United States Patent
`
`[‘19]
`
`Jackson, deceased et a1.
`
`[54]
`
`[75]
`
`INTERNAL COMBUSTION ENGINE
`SYSTEM AND OPERATION
`‘
`
`Inventors: Hugh R. Jackson, deceased, late of
`Fullerton, Calif, by Ellin E. Jackson,
`executrix; Robert H. Haas, Fullerton,
`Calif.
`
`[73] Assignee: Union Oil Company of California,
`Los Angels, Calif.
`
`[21] Appl. No.: 425,170
`
`[22] Filed:
`
`Dec. 14, 1973
`
`Related US. Application Data
`
`[63]
`
`Continuation of Ser. No. 128,874, Mar. 29, 1971, abanv
`cloned.
`
`
`[51]
`Int. C1.2 .......................... FOZM 13/04
`[52] US. Cl. .......................................... 123/3
`[58] Field of Search .................... 123/127, 133, 139, 3
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`1,559,216
`1,576,766
`
`10/1925 Woolson .............................. 123/127
`3/ 1926 Kloepper ............................. 123/127
`
`[11]
`
`[45]
`
`4,220,120
`
`Sep. 2, 1980
`
`2,098,575
`2,865,355
`2,940,435
`3,021,681
`3,688,755
`
`Flamini ................................ 123/127
`11/1937
`12/1958 Hilton ........
`123/139 R
`6/1960 Nemec etal.
`123/139 R
`2/1972
`Perry .................
`123/133 R
`9/1972 Grayson etal. ....................... 123/ 127
`
`
`
`Primary Examiner—~Wendell E. Burns
`Attorney, Agent, or Firm—Gregory F. Wirzbicki; Dean
`Sandford
`
`ABSTRACT
`[57]
`An internal combustion engine operating method and
`system include provisions for on-site fuel separation,
`accumulation of the resultant fractions, and an auto-
`matic control of engine fuel feed composition and air-
`to-fuel ratio in response to factors including engine
`operating temperature, engine load, liquid fuel tempera—
`ture and ambient conditions. These systems and meth—
`ods allow dramatic. improvement in engine operating
`performance, hydrocarbon emissions levels, full range
`fuel characteristics compatible with a given engine and
`flexibility of operation under varying conditions of load
`and ambient temperature.
`
`18 Claims, 1 Drawing Figure
`
`
`
`1-________
`Lug__________
`
`
`VW EX1014
`
`US. Patent No. 6,557,540
`
`
`
`VW EX1014
`U.S. Patent No. 6,557,540
`
`

`

`US. Patent
`
`Sep. 2, 1980
`
`4,220,120
`
`
`
`

`

`1
`
`4,220, 120
`
`INTERNAL COMBUSTION ENGINE SYSTEM AND
`OPERATION
`'
`-
`
`This is a continuation of application Ser. No. 128,874,
`filed Mar. 29, 1971, now abandoned.
`BACKGROUND
`
`.
`
`The major classifications of internal combustion en-
`gines have several characteristics in common regarding
`the effect and control of factors which influence the
`efficiency of fuel conversion to useable heat and/or
`mechanical energy and attendant effects such as noxious
`exhaust component emissions. Exemplary of engines to
`which this subject pertains are reciprocating piston-
`. type internal combustion engines including gasoline and
`1 diesel engines, rotating piston or Wankel engines, and to
`a lesser, although significant degree, turbo-jet engines
`operating on liquid turbine fuels.
`these various power
`. Almost without exception,
`. plants, regardless of the utility to which they are ap-
`plied, are expected to operate and are operated, under
`varying conditions of load, engine operating tempera-
`ture, ambient
`temperature and barometric pressure.
`« Due to the nature of these power plants, all of these
`variables are known to effect the efficienty of fuel con-
`' version to mechanical energy and the attendant produc-
`-~tion of undesirable byproducts or unreacted feed con-
`stituents in the form of exhaust emissions.
`For example, in the operation of a conventional spark
`“"3 ignition gasoline automotive engine, it is known that
`considerable reduction in air-to-fuel ratio, below that
`"required for operation at design operating temperatures,
`is-re‘quired when the engine is cold. This requirement is
`" “due to the relatively low volatility of the gasoline fuel at
`relatively low engine operating temperatures thus re-
`quiring the injection of higher amounts of fuel per unit
`' standard volume of air to obtain adequate performance.
`An equally well-known consequence of operating at
`‘ lower air-to-fuel ratios is the presence of dramatically
`increased amounts of unburned hydrocarbons and car-
`bon monoxide in the engine exhaust. Engine operation
`1resulting in the discharge of such amounts of unburned
`"combustible materials results in further contribution to
`already excessive air pollution problems but also results
`in inefficient engine operation and attendant increased
`Operating expense.
`However, another problem of a different nature, yet
`sstill related to fuel volatility characteristics, and with
`i which almost every motorist is familiar, is that of vapor
`lock occurring in systems employing liquid fuel pumps.
`This condition results when the fuel temperature within
`the pump exceeds that required to vaporize an amount
`of the hydrocarbon fuel sufficient to displace a signifi-
`,- cant part of the pump displacement volume. When the
`i-incipient vapor lock temperature is reached, i.e., that
`in temperature at which vaporization withinthe pump
`first occurs, the amount of fuel transfer through the
`system by the pump and the outlet pressure become
`subject to variation and are reduced below the design
`specifications of the system. These consequences result
`in uncontrollable fuel rate fluctuations through the car-
`buretor or other fuel induction means, eg, fuelinjec-
`tors, with attendant engine power surging. If the situa-
`tion persists by the continued formation of vapor phase
`in the fuel pump, the pump will finally fail to convey an
`amount of fuel necessary to maintain engine operation
`resulting in total shutdown.
`
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`2
`One solution to the problem of engine startup at rela-
`tively low temperatures is the provision of a highly
`volatile fuel. A fuel could be provided on which the
`engine could be started at moderately low temperatures
`without the necessity of excessive choking and atten-
`dant
`inefficient combustion and pollutant emissions.
`However, the degree of volatility of the selected fuel
`would depend upon the lowest anticipated engine oper-
`ating temperature. This factor is, of course, subject to
`considerable variation depending on geographic loca-
`tion, seasonable factors and altitude. In face, in this age
`of greatly increased mobility it is quite conceivable that
`an automotive engine might be expected to operate
`throughout extremes of high and low temperature and
`even differences in barometric pressure occasioned by
`changes in altitude within a period of only a few hours.
`It therefore becomes apparent that solving this particu-
`lar problem associated with fuel composition by provid-
`ing a fuel of predetermined composition designed to
`meet all demands is rather impractical due to the ex~
`tremes that the system might be expected to accommo-
`date.
`The modification of fuel compositions by the provi-
`sions of a greater proportion of light ends in the total
`fuel mixture also results in a fuel having a lower energy
`content on a volume basis. Consequently, if the volatil-
`ity of the total fuel is increased to solve or at least re—
`duce problems associated with operation at lower en—
`gine temperatures, such modifications are made at the
`expense of total power output for a given volume of fuel
`or, in the case of the automotive engine, shorter mileage
`ranges per tank of gas.
`This proposed solution to the problem of low engine
`operating temperatures is completely inconsistent with
`the problems encountered with fuel vapor lock dis-
`cussed above. The only reasonable solutions to the
`problem of fuel vaporization within the fuel pump itself
`are either cooling of the fuel pump and the fuel feed
`thereto or reducing the inherent volatility of the fuel.
`Cooling of the fuel system of course requires consider-
`able expense and the consumption of power in order to
`attain that objective. On the other hand, reduction of
`fuel volatility, which would solve the problem if suffi-
`cient reduction is achieved, would only serve to mag-
`nify the problems associated with cold engine opera-
`tion.
`Yet another drawback to the use of lighter fuels to
`prevent excessive exhaust emissions on startup and
`other attendant problems,
`is that the remedy creates
`another ill of the same nature. Higher volatility fuels
`have higher vapor pressures and consequently cause
`greater escape of vaporized hydrocarbons from storage,
`during transfer and in the original fuel system itself.
`Particular interest has developed in this problem with
`regard to automotive engines as indicated by several
`legislative proposals and acts at the state and federal
`level. For example, California Assembly Bill No. 81
`enacted in 1970 requires the California Air Resources
`Board to limit gasoline vapor pressure to 9 pounds Reid
`Vapor Pressure (RVP) maximum as required to reduce
`evaporative emissions when necessitated by seasonal
`and climatic conditions. The use and handling of a light
`volatility full range fuel would obviously not meet these
`requirements when imposed and would not comport
`with the legislative intent evidenced by this and similar
`enactments.
`
`Similar problems of significant magnitude are also
`encountered in the operation of liquid fuel turbines and
`
`

`

`4,220,120
`
`3
`diesel engines at operating temperatures substantially
`below design operating temperatures. For example,
`upon startup, diesel engines are known to exhibit char-
`acteristics similar to those discussed above regarding
`spark ignition gasoline engines. one telltale sign of cold 5
`diesel operation is the emission of a bluish exhaust
`smoke indicating the presence of substantial amounts of
`hydrocarbons in the exhaust. The problem is not as
`severe with regard to liquid fueled turbines although
`differences in the efficiency of fuel consumption deter- 10
`mined by the extent of unburned hydrocarbon emissions
`is readily detectable upon cold startup of such power
`plants. Here, again, the lack of complete fuel consump-
`tion is due primarily to the relatively slow rate of fuel
`vaporization upon exposure to the relatively cold com- 15
`bustion zones as opposed to the much higher rates of
`vaporization that result after the engine has reached
`design operating temperature.
`As in the case of spark ignition gasoline engines, the
`problems associated with low temperature operation of 20
`diesel and turbine power plants can be minimizedby the
`use of higher volatility fuels. However, several signifi-
`cant disadvantages result by the use of lighter fuels in
`such systems. The most significant of these problems is
`the substantial loss in heat energy per volume of fuel 25
`which results from the use of lower boiling fuels. This
`loss is particularly significant with relation to commer-
`cial diesel engines intended to operate through a widely
`variant range of load requirements. In other words, the
`use of a high energy low volatility fuel in a commercial 30
`diesel engine operating at design temperature under
`maximum load is a decided advantage. The use of
`higher volatility, lower energy fuels under such circum—
`stances results in significant power loss and the conse-
`quent requirement for larger power plants or other 35
`compensating modifications in operating conditions.
`An example of the variable fuel requirements of com-
`mercial diesel engines is posed by comparison of the
`operation of diesel powered trailer tractors at highway
`speeds or on grades as opposed to operation at rela- '40
`tively low speeds in populated areas. The higher energy
`fuels, of course, are desirable when operating under
`maximum load on highways and particularly on uphill
`grades. Such use is not particularly detrimental from the
`environmental standpoint due to the fact that the ex- 45
`haust emissions which are higher in unburned hydrocar-
`bons when operating on lower boiling fuels, are not
`emitted in congested areas. However, as the same truck
`passes into or through a populated area at reduced
`speed, power requirements are not nearly so severe so 50
`that the substitution of a higher volatility fuel would not
`unduly hamper engine operation. It would, however,
`markedly reduce the extent of exhaust emissions which
`is a very desirable objective in congested areas.
`A problem associated primarily with the operation of 55
`turbojet engines, particularly aircraft engines,
`is the
`extensive degree of particulate or “smoke” emissions
`usually encountered upon take off and landing. This
`characteristic is usually caused by lower air-to-fuel
`ratios employed under certain conditions. However, the 60
`level of smoke and/or particulate emissions in these
`systems can be markedly reduced by use of the methods
`and apparatus of this invention. To accomplish this
`result, the engine is operated on the lighter fraction
`when it is desirable to reduce emissions. The requisite 65
`control of fuel selection can be accomplished either
`manually or automatically. Automatic control can be
`effected by sensing the air-to-fuel ratio or parameters
`
`4
`related thereto, and directing flow of the light fraction
`to the fuel intake when that ratio isbelow a predeter-
`mined minimum. The heavy fraction can either be recy-
`cled to the full range fuel reservoir or accumulated and
`directed to the fuel intake at air-to-fuel ratios above said
`predetermined minimum.
`A collateral problem associated with the use of
`higher boiling fuels such as diesel and turbine fuels
`stems from the accumulation of paraffinic, e.g. waxy,
`hydrocarbons in the fuel filter during low temperature
`operation, e.g. startup. Essentially, all engine fuel sys-
`tems employ relatively fine filters in the fuel lines up-
`stream of the final induction means to reduce the possi-
`bility of fouling the engine or fuel inductor, e.g. carbu-
`retor. Relatively high molecular weight paraffins “con-
`dense out” on these filters causing increased pressure
`drop and even total shutdown. This problem, as several
`of the others already discussed, is most acute during low
`temperature operation. When design operating temper-
`atures are approached the solubility of these paraffinic
`materials is increased to the point that no condensation
`takes place. However, the methods of this invention can
`be employed to minimize or even eliminate such con—
`densation by operating the engine on a lighter fraction
`when a temperature indicative of the fuel temperature
`at the filter is below a predetermined minimum, e.g.
`100° F. After this temperature is exceeded, the fuel flow
`can be redirected as discussed hereinafter to supply
`either the full range fuel or the heavy fraction recov-
`ered during separation.
`.
`Consequently,
`it can be seen that the demands im-
`posed upon the operation of internal combustion, en-
`gines by the varying nature of conditions underywhiCh
`those systems are operated necessitates the selection of
`a fuel which, in a manner of speaking, is the best com-
`promise available to meet
`the. requirements of each
`operating extreme without magnifying problems which
`might occur at other operating conditions beyond toler-
`able limits. Consequently it is generally the case that‘a
`fuel of a specific composition will not be the best fuel
`for operation at one or more conditions of ambient
`temperature, engine operating temperature, barometric
`pressure or load.
`It is therefore one object of this invention to provide
`an improved internal combustion engine operating
`method and apparatus. Another object is the provision
`a method and apparatus for improving the operation of
`internal combustion engines under varied operating
`conditions. Another object is the provision of an im-
`proved method of apparatus for operating internal com-
`bustion engines on a relatively wide boiling range fuel
`of predetermined characteristics under varying condi-
`tions of ambient temperature, load and engine operating
`temperature. Yet another object of this invention is the
`provision of improved method and apparatus for the
`operation of gasoline and diesel engines under extreme
`conditions of ambient temperature, operating load or
`engine operating temperature on a hydrocarbon fuel
`designed for optimum utilization within a narrower
`range of operating conditions. Yet another object of this
`invention is the provision of an apparatus for the reduc-
`tion of air pollutant emissions attendant internal com-
`bustion engine operations. Still another object is the
`reduction of pollutant emissions from internal combus-
`tion engines without deleteriously effecting engine op-
`erating characteristics. Still another object is to enable
`the operation of internal combustion engines on a wider
`boiling range fuel mixture. A further object of this in-
`
`

`

`'5
`vention is the provision of a method and apparatus for
`operating internal combustion engines throughout a
`range of operating conditions of ambient temperature,
`engine operating load temperature while reducing req-
`uisite variations in air-to-fuel ratio. A further object is
`the reduction of vapor lock tendencies in liquid fuelled
`internal combustion engines.
`In accordance with one embodiment of this invention
`the operation of an internal combustion engine employ-
`ing a full range‘vaporizable liquid fuel mixture includes
`the steps ‘of separating a portion of the full range fuel
`into a lower boiling fraction and a higher boiling frac-
`tion and ‘operating the engine, at least in part, on the
`lighter fraction when the operating temperature of the
`engine is below a predetermined minimum. The charac-
`teristics of the lighter boiling fraction, e.g. boiling point
`range and the temperature level at Which the lighter
`fraction is passed as fuel to the engine, are determined to
`enable efficient, smooth engine operation atrelatively
`low temperatures such as those encountered upon
`startup without the necessity of substantially decreasing
`the air-to-fuel ratio thereby avoiding higher exhaust and
`carbon monoXide emission levels.
`.
`.
`In accordance with another embodiment, the heavy
`fraction is at least partially accumulated during the
`operation of the engine and passed to, the engine as fuel
`through a liquid fuel pump when conditions such as
`temperature and pressure indicative of the tendency of
`the fuel to vaporize within the fuel pump indicate that
`incipient vaporization or vapor lock conditions are
`being approached or have been exceeded. This method
`of operation serves to prevent or at least reduce the
`vapor locking tendencies observed at higher operating
`or ambient temperatures or under reduced operating
`pressures. Vapor lock problems associated with pres-
`sure variation are usually encountered upon changeskin
`external pressure, i.e., barometric pressure occasioned
`by significant changes in elevation.
`In accordance with another embodiment, the light
`and heavy fractions are at least partially accumulated
`during engine operation above the predetermined mini-
`mum temperature. These constituents are then em-
`ployed either alone or in admixture with other fuel
`‘ components under conditions of light or heavy load to
`satisfy power requirements or reduce hydrocarbon and
`carbon monoxide emissions.
`.
`In‘another embodiment an internal combustion en-
`gine is operated on a relatively high boiling hydrocar-
`bon fuel containing an amount of lower boiling constitu-
`ents insufficient to enable utilization of the full range
`fuel in conventional systems under all extremes of oper-
`ating conditions by separating at least a portion of the
`fuel into a lighter fraction at least a portion of which is
`accumulated and passed to the engine as fuel when a
`temperature indicative of the operating temperature of
`the engine is below a predetermined minimum. This
`system enables the effective use of fuels which could
`not otherwise be employed in a given system. For exam-
`ple, in this embodiment, the isolated lower boiling frac-
`tion could be employed in addition to variation in air-to-
`fuel ratio at relatively low temperatures to afford
`smooth engine operation even under load without stall-
`ing or skipping.
`.
`The several concepts of this invention can be better
`understood by reference to the drawing which is a
`schematic illustration of one embodiment of this inven-
`tion combining several of the concepts disclosed herein.
`
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`_ Referring now to the drawing, a full range liquid fuel
`is supplied-to the system from reservoir 1 illustrated in
`this figure as a fuel tank. However, it should be under-
`stood that the full range fuel could be supplied directly
`to the system by conduit from a remote source in the
`case of a fixed engine installation. The full range fuel
`will of course vary depending upon the characteristics
`of. the engine. For example, spark ignition gasoline en-
`gines envisioned within the concepts of this invention,
`generally employ fuels boiling primarily between 50°
`500° F., usually between about 80° and 450° F. When a
`primary objective in operation of the installation is the
`prevention of air pollutant emissions when operating
`under extreme conditions such as the relatively low
`temperatures encountered during startup, it is also pref-
`, erable that the full range fuel contain at least about 10
`volume percent of hydrocarbon constituents boiling
`below about 200° F., preferably below about 150° F. In
`contrast, the fuels usually employed in the operation of
`diesel engines usually boil between about 150° and 600°
`F.‘ Similar boiling range fuels are employed in the oper-
`ation of turbojet or turboprop engines. However, larger
`diesel engines such as those employed in diesel locomo-
`tives, are designed to accommodate even heavier fuels
`containing constituents boiling up to about 700° F. In
`each situation it is desirable that the selected fuel should
`
`contain at least about 10 volume-percent of constituents
`boiling within a range on which the engine can be oper-
`ated at the lowest anticipated operating temperature
`without excessive variation in air-to-fuel ratio. The
`
`boiling point ranges of these fuels will usually be in
`excess of about 100° F., preferably in excess of about
`200° F.
`.
`
`In this embodiment, the full range fuel is passed from
`'
`reservoir 1 via conduit 2 to a four-way valve 3, conduit
`4, liquid fuel pump 5, line 6, and fuel induction means
`such as carburetor 7 to the engine 8. This alignment of
`fuel passage from the fuel source to the engine is estab-
`lished when the engine operating conditions are such as
`‘to enable efficient operation on the full range fuel. The
`controlling variable in this regard is usually engine
`operating temperature. However, operating load is also
`a factor in some situations as will be discussed later. A
`portion of the full range fuel leaving liquid fuel pump 5
`is passed via line 9 and valve 10 to evaporator 11. The
`evaporator is operated at a temperature sufficient to
`produce a vapor phase comprising the desired lower
`boiling fraction. This fraction usually constitutes less
`than about 50 volume-percent and preferably less than
`30 volume-percent of the full range feed. As a general
`rule, the 50% boiling point of the lighter boiling frac-
`tion will be at least about 50° F. below the 50 volume
`percent boiling point of the full range feed. This usually
`corresponds to a maximum boiling point below 300° F.,
`preferably below 250° F. The exact definition of the
`maximum’boiling point will of course depend upon the
`nature of the engine employed, e.g., gasoline spark igni-
`tion, diesel, etc., and the extremes of operating condi-
`tions anticipated. The most significant consideration in
`this latter regard is the minimum temperature at which
`the engine will be operated. That limit in turn is usually
`primarily a function of geographical and seasonal con-
`ditions.
`The combination of liquid and vapor phase thus pro—
`duced in evaporator 11 is passed by way of conduit 12
`to separator 13. Any one of numerous available forms of
`apparatus effective for separating vapor and liquid pha-
`ses can be employed for this purpose. The temperature
`
`
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`

`

`7
`in separator 13 should be approximately the same as that
`existing in evaporator 11 in order to maintain the de-
`sired degree of separation. However, any means by
`which the full range fuel can be separated into the de-
`sired lighter and heavier fractions can be employed
`within the concept of this invention. For example, the
`evaporator and separator functions can be performed in
`a unitary apparatus rather than by the two part appara-
`tus illustrated in the figure.
`The lower boiling fraction is removed from the sepa-
`rator by way of conduit 14 and is passed either in vapor
`phase or as liquid phase following condensation to the
`light fraction accumulator 15 wherein at least a portion
`of the lower boiling fraction is accumulated during
`operation of the system. Provision can be made for
`condensing the vapor phase lighter fraction recovered
`from separator 13 either within accumulator 15 or prior
`to introduction of that fraction to the accumulator. In
`another embodiment, provision can also be made for
`passing the vaporous or condensed lighter fraction di-
`rectly to the full range fuel reservoir 1. In the alterna-
`tive the condensed lighter fraction can be passed di-
`rectly to the fuel induction means such as carburetor 7.
`In either event, the excess portion of the lower boiling
`fraction can be returned to the full range fuel reservoir
`1 by way of overflow line 17 if desired. This procedure
`is required when the separator system is operated con-
`tinuously during the operation of the engine without
`complete depletion of the lower boiling fraction at a
`rate equivalent to the rate at which it is produced. How-
`ever,
`in the embodiment
`illustrated in the drawing,
`provision is made for sensing the amount of lighter
`fraction accumulated in reservoir 15 by means of liquid
`level detector 26. The signal developed by detector 26
`can be passed by control circuit 27 to controller 28 and
`valve 10 to discontinue flow of the full range fuel to the
`evaporator and separator when the level of accumu-
`lated fraction in reservoir 15 reaches a predetermined
`level.
`.
`The lighter fraction is then passed as required by way
`of line 16, valve 3, and lines 4 and 6 to the power plant
`'8.
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`The heavier fraction recovered from the'separator 13
`is passed by way of line 18 to reservoir 19 having an
`optional
`liquid level indicator 23 and off-on control
`valve 22 for controlling the recycle of the heavy frac-
`tion by way of line 21 to the full range fuel reservoir 1.
`In an alternative embodiment, the level indicator 23 and
`control valve 22 can be replaced by a simple overlow
`recycle system if desired. Heavy fraction reservoir 19
`can even by eliminated altogether with direct recycle of
`the heavy fraction to reservoir 1 when it is not desirable
`to accumulate at least a portion of the heavy fraction.
`However,
`in this embodiment means is provided for
`passing the accumulated heavy fraction by way of pipe
`20, multidirectional control valve 3 and line 4 to pump
`5 when desired.
`In the illustrated case, the power plant 8 is a spark
`ignition gasoline engine to which the fuel is introduced
`via a carburetor 7. The great majority of carburetors
`employed in such systems are provided with fuel reser-
`voir or bowls within the carburetor itself that are con-
`tinuously refilled during operation. However, it may be
`desirable to remove the fuel retained in the carburetor
`reservoir after shutdown and prior to initiation of the
`next startup if the fuel retained in the reservoir is either
`the full range fuel, the heavy fraction or a combination
`thereof. Consequently,
`in this embodiment means is
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`8
`provided for passing the fuel retained in the carburetor
`bowl via valve 38 and lines 39 and 21 to the fuel reser-
`voir 1. Several alternatives are available in the opera-
`tion of this recycle system. For example, the residual
`fuel retained in the carburetor float. chamber can be
`recycled automatically after shutdown. On the other
`hand, as illustrated in this embodiment, recycle of the
`retained fraction can be controlled as a function of en-
`gine temperature. Temperature, sensing means 36 de—
`tects a temperature indicative of the engine temperature
`and passes that signal through control circuit 37 to
`valve 38. When the engine temperature is below a pre-
`determined minimum, control valve 38 is opened allow-
`ing recycle of the heavier fraction retained 'in carbure-
`tor 7 toreservoir 1. However, if the engine temperature
`exceeds that predetermined minimum such that
`the
`engine can be effectively restarted and operated on the
`full range fuel without significant variation in air-to-fuel
`ratio, control valve 38 remains closed thereby enabling
`direct use of the fuel retained in the carburetor bowl.
`Provision is also made for controlling the flow of fuel
`through line 9 to evaporator 11 in response to the en-
`gine operating temperature. This control feature is ac-
`complished by passing the temperature signal devel-
`oped by detector 36 via control circuit 40 to controller
`28 operating on valve 10. When the engine operating
`temperature is below the noted predetermined mini-
`mum such that lighter boiling fuel is passed to the en-
`gine upon startup, valve 10 is closed so as to prevent
`recycling of the lighter fractiOn through the evaporator
`and separator.
`Another aspect includes control of flow of higher
`boiling fraction to the fuel pump and engine in response
`to the fuel temperature within fuel pump 5. This pump,
`usually a positive displacement
`liquid fuel pump,
`is
`preferably electrically operated in order to enable rapid
`introduction of fuel to the carburetor 7 When provision
`is made for dumping the carburetor bowl prior to
`startup at relatively low temperatures. A temperature
`indicative of the fuel temperature in the pump related to
`the incipient vapor lock temperature of the full range
`fuel is detected by temperature detector 33 and is passed
`by way of control circuit 34 to controller 30 operating
`on multidirectional valve 3. Controller 30 also receives
`signals indicative of engine operating temperature by
`way of control circuit 35, and signals indicative of the
`presence or absence of light and heavy fractions by way
`of circuits 29 and 25 respectively. Manual controller 31
`is employed to override the signals otherwise received
`by controller 30 and provides for the alternative of
`manually controlling multidirectional valve 3 and se-
`lecting the desired fuel source accordingly.
`For purposes of describing the operation of the entire
`system, it will be assumed that the engine is started at a
`temperature below the predetermined minimum. This
`temperature will usually be set as a function of the tem-
`perature at which the full range fuel is substantially
`vaporized upon introduction into the combustion cham-
`bers within the engine. In the case of most water cooled
`spark ignition gasoline engines this temperature corre-
`sponds to a coolant temperature of approximately 110°
`F. Under these circumstances, temperature indicator 36
`will direct valve 38 to open thereby dumping the carbu-
`retor fuel reservoir. A similar signal passed by way of
`circuit 35 to controller 30 will direct multi-directional
`valve 3 to align conduits 16 and 4 thereby drawing
`lower boiling fraction from reservoir 15 while at the
`same time blocking fuel flow through conduits 2 and 20
`
`

`

`
`
`9
`from reservoirs 1 and 19 respectively. However, provi-
`sion can also be made for proportioning the amount of
`lighter fraction and full range fuel'fed to the engine on
`startup depending on the differential between the indi-
`cated engine temperature and the predetermined set
`point, e. g., minimum required operating temperature. In
`accordance with that alternative valve 3 could be set to
`allow fuel to be drawn simultaneously from reservoirs 1
`and 15 in accordance with the differential between the
`actual and predetermined minimum temperatures.
`However, for purposes of simplicity this embodiment
`will be limited to consideration of a system employing
`only the lighter fraction upon startup at temperatures
`below the prescribed minimum.
`.
`The engine operating temperature will determine the
`position of multi-way valve 3 unless the supply of ligh-
`ter fraction in reservoir 15 is insufficient. In that event,
`indicator 26 will detect the absence of fluid in accumu-
`lator 15 sending a corresponding signal via circuit 29 to
`controller 30 and reorienting valve 3 to align conduits 2
`and 4 allowing fuel to be drawn from full range reser-
`voir 1. At temperatures below the prescribed minimum
`valve 10 will be closed to prevent passage of fuel
`through the evaporator curcuit.
`After a period of engine operation sufficient to raise
`the engine operating temperature above the predeter-
`mined minimum, valve 3 will be reset to align conduits
`2 and 4 thereby drawing fuel from the full range reser-
`‘voir. In addition, valve 10 will be opened to allow pas—
`sage of fuel through the evaporator and separator with
`. attendant accumulation of light and heavy