Fuel system components

July 23, 1968

3,393,984

F. O. WISMAN

FUEL SYSTEM COMPONENTS

Filed Feb. 14, 1967

<img file="US3393984A_D0001.tif" />

INVENTOR

United States Patent Office „ ₄³-^{393 984}

Patented July 23, 1968

3,393,984 FUEL SYSTEM COMPONENTS Franklin O. Wisman, Richmond, Ya., (Rte. 8, Box 431, Chambersburg, Pa. 17201) Filed Feb. 14, 1967, Ser. No. 616,082 2 Claims. (Cl. 48—180)

ABSTRACT OF THE DISCLOSURE

A new concept for accelerating the vaporation of fuel in air for combustion. Action derives from application of non-wettable materials to surfaces contacted by entrained liquid fuel particles whereby the particles are caused to fragment into smaller globules possessing aggregate surface area greater than the original particles. A preferred embodiment includes a mixer device for homogenizing the discharge mixture. The teaching is particularly applicable to the carburetion and induction systems of automobiles for the purpose of reducing unburned hydrocarbon exhaust emission and for improving performance and economy.

The present invention relates to improvements in apparatus for preparing a liquid fuel for combustion, as exemplified by the carburetor and induction manifold of a gasoline automobile engine.

The proliferation of gasoline powered automobiles has produced an air pollution emergency and made necessary legislation directed to its abatement. Product Engineering, vol. 37, No. 27, pp. 32-41 Dec. 19, 1966, published an excellent exposition of the problem and the existing state of the art relating to remedies.

The emission of unburned hydrocarbons, particularly carbon monoxide, is largely a reflection of deficient carburetor and induction manifold performance. This has long been recognized in regulations banning indoor operation of gasoline powered materials handling trucks while generally permitting the same engines after conversion to liquefied petroleum gas fuels. The significant difference 40 lies in the means for rendering the fuel gaseous rather than in the chemistry of the fuel itself.

Perhaps the most important pertinent fact is that fuels in liquid form will not burn but must first be vaporized. Moreover, after vaporization gasoline is combustible only over a rather narrow range of air mixtures from about 9:1 ⁴⁵to 17:1 by weight. The stoichiometric ratio affording sufficient oxygen to completely burn the gasoline is 14.7:1.

It is important to recognize that atomization and vaporization are two separate and distinct phenomena. Atomization of a liquid into a finely divided spray or fog does not in itself constitute a transition to the gaseous phase capable of molecular admixture with oxygen which is the necessary prerequisite for combustion. The discrete fog particles remain liquid albeit finely divided but of aggregate volume identical to the original pre-automization liquid. When vaporization occurs the liquid absorbs heat from its surroundings, expands to a volume much greater than the liquid and assumes the elastic qualities of a gas. Since the absorption of heat represents a flow of energy across the liquid surface and nature does not ⁶⁰admit of infinite rates of energy flow or power, it follows that the rate at which vaporization will occur is proportional to the exposed liquid surface area. Consider now a sphere of liquid 1 inch in diameter. It has a volume of .533 cubic inch and a surface area of 3.14 square inches ⁶⁵or a specific area of 6 square inches per cubic inch. If this same .533 cubic inch of liquid is atomized into spheres of .001 inch diameter they will be 1 billion in number, each with a surface area of 3.14/1,000,000 and specific area has become 6000 square inches per cubic ⁷⁰an aggregate surface area of 3140 square inches. The inch with the exposed area and rate at which vaporization can occur increased 1000 fold. Hence atomization, while insufficient in itself, is to be valued as a prelude to rapid vaporization. If instead of being atomized this same .533 cubic inch of liquid were spread in a film .003 inch thick (the thickness of ordinary newsprint) it would cover only 177 square inches or about 5% of the area presented when atomized. The trend toward compactly built engines with manifold passages in some instances as short as about 6 inches accentuates the desirability of attaining the fastest vaporization rates. Manifold velocities commonly reach 200 feet per second, resulting in an available vaporization time of the order of only %₀₀second.

Present carburetor designs have enjoyed nearly a century of evolutionary improvement and while the needs have long been recognized, adequate remedies have been lacking for the problems of wet wall flow and unequal mixture distribution to the several cylinders. That portion of the fuel which is swept along the manifold and combustion chamber surfaces as a wet film is condemned to flow out the exhaust unburned. The same destiny awaits the residual core of any air entrained liquid particle too large to be evaporated during the brief transit time through the engine. Inequality of mixture distribution results in carburetion being adjusted to cater to the firing requirements of the leanest cylinder with the result that others are receiving an over-rich mixture which cannot be fully burned. The practical consequence is that carburetors must almost invariably be calibrated richer than stoichiometric, in some cases as rich as 11:1. An engine so equipped cannot fail to discharge about 25% of its fuel unburned and paradoxically may show rather low carbon monoxide emission if the fuel is passing through inertly in liquid form. Leaner calibration of the carburetor in such a case will usually result in mis-firing and ’oss of power.

It is a particular object of this invention to importantly diminish the emission of unburned hydrocarbons in the exhaust gases of automobile engines. Further objects are to render the operation of such engines smoother and more responsive and to reduce their fuel consumption. It is a further special object to accomplish the foregoing in apparatus adaptable to simple and economical retrofit application to the millions of automotive vehicles now in operation.

I have discovered a simple and practical means for applying a familiar but previously unexploited scientific principle to the instant problems. Any student who has spilled a drop of mercury onto a surface it does not wet remembers vividly how it fragmented into a multitude of smaller droplets. The same phenomenon can be demonstrated with water against a non-wettable waxed surface. It was explained above that the aggregate liquid surface area exposed for evaporation increases as the liquid is broken into smaller particles. The manner in which my invention applies these two scientific principles to the instant problems will be set forth in the following descriptive specification and accompanying drawings.

FIGURE 1 is a sectional elevation view through a carburetor and induction manifold of an engine illustrating the manner of praticing my invention. Some conventional details not needed to describe or understand the present invention have been omitted. FIGURE 2 is a detail plan view of an improved embodiment for practicing my invention. FIGURE 3 is a detail plan view of a preferred embodiment. FIGURES 2 and 3 which look upwardly along line 2,3-2,3 show the relation of certain features of the invention to the carburetor throttle.

The numeral 10 generally indicates a carburetor associated with an engine intake manifold 20 for delivering mixture to the cylinder or cylinders. The carburetor il3,393,984 lustrated is of the conventional type wherein air is drawn through a venturi tube 14 to produce a pressure depression for drawing fuel from the discharge nozzle 16. A throttle valve 18 controls the admission of mixture to the manifold 20 which is shown with branches 22 and 5 24 nourishing various of the engine cylinders. The carburetor 10 and manifold 20 are joined by means of a bolted flange joint at 30 with sealing gaskets 31 and 33. Homogenizer plate 40 represents a preferred method of practicing my invention. At idle and low speed conditions θ fuel is discharged by the idle port 12 as will be understood by those skilled in the art.

To better explain the operation of the invention, the conditions prevailing in its absence and with the homogenizer plate 40 removed will first be described. At idle and low speeds fuel issues from idle port 12 and is partly mixed with air flowing past the throttle at 19 but is mostly swept as a spreading streak of wet film down the throttle body wall 46 and into manifold at 47. Because an equal quantity of air is being admitted at 17 totally without ₂q fuel it is obvious that branch 22 will receive a decidedly richer mixture than branch 24. A similar condition prevails with respect to the fuel sprayed through discharge nozzle 16 which usually incorporates provisions for aerating and finely dividing the fuel. The throttle plate is il- 05 lustrated in the attitude typically occupied under steady conditions at moderate speeds of 30-50 m.p.h. The entrained liquid particles almost immediately impact the inclined throttle plate and because the ordinary materials of construction are wetted by gasoline, the spray is con- 30 solidated into a film and the nozzle atomization is frustrated. This liquid is swept to the lower edge, partly transferred to the wall at 44 and unvaporized residual portions swept into branch 24 at 49. Again the consequence is unequal distribution which may under some conditions 35 reach the absurdity of one cylinder not firing because it is starved while another is flooded with a mixture rich beyond the limit of combustibility.

An important principle of my invention consists in making those surfaces which will be contacted or struck by 40 liquid fuel particles of a material which will not be wetted by the fuel. The formation of films, offering low specific area, is prevented and instead an impacting particle is fragmented into smaller globules just as was the spilled drop of mercury. The physical properties which govern the 45 phenomenon of non-wetting are that the liquid surface tension acting to pull the liquid into a spherical shape must exceed the surface free energy striving to spread it as a film along the solid surface. Gasoline has a relatively low surface tension of only about 20 dyne-cm. and the choice of 50 materials with lower surface free energies is limited. The material which I prefer to use is polytetrafluoroethylene. It is readily applied as a coating over any of the common structural materials and is self cleaning, obviating the need for any maintenance. There are other materials and 55 surface film treatments which may also be employed to practice my invention. It is expected that future progress in the chemical arts will yield practical materials with lower surface free energies and otherwise preferable qualities. 60

The simplest practice of my discovery then is to make the surfaces of throttle 18 and/or bore surfaces 44, 46, 47, 49 of the non-wettable material or film treatment. When this is practiced, the wet film streaks within the bores tend to be abolished and replaced with spheroids 65 offering greater area for vaporization and more readily detached from the surface for entrainment in the flowing air stream. The nozzle spray impacting the throttle 18 is fragmented and bounced off in the direction of wall 44 where the process may be repeated with vaporization en- 70 hanced. However in this embodiment the bulk of the fuel will still flow through opening 17 while opening 19 is starved and the mixture reaching the various manifold branches may be less than desirably homogeneous.

The preferred practice of my invention is to insert the 75 homogenizer plate 40 with non-wettable surfaces into the joint between carburetor and manifold. The concept of a mixer is old and was the subject of numerous patents issued early in this century. Examples are 1,186,386 to Egan et al., 1,199,243 to Bushey and 1,231,939 to Reynolds. Others are 1,424,349 to Fryett and 1,885,559 to Smith. These prior art devices were applied grossly to creating admixture of all portions of the flowing charge by means of elements randomly located without regard to the carburetor design. Some may have actually hindered vaporization by precipitating surface films out of atomized streams or by centrifuging liquid to the walls with similar consequences. The novelty of the present homogenizer plate resides importantly in use of non-wetting materials to compel atomization rather than film formation and in designing the location of the homogenizer blades to cooperate with the sources of the non-homogeneous flow. Referring now to the figures, the homogenizer plate carries dependent fingers or blades 41 and 48 inclined downward in the direction of flow. These are positioned to align and register with the location of the proximate source of the non-homogeneity, namely the two disparately laden air streams issuing through the crescent shaped throttle opening apertures at 17 and 19. The roots of the blades 41 and 48 are positioned to intercept a major fraction of those flows at 42 and 43 and deflect the two streams inwardly for admixture in the central region 45. At the same time wet wall films have been intercepted and any flowing liquid fuel particles have been fragmented and splashed off the non-wettable surfaces of blades 41 and 48 into the central region 45 where admixture of the two deflected air streams is occurring. FIGURES 2 and 3 illustrate two of the many possible blade designs by which this may be practiced. The FIGURE 3 embodiment is to be preferred as somewhat easier to manufacture and on test it appears to offer some performance superiority.

Yet another mode of practicing my invention is illustrated at 50. It often happens that for various reasons liquid fuel will collect in certain parts of the manifold as films, puddles, or slowly moving streams. I find that this liquid can be broken into small globules and dispersed in the moving air stream by providing an inclined non-wettable ramp at 52. Preferably the entire manifold interior should be coated, with inclined ramps provided in the critical locations.

The preferred embodiment with the homogenizer plate 40 is also most practically and easily applied on a retrofit basis to existing cars with excellent effectiveness as exemplified by data from trial on two different popular cars. One was a 1966 model Chevrolet station wagon with 283 cubic inch V-8 engine. As delivered its fuel economy was 14-15 miles per gallon at 60-65 m.p.h. highway cruising and there was a definite tendency to lean-out and misfire in normal city cornering at light throttle openings. This last was evidence that the mixture was a bit too lean, on the basis of vaporized combustible fuel. Installation of the homogenizer plate embodiment remedied the mis-firing, rendered the engine palpably more responsive and improved fuel economy to 19 m.p.g. Further experiment showed that the main calibrating jets could be reduced in area by 26% and 21.7 m.p.g. economy realized before too-lean engine hesitation or lumpiness could be detected. The jet size for peak engine performance represents an area reduction of 17% from original and produces fuel economy of 20-21 m.p.g. In another experiment a 1965 model Ford with 289 cubic inch V-8 engine having no initial misbehavior and fuel economy of 15-16 m.p.g. was tested. Economy improved to 20.3 m.p.g. on installation of the plate alone. Subsequent reduction of the jet area by 16% maintained 20-21 m.p.g. economy with superior performance. For retrofit application the prepared homogenizer plate could be sold as part of the perishable parts kit common in the trade for carburetor overhaul. The replacement jets normally included in such kits would be appropriately recalibrated.

3,393,984

It will be understood that the several embodiments described may be practiced either separately or in combination. The compound action results in reducing the need for choking when cold and improves a particularly troublesome aspect of the exhaust emission problem. A con- 5 ventional fuel induction system tends to become wetted under open throttle operation and then on subsequent closed throttle deceleration this accumulated wet fuel is evaporated in the presence of insufficient air for combustion. The earlier the fuel flow can be vaporized and the drier the manifold can be kept, the lesser the magnitude of this effect.

The foregoing is considered as illustrative only of the pinciples of the invention. Further since numerous modifications will readily occur to those skilled in the art, it 15 is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to falling within the scope of the following claims.