US3640256A

US3640256A - System for preconditioning a combustible vapor

Info

Publication number: US3640256A
Application number: US82647A
Authority: US
Inventors: Charles Mangion
Original assignee: National Aeronautics and Space Administration NASA
Current assignee: National Aeronautics and Space Administration NASA
Priority date: 1970-10-21
Filing date: 1970-10-21
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08

Abstract

A system particularly adapted for use in preconditioning combustible vapors for delivery to internal combustion engines, characterized by a system housing including therein a full-flow bore communicating with a bypass conduit and having a vapor heater arranged therewithin, whereby a combustible vapor selectively is mixed and heated to a predetermined temperature as it is delivered in a continuous flow through the system. A particular feature of the invention resides in a provision of an improved control system having a reduced number of moving parts, and including a provision of fluidic bias ports, for imposing directional control on an established flow of vapor and directing predetermined portions of the flow across a heater, whereby the vapor selectively is preconditioned for enhancing subsequent combustion.

Description

United States Patent Low et al.

[ Feb. 8,1972

[54] SYSTEM FOR PRECONDITIONING A COMBUSTIBLE VAPOR 22 Filed: Oct. 21,1970

211 Appl.No.: 82,647

3,441,008 4/1969 Nelson ..123/52M 3,456,634 7/1969 Nelson ..l23/l22 AB Primary Examiner-Al Lawrence Smith Attorney-John R. Manning, .1. H. Warden and Monte F. Mott ABSTRACT A system particularly adapted for use in preconditioning combustible vapors for delivery to internal combustion engines, characterized by a system housing including therein a full-flow bore communicating with a bypass conduit and having a vapor heater arranged therewithin, whereby a combustible vapor selectively is mixed and heated to a predetermined temperature as it is delivered in a continuous flow through the system. A particular feature of the invention resides in a provision of an improved control system having a reduced number of moving parts, and including a provision of fluidic bias ports, for imposing directional control on an established flow of vapor and directing predetermined portions of the flow across a heater, whereby the vapor selectively is preconditioned for enhancing subsequent combustion.

9 Claims, 5 Drawing Figures klh CHARLES MA NG/ON A ORNEKS SYSTEM FOR PRECONDITIONING A COMBUSTIBLE VAPOR ORIGIN OF INVENTION The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; 42 U.S.C. 2457).

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to systems which employ the principles of fluidics, and more particularly to a system adapted for use in achieving a preheating of a combustible vapor as the vapor is delivered from a mixing chamber to a combustion chamber, whereby the vapor is preconditioned for enhancing combustion and thus impeding generation of noxious exhaust as combustion is achieved.

2. Description of Prior Art The prior art is replete with various types of fuel-air mixing chambers, including numerous systems designed for mixing and warming air and atomized fuel to provide a highly combustible mixture of fuel and air. However, the tendency to experience incomplete combustion of fuel and air mixtures continues to plague designers of internal combustion engines, particularly those engaged in the research and design of systems calculated to reduce the level of atmospheric contamination. Incomplete combustion has long been recognized as a prime source of noxious gases which tend to contaminate the atmosphere. While exhaust emission control systems presently are available for use in controlling the emission of noxious exhaust from internal combustion engines such systems have met with only limited success.

A suggested corrective technique currently under consideration is based upon achieving an increase in the completeness of combustion, whereby the resulting emission of unburned hydrocarbons is substantially reduced. As is well recognized, it is possible to improve completeness of combustion of a fuel-air mixture by affording the mixture a more thorough mixing, as well as through preheating the mixture.

Various attempts have been made to provide improved systems for preconditioning fuel-air mixtures as the mixtures are delivered from a mixing chamber, or carburetor, to a combustion chamber of an internal combustion engine. Such systems normally are designed to preheat and homogenize the fuel-air mixture prior to its introduction into the combustion chamber. Such systems, however, tend to be impractical due to their level of complexity, and quite often require highly skilled operating and maintenance personnel.

Accordingly, there currently exists a need for an improved, practical system, which readily is employable in preconditioning fuel-air mixtures, particularly suited for preheating and homogenizing fuel-air mixture while employing a minimal number of movable components.

OBJECTS AND SUMMARY OF THE INVENTION It therefore is an object of the instant invention to provide a system for reducing emission of noxious exhaust from internal combustion engines.

It is another object of the instant invention to provide a fluidic system for controlling a flow of combustible vapor to an internal combustion engine of an automotive vehicle.

It is another object to provide an improved system adapted to be mounted on existing vehicles for use in preheating fuelair' vapor mixtures, while employing a reduced number of moving components.

Another object is to provide a fluidic system for controlling a flow of combustible vapor as it is discharged from a fuel-air mixing chamber, through a preheating unit to a combustion chamber, whereby an increased propensity for experiencing complete combustion is imparted to the vapor.

Another object is to provide a fuel-air delivering system,

having a multiplicity of fluidic bias ports suitably arranged for imposing directional control on an established flow of fuel-air vapor as it is delivered relative to a vapor heating system.

Another object is to provide a unique fluidic system including therein a vapor preconditioning unit consisting of a unique association of structural components particularly suited for use in preheating and mixing combustible vapors prior to their delivery to combustion chambers.

These and other objects and advantages are achieved through the use of a simplified fluidic system which includes a housing adapted to be interposed between a carburetor and an intake manifold for an internal combustion engine and including therewithin a full-flow bore through which is established a flow of vaporized fuel-air mixture, a bypass conduit operatively communicating with the bore at longitudinally spaced ports, a heater operatively associated with an engine exhaust system and seated within the conduit, and a multiplicity of bias ports operatively associated with the bore in a manner such that as the velocity of the flow of fuel-air mixture through the bore is varied, and the bias ports selectively are closed, predetermined quantities of the flow are diverted from the bore and caused to pass through the conduit to be preheated, prior to being delivered from the bore to the intake manifold.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary end view of an internal combustion engine of a type frequently employed as an automotive engine and with which the fluidic system of the instant invention can operatively be associated.

FIG. 2 is a sectioned elevation of the fluidic system which embodies the principles of the present invention illustrating an established flow path for a flow of a fuel-air mixture when its associated engine is operating in a low-output mode of operation.

FIG. 3 is a cross-sectional elevational view of the system of FIG. 2, illustrating a flow path established for a flow of a fuelair mixture as its associated engine is operated in a highoutput mode of operation.

FIG. 4 is a cross-sectional elevational view of the system of FIGS. 2 and 3, illustrating an established flow path for a flow of fuel-air mixture as its associated engine is operated in a cold-start, high-output mode of operation.

FIG. 5 is a cross-sectional elevational view of the system of FIGS. 2 through 4, illustrating a flow path for a flow of a fuelair mixture as its associated engine is operated in a high-acceleration mode of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 an internal combustion engine, generally designated 10. As illustrated, the engine 10 includes a carburetor, generally designated 12, and an intake manifold, generally designated 14, each being of any suitable design. Between the carburetor l2 and the intake manifold 14 there is disposed a fluidic system 16, which embodies the principles of the instant invention and through which is delivered a flow of a substantially vaporized fuel-air mixture as the mixture is derived from the carburetor l2 and delivered to the intake manifold 14 of the engine 10.

Since the engine 10 forms no specific part of the instant invention and is of any suitable design, a detailed description thereof is omitted. However, it is to be understood that such engines normally include a plurality of cylinders, not shown, within which fuel-air mixtures are burned. As the mixtures are burned, a resulting mixture of exhaust gases is emitted through an exhaust system, illustrated as exhaust manifolds I8.

The engine 10 preferably is a variable-speed engine adapted to be driven in various modes of operation, including an idle or a low-output mode, a high-output mode, a cold-start mode, and a high-acceleration mode of operation. The instantaneous speeds at which the engine is operated necessarily determine the instantaneous quantity of fuel-air mixture which must be delivered to the engine via the intake manifold 14. Accordingly, the speed at which the engine is operated serves to dictate the velocity at which the fuel-air mixture is delivered to the manifold. Since this phenomenon is well known and thoroughly understood by those familiar with the design and operation of internal combustion engines, a detailed description thereof is omitted in the interest of brevity.

As best illustrated in FIG. 1, the system 16 includes a housing 20 which is fabricated employing any suitable technique or combination of techniques, including casting and machining. The housing 20 is provided with amounting flange 22 which is of an annular configuration and seats adjacent to a manifold intake port 23. The intake port 23 is of a suitable configuration, as is normally employed in the delivery of a fuel-air mixture from the carburetor 12 to the manifold 14. The housing 20 also includes a mounting flange 24, also of an annular configuration, particularly suited for receiving thereon the carburetor 12 in a manner such that the carburetors delivery or mixture discharge port 25 is permitted to communicate with the intake port 23 through a full-flow bore 26 extended through the housing 20.

The bore 26, in effect, is defined by an internal surface 27 and serves to accommodate a passage of streams of vaporized fuel-air mixtures as they are acquired from the carburetor 12 and delivered to the intake manifold 14. Of course, it is possible that small droplets of atomized liquid including fuels, airborne moisture and the like can inadvertently be mixed with the vaporized fuel-air mixtures.

In order to preheat and thus precondition the vaporized fuel-air mixture for purposes of increasing completeness of combustion, the housing 20 also includes a heating unit 28 which serves to preheat selected quantities of the vaporized mixture prior to its delivery to the intake manifold 14. This heating of the mixture serves to assure that the mixture is completely vaporized and homogenized for increasing the propensity of the mixture to achieve complete combustion.

The heating unit 28 is provided with a conduit 30, preferably designed to include an arcuate segment 31 interposed between an intake opening 32 and a discharge opening 34 which communicate with the bore 26 and through which selected quantities of vaporized fuel-air mixture are delivered prior to a subsequent delivery thereof to the intake manifold 14.

Within the conduit there is disposed a plurality of fins 36 which serve as heat-transfer members for delivering heat to the vaporized mixture as the mixture is caused to progress through the conduit 30. Since these fins operatively are heated in any suitable fashion, the particular manner in which heat is transferred thereto is deemed a matter of convenience, dictated by the relative location of the fluidic system 16 with respect to heat input devices, including the exhaust manifold 18 and its associated conduits. Therefore, it is to be understood that the particular system employed in heating the flow of vaporized mixture as it is passed through the heating unit 28 is a matter of convenience and can be varied as found practical.

Preferably, the fins 36 are fabricated from a material which is a particularly good heat conductor and are associated with the exhaust manifold 18 in a manner such that heat is conducted from the engines stream of exhaust to the fins 36 for achieving a heat exchange with the vaporized mixture as it is caused to flow through the heating unit 28. As illustrated, each of the fins 36 includes a plurality of tubular conduits 38 through which heated exhaust gases are delivered in order that a heat exchange be achieved between the vaporized mixture and the exhaust for thus heating and thus preconditioning the vaporized mixture as it is delivered along a tortuous path defined by the conduit 30.

In order to achieve the desired delivery of heated exhaust gases through the tubular conduits 38, a bypass conduit 40 is connected with one of the exhaust manifolds l8 and coupled with the tubular conduits 38 in any suitable manner which permits the exhaust gases to be passed through the conduits 38 for purposes of heating the fins 36 through convection. Where found practical, the conduits 38 are associated with the conduit 40 through a simple manifold block 41 having multiple couplings associated with the

conduits

38 and 40.

Upstream of the intake opening 32, of the heating unit 28, there is provided a fluidic bias chamber 42 of a suitable configuration, concentrically related with the bore 26. The chamber 42 is provided with a pair of transversely disposed, coaxially related bias ports, including an acceleration bias port 44 and a cold engine bias port 46. The acceleration bias port 44 and the cold engine bias port 46 each communicates with ambient atmosphere, through a laterally extended tubular conduit, designated 48 and 50, respectively.

It is important to note that the acceleration bias port 44 is arranged in diametric opposition to the intake opening 32 of the heating unit 28, while the cold engine bias port 46 is disposed directly above the opening 32. Therefore, both the direction and the configuration of the flow of vaporized fuelair mixture are dictated by the velocity of the flow of ambient air established through the

bias ports

44 and 46, the velocity of the stream acquired from the carburetor 12, and the mechanical configuration of the biasing chamber 42 in accordance with recognized principles of fluidics.

Due to the fact that the principles of fluidics utilized by the instant invention are fully understood by those familiar with such systems, and that such systems can empirically be varied in a manner dictated by the specific operational requirements of a given system, a detailed mathematical description of the system is omitted in the interest of brevity. Of course, it is to be understood that as the engine 10 is operated a low pressure tends to develop within the manifold 14, causing vapor to he delivered through the bore 26. Should the

bias ports

44 and 46 simultaneously be closed, the total quantity of vapor delivered through the bore 26 is acquired from the carburetor 12. However, should either of the bias ports be opened to atmosphere, ambient air is extracted through the ports and caused to act against the periphery of the flow for thus causing the stream of vapor acquired from the carburetor to adhere to the wall of the bore 26 which oppositely is related to the open port.

lnterposed between the chamber 42 and each of the

bias ports

44 and 46 there is disposed a partial baffle plate 51 which serves to intercept streams of ambient air as it is delivered from the

ports

44 and 46. The surfaces of the partial baffle plates function to reduce the velocity of the stream and cause the air to enter the bore 26 above the level of the ports as they pass over the upper edge surface of the plates.

At the outermost or distal ends of the

conduits

48 and 50 there is provided a pair of

flapper valves

52 and 54, respectively. While other types of valving can be employed, it is preferred that the

flapper valves

52 and 54 be pivotally suspended by a suitable suspension pivot pin 56 in a manner such that the valves are suitably supported to pivotally seat and operatively seal the distal ends of the

conduits

48 and 50. Coupled to each of the

flapper valves

52 and 54, through an appropriate linkage 57, there is a solenoid 58 which preferably is coupled with a suitable source of electrical potential, not shown, and adapted to be energized through a selectively energizable circuit, also not shown.

Each linkage 57 includes an axially reciprocable output shaft 60 which is coupled to the solenoid 58 and secured to one end of an extended arm 62. The arm 62, in turn, fixedly is secured to one of the

flapper valves

52 and 54 in a manner such that as the associated solenoid 58 is energized, the shaft 60 axially is advanced for pivotally displacing the arm 62 for thereby causing the flapper valve to rotate relative to its pivot pin 56 to achieve a selective sealing of the

conduits

48 and 50.

It is particularly important to note that the internal surface 27 is provided with substantially opposed surface segments 64 and 66, These surfaces are located between the upper edge portions of the partial baffle plate 51 and the intake opening 32 and provide a fluidic interface, which, in conjunction with the stream of desired ambient air, serve to control the flow of fuel-air mixture along the surface 27 of the bore 26 in a manner consistent with known principles of fluidics.

In view of the foregoing, it should be apparent that the system 16 readily is adaptable for use with various types of internal combustion engines and that to couple the system with such engines involves only minor modifications and adjustments. Due to the fact that fuel-air mixture is preheated and homogenized, and thus preconditioned for achieving complete combustion, cleaner fuels having fewer additives readily are suited for use by the system, whereby still a further reduction in the generation of noxious exhaust gases is experienced as combustion occurs.

OPERATION It is believed that in view of the foregoing description, the operation of the fluidic system which embodies the instant invention will be readily understood and it will be briefly reviewed at this point.

With the fluidic system 16 operatively interposed between a carburetor l2 and an intake manifold 14, in the manner hereinbefore described, fuel delivery requirements, established by the various modes of operation operatively imposed on the associated internal combustion engine 10, are satisfied through a responsive operation of the system.

With particular reference to FIG. 2, it is noted that when the engine 10 is operating in a low-output mode of operation the

bias ports

44 and 46 are open to ambient atmosphere simultaneously. Hence, a stream of ambient atmosphere operatively is conducted through both of these ports and delivered to the chamber 42 as the enginell) is operated in a manner which develops a pressure drop within the intake manifold 14. When the engine 10 is operating in a low-output mode, as normally prevails at idle speeds, the quantity of fuel-air mixture consumed is minimal, hence the velocity of the flow of vaporized fuel-air mixture derived from the carburetor 12 is relatively low. Additionally, it should be apparent that when an engine is operating in the low-output mode, its combustion normally can be expected to be incomplete. Accordingly, a simultaneous opening of both of the

bias ports

44 and 46 causes the vaporized fuel-air mixture to adhere to the surface segment 66, whereupon a relatively large quantity of the flow of fuelair mixture, when compared to the engines intake requirement, is directed along the surface segment 66 and diverted throughthe intake opening 32 of the conduit 30. As the mixture enters the opening 32 it is caused to progress along a tortuous path across the fins 36 for purposes of effecting a heat exchange within the conduit. The fins 36, in turn, are heated in response to heat delivered thereto from the engines exhaust gases as they are acquired from the exhaust manifold 18 and delivered through the manifold block 41. As the vaporized mixture is passed over the fins 36, a heat exchange is achieved, whereby the vapor is preheated, vaporization of the mixture maximized, and the combustibility of the fuel-air mixture enhanced as its temperature is increased, all in accordance with known principles of combustion.

When the engine 10 is operating in a steady, high-output mode of operation, as normally prevails at moderate engine speeds, there exists a lesser need to stimulate combustion within the combustion chambers, due to the fact that maximized combustion normally is experienced when the engine is operating at moderate, but steady, engine speed. Hence, a relatively lesser quantity of the mixture need be delivered through the heating unit 28. Therefore, as the velocity of the flow of vaporized fuel-air mixture through the bore 26 is increased, an attendant reduction in the relative quantity of the fuel-air mixture being delivered through the heating unit 28 is experienced. This, of course, occurs because the mixture tends to separate from surface 66 at higher velocities. Consequently, the engine 10 can be operated at moderate speeds with both of the

ports

44 and 46 opened to ambient atmosphere, as illustrated in FIG. 3.

When it is found desirable to operate the engine 10 in a cold-start, but high-output mode, the cold engine bias port 46 is closed, as illustrated in FIG. 4'. Closure of this port occurs as an energization of a suitable electrical circuit, not shown, is effected in order to activate the associated solenoid 58, whereupon the associated shaft 60 is advanced for displacing the flapper valve 54 and then closing the distal end of the conduit 50. As closure of the port 46 occurs, flow of ambient air through the port is interrupted. Since the acceleration bias port 44 remains open, as best illustrated in FIG. 4, the stream of ambient air extracted through the port 44 acts against the stream of fuel-air mixture for causing the stream to adhere to the surface 66 adjacent to the opening 32. Due to the combined effects of the open port 44 and the velocity of the flow of the mixture, about 50 percent of the flow of fuel-air mixture is delivered through the opening 32 of the heating unit 28. Hence, a substantial increase in the temperature and homogeneity of the vaporized mixture is experienced before the mixture is delivered to the intake manifold 14 from the bore 26. Consequently, a maximized quantity of the fuel-air mixture is subjected to preconditioning in order that the engine 10 be permitted to operate in its most efficient manner, even though it is being operated in a cold-start mode of operation.

At accelerating speeds, wherein little or no preheating of the fuel-air mixture is required, the solenoid 58 associated with the flapper valve 52 is electrically energized, whereupon the flapper valve 52 is displaced to interrupt the flow of ambient air through the conduit 48, as best illustrated in FIG. 5. Consequently, the ambient air acts against the stream of fuelair mixture in the manner such that the mixture is caused to adhere to the surface segment 64 of the internal surface 27, opposite the bias port 46, whereupon the bulk of the vaporized fuel-air mixture is caused to be delivered directly from the carburetor 12, through the bore 26 without being diverted through the conduit 30.

It is to be understood that heating of the fuel-air mixture delivered to the engine 10 for operating the engine in its various operating modes can be varied and overlapped as overlapping operational conditions are encountered and found to be practical.

In view of the foregoing, it should be apparent that the instant invention provides a practical solution to a perplexing problem of achieving maximized combustion of fuel-air mixtures within an internal combustion engine, while employing a simplified system having minimal number of moving components.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred system, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the illustrative details disclosed.

What is claimed is:

1. A system for use in preconditioning a combustible vapor as the vapor is delivered to an internal combustion engine for enhancing its combustibility, comprising:

A. a system housing including means defining therewithin an axially extended bore adapted to conduct a stream of combustible vapor therethrough;

B. a heating unit operatively communicating with said bore adapted to receive vapor from the bore, transfer heat thereto, and to return the received vapor to said bore in a heated condition; and

C. a selectively operable fluidic system communicating with said bore operatively associated with the heating unit and adapted to divert vapor from said bore into said heating unit.

- 2. The system of claim 1 wherein said fluidic system includes means defining a pair of coaxially related, oppositely disposed, fluidic bias ports disposed upstream of said heating unit, and valve means operatively associated with said bias ports adapted to selectively close said ports.

3. The system'of claim 2 wherein said heating unit includes:

A. a fluid conduit having means defining a vapor intake opening and a vapor discharge opening disposed in direct communication with said bore, whereby vapor is accepted through said intake opening and discharged through said discharge opening; and

B. means including heat-exchanging fins disposed within said conduit adapted to heat combustible vapor received by said intake opening prior to a discharge thereof through said discharge opening.

4. A system for preheating a combustible mixture of fuel-air vapors, whereby the combustibility of the mixture is enhanced as the mixture is delivered from a carburetor to an internal combustion engine, comprising:

A. a system housing operatively associated with an internal combustion engine;

B. means defining within said housing a full-flow bore extended through said housing adapted to conduct an unobstructed flow of combustible vapor to the engine;

C. an arcuate conduit communicating at opposite ends with said bore for conducting selected portions of the flow along a path bypassing a portion of the bore;

D. a fiuidic control unit operatively associated with said conduit adapted to direct portions of the flow into said conduit; and

E. heating means operatively associated with said conduit for heating vapor directed into the conduit, whereby the vapor is heated and subsequently delivered from the system in a heated condition.

5. The system of claim 4 wherein said fluidic control unit comprises:

A. means defining a pair of diametrically opposed bias ports communicating with said bore upstream from said conduit, and adapted to accommodate a selected delivery of ambient air to opposite sides of said bore; and

B. selectively operable valve means operatively associated with said control unit and adapted to open and close said ports, whereby ambient air selectively is delivered through said ports for thereby directing determinable portions of said flow into said arcuate conduit.

6. The system of claim 5 wherein said combustible mixture of fuel-air vapors comprises a mixture of automotive fuel and air for use in internal combustion engines of a type normally employed in driving automobiles.

7. The system of claim 6 wherein said housing includes mounting means mounting the system in an interposed relationship between a delivery port of a carburetor and an intake manifold of an internal combustion engine mounted within an automobile.

8. A system adapted for use in preconditioning combustible vapors in a manner such that the propensity of the vapors for experiencing complete combustion is increased as the vapors are delivered from a carburetor to an intake manifold of an automotive, internal combustion engine comprising:

A. a system housing;

B. means defining within said housing a full-flow bore extended through the housing in direct communication with the carburetor and with the intake manifold and adapted to conduct an unobstructed flow of fuel-air vapors from the carburetor, through the housing, to the intake manifold;

C. a conduit operatively communicating with said bore, near its opposite ends, for conducting selected portions of the flow along a path bypassing a portion of said bore;

D. a heating unit disposed within said conduit adapted to heat the vapor as it is conducted through said conduit;

E. a fluidic control unit including means defining within said bore a pair of oppositely disposed bias ports arranged upstream of said conduit and adapted operatively to divert quantities of vapors from said stream into said conduit, whereby the diverted vapors are caused to be heated by said heating unit and subsequently returned to said bore;

and F. valve means operatively associated with said bias ports adapted to be manipulated for controlling the bias ports, whereby vapors are delivered to the intake manifold in a preheated condition in a manner dictated by the fluidic control unit.

9. The system of claim 8 wherein said heating means includes a plurality offins operatively associated with the engine exhaust system and adapted to deliver to said vapors heat delivered thereto by heated gases ofcombustion.

Claims

1. A system for use in preconditioning a combustible vapor as the vapor is delivered to an internal combustion engine for enhancing its combustibility, comprising: A. a system housing including means defining therewithin an axially extended bore adapted to conduct a stream of combustible vapor therethrough; B. a heating unit operatively communicating with said bore adapted to receive vapor from the bore, transfer heat thereto, and to return the received vapor to said bore in a heated condition; and C. a selectively operable fluidic system communicating with said bore operatively associated with the heating unit and adapted to divert vapor from said bore into said heating unit.

2. The system of claim 1 wherein said fluidic system includes means defining a pair of coaxially related, oppositely disposed, fluidic bias ports disposed upstream of said heating unit, and valve means operatively associated with said bias ports adapted to selectively close said ports.

3. The system of claim 2 wherein said heating unit includes: A. a fluid conduit having means defining a vapor intake opening and a vapor discharge opening disposed in direct communication with said bore, whereby vapor is accepted through said intake opening and discharged through said discharge opening; and B. means including heat-exchanging fins disposed within said conduit adapted to heat combustible vapor received by said intake opening prior to a discharge thereof through said discharge opening.

4. A system for preheating a combustible mixture of fuel-air vapors, whereby the combustibility of the mixture is enhanced as the mixture is delivered from a carburetor to an internal combustion engine, comprising: A. a system housing operatively associated with an internal combustion engine; B. means defining within said housing a full-flow bore extended through said housing adapted to conduct an unobstructed flow of combustible vapor to the engine; C. an arcuate conduit communicating at opposite ends with said bore for conducting selected portions of the flow along a path bypassing a portion of the bore; D. a fluidic control unit operatively associated with said conduit adapted to direct portions of the flow into said conduit; and E. heating means operatively associated with said conduit for heating vapor directed into the conduit, whereby the vapor is heated and subsequently delivered from the system in a heated condition.

5. The system of claim 4 wherein said fluidic control unit comprises: A. means defining a pair of diametrically opposed bias ports communicating with said bore upstream from said conduit, and adapted to accommodate a selected delivery of ambient air to opposite sides of said bore; and B. selectively operable valve means operatively associated with said control unit and adapted to open and close said ports, whereby ambient air selectively is delivered through said ports for thereby directing dEterminable portions of said flow into said arcuate conduit.

8. A system adapted for use in preconditioning combustible vapors in a manner such that the propensity of the vapors for experiencing complete combustion is increased as the vapors are delivered from a carburetor to an intake manifold of an automotive, internal combustion engine comprising: A. a system housing; B. means defining within said housing a full-flow bore extended through the housing in direct communication with the carburetor and with the intake manifold and adapted to conduct an unobstructed flow of fuel-air vapors from the carburetor, through the housing, to the intake manifold; C. a conduit operatively communicating with said bore, near its opposite ends, for conducting selected portions of the flow along a path bypassing a portion of said bore; D. a heating unit disposed within said conduit adapted to heat the vapor as it is conducted through said conduit; E. a fluidic control unit including means defining within said bore a pair of oppositely disposed bias ports arranged upstream of said conduit and adapted operatively to divert quantities of vapors from said stream into said conduit, whereby the diverted vapors are caused to be heated by said heating unit and subsequently returned to said bore; and F. valve means operatively associated with said bias ports adapted to be manipulated for controlling the bias ports, whereby vapors are delivered to the intake manifold in a preheated condition in a manner dictated by the fluidic control unit.

9. The system of claim 8 wherein said heating means includes a plurality of fins operatively associated with the engine exhaust system and adapted to deliver to said vapors heat delivered thereto by heated gases of combustion.