US 3747581 A
A portion of the contaminants in ICE exhausts has its origin in intake of fuel in droplet rather than vapor form. This invention provides two cooperating means of assuring evaporation of the fuel before intake. A venturi throat is provided in a passage after mixing of fuel with intake air in a conventional carburetor having a venturi throat. This second venturi throat provides a pressure reduction in the intake mixture following carburation which causes much of the fuel still in droplet form to evaporate. A low resistance catching filter or screen is placed in the path of the intake mixture after the second venturi throat such as to collect droplets there existing such as those which were too large to be evaporated by the pressure reduction at the pressure reduction throat. These droplets are collected and evaporated in a region of elevated temperature in close proximity to the cylinders while being reduced in volume to be evaporated by the second venturi evaporator.
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Description (OCR text may contain errors)
United States Patent [1 1 Kolb 1111 3,747,581 [4 1 July 24, 1973  lnventor: Richard G. Kolb,5510 Harvest Scene Lane, Columbia, Md. 21044 221 Filed: Feb. 17, 1971 211 Appl.No.:ll6,131
 US. Cl. 123/141, 48/180 M, 48/180 R  Int. Cl. F02m 29/00  Field of Search 123/141; 48/180 R, 48/180 M  References Cited UNITED STATES PATENTS 3,414,242 12/1968 Bouteleux 261/41 D 1,315,758 9/1919 Brown 48/180 R 1,462,750 7/1923 Hart 48/180 R 1,515,280 11/1924 Saunders et a1 48/180 R 1,282,654 10/1918 Thurston 48/180 R 1,007,010 10/1911 Schlayer 123/141 1,260,609 3/1918 Warren 123/141 1,394,820 10/1921 Fritz 123/141 1,530,157 3/1925 Edwards 123 141 3,393,984 7/1968 Wisman 123/141 X 1,311,071 7/1919 Hunter 123/141 FOREIGN PATENTS OR APPLICATIONS 755,753 5/1953 Germany 48/180 R 741,462 12/1932 France 123/141 969,851 5/1950 France 123/141 550,807 11/1956 Italy 123/141 583,186 1011958 Italy 123/141 Primary Examiner-Wendell E. Burns Attorney-Beveridge & De Grandi 57 ABSTRACT A portion of the contaminants in ICE exhausts has its origin in intake of fuel in droplet rather than vapor form. This invention provides two cooperating means of assuring evaporation of the fuel before intake. A venturi throat is provided in a passage after mixing of fuel with intake air in a conventional carburetor having a venturi throat. This second venturi throat provides a pressure reduction in the intake mixture following carburation which causes much of the fuel still in droplet form to evaporate. A low resistance catching filter or screen is placed in the path of the intake mixture after the second venturi throat such as to collect droplets there existing such as those which were too large to be evaporated by the pressure reduction at the pressure reduction throat. These droplets are collected and evaporated in a region of elevated temperature in close proximity to the cylinders while being reduced in volume to be evaporated by the second venturi evaporator.
Patented July 24, 1973 INVENTOR RICHARD G. KOLB BY Wa 4 3 a QM ATTORNEYS buretor mixing of fuel and air, or that such enhanced evaporation reduces the volume of liquid at time of collecting fuel droplets for evaporation, or that such reduced droplet quantities at the filter resulting from the considerable reduction in volume of liquid fuel by the venturi evaporator avoids overloading of the filter evaporator to prevent collected droplets from being sluffed off by the filter or collecting screen.
It is accordingly an object of this invention to provide a second fuel evaporating venturi throat for reduction of the quantity of liquid fuel combined with a liquid fuel catching filter to provide at minimum cost a wholly vaporized fuel for ingestion into the cylinders of an ICE engine.
Another object of the invention is to provide an economical venturi throat for causing a pressure reduction in the intake air/fuel mixture after carburetion to effect 7 evaporation of at least a substantial portion of the fine droplets emerging from the fuel aspiration throat in the carburetor.
A still further object of the invention is to provide a droplet catching fuel filter exhibiting very small dynamic flow resistance in an air/fuel passage between a second venturi throat and the cylinders of an engine.
Other objects and advantages of the engine will be perceived in connection with the following description of the invention taken in connection with the drawings of which:
FIG. 1 is a diagram of the general arrangement according to this invention for combining two aspects of improved fuel vaporization after carburization;
. FIG. 2 shows an evaporator arrangement alternative to that of FIG. 1;
FIG. 3 illustrates a Bernouilli throat and filter in a manifold at the input to a cylinder;
FIG. 4 illustrates a venturi throat after the carburetor to which a filter is attached;
FIG. 5 illustrates a Bernouilli constriction alternative to that of FIG. 4;
FIG. 6 illustrates a further form of Bernouilli constriction; and
FIG. 7 illustrates a form of filter alternative to that of FIG. 4.
The purpose and effect of this invention may be summarized in stating that tests made by independent testin g laboratories have shown that a construction according to this invention is effective both to substantially increase the gas mileage and to decrease the recognized pollutants, normally inherent in operation of an ICE plant. An SAE Paper 710069 entitled Exhaust Emission Control for Used Cars published January, 1971 states that averaged pre 1968 cars equipped with the best antipollution devices then known had the following contaminants: HC 283ppm; NOx 693ppm; CO 1.13 percent. Tests of the present device show reduced contaminants of: HC l95ppm; NOx 564ppm; CO 0.91%, which approximate the U.S. Government standards applicable to 1970 cars, even when applied to cars of pre-1968 manufacture, prior to the establishment of emission standards. The invention is applicable to later cars wherein emissions have already been reduced to current standards.
While it has been generally recognized that complete vaporization of fuel is of some benefit in promoting clean burning, it has not heretofore been recognized that pollutants can be reduced to the extent currently found on test of apparatus according to this invention. Also it has not been understood that modern practice ingests considerable quantities of liquid fuel in automotive engines or that engine efficiency could be greatly improved by effecit'vely complete fuel evaporation, as has been demonstrated in test of this invention. Other tests show that various method and means for effecting fuel vaporization before entry into the cylinders have not been adequate to avoid ingesting liquid droplets. This invention provides in very simple constructions, two effects which are cumulative and mutually supporting for enhancing evaporation with a result appearing to exceed that known in prior practice.
Referring first to the second effect above-noted, one basic feature of the present invention is the provision of a screen or filter for catching droplets emitted from the carburetor as a cloud or mist following aspiration in the carburetor venturi, and holding these droplets as liquid adhereing to the fibers or strands of the screen or filter until they have evaporated due to passage of further intake air. It is recognized that many filter devices have heretofore been employed, some of which are intended to catch liquid fuel and retain the same in position until specially introduced currents of air are impinged thereon for evaporating that fuel. One reason that these havenot been effective is that too much fuel is collected on the screen for evaporation without some of that fuel sluffing off as droplets which may often be larger in size than the droplets emerging from the carburetor, and therefore a greater contributor to pollution. This invention employs a venturi pressure reduction after air/fuel mixing and before the filter as a means of partial fuel evaporation which greatly reduces the volume of liquid droplets in the mist as it strikes the screen, and therefore presents on the screen a much smaller quantity of liquid fuel to be evaporated by air passing the filter.
According to this prelimiinary evaporation feature of the invention, a venturi throat is in the intake line after carburetion, preferably somewhere between the carburetor and the intake manifold effective to reduce the cross sectional area of the intake passage, for example 10 to 30 percent, whereby the air fuel mixutre is increased in velocity within a smooth wall venturi throat structure, thus to reduce the ambient pressure about the fuel droplets. Since fine liquid droplets have high surface tension relative to volume and tend to evaporate rapidly in a carrying gas in which the existing vapor pressure of the liquid is below saturation for the existing temperature, many of the finer droplets evaporate in a normally operating intake manifold. They do not all evaporate in the conventional manifold. By using a venturi-caused pressure reduction after carburetion provides an increased tendency of those droplets to be evaporated according to well known gas theory. It is well known that a liquid evaporates more rapidly into a vacuum or a reduced partial pressure than into the substantially full atmospheric pressure normally experienced. It is also well known that droplets evaporate much more rapidly when in fine mist form, according to an exponential relationship between evaporating rate and the diameter of the droplets. Since some of the droplets in the mixture may be too large to be evaporated by this means (as demonstrated by testing) a percentage of the droplets in the mixture may still be present following the second venturi under some circumstances, e.g. acceleration and enter the engine in droplet form. Those droplets, while reduced in number and volume, are nevertheless to be avoided to achieve a clean burning in ICE practice and an enhancement of the operating efficiency. The screen or filter catches these droplets, when present, but now in reduced quantity so that they evaporate from the filter without sluffing off.
According to this invention, these two effects combine to achieve a result which is not obtainable by either a second venturi throat, following the carburetor, or by a filter alone between the carburetor and the engine intake, which overloads in the absence of the venturi preevaporator.
It will be appreciated that a structure as generally described is suitable for use in the input passage of an intake manifold after the carburetor and before dividing for the individual cylinders of an engine. Alternatively, such a filter or constriction and filter may be in the individual intake passage to each of the cylinders, or to a group of cylinders, in lieu of the single intake manifold installation described. A constriction throat of various design is used as a preliminary evaporator forward of the droplet-catching filter, which may be'a single throat, or separated throats, according to the location of the filters in the intake passages. The constrictions may be smoothly curved, conical or stepped.
It will be appreciated that the filter need not follow immediately after the carburetor or the constriction but may be located at the junction between the manifold and the block of the engine in such a manner as to be held in place along with a sealing gasket. Such a filter extends across a single intake passage unit following a second venturi as in FIG. 1, or across each intake passage in an installation as illustrated in FIG. 3. By placing the evaporator screen close to the entrance to the cylinder, a higher temperature is present when the engine has come up to operating temperature, and this is effective for evaporating a larger quantity of fuel during those intervals of extraordinary power requirement as when the engine is loaded or rapidly accelerated. In such intervals larger quantities of liquid fuel must be evaporated from the filter.
Regardless of the location of the number of filter units for catching and evaporating droplets, it may be seen that Bernouilli constriction-caused evaporation of some 50 percent of the fuel present in droplet form as it leaves the carburetor venturi permits the dropletcatching filter to more effectively remove the remaining liquid fuel without an appreciable accumulation on the filter itself thus to substantially avoid both the unequal fuel concentrations in the cylinders and the ingestion of droplets. Essentially all fuel otherwise in droplet form appears to be evaporated as it enters the cylinders. Once evaporated the fuel is then a gas which remains a gas in intimate and complete mixture with the air. The effects of the constriction and the filter are cumulative and more than either effect alone, and than the two elements when used together but in the opposite order such that the constriction follows the dropletcatching filter.
It will be seen that this constriction requires no changes in manifold or carburetor, but permits placing the evaporator filter close to the heated portions of the engine at which the temperature may be well above the boiling temperature for gasoline. Obviously this could not be done for the carburetor itself, which must never be much heated. A prior art venturi throat forming part of the carburetor, in which the fuel is first aspirated into the intake air, cannot serve both the prior art purpose of aspiration and the later evaporation obtained in this invention by pressure reduction about the droplets to effect a considerable further evaporation of droplets before they reach the filter. Test data indicates that the combined effect is much more than obtained on prior emission control arrangements, at least as to older cars.
Referring now to the drawings illustrating embodiments of the invention, FIG. I shows an internal combustion engine indicated generally at 10 having a carburetor 11 including a first venturi 12, 12' with a primary fuel controlled orifice 13 for aspiration of a liquid fuel in a compound venturi throat at 12, 12'. Manifold 14 extends from the carburetor to separate intake ports 15, 15', 15", etc. under control of a throttle butterfly valve 19. At the junction of the carburetor and the manifold 14 there is normally a gasket 16, other gaskets (not shown in FIG. 1) seal the manifold to the engine block around ports 15, 15 while gaskets 17 seal manifold 14 to cylinder head 18 in FIGS. 2 and 3. A filter 20, which may be formed as a multi-layer metal screen of high porosity to avoid resistance to air flow or pressure drop, may be secured by a flange portion 21 at a cutaway portion of gasket 16, 17 etc.
Filter 20 may be formed as a cupped screen illustrated in FIG. 4, 5 or 6 in which the screen has flange 21 and cupped element 22 preferably of fine metallic gauze strands 23 and 24 and extends across the intake passage. It may comprise merely two nesting screen layers 25, 26 or may have a forward screen element 26 separated from outer element 25 for confining a fibrous material 29 thereinbetween as in FIG.7, this fibrous material being steel wool or bronze wool, or the like. The exact form of the filter may be greatly varied but should have a very low resistance to air. passage to maintain unimpaired air flow so as not to alter the fuelair ratio. Sufficient baffling passages, e.g. two or more layers of fine screen or wool, are provided so that droplets cannot pass through without striking at least one filament or fiber of the screen. All liquid droplets which would otherwise pass into the intake ports of the engine are thus retained and evaporated at an elevated temperature.
The second venturi throat or Bernouilli constriction 30, 33 or 35 thus formed between the carburetor and the intake ports for the engine according to this invention has a capability of providing a reduced airpressure in which at least the finest fuel droplets are fully evaporated before reaching the filter. Some 30 percent reduction between manifold sectional area and throat area is found to be a good compromise between need for free air-flow and need for effective evaporation, although greater reductions in area may be used.
In some experiments it has been found desirable to employ smaller fuel jet nozzles when using the constric tion and filter of this invention. One feature of the invention is its ability to more thoroughly mix fuel and air, and with the resulting greater homogeneity and predictability of mix a leaner mix is used, increasing gasoline economy as well as further improving emissions.
A Bernouilli constriction having smooth flow converging and diverging portions, referred to as a venturi, produces less pressure drop in the dubting of which it is a part than other forms of Bernouilli constriction, and is illustrated in FIG. 4. As illustrated in FIG. 5 the Bernouilli constriction is a truncated conical section terminating in a flange 21 at the larger end, to which a filter screen optionally may be attached as at 28. The constriction shown at is thus a converging nozzle only within the ducting. Filter 20 may be separate from cone 30' and may comprise a filter in each of the individual input ports for the cylinders, as in FIG. 2. A suitable Bernouilli constriction may also, be of the form shown at FIG. 6 comprising a cylindrical portion having a flange 21 and having stepped degrees of constriction between the leading end and the exit of the Bernouilli constriction, including shoulders 36, which have the advantage of catching a portion of the liquid droplet fuel present to further assist in its evaporation so that the following screen 20 is less likely to be loaded sufficiently to itself give off droplets.
In view of the foregoing discussion it will be appreciated that matters of economy or auxiliary benefits from shoulders 36 may make preferable a form of Bernouilli restriction other than the venturi throat. It is likewise apparent that screen 20 may be nested within the conical structure 30' or the stepped restriction 35, or. may be exterior thereto, secured underneath flange 21, or may be soldered exterially to the constrictor 35 or 30. Similarly a retaining ring 27 may secure a screen portion of the filter 20 in a groove 34 formed in the exterior of the constrictor as at 33.
In FIG. 1 there is also illustrated a conventional arrangement of an idle jet normally opening into the carburetor passage beyond the throttle valve since this nozzle is desired for bypassing the throttle valve in order to maintain operation of the engine during the time when the throttle valve is in the closed position. Holes through valve 19 normally permit a quantity of combustion air mixed with fuel for the idle condition, but such an arrangement does not produce smooth idling for the reason that cylinders will not receive a uniform mixture or a mixture on which combustion is reliable. Thus it is necessary to supply additional fuel by way ofa jet 40 to enrich the fuel and, air mixture passing into the intake ports of the engine at idling speeds. Jet 40 normally consists of a needle point 41 adjustable within a tapered conical piece by means of an adjusting screw 42 for controlling the rate of supply of liquid fuel beyond the carburetor. It is well known in the automotive engineering art that this requirement of fuel bypassing the carburetor through a jet 40 is one of the causes of undesired emissions from automotive engines, being fuel in droplet form. It has also been recently affirmed that a considerable portion of the emissions occurs during idling of the engine, this idling condition producing a far greater proportion of the various contaminants than occurs in normal operation of the engine except possibly for conditions of engine overload where contamination is alsoincreased.
The present invention supplies a pressure reduction applied to normal mixtures and to idling fuel added thereto as the fuel-air mixutre passes through a Bernouilli constriction by which fuel droplets are evaporated to a much greater extent than without the resulting pressure decrease. Those larger droplets not there evaporated strike screen 20 and adhere to the screen until passing air has evaporated the liquid. Since a much smaller quantity of liquid fuel strikes the screen 20 because of the pressure changes in the Bernouilli constriction following the carburetion, the screen is less loaded. This means of evaporating the droplets during idling conditions has been found effective in cleaning up the exhaust of internal. combustion engines to a remarkable'degree.
It is known in the prior art that a more perfectly mixed and better retained mixture of fuel and air when fuel is in the gaseous state provides a more uniform fuel-air distribution to all cylinders and therefore reduces the octane requirement in the fuel for any ICE. This better distribution is achieved by the second constriction followed by the filter.
What is claimed is:
1. In an internal combustion engine having a carburetor including a fuel aspirating nozzle in a venturi and a throttle valve controlling mixture passage to a manifold connecting the carburetor to an input port of a cylinder, the improvement for evaporating input fuel comprising in combination, means for reducing the pressure after carburation of the air-fuel mixture without further fluid aspiration to enhance the evaporation of aspirated fuel portions in droplet form, including a Bernouilli constriction downstream from the carburetor, said constriction having an opening not substantially smaller than the opening in the carburetor venturi, and a droplet retaining filter device arranged across the manifold downstream from the minimum area of said constriction, said screen comprising a bag-like portion extending through said constriction and downstream therefrom a distance at least equal to the minimum diameter of the restruction and including a mounting flange radially extending from the upstream opening of said bag portion.
2. In an internal combustion engine having a carburetor including a fuel aspirating nozzle in a venturi and a throttle valve controlling mixture passage to a manifold connecting the carburetor to an input port of a cylinder, the improvement for evaporating input fuel comprising in combination, means for reducing the pressure after carburation of the air-fuel mixture without further fluid aspiration to enhance the evaporation of aspirated fuel portions in droplet form, including a Bernouilli constriction downstream from the carburetor, said constriction having an opening not substantially smaller than the opening in the carburetor venturi, said constriction comprising a tubular structure aligned with the fluid flow from the carburetor, said tubular structure having an exterior diameter substantially exceeding its interior diameter, and a droplet retaining filter device exteriorly attached to said tubular structure and extending downstream therefrom a distance at least equal to said interior diameter thereby to form 'a mixing chamber downstream from. the Bernouilli constriction and upstream from the screen at least substantially equalling the volume within aid tubular structure. IR I!