low-load working condition, a diesel oil working mode is adopted, a liquid ammonia injection valve does not perform fuel injection, air enters an air cylinder in a time range from an opening to a closing of an air inlet valve, a main fuel injector and an auxiliary fuel injector are controlled to simultaneously inject diesel oil for compression ignition, the injection timing is in a later stage of a compression stroke, an auxiliary fuel injection mist beam penetrates through a gap between the main fuel injection mist beam and the auxiliary fuel injection mist, interference between the main fuel injection mist and the spot is avoided, balance of NOx and the spot is realized, vortex flow and extrusion flow generated by the mist beam and the ascending of a deep omega-shaped necking piston are interacted, the oil-gas mixture is accelerated, the combustion duration is shortened, and the engine is enabled to run softly under the low-speed low-load working condition;
(2) When the engine is in a medium load working condition, a dual-fuel working mode is adopted, the main fuel injector does not perform fuel injection, the auxiliary fuel injector and the liquid ammonia injection valve work together, the liquid ammonia injection valve adopts a multi-point injection mode to inject liquid ammonia into an air inlet channel at low pressure and pre-mix with fresh air, mixed gas enters an air cylinder in a time range from an opening to a closing of an air inlet valve, firstly, homogeneous mixed gas is formed in the air cylinder, the auxiliary fuel injector adopts two injections, the first injection time is in a compression stroke middle period, diesel oil spray is mixed with in-cylinder ammonia pre-mixed gas, a preliminary low-temperature cracking reaction occurs under the action of in-cylinder temperature to generate high-activity free radicals, the second injection time is in the compression stroke near an upper dead center, air inlet rolling flow and vortex flow are quickly crushed into micro-vortex by the upward extrusion of a piston, the mixed gas in the air cylinder is promoted to form obvious reactive layering and concentration layering, the diesel oil injected for the second time further improves the reactive activity of the in-cylinder mixed gas, and when the temperature, pressure and equivalent ratio reach a firing point, the high-activity area at the top of a piston pit fires first, stable combustion of diesel oil spray and ammonia fuel is realized;
(3) When the engine is in a high-load working condition, a dual-fuel working mode is adopted, the main fuel injector does not perform fuel injection, the auxiliary fuel injector and the liquid ammonia injection valve work together, liquid ammonia is injected into the air inlet channel by the injection valve in a multi-point injection mode under low pressure and premixed in fresh air, mixed gas enters the air cylinder in the time range of opening and closing the air inlet valve, homogeneous mixed gas is formed in the air cylinder, the auxiliary fuel injector adopts a single injection mode, the injection timing is that the compression stroke moves to the vicinity of the top dead center, the extrusion flow generated by the upward movement of the deep omega-shaped piston promotes the ammonia premixed gas to be concentrated to the center position of the combustion chamber, the compression stroke is continued, when the temperature, the pressure and the equivalence ratio reach the ignition point, diesel oil spray spontaneously ignites in a multi-point near the top dead center area at first, and then the ammonia fuel is ignited, and stable ignition and combustion of the combustible mixed gas are realized.
The invention has the advantages that: according to the invention, by adopting a multi-point injection mode, the accurate control of the air inlet process of each cylinder is realized, so that the combustion uniformity of each cylinder is more excellent; the main fuel injector and the auxiliary fuel injector with different flow characteristics are adopted to spray the fuel bundles into the combustion chamber, and the fuel bundles are cooperated with the deep omega-shaped piston and the air inlet tumble to strengthen the extrusion vortex near the piston pit, so that the rapid and uniform mixing of the fuel spray and the ammonia premixed gas is realized; by reasonably matching the combustion modes and the fuel injection strategies of the ammonia/diesel dual-fuel engine under different load working conditions, reasonable layering of the mixed gas in the cylinder is realized, stable ignition of the engine is ensured, the flame propagation speed and combustion stability of ammonia fuel are improved, and the problems that the diesel/ammonia dual-fuel engine is difficult to start under medium and low load working conditions, the ammonia escape amount is large and the NOx emission is high under high load working conditions are solved.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic diagram of liquid ammonia injection;
FIG. 3 is a schematic diagram of intake swirl and tumble flow;
FIG. 4 is a low load operating mode diesel injection schematic;
FIG. 5 is a top view of the low load condition beam distribution;
FIG. 6 is a schematic diagram of the oil and gas distribution of the secondary injector in the medium load condition during the first injection;
FIG. 7 is a schematic diagram of oil and gas distribution during secondary injection of a secondary injector under medium load conditions;
FIG. 8 is a graph of the two unequal injection rate laws of a secondary fuel injector under medium load conditions;
FIG. 9 is a schematic diagram of oil and gas distribution during injection of a secondary injector under high load conditions;
FIG. 10 is a graph of the high load operating mode liquid ammonia and diesel injection rate law.
Detailed Description
The invention is described in more detail below, by way of example, with reference to the accompanying drawings:
referring to fig. 1-10, a specific layout diagram of the dual fuel engine system of the invention is shown in fig. 1, and mainly comprises: a liquid ammonia storage tank 1, a pressure reducing valve 2, a flow meter 3, a liquid ammonia common rail pipe 4, a liquid ammonia injection valve 5, an air inlet 6, an air inlet valve 7, a main fuel injector 8, a sub fuel injector 9, a combustion chamber 10, a piston 11, a cylinder liner 12, a cylinder head 13, a fuel tank 14, a low pressure fuel feed pump 15, a filter 16, a high pressure fuel pump 17, a pressure reducing valve 18, a high pressure common rail pipe 19, a rail pressure sensor 20, an ECU21 and the like; the liquid ammonia injection valve 5 is obliquely arranged on the air inlet channel 6, and the included angle between the central axis of the liquid ammonia injection valve 5 and the central axis of the air inlet channel 6 is 30-60 degrees; the main fuel injector 8 is vertically arranged in the cylinder cover 13, the central axis of the main fuel injector 8 coincides with the axis of the cylinder, the auxiliary fuel injector 9 is obliquely arranged in the cylinder cover 13, the inclined included angle between the central axis of the auxiliary fuel injector 9 and the axis of the cylinder is 15-35 degrees, the main fuel injector 8 is a large-flow porous fuel injector, spray holes are uniformly distributed on a fuel injector nozzle, the auxiliary fuel injector 9 is a small-flow porous fuel injector, the spray holes are intensively distributed on one side surface of the fuel injector, which is close to the axis of the cylinder, of the fuel injector, and the spray flow of the auxiliary fuel injector 13 is 5-10% of the spray flow of the main fuel injector 15 under the same spray pulse width; the top of the combustion chamber 10 is round; the piston 11 is deep omega-shaped, the pit at the top of the piston is deep, and the caliber is contracted; the adopted ammonia/diesel dual-fuel engine is a four-stroke engine, and the working cycle comprises an air inlet stroke, a compression stroke, a combustion power stroke and an exhaust stroke; the fuel in the fuel tank 14 is sucked out by the low-pressure fuel supply pump 15 and is conveyed to the high-pressure fuel pump 17, the high-pressure fuel pump 17 pressurizes the fuel, the fuel is pressurized into high-pressure fuel and is supplied to the high-pressure common rail pipe 19, the ecu21 adjusts rail pressure according to the feedback signal of the rail pressure sensor 20, if the rail pressure is too high, the pressure release valve 18 is opened, part of the high-pressure fuel flows back to the fuel tank, and the common rail pressure is reduced; the ECU21 controls the liquid ammonia injection strategy to be matched and cooperated with the fuel injection strategy according to the operation condition of the engine, and controls the formation and the combustion process of the mixed gas in the cylinder.
In the stage of the air intake stroke, the liquid ammonia injection valve injects liquid ammonia to the inner wall of the air inlet channel at low pressure along the central axis, so as to construct a free jet flow area, an impact coanda area and a reflection jet flow area in the air inlet channel in the liquid ammonia injection process, wherein the jet flow movement is shown in the attached wall area in the figure 2, the free jet flow area is the area in which liquid ammonia is sprayed from the spray hole to the impact coanda, and in the free jet flow area, the liquid ammonia jet flow is wedge-shaped along the injection axis; the collision coanda area is an area formed by collision contact of liquid ammonia and the wall surface of the air inlet passage, in the collision coanda area, liquid ammonia jet flow collides with the wall surface to accelerate crushing, part of liquid ammonia is gasified and flows along the wall surface, and an adhesive vortex structure is continuously formed; the reflection jet flow area is an area formed by reflecting liquid ammonia from a wall back to the air inlet channel, in the reflection jet flow area, the liquid ammonia jet flow is continuously sucked into the air under the dominant action of air flow, and the gasification, diffusion and entrainment processes of the liquid ammonia are enhanced through the synergistic action of the collision wall, the adherence and the reflection flow of the liquid ammonia jet flow, so that the mixing rate of the ammonia and the air is improved.
The air inlet is a tangential air inlet, the inclined included angle between the central line of the air passage near the air inlet valve and the axis of the air cylinder is 10-25 degrees, and under the guiding action of the tangential air inlet and the dome-shaped combustion chamber, the ammonia mixed gas in the air inlet enters the air cylinder along the circumferential tangential direction of the air cylinder and collides and separates with the air valve and the air cylinder wall, large-scale rolling flow and small-scale vortex flow are formed in the air cylinder, and the formed airflow motion is shown in the figure 3, and the formation of the mixed gas is further promoted through the synergistic mixing action of the air inlet rolling flow and the air inlet vortex flow on ammonia and air.
When the engine is in a stable working state, the liquid ammonia injection valve is controlled to inject liquid ammonia into the air inlet channel once after the exhaust valve is closed, when the engine is in an unstable working state of transient acceleration, the liquid ammonia injection valve is controlled to inject liquid ammonia into the air inlet channel twice after the exhaust valve is closed, uniform lean mixture is formed in the cylinder after the liquid ammonia injected for the first time is premixed with air, the liquid ammonia injected for the second time is premixed with air and then is intensively distributed on the upper layer of the combustion chamber, so that the concentration distribution of the ammonia mixture with high concentration and low concentration is formed, the combustion duration is shortened, and the acceleration sensitivity of the engine is improved.
The method for organizing the combustion of the multi-point low-pressure injection ammonia/diesel dual-fuel engine comprises the following steps: through the collaborative optimization control of the injection timing, injection quantity and injection rule of the liquid ammonia injection valve, the main fuel injector and the auxiliary fuel injector, the flexible switching of the pure diesel mode and the dual fuel mode under different working conditions is realized, the gradient coupling layering of the concentration of the high-low reactive fuel is realized, and the combustion process of the mixed gas is controlled.
The specific control process is as follows:
(1) When the engine is in the working condition of starting, idling and low load, the ammonia/diesel dual-fuel engine adopts a diesel working mode, the liquid ammonia injection valve does not perform fuel injection, air enters the cylinder in the time range from the opening to the closing of the air inlet valve, in order to avoid carbon smoke blocking the spray holes of the auxiliary fuel injector, the ECU controls the main fuel injector and the auxiliary fuel injector to simultaneously inject diesel to perform compression ignition work, the injection timing is the later stage of a compression stroke, at the moment, the distribution state of diesel mist bundles injected by the main fuel injector and the auxiliary fuel injector is as shown in the attached drawings 4 and 5, the auxiliary diesel mist bundles penetrate through the gaps of the main diesel mist bundles, the interference between the main diesel mist bundles and the auxiliary diesel mist bundles is avoided, and the balance of NOx and the spot is realized.
(2) When the engine is in a medium load working condition, the ammonia/diesel dual-fuel engine adopts a dual-fuel working mode, the main fuel injector does not perform fuel injection, the auxiliary fuel injector and the liquid ammonia injection valve work together, the liquid ammonia injection valve adopts a multi-point injection mode to inject liquid ammonia into the air inlet channel at low pressure and pre-mix with fresh air, mixed gas enters the air cylinder in a time range from opening to closing of the air inlet valve, firstly, homogeneous mixed gas is formed in the air cylinder, the auxiliary fuel injector adopts two injections, the first injection timing is the middle stage of a compression stroke, diesel spray is mixed with in-cylinder ammonia pre-mixed gas, a preliminary low-temperature cracking reaction occurs under the action of in-cylinder temperature, high-activity free radicals with a certain concentration are generated, ammonia reaction activity and combustion speed are improved, at the moment, in-cylinder oil gas distribution is shown in an attached chart 6, the second injection timing is the compression stroke is near the top dead center, the air inlet rolling flow and vortex are quickly crushed into micro-vortex by upward extrusion of a piston, the in-cylinder mixed gas is promoted to form obvious reactive activity layers and concentration layers, at the moment, the in-cylinder distribution is shown in an attached chart 7, the diesel oil injection rate curve is shown in an attached chart, the figure 8, diesel fuel injection for the second injection can further improve the internal mixed gas and the reactive gas and the combustion activity and the pressure and the combustion efficiency reach the ignition stability when the ignition temperature reaches the top of the ignition point of the combustion area.
(3) When the engine is in a high-load working condition, the ammonia/diesel dual-fuel engine adopts a dual-fuel working mode, the main fuel injector does not perform fuel injection, the auxiliary fuel injector and the liquid ammonia injection valve work together, liquid ammonia is injected into the air inlet channel by the injection valve in a multi-point injection mode, and premixed in fresh air, mixed gas enters the cylinder in the time range of opening and closing of the air inlet valve, homogeneous mixed gas is formed in the cylinder, the auxiliary fuel injector adopts a single injection mode, the injection timing is that the compression stroke moves to the vicinity of the top dead center, the extrusion flow generated by the upward movement of the deep omega-shaped piston promotes the ammonia premixed gas to be concentrated to the center position of the combustion chamber, at the moment, the oil gas distribution in the cylinder is shown in an attached drawing 9, the injection rate curve of the liquid ammonia and the diesel oil is shown in an attached drawing 10, the compression stroke continues, and when the temperature, the pressure and the equivalence ratio reach the ignition point, the diesel spray can spontaneously ignite in a multi-point in the vicinity of the high-activity area at first, and the ignition of the high-activity area, so that the ammonia fuel is ignited, and stable ignition and combustion of the combustible mixed gas is realized.

Claims (10)

1. The multi-point low-pressure injection ammonia and diesel dual-fuel engine is characterized in that: including cylinder jacket, cylinder head, piston, fuel tank, liquid ammonia holding vessel, high pressure common rail pipe, liquid ammonia common rail pipe, the cylinder jacket, cylinder head and piston form the combustion chamber, set up main fuel injector on the cylinder head, vice fuel injector, the admission valve, discharge valve, the combustion chamber passes through the admission valve and connects the intake duct, the combustion chamber passes through discharge valve and connects the exhaust duct, install the liquid ammonia injection valve in the intake duct, the fuel tank passes through low pressure fuel feed pump, first relief valve, high pressure oil pump connects high pressure common rail pipe, main fuel injector and vice fuel injector are connected respectively to high pressure common rail pipe, the liquid ammonia common rail pipe is connected through the relief valve, the flowmeter, liquid ammonia common rail pipe connection liquid ammonia injection valve.
2. The multi-point low pressure injection ammonia, diesel dual fuel engine of claim 1, characterized by: the high-pressure common rail pipe is connected with the fuel tank through a second relief valve.
3. The multi-point low pressure injection ammonia, diesel dual fuel engine of claim 1, characterized by: the liquid ammonia injection valve is obliquely arranged on the air inlet channel, and the included angle between the central axis of the liquid ammonia injection valve and the central axis of the air inlet channel is 30-60 degrees.
4. The multi-point low pressure injection ammonia, diesel dual fuel engine of claim 1, characterized by: the main oil sprayer is vertically arranged in the cylinder cover, the central axis of the main oil sprayer coincides with the axis of the cylinder, the auxiliary oil sprayer is obliquely arranged in the cylinder cover, and the inclined included angle between the central axis of the auxiliary oil sprayer and the axis of the cylinder is 15-35 degrees.
5. The multi-point low pressure injection ammonia, diesel dual fuel engine of claim 1, characterized by: the main oil injector is a large-flow porous oil injector, the spray holes are uniformly distributed on the oil injector, the auxiliary oil injector is a small-flow porous oil injector, the spray holes are intensively distributed on one side surface of the oil injector, which is close to the axis of the cylinder, and the spray flow of the auxiliary oil injector is 5-10% of the spray flow of the main oil injector under the same spray pulse width.
6. The multi-point low pressure injection ammonia, diesel dual fuel engine of claim 1, characterized by: the top of the combustion chamber is round; the piston is deep omega-shaped, the pit at the top of the piston is deep, and the caliber of the piston is contracted.
7. The multi-point low pressure injection ammonia, diesel dual fuel engine of claim 1, characterized by: the air inlet is a tangential air inlet, the inclined included angle between the central line of the air passage near the air inlet valve and the axis of the air cylinder is 10-25 degrees, and the ammonia mixed gas in the air inlet enters along the circumferential tangential direction of the air cylinder and collides and separates with the air valve and the air cylinder wall, so that large-scale rolling flow and small-scale vortex flow are formed in the air cylinder, and the formation of the mixed gas is further promoted through the synergistic mixing effect of the air inlet rolling flow and the air inlet vortex flow on ammonia and air.
8. The method for organizing the combustion of the multi-point low-pressure injection ammonia and diesel dual-fuel engine is characterized by comprising the following steps of: in the stage of the air intake stroke, the liquid ammonia injection valve injects liquid ammonia at low pressure along the central axis to the inner wall of the air inlet channel, a free jet flow area, an impact coanda area and a reflection jet flow area are constructed in the air inlet channel, the free jet flow area is an area in which the liquid ammonia is sprayed from the spray hole to the impact coanda, and in the free jet flow area, the liquid ammonia jet flow is wedge-shaped along the injection axis; the collision coanda area is an area formed by collision contact of liquid ammonia and the wall surface of the air inlet passage, in the collision coanda area, liquid ammonia jet flow collides with the wall surface to accelerate crushing, part of liquid ammonia is gasified and flows along the wall surface, and an adhesive vortex structure is continuously formed; the reflection jet flow area is an area formed by reflecting liquid ammonia from a wall back to the air inlet channel, in the reflection jet flow area, the liquid ammonia jet flow is continuously sucked into the air under the dominant action of air flow, and the gasification, diffusion and entrainment processes of the liquid ammonia are enhanced through the synergistic action of the collision wall, the adherence and the reflection flow of the liquid ammonia jet flow, so that the mixing rate of the ammonia and the air is improved.
9. The multi-point low-pressure injection ammonia, diesel dual-fuel engine combustion organization method of claim 8, characterized by: when the engine is in a stable working state, the liquid ammonia injection valve is controlled to inject liquid ammonia into the air inlet channel once after the exhaust valve is closed, and when the engine is in a transient acceleration non-stable working state, the liquid ammonia injection valve is controlled to inject liquid ammonia into the air inlet channel twice after the exhaust valve is closed, uniform lean mixture is formed in the cylinder after the liquid ammonia injected for the first time is premixed with air, and the liquid ammonia injected for the second time is premixed with air and then is intensively distributed on the upper layer of the combustion chamber to form the concentration distribution of the ammonia mixture with upper concentration and lower lean concentration.
10. The multi-point low-pressure injection ammonia, diesel dual-fuel engine combustion organization method of claim 8, characterized by:
(1) When the engine is in a starting, idling and low-load working condition, a diesel oil working mode is adopted, a liquid ammonia injection valve does not perform fuel injection, air enters the cylinder in the time range from the opening to the closing of an intake valve, a main fuel injector and an auxiliary fuel injector are controlled to simultaneously inject diesel oil for ignition, the injection timing is the later stage of a compression stroke, an auxiliary fuel injection mist beam penetrates through a gap of the main fuel injection mist beam, interference between the main fuel injection mist and the auxiliary fuel injection mist is avoided, the balance of NOx and a spot is realized, vortex and squeeze flow generated by the ascending of the mist beam and a deep omega-shaped necking piston are interacted, the oil-gas mixing is accelerated, the combustion duration is reduced, and the engine is enabled to run softly under the low-speed low-load working condition;
(2) When the engine is in a medium load working condition, a dual-fuel working mode is adopted, the main fuel injector does not perform fuel injection, the auxiliary fuel injector and the liquid ammonia injection valve work together, the liquid ammonia injection valve adopts a multi-point injection mode to inject liquid ammonia into an air inlet channel at low pressure and pre-mix with fresh air, mixed gas enters an air cylinder in a time range from an opening to a closing of an air inlet valve, firstly, homogeneous mixed gas is formed in the air cylinder, the auxiliary fuel injector adopts two injections, the first injection time is in a compression stroke middle period, diesel oil spray is mixed with in-cylinder ammonia pre-mixed gas, a preliminary low-temperature cracking reaction occurs under the action of in-cylinder temperature to generate high-activity free radicals, the second injection time is in the compression stroke near an upper dead center, air inlet rolling flow and vortex flow are quickly crushed into micro-vortex by the upward extrusion of a piston, the mixed gas in the air cylinder is promoted to form obvious reactive layering and concentration layering, the diesel oil injected for the second time further improves the reactive activity of the in-cylinder mixed gas, and when the temperature, pressure and equivalent ratio reach a firing point, the high-activity area at the top of a piston pit fires first, stable combustion of diesel oil spray and ammonia fuel is realized;
(3) When the engine is in a high-load working condition, a dual-fuel working mode is adopted, the main fuel injector does not perform fuel injection, the auxiliary fuel injector and the liquid ammonia injection valve work together, liquid ammonia is injected into the air inlet channel by the injection valve in a multi-point injection mode under low pressure and premixed in fresh air, mixed gas enters the air cylinder in the time range of opening and closing the air inlet valve, homogeneous mixed gas is formed in the air cylinder, the auxiliary fuel injector adopts a single injection mode, the injection timing is that the compression stroke moves to the vicinity of the top dead center, the extrusion flow generated by the upward movement of the deep omega-shaped piston promotes the ammonia premixed gas to be concentrated to the center position of the combustion chamber, the compression stroke is continued, when the temperature, the pressure and the equivalence ratio reach the ignition point, diesel oil spray spontaneously ignites in a multi-point near the top dead center area at first, and then the ammonia fuel is ignited, and stable ignition and combustion of the combustible mixed gas are realized.
CN202310091070.1A 2023-02-09 2023-02-09 Multi-point low-pressure injection ammonia and diesel dual-fuel engine and combustion organization method Pending CN116291907A (en)

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