DK2623863T3

DK2623863T3 - Fuel gas-air mixing device

Info

Publication number: DK2623863T3
Application number: DK13153084T
Authority: DK
Inventors: Jochen Wriske; Matthias Wodtke; Nicole Schmidt
Original assignee: Vaillant Gmbh
Priority date: 2012-01-31
Filing date: 2013-01-29
Publication date: 2015-03-02
Also published as: DE102012003501A1; EP2623863B1; EP2623863A3; ES2528968T3; EP2623863A2

Description

Den foreliggende opfindelse angår en brændgas-luft blandeindretning for et varmeapparat. Sådanne blandeindretninger baserer sig på en blandedyse, sædvanligvis en ven-turidyse, hvor der ved hjælp af en blæser transporteres luft gennem dysen. I området ved venturidysens snævre tværsnit bliver der ortogonalt tilført brændgas. Via en drøv-leventil i gasvejen bliver den for en ren forbrænding nødvendige brændgasmængde i forhold til luftmængden indstillet. Venturidysen sikrer, at der i et bestemt område af luftmassestrømmen inden for snævre tolerancer sker konstantholdelse af brændgas-luft-forholdet.The present invention relates to a fuel-air mixing device for a heater. Such mixing devices are based on a mixing nozzle, usually a vent nozzle, where air is transported through the nozzle by means of a blower. In the area at the narrow cross section of the venturi nozzle is supplied orthogonally. Via a throttle valve in the gas path, the amount of fuel needed for a clean combustion is adjusted in relation to the amount of air. The venturi nozzle ensures that within a certain range of the air mass flow within narrow tolerances, the fuel-air ratio is maintained.

Under en grænseværdi, hvor strømningshastigheden bliver for lille, er dette imidlertid ikke længere muligt. For et varmeapparat er det imidlertid fordelagtigt, når det ved en nominel belastning, henholdsvis delbelastning råder over et stort forhold mellem maksimal og minimal ydelse. Disse systemer er imidlertid begrænsede i den henseende, at trykfaldet, som her indstiller sig over venturidysen fra delbelastning til nominel belastning, forholder sig kvadratisk, og at hele systemet ved nominel belastning begrænses af den maksimalt mulige trykforøgelse ved hjælp af den anvendte blæser.However, below a limit value where the flow rate becomes too small, this is no longer possible. However, for a heater it is advantageous when at a nominal load or partial load, respectively, there is a large ratio between maximum and minimum output. However, these systems are limited in that the pressure drop, which here sets itself over the venturi nozzle from partial load to nominal load, is quadratic and that the whole system at nominal load is limited by the maximum possible pressure increase by means of the fan used.

Af denne grund kendes der ifølge den kendte teknik forskellige løsninger, som også i delbelastningsområdet med små ydelser har et tilstrækkelig smalt tolereret brændgas-luft-forhold.For this reason, various solutions are known according to the prior art, which also have a sufficiently narrow tolerated fuel-air ratio in the low-load part area with low performance.

Patentansøgningen DE 196 35 974 Al beskriver en brændgas-luft-blandeindretning til gasvarmeapparater, hvor åbningstværsnittet til brændkammeret ved hjælp af en tyngdekraftbelastet svingklap alt efter volumenstrømmen bliver tilpasset.The patent application DE 196 35 974 A1 discloses a gas-air mixer for gas heaters, in which the opening cross-section of the combustion chamber is adjusted according to the volume flow by means of a gravity-loaded swing valve.

Patentet EP 1 183 483 Bl beskriver en blandeindretning til brændgas og forbrændingsluft med to parallelle luftdyser i form af venturidyser. En eller alternativt begge luftdyser kan spærres ved hjælp af lukkeindretninger. Lukkeindretningerne er udformet som klapper, hvorved klapperne ved hjælp af fjedre holdes mod strømningsretningen. Fjederkonstanten bestemmer således lukkekarakteristikken.The patent EP 1 183 483 B1 describes a combustion device for combustion gas and combustion air with two parallel air nozzles in the form of venturi nozzles. One or alternatively both air nozzles can be blocked by means of closing devices. The closing devices are designed as flaps, whereby the flaps are held against the flow direction by means of springs. Thus, the spring constant determines the closing characteristic.

Ifølge patentansøgningen WO 2012/007823 kendes en blandeindretning, hvor der ligeledes ved hjælp af en klap i luftvejen sker formindskelse af strømningstværsnittet ved delbelastning. En anden klap, som påvirkes af lufttrykket, lukker for brændgasve-jen.According to patent application WO 2012/007823, a mixing device is known in which a reduction of the flow cross-section by partial loading is also effected by means of a flap in the airway. Another flap, which is influenced by the air pressure, closes the fuel path.

Patentskriftet DE 41 37 573 Cl offentliggør en blandeindretning med et i strømningsmæssig henseende fordelagtigt fortrængningslegeme inden i en venturidyse. Med henblik på at kunne indstille blandeindretningen til forskellige gaskvaliteter kan fortrængningslegemets position inden i venturidysen ved hjælp af en spindel indstilles i luftstrømningsretningen. Gastilførslen kan ligeledes drøvles.The patent specification DE 41 37 573 Cl discloses a mixing device with a displaceable body advantageous within a venturi nozzle. In order to be able to adjust the mixer to different gas grades, the position of the displacement body within the venturi nozzle can be adjusted in the air flow direction by means of a spindle. The gas supply can also be swirled.

Patentskriftet DE 103 24 706 B3 beskriver en blandeindretning, hvor et kegleformet fortrængningslegeme ved hjælp af en servomotor kan bevæges ind i en luftdyse. Ser-vomotoren for keglen arbejder i afhængighed af et signal fra en sensor, som detekterer ændringer i gaskvaliteten, lufttrykket og/eller forbrændingsluftens temperatur.The patent specification DE 103 24 706 B3 discloses a mixing device in which a cone-shaped displacement body can be moved into an air nozzle by means of a servomotor. The cone servomotor operates in response to a signal from a sensor which detects changes in gas quality, air pressure and / or combustion air temperature.

De fra den kendte teknik kendte blandeindretninger er imidlertid ufordelagtige ved, at den ved geometrien bestemte sammenhæng mellem luftvolumen og tryktab ved smalle tværsnit kun kan ændres springvist, men ikke kontinuerligt. Også i tilfælde af jævn åbning af afspærringsindretningen i en af luftdyseme forbliver det for gastilførslen bestemmende tryksignal udelukkende afhængigt af den foreliggende, uforanderlige dysegeometri. Tilvejebringelsen af tyngdekraft- eller fjederbelastede afspærringsindretninger i strømningsvejen bevirker ydermere reguleringstolerancer, som dels skyldes ugunstige strømningsforhold og dels tryktabets følsomhed over for komponenttolerancer.The mixing devices known in the prior art, however, are disadvantageous in that the relationship determined by the geometry between air volume and pressure loss at narrow cross sections can only be changed in a jumpy manner but not continuously. Also, in the case of smooth opening of the shut-off device in one of the air nozzles, the pressure signal for the gas supply remains solely dependent on the invariable nozzle geometry available. The provision of gravity or spring-loaded shut-off devices in the flow path further causes regulation tolerances, which are partly due to unfavorable flow conditions and partly the pressure sensitivity to component tolerances.

Den til grund for opfindelsen liggende opgave er derfor at anvise en blandeindretning, hvis blandingsforhold mellem brændegas og luft ved lille delbelastning har endnu mindre tolerance end ved den kendte teknik. Det tilstræbes, at der ved en ifølge ven-turiprincippet drevet gas-luft relation ved delbelastningen frembringes et tilstrækkelig stort tryksignal med henblik på at sikre en nøjagtig regulering af gasarmaturet.The object of the invention is therefore to provide a mixing device whose mixing ratio between fuel gas and air at a small partial load has even less tolerance than in the prior art. It is sought that in a gas-air relationship driven by the venturi principle at the partial load, a sufficiently large pressure signal is produced in order to ensure an accurate regulation of the gas luminaire.

Denne opgave løses ifølge opfindelsen ved, at der dels sker en sådan udformning af lufttilførslens strømning svej, at denne er dannet forstyrrelsesfrit og uden kanter eller plader, på hvilke der opstår hvirveldannelse. Dels er der tilvejebragt en kontinuerlig ændring af tværsnittet i afhængighed af luftmassestrømmen. Dette sker dels ved hjælp af en strømningsmæssigt fordelagtig udformning af drøvlingsmidlet, dels på grund af muligheden for, at drøvlingsmidlet og luftkanalen kontinuerligt forskydes i forhold til hinanden. I denne forbindelse sker forskydningen i en retning parallelt med luftstrømningsretningen, således at denne forskydning, således at denne forskydning på simpel måde kan udvirkes ved hjælp af lufttrykforskelle mellem position foran og bagved blandeindretningen. Blandeindretningen er udformet således, at den strømmende luft og dermed det virkende lufttryk forskyder sammensætningen af luftkanalen og/eller droslingsmidlet mod et elastisk element i luftstrømningsretningen. Ved hjælp af det elastiske element fastlægges en kraft-vej-sammenhæng. Udformningen af luftkanalen, drøvlingsmidlet og det elastiske element tilpasses herved således, at der ved tiltagende luftmassestrøm sker en kontinuerlig forøgelse af tværsnitsarealet, som dannes mellem drøvlingsmiddel og luftkanal. Derved sikres det, at der i et bredt område for luftmassestrømmen med henblik på pålidelig funktion af blandeindretningen foreligger den nødvendige, minimale strømningshastighed, og der således foreligger et tilstrækkelig højt undertryk af hensyn til blandeindretningens funktion.This task is solved according to the invention in that part of the design of the flow of the air supply is made so that it is disturbed free and without edges or plates on which vertebral formation occurs. In part, a continuous change of the cross section is provided depending on the air mass flow. This is done partly by means of a flow advantageous design of the throttle means and partly because of the possibility that the throttle means and the air duct are continuously displaced relative to each other. In this connection, the displacement occurs in a direction parallel to the air flow direction, such that this displacement, so that this displacement can be simply effected by means of air pressure differences between the position in front and behind the mixing device. The mixing device is designed so that the flowing air and thus the operating air pressure displaces the composition of the air duct and / or the throttling means against an elastic element in the air flow direction. By means of the elastic element, a force-path relationship is established. The design of the air duct, the throttle means and the resilient element is hereby adapted such that, with increasing air mass flow, a continuous increase of the cross-sectional area formed between the throttle agent and the air duct occurs. This ensures that in a wide area of the air mass flow for the reliable operation of the mixing device, the necessary minimum flow rate is present, and thus a sufficiently high negative pressure exists for the function of the mixing device.

Ganske vist er det fra DE 198 06 315 Cl kendt, at der i en brændgas-luft-blandeindretning tilvejebringes et fortrængningslegeme, som ved hjælp af luftstrømningen kan forskydes i aksial retning. Denne udførelsesform stiller en meget ydedygtig dyse i udsigt, men der er ingen henvisninger til, at denne dyse på særligt egnet måde ved delbelastning sikrer nøjagtige blandingsforhold mellem brændgas og luft. Således er ifølge opfindelsen det forskydelige drøvlingsmiddel eller den forskydelige luftkanal i modsætning til den kendte teknik på en sådan måde sammenkoblet med en separat ventil til brændgas, at denne ventil samtidig med forskydningen af drøvlingsmidlet eller luftkanalen, hvorved luftkanalen åbnes, kontinuerligt og proportionalt med tværsnitsændringen af luftkanalen, bliver åbnet. Derved sikres det, at blandeindretningen i hvert driftspunkt gives luft/brændgas-forholdet en ønsket værdi. I en udførelsesform for opfindelsen tilvejebringes den i strømningsmæssig henseende fordelagtige udformning ved hjælp af et fordelagtigt længde/diameter-forhold. Herved skal begrebet diameter ikke være indskrænket til cirkulære tværsnit, men snarere kunne anvendes til enhver tværsnitsform.It is known from DE 198 06 315 C1 that a displacement body is provided in a fuel-air mixing device which can be displaced in the axial direction by means of the air flow. This embodiment provides a very high-performance nozzle, but there are no indications that this nozzle, in a particularly suitable way, ensures accurate mixing ratios of fuel and air. According to the invention, in contrast to the prior art, the displaceable turbine or displaceable air duct is interconnected in such a way with a separate valve for fuel gas that this valve simultaneously with the displacement of the throttle or air duct, thereby opening the air duct, continuously and proportionally with the the air duct, being opened. This ensures that the mixing device at each operating point is given the desired air / fuel ratio. In one embodiment of the invention, the advantageous design in terms of flow is provided by an advantageous length / diameter ratio. In this way, the concept of diameter should not be limited to circular cross sections, but rather be applicable to any cross sectional shape.

Ifølge en fordelagtig variant af udførelsesformen udviser drøvlingsmidlet kontinuerlige tværsnitsovergange. Derved muliggøres en uforstyrret strømning langs drøvlingsmidlet.According to an advantageous variant of the embodiment, the throttling means exhibits continuous cross-sectional transitions. This allows an undisturbed flow along the throttle means.

Det elastiske element er med fordel en fjeder.The elastic member is advantageously a spring.

Ifølge en variant af opfindelsen er luftkanalen stationær, og drøvlingsmidlet er udført som forskydeligt.According to a variant of the invention, the air duct is stationary and the throttling means is designed as slidable.

Ved en foretrukket udførelsesform er luftkanalen stationær, og drøvlingsmidlet er udført som forskydeligt.In a preferred embodiment, the air duct is stationary and the throttle means is slidable.

Ifølge en foretrukket udførelsesform for denne variant af opfindelsen er drøvlingsmidlet forbundet til en fjederbelastet arm, der er så lang, at drøvlingsmidlet kan bevæges langs en med tilnærmelse retlinjet stedkurve parallelt med luftstrømningsretningen.According to a preferred embodiment of this variant of the invention, the throttle means is connected to a spring loaded arm so long that the throttle means can be moved along an approximately rectilinear place curve parallel to the direction of air flow.

Ved en alternativ variant af opfindelsen er drøvlingsmidlet derimod udført som stationært, og luftkanalen som forskydelig. Med fordel føres luftkanalen lineært forskydeligt mod en fjeder.In an alternative variant of the invention, on the other hand, the throttling means is designed as stationary and the air duct as slidable. Advantageously, the air duct is linearly displaceable against a spring.

Opfindelsen bliver nu forklaret nærmere ved hjælp af tegningens figurer, hvor:The invention will now be explained in more detail with the aid of the drawings in which:

Fig. 1 viser et snitbillede af en blandeindretning ifølge opfindelsen;FIG. 1 is a sectional view of a mixing device according to the invention;

Fig. 2 et snitbillede af en udførelsesvariant af en blandeindretning ifølge opfindelsen.FIG. 2 is a sectional view of an embodiment of a mixing device according to the invention.

Fig. 1 viser en betegnelse af en blandeindretning ifølge opfindelsen. Fra en på højre side anbragt, ikke her vist, blæser transporteres der luft gennem venturidysen. Ventu-ridysen dannes af luftkanalen 2 og det deri indeholdte drøvlingsmiddel 3. Set fra venstre sker der en kontinuerlig formindskelse af det frie tværsnitsareal for luftstrømningen indtil en tværsnitsareal-indsnævring 4, hvorefter tværsnitsarealet igen udvider sig. I området ved tværsnitsareal-indsnævringen er der tilvejebragt en tilførsel 5 for brændgas. På grund af den højere strømningshastighed i tværsnits-indsnævringen dannes der et undertryk, således at der gennem tilførslen 5 sker transport af brændgas ind i luftvejen, og som blander sig med luften. Ved hjælp af omdrejningstallet for den her ikke viste blæser kan mængden af gas-luft-blandingen ændres. Herved forbliver blandingsforholdet mellem brændgas og luft konstant i et bestemt område. Sker der en yderligere formindskelse af omdrejningstallet for blæseren og dermed af massestrømmen for luften, er det ikke længere sikret, at blandingsforholdet forbliver konstant. Af denne grund er venturidysen 1 udført således, at luftkanalen 2 og drøvlings-midlet 3 på grund af trykforholdene, som indstiller sig på grund af luftstrømningen, på en sådan måde kan forskydes i forhold til hinanden, at det frie tværsnitsareal mellem luftkanal 2 og droslingsmiddel 3 ved høje strømningshastigheder forøges, henholdsvis ved lave strømningshastigheder formindskes. Dette kan enten ske kontinuerligt over hele blæserens modulationsområde, kun kontinuerligt i det nedre dellastområde, men i et bestemt driftspunkt binært på den måde, at, ved over- eller underskridning af dette driftspunkt, enten et stort eller et lille tværsnitsareal mellem luftkanal 2 og drøvlings-middel forbliver frit. Ligeledes kan der være tilvejebragt en friktionsbetinget hystere-se, som forhindrer flagrende funktion. På grund af den høje lufthastighed bliver luftkanalen 2 skubbet til højre mod fjederen 7. Til dette formål bliver luftkanalen 2 til venstre ved hjælp af en føring 8, som ved hjælp af eger er forbundet til luftkanalen 2, ført mod det faststående drøvlingsmiddel 3. Tilførslen 5 er forbundet til en ventil 6, ved hjælp af hvilken massestrømmen for den tilførte brændgas kan ændres. Ventilen 6 er på en sådan måde forbundet til luftkanalen 2, at ventilen 6 åbnes, når luftkanalen 2 skubbes til højre. Derved bliver brænd-gasmængden tilpasset til det under ændring værende tværsnit af venturidysen. I fig. 2 er der vist en alternativ udførelsesform for blandeindretningen. Drøvlingsmid-let 3 har form som en rotationsellipsoide. Drøvlingsmidlet 3 er fastgjort således på en lang arm, at den bliver ført langs en cirkelbane med meget stor radius, som med tilnærmelse repræsenterer en ret linje. Ved tiltagende lufthastighed bliver drøvlingsmidlet trykket til højre mod fjederen. Løftearmen er forbundet til en ventil 6, ved hjælp af hvilken tilførslen af brændgas gennem tilførslen 5 kan doseres. Ved tiltagende lufthastighed bliver ventilen 6 mere og mere åbnet, således at tilførslen af brændgas tilpasses til luftmængden.FIG. 1 shows a designation of a mixing device according to the invention. From a blower located on the right side, not shown here, air is transported through the venturi nozzle. The vent nozzle is formed by the air duct 2 and the throttle means contained therein. From the left, a continuous decrease of the free cross-sectional area of the air flow occurs until a cross-sectional area narrowing 4, after which the cross-sectional area expands again. In the area of the cross-sectional area narrowing, a fuel supply 5 is provided. Due to the higher flow rate in the cross-sectional narrowing, a negative pressure is formed, so that through the feed 5 transport of fuel gas into the airway takes place and which mixes with the air. Using the speed of the fan not shown here, the amount of the gas-air mixture can be changed. In this way, the mixing ratio of fuel gas to air remains constant in a certain area. If there is a further decrease in the fan speed and hence the mass flow of the air, the mixing ratio is no longer ensured. For this reason, the venturi nozzle 1 is designed so that, due to the pressure conditions which adjust due to the air flow, the air duct 2 and the throttle means 3 can be displaced relative to each other such that the free cross-sectional area between air duct 2 and throttle means 3 at high flow rates are increased, respectively at low flow rates. This can be done either continuously over the entire fan modulation range, only continuously in the lower partial load range, but at a certain operating point binary in the way that, by over- or undercut this operating point, either a large or a small cross-sectional area between air duct 2 and turbine agent remains free. Likewise, a frictional hysteresis may be provided which prevents flagging operation. Due to the high air velocity, the air duct 2 is pushed to the right against the spring 7. For this purpose, the air duct 2 on the left is guided by the guide 8, which is connected to the air duct 2 by means of spokes, to the fixed throttle means 3. The supply 5 is connected to a valve 6 by means of which the mass flow of the supplied fuel gas can be changed. The valve 6 is connected in such a way to the air duct 2 that the valve 6 is opened when the air duct 2 is pushed to the right. Thereby, the amount of fuel gas is adjusted to the changing section of the venturi nozzle. In FIG. 2, an alternative embodiment of the mixing device is shown. The ruminant 3 is in the form of a rotary ellipsoid. The throttle means 3 is secured to a long arm so that it is guided along a circular path of very large radius, which approximates a straight line. At increasing air velocity, the throttle means is pressed to the right against the spring. The lifting arm is connected to a valve 6 by means of which the supply of fuel gas can be metered through the supply 5. With increasing air velocity, the valve 6 is opened more and more, so that the supply of fuel gas is adjusted to the amount of air.

Henvisningstal. 1 blandedyse 2 luftkanal 3 drøvlingsmiddel 4 tværsnitsindsnævring 5 tilførsel 6 ventil 7 elastisk element 8 føring.Numeral. 1 mixing nozzle 2 air duct 3 throttle means 4 cross-sectional constriction 5 supply 6 valve 7 elastic element 8 guide.

Claims

A mixing device for mixing fuel and air in a specific mixing ratio, comprising a mixing nozzle (1) containing an air duct (2) through which the air can be passed, comprising a supply (5) for fuel gas entering the mixing nozzle (1) ), and comprising a throttle means (3), whereby the throttle means (3) are designed to be flowably advantageous and disposed in such a manner as to form in the air duct 2 such that the cross section remaining between the air duct (2) and the throttle means (3) substantially continuous cross-sectional narrowing (4) into which the supply (5) enters and that the throttling means (3) and the air duct (2) can be displaced in such a way in the air flow direction relative to each other that the cross-sectional area in the area of the cross-sectional narrowing (4) increases the air mass flow continuously expands, whereby the displaceable throttle means (3) or the displaceable air duct (2) is coupled to a valve (6) for fuel gas that 1 is continuously opened as the displaceable throttle means (3) or the slidable air duct (2) move in a direction causing an increase of the cross-sectional area in the area of the cross-sectional constriction (4), characterized in that the air duct (2) and the throttle means (3) ) is designed such that the flowing air exerts a force on the air duct (2) and / or the throttle means (3), and such force acts against an elastic member (7) to displace the throttle means (3) and the air duct (2). relative to each other in the flow direction.

A mixing device according to claim 1, wherein the throttle means (3), viewed in the direction of the air flow, has a length / diameter ratio greater than 0.5, preferably greater than 1.

A mixing device according to claim 1 or 2, wherein the throttling means (3), viewed in the direction of the air flow, exhibit substantially continuous cross-sectional transitions.

A mixing device according to any one of claims 1 to 3, wherein the turbulent means, seen in the direction of the air flow, exhibits a substantially elliptical shape.

The mixing device of any one of claims 1 to 4, wherein the elastic member (7) is a spring.

A mixing device according to any one of claims 1 to 5, wherein the air duct (2) is designed as stationary and the throttling means (3) is designed as slidable.

The mixing device of claim 6, wherein the throttling means (3) is connected to a spring loaded arm.

A mixing device according to any one of claims 1 to 5, wherein the throttling means (3) is designed as stationary and the air duct is provided as slidable.

A mixing device according to claim 8, wherein the air duct (2) is designed as linearly displaceable against a spring.