WO2004036035A1

WO2004036035A1 - Fuel feeding system

Info

Publication number: WO2004036035A1
Application number: PCT/FI2003/000760
Authority: WO
Inventors: Jukka Lillbacka; Jaakko Salakari
Original assignee: J & J Prowork Oy
Priority date: 2002-10-15
Filing date: 2003-10-14
Publication date: 2004-04-29
Also published as: FI20021830A0; FI20021830A; AU2003268990A1

Abstract

A fuel feed System is disclosed for use in an apparatus, wherein at least one substance is fed in conjunction with the fuel induction via an intake valve, whereby the system in an internal combustion engine, for instance, comprises fuel injection channels made in the valve seat. The valve train is adapted to cover and uncover simultaneously both the intake of combustion air or combustible fuel gas and the injection of fuel into the combustion space of an engine or a pulsed gas burner. The fuel is injected via fuel injection channels machined through the valve seat and thus the fuel is mixed with the intake air or combustible gas in the inlet port uncovered as the valve opens.

Description

Fuel feeding system

The present invention relates to a fuel feed system according to the preamble of claim 1 for feeding fuel or the like flowable material in a combustion engine, meter- ing system, mixing device or the like equipment in which into a large volumetric flow of one material must be mixed a second material.

In many types of multicycle engines and other combustion processes unrelated to engines, fuel is mixed with the combustion air or, alternatively, combustion air and fuel are fed together into a cylinder or combustion space. Obviously, the goal is to achieve fast and complete mixing of fuel with the combustion air before the combustion process is initiated in order to obtain maximally effective and complete combustion. A further goal is to provide easy control ofthe fuel-combustion air ratio. The The need for control is most pronounced for engines, such as vehicle engines, operated at varying power levels.

In a combustion engine operated in the prior-art fashion, fuel is conventionally first fed into a carburetor in which the fuel is evaporated into the intake air, whereupon the fuel together with the intake air travels under the vacuum induced by the piston down-stroke into the cylinder whereupon the mixture is spark-ignited. This type of process is called the Otto engine. In a diesel engine, the fuel is injected from an injector into the combustion space when the compression cycle is close to the top dead center position ofthe piston, whereby the fuel is ignited under the elevated combustion air temperature induced by the high compression pressure. In this fashion, the diesel engine avails of its higher compression ratio that gives superior efficiency to this engine type.

Fuel injection directly into the combustion space has also been adopted to later types of gasoline-fueled Otto-cycle-type internal combustion engines. Gas-fueled engines running on methane or reform process gas have been available for some time in both Otto cycle and specifically modified diesel cycle versions. Mixing the fuel with the intake air has always been problematic, particulary in conjunction with liquid fuels. This is because liquid fuel is metered as discrete droplets into a gaseous medium, generally air, with the result that the combustible mixture is comprised of two different phases. When using a carburetor, the fuel is mixed directly with the intake air flow, while in a fuel injection system the fuel is atomized into droplets at the injector tip under the high ejection velocity imparted by the line pressure ofthe fuel injection system. For improved atomization, the trend has been to use ever higher fuel feed line pressures. The maximum size of droplets ejected from the injection valve can be computed from the following equation:

0.75(σ/p)°° ε^" ^•0.4

where σ = surface tension of injected liquid, p = density of injected liquid, and ε = dissipation rate of turbulent kinetic energy per unit volume wherein droplets are being atomized.

In an injector, the variable ε representing the rate of energy per unit volume is directly proportional to the differential pressure at the injector tip or, respectively, to the square of injection velocity (according to the equation proposed by Hinze and Clay). Hence, reduction of droplet size is directly related to the use of a higher injection pressure. As to the surface tension, this parameter of a given liquid fuel is dependent on the temperature so that the surface tension is reduced at an elevated temperature.

Furthermore, the rate of a chemical reaction between two phases is directly proportional to the interactive area of chemical reaction between the two phases that in turn is inversely proportional to the size ofthe reacting droplet. More precisely, a small droplet size promotes the combustion reaction while preheating ofthe fuel in turn reduces the droplet size. In the recent years, multivalve constructions have been adopted in spark-ignited combustion engines, whereby the cylinder head typically has two intake and two exhaust valves. While this arrangement improves the breathing efficiency ofthe engine, it also crams the cylinder head so that it becomes difficult to locate other elements such as fuel injectors or a second spark plug therein.

Over the years, plural different attempts have been made to improve the mixing of fuel with combustion air. One of these is the swirl chamber technique, wherein the combustion air and the fuel are introduced into the combustion space in a fashion that induces a swirl motion in the combustible mixture. The desired swirl effect is accomplished by proper contouring ofthe piston top surface or other arrangements inducing swirl and, in certain cases, modifications made in the construction ofthe inlet manifold. Diesel engines have been provided with a so-called precombustion chamber that precedes the actual combustion space. In a precombustion chamber diesel engine, the fuel is injected by the pressure ofthe fuel pump into the precombustion chamber generally equipped with a glow plug to secure reliable cold starts. While a small portion ofthe combustion air is mixed with the fuel in the precombustion chamber, the burning ofthe fuel is continued in the actual combustion space, that is, in the cylinder. In gasoline-fueled engines equipped with fuel injection, the fuel can be metered from a single injector or the injectors of a multiport system. In the prior art, injection has invariably taken place into the intake manifold in front of the intake valve. This arrangement provides more accurate fuel mixing and metering than what can be achieved by means of a carburetor. In later systems ofthe art, also direct injection of fuel into the cylinder space has been implemented (e.g., by Mitsubishi). Direct injection of gasoline has been limited by the material durability problems of injection pumps inasmuch as gasoline is not a self-lubricating medium in contrast to diesel fuel which acts to a certain degree as a lubricant. Today, the newest fuel blending technology complements both diesel fuel and gasoline with lubricating additives, generally fatty acid esters and the like compounds, in concentrations ranging from 200 to 1000 ppm. Direct injection of fuel into the cylinder provides plural benefits such as more accurate fuel metering and the possibility of forming a zone of rich mixture, e.g., at the spark plug, in order to obtain secure ignition, whereby the average composition ofthe mixture to be combusted in the cylinder can be leaner than that ofthe ideal stoichiometric fuel-air ratio. As a result, fuel consumption can be reduced particularly at partial loads.

Mixing of fuel with air and swirling induction have been discussed in plurality of patent publications of which, e.g., US Pat. No. 6,443,124 discloses an arrangement wherein a portion of intake air is allowed to flow into the cylinder on the downstream side ofthe throttle valve, whereby the combination ofthe two airstreams causes swirling.

US Pat. No. 6,439,482 in turn discloses a fuel injection system having the intake manifold equipped in a space downstream ofthe fuel injection point with a swirl groove or plural swirl grooves serving to improve the mixing ofthe fuel-air mixture before it is passed to the cylinder.

US Pat. No. 5,707,012 describes a fuel injection system wherein fuel and air are mixed by a atomizing sieve before the combustible mixture enters the cylinder.

Grooves, constrictions and sieves designed into the intake manifold involve the shortcoming of increasing the flow resistance whereby the flow velocity is reduced and, thus, maximum available output power is curtailed. Hence, the benefit of improved mixing is at least partially lost with the increasing flow resistance.

A typical modern combustion engine involves a lot of electronics, magnetic valves and sensors, whereby the sensors detect the fuel-air ratio and then adjust it appropriately by controlling the magnetic valves. In this manner, such factors as air temperature, output power demand and other variables are taken into account so as to achieve maximally complete combustion.

It is an object ofthe present invention to provide a fuel injection system for an internal combustion engine or the like apparatus, which includes a space that can be closed by a valve so as to accommodate feeding therein at least two flowable substances, whereby the present injection system offers a simple way of effective infeed of such substances and simultaneous mixing thereof with each other.

The invention is based on machining into the intake valve seat ofthe apparatus being operated at least one channel opening serving as the fuel injector orifice.

The apparatus being operated is advantageously an internal combustion engine and intake valve is a seated disc valve.

More specifically, the fuel feed system in accordance with the invention is character-, ized by what is stated in the characterizing part of claim 1.

The invention offers significant benefits.

By virtue ofthe present invention, the fuel is injected to the cylinder at the point where the flow velocity and, hence, the dissipation of kinetic energy per unit volume is highest. Obviously, this location can be found at the point of maximum velocity of the gaseous intake medium, that is, the uncovered port ofthe gas inlet valve. Due to the high flow velocity at this point, mixing takes place effectively. According to the present invention, the fuel, whether gaseous or liquid, is injected via orifice channels which are drilled through the valve seat in such positions that the orifice channels are uncovered only when the inlet valve itself opens and, conversely, shutting the inlet valve also covers the orifice channels. This arrangement provides at the same time correct synchronization of fuel injection during the induction stroke as well as timed valve function for the fuel injector orifices. Thus, the opening valve automatically triggers fuel injection and, respectively, shuts off fuel flow from the injector orifice. Mixing, ignition and combustion are improved as the fuel becomes preheated in the valve seat. Fuel preheating is particularly advantageous in the injection of diesel fuels and other materials difficult to mix and ignite.

While the above outlined fuel feed system in accordance with the present invention is most advantageously suited for use in combustion systems ignited by means of a spark plug, it may as well be applied to systems using two different fuels in a high- compression process known as a modified diesel cycle. Particularly advantageously the present system can be applied to equipment burning a gaseous or easily gasifiable fuel.

The orifice channels made to the valve seat can be at least partially directed so that some ofthe orifices direct the fuel spray toward the spark plug while the other orifices align some ofthe fuel sprays counter to the intake air flow, advantageously at an angle of 45° to 90°. By way of thus directing a portion ofthe fuel to a spark plug, the rich mixture advantageously promoting ignition can be concentrated in a close vicinity ofthe spark plug, whereby all the mixture in the cylinder ignites easier. The fuel channels made to the valve seat may also merge into a contiguous annular injection channel with a hemispherical or U-shaped form that exits toward the valve disc. This arrangement assures smooth distribution ofthe fuel flow into the intake air flow.

In the following, the invention is examined in more detail with the help ofthe appended drawings, wherein

FIG. 1 shows a first embodiment ofthe invention;

FIG. 2 shows a second embodiment ofthe invention;

FIG. 3 shows a third embodiment ofthe invention;

FIG. 4 shows a fourth embodiment ofthe invention; and

FIG. 5 shows a fifth embodiment ofthe invention.

In the embodiments described in the following, the fuel feed channels are formed into a separate valve seat element. This arrangement is the best alternative as to the fabrication ofthe fuel feed channels and servicing of cylinder heads. Obviously, the invention may also be adapted to a cylinder head not having mounted therein separate valve seat rings but rather having the valve seat surface directly machined on the cylinder head.

Referring to FIG. 1, the fuel injection system shown therein comprises a cylinder head having mounted thereon a valve seat 2, a portion of which forms a rotationally symmetrical port accommodating a disc valve 4. The conical portion 14 of valve seat 2 together with the compatibly shaped conical rear surface 15 of valve 4 provide the sealing surfaces 14, 15 that shut off intake flow in the inlet port 6 at the closure ofthe valve when the valve disc meets the sealing surface 14 of valve seat 2. Valve 4 is actuated by the engine's valve control means. Orifice channels 3 via which the fuel is injected are drilled to the valve seat 2 so that each one ofthe channels is aligned perpendicular to the conical sealing surface 14. The orifice channels 3 begin from an annular distribution manifold 5 that houses a fuel infeed channel 1 connecting orifice channels 3 with each other. The orifice channels made to the valve seat may be at least partially directed so that some ofthe orifices direct the fuel spray toward the spark plug while the other orifices align some ofthe fuel sprays counter to the intake air flow, advantageously at an angle of 45° to 90°. The fuel injecting orifice channels 3 made to valve seat 2 may also merge in the fashion shown in FIG. 2 into a contiguous annular injection channel 7 with a hemispherical or U-shaped form exiting toward the sealing surface 15 ofthe rear surface of valve 4. This arrangement assures smooth distribution ofthe fuel flow into the intake air flow.

During operation, fuel first enters an annular fuel distribution manifold 5 wherefrom the fuel propelled by the fuel infeed line pressure travels along the orifice channels 3 machined to the valve seat 2 and finally is ejected into the intake air flow in the intake port 6 flaring into the combustion chamber as the port between valve seat 3 and disk valve 4 when valve 4 is driven open. In FIG. 2 the orifice channels are shown exiting into an annular injection channel 7 that is covered when valve 4 is driven closed. Referring to FIG. 3, the valve movement may also open an auxiliary valve 8 ofthe fuel infeed line that thus performs automatic timing of fuel injection, whereby fuel injection is controlled by two separate valves as shown in the diagram. The auxiliary valve 8 is pushed open by a valve stem projection 9 acting via an intermediate element 10 thus directly synchronizing the instant of fuel injection with the opening ofthe valve. Obviously, other technical arrangements selected from the plural possibilities can be used as well. Particularly in devices and motors equipped with electronic control systems, plural different techniques are available for steering the fuel infeed line pressure and open/close timing of valves. The auxiliary valve may be arranged to open simultaneously with the disc valve or at a delay or in advance thereto.

If the operated apparatus is a four-stroke combustion engine, prior to entering the valve seat orifice channels, the fuel can be passed via a preheating device located in an exhaust gas duct or other point utilizing the heat content of exhaust gases prior to or after a possible turbocharger of intake air. While the fuel obviously will heat up also in the orifice channels, the retention time of fuel herein remains very short thus possibly needing more effective preheating. In FIG. 4 is illustrated a heat exchanger 11, wherein exchaust gases 12 preheat the fuel that subsequently enters the orifice channels ofthe valve seat via an annular channel 5.

Advantageously, plural orifice channels are employed and they may be aligned in different direction in regard to each other. In a propane-fueled apparatus, for instance, having a 40 mm dia. inlet valve, the number of orifice channels is 13 with an overall cross-sectional orifice area of 10 mm . As a rule, the system is advantageously implemented using a plurality of small-diameter orifice channels. Obviously, the properties ofthe substance being fed sets some limits to the minimum diameter ofthe orifice channel.

In a two-stroke engine, the present valve arrangement can be utilized particularly advantageously when the two-stroke engine is turbo/supercharged. This kind of construction is shown in FIG. 5. As shown in FIG. 5, the valve opens the inlet port of intake air and fuel flow at the same time as the engine piston starts its upward motion, whereby the turbo/supercharged intake air pressure cannot hinder the engine function during its other stroke phases. The fuel infeed line is connected to point 1 and, advantageously, the turbo/supercharged intake air enters via port 13.

In addition to those described above, the invention may have alternative embodiments.

Obviously, the above-described intake valve and fuel injection arrangement may be adapted to applications different from a four-stroke engine. Such applications can be found, e.g., in pulsed gas burners and propulsion devices based on pulsed operation. Pulsed burners are, e.g., in the USA employed for heating water boilers. The valve arrangement in accordance with the present invention is also particularly applicable to a twό-stroke engine inasmuch as, contrary to the prior art, the fuel is always mixed with fresh intake air instead of using piston-ported induction from the crankcase that today is conventional in two-stroke engines.

Furthermore, the present invention makes it possible to implement a construction wherein via the seat of an inlet valve are fed two different fuels such as a gas and a difficult-to-ignite heavy oil grade. Herein, the valve seat is adapted to inject the different fuels from separate sets of orifice channels or the fuels are fed via separate annular channels feeding the separate sets of orifice channels, whereby the number of the annular feed channels can be two, for instance.

Inasmuch as the substance to be fed via the valve arrangement and the valve seat in accordance with our invention may be different from the substance entering via the uncovered port ofthe valve, the invention may also be utilized to implement a cost- effective mixing/metering device. Such a mixing/metering device finds use in, e.g., process technology and chemical applications to replace, e.g., a dosing pump or other device used for metering and mixing two different flows of substances with each other.

Claims

What is claimed is:

1. A fuel feed system comprising

- at least one valve (4), - an intake port (6) leading to said valve for a first substance,

- at least one sealing surface (14) against which said valve (4) is adapted to seat when the valve is in its closed position, and

- at least one orifice channel (3) exiting on the sealing surface (14) for passing at least one second substance into said intake port (6) of said first substance, said intake port (6) of said first substance opening simultaneously as said orifice channel (3) becomes uncovered with the opening of said valve and closing with the closing of said valve, characterized in that at least some of said orifice channels (3) are directed toward an igniting device such as a spark plug.

2. The fuel feed system of claim 1, characterized in that the injector ends of said orifice channels (3) exiting on said sealing surface (14) are connected to each other by an annular channel (7) that exits toward the rim ofthe disc valve, is adapted to receive said second substance from a plurality of said orifice channels and has such an annular shape which is entirely covered when the disc of valve (4) is in its closed positition.

3. The fuel feed system of claim 1, characterized by an auxiliary valve (11) adapted to open/close in synchronism with the movements ofthe valve train and located upstream ofthe orifice channels, whereby fuel injection is controlled by two separate valves that may be arranged to open simultaneously with the disc valve or at a delay or in advance thereto.

4. The fuel feed system of any one of foregoing claims, characterized by a heat exchanger serving to preheat said second substance and located to operate upstream ofthe orifice channels.

5. The fuel feed system of any one of foregoing claims, characterized by a first set of orifice channels for injection of a second substance and a second set of orifice channels for injection of a third substance thus facilitating the injection of two different fuels via the separate sets of orifice channels or via separate annular channels feeding the separate sets of orifice channels.

6. The fuel feed system of any one of foreging claims, characterized in that said orifice channels are made in said valve seat (2).

7. The fuel feed system of any of claims 1 or 6, characterized in that valve (4) is a disc valve (4) and the mating valve seat (2) respectively has a rotationally symmetrical shape.