GB1596340A

GB1596340A - Fuel metering and distribution

Info

Publication number: GB1596340A
Application number: GB24064/78A
Authority: GB
Original assignee: Dresser Investments; Dresser Inventments NV
Current assignee: Dresser Investments; Dresser Inventments NV
Priority date: 1977-06-01
Filing date: 1978-05-30
Publication date: 1981-08-26
Also published as: JPS541728A; IT7849641A0; DE2821716A1; IT1105414B; FR2393236A1; CA1091522A; FR2393236B1

Description

(54) FUEL METERING AND DISTRIBUTION (71) We, DRESSER INVESTMENTS N.V., a corporation organized and existing under the laws of the Netherlands Antilles, of Pietermaai 6, Willemstad, Curacao, Netherlands Antilles, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to fuel metering and distribution, and more particularly to apparatus for introducing and distributing liquid fuel into an air stream in the formation of a combustible air-liquid fuel mixture.

U.S. Patent 3,778,038 explains a method and apparatus for producing a uniform combustible mixture of air and minute liquid fuel droplets for delivery to the intake manifold of an engine. The apparatus includes an intake air zone connected to a variable area throat zone for constricting the flow of air to increase its velocity to sonic. Liquid fuel is introduced into the air stream at or upstream of the throat zone to minutely divide and uniformly entrain fuel as droplets in the air flowing through the throat zone. Walls downstream of the throat zone are arranged to provide a gradually increasing cross-sectional area for efficiently converting a substantial portion of the kinetic energy of the high velocity air and fuel to static pressure.

Such conversion enables the maintenance of sonic velocity air through the throat zone over substantially the entire operating range of the engine to which the air-liquid fuel mixture is supplied.

It is important to meter the proper quantity of fuel into the high velocity air stream in order to obtain a combustible mixture having a substantially constant air-to-fuel ratio. It is equally important that the fuel so introduced be properly distributed since the uniform distribution plays a major role in consistently obtaining a substantially constant air-to-fuel ratio. Air and fuel introduction rates often vary by a factor of 40 when comparing idling conditions with those encountered during rapid acceleration.

Such conditions demand fuel metering and distribution apparatus having special characteristics such as the avoidance of excessive quantities of liquid fuel at the point where the fuel enters the air stream or at other locations.

According to the present invention there is provided apparatus for introducing and distributing liquid fuel into a moving air stream, comprising: a fuel discharge structure including a fuel opening arranged transverse to the path of air flow; a rod slidably received within the flow opening transversely extending across the path of air flow; and at least one pair of spaced apart tapered slots in the rod for varying the cross-sectional area of fuel flow through the opening as the rod is moved relative thereto, each tapered slot of the pair having a decreasing cross-sectional area in a direction outwardly away from the opening and each slot extending along the length of the rod for distributing fuel along the rod where it is stripped away by the moving air stream, and each of the slots being located in the upstream half of the rod.

In a preferred embodiment the width of each tapered slot may be approximately 0.030 inches. Preferably, the rod has a substantially circular cross-section and the diameter thereof is within the range of one-eighth to three-eighths inches. The rod slides relative to the fuel opening between an idling position and a wide open throttle position. The depth of each slot at the fuel opening preferably ranges from 0.001 to 0.010 inches at the idling position to about 0.090 to 0.100 inches at the wide open throttle position. The fuel bar may include a second pair of spaced apart tapered slots in the rod located in ,the upstream half thereof. Moreover, additional slots may be provided in the downstream half of the rod.

The invention will be better understood from the following description of preferred embodiments thereof, given by way of example only, reference being had to the accompanying drawings, wherein: Figure 1 is a top plan view of a fluid flow device having an embodiment of fuel metering and distribution apparatus, according to the present invention; Figure 2 is a sectional view taken along line 2-2 of Figure 1; Figure 3 is a sectional view taken along line 3-3 of Figure 1 Figure 4 is a side elevational view of the fuel metering and distribution rod shown in Figures 1-3; Figure 5 is a top plan view of the rod shown in Figure 4; Figure 6 is an end elevational view of the rod shown in Figures 4 and 5; Figure 7 is a sectional view taken along line 7-7 of Figure 6;; Figure 8 is a top plan view of another embodiment of fuel metering and distribution rod, according to the present invention; and Figure 9 is an end elevational view of the rod shown in Figure 8.

Referirng in more particularity to the drawings, Figures 1-3 illustrate a fluid flow device 10 for mixing liquid fuel and air in the production of a combustible air-liquid fuel mixture having a substantially constant air-to-fuel ratio. Generally, the device 10 comprises an elongate housing with a central flow passageway therein. The passageway is defined by a pair of opposite stationary large jaws 12, 14 and a pair of opposite small members in the form of slabs 16, 18. As explained more fully below, slab 18 moves toward and away from stationary slab 16 to vary the mass flow of air passing through the passageway.

Specifically, the passageway includes a gradually converging air entrance zone 20, a variable area throat zone 22, and a gradually diverging downstream zone 24.

The stationary jaws 12, 14 together with slab 16 and housing end wall 26 are secured to a rectangular base plate 28 having openings 30 therein for securing the device 10 to the intake manifold (not shown) of an internal combustion engine.

The inside walls of the opposite stationary large jaws are shaped to define a venturi cross section with the small slabs 16, 18 and this venturi cross section includes the air entrance zone 20, the throat zone 22, and the gradually diverging downstream zone 24. Atmospheric air enters the device 10 at the air entrance zone 20, and the air is accelerated to sonic velocity at the throat zone 22. Liquid fuel is introduced into the high velocity air stream at a fuel opening 34 upstream from the throat 22. The fuel opening 34 is located in the stationary slab 16, and a fuel source (not shown) is connected to the opening. A fuel metering and distribution rod 36 mounted for movement with the movable slab 18 is received within the fuel opening 34 to vary the rate of fuel delivered into the high velocity air stream.

The rod has a pair of spaced apart tapered slots 38, 40 for varying the cross-sectional area of fuel flow through the opening 34 as the rod is moved relative thereto, as explained more fully below.

The sonic velocity air-liquid fuel mixture passes from the throat zone 22 into the gradually diverging downstream zone 24 where the kinetic energy of the high velocity air and fuel is efficiently converted static pressure. Such conversion enables the maintenance of sonic velocity air and fuel flow through the throat zone 22 over substantially the entire operating range of the engine. Thus, sonic velocity is achieved at the throat zone even at very low manifold vacuum levels.

The mass flow of air passing through the device 10 is primarily governed by the position of the movable slab 18 relative to the stationary slab 16. Movement of the slab 18 varies the cross-sectional area of the throat zone, and under sonic conditions such variation is accompanied by an equal variation in the mass flow of air. However, such equal mass flow of air is only achieved when the atmospheric conditions remain constant, as explained more fully below.

A bar 41 extending through an opening in the end plate 26 is secured to the outside surface of the movable slab 18. This bar is under the control of a throttle linkage (not shown), and the cross-sectional area of the throat zone is varied by moving the slab 18 in direct response to operating demands imposed upon the engine to which the device 10 is attached. Such demands are imposed upon the throttle linkage which in turn causes the bar 41 to move slab 18 to vary the throat zone area. Since the fuel metering and distribution rod 36 is connected for movement with the slab 18 it is also under the direct control of the throttle linkage. The relationship between the metering rod 36 and the fuel opening 34 is such that incremental changes of the throat area are accompanied by proportional changes in the free cross-sectional area between the slotted rod and the fuel opening.

Hence, under sonic air flow and constant atmospheric conditions, when the area of the throat zone is varied such variation is accompanied by a directly proportional variation in the fuel delivered into the high velocity air stream. The air-to-fuel ratio of the mixture produced remains constant even though the demands of the engine change.

It is significant that the inside walls of the slabs 16, 18 are parallel to one another at least from the throat zone 22 to somewhat above the elevation of the fuel opening 34. By providing such a relationship, the ratio of the cross-sectional area at the fuel opening 34 relative to the area of the throat zone 22 remains constant. Changes in the area of the throat zone are accompanied by linearly related changes in the area of the air entrance zone 20 at the fuel opening 34. With such a constant area ratio, the pressure at the point of introduction of fuel into the air entrance zone 20 bears a predictable relationship to the pressure at the throat. As explained above, under sonic conditions, the pressure at the throat 22 is always approximately 53% of atmospheric pressure.Since the ratio of the area at the point of fuel introduction relative to the area at the throat zone 22 remains constant, the pressure at the fuel introduction point 34 in the air entrance zone 20 is always the same percentage of atmospheric pressure. Thus, changes in atmospheric pressure are automatically reflected in the pressure at the fuel introduction location 34.

It is desirable to produce a vacuum signal at the fuel introduction point of about 1 inch Hg., and the point of fuel introduction is therefore located away from the throat at a position in the air entrance zone where about 1 inch Hg. vacuum exists during sonic flow at the throat. Without a constant area ratio between the throat and the fuel introduction point, the vacuum signal at the fuel point would not vary directly with the throat opening and the only location of unvarying vacuum would be at the throat. Difficulty in precise location of the throat could result in a varying signal at this location.

The fuel metering and distribution rod 36 functions to introduce and distribute predetermined amounts of liquid fuel into the rapidly moving air stream passing through the fluid flow device 10. As noted above, the rod is slidably received within the fuel opening 34 and it transversely extends across the path of air flow. The pair of spaced apart tapered slots 38, 40 provide channels along which the liquid fuel flows when such fuel is introduced into the air stream. Preferably the tapered slots 38, 40 are spaced apart approximately 1200, as shown best in Figure 6. However, spacing ranging from 90" to 1200 may also be utilised. The width of each slot is approximately 0.030 inches, and the taper of each slot is such that proper amounts of liquid fuel are introduced into the air stream as the mass thereof varies.In this regard the rod slides relative to the fuel opening between an idling position and a wide open throttle position. The depth of each slot at the fuel opening ranges from 0.001 to 0.010 inches at the idling position to about 0.090 to 0.100 inches at the wide open throttle position. Finally, the rod has a substantially circular cross section, the diameter of which is in the range of one-eighth to threeeighths of an inch, preferably a quarter of an inch.

The tapered slots 38, 40 are located in the upstream half of the rod 36 and serve to distribute the fuel along the rod where it is striped away by the rapidly moving stream.

Additional tapered slots 42, 44 may be provided in the downstream half of the rod 36, as shown best in Figure 4. The slots 42, 44 are tapered in the same directions as the slots 38, 40 but extend only about half way along the rod. The slots 42, 44 enable adidtional liquid fuel to be introduced into the air stream at the wide open throttle position of the rod and those throttle positions which are close to wide open. Such additional fuel introduction provides an airfuel mixture for increased power purposes.

Figures 8 and 9 illustrate another fuel metering and distribution rod 46 that functions to introduce and distribute predetermined amounts of liquid fuel into a rapidly moving air stream. The rod 46 has four spaced apart tapered slots 48 in the upstream half thereof and each slot is separated from an adjacent one by appfoxi- mately 40", as shown best in Figure 9. The width of the slots 48 of rod 46 are somewhat smaller than the width of the slots on the rod 36. Also, the taper may be more gradual in the case of the slots 48.

Otherwise, the fuel metering and distribute tion rod 46 functions in the same manner as the fuel rod 36. Moreover, additional slots may be provided in the downstream half of rod 46, if desired.

In operation, the pressure of the high velocity air stream flowing through the passageway of the device 10 is sensed at the fuel opening 34 where it bears a predictable relationship to atmospheric pressure. The rate of fuel delivered into the air stream is adjusted in response to changes in the air pressure sensed so that the air-to-fuel ratio of the air-liquid fuel mixture is maintained substantially constant.

Adjustment of the rate of fuel delivered into the air stream is accomplished by the change in pressure differential across the valve that comprises the metering and distribution rod 36 and the fuel opening 34. For reasons noted above, the pressure of the air stream at the fuel opening 34 changes in proportion to atmospheric pressure variations, and the pressure change at the fuel opening results in a change in the pressure differential across the valve. The rate of fuel delivered into the air stream is thereby adjusted in direct response to changes in atmospheric pressure.

During the relatively brief subsonic mode of operation when the manifold vacuum levels are quite low, the fluid flow device functions as a metering venturi to introduce varying quantities of liquid fuel into the varying velocity air stream. Due to the efficient conversion of the energy of the high velocity air and fuel to static pressure in the diffuser, sonic air flow at the throat zone 22 is maintained over just about the entire operating range of the engine. However, at very low manifold vacuum levels of below 5 inches Hg. vacuum, for example, the air flow at the throat zone 22 may drop below sonic and the reduced velocity operates to such less fuel into the passageway. During the subsonic mode the vacuum signal at the fuel opening 34 varies as the air velocity squared.

WHAT WE CLAIM IS:- 1. Apparatus for introducing and distributing liquid fuel into a moving air stream, comprising: a fuel discharge structure including a fuel opening arranged transverse to the path of air flow; a rod slidably received within the fuel opening transversely extending across the path of air flow; and at least one pair of spaced apart tapered slots in the rod for varying the cross-sectional area of fuel flow through the opening as the rod is moved relative thereto, each tapered slot of the pair having a decreasing cross-sectional area in a direction outwardly away from the opening and each slot extending along the length of the rod for distributing fuel along the rod where it is stripped away by the moving air stream, and each of the slots being located in the upstream half of the rod.

2. Apparatus according to claim 1 wherein the width of each tapered slot is substantially 0.030 inches.

3. Apparatus according to claim 1 or claim 2 wherein the rod has a substantially circular cross-section, and the diameter of the rod is within the range of one-eighth to three-eighths of an inch.

4. Apparatus according to claim 3 wherein the diameter of the rod is a quarter of an inch.

5. Apparatus according to any preceding claim wherein the rod slides relative to the fuel opening between an idling position and a wide open throttle position, the depth of each slot at the fuel opening ranging from 0.001 to 0.010 inches at the idling position to about 0.090 to 0.100 inches at the wide open throttle position.

6. Apparatus according to any preceding claim including a second pair of spaced apart tapered slots in the rod located in the upstream half thereof.

7. Apparatus according to any preceding claim including a pair of spaced apart tapered slots in the rod located in the downstream half thereof.

8. Apparatus for introducing and distributing liquid fuel into a moving air stream, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

Reference has been directed in pursuance of section 9, subsection (1) of the Patents Act 1949, to patent No. 1 517002.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. functions as a metering venturi to introduce varying quantities of liquid fuel into the varying velocity air stream. Due to the efficient conversion of the energy of the high velocity air and fuel to static pressure in the diffuser, sonic air flow at the throat zone 22 is maintained over just about the entire operating range of the engine. However, at very low manifold vacuum levels of below 5 inches Hg. vacuum, for example, the air flow at the throat zone 22 may drop below sonic and the reduced velocity operates to such less fuel into the passageway. During the subsonic mode the vacuum signal at the fuel opening 34 varies as the air velocity squared. WHAT WE CLAIM IS:-

1. Apparatus for introducing and distributing liquid fuel into a moving air stream, comprising: a fuel discharge structure including a fuel opening arranged transverse to the path of air flow; a rod slidably received within the fuel opening transversely extending across the path of air flow; and at least one pair of spaced apart tapered slots in the rod for varying the cross-sectional area of fuel flow through the opening as the rod is moved relative thereto, each tapered slot of the pair having a decreasing cross-sectional area in a direction outwardly away from the opening and each slot extending along the length of the rod for distributing fuel along the rod where it is stripped away by the moving air stream, and each of the slots being located in the upstream half of the rod.