EP0400210A1 - Air-fuel mixture preparing device for internal combustion engine - Google Patents

Air-fuel mixture preparing device for internal combustion engine Download PDF

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Publication number
EP0400210A1
EP0400210A1 EP89118677A EP89118677A EP0400210A1 EP 0400210 A1 EP0400210 A1 EP 0400210A1 EP 89118677 A EP89118677 A EP 89118677A EP 89118677 A EP89118677 A EP 89118677A EP 0400210 A1 EP0400210 A1 EP 0400210A1
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EP
European Patent Office
Prior art keywords
fuel
nozzle
wall
rotationally symmetrical
internal combustion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP89118677A
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German (de)
French (fr)
Inventor
Martin Prof. Dr. Feldinger
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Mannesmann VDO AG
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Mannesmann VDO AG
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Publication of EP0400210A1 publication Critical patent/EP0400210A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M33/00—Other apparatus for treating combustion-air, fuel or fuel-air mixture
    • F02M33/02—Other apparatus for treating combustion-air, fuel or fuel-air mixture for collecting and returning condensed fuel
    • F02M33/04—Other apparatus for treating combustion-air, fuel or fuel-air mixture for collecting and returning condensed fuel returning to the intake passage
    • F02M33/06—Other apparatus for treating combustion-air, fuel or fuel-air mixture for collecting and returning condensed fuel returning to the intake passage with simultaneous heat supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M33/00—Other apparatus for treating combustion-air, fuel or fuel-air mixture
    • F02M33/02—Other apparatus for treating combustion-air, fuel or fuel-air mixture for collecting and returning condensed fuel
    • F02M33/025—Means not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M9/00—Carburettors having air or fuel-air mixture passage throttling valves other than of butterfly type; Carburettors having fuel-air mixing chambers of variable shape or position
    • F02M9/12—Carburettors having air or fuel-air mixture passage throttling valves other than of butterfly type; Carburettors having fuel-air mixing chambers of variable shape or position having other specific means for controlling the passage, or for varying cross-sectional area, of fuel-air mixing chambers
    • F02M9/127—Axially movable throttle valves concentric with the axis of the mixture passage
    • F02M9/133—Axially movable throttle valves concentric with the axis of the mixture passage the throttle valves having mushroom-shaped bodies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S261/00—Gas and liquid contact apparatus
    • Y10S261/56—Variable venturi

Definitions

  • the invention relates to a fuel-air mixture formation device for internal combustion engines with a rotationally symmetrical nozzle body which, together with a rotationally symmetrical throttle body displaceable in it, forms a convergent-divergent nozzle which opens into a radial diffuser, and in the vicinity of the narrowest cross section of the nozzle around it circumferential and opening into this gap is provided, in which at least one fuel supply line opens.
  • the fuel is fed across the entire circumference of the nozzle in a film-like manner transversely to the direction of flow of the air flowing through the nozzle.
  • the main mass of the fuel supplied is in the white tere consequence atomized by the air mass flowing transversely to the fuel film, the resulting droplet size decreasing with increasing speed of the air mass flow.
  • the fuel flowing in the radial gap adheres to its walls as a result of adhesion and remains adhering to the walls of the same in a more or less strong film even after it has entered the divergent nozzle area of the nozzle body.
  • the nozzle opens into a strongly outwardly curved radial diffuser, with the result that the fuel film in the area of curvature detaches in the form of larger droplets due to the low air speed there and the centrifuging effect, in contrast to the much smaller droplets in the core flow of the fuel Air mixture.
  • the result is a stronger fuel film in the intake manifold with the consequent disadvantage of an uneven mixture composition for the individual cylinders and for one and the same cylinder during successive work cycles, which leads to an unsteady load on the engine and causes changes in the average exhaust gas composition, so that even after Catalyst a deterioration in the exhaust gas quality is recorded.
  • the radial diffuser is formed by a region of the nozzle body which is curved outward in the direction of flow of the mixture and a wall, opposite the throttle body and rotationally symmetrical to the axis of rotation of the throttle body, of a component forming a structural unit with an intake manifold of the internal combustion engine, the wall has a curvature directed towards the throttle body.
  • the nozzle body is curved outwards from the narrowest cross section of the nozzle with minimal radii of curvature, if possible, and that the curvature directed towards the throttle body is curved so far with minimal radii of curvature in the direction of the throttle body that the diffuser function is caused by the Cooperation between the corresponding area of the nozzle body and the curved wall directed towards the throttle body is ensured.
  • the minimal radii of curvature of the area of the nozzle body and the wall ensure that there is no separation of the flow on the components flowing around and that the fuel film does not become detached in the form of larger droplets.
  • the outwardly curved region of the nozzle body is provided with a heating device.
  • the heating should begin as close as possible to the point at which the fuel is supplied, thus the gap that opens into the nozzle. It can be done, for example, electrically and / or - preferably - by a medium heated by the engine, in particular cooling water, lubricating oil, exhaust gas.
  • the heating device expediently being arranged in the immediate vicinity of the inner wall of the relevant section of the nozzle body, the fuel film on the inner wall evaporates almost completely, the more the stronger the wall of the nozzle body is heated.
  • the heating option thus further improves the aerodynamic advantages achieved by the special design of the radial diffuser. It is also considered appropriate, including the rotations to provide a symmetrical wall-mounted component with a heating device. This component can also be heated, for example, electrically and / or by a medium heated by the motor.
  • Reference number 1 denotes an imaginary longitudinal axis of the fuel-air mixture formation device, around which parts of this mixture formation device are formed symmetrically.
  • a nozzle body 2 with its inner wall 3 is essentially rotationally symmetrical.
  • the interior space delimited by the inner wall in the nozzle body tapers downwards continuously in its upper region 4 to a point at reference number 5 of the narrowest clear cross-section.
  • a radial diffuser 6 adjoins this at the bottom.
  • Air is applied to the fuel-air mixture formation device at the top via an air filter (not shown). The main air mass flow therefore flows in the direction of arrow L from top to bottom and then at right angles to it radially outwards.
  • a throttle body 8 which is likewise rotationally symmetrical about the longitudinal axis and is adjustable in the direction of the longitudinal axis according to double arrow A, is used in connection with the nozzle body.
  • An upper part of the throttle body widens continuously from above and opens into a substantial lower part of the throttle body, which tapers continuously from top to bottom.
  • the passage for the air mass flow between the nozzle body and the throttle body is thus narrowed the further the throttle body is moved downward.
  • the nozzle body forms a convergent-divergent nozzle together with the throttle body.
  • the wall of the nozzle body is provided with a fuel feed bore 9 which merges into a fuel gap 11 via a fuel ring channel 10.
  • the fuel gap lies in a cross-sectional plane in the area of the narrowest clear cross-section and has a gap opening 12 directed towards the interior of the nozzle body.
  • the gap opening like the circumferential fuel gap, thus extends over 360 °.
  • the fuel ring channel is designed with a relatively small flow resistance, while the fuel gap has a relatively high flow resistance.
  • air is introduced into the fuel gap under higher pressure, approximately under ambient air pressure.
  • the fuel gap is connected via an air ring duct 13 and bores 14 to an interior section, not shown in more detail, in the nozzle body, in which practically the air pressure in the environment prevails, while in the gap opening 12 there is an air pressure of approximately half the ambient pressure, and the air at this point flows at the speed of sound.
  • the air supply prevents the formation of vapor bubbles, since the fuel is practically under atmospheric pressure.
  • the air supply and the fuel gap adjoining it are dimensioned such that some air is mixed with the fuel in them. This gives the fuel emerging from the gap opening 12 a higher speed than without such an admixture of air. As a result, the fuel is supplied to the combustion air or the air masses stream evenly over the circumference of the nozzle body and film-like.
  • the radial diffuser is thus formed by an area of the nozzle body which is curved outward in the flow direction of the mixture and by a wall 15 which is opposite the throttle body and is rotationally symmetrical with respect to the axis of rotation of the throttle body and has a curvature 16 directed towards the throttle body.
  • the wall 15 is part of a component 17, which forms a structural unit 18 with a suction pipe 7 of the internal combustion engine.
  • the figure shows in concrete terms that the nozzle body with the throttle body downstream of the gap opening 12 forms the divergent area of the nozzle, which opens into the radial diffuser, the passage cross section of which tapers continuously up to its radial outlet opening 19, which represents the transition to the suction pipe 7.
  • the required curvature of the wall 15 in the direction of the throttle body is dependent on the fluidic conditions.
  • the operation of the radial diffuser according to the invention which is intended to prevent the air from detaching from the wall 3, is supported in that, in the device shown, both the outwardly curved region of the nozzle body and the component having the wall 15 with a heating device 20 or 21 are provided.
  • the heating device 20 has a heating channel 22 which is arranged in the nozzle body in the region of its inner wall and is of annular design and thus the inner wall completely surrounds the diffuser.
  • the heating duct is provided with an engine cooling water inlet 23 and an opposite engine cooling water outlet 24, the diffuser is thus heated by the hot engine cooling water.
  • the thermal resistance between the engine cooling water and the fuel-carrying ducts is kept as large as possible by constructive design of the fuel-air mixture formation device.
  • the nozzle body in the area of the fuel gap and the gap opening has a small wall thickness and an air-guiding cavity 25 which counteract undesired heating of the fuel, which ensures a high heating efficiency of the nozzle body in the area of the diffuser.
  • the heating causes the fuel film on the wall of the diffuser to evaporate almost completely.
  • the associated component 17 passes through a heating channel 26 with engine cooling water inlet 27 and engine cooling water outlet 28.

Abstract

The invention proposes an air-fuel preparing device for internal combustion engines having a rotationally symmetrical nozzle body (2) which, together with a rotationally symmetrical restrictor body (8) displaceable therein, forms a convergent-divergent nozzle, which opens into a radial diffusor (6). A fuel gap (11) into which at least one fuel feed line (9, 10) opens is provided in the vicinity of the narrowest cross-section (5) of the nozzle, enclosing this and opening into it. The radial diffusor is formed by an area of the nozzle body curved outwards in the direction of flow of the mixture and by a wall (15) of a component (17) facing the nozzle body, rotationally symmetrical to the axis of rotation (1) of the restrictor body and forming a modular unit (18) with an intake pipe (7) of the internal combustion engine, the wall having a curvature (16) directed at the restrictor body. By virtue of its design, the radial diffusor allows a fuel film, inevitably being deposited on the wall of the diffusor when the fuel is injected, to detach itself, thereby forming an improved mixture. <IMAGE>

Description

Die Erfindung betrifft eine Kraftstoff-Luft-Gemischbil­dungsvorrichtung für Verbrennungsmotoren mit einem rota­tionssymmetrischen Düsenkörper, der zusammen mit einem in ihm verschiebbaren rotationssymmetrischen Drosselkörper eine konvergent-divergente Düse bildet, die in einen Radial­diffusor mündet, und ein in der Nähe des engsten Querschnit­tes der Düse um diese umlaufender und in diese mündender Spalt vorgesehen ist, in den mindestens eine Kraftstoff­zuleitung mündet.The invention relates to a fuel-air mixture formation device for internal combustion engines with a rotationally symmetrical nozzle body which, together with a rotationally symmetrical throttle body displaceable in it, forms a convergent-divergent nozzle which opens into a radial diffuser, and in the vicinity of the narrowest cross section of the nozzle around it circumferential and opening into this gap is provided, in which at least one fuel supply line opens.

Je homogener das Kraftstoff-Luft-Gemisch bereits vor dem Eintritt in die Brennkammern des Motors durch die Gemisch­bildungsvorrichtung aufbereitet wird und je kleiner die in diesem Gemisch vorhandenen Kraftstofftröpfchen sind, um so kleiner wird der effektive Kraftstoffverbrauch und um so gleichmäßiger ist die Verbrennung nicht nur bei auf­einanderfolgenden Arbeitsspielen in ein und demselben Zylinder, sondern auch in sämtlichen Zylindern des Motors, um so höher wird die erzielbare Motorleistung.The more homogeneous the fuel-air mixture is processed by the mixture formation device before it enters the combustion chambers of the engine and the smaller the fuel droplets present in this mixture, the smaller the effective fuel consumption and the more uniform the combustion is, not only at successive work cycles in the same cylinder, but also in all cylinders of the engine, the higher the achievable engine performance.

Bei einer aus der DE 36 43 882 Al bekannten Gemischbil­dungsvorrichtung der genannten Art wird der Kraftstoff quer zur Strömungsrichtung der durch die Düse strömenden Luft filmartig über den gesamten Umfang der Düse zugeführt. Die Hauptmasse des zugeführten Kraftstoffes wird in der wei­ teren Folge durch die quer zum Kraftstoffilm strömende Luft­masse zerstäubt, wobei die entstehende Tröpfchengröße mit steigender Geschwindigkeit des Luftmassenstromes abnimmt. Der im Radialspalt strömende Kraftstoff haftet infolge Adhäsion an seinen Wandungen und bleibt auch nach dem Über­tritt in den divergenten Düsenbereich des Düsenkörpers in einem mehr oder weniger starken Film an den Wandungen des­selben haften. Die Düse mündet in einen stark nach außen gekrümmten Radialdiffusor, mit der Folge, daß sich der Kraftstoffilm im Krümmungsbereich wegen der dort nur ge­ringen Luftgeschwindigkeit und der auszentrifugierenden Wirkung in Form größerer Tröpfchen ablöst, im Gegensatz zu den ungleich kleineren Tröpfchen in der Kernströmung des Kraftstoff-Luft-Gemisches. Die Folge ist ein stärkerer Kraftstoffilm im Saugrohr mit dem hierdurch bedingten Nach­teil einer ungleichmäßigen Gemischzusammensetzung für die einzelnen Zylinder und für ein und denselben Zylinder bei aufeinanderfolgenden Arbeitsspielen, was zu einer instatio­nären Belastung des Motors führt und Veränderungen der mittleren Abgaszusammensetzung bewirkt, so daß auch nach dem Katalysator eine Verschlechterung der Abgasqualität zu verzeichnen ist.In a mixture formation device of the type mentioned known from DE 36 43 882 A1, the fuel is fed across the entire circumference of the nozzle in a film-like manner transversely to the direction of flow of the air flowing through the nozzle. The main mass of the fuel supplied is in the white tere consequence atomized by the air mass flowing transversely to the fuel film, the resulting droplet size decreasing with increasing speed of the air mass flow. The fuel flowing in the radial gap adheres to its walls as a result of adhesion and remains adhering to the walls of the same in a more or less strong film even after it has entered the divergent nozzle area of the nozzle body. The nozzle opens into a strongly outwardly curved radial diffuser, with the result that the fuel film in the area of curvature detaches in the form of larger droplets due to the low air speed there and the centrifuging effect, in contrast to the much smaller droplets in the core flow of the fuel Air mixture. The result is a stronger fuel film in the intake manifold with the consequent disadvantage of an uneven mixture composition for the individual cylinders and for one and the same cylinder during successive work cycles, which leads to an unsteady load on the engine and causes changes in the average exhaust gas composition, so that even after Catalyst a deterioration in the exhaust gas quality is recorded.

Es ist Aufgabe der vorliegenden Erfindung, eine Vorrich­tung der genannten Art so weiter zu bilden, daß eine verbes­serte Gemischbildung gewährleistet ist.It is an object of the present invention to develop a device of the type mentioned so that an improved mixture formation is ensured.

Gelöst wird die Aufgabe dadurch, daß der Radialdiffusor durch einen in Strömungsrichtung des Gemisches nach außen gekrümmten Bereich des Düsenkörpers und eine, dem Drossel­körper gegenüberliegende, zur Rotationsachse des Drossel­körpers rotationssymmetrische Wandung eines eine Bauein­heit mit einem Saugrohr des Verbrennungsmotors bildenden Bauteils gebildet ist, wobei die Wandung eine auf den Dros­selkörper gerichtete Wölbung aufweist.The object is achieved in that the radial diffuser is formed by a region of the nozzle body which is curved outward in the direction of flow of the mixture and a wall, opposite the throttle body and rotationally symmetrical to the axis of rotation of the throttle body, of a component forming a structural unit with an intake manifold of the internal combustion engine, the wall has a curvature directed towards the throttle body.

Grundlegend ist für die vorliegende Erfindung, daß der Düsenkörper nach Möglichkeit ab dem engsten Querschnitt der Düse bei minimalen Krümmungsradien nach außen gekrümmt ist und daß die auf den Drosselkörper gerichtete Wölbung so weit bei minimalen Krümmungsradien in Richtung des Dros­selkörpers gewölbt ist, daß die Diffusorfunktion durch das Zusammenwirken des entsprechenden Bereiches des Düsenkör­pers und der auf den Drosselkörper gerichteten, gewölbten Wandung gewährleistet ist. Die minimalen Krümmungsradien des genannten Bereiches des Düsenkörpers und der Wandung stellen sicher, daß an den umströmten Bauteilen keine Ab­lösung der Strömung erfolgt und sich damit der Kraftstoff­film auch nicht in Form größerer Tröpfchen ablöst. Die erfindungsgemäße Kraft-Luft-Gemischbildungsvorrichtung mit dem Radialdiffusor vereint somit die baulichen Vorteile betreffend die geringere Baulänge bei Verwendung eines Radialdiffusors mit den strömungstechnischen Vorteilen, aber baulichen Nachteilen eines geraden Diffusors.It is fundamental to the present invention that the nozzle body is curved outwards from the narrowest cross section of the nozzle with minimal radii of curvature, if possible, and that the curvature directed towards the throttle body is curved so far with minimal radii of curvature in the direction of the throttle body that the diffuser function is caused by the Cooperation between the corresponding area of the nozzle body and the curved wall directed towards the throttle body is ensured. The minimal radii of curvature of the area of the nozzle body and the wall ensure that there is no separation of the flow on the components flowing around and that the fuel film does not become detached in the form of larger droplets. The power-air mixture formation device according to the invention with the radial diffuser thus combines the structural advantages with regard to the shorter overall length when using a radial diffuser with the aerodynamic advantages, but structural disadvantages of a straight diffuser.

Gemäß einer besonderen Ausführungsform der Erfindung ist vorgesehen, daß der nach außen gekrümmte Bereich des Düsen­körpers mit einer Heizeinrichtung versehen ist. Die Auf­heizung sollte dabei möglichst nahe nach der Stelle der Kraftstoffzufuhr, somit dem in die Düse mündenden Spalt beginnen. Sie kann beispielsweise elektrisch und/oder - vorzugsweise - durch ein vom Motor aufgeheiztes Medium, insbesondere Kühlwasser, Schmieröl, Abgas erfolgen. Durch die Aufheizung im gekrümmten Bereich des Düsenkörpers, wo­bei die Heizeinrichtung zweckmäßig in unmittelbarer Nähe zur Innenwandung des betreffenden Abschnittes des Düsen­körpers in diesem angeordnet sein sollte, dampft der an der Innenwandung befindliche Kraftstoffilm fast vollständig ab, um so mehr, je stärker die Wandung des Düsenkörpers aufgeheizt wird. Die Heizmöglichkeit verbessert damit noch­mals die durch die besondere Auslegung des Radialdiffusors erzielten strömungstechnischen Vorteile. Es wird darüber hinaus als zweckmäßig angesehen, auch das die rotations­ symmetrische Wandung aufweisende Bauteil mit einer Heizein­richtung zu versehen. Auch die Beheizung dieses Bauteiles kann beispielsweise elektrisch und/oder durch ein vom Mo­tor aufgeheiztes Medium erfolgen.According to a special embodiment of the invention it is provided that the outwardly curved region of the nozzle body is provided with a heating device. The heating should begin as close as possible to the point at which the fuel is supplied, thus the gap that opens into the nozzle. It can be done, for example, electrically and / or - preferably - by a medium heated by the engine, in particular cooling water, lubricating oil, exhaust gas. As a result of the heating in the curved region of the nozzle body, the heating device expediently being arranged in the immediate vicinity of the inner wall of the relevant section of the nozzle body, the fuel film on the inner wall evaporates almost completely, the more the stronger the wall of the nozzle body is heated. The heating option thus further improves the aerodynamic advantages achieved by the special design of the radial diffuser. It is also considered appropriate, including the rotations to provide a symmetrical wall-mounted component with a heating device. This component can also be heated, for example, electrically and / or by a medium heated by the motor.

Weitere Merkmale der Erfindung sind in der Figurenbeschrei­bung dargestellt, wobei bemerkt wird, daß alle Einzelmerk­male und alle Kombinationen von Einzelmerkmalen erfindungs­wesentlich sind.Further features of the invention are shown in the description of the figures, it being noted that all the individual features and all combinations of individual features are essential to the invention.

In der einzigen Figur ist eine Ausführungsform der erfin­dungsgemäßen Kraftstoff-Luft-Gemischbildungsvorrichtung in einem Längsschnitt verdeutlicht, ohne hierauf beschränkt zu sein.In the single figure, an embodiment of the fuel-air mixture formation device according to the invention is illustrated in a longitudinal section, without being limited to this.

Mit der Bezugsziffer 1 ist eine gedachte Längsachse der Kraftstoff-Luft-Gemischbildungsvorrichtung bezeichnet, um die Teile dieser Gemischbildungsvorrichtung symmetrisch ausgebildet sind. Im wesentlichen rotationssymmetrisch ge­formt ist ein Düsenkörper 2 mit seiner inneren Wandung 3. Der von der inneren Wandung begrenzte Innenraum in dem Düsenkörper verjüngt sich in seinem oberen Bereich 4 nach unten stetig bis zu einer Stelle bei dem Bezugszeichen 5 des engsten lichten Querschnitts. An diesen schließt sich nach unten ein Radialdiffusor 6 an. Oben wird die Kraftstoff-­Luft-Gemischbildungsvorrichtung über ein nicht dargestelltes Luftfilter mit Luft beaufschlagt. Der Hauptluftmassenstrom strömt also in Pfeilrichtung L von oben nach unten und dann im rechten Winkel hierzu radial nach außen.Reference number 1 denotes an imaginary longitudinal axis of the fuel-air mixture formation device, around which parts of this mixture formation device are formed symmetrically. A nozzle body 2 with its inner wall 3 is essentially rotationally symmetrical. The interior space delimited by the inner wall in the nozzle body tapers downwards continuously in its upper region 4 to a point at reference number 5 of the narrowest clear cross-section. A radial diffuser 6 adjoins this at the bottom. Air is applied to the fuel-air mixture formation device at the top via an air filter (not shown). The main air mass flow therefore flows in the direction of arrow L from top to bottom and then at right angles to it radially outwards.

Zur Regelung des Hauptluftmassenstroms dient in Verbindung mit dem Düsenkörper ein ebenfalls rotationssymmetrisch um die Längsachse geformter Drosselkörper 8, der dazu in Rich­tung der Längsachse gemäß Doppelpfeil A einstellbar ist. Ein oberer Teil des Drosselkörpers erweitert sich von oben stetig und mündet in einen wesentlichen unteren Teil des Drosselkörpers, der sich von oben nach unten stetig verjüngt.To regulate the main air mass flow, a throttle body 8, which is likewise rotationally symmetrical about the longitudinal axis and is adjustable in the direction of the longitudinal axis according to double arrow A, is used in connection with the nozzle body. An upper part of the throttle body widens continuously from above and opens into a substantial lower part of the throttle body, which tapers continuously from top to bottom.

Der Durchlaß für den Luftmassenstrom zwischen dem Düsen­körper und dem Drosselkörper wird also um so mehr verengt, je weiter der Drosselkörper nach unten verschoben ist. Der Düsenkörper bildet zusammen mit dem Drosselkörper eine konvergent-divergente Düse.The passage for the air mass flow between the nozzle body and the throttle body is thus narrowed the further the throttle body is moved downward. The nozzle body forms a convergent-divergent nozzle together with the throttle body.

Zur Kraftstoffzufuhr in den Innenraum des Düsenkörpers ist dessen Wandung mit einer Kraftstoffzuleitungsbohrung 9 versehen, die über einen Kraftstoffringkanal 10 in einen Kraftstoffspalt 11 übergeht. Der Kraftstoffspalt liegt in einer Querschnittsebene im Bereich des engsten lichten Querschnittes und weist eine zu dem Innenraum des Düsenkörpers gerichtete Spaltöffnung 12 auf. Die Spalt­öffnung erstreckt sich also ebenso wie der umlaufende Kraftstoffspalt über 360°. Zur gleichmäßigen Verteilung des in den Düsenkörper über dessen Umfang eintretenden Kraftstoffstroms ist der Kraftstoffringkanal mit einem verhältnismäßig kleinen Strömungswiderstand ausgebildet, während der Kraftstoffspalt einen verhältnismäßig hohen Strömungswiderstand aufweist. In den Kraftstoffspalt wird außer Kraftstoff Luft unter höherem Druck annähernd unter Umgebungsluftdruck eingeleitet. Hierzu steht der Kraftstoff­spalt über einen Luft-Ringkanal 13 sowie Bohrungen 14 mit einem nicht näher gezeigten Innenraumabschnitt in dem Düsenkörper in Verbindung, in dem praktisch der Luftdruck der Umgebung herrscht, während in der Spaltöffnung 12 ein Luftdruck von etwa der Hälfte des Umgebungsdruckes herrscht, und die Luft an dieser Stelle mit Schallgeschwindigkeit strömt. Durch die Luftzuführung wird eine Dampfblasenbil­dung vermieden, da hier der Kraftstoff praktisch unter Atmosphärendruck steht. Die Luftzuführung und der sich an sie anschließende Kraftstoffspalt sind so bemessen, daß in ihnen etwas Luft mit dem Kraftstoff vermischt wird. Dadurch erhält der aus der Spaltöffnung 12 austretende Kraftstoff eine höhere Geschwindigkeit als ohne eine sol­che Luftbeimischung. Im Ergebnis erfolgt damit die Kraft­stoffzuführung zu der Verbrennungsluft bzw. dem Luftmassen­ strom gleichmäßig über den Umfang des Düsenkörpers und filmartig. Dennoch ist im Betrieb der beschriebenen Kraft­stoff-Luft-Gemischbildungsvorrichtung festzustellen, daß im Kraftstoffspalt 11 strömender Kraftstoff an dessen Wandungen infolge Adhäsion haftet und auch nach dem Über­tritt in den Diffusor in einem mehr oder weniger starken Film an dessen innerer Wandung haften bleibt.To supply fuel to the interior of the nozzle body, the wall of the nozzle body is provided with a fuel feed bore 9 which merges into a fuel gap 11 via a fuel ring channel 10. The fuel gap lies in a cross-sectional plane in the area of the narrowest clear cross-section and has a gap opening 12 directed towards the interior of the nozzle body. The gap opening, like the circumferential fuel gap, thus extends over 360 °. For the uniform distribution of the fuel flow entering the nozzle body over its circumference, the fuel ring channel is designed with a relatively small flow resistance, while the fuel gap has a relatively high flow resistance. In addition to fuel, air is introduced into the fuel gap under higher pressure, approximately under ambient air pressure. For this purpose, the fuel gap is connected via an air ring duct 13 and bores 14 to an interior section, not shown in more detail, in the nozzle body, in which practically the air pressure in the environment prevails, while in the gap opening 12 there is an air pressure of approximately half the ambient pressure, and the air at this point flows at the speed of sound. The air supply prevents the formation of vapor bubbles, since the fuel is practically under atmospheric pressure. The air supply and the fuel gap adjoining it are dimensioned such that some air is mixed with the fuel in them. This gives the fuel emerging from the gap opening 12 a higher speed than without such an admixture of air. As a result, the fuel is supplied to the combustion air or the air masses stream evenly over the circumference of the nozzle body and film-like. Nevertheless, in operation of the fuel-air mixture formation device described it can be ascertained that fuel flowing in the fuel gap 11 adheres to its walls as a result of adhesion and also adheres to its inner wall in a more or less strong film after it has entered the diffuser.

Um sicherzustellen, daß der Kraftstoffilm sich nicht von der Wandung 3 des Radialdiffusors ablöst, weist dieser eine besondere Ausbildung auf. So ist der Radialdiffusor durch einen in Strömungsrichtung des Gemisches nach außen gekrümmten Bereich des Düsenkörpers und eine dem Drossel­körper gegenüberliegende, zur Rotationsachse des Drossel­körpers rotationssymmetrische Wandung 15 gebildet, die eine auf den Drosselkörper gerichtete Wölbung 16 aufweist. Die Wandung 15 ist Bestandteil eines Bauteiles 17, das mit einem Saugrohr 7 des Verbrennungsmotors eine Baueinheit 18 bildet. Der Figur ist konkret zu entnehmen, daß der Düsen­körper mit dem Drosselkörper stromabwärts der Spaltöffnung 12 den divergenten Bereich der Düse bildet, die in den Radialdiffusor mündet, dessen Durchtrittsquerschnitt sich stetig bis zu dessen radialer Austrittsöffnung 19 verjüngt, die den Übergang zum Saugrohr 7 darstellt. Die erforder­liche Auswölbung der Wandung 15 in Richtung des Drossel­körpers ist dabei von den strömungstechnischen Gegebenen­heiten abhängig.In order to ensure that the fuel film does not detach from the wall 3 of the radial diffuser, it has a special design. The radial diffuser is thus formed by an area of the nozzle body which is curved outward in the flow direction of the mixture and by a wall 15 which is opposite the throttle body and is rotationally symmetrical with respect to the axis of rotation of the throttle body and has a curvature 16 directed towards the throttle body. The wall 15 is part of a component 17, which forms a structural unit 18 with a suction pipe 7 of the internal combustion engine. The figure shows in concrete terms that the nozzle body with the throttle body downstream of the gap opening 12 forms the divergent area of the nozzle, which opens into the radial diffuser, the passage cross section of which tapers continuously up to its radial outlet opening 19, which represents the transition to the suction pipe 7. The required curvature of the wall 15 in the direction of the throttle body is dependent on the fluidic conditions.

Die erfindungsgemäße Wirkungsweise des Radialdiffusors, die ein Ablösen der Luft von der Wandung 3 ver­hindern soll, wird dadurch unterstützt, daß bei der gezeig­ten Vorrichtung sowohl der nach außen gekrümmte Bereich des Düsenkörpers als auch das die Wandung 15 aufweisende Bauteil mit einer Heizeinrichtung 20 bzw. 21 versehen sind. Die Heizeinrichtung 20 weist einen im Düsenkörper im Be­reich dessen innerer Wandung angeordneten Heizkanal 22 auf, der ringförmig ausgebildet ist und damit die innere Wandung des Diffusors vollständig umgibt. Der Heizkanal ist mit einem Motorkühlwassereintritt 23 und einem gegenüberlie­genden Motorkühlwasseraustritt 24 versehen, die Aufheizung des Diffusors erfolgt somit durch das heiße Motorkühlwasser. Damit der radial zum Diffusor zugeführte Kraftstoff durch das Motorkühlwasser nicht aufgeheizt wird - was in der weiteren Folge zur Dampfblasenbildung führen könnte - ist durch konstruktive Ausbildung der Kraftstoff-Luft-Gemisch­bildungsvorrichtung der Wärmewiderstand zwischen dem Motor­kühlwasser und den kraftstofführenden Kanälen möglichst groß gehalten. So weist der Düsenkörper im Bereich des Kraftstoffspaltes und der Spaltöffnung eine geringe Wand­stärke und einen luftführenden Hohlraum 25 auf, die einer unerwünschten Aufwärmung des Kraftstoffes entgegenwirken, was einen hohen Aufheizungswirkungsgrad des Düsenkörpers im Bereich des Diffusors gewährleistet. Die Aufheizung be­wirkt ein fast vollständiges Abdampfen des an der Wandung des Diffusors befindlichen Kraftstoffilmes. Zur weiteren Vermindung des Kraftstoffilmes auch an der Wandung 15 durchsetzt das zugehörige Bauteil 17 ein Heizkanal 26 mit Motorkühlwassereintritt 27 und Motorkühlwasseraustritt 28.The operation of the radial diffuser according to the invention, which is intended to prevent the air from detaching from the wall 3, is supported in that, in the device shown, both the outwardly curved region of the nozzle body and the component having the wall 15 with a heating device 20 or 21 are provided. The heating device 20 has a heating channel 22 which is arranged in the nozzle body in the region of its inner wall and is of annular design and thus the inner wall completely surrounds the diffuser. The heating duct is provided with an engine cooling water inlet 23 and an opposite engine cooling water outlet 24, the diffuser is thus heated by the hot engine cooling water. So that the fuel supplied radially to the diffuser is not heated by the engine cooling water - which could subsequently lead to the formation of vapor bubbles - the thermal resistance between the engine cooling water and the fuel-carrying ducts is kept as large as possible by constructive design of the fuel-air mixture formation device. Thus, the nozzle body in the area of the fuel gap and the gap opening has a small wall thickness and an air-guiding cavity 25 which counteract undesired heating of the fuel, which ensures a high heating efficiency of the nozzle body in the area of the diffuser. The heating causes the fuel film on the wall of the diffuser to evaporate almost completely. To further reduce the fuel film on the wall 15, the associated component 17 passes through a heating channel 26 with engine cooling water inlet 27 and engine cooling water outlet 28.

Claims (4)

1. Kraftstoff-Luft-Gemischbildungsvorrichtung für Verbren­nungsmotoren, mit einem rotationssymmetrischen Düsen­körper, der zusammen mit einem in ihm verschiebbaren rotationssymmetrischen Drosselkörper eine konvergent-­divergente Düse bildet, die in einen Radialdiffusor mündet, und ein in der Nähe des engsten Querschnittes der Düse um diese umlaufender und in diese mündender Spalt vorgesehen ist, in den mindestens eine Kraftstoff­zuleitung mündet,
dadurch gekennzeichnet, daß der Radialdiffusor (6) durch einen in Strömungsrichtung des Gemisches nach außen gekrümmten Bereich des Düsenkörpers und eine dem Dros­selkörper (8) gegenüberliegende, zur Rotationsachse (1) des Drosselkörpers (8) rotationssymmetrische Wan­dung (15) eines eine Baueinheit (18) mit einem Saug­rohr (7) des Verbrennungsmotors bildenden Bauteiles (17) gebildet ist, wobei die Wandung (15) eine auf den Drosselkörper (8) gerichtete Wölbung (16) aufweist.1. A fuel-air mixture formation device for internal combustion engines, with a rotationally symmetrical nozzle body which, together with a rotationally symmetrical throttle body displaceable in it, forms a convergent-divergent nozzle which opens into a radial diffuser, and a circumferential one in the vicinity of the narrowest cross section of the nozzle and is provided in this opening gap, into which at least one fuel supply line opens,
characterized in that the radial diffuser (6) has a unit (18) through a region of the nozzle body which is curved outward in the direction of flow of the mixture and a wall (15) which is opposite the throttle body (8) and is rotationally symmetrical to the axis of rotation (1) of the throttle body (8) ) is formed with a suction pipe (7) of the component (17) forming the internal combustion engine, the wall (15) having a curvature (16) directed towards the throttle body (8). 2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der nach außen gekrümmte Bereich des Düsenkörpers (2) mit einer Heizeinrichtung (20) versehen ist.2. Device according to claim 1, characterized in that the outwardly curved region of the nozzle body (2) is provided with a heating device (20). 3. Vorrichtung nach Anspruch 1 oder 2, dadurch gekenn­zeichnet, daß das die rotationssymmetrische Wandung (15) aufweisende Bauteil (17) mit einer Heizeinrichtung (21) versehen ist.3. Device according to claim 1 or 2, characterized in that the component (17) having the rotationally symmetrical wall (15) is provided with a heating device (21). 4. Vorrichtung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Aufheizung mittels der Heizein­richtung bzw. Heizeinrichtungen (20, 21) elektrisch und/oder durch ein vom Verbrennungsmotor aufgeheiztes Medium, insbesondere Kühlwasser, Schmieröl, Abgas erfolgt.4. Device according to one of claims 1 to 3, characterized in that the heating by means of the heating device or heating devices (20, 21) is carried out electrically and / or by a medium heated by the internal combustion engine, in particular cooling water, lubricating oil, exhaust gas.
EP89118677A 1989-05-31 1989-10-07 Air-fuel mixture preparing device for internal combustion engine Withdrawn EP0400210A1 (en)

Applications Claiming Priority (2)

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DE3917681A DE3917681A1 (en) 1989-05-31 1989-05-31 FUEL-AIR MIXTURE FOR COMBUSTION ENGINES
DE3917681 1989-05-31

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Publication number Priority date Publication date Assignee Title
US5245977A (en) * 1991-07-03 1993-09-21 Tecogen, Inc. Flow proportioning mixer for gaseous fuel and air and internal combustion engine gas fuel mixer system
DE9318951U1 (en) * 1993-11-30 1994-02-17 Kabisch Herbert Device for the production of mixtures of gases and liquids, in particular of air and fuels

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US4008699A (en) * 1976-04-05 1977-02-22 Ford Motor Company Extended throttle bore multi-stage carburetor
EP0084639A2 (en) * 1982-01-27 1983-08-03 Keiun Kodo Variable venturi carburetor
DE3643882A1 (en) * 1986-12-22 1988-06-30 Vdo Schindling FUEL-AIR MIX TREATMENT DEVICE FOR COMBUSTION ENGINES

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DE2058992A1 (en) * 1970-12-01 1972-06-08 Daimler Benz Ag Axially movable throttle element arranged in an intake duct of a mixture-compressing internal combustion engine

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US4008699A (en) * 1976-04-05 1977-02-22 Ford Motor Company Extended throttle bore multi-stage carburetor
EP0084639A2 (en) * 1982-01-27 1983-08-03 Keiun Kodo Variable venturi carburetor
DE3643882A1 (en) * 1986-12-22 1988-06-30 Vdo Schindling FUEL-AIR MIX TREATMENT DEVICE FOR COMBUSTION ENGINES

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JPH0396648A (en) 1991-04-22
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