1. Field of Invention
The present invention relates to fuel injection in general and in particular to a method and apparatus for the injection of liquid and gaseous fuels directly into the combustion chamber of an engine.
2. Description of Related Art
The book, The Modern Diesel Engine, (Geoffrey Smith, Ed., Ilife and Sons Ltd, London, 1942) describes the most advanced practical and experimental diesel engine technology up to about 1942. The Ricardo Comet, Lanova air-cell and Acro air-cell systems use a small side chamber connected to the main combustion chamber by a small passage. When the piston moves down, the high pressure gases stored in the side chamber rush through the passage to the main chamber, creating a high-velocity jet that may be used for atomization and mixing of the jet. Cummins Engine Co. produced engines in the 1930's with an air-cell in the piston, which produced an air jet aimed directly at the fuel injector, supposedly improving the air supply to the burning fuel.
U.S. Pat. No. 6,564,770 B1, May 2003 (Geoffrey Cathcart, assigned to Orbital Engine Company) discloses a “Method of Injection of a Fuel-Gas Mixture to an Engine”. This patent is directed to co-injection of air and liquid fuel (typically gasoline) into a direct-injection spark ignition engine. By injecting air with the fuel, it is possible to prevent the over-rich regions that would lead to high emissions. The core of the invention seems to be the use of multiple injection events, combined with the air injection, to achieve a desirable fuel-air mixture prior to ignition. The embodiments discussed refer to a spark ignition engine. This patent teaches the trapping of cylinder gases (as opposed to using a compressed air source) for later use in atomizing the fuel.
U.S. Pat. No. 6,427,660 B1 Aug. 6, 2002 to Yang (assigned to Ford Global Technologies) titled “Dual Fuel Compression Ignition Engine” disclosed the use of low-pressure (15-45 bar) natural gas and diesel co-injection, typically injected prior to top-dead center to operate in a stratified, mostly premixed combustion mode. Split injections are possible depending on the load. The injector incorporates a mixing-chamber into which diesel is injected through a first valve and sits in the chamber until the gaseous fuel valve opens and the gaseous fuel atomizes the diesel and the whole mixture is injected into the combustion chamber. The fact that the gaseous fuel is at moderately low pressure precludes the possibility of late-cycle gaseous fuel injection (peak cylinder pressures in some engines can approach 100 bar). High gaseous fuel pressure (>250 bar) can be a critical part of maintaining high-efficiency and low emissions with exhaust gas recirculation (EGR).
U.S. Pat. No. 5,067,467 November 1991 to Hill et al. (originally assigned to the University of British Columbia) titled “Intensifier-Injector for Gaseous Fuel for Positive Displacement Engines” discloses the idea of using natural gas to continuously atomize diesel in a prechamber without control of the relative timing for liquid pilot and gaseous fuels (i.e., there is no means taught for controlling the liquid/gaseous fuel mass ratio and there is no teaching of anything about metering the liquid fuel or anything about injection phasing). The apparatus described uses a poppet valve injector and the method is described as “gas blast” atomization.
U.S. Pat. No. 6,598,584 B2 Jul. 29, 2003 to Beck et al. (Clean Air Partners Inc.) titled “Gas-Fueled, Compression Ignition Engine with Maximized Pilot Ignition Intensity” relates to pilot-ignition of a premixed natural gas/air charge (commonly referred to as fumigation), the basic concept of which is very old—all the major engine companies have tried variations of this sort. The key novelty disclosed in this patent appears to be the concept of injecting the pilot for a period shorter than the ignition delay or the “mixing time”. Presumably this results in more widespread ignition of the premixed charge and lower emissions. The patent describes in detail the importance of a particular injector geometry (interference angles for the needle-seat seal).
U.S. Pat. No. 6,073,862 Jun. 13, 2000 to Touchette et al., (Westport Research) “Gaseous and Liquid Fuel Injector” includes a detailed review of prior art, including the work of Miyake et al. 1987, who describe a single injector with two concentric needles injecting pilot and high-pressure gaseous fuel through separate holes.
U.S. Pat. No. 4,414,229 Nov. 22, 1983 to Wood (assigned to Southwest Research) “Fuel Injection System for Diesel Engines” describes a dual-fuel injector for liquid fuels. As in the other co-injectors reviewed here, the diesel fuel (pilot) is introduced into a chamber in the injector prior to lifting the needle with the pressure of the second fuel. The concept of injecting the pilot first is discussed with respect to efficient ignition. This invention cannot work for a main injection of gaseous fuel because the needle is actuated by an increase in pressure of the alternative fuel. Fuel injectors cannot be actuated rapidly enough by changes in gaseous fuel pressure because gaseous fuel is so compressible. Also, it appears that the intention is to create a “charge” of diesel fuel (DF) below the alternative fuel (AF) which is all injected essentially sequentially (DF first) when the needle is lifted. There seems to be no way of limiting the DF/AF mass ratio during the early part of the injection.
U.S. Pat. No. 4,742,801 May 10, 1988, to Kelgard “Dual Fuel Mobil Engine System” discloses a system for burning gaseous fuels or liquefied petroleum gas (e.g. propane, LPG) in a diesel engine with a pilot diesel engine using separate injectors for the diesel and gaseous fuel.
U.S. Pat. No. 6,484,699 to Paul et al. teaches a “universal fuel injector” for automatically switching from injecting a combination of two fuels or one fuel when the second fuel is not available. For example, if the second fuel is a gaseous fuel, liquid fuel is introduced through one connection and gaseous fuel is introduced through a different connector. While the '699 patent discloses a liquid fuel distributor, it does not teach anything about metering the liquid fuel or anything about injection phasing.
US 2006/0086825 Application to Date et al. filed 24 Oct. 2005 discloses a fuel injector that co-injects gaseous and liquid fuels. The liquid fuel assists with combustion and lubricates the needle at sliding interfaces and where the needle tip impacts against the seat. The application provides no guidance on how to achieve desirable (or even operable) mass ratios of liquid fuel to gaseous fuel during injections.
The present invention relates to a fuel injector capable of injecting an ignition-promoting liquid fuel (henceforth, simply “liquid”) and a high-pressure gaseous fuel (henceforth, simply “gas”) in an internal combustion engine. The invention pertains specifically to an injector in which both liquid and gas are injected into the combustion chamber through the same injection hole(s).
The present invention also relates to a method and apparatus for operating an internal combustion engine using a combustible gas under pressure in combination with a controlled quantity of a liquid igniter fuel wherein the controlled quantity of liquid is carried into a combustion chamber and atomized by the flow of gas to the combustion chamber. The liquid can contain additives to reduce exhaust emissions (such as water, alcohols and biodiesel), while the gas can be any blend of hydrocarbons and hydrogen that can be combusted in the combustion chamber, such, as, for example, natural gas, syngas, biogas and mixtures thereof. As found in the recited examples, the gas can also comprise non-reactive gases.
The liquid start of injection can be slightly delayed from the gas start of injection, in order to control atomization and emissions. The injector is capable of delivering at least a certain minimum liquid/gas mass ratio during the initial part of the injection. Liquid injected during the middle and end of the injection is undesirable. If the initial liquid/gas mass ratio is too high, then liquid atomization can be poor, leading to excessive exhaust emissions. If multiple injections are used for each combustion cycle, then the first injection should have the highest liquid/gas mass ratio. Controlling the liquid/gas mass ratio in the initial part of the injection is an important objective of the method and apparatus described below, not taught in the prior art.
The present injector introduces the liquid into an accelerating gas stream within the body of the injector to entrain the liquid within the gas for atomization of the liquid as the mixture is injected into the combustion chamber.
Single-Actuator Embodiments
Liquid fuel can be metered into the injector by means of a control orifice and a regulated liquid/gas pressure differential, which can be made a function of engine speed. In some embodiments, the liquid fuel flow is further limited by the movement of the needle, which can open or close liquid flow passages in addition to performing its primary function of controlling fuel injection into the engine combustion chamber.
Dual-Actuator Embodiments
Liquid fuel can be metered into the injector at controllable times using a second movable needle inside the main needle, an external control valve (such as solenoid, piezo), or an external distributor pump of the sort found on many diesel engines.
Accordingly, there is provided a method for concurrently injecting a liquid fuel and a gaseous fuel directly into a combustion chamber of an internal combustion engine, the method comprising:
In a further aspect, there is provided a fuel injector for concurrently injecting a liquid fuel and a gaseous fuel directly into a combustion chamber of an internal combustion engine, the fuel injector comprising:
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
In drawings which illustrate embodiments of the invention,
a is a cross sectional view of an injector according to a further embodiment of the present invention having a simple on/off control valve.
b is a cross-sectional view of an injector according to the embodiment of
Single-Actuator Apparatus
Referring to
The fuel injector includes injector body 10 having injection holes or orifices 14 at a first end 16 thereof. Injector body 10 includes central cavity 18 formed by cavity wall 24 and includes slidable needle 20 therein. At a lower portion of central cavity 18, needle 20 forms lower chamber 22, which serves as a plenum or small accumulator, annularly disposed between needle 20 and cavity wall 24. The lower chamber includes tapered end 25 at first end 16 of the injector wherein injection holes 14 allow the combustion chamber of an internal combustion engine (not shown) to be in fluidic communication with tapered end 25 of the lower chamber when needle 20 is lifted from seat 34. The lower chamber further communicates with gas inlet port 27 operable to supply the lower chamber with a quantity of gaseous fuel from a fuel compressor, common rail or other conventional manner. At upper portion 28 of central cavity 18 needle 20 is in slidable and sealable communication with cavity wall 24.
Needle 20 comprises a substantially cylindrical body having exterior wall 21 and includes a central liquid passage 30 which is shown in this embodiment as a bore formed within needle 20. The lower end of the needle is shaped to provide a sealing surface that can be pressed against tapered end 25 of the lower chamber so as to seal lower chamber 22 when the needle is commanded to a closed position. The position of the seal (or “seat”) is shown at 34. The needle includes a plurality of exit bores 39 extending radially from passage 30 to lower chamber 22 above needle seat 34.
The upper end of needle 20 comprises a substantially planar end surface perpendicular to the axis of needle 20. Upper chamber 40 is formed in the injector body above the needle. The upper chamber includes spring 44 positioned and oriented to urge needle 20 out of upper chamber 40 towards seat 34 (the “closed position”). The upper chamber further includes inlet port 46 to supply the upper chamber with a hydraulic fluid and outlet port 48 to relieve the upper chamber of hydraulic fluid. As shown in the embodiment of
Control valve 60 which includes liquid supply line 62, plunger 64 and actuator 66 is provided to control the flow of liquid to the injector. In the embodiment of
Between injections, control valve 60 is in a “closed” position, which connects upper chamber 40 to high-pressure liquid supply line 62. Spring 44 and the pressure of the liquid in upper chamber 40 keep needle 20 in the closed position, sealing lower chamber 22 and passage 30 from the combustion chamber. The liquid is prevented from flowing through exit bores 39 because control valve 60 is “closed” so liquid can not flow from liquid supply line 62 to passage 30.
At the command-start-of-injection (CSOI), which can be received from an engine management computer, mechanical or other known means, actuator 66 of control valve 60 lifts valve plunger 64, which disconnects upper chamber 40 from liquid supply line 62 and connects liquid inlet port 52 for passage 30 of needle 20 to the high-pressure liquid supply line. Liquid then flows through passage 30 to exit bores 39 as needle 20 is lifted from seat 34 at a rate determined by orifice 72 at liquid outlet port 48. From outlet port 48, the liquid can return to the liquid tank (not shown). When needle 20 is lifted from seat 34, gas flow is initiated and begins to flow through gas inlet port 27 into lower chamber 22 and out of injector orifices 14, entraining and atomizing the liquid to create a mixed fuel injection charge. The quantity of liquid injected is limited by how much liquid flows through middle chamber 57 before needle 20 rises fully and upper seat 56 contacts surface 58, thereby blocking the supply of further liquid.
At the end of injection, control valve 60 returns to the closed position, which is the position associated with when valve plunger 64 again connects upper chamber 40 with high-pressure liquid supply line 62 and blocks flow to liquid inlet port 52. Re-establishment of pressure in upper chamber 40 causes needle 20 is move downwardly. As needle 20 moves downwardly toward seat 34, upper seat 56 no-longer blocks the liquid flow to the needle passages, but liquid flow is instead blocked by valve plunger 64. Thus, the liquid/gas mass ratio is large at the beginning of an injection event, but very low at the middle and end of the injection event.
The pressure differential that drives the liquid flow arises because:
By virtue of the arrangement of injection orifices 14, and the regulation of liquid flow to passage 30, liquid does not collect within the injector passage for gas flow through the injector, but is continuously atomized. Similarly, exit bores 39 from passage 30 can also be positioned to enhance the operation of the invention i.e., for improved operation they should be adjacent to and immediately upstream of the contact line or seal 34. It is believed that if the liquid is injected into a gas flow with sufficiently high velocity, it will be carried out almost immediately and not pool in lower chamber 22. Excessive pooling of the liquid would not be desirable because it could reduce the ability to control the timing of the liquid injection. Accumulated liquid could lead to poor atomization, particularly near the end of the gas injection.
The operation of the fuel injector of
The fluid resistances imparted by the small orifices are dynamic and the pressure drop across these orifices varies in a complex way with the transient flows. However, for the sake of describing the function of the disclosed injector, they can be treated as simple resistances giving a linear relation between flow and pressure. The resistances are:
When needle 20 is seated and control valve 70 is open, upper chamber 40 and middle chamber 57 are pressurized by liquid flowing from liquid supply line 62.
Pup=Pmid=RD/(RD+RS)PL
The resistances should be chosen so that Pmid˜PG so that there is no significant flow into the gas passages. An additional check valve (not shown) between orifice 79 and chamber 57 can prevent backflow of gas in the event that Pmid<PG. Exit bores 39 are partially blocked at the bottom of needle 20, but there is not a tight seal.
When control valve 70 closes, Pup approaches PD at a rate set by RD thereby reducing the downward closing force acting on needle 20. Pmid˜PL but needle 20 starts to lift because of the reduced closing force and this restricts liquid flow through chamber 57 as shoulder 56 rises to meet contact seal 58. When needle 20 starts to lift from seat 34 liquid is injected with gas through orifices 14.
When needle 20 rises to the position of maximum lift, liquid flow is shut off by shoulder 56 engaging contact seal 58, even though the pressure remains above PG.
At the command end of injection, control valve 70 opens, so Pup and Pmid return to near PG. Very little liquid is injected as needle 20 moves downwardly because the pressure differential is very small.
b shows a preferred arrangement of the second embodiment in which the various components are arranged in a manner closer to the anticipated actual construction.
Referring now to
The contact between cap 144 and plunger 142 is due to the balance of forces. The injector includes upper chamber 146 which is supplied with liquid from supply line 62. Orifice 148, which is located between upper chamber 146 and supply line 62, throttles the liquid flow to upper chamber 146. The liquid is also supplied through check valve 152 to liquid inlet port 52 in the side wall of the injector which is in fluidic communication with annular groove 50 in needle 20. Groove 50 is connected by radial passages 53 to central passage 140.
Like in the other disclosed embodiments, gaseous fuel is supplied from gas supply passage 27 to lower chamber 22, provided in the nozzle of the injector.
When control valve 70 opens, the pressure in upper chamber 146 falls, and needle 20 lifts from seat 34. Liquid inside passage 140 of needle 20 is forced through liquid exit bores 39 near the bottom of needle 20 into the gaseous fuel flowing through lower chamber 22 and out through the nozzle orifices. This provides most of the liquid flow at the preferred time when needle 20 is rising. Check-valve 152 ensures the liquid injection quantity is proportionate to the stroke of needle 20. If control valve 70 is now closed, the upper chamber 146 pressure rises, forcing needle 20 down with the aid of spring 44. When pressure inside passage 140 falls to below the liquid supply pressure, check valve 152 allows liquid to refill needle passage 140.
The rise and fall rates of the needle are determined mainly by the sizes of supply and drain orifices 148 and 154, respectively which can be adjustable during service, for example, by substituting an orifice of one size for another orifice of a different size. The liquid supply pressure at 62 can be adjusted during operation in response to operating conditions. The pressure at drain 150 can also be adjusted during operation. The stroke of needle 20 can be adjusted by the position of cap 144 and/or by adding or removing shims in upper chamber 146.
(General Flow Description and Further Single-Actuator Embodiments)
In the embodiments shown in
Turning now to
The injector system of
Before discussing more specific embodiments, some general operational features should be noted.
Turning now to
The key to this embodiment is that liquid pressure at supply line 62 is controlled above gas pressure at line 27, so the liquid flow into passage 30 is regulated by resistance 79 (which can be placed inside the injector body or needle). The other important aspect of this embodiment is that once gas flow is established, a pressure differential between upper passages 37 and lower passages 39 drives gas into core passages 30, flushing liquid out of the needle and into the gas flow during the early part of injection events.
Dual-Actuator Apparatus
Greater control of the liquid and gas mass ratio during the injection event can be achieved by using 2 actuators.
Turning to
In another embodiment, the liquid flow can be controlled by a mechanical, distributor pump of the type found on many small diesel engines. These pumps are designed to provide metered quantities of liquid fuel at variable timing, with a separate line to each injector. In this embodiment, the gas injection is controlled by a direct actuator, and the liquid injection by the separate liquid pump. The injector can appear identical to that of
Operation
Now referring to
The heart of the method is phasing the liquid and gas injections in the appropriate way. With the disclosed method the initial injection is enriched in liquid to encourage rapid ignition, but little or no liquid is injected late in the injection event, which is desirable because later injected liquid fuel can cause higher emissions. If a constant liquid/gas mass ratio is provided throughout the injection event, because of the ignition requirements at the beginning of the injection event, overall demand for liquid, by mass, would be higher than needed—greatly decreasing the utility of an engine fuelled with liquid and gas, which is aimed at increasing the amount of gaseous fuel burned to reduce emissions from a compression ignition engine.
Small quantities of liquid can be injected just before the first gas leaves the injector, but this relative advancement of the liquid should be small enough so that the gas can overtake the liquid spray in the combustion chamber, promoting atomization.
Generally the total mass of liquid injected can be up to about 50% of the total mass of gas injected, with the exact mass ratio of gas and diesel depending on load and the ignition characteristics of the liquid and gaseous fuels. Over the entire operating range of an engine, an engine using one of the disclosed methods and apparatus can normally operate with the liquid fuel being a much lower mass percentage than 33% of the total fuel injected. The mass percentage of liquid fuel is generally in the higher end of the normal operating range when only very small quantities of fuel are needed, for example when the engine is idling or under low load, since a minimum of liquid fuel is generally needed to assist with ignition of the gaseous fuel.
With the present invention particular (different) phasing of the gas and diesel co-injection can be used to minimize emissions for mostly non-premixed combustion. The relative phasing of the injections is discussed above.
The illustrated preferred embodiments of the fuel injector employ an inward lifting needle with a multi-hole nozzle tip through which the gaseous and liquid fuel can be concurrently injected into the combustion chamber. These preferred embodiments can deliver suitable fuel distribution within the combustion chamber which is important for reducing emissions and improving engine performance and combustion efficiency. However, the disclosed method can also be employed with a poppet-style injector which has an outward lifting valve needle. The disclosed methods for metering the liquid fuel and controlling the timing for dispensing liquid fuel can be adapted to a poppet-style injector as shown in
In preferred embodiments, the liquid fuel of the present invention is a liquid fuel with a lower auto-ignition temperature compared to the gas, for example including but not limited to diesel, synthetic diesel, DME (dimethyl ether), biodiesel, straight vegetable oil and water emulsions of any of these. The liquid can be used to initiate the combustion within the combustion chamber of an ignition compression engine. The various embodiments of the present invention allow entrainment of the liquid fuel within the gaseous fuel inside the injector to assist with atomization of the liquid fuel on injection into the combustion chamber of the engine. Such gas-blasted atomization of the liquid fuel can aid in the use of relatively unrefined liquid fuels, such as for example, straight vegetable oil.
The gaseous fuel can include, but is not limited to natural gas, syngas, biogas, hydrogen, and blends thereof. The gaseous fuel can have an auto ignition temperature higher than that of the liquid fuel and can comprise the majority of the combustion reaction within the combustion chamber after combustion is initiated by the liquid fuel
A number of variations of the injector can be utilized, such as:
The following provides a list of features and/or advantageous that can be available when practicing the present invention and or applications to which or by which the present invention can be applied:
While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.
This application is a National Stage of International Application No. PCT/CA2007/001175 filed Jun. 29, 2007 and which claims the benefit of U.S. Provisional Application No. 60/817,079, filed Jun. 29, 2006, the disclosures of all applications being incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CA2007/001175 | 6/29/2007 | WO | 00 | 2/19/2010 |
Publishing Document | Publishing Date | Country | Kind |
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WO2008/000095 | 1/3/2008 | WO | A |
Number | Name | Date | Kind |
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5549083 | Feuling | Aug 1996 | A |
5775282 | Smith | Jul 1998 | A |
6073862 | Touchette et al. | Jun 2000 | A |
6439192 | Ouellette et al. | Aug 2002 | B1 |
6761325 | Baker et al. | Jul 2004 | B2 |
7373931 | Lennox et al. | May 2008 | B2 |
7861696 | Lund | Jan 2011 | B2 |
8166956 | Ulrey et al. | May 2012 | B2 |
20080245318 | Kuroki et al. | Oct 2008 | A1 |
Number | Date | Country |
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2 532 775 | Oct 2006 | CA |
0 872 634 | Oct 1998 | EP |
Number | Date | Country | |
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20100199948 A1 | Aug 2010 | US |
Number | Date | Country | |
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60817079 | Jun 2006 | US |