WO2011130792A1 - A dual fuel supply system for a direct-injection system of a diesel engine with off-board mixing - Google Patents

A dual fuel supply system for a direct-injection system of a diesel engine with off-board mixing Download PDF

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Publication number
WO2011130792A1
WO2011130792A1 PCT/AU2011/000456 AU2011000456W WO2011130792A1 WO 2011130792 A1 WO2011130792 A1 WO 2011130792A1 AU 2011000456 W AU2011000456 W AU 2011000456W WO 2011130792 A1 WO2011130792 A1 WO 2011130792A1
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WO
WIPO (PCT)
Prior art keywords
fuel
supply system
diesel
supply
fuel supply
Prior art date
Application number
PCT/AU2011/000456
Other languages
French (fr)
Inventor
Ewe Krug
Original Assignee
Dgc Industries Pty Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2010901653A external-priority patent/AU2010901653A0/en
Application filed by Dgc Industries Pty Ltd filed Critical Dgc Industries Pty Ltd
Publication of WO2011130792A1 publication Critical patent/WO2011130792A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M37/00—Apparatus or systems for feeding liquid fuel from storage containers to carburettors or fuel-injection apparatus; Arrangements for purifying liquid fuel specially adapted for, or arranged on, internal-combustion engines
    • F02M37/0076—Details of the fuel feeding system related to the fuel tank
    • F02M37/0088—Multiple separate fuel tanks or tanks being at least partially partitioned
    • 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
    • F02D19/0605—Control of components of the fuel supply system to adjust the fuel pressure or temperature
    • 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
    • F02D19/0647—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 liquefied petroleum gas [LPG], liquefied natural gas [LNG], compressed natural gas [CNG] or dimethyl ether [DME]
    • 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
    • F02D19/0684—High pressure fuel injection systems; Details on pumps, rails or the arrangement of valves in the fuel supply and return systems
    • 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
    • F02D19/0694—Injectors operating with a plurality of 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
    • F02D19/08—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
    • 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
    • F02D19/082—Premixed fuels, i.e. emulsions or blends
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M43/00—Fuel-injection apparatus operating simultaneously on two or more fuels, or on a liquid fuel and another liquid, e.g. the other liquid being an anti-knock additive
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/02—Fuel-injection apparatus having several injectors fed by a common pumping element, or having several pumping elements feeding a common injector; Fuel-injection apparatus having provisions for cutting-out pumps, pumping elements, or injectors; Fuel-injection apparatus having provisions for variably interconnecting pumping elements and injectors alternatively
    • F02M63/0225—Fuel-injection apparatus having a common rail feeding several injectors ; Means for varying pressure in common rails; Pumps feeding common rails
    • 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

Definitions

  • the present invention relates to fuel systems for diesel engines.
  • the invention relates to a dual fuel supply system for a diesel engine having a direct- injection system.
  • the invention extends to a diesel engine incorporating the dual fuel supply system and to a vehicle that incorporates a diesel engine having the dual fuel supply system.
  • This invention relates particularly but not exclusively to a dual fuel supply system for diesel engines of trucks. It will therefore be convenient hereinafter to describe the invention with reference to this example application. However, at the same time it must be recognized that the invention applies to other applications such as to diesel engines for light vehicles and to other types of internal combustion engines.
  • Dual fuel supply systems for supplying a fuel mixture of diesel and gaseous fuel to diesel engines are known. Some dual fuel supply systems introduce the gaseous fuel into the air supply that leads to the combustion chamber. In US2005202021 a separate set of injectors introduce gaseous LPG into the combustion chamber, whereas in US5408957, US4520766, JP1318755 and GB1252458, gaseous LPG is mixed with air prior to introducing the air mixture to the combustion chamber.
  • LPG and diesel at the same time has recently been addressed by the dual fuel system disclosed in WO 2008036999 where liquid LPG and diesel were mixed in a chamber prior to being introduced into the combustion chambers.
  • problems associated with the dual fuel system disclosed in WO 2008036999 in its application with different engine types.
  • the invention provides a dual fuel supply system for supplying fuel to a direct-injection system of a diesel engine, the dual fuel supply system including:
  • a diesel supply system to supply diesel to the direct-injection system; and a mixed fuel supply system that is operatively able to supply a liquid fuel premixture of diesel and liquefied gaseous fuel to the direct-injection system at a supply pressure within a fuel demand pressure range of the direct-injection system and at a corresponding temperature range that retains the fuel premixture below its vapor temperature as it flows through the fuel path of the direct-injection system and the diesel engine, in which the dual fuel supply system is configured to permit selective change over between the diesel supply system and the mixed fuel system to supply the direct-injection system selectively with either diesel or liquid fuel premixture respectively; said liquid fuel premixture is supplied to the dual fuel system as an off-board fuel premixture.
  • the fuel premixture is mixed off board and is preferably stored in a tank or reservoir prior to use by the dual fuel system.
  • the diesel supply system is preferably operatively able to supply diesel to the direct-injection system at a supply pressure within the fuel demand pressure range of the direct-injection system and at a supply temperature range that corresponds with the supply temperature range of the mixed fuel supply system.
  • the mixed fuel supply system is preferably configured to regulate the supply pressure of the liquid fuel premixture within a pressure range towards a high end of the fuel demand pressure of the direct-injection system.
  • the mixed fuel supply system is preferably configured to supply the fuel premixture at a supply temperature that is sufficiently lower than the vapor temperature of the liquid fuel premixture at the supply pressure to compensate for heat that is introduced into the liquid fuel premixture by engine heat as it flows , through the fuel path of the direct-injection system and the diesel engine.
  • the mixed fuel supply system preferably includes a first stage and a second stage, and in which the second stage of the mixed fuel supply system is configured to regulate the supply pressure and the supply temperature at which the liquid fuel premixture is supplied to the direct-injection system.
  • the mixed fuel supply system is preferably configured to trigger the first stage of the mixed fuel supply system to supply liquid fuel premixture to the second stage of the mixed fuel supply system when the supply pressure in the second stage of the mixed fuel supply system drops towards a low end of the fuel demand pressure range of the direct-injection system.
  • the mixed fuel supply system preferably includes a pressure accumulator, and in which the first stage of the mixed fuel supply system is triggered to charge the pressure accumulator with fuel premixture when the supply pressure in the second stage of the mixed fuel supply system drops towards a low end of the fuel demand pressure of the direct-injection system.
  • the second stage of the mixed fuel supply system preferably includes a mixed fuel supply circulation line that defines a mixed fuel supply circulation flow path that is connected or connectable inline in flow circulation with a high pressure pump and a fuel rail of the direct-injection system.
  • An overflow line of the high pressure pump of the direct-injection system is preferably connected in flow communication with the mixed fuel circulation line.
  • the mixed fuel supply circulation line preferably defines a mixed fuel supply circulation flow path that has a flow path volume to accommodate at least the amount of liquid fuel premixture that the diesel engine consumes at full load for one minute.
  • the second stage of the mixed fuel supply system preferably includes a circulation pump inline the mixed fuel supply circulation line.
  • the circulation pump is preferably a variable speed controlled pump.
  • the second stage of the mixed fuel supply system preferably includes at least one fuel cooler inline the mixed fuel supply circulation line upstream of the direct- injection system and downstream of the mixed fuel pressure accumulator.
  • the at least one fuel cooler preferably includes an evaporator through which a refrigerant is passed, and a shut-off valve to shut-off the flow of refrigerant through the evaporator.
  • the second stage of the mixed fuel supply system preferably includes a temperature sensor upstream from the direct-injection system, to measure the supply temperature of the liquid fuel premixture that is supplied to the direct-injection system.
  • thermosensor downstream from the direct-injection system, to measure a temperature of the liquid fuel premixture that discharges from the direct-injection system into the mixed fuel supply circulation line.
  • the second stage of the mixed fuel supply system preferably includes a flow sensor to measure a flow rate of liquid fuel premixture circulating through the mixed fuel supply circulation line.
  • the mixed fuel pressure accumulator is preferably a bladder accumulator.
  • the second stage of the mixed fuel supply system preferably includes at least one pressure sensor upstream from the direct-injection system to measure the supply pressure of the liquid fuel premixture being supplied to the direct-injection system.
  • the second stage of the mixed fuel supply system preferably includes a mixed fuel supply line to connect the first stage of the mixed fuel supply system in flow communication with the second stage of the mixed fuel supply system, and in which the mixed fuel supply line joins the mixed fuel supply circulation line upstream from the circulation pump that is inline the mixed fuel supply circulation line.
  • the second stage of the mixed fuel supply system preferably includes a pressure regulating valve inline the mixed fuel supply line.
  • the first stage of the mixed fuel supply system is preferably a. fuel premix supply system that is configured to receive and store a fuel premixture of diesel and liquefied gaseous fuel and to supply the fuel premixture to the second stage of the mixed fuel supply system.
  • the fuel premix supply system preferably includes a fuel premix supply line that extends from a fuel premix supply reservoir to the fuel mixture supply line.
  • the fuel premix supply system preferably includes a filter inline the fuel premix supply line.
  • the fuel premix supply system preferably includes a fuel cooler inline the fuel premix supply line.
  • the fuel premix supply system preferably includes a premix booster pump for pumping the fuel premixture to the second stage of the mixed fuel supply system.
  • the fuel premix supply system preferably includes at least one temperature sensor upstream from the fuel cooler.
  • the fuel premix supply system preferably includes a diesel flush line extending from the diesel supply circulation line to the mixed fuel supply line.
  • the fuel premix supply system preferably includes a solenoid valve inline the diesel flush line.
  • the second stage of the mixed fuel supply system preferably includes a mixed fuel bypass line selectively to bypass the direct-injection system.
  • the diesel supply system preferably includes a diesel supply circulation line that is connected or connectable in flow communication inline with the fuel rail of the direct-injection system.
  • the diesel supply system preferably includes at least one fuel cooler inline the diesel supply circulation line upstream from the direct injection-system.
  • the diesel supply system preferably includes a diesel booster pump inline the diesel supply circulation line upstream from the at least one fuel cooler.
  • the diesel supply system preferably includes a diesel bypass selectively to bypass the direct-injection system.
  • the dual fuel supply system preferably includes a controller that is configured to control selectively the change over between the diesel supply system and the mixed fuel supply system.
  • the controller is preferably configured to flush the mixed fuel supply line with diesel before switching over from the mixed fuel supply system to the diesel system.
  • the controller is preferably configured to flush the mixed fuel supply line with diesel after the fuel premix supply system charged the second stage of the mixed fuel supply system with liquid fuel premixture.
  • the controller is preferably configured to flush the mixed fuel supply line with diesel before the diesel engine is stopped.
  • the controller is preferably configured to regulate the flow rate of the fuel premixture through the mixed fuel cooler to regulate the temperature of the fuel premixture.
  • the controller is preferably configured to open the diesel supply circulation line prior to opening the mixed fuel bypass line.
  • the controller is preferably configured to open the mixed fuel supply circulation line prior to opening the diesel bypass line.
  • the controller is preferably configured automatically to change over from the mixed fuel supply system to the diesel supply system when the pressure in the mixed fuel supply circulation loop drops below a set pressure threshold.
  • the controller is preferably configured to monitor the temperature of the liquid fuel premixture in the mixed fuel supply circulation line, and to switch over to the diesel supply system if the temperature rises above a set temperature threshold.
  • the controller is preferably configured to monitor the temperature in the mixed fuel bypass loop, and if the temperature of the liquid fuel premixture in the mixed fuel bypass loop is above a set temperature threshold then to resist switching over from the diesel supply system to the mixed fuel supply system.
  • the controller is preferably configured to monitor the supply temperature of the diesel, and if the supply temperature of the diesel is above a set temperature threshold then to resist change over to the mixed fuel supply system.
  • the controller is preferably configured to trigger an alarm if the flow rate of diesel in the diesel supply circulation line or the flow rate of fuel premixture in the mixed fuel circulation line is below a set flow rate threshold.
  • the dual supply system can be retrofitted as a kit to existing vehicles.
  • the invention provides a diesel engine that includes:
  • the dual fuel supply system preferably includes any one or more of the features described above in accordance with the first aspect of the invention.
  • the invention provides a vehicle that includes:
  • the dual fuel supply system preferably includes any one or more of the features described above in accordance with the first aspect of the invention.
  • FIG. 1 is a schematic functional block diagram of a dual fuel supply system, in accordance with the invention.
  • Figure 2 is a schematic representation of a first embodiment of the dual fuel supply system
  • Figure 3 is a schematic representation of a second embodiment of the dual fuel supply system the includes the first embodiment and additional system components;
  • Figure 4 is a schematic representation of a third embodiment of the dual fuel supply system.
  • Figure 5 is a schematic representation of a fourth embodiment of the dual fuel supply system that includes the third embodiment and additional system components.
  • reference numeral 10 generally indicates a dual fuel supply system in accordance with the invention for supplying fuel to a direct-injection system (the injection system) 12 of a diesel engine (not shown).
  • direct-injection system is meant to include a high pressure pump having a low pressure intake side and a high pressure outlet side that supplies fuel at a relative high pressure to a fuel rail which supplies the fuel to injectors.
  • the intake or low pressure side of a high pressure pump of a direct-injection system has an operative intake pressure of typically between 2 bar to 15 bar.
  • the intake pressure range of the high pressure pump is herein referred to as the fuel demand pressure range of the direct-injection system.
  • each of the embodiments described below includes two subsystems.
  • One sub-system is a mixed fuel supply system 17 that includes a first stage 14 of the mixed fuel supply system 17 having a fuel premix tank 44 for receiving and storing a liquid fuel premixture of diesel and liquefied gaseous fuel and system components 13 for supplying the liquid fuel premixture to the second stage 16 of the mixed fuel supply system 17.
  • Second stage 16 includes system components 15.
  • the liquid fuel premixture is typically a mixture of diesel and liquid petroleum gas (LPG), however, it will be appreciated that a dual fuel supply system, in accordance with the invention, can be configured for use with different types of fuel premixtures.
  • LPG liquid petroleum gas
  • the mixed fuel supply system 17 is operatively able to supply the liquid fuel premixture of diesel and liquefied gaseous fuel to the direct-injection system at a supply pressure range that matches the fuel demand pressure range of the injection system 12 and at a corresponding temperature range that retains the fuel premixture below its vapor temperature as it flows through the fuel path of the direct-injection system 12 and the diesel engine.
  • Another subsystem of the dual fuel supply system 10 is a diesel supply system 80 and includes the diesel tank 42 and system components 79 for delivering diesel to the injection system 12 and circulating diesel to the tank 42.
  • the dual fuel supply system 10 includes conduits or lines that define various flow paths, and system components that regulate and control the active flow paths, flow rates, temperature, and pressure of the diesel or fuel premixture through the dual fuel supply system 1 1 , as is explained in more detail below. Moreover, the dual fuel supply system 10 is configured to permit selective change over between the diesel supply system 80 and the mixed fuel system 17 to supply the injection system 12 selectively with either diesel or liquid fuel premixture respectively.
  • FIG 2 shows a schematic diagram of an embodiment 11 of the due-fuel supply system.
  • the dual fuel supply system 1 1 includes a mixed fuel supply system 17 that includes the first stage 14 for receiving and storing and supplying the second stage 16 with the fuel premixture.
  • the second stage 16 is for supplying the injection system 12 with the fuel premixture from the first stage 14 of the mixed fuel supply system 17.
  • the second stage 16 of the mixed fuel supply system 17 forms a fuel premix supply system.
  • the second stage 16 of the mixed fuel supply system 17 includes a mixed fuel supply circulation line or loop 18 that defines a mixed fuel supply circulation flow path (see arrow 20).
  • the mixed fuel supply circulation loop 18 js connected in flow communication inline with the high pressure pump 21 and fuel rail 23 that forms part of the injection system 2 for circulating fuel premixture through the fuel rail of the injection system 12.
  • a mixed fuel supply line 22 that defines a mixed fuel supply line flow path extends between the fuel premix supply system 14 and the mixed fuel supply circulation loop 18 to supply fuel premixture to the mixed fuel supply circulation loop 18 from the fuel premix supply system 14.
  • the second stage 16 of the mixed fuel supply system 17 includes a circulation pump 26 inline the mixed fuel supply circulation loop 18 and a fuel cooler 28 inline the mixed fuel supply circulation loop 18 upstream from the direct injection-system 12 and downstream from the circulation pump 26.
  • the circulation pump is a controllable variably speed pump and the fuel cooler includes an evaporator that is connected inline with the refrigerant line of the air conditioning system of the truck.
  • the fuel cooler can be a stand alone fuel cooler.
  • a temperature sensor 30 is provided upstream from the direct-injection system 12, to measure the supply temperature of the liquid fuel premixture that is supplied to the injection system 12.
  • the dual fuel supply system 11 also includes a mixed fuel bypass line 32 selectively to isolate the direct-injection system 12 from the mixed fuel supply circulation line 18 (see arrow 33).
  • Valves in the form of a controllable normally closed solenoid valve 35 and normally opened solenoid valve 34 are provided inline the mixed fuel circulation supply loop 18 and the bypass line 32 respectively, selectively to divert fuel premixture, through either flow path 20 or 33.
  • the second stage 16 of the mixed fuel supply system 17 also includes a pressure accumulator 36 inline the mixed fuel circulation supply loop 18 downstream from the direct-injection system 2 and upstream from the circulation pump 26.
  • the pressure accumulator 36 is in the form of a bladder accumulator.
  • the second stage 16 of the mixed fuel supply system 17 includes at least one pressure sensor 38 upstream from the direct-injection system 12 to measure the supply pressure of the liquid fuel premixture being supplied to the direct-injection system 12.
  • the fuel premix supply system 14 is configured to supply the liquid fuel premixture to the second stage 16 of the mixed fuel supply system 17.
  • the fuel premixture can have a ratio of between about 10% and 50% parts per mass diesel to between 90% and 50% parts per mass LPG.
  • the fuel premixture is supplied to the mixed fuel circulation supply loop 18 at a pressure of between 2.0bar and 15.0bar at a temperature of between 8.5°C and +55°C, depending on the intake pressure rating of .the high pressure pump 21. These temperatures and pressures are the preferable temperature range and pressure range for the liquid fuel premixture in the mixed fuel circulation supply loop 18.
  • the fuel premix supply system 14 includes a fuel premix supply line 46 that extends from the fuel premix supply reservoir or tank 44 to the fuel mixture supply line 22.
  • a filter 66 is provided inline the fuel premix supply line 46.
  • the fuel premix supply system 14 further includes a fuel cooler 60 inline the fuel premix supply line downstream from the filter.
  • the fuel premix supply system also includes a premix booster pump 50 for pumping the fuel premixture to the second stage 16 of the mixed fuel supply system 17.
  • the fuel premix supply system 14 also includes two temperature sensors 72 and 73 at either side of the fuel cooler, and a pressure sensor 74 downstream from the fuel cooler 60.
  • the fuel premix supply system 14 includes a diesel flush line 62 extending from a diesel supply circulation line 82 to the mixed fuel supply line 22, and a solenoid valve 52 inline the diesel flush line 62.
  • the fuel premix supply system 14 can include a fuel mixer (not shown) to mix the fuel premixture once more before it is passed to the second stage 16 of the dual fuel supply system 11.
  • the dual fuel supply system 11 is configured selectively to change over between the diesel supply system 80 and mixed fuel supply system 7 selectively to supply either diesel only or fuel premixture to the injection system 12.
  • the diesel supply system 80 is operatively able to supply diesel to the direct- injection system 12 at a supply pressure within the fuel demand pressure range of the direct-injection system 12.
  • the diesel supply system 80 includes a diesel supply circulation line or loop
  • a diesel circulation pump 86 is provided inline the diesel circulation supply loop 82 upstream from the high pressure pump 21.
  • the diesel circulation pump 86 can be the existing onboard low pressure fuel feed pump of the vehicle.
  • the fuel cooler 132 serves to keep the diesel cool while the engine runs on diesel. If the fuel lines were not kept cool, LPG of the mixed fuel may form a gas when the fuel is switched to mixed fuel and it contacts the hot fuel lines.
  • the additional fuel coolers may be constantly on or turned on for a short period prior to the fuel being switched from diesel to the mixed fuel.
  • Diesel passes fuel filter 67 and is pumped via pump 21 to the direct injection system 12.
  • the diesel supply system 80 includes a diesel bypass line 87 selectively to isolate the injection system 12 from the diesel circulation supply loop.
  • the dual fuel supply system 11 also includes a controller (not shown) that is interfaced with the relevant system components, pumps, valves, coolers, and the like, of the dual fuel supply system 11 to control the flow, temperature and pressure of the fuels through the system.
  • the controller is typically a dedicated logic controller or programmable logic controller.
  • the injection system 12 is supplied with either diesel or liquid fuel premixture of diesel and LPG.
  • fuel premixture When the fuel premixture is supplied to the injection-system 12 then fuel premixture circulates through the mixed fuel circulation supply loop 18 along flow path 20.
  • the cooler 28 reduces the temperature of the circulating fuel premixture to maintain the liquid fuel premixture in a liquefied state at the fuel supply pressure of the injection system 12.
  • the temperature sensor 30 measures the temperature of the circulating fuel premixture.
  • the pressure sensor 38 measures the pressure of the circulating fuel premixture.
  • the circulation rate of the fuel premixture trough the cooler 28 can be increased by the circulating pump 26 through the cooler 28.
  • Another way to control the temperature would be to circulate the fuel premixture at a constant rate, and to merely switch the fuel cooler on and off, as needed, to cool the fuel premixture.
  • the injection-system 12 uses fuel from the circulating fuel premixture that circulates in the mixed fuel circulation supply loop 18, which causes the supply pressure of the fuel premixture in the mixed fuel circulation loop 18 to drop over time. When the pressure of the circulating fuel premixture is reduced below a minimum threshold then the fuel premix supply system 14 is activated to supplement the mixed fuel circulating supply loop with fuel premixture from the fuel premix supply system 14.
  • Solenoid valve 68 is a safety cutout valve which is required in some countries like Australia. Solenoid valve 68 is not controlled by the dual fuel supply system controller, it is controlled independently by a separate safety * device. This device detects impulses coming from the crankshaft sensor of the engine. Only if the safety device detects such impulses, which indicates that the engine is running, it opens valve 68 starts the pump 50.
  • the fuel premix supply system 14 delivers the fuel premixture at a pressure that is sufficient to enter the mixed fuel circulation supply loop 18 and to charge the bladder accumulator 36 which increases the pressure of the circulating fuel premixture in the mixed fuel circulation supply loop 18.
  • the pressure sensor 38 measures the pressure in the mixed fuel circulating supply loop 18, and when the pressure of the circulating fuel premixture reaches a maximum threshold then pump 50 are switched off and valve 68 is closed.
  • valve 52 is opened for short duration to at least partly flush the second stage 16 of the mixed fuel supply system with diesel from the diesel supply system 80.
  • diesel is circulating through the diesel bypass line 87, in particular in the case which the on-board diesel feed pump 86 is mechanically driven and can not be turned off. Diesel circulates via bypass line 87 with the diesel return valve 89 open to return diesel to the tank 42.
  • valve 91 in the diesel circulating supply loop 82 When the dual fuel supply system 11 changes over from the mixed fuel supply system 17 to the diesel supply system 80, then the controller opens valve 91 in the diesel circulating supply loop 82 and closes valve 89 in the diesel bypass line 87, to start circulating diesel through the diesel supply circulation line 82.
  • valve 35 in the mixed fuel circulation supply loop 18 is closed and valve 34 in the mixed fuel bypass line 32 is opened so that the fuel premixture bypasses the injection system 12.
  • the controller is also configured automatically to change over from the mixed fuel supply system 17 to the diesel supply system 80 when the pressure in the mixed fuel supply circulation loop 8 drops below a set pressure threshold.
  • the controller is configured to monitor the temperature of the liquid fuel premixture in the mixed fuel supply circulation line, and to switch over to the diesel supply system if the temperature rises above a set temperature threshold. Further, the controller is configured to monitor the temperature in the mixed fuel bypass loop, and if the temperature of the liquid fuel premixture in the mixed fuel bypass loop is above a set temperature threshold then to resist switching over from the diesel supply system 80 to the mixed fuel supply system 17.
  • the controller is configured to monitor the supply temperature of the diesel, and if the supply temperature of the diesel is above a set temperature threshold then to resists change over to the mixed fuel supply system.
  • the controller is configured to trigger an alarm if the flow rate of diesel in the diesel supply circulation line or the flow rate of fuel premixture in the mixed fuel circulation line is below a set flow rate threshold.
  • Figure 3 shows a dual fuel supply system 100 that is essentially identical to the dual fuel supply system 11 in Figure 2, but includes additional system components.
  • the additional system components include in the mixed fuel circulation supply loop 18 a flow meter 102, an additional cooler 103, additional temperature sensor 110, additional pressure sensor 109, and a pressure holding valve 118 upstream from the cooler 103.
  • the fuel premix supply system 120 is substantially identical to the fuel premix supply system 14 in Figure 2, and the diesel supply system 111 of the dual fuel supply system 100 is substantially identical to the diesel supply system 80 in Figure 2.
  • the cooler 103 is common to the mixed fuel circulation line 102 and the diesel supply circulation line 82, and therefore retain the fuel fluidic path of the injection system 12 and the engine at a sufficient low temperature when the dual fuel supply system runs on diesel, so as to resist boiling of the fuel premixture when the fuel supply is changed over from the diesel supply system 80 to the mixed fuel supply system 17.
  • coolers 28 and 103 the temperature of the fuel, fuel premixture and/or diesel, is regulated at a sufficient low temperature that compensates for the additional heat that is introduced into the fuel when it circulates through the fuel fluidic path of the diesel engine and injection system.
  • FIG 4 shows another embodiment of a dual fuel supply system 140, in accordance with the invention.
  • the dual fuel supply system 140 includes a mixed fuel supply system 143 and a diesel supply system 144.
  • the diesel supply system 144 is substantially identical to the diesel supply system 80 in Figure 2.
  • the second stage 142 of the mixed fuel supply system 143 is essentially identical to the second stage 16 of the mixed fuel supply system 11 in Figure 2, in that it also includes a mixed fuel circulation supply loop 18, a mixed fuel bypass loop 32, a cooler 28 and a mixed fuel circulation pump 26 and solenoid valves 34 and 35.
  • the mixed fuel bladder accumulator 262 is positioned inline the mixed fuel supply line 22 towards a back end of the mixed fuel supply line 22, as opposed to being inline the mixed fuel circulation supply loop 18, and temperature sensor 264 and pressure sensor 263 is provided
  • the additional working and controlling of the dual fuel supply system 140 is essentially identical to that described above with reference to the, dual fuel supply system 1 1 in Figure 2.
  • Figure 5 shows another embodiment of a dual fuel supply system 210 that is essentially identical to the dual fuel supply system 140 in Figure 5, but that includes a number of additional system components in the mixed fuel system 214, not unlike the embodiment described with reference to Figure 3.
  • the fuel premix supply system 216 is similar to the fuel premix supply system
  • the mixed fuel supply system 269 further includes associated pressure sensors 268, 269 temperature sensors 270 and 272 for use in controlling the pressure and temperature of the fuel premixture that is supplied to the mixed fuel circulation supply loop 18.
  • the pressure regulating valve 266 ensures that the pressure of the fuel premixture in the mixed fuel supply circulation loop 18 is within the required pressure demand range of the injection system 12, thus, the pressure towards the backend of the pressure regulating valve 266 is maintained at a pressure that is sufficiently high to maintain the liquid fuel premixture in a liquefied state, and therefore does not require a fuel cooler in the fuel premix supply system 216. It will be appreciated that the addition of coolers in the diesel and LPG lines is nevertheless an optional feature. ADVANTAGES
  • the preferred embodiments of the dual fuel supply system for direct injection fuel systems have the advantage to provide the dual fuel supply system with either a fuel premixture or diesel only to the direct injection system, and is able to selectively to change over between the two systems.
  • the preferred embodiments of the dual fuel supply system is designed for receiving a fuel premixture from a refueling station, and to supply the fuel premixture to the direct injection system.
  • Another advantage of the preferred embodiments of the dual fuel supply system is that when the dual fuel supply system supplies diesel only to the direct injection system, the diesel temperature is controlled to retain the fuel flow path of the engine at a temperature that is safe for the dual fuel supply system to switch over to the mixed fuel supply system without causing boiling of the liquid fuel premixture.
  • a further advantage of the preferred embodiments of the dual fuel supply system is that it is able to regulate the supply temperature of the diesel or the fuel premixture at a temperature that is sufficiently lower than the vapor temperature of the fuel premixture, so as to compensate for the introduction of heat into the fuel premixture by the engine, in use, so as to retain the fuel premixture below its vapor temperature at the fuel demand pressure.
  • the preferred embodiments of the mixed fuel supply system is designed to minimize the volume of the fuel premixture flow path, so as to minimize the amount of fuel premixture that is resident in the mixed fuel supply system when the dual fuel supply system supplies diesel only to the direct injection system.
  • the preferred embodiments of the dual fuel supply system is configured at least partly to flush the fuel premixture flow path with diesel after the fuel premixture is supplied to the second stage of the mixed fuel supply system and before the diesel engine is stopped.
  • the preferred embodiments of the dual fuel supply system also has the advantage that the diesel supply system, the first stage of the mixed fuel supply system, and the second stage of the mixed fuel supply system are independently controllable.
  • the second stage of the mixed fuel supply system includes a pressure accumulator to buffer pressurized fuel premixture, and therefore separates continuous pressure control dependency from the first stage of the mixed fuel supply system and contributes to control stability during fuel demand fluctuation of the diesel engine.
  • the preferred embodiments of the dual fuel system employs multiple fuel coolers respectively within the sub-systems of the dual fuel supply system, which increase the temperature controllability of the fuels, through the dual fuel supply system.
  • the preferred embodiments of the dual fuel supply system is also designed to use a substantial part of the existing fuel system components, and therefore reduce the modifications needed to equip a diesel engine with the dual fuel supply system.

Abstract

The present invention is directed to a dual fuel supply system for supplying fuel to a direct-injection system of a diesel engine. The dual fuel supply system includes a diesel supply system to supply diesel to the direct-injection system; and a mixed fuel supply system that is operatively able to supply a liquid fuel premixture of diesel and liquefied gaseous fuel to the direct-injection system at a supply pressure within a fuel demand pressure range of the direct-injection system and at a corresponding temperature range that retains the fuel premixture below its vapor temperature as it flows through the fuel path of the direct-injection system and the diesel engine. The dual fuel supply system is configured to permit selective change over between the diesel supply system and the mixed fuel system to supply the direct-injection system selectively with either diesel or liquid fuel premixture respectively. The liquid fuel premixture is supplied to the dual fuel system as an off-board fuel premixture.

Description

A DUAL FUEL SUPPLY SYSTEM FOR A DIRECT-INJECTION SYSTEM OF A DIESEL ENGINE WITH OFF-BOARD MIXING
FIELD OF INVENTION
The present invention relates to fuel systems for diesel engines. In particular, the invention relates to a dual fuel supply system for a diesel engine having a direct- injection system. The invention extends to a diesel engine incorporating the dual fuel supply system and to a vehicle that incorporates a diesel engine having the dual fuel supply system.
This invention relates particularly but not exclusively to a dual fuel supply system for diesel engines of trucks. It will therefore be convenient hereinafter to describe the invention with reference to this example application. However, at the same time it must be recognized that the invention applies to other applications such as to diesel engines for light vehicles and to other types of internal combustion engines.
BACKGROUND TO THE INVENTION
Dual fuel supply systems for supplying a fuel mixture of diesel and gaseous fuel to diesel engines are known. Some dual fuel supply systems introduce the gaseous fuel into the air supply that leads to the combustion chamber. In US2005202021 a separate set of injectors introduce gaseous LPG into the combustion chamber, whereas in US5408957, US4520766, JP1318755 and GB1252458, gaseous LPG is mixed with air prior to introducing the air mixture to the combustion chamber. The use of LPG and diesel at the same time has recently been addressed by the dual fuel system disclosed in WO 2008036999 where liquid LPG and diesel were mixed in a chamber prior to being introduced into the combustion chambers. However there are problems associated with the dual fuel system disclosed in WO 2008036999 in its application with different engine types.
OBJECT OF THE INVENTION
It is an object of the present invention to provide an alternative dual fuel supply system suitable for direct injection systems that overcome at least in part the problems associated with prior art dual fuel supply systems.
SUMMARY OF THE INVENTION
In first aspect the invention provides a dual fuel supply system for supplying fuel to a direct-injection system of a diesel engine, the dual fuel supply system including:
a diesel supply system to supply diesel to the direct-injection system; and a mixed fuel supply system that is operatively able to supply a liquid fuel premixture of diesel and liquefied gaseous fuel to the direct-injection system at a supply pressure within a fuel demand pressure range of the direct-injection system and at a corresponding temperature range that retains the fuel premixture below its vapor temperature as it flows through the fuel path of the direct-injection system and the diesel engine, in which the dual fuel supply system is configured to permit selective change over between the diesel supply system and the mixed fuel system to supply the direct-injection system selectively with either diesel or liquid fuel premixture respectively; said liquid fuel premixture is supplied to the dual fuel system as an off-board fuel premixture.
The fuel premixture is mixed off board and is preferably stored in a tank or reservoir prior to use by the dual fuel system.
The diesel supply system is preferably operatively able to supply diesel to the direct-injection system at a supply pressure within the fuel demand pressure range of the direct-injection system and at a supply temperature range that corresponds with the supply temperature range of the mixed fuel supply system.
The mixed fuel supply system is preferably configured to regulate the supply pressure of the liquid fuel premixture within a pressure range towards a high end of the fuel demand pressure of the direct-injection system.
The mixed fuel supply system is preferably configured to supply the fuel premixture at a supply temperature that is sufficiently lower than the vapor temperature of the liquid fuel premixture at the supply pressure to compensate for heat that is introduced into the liquid fuel premixture by engine heat as it flows , through the fuel path of the direct-injection system and the diesel engine.
The mixed fuel supply system preferably includes a first stage and a second stage, and in which the second stage of the mixed fuel supply system is configured to regulate the supply pressure and the supply temperature at which the liquid fuel premixture is supplied to the direct-injection system.
The mixed fuel supply system is preferably configured to trigger the first stage of the mixed fuel supply system to supply liquid fuel premixture to the second stage of the mixed fuel supply system when the supply pressure in the second stage of the mixed fuel supply system drops towards a low end of the fuel demand pressure range of the direct-injection system. The mixed fuel supply system preferably includes a pressure accumulator, and in which the first stage of the mixed fuel supply system is triggered to charge the pressure accumulator with fuel premixture when the supply pressure in the second stage of the mixed fuel supply system drops towards a low end of the fuel demand pressure of the direct-injection system.
The second stage of the mixed fuel supply system preferably includes a mixed fuel supply circulation line that defines a mixed fuel supply circulation flow path that is connected or connectable inline in flow circulation with a high pressure pump and a fuel rail of the direct-injection system.
An overflow line of the high pressure pump of the direct-injection system is preferably connected in flow communication with the mixed fuel circulation line.
The mixed fuel supply circulation line preferably defines a mixed fuel supply circulation flow path that has a flow path volume to accommodate at least the amount of liquid fuel premixture that the diesel engine consumes at full load for one minute.
The second stage of the mixed fuel supply system preferably includes a circulation pump inline the mixed fuel supply circulation line. The circulation pump is preferably a variable speed controlled pump.
The second stage of the mixed fuel supply system preferably includes at least one fuel cooler inline the mixed fuel supply circulation line upstream of the direct- injection system and downstream of the mixed fuel pressure accumulator.
The at least one fuel cooler preferably includes an evaporator through which a refrigerant is passed, and a shut-off valve to shut-off the flow of refrigerant through the evaporator. The second stage of the mixed fuel supply system preferably includes a temperature sensor upstream from the direct-injection system, to measure the supply temperature of the liquid fuel premixture that is supplied to the direct-injection system.
There is preferably a temperature sensor downstream from the direct-injection system, to measure a temperature of the liquid fuel premixture that discharges from the direct-injection system into the mixed fuel supply circulation line.
The second stage of the mixed fuel supply system preferably includes a flow sensor to measure a flow rate of liquid fuel premixture circulating through the mixed fuel supply circulation line.
The mixed fuel pressure accumulator is preferably a bladder accumulator. The second stage of the mixed fuel supply system preferably includes at least one pressure sensor upstream from the direct-injection system to measure the supply pressure of the liquid fuel premixture being supplied to the direct-injection system.
The second stage of the mixed fuel supply system preferably includes a mixed fuel supply line to connect the first stage of the mixed fuel supply system in flow communication with the second stage of the mixed fuel supply system, and in which the mixed fuel supply line joins the mixed fuel supply circulation line upstream from the circulation pump that is inline the mixed fuel supply circulation line.
The second stage of the mixed fuel supply system preferably includes a pressure regulating valve inline the mixed fuel supply line.
The first stage of the mixed fuel supply system is preferably a. fuel premix supply system that is configured to receive and store a fuel premixture of diesel and liquefied gaseous fuel and to supply the fuel premixture to the second stage of the mixed fuel supply system.
The fuel premix supply system preferably includes a fuel premix supply line that extends from a fuel premix supply reservoir to the fuel mixture supply line.
The fuel premix supply system preferably includes a filter inline the fuel premix supply line.
The fuel premix supply system preferably includes a fuel cooler inline the fuel premix supply line.
The fuel premix supply system preferably includes a premix booster pump for pumping the fuel premixture to the second stage of the mixed fuel supply system.
The fuel premix supply system preferably includes at least one temperature sensor upstream from the fuel cooler.
The fuel premix supply system preferably includes a diesel flush line extending from the diesel supply circulation line to the mixed fuel supply line.
The fuel premix supply system preferably includes a solenoid valve inline the diesel flush line.
The second stage of the mixed fuel supply system preferably includes a mixed fuel bypass line selectively to bypass the direct-injection system.
The diesel supply system preferably includes a diesel supply circulation line that is connected or connectable in flow communication inline with the fuel rail of the direct-injection system.
The diesel supply system preferably includes at least one fuel cooler inline the diesel supply circulation line upstream from the direct injection-system.
The diesel supply system preferably includes a diesel booster pump inline the diesel supply circulation line upstream from the at least one fuel cooler. The diesel supply system preferably includes a diesel bypass selectively to bypass the direct-injection system.
The dual fuel supply system preferably includes a controller that is configured to control selectively the change over between the diesel supply system and the mixed fuel supply system.
The controller is preferably configured to flush the mixed fuel supply line with diesel before switching over from the mixed fuel supply system to the diesel system.
The controller is preferably configured to flush the mixed fuel supply line with diesel after the fuel premix supply system charged the second stage of the mixed fuel supply system with liquid fuel premixture.
The controller is preferably configured to flush the mixed fuel supply line with diesel before the diesel engine is stopped.
The controller is preferably configured to regulate the flow rate of the fuel premixture through the mixed fuel cooler to regulate the temperature of the fuel premixture.
The controller is preferably configured to open the diesel supply circulation line prior to opening the mixed fuel bypass line.
The controller is preferably configured to open the mixed fuel supply circulation line prior to opening the diesel bypass line.
The controller is preferably configured automatically to change over from the mixed fuel supply system to the diesel supply system when the pressure in the mixed fuel supply circulation loop drops below a set pressure threshold.
The controller is preferably configured to monitor the temperature of the liquid fuel premixture in the mixed fuel supply circulation line, and to switch over to the diesel supply system if the temperature rises above a set temperature threshold. The controller is preferably configured to monitor the temperature in the mixed fuel bypass loop, and if the temperature of the liquid fuel premixture in the mixed fuel bypass loop is above a set temperature threshold then to resist switching over from the diesel supply system to the mixed fuel supply system.
The controller is preferably configured to monitor the supply temperature of the diesel, and if the supply temperature of the diesel is above a set temperature threshold then to resist change over to the mixed fuel supply system.
The controller is preferably configured to trigger an alarm if the flow rate of diesel in the diesel supply circulation line or the flow rate of fuel premixture in the mixed fuel circulation line is below a set flow rate threshold.
In a preferred form the dual supply system can be retrofitted as a kit to existing vehicles.
In a second aspect the invention provides a diesel engine that includes:
an direct-injection system; and
a dual fuel supply system as defined in accordance with the first aspect of the invention.
The dual fuel supply system preferably includes any one or more of the features described above in accordance with the first aspect of the invention.
In a third aspect the invention provides a vehicle that includes:
a diesel engine having an direct-injection system; and
a dual fuel supply system as defined in accordance with the first aspect of the invention.
The dual fuel supply system preferably includes any one or more of the features described above in accordance with the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS
In order that the present invention can be more readily understood reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:
Figure 1 is a schematic functional block diagram of a dual fuel supply system, in accordance with the invention;
Figure 2 is a schematic representation of a first embodiment of the dual fuel supply system;
Figure 3 is a schematic representation of a second embodiment of the dual fuel supply system the includes the first embodiment and additional system components;
Figure 4 is a schematic representation of a third embodiment of the dual fuel supply system; and
Figure 5 is a schematic representation of a fourth embodiment of the dual fuel supply system that includes the third embodiment and additional system components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 1 , reference numeral 10 generally indicates a dual fuel supply system in accordance with the invention for supplying fuel to a direct-injection system (the injection system) 12 of a diesel engine (not shown). In this specification with direct-injection system is meant to include a high pressure pump having a low pressure intake side and a high pressure outlet side that supplies fuel at a relative high pressure to a fuel rail which supplies the fuel to injectors. The intake or low pressure side of a high pressure pump of a direct-injection system has an operative intake pressure of typically between 2 bar to 15 bar. The intake pressure range of the high pressure pump is herein referred to as the fuel demand pressure range of the direct-injection system.
Broadly, each of the embodiments described below includes two subsystems. One sub-system is a mixed fuel supply system 17 that includes a first stage 14 of the mixed fuel supply system 17 having a fuel premix tank 44 for receiving and storing a liquid fuel premixture of diesel and liquefied gaseous fuel and system components 13 for supplying the liquid fuel premixture to the second stage 16 of the mixed fuel supply system 17. Second stage 16 includes system components 15. The liquid fuel premixture is typically a mixture of diesel and liquid petroleum gas (LPG), however, it will be appreciated that a dual fuel supply system, in accordance with the invention, can be configured for use with different types of fuel premixtures.
The mixed fuel supply system 17 is operatively able to supply the liquid fuel premixture of diesel and liquefied gaseous fuel to the direct-injection system at a supply pressure range that matches the fuel demand pressure range of the injection system 12 and at a corresponding temperature range that retains the fuel premixture below its vapor temperature as it flows through the fuel path of the direct-injection system 12 and the diesel engine.
Another subsystem of the dual fuel supply system 10 is a diesel supply system 80 and includes the diesel tank 42 and system components 79 for delivering diesel to the injection system 12 and circulating diesel to the tank 42.
The dual fuel supply system 10 includes conduits or lines that define various flow paths, and system components that regulate and control the active flow paths, flow rates, temperature, and pressure of the diesel or fuel premixture through the dual fuel supply system 1 1 , as is explained in more detail below. Moreover, the dual fuel supply system 10 is configured to permit selective change over between the diesel supply system 80 and the mixed fuel system 17 to supply the injection system 12 selectively with either diesel or liquid fuel premixture respectively.
Figure 2 shows a schematic diagram of an embodiment 11 of the due-fuel supply system. The dual fuel supply system 1 1 includes a mixed fuel supply system 17 that includes the first stage 14 for receiving and storing and supplying the second stage 16 with the fuel premixture. The second stage 16 is for supplying the injection system 12 with the fuel premixture from the first stage 14 of the mixed fuel supply system 17. The second stage 16 of the mixed fuel supply system 17 forms a fuel premix supply system.
The second stage 16 of the mixed fuel supply system 17 includes a mixed fuel supply circulation line or loop 18 that defines a mixed fuel supply circulation flow path (see arrow 20). The mixed fuel supply circulation loop 18 js connected in flow communication inline with the high pressure pump 21 and fuel rail 23 that forms part of the injection system 2 for circulating fuel premixture through the fuel rail of the injection system 12.
A mixed fuel supply line 22 that defines a mixed fuel supply line flow path (see arrow 24) extends between the fuel premix supply system 14 and the mixed fuel supply circulation loop 18 to supply fuel premixture to the mixed fuel supply circulation loop 18 from the fuel premix supply system 14.
The second stage 16 of the mixed fuel supply system 17 includes a circulation pump 26 inline the mixed fuel supply circulation loop 18 and a fuel cooler 28 inline the mixed fuel supply circulation loop 18 upstream from the direct injection-system 12 and downstream from the circulation pump 26. In this embodiment, the circulation pump is a controllable variably speed pump and the fuel cooler includes an evaporator that is connected inline with the refrigerant line of the air conditioning system of the truck. However, it will be appreciated that the fuel cooler can be a stand alone fuel cooler.
A temperature sensor 30 is provided upstream from the direct-injection system 12, to measure the supply temperature of the liquid fuel premixture that is supplied to the injection system 12.
The dual fuel supply system 11 also includes a mixed fuel bypass line 32 selectively to isolate the direct-injection system 12 from the mixed fuel supply circulation line 18 (see arrow 33).
Valves in the form of a controllable normally closed solenoid valve 35 and normally opened solenoid valve 34 are provided inline the mixed fuel circulation supply loop 18 and the bypass line 32 respectively, selectively to divert fuel premixture, through either flow path 20 or 33.
The second stage 16 of the mixed fuel supply system 17 also includes a pressure accumulator 36 inline the mixed fuel circulation supply loop 18 downstream from the direct-injection system 2 and upstream from the circulation pump 26.
The pressure accumulator 36 is in the form of a bladder accumulator.
To this end, the second stage 16 of the mixed fuel supply system 17 includes at least one pressure sensor 38 upstream from the direct-injection system 12 to measure the supply pressure of the liquid fuel premixture being supplied to the direct-injection system 12.
The fuel premix supply system 14 is configured to supply the liquid fuel premixture to the second stage 16 of the mixed fuel supply system 17. The fuel premixture can have a ratio of between about 10% and 50% parts per mass diesel to between 90% and 50% parts per mass LPG.
Moreover, the fuel premixture is supplied to the mixed fuel circulation supply loop 18 at a pressure of between 2.0bar and 15.0bar at a temperature of between 8.5°C and +55°C, depending on the intake pressure rating of .the high pressure pump 21. These temperatures and pressures are the preferable temperature range and pressure range for the liquid fuel premixture in the mixed fuel circulation supply loop 18.
The fuel premix supply system 14 includes a fuel premix supply line 46 that extends from the fuel premix supply reservoir or tank 44 to the fuel mixture supply line 22.
A filter 66 is provided inline the fuel premix supply line 46.
The fuel premix supply system 14 further includes a fuel cooler 60 inline the fuel premix supply line downstream from the filter.
The fuel premix supply system also includes a premix booster pump 50 for pumping the fuel premixture to the second stage 16 of the mixed fuel supply system 17.
The fuel premix supply system 14 also includes two temperature sensors 72 and 73 at either side of the fuel cooler, and a pressure sensor 74 downstream from the fuel cooler 60.
. The fuel premix supply system 14 includes a diesel flush line 62 extending from a diesel supply circulation line 82 to the mixed fuel supply line 22, and a solenoid valve 52 inline the diesel flush line 62. The fuel premix supply system 14 can include a fuel mixer (not shown) to mix the fuel premixture once more before it is passed to the second stage 16 of the dual fuel supply system 11.
The dual fuel supply system 11 is configured selectively to change over between the diesel supply system 80 and mixed fuel supply system 7 selectively to supply either diesel only or fuel premixture to the injection system 12.
The diesel supply system 80 is operatively able to supply diesel to the direct- injection system 12 at a supply pressure within the fuel demand pressure range of the direct-injection system 12.
The diesel supply system 80 includes a diesel supply circulation line or loop
82 (see arrow 84) that is connected in flow communication inline with the direct- injection system 12.
A diesel circulation pump 86 is provided inline the diesel circulation supply loop 82 upstream from the high pressure pump 21. The diesel circulation pump 86 can be the existing onboard low pressure fuel feed pump of the vehicle. There is a fuel filter 70 upstream of the diesel circulation pump 86 to filter the diesel passing along the diesel supply circulation line. There is also an additional fuel cooler 132 in the diesel supply circulation line downstream of pump 86 but upstream of fuel filter 67. The fuel cooler 132 serves to keep the diesel cool while the engine runs on diesel. If the fuel lines were not kept cool, LPG of the mixed fuel may form a gas when the fuel is switched to mixed fuel and it contacts the hot fuel lines. The additional fuel coolers may be constantly on or turned on for a short period prior to the fuel being switched from diesel to the mixed fuel. Diesel passes fuel filter 67 and is pumped via pump 21 to the direct injection system 12. There is a pressure relief valve 65 for mixed fuel in the circulation loop 20. There is also a pressure relief valve 69 for overflow of fuel from the fuel rail 23.
The diesel supply system 80 includes a diesel bypass line 87 selectively to isolate the injection system 12 from the diesel circulation supply loop.
The dual fuel supply system 11 also includes a controller (not shown) that is interfaced with the relevant system components, pumps, valves, coolers, and the like, of the dual fuel supply system 11 to control the flow, temperature and pressure of the fuels through the system. The controller is typically a dedicated logic controller or programmable logic controller.
In use, when the diesel engine is in operation, the injection system 12 is supplied with either diesel or liquid fuel premixture of diesel and LPG.
When the fuel premixture is supplied to the injection-system 12 then fuel premixture circulates through the mixed fuel circulation supply loop 18 along flow path 20. The cooler 28 reduces the temperature of the circulating fuel premixture to maintain the liquid fuel premixture in a liquefied state at the fuel supply pressure of the injection system 12. The temperature sensor 30 measures the temperature of the circulating fuel premixture. At the same time the pressure sensor 38 measures the pressure of the circulating fuel premixture.
If the pressure of the circulating fuel premixture is within its required pressure range but its temperature increases beyond a maximum threshold temperature then the circulation rate of the fuel premixture trough the cooler 28 can be increased by the circulating pump 26 through the cooler 28. Another way to control the temperature would be to circulate the fuel premixture at a constant rate, and to merely switch the fuel cooler on and off, as needed, to cool the fuel premixture. The injection-system 12 uses fuel from the circulating fuel premixture that circulates in the mixed fuel circulation supply loop 18, which causes the supply pressure of the fuel premixture in the mixed fuel circulation loop 18 to drop over time. When the pressure of the circulating fuel premixture is reduced below a minimum threshold then the fuel premix supply system 14 is activated to supplement the mixed fuel circulating supply loop with fuel premixture from the fuel premix supply system 14.
When the fuel premix supply system 14 is activated the solenoid valve 68 is opened and pump 50 is started to pump fuel premixture to the second stage 16 of the mixed fuel supply system. Solenoid valve 68 is a safety cutout valve which is required in some countries like Australia. Solenoid valve 68 is not controlled by the dual fuel supply system controller, it is controlled independently by a separate safety * device. This device detects impulses coming from the crankshaft sensor of the engine. Only if the safety device detects such impulses, which indicates that the engine is running, it opens valve 68 starts the pump 50.
With pump 50, the fuel premix supply system 14 delivers the fuel premixture at a pressure that is sufficient to enter the mixed fuel circulation supply loop 18 and to charge the bladder accumulator 36 which increases the pressure of the circulating fuel premixture in the mixed fuel circulation supply loop 18. The pressure sensor 38 measures the pressure in the mixed fuel circulating supply loop 18, and when the pressure of the circulating fuel premixture reaches a maximum threshold then pump 50 are switched off and valve 68 is closed.
After fuel premixture is pumped to the second stage 16 of the mixed fuel supply system 17, then valve 52 is opened for short duration to at least partly flush the second stage 16 of the mixed fuel supply system with diesel from the diesel supply system 80.
Meanwhile, diesel is circulating through the diesel bypass line 87, in particular in the case which the on-board diesel feed pump 86 is mechanically driven and can not be turned off. Diesel circulates via bypass line 87 with the diesel return valve 89 open to return diesel to the tank 42.
When the dual fuel supply system 11 changes over from the mixed fuel supply system 17 to the diesel supply system 80, then the controller opens valve 91 in the diesel circulating supply loop 82 and closes valve 89 in the diesel bypass line 87, to start circulating diesel through the diesel supply circulation line 82.
Subsequently, valve 35 in the mixed fuel circulation supply loop 18 is closed and valve 34 in the mixed fuel bypass line 32 is opened so that the fuel premixture bypasses the injection system 12.
Thus, while the diesel supply system 80 is supplying diesel to the injection system 12, fuel premixture is still being circulated in the mixed fuel bypass loop 33 through the cooler 28 to keep the resident fuel premixture in the mixed fuel circulation supply loop 18 at a sufficiently low temperature that prevents boiling of the liquid fuel premixture.
The controller is also configured automatically to change over from the mixed fuel supply system 17 to the diesel supply system 80 when the pressure in the mixed fuel supply circulation loop 8 drops below a set pressure threshold.
There are also safety measures built into the system, such as that the controller is configured to monitor the temperature of the liquid fuel premixture in the mixed fuel supply circulation line, and to switch over to the diesel supply system if the temperature rises above a set temperature threshold. Further, the controller is configured to monitor the temperature in the mixed fuel bypass loop, and if the temperature of the liquid fuel premixture in the mixed fuel bypass loop is above a set temperature threshold then to resist switching over from the diesel supply system 80 to the mixed fuel supply system 17.
In addition, the controller is configured to monitor the supply temperature of the diesel, and if the supply temperature of the diesel is above a set temperature threshold then to resists change over to the mixed fuel supply system.
The controller is configured to trigger an alarm if the flow rate of diesel in the diesel supply circulation line or the flow rate of fuel premixture in the mixed fuel circulation line is below a set flow rate threshold.
Figure 3 shows a dual fuel supply system 100 that is essentially identical to the dual fuel supply system 11 in Figure 2, but includes additional system components. The additional system components include in the mixed fuel circulation supply loop 18 a flow meter 102, an additional cooler 103, additional temperature sensor 110, additional pressure sensor 109, and a pressure holding valve 118 upstream from the cooler 103.
The fuel premix supply system 120 is substantially identical to the fuel premix supply system 14 in Figure 2, and the diesel supply system 111 of the dual fuel supply system 100 is substantially identical to the diesel supply system 80 in Figure 2.
The cooler 103 is common to the mixed fuel circulation line 102 and the diesel supply circulation line 82, and therefore retain the fuel fluidic path of the injection system 12 and the engine at a sufficient low temperature when the dual fuel supply system runs on diesel, so as to resist boiling of the fuel premixture when the fuel supply is changed over from the diesel supply system 80 to the mixed fuel supply system 17.
Also* with coolers 28 and 103 the temperature of the fuel, fuel premixture and/or diesel, is regulated at a sufficient low temperature that compensates for the additional heat that is introduced into the fuel when it circulates through the fuel fluidic path of the diesel engine and injection system.
Where there are similar features in alternative embodiments as in the embodiment shown in Figure 2, they have been given the same numbers to indicate their similarity and relevant description regarding these features of the embodiment shown in Figure 2 also apply to the similarly numbered features shown in the alternative embodiments.
Figure 4 shows another embodiment of a dual fuel supply system 140, in accordance with the invention. The dual fuel supply system 140 includes a mixed fuel supply system 143 and a diesel supply system 144. The diesel supply system 144 is substantially identical to the diesel supply system 80 in Figure 2.
. The second stage 142 of the mixed fuel supply system 143 is essentially identical to the second stage 16 of the mixed fuel supply system 11 in Figure 2, in that it also includes a mixed fuel circulation supply loop 18, a mixed fuel bypass loop 32, a cooler 28 and a mixed fuel circulation pump 26 and solenoid valves 34 and 35. However, the mixed fuel bladder accumulator 262 is positioned inline the mixed fuel supply line 22 towards a back end of the mixed fuel supply line 22, as opposed to being inline the mixed fuel circulation supply loop 18, and temperature sensor 264 and pressure sensor 263 is provided The additional working and controlling of the dual fuel supply system 140 is essentially identical to that described above with reference to the, dual fuel supply system 1 1 in Figure 2.
Figure 5 shows another embodiment of a dual fuel supply system 210 that is essentially identical to the dual fuel supply system 140 in Figure 5, but that includes a number of additional system components in the mixed fuel system 214, not unlike the embodiment described with reference to Figure 3.
The fuel premix supply system 216 is similar to the fuel premix supply system
146.
A difference compared to the embodiment in Figures 2, is that a cooler 265 is provided inline the mixed fuel supply line 22 upstream from the mixed fuel bladder accumulator 272. Also, a pressure regulating valve 266 is positioned upstream from the cooler 265 inline the mixed fuel supply line 22.
The mixed fuel supply system 269 further includes associated pressure sensors 268, 269 temperature sensors 270 and 272 for use in controlling the pressure and temperature of the fuel premixture that is supplied to the mixed fuel circulation supply loop 18.
The pressure regulating valve 266 ensures that the pressure of the fuel premixture in the mixed fuel supply circulation loop 18 is within the required pressure demand range of the injection system 12, thus, the pressure towards the backend of the pressure regulating valve 266 is maintained at a pressure that is sufficiently high to maintain the liquid fuel premixture in a liquefied state, and therefore does not require a fuel cooler in the fuel premix supply system 216. It will be appreciated that the addition of coolers in the diesel and LPG lines is nevertheless an optional feature. ADVANTAGES
The preferred embodiments of the dual fuel supply system for direct injection fuel systems have the advantage to provide the dual fuel supply system with either a fuel premixture or diesel only to the direct injection system, and is able to selectively to change over between the two systems.
The preferred embodiments of the dual fuel supply system is designed for receiving a fuel premixture from a refueling station, and to supply the fuel premixture to the direct injection system.
Another advantage of the preferred embodiments of the dual fuel supply system is that when the dual fuel supply system supplies diesel only to the direct injection system, the diesel temperature is controlled to retain the fuel flow path of the engine at a temperature that is safe for the dual fuel supply system to switch over to the mixed fuel supply system without causing boiling of the liquid fuel premixture.
A further advantage of the preferred embodiments of the dual fuel supply system is that it is able to regulate the supply temperature of the diesel or the fuel premixture at a temperature that is sufficiently lower than the vapor temperature of the fuel premixture, so as to compensate for the introduction of heat into the fuel premixture by the engine, in use, so as to retain the fuel premixture below its vapor temperature at the fuel demand pressure.
Advantageously, the preferred embodiments of the mixed fuel supply system is designed to minimize the volume of the fuel premixture flow path, so as to minimize the amount of fuel premixture that is resident in the mixed fuel supply system when the dual fuel supply system supplies diesel only to the direct injection system. Also, the preferred embodiments of the dual fuel supply system is configured at least partly to flush the fuel premixture flow path with diesel after the fuel premixture is supplied to the second stage of the mixed fuel supply system and before the diesel engine is stopped.
The preferred embodiments of the dual fuel supply system also has the advantage that the diesel supply system, the first stage of the mixed fuel supply system, and the second stage of the mixed fuel supply system are independently controllable. In particular, the second stage of the mixed fuel supply system includes a pressure accumulator to buffer pressurized fuel premixture, and therefore separates continuous pressure control dependency from the first stage of the mixed fuel supply system and contributes to control stability during fuel demand fluctuation of the diesel engine.
Also, the preferred embodiments of the dual fuel system employs multiple fuel coolers respectively within the sub-systems of the dual fuel supply system, which increase the temperature controllability of the fuels, through the dual fuel supply system.
The preferred embodiments of the dual fuel supply system is also designed to use a substantial part of the existing fuel system components, and therefore reduce the modifications needed to equip a diesel engine with the dual fuel supply system.
VARIATIONS
It will of course be realized that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth. Throughout the description and claims this specification the word "comprise" and variations of that word such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

Claims

1. A dual fuel supply system for supplying fuel to a direct-injection system of a diesel engine, the dual fuel supply system including:
a diesel supply system to supply diesel to the direct-injection system; and a mixed fuel supply system that is operatively able to supply a liquid fuel premixture of diesel and liquefied gaseous fuel to the direct-injection system at a supply pressure within a fuel demand pressure range of the direct-injection system and at a corresponding temperature range that retains the fuel premixture below its vapor temperature as it flows through the fuel path of the direct-injection system and the diesel engine, in which the dual fuel supply system is configured to permit selective change over between the diesel supply system and the mixed fuel system to supply the direct-injection system selectively with either diesel or liquid fuel premixture respectively; said liquid fuel premixture is supplied to the dual fuel system as an off-board fuel premixture.
2. A dual fuel supply system as claimed in claim 1 , wherein the diesel supply system is operatively able to supply diesel to the direct-injection system at a supply pressure within the fuel demand pressure range of the direct-injection system and at a supply temperature range that corresponds with the supply temperature range of the mixed fuel supply system.
3. A dual fuel supply system as claimed in claim 2, wherein the mixed fuel supply system is configured to regulate the supply pressure of the liquid fuel premixture within a pressure range towards a high end of the fuel demand pressure of the direct-injection system.
4. A dual fuel supply system as claimed in claim 1 , wherein the fuel premixture is mixed off board and is stored in a tank or reservoir prior to use by the dual fuel system.
5. A dual fuel supply system as claimed in claim 1 , wherein the mixed fuel supply system is configured to supply the fuel premixture at a supply temperature that is sufficiently lower than the vapor temperature of the liquid fuel premixture at the supply pressure to compensate for heat that is introduced into the liquid fuel premixture by engine heat as it flows through the fuel path of the direct-injection system and the diesel engine. 5. A dual fuel supply system as claimed in claim 1 , wherein the mixed fuel supply system includes a first stage and a second stage, and in which the second stage of the mixed fuel supply system is configured to regulate the supply pressure and the supply temperature at which the liquid fuel premixture is supplied to the direct-injection system; wherein the mixed fuel supply system is configured to trigger the first stage of the mixed fuel supply system to supply liquid fuel premixture to the second stage of the mixed fuel supply system when the supply pressure in the second stage of the mixed fuel supply system drops towards a low end of the fuel demand pressure range of the direct-injection system.
6. A dual fuel supply system as claimed in claim 5, wherein the mixed fuel supply system includes a pressure accumulator, and in which the first stage of the mixed fuel supply system is triggered to charge the pressure accumulator with fuel premixture when the supply pressure in the second stage of the mixed fuel supply system drops towards a low end of the fuel demand pressure of the direct-injection system.
7. A dual fuel supply system as claimed in claim 5, wherein the second stage of the mixed fuel supply system includes a mixed fuel supply circulation line that defines a mixed fuel supply circulation flow path that is connected or connectable inline in flow circulation with a high pressure pump and a fuel rail of the direct- injection system; wherein there is an overflow line of the high pressure pump of the direct-injection system is connected in flow communication with the mixed fuel circulation line; wherein the mixed fuel supply circulation line defines a mixed fuel supply circulation flow path that has a flow path volume to accommodate at least the amount of liquid fuel premixture that the diesel engine consumes at full load for one minute.
8. A dual fuel supply system as claimed in claim 5, wherein the second stage of the mixed fuel supply system includes a circulation pump inline the mixed fuel supply circulation line; said circulation pump is a variable speed controlled pump.
9. A dual fuel supply system as claimed in claim 5, wherein the second stage of the mixed fuel supply system includes at least one fuel cooler inline the mixed fuel supply circulation line upstream from the direct injection-system and downstream from the circulation pump.
10. A dual fuel supply system as claimed in claim 5, wherein the at least one fuel cooler includes an evaporator through which a refrigerant is passed, and a shut-off valve to shut-off the flow of refrigerant through the evaporator.
11. A dual fuel supply system as claimed in claim 5, wherein the second stage of the mixed fuel supply system includes a temperature sensor upstream from the direct-injection system, to measure the supply temperature of the liquid fuel premixture that is supplied to the direct-injection system; wherein there is a temperature sensor downstream from the direct-injection system, to measure a temperature of the liquid fuel premixture that discharges from the direct-injection system into the mixed fuel supply circulation line; wherein there is a flow sensor to measure a flow rate of liquid fuel premixture circulating through the mixed fuel supply circulation line and at least one pressure sensor upstream from the direct-injection system to measure the supply pressure of the liquid fuel premixture being supplied to the direct-injection system.
12. A dual fuel supply system as claimed in claim 5, wherein the first stage of the mixed fuel supply system includes a fuel premix supply system that is configured to . receive and store a fuel premixture of diesel and liquefied gaseous fuel and to supply the fuel premixture to the second stage of the mixed fuel supply system.
13. A dual fuel supply system as claimed in claim 12, wherein there is a fuel premix supply line that extends from a fuel premix supply reservoir to the fuel mixture supply line, said fuel premix supply line includes an inline filter, a fuel cooler, and at least one temperature sensor upstream from the fuel cooler.
14 A dual fuel supply system as claimed in claim 12 or 13, wherein the fuel premix supply system includes a diesel flush line extending from the diesel supply circulation line to the mixed fuel supply line; said diesel flush line includes an inline solenoid valve.
15. A dual fuel supply system as claimed in any one of the above mentioned claims, wherein there is a mixed fuel bypass line selectively to bypass the direct- injection system.
16. A dual fuel supply system as claimed in any one of the above mentioned claims, wherein the diesel supply system includes a diesel supply circulation line that is connected or connectable in flow communication inline with the fuel rail of the direct-injection system; said diesel supply system includes at least one fuel cooler inline the diesel supply circulation line upstream from the direct injection-system and a diesel booster pump inline the diesel supply circulation line upstream from the at least one fuel cooler; the diesel supply system also includes a diesel bypass selectively to bypass the direct-injection system:
17. A dual fuel supply system as claimed in any one of the above mentioned claims, wherein the dual fuel supply system includes a controller that is configured to control selectively the change over between the diesel supply system and the mixed fuel supply system; the controller is configured to flush the mixed fuel supply line with diesel before switching over from the mixed fuel supply system to the diesel system; the controller is configured to flush the mixed fuel supply line with diesel after the fuel premix supply system charged the second stage of the mixed fuel supply system with liquid fuel premixture; the controller is configured to flush the mixed fuel supply line with diesel before the diesel engine is stopped; the controller is configured to regulate the flow rate of the fuel premixture through the mixed fuel cooler to regulate the temperature of the fuel premixture; the controller is configured to open the diesel supply circulation line prior to opening the mixed fuel bypass line; the controller is configured to open the mixed fuel supply circulation line prior to opening the diesel bypass line.
18. A dual fuel supply system as claimed in any one of the above mentioned claims, wherein the controller is configured automatically to change over from the mixed fuel supply system to the diesel supply system when the pressure in the mixed fuel supply circulation loop drops below a set pressure threshold; the controller is configured to monitor the temperature of the liquid fuel premixture in the mixed fuel supply circulation line and to switch over to the diesel supply system if the temperature rises above a set temperature threshold; the controller is configured to monitor the temperature in the mixed fuel bypass loop and if the temperature of the liquid fuel premixture in the mixed fuel bypass loop is above a set temperature threshold then to resist switching over from the diesel supply system to the mixed fuel supply system; the controller is configured to monitor the supply temperature of the diesel and if the supply temperature of the diesel is above a set temperature threshold then to resist change over to the mixed fuel supply system.
PCT/AU2011/000456 2010-04-20 2011-04-20 A dual fuel supply system for a direct-injection system of a diesel engine with off-board mixing WO2011130792A1 (en)

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