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EP0160884B1 - Air to fuel-ratio controller for a heating source - Google Patents

Air to fuel-ratio controller for a heating source Download PDF

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Publication number
EP0160884B1
EP0160884B1 EP85104923A EP85104923A EP0160884B1 EP 0160884 B1 EP0160884 B1 EP 0160884B1 EP 85104923 A EP85104923 A EP 85104923A EP 85104923 A EP85104923 A EP 85104923A EP 0160884 B1 EP0160884 B1 EP 0160884B1
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EP
European Patent Office
Prior art keywords
temperature
exhaust gas
air
dew point
controller
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.)
Expired - Lifetime
Application number
EP85104923A
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German (de)
French (fr)
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EP0160884A3 (en
EP0160884A2 (en
Inventor
Joachim Plate
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Vaillant BV
Original Assignee
Vaillant Austria GmbH
Nv Vaillant Sa
Joh Vaillant GmbH and Co
Vaillant GmbH
Vaillant SARL
Vaillant Ltd
SCHONEWELLE BV
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Application filed by Vaillant Austria GmbH, Nv Vaillant Sa, Joh Vaillant GmbH and Co, Vaillant GmbH, Vaillant SARL, Vaillant Ltd, SCHONEWELLE BV filed Critical Vaillant Austria GmbH
Priority to AT85104923T priority Critical patent/ATE56084T1/en
Publication of EP0160884A2 publication Critical patent/EP0160884A2/en
Publication of EP0160884A3 publication Critical patent/EP0160884A3/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/02—Regulating fuel supply conjointly with air supply
    • F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/08—Measuring temperature
    • F23N2225/10—Measuring temperature stack temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2225/00—Measuring
    • F23N2225/26—Measuring humidity

Definitions

  • the present invention relates to a control device according to the preamble of the main claim.
  • Such a control device is known from EP-A-147 632 in accordance with Article 54 (3) EPO.
  • Control devices have also become known which use either the residual concentration of oxygen in the exhaust gas or the O Z content of this exhaust gas as the measurement variable. Due to the fact that any kind of continuously operating quantitative gas analysis has to be carried out, the control devices mentioned require a high level of measurement technology. The high costs of oxygen and carbon dioxide analysis have so far only justified the use of these measurement and control methods in large industrial furnace construction.
  • the present invention aims to establish a ratio control for the air-fuel ratio.
  • Small heat source in the range between 5 and 30 kW. With such a small heat source, the price for the control device must not exceed a certain small percentage in relation to the total device price, since otherwise the control device will not be accepted by the operator of the heat source.
  • the invention is based on the knowledge that there is a connection between the air ratio and the dew point temperature in the exhaust gas.
  • the temperature in the exhaust gas can now be lowered by changing the air ratio until the dew point temperature is just not undercut.
  • a boiler 3 is installed within a room 1, which is delimited by walls 2 of a building.
  • This boiler can be a cast iron boiler as well as a welded steel boiler which is heated by a burner 4.
  • This burner can be an oil or gas burner, and the gas burner can also be designed as a fan burner or as an atmospheric gas burner.
  • the boiler is connected to the atmosphere 6 via an exhaust pipe 5, the temperature of which is exposed to an outside temperature sensor 7, which is connected to a controller 9 via a measuring line 8.
  • a dew point temperature sensor 11 is connected to the controller via a line 10 as a further actual value transmitter, which is arranged in the exhaust pipe 5 downstream of the actual boiler heat exchanger.
  • the boiler is connected via a flow line 12 and a return line 13 to a 4-way mixing valve 14, from which a heating circuit flow line 15 and a heating circuit return line 16 originate, which in turn connect a heating system with a pump via a large number of radiators are connected.
  • the temperature of the radiator running line 15 is sensed by a temperature sensor 17 which is connected to the controller 9 via a measuring line 18.
  • An actuator of the mixer 14 is connected to the controller 9 via an actuating line 19.
  • a continuously adjustable gas valve 21 is connected to the controller 9, which is arranged in the course of a gas supply line 22 and feeds the burner with gas.
  • This continuously adjustable gas valve can be a known, pneumatically working, continuously adjustable gas valve of a known type.
  • an adjustable oil feed pump or a continuously variable solenoid valve is provided instead of the gas valve 21.
  • the burner is designed as a forced draft burner, and the air access to the burner can be adjusted via a throttle orifice 23, which has a servomotor, not shown, which is acted upon by the controller 9 via a line 24.
  • the control device described in FIG. 1 has the following function:
  • a certain gas throughput is predetermined by the burner.
  • the controller 9 is given a specific reference variable as a load which, in the case of a known gas type, can only be achieved with a certain gas throughput in the time unit.
  • the gas valve 21 is preset on this gas throughput.
  • the burner 4 is ignited, and a certain position of the throttle orifice 23 results via the line 24, which leads to a specific, appropriate air throughput.
  • the hot exhaust gases from the burner act on the boiler heat exchanger inside the boiler 3 and reach the exhaust pipe 5 as cooled exhaust gas.
  • the dew point temperature sensor 11 is acted on, which switches a specific temperature measurement signal to the controller 9 as an actual value on its line 10. If the dew point temperature has already fallen below in the exhaust pipe, this means that the air excess is too small.
  • a command to increase the air throughput by varying the position of the throttle orifice 23 results via the controller 9.
  • This actuating movement is continued until there is no longer a drop below the dew point.
  • the controller is adjusted so that it tries to lower the temperature of the exhaust gases in the exhaust pipe 5 by increasing the Lubt admixture so that a wet precipitation does not occur due to the temperature falling below the dew point.
  • This mode of operation of the fuel-air ratio control is independent of the load on the boiler, i.e. the gas throughput just required.
  • the fuel gas is varied (transition from natural gas to town gas or liquefied petroleum gas) there are different values for the dependence of the dew point temperature on the air ratio, but these values can be adjusted on the controller so that the controller can also be adapted to all types of gas.
  • a flow temperature control also takes place, in that the temperature is reported by the sensor 17 to the controller 9 and adjusted to compensate for any control deviation of the flow temperature of the mixing valve 14.
  • a return temperature control could also take place here instead of a flow temperature control, it would also be possible to omit the mixing valve and to connect the lines 12 and 15 or 16 and 13 directly to one another and to work with a pure burner control. The air / fuel ratio control remains unaffected.
  • FIG. two shows the application of the ratio control according to the invention to a circulating water heater.
  • This circulating water heater 30 is connected via the flow line 12 to the radiators 34, which in turn are connected to the return line 13 via a pump 35.
  • the heat exchanger 36 is integrated in the housing of the circulating water heater. Instead of a circulation water heater, it could just as well be a pure water heater or a storage tank. It is essential that an atmospheric burner 4 is used here, which is fed via the gas line 22 via a gas valve 21, which is connected to the controller 9 via a servomotor 37.
  • the gas valve 21 can be continuously adjusted proportionally via the servomotor 37.
  • the controller 9 is connected to the dew point temperature sensor 11 via line 10, likewise via line 8 to the outside temperature sensor 7.
  • the burner 4 is designed as a premix burner, the circulating water heater 30 is connected to a secondary air supply opening 38, which is used as a cylindrical channel is formed and can be more or less closed with a flap 32.
  • the flap is connected via a shaft 33 to a servomotor 31, which is acted upon by the controller 9 via the actuating line 24.
  • This control device works analogously to that according to FIG. 1, starting from the outside temperature or another variable which specifies the load, a certain gas throughput is predetermined by the burner 4.
  • This gas throughput includes a certain amount of air supply in the time unit, which can be adjusted by adjusting the secondary air inlet opening 38 to a greater or lesser extent.
  • the setting of the secondary air supply and also the primary air supply thus takes place by adjusting the shaft 33 via the servomotor 31.
  • the exhaust gas generated by the burner 4 is cooled in the heat exchanger 36 and then reaches the exhaust pipe 5.
  • the sensor 11 detects whether the dew point temperature is above or below. If the dew point temperature is undershot, the air throughput is increased until the dew point temperature is exceeded; if the dew point temperature is exceeded, the air supply is reduced until the dew point temperature has just been reached.
  • This actual value transmitter 11 is a double Peltier element, one part 40 of which is integrated in the actual sensor element 41, while the other sensor element 42 is arranged at a distance outside the exhaust pipe 5. Both Peltier elements are connected to each other via a line 43 and 44, a line voltage source 45 being arranged in line 44. This can consist of a battery or a power supply. The same voltage can also be supplied by an electronic part 46 which is connected to the two connections of line 44 by two output lines 47 and 48. The electronic part 46 can periodically switch the direct voltage that is applied to the lines 47 and 48. Resistance tracks 49 are applied to the surface of the sensor 41, which change their resistance as well as moisture is deposited on the surface.
  • the Peltier elements consist of a combination of metal elements which, when a DC voltage is applied to them, assume different temperature levels. When the polarity of the DC voltage is reversed, the contact points of the Peltier elements exchange their temperatures. If the cold side of a Peltier element is now brought into an exhaust gas mixture from a fuel-heated heat source, water will fail as condensate when the dew point temperature of the water vapor is reached if the temperature falls below the dew point. The presence of precipitated water as condensate can then be determined by measuring the resistance of the individual resistance elements 49. The resistors are connected to the electronics part 46 via lines 50. By the Conductive condensate results in a large decrease in the resistance value in the area of the resistors.
  • the surface temperature of the sensor can be measured with the help of an NTC sensor or thermocouple.
  • a temperature sensor 51 is provided, which is connected to the controller 9 via the line 10.
  • the direct voltage on lines 47 and 48 is reversed. This heats up the cold measuring point of the Peltier element and the condensate evaporates.
  • the polarity is reversed again, and the dew point temperature at the measuring point in the exhaust pipe is again undershot.
  • the temperature is measured again via the temperature sensor 51 and passed to the controller 9. The timing of the measurement depends on the thermal inertia of the measuring cell and the thermal force of the Peltier element.
  • a suitable construction of the sensor 41 would also enable a continuous measurement of the dew point temperature.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Control Of Combustion (AREA)
  • Air-Conditioning For Vehicles (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Control Of The Air-Fuel Ratio Of Carburetors (AREA)

Abstract

1. A system for the automatic control of the fuel-air ratio in a heat source, comprising a controller (9) for an automatic control of the exhaust gas temperature by a control of a final control element (23) for controlling the supply of air, characterized in that an actual-value sensor (11) measures the dew point temperature and the exhaust gas temperature and that the controller (9) by means of the final control element (23) increases and decreases the supply of air in response to a drop and rise, respectively of the exhaust gas temperature through the dew point temperature.

Description

Die vorliegende Erfindung bezieht sich auf eine Regeleinrichtung gemäß dem Oberbegriff des Hauptanspruchs.The present invention relates to a control device according to the preamble of the main claim.

Eine solche Regeleinrichtung ist gemäß Artikel 54(3) EPO bekannt aus der EP-A-147 632.Such a control device is known from EP-A-147 632 in accordance with Article 54 (3) EPO.

Weiterhin ist es aus der DE-A-3 130 532 bei Verbrennungsaulagen bekannt die Abgastemperatur oberhalb des Taupunkts zu halten.Furthermore, it is known from DE-A-3 130 532 for combustion systems to keep the exhaust gas temperature above the dew point.

Weiterhin sind Regeleinrichtungen bekanntgeworden, die als Meßgröße entweder die Restkonzentration des Sauerstoffs im Abgas oder den OZ-Gehalt dieses Abgases benutzen. Die genannten Regeleinrichtungen benötigen aufgrund der Tatsache, daß hier eine wie auch immer geartete kontinuierlich arbeitende quantitative Gasanalyse vorgenommen werden muß, einen hohen meßtechnischen Aufwand. Die hohen Kosten der Sauerstoff- beziehungsweise Kohlendioxidanalyse rechtfertigen den Einsatz dieser Meß- und Regelmethoden bislang nur im industriellen Großofenbau.Control devices have also become known which use either the residual concentration of oxygen in the exhaust gas or the O Z content of this exhaust gas as the measurement variable. Due to the fact that any kind of continuously operating quantitative gas analysis has to be carried out, the control devices mentioned require a high level of measurement technology. The high costs of oxygen and carbon dioxide analysis have so far only justified the use of these measurement and control methods in large industrial furnace construction.

Die vorliegende Erfindung bezweckt den Aufbau einer Verhältnisregelung für das Luft-Brennstoff-Verhältnis einer. Kleinwärmequelle etwa im Bereich zwischen 5 und 30 kW. Bei einer solchen kleinen Wärmequelle darf der Preis für die Regeleinrichtung einen gewissen kleinen Prozentsatz in Relation zu dem Gesamtgerätepreis nicht übersteigen, da sonst die Regeleinrichtung vom Betreiber der Wärmequelle nicht akzeptiert wird.The present invention aims to establish a ratio control for the air-fuel ratio. Small heat source in the range between 5 and 30 kW. With such a small heat source, the price for the control device must not exceed a certain small percentage in relation to the total device price, since otherwise the control device will not be accepted by the operator of the heat source.

Die Erfindung geht von der Erkenntnis aus, daß es einen Zusammenhang zwischen der Luftzahl und der Taupunkttemperatur im Abgas gibt. In weiterer erfindungsgemäßer Erkenntnis kann man nun die Temperatur im Abgas durch Verändern der Luftzahl soweit erniedrigen, bis die Taupunkttemperatur gerade noch nicht unterschritten wird. Damit besteht die erfindungsge- mäße Lösung in den kennzeichnenden Merkmale des Anspruchs 1.The invention is based on the knowledge that there is a connection between the air ratio and the dew point temperature in the exhaust gas. In further knowledge according to the invention, the temperature in the exhaust gas can now be lowered by changing the air ratio until the dew point temperature is just not undercut. Thus, there he f indungsge- Permitted solution in the characterizing features of claim 1.

Weitere Ausgestaltungen und besonders vorteilhafte Weiterbildungen der Erfindung sind Gegenstand der Unteransprüche beziehungsweise gehen aus der nachfolgenden Beschreibung hervor, die ein Ausführungsbeispiel der Erfindung anhand der Figuren eins bis drei näher erläutert. Es zeigen

  • Figur eins eine Prinzipdarstellung eines Kessels mit der erfindungsgemäßen Regeleinrichtung,
  • Figur zwei einen Umlaufwasserheizer mit der Regeleinrichtung und
  • Figur drei den schematischen Aufbau des Istwertgebers.
Further refinements and particularly advantageous developments of the invention are the subject of the subclaims or emerge from the following description, which explains an exemplary embodiment of the invention with reference to FIGS. One to three. Show it
  • FIG. 1 shows a schematic diagram of a boiler with the control device according to the invention,
  • Figure two a circulating water heater with the control device and
  • Figure three shows the schematic structure of the actual value transmitter.

In allen drei Figuren bedeuten gleiche Bezugszeichen jeweils die gleichen Einzelheiten.In all three figures, the same reference numerals denote the same details.

Innerhalb eines Aufstellungsraums 1, der durch Wände 2 eines Gebäudes begrenzt ist, ist ein Kessel 3 aufgestellt. Bei diesem Kessel kann es sich um einen Gußkessel sowie auch um einen geschweißten Stahlkessel handeln, der von einem Brenner 4 beheizt ist. Bei diesem Brenner kann es sich um einen ÖI- oder Gasbrenner handeln, weiterhin ist die Ausbildung des Gasbrenners sowohl als Gebläsebrenner wie auch als atmosphärischer Gasbrenner möglich. Der Kessel ist über ein Abgasrohr 5 mit der Atmosphäre 6 verbunden, deren Temperatur einem Außentemperaturfühler 7 ausgesetzt ist, der über eine Meßleitung 8 mit einem Regler 9 verbunden ist. Mit dem Regler ist über eine Leitung 10 ein Taupunkttemperaturfühler 11 als weiterer Istwertgeber verbunden, der im Abgasrohr 5 stromab des eigentlichen Kesselwärmetauschers angeordnet ist.A boiler 3 is installed within a room 1, which is delimited by walls 2 of a building. This boiler can be a cast iron boiler as well as a welded steel boiler which is heated by a burner 4. This burner can be an oil or gas burner, and the gas burner can also be designed as a fan burner or as an atmospheric gas burner. The boiler is connected to the atmosphere 6 via an exhaust pipe 5, the temperature of which is exposed to an outside temperature sensor 7, which is connected to a controller 9 via a measuring line 8. A dew point temperature sensor 11 is connected to the controller via a line 10 as a further actual value transmitter, which is arranged in the exhaust pipe 5 downstream of the actual boiler heat exchanger.

Der Kessel ist über eine Vorlaufleitung 12 und eine Rücklaufleitung 13 mit einem 4-Wege-Mischventil 14 verbunden, von dem eine Heizkreis-Vorlaufleitung 15 und eine Heizkreis-Rücklaufleitung 16 abgehen, die ihrerseits über eine Vielzahl von Radiatoren eine Heizungsanlage unter Zwischenschaltung einer Pumpe miteinander verbunden sind. Die Temperatur der Heizkörperlaufleitung 15 wird durch einen Temperaturfühler 17 abgefühlt, der über eine Meßleitung 18 mit dem Regler 9 verbunden ist. Über eine Stellleitung 19 ist ein Stellmotor des Mischers 14 mit dem Regler 9 verbunden.The boiler is connected via a flow line 12 and a return line 13 to a 4-way mixing valve 14, from which a heating circuit flow line 15 and a heating circuit return line 16 originate, which in turn connect a heating system with a pump via a large number of radiators are connected. The temperature of the radiator running line 15 is sensed by a temperature sensor 17 which is connected to the controller 9 via a measuring line 18. An actuator of the mixer 14 is connected to the controller 9 via an actuating line 19.

Über eine weitere Stelleitung 20 ist ein stufenlos verstellbares Gasventil 21 mit dem Regler 9 verbunden, das im Zuge einer Gaszuleitung 22 angeordnet ist und den Brenner mit Gas speist. Bei diesem stufenlos verstellbaren Gasventil kann es sich um eine an sich bekannte, pneumatisch arbeitende, stetig verstellbare Gasarmatur bekannter Bauart handeln. Bei Verwendung eines Ölbrenners ist statt des Gasventils 21 eine vertellbare Ölförderpumpe oder ein stetig variierbares Magnetventil vorgesehen. Der Brenner ist im Ausführungsbeispiel nach Figur eins als Gebläsebrenner ausgebildet, der Luftzutritt zum Brenner ist über eine Drosselblende 23 verstellbar, die einen nicht weiter dargestellten Stellmotor besitzt, der über eine Stelleitung 24 von dem Regler 9 beaufschlagt ist.Via a further line 20, a continuously adjustable gas valve 21 is connected to the controller 9, which is arranged in the course of a gas supply line 22 and feeds the burner with gas. This continuously adjustable gas valve can be a known, pneumatically working, continuously adjustable gas valve of a known type. When using an oil burner, an adjustable oil feed pump or a continuously variable solenoid valve is provided instead of the gas valve 21. In the exemplary embodiment according to FIG. 1, the burner is designed as a forced draft burner, and the air access to the burner can be adjusted via a throttle orifice 23, which has a servomotor, not shown, which is acted upon by the controller 9 via a line 24.

Die nach Figur eins beschriebene Regeleinrichtung besitzt folgende Funktion:The control device described in FIG. 1 has the following function:

Ausgehend von der Außentemperatur oder einer anderen die Belastung vorgebenden Größe wird ein bestimmter Gasdurchsatz durch den Brenner vorgegeben.On the basis of the outside temperature or another variable which specifies the load, a certain gas throughput is predetermined by the burner.

Nach Maßgabe der Vorlauftemperatur wird dem Regler 9 eine bestimmte Führungsgröße als Last vorgegeben, die bei bekannter Gasart nur mit einem bestimmten Gasdurchsatz in der Zeiteinheit erreichbar ist. Auf diesem Gasdurchsatz wird das Gasventil 21 voreingestellt. Der Brenner 4 wird gezündet, und über die Stelleitung 24 resultiert eine bestimmte Stellung der Drosselblende 23, die zu einem bestimmten, hierzu passenden Luftdurchsatz führt. Die heißen Abgase des Brenners beaufschlagen den Kesselwärmetauscher im Innern des Kessels 3 und gelangen als abgekühltes Abgas in das Abgasrohr 5. Hier wird der Taupunkttemperaturfühler 11 beaufschlagt, der auf seiner Leitung 10 ein bestimmtes Temperaturmeßsignal als Istwert auf den Regler 9 schaltet. Ist die Taupunkttemperatur bereits im Abgasrohr unterschritten, so bedeutet dies, daß der Luftüberschuß zu klein ist. Demgemäß resultiert über den Regler 9 ein Befehl zur Vergrößerung des Luftdurchsatzes durch Variation der Stellung der Drosselblende 23. Diese Stellbewegung wird so lange fortgesetzt, bis keine Taupunktunterschreitung mehr stattfindet. Für den Fall, daß eine Taupunktunterschreitung nicht vorliegt, versucht der Regler 9, durch Verkleinern des Luftdurchsatzes die optimale Luftzahl zu erreichen, die bei einem Gebläsebrenner etwa beil λ=1,1 bis 1,2 liegt. Dieser Wert wird erreicht, wenn die Taupunkttemperatur gerade nicht erreicht wird. Der Regler ist so justiert, daß er durch Vergrößern der Lubtbeimischung die Temperatur der Abgase im Abgasrohr 5 so weit zu senken versucht, daß gerade nicht ein feuchter Niederschlag durch Unterschreiten der Taupunkttemperatur auftritt. Diese Wirkungsweise der Brennstoff-Luftverhältnisregelung ist unabhängig von der Belastung des Kessels, also dem gerade notwendigen Gasdurchsatz. Bei Variation des Brenngases (Übergang von Erdgas auf Stadtgas oder Flüssiggas) ergeben sich zwar andere Werte für die Abhängigkeit der Taupunkttemperatur von der Luftzahl, nur können diese Werte am Regler justiert werden, so daß der Regler auch für alle Gasarten anpaßbar ist. Umabhängig von dieser Brennstoff-Luftverhältnisregelung findet noch eine Vorlauftemperaturregelung statt, indem die Temperatur vom Fühler 17 auf den Regler 9 gemeldet und zum Ausgleich einer etwaigen Regelabweichung der Vorlauftemperatur des Mischventils 14 nachgestellt wird. Ebensogut könnte hier statt einer Vorlauftemperaturregelung auch eine Rücklauftemperaturregelung stattfinden, es wäre auch möglich, das Mischventil entfallen zu lassen und die Leitungen 12 und 15 beziehungsweise 16 und 13 unmittelbar miteinander zu verbinden und mit einer reinen Brennersteuerung zu arbeiten. Die Verhältnisregelung Luft/Brennstoff bleibt hiervon unberührt.In accordance with the flow temperature, the controller 9 is given a specific reference variable as a load which, in the case of a known gas type, can only be achieved with a certain gas throughput in the time unit. The gas valve 21 is preset on this gas throughput. The burner 4 is ignited, and a certain position of the throttle orifice 23 results via the line 24, which leads to a specific, appropriate air throughput. The hot exhaust gases from the burner act on the boiler heat exchanger inside the boiler 3 and reach the exhaust pipe 5 as cooled exhaust gas. Here, the dew point temperature sensor 11 is acted on, which switches a specific temperature measurement signal to the controller 9 as an actual value on its line 10. If the dew point temperature has already fallen below in the exhaust pipe, this means that the air excess is too small. Accordingly, a command to increase the air throughput by varying the position of the throttle orifice 23 results via the controller 9. This actuating movement is continued until there is no longer a drop below the dew point. In the event that the temperature does not drop below the dew point, the controller 9 tries to achieve the optimum air ratio by reducing the air throughput, which is approximately λ = 1.1 to 1.2 for a forced draft burner. This value is reached when the dew point temperature is not being reached. The controller is adjusted so that it tries to lower the temperature of the exhaust gases in the exhaust pipe 5 by increasing the Lubt admixture so that a wet precipitation does not occur due to the temperature falling below the dew point. This mode of operation of the fuel-air ratio control is independent of the load on the boiler, i.e. the gas throughput just required. When the fuel gas is varied (transition from natural gas to town gas or liquefied petroleum gas) there are different values for the dependence of the dew point temperature on the air ratio, but these values can be adjusted on the controller so that the controller can also be adapted to all types of gas. Depending on this fuel-air ratio control, a flow temperature control also takes place, in that the temperature is reported by the sensor 17 to the controller 9 and adjusted to compensate for any control deviation of the flow temperature of the mixing valve 14. A return temperature control could also take place here instead of a flow temperature control, it would also be possible to omit the mixing valve and to connect the lines 12 and 15 or 16 and 13 directly to one another and to work with a pure burner control. The air / fuel ratio control remains unaffected.

Figur zwei zeigt die Anwendung der erfindungsgemäßen Verhältnisregelung auf einen Umlaufwasserheizer. Dieser Umlaufwasserheizer 30 ist über die Vorlaufleitung 12 an die Radiatoren 34 angeschlossen, die ihrerseits über eine Pumpe 35 mit der Rücklaufleitung 13 verbunden sind. Der Wärmetauscher 36 ist im Gehäuse des Umlaufwasserheizers integriert. Statt eines Umlaufwasserheizers könnte es sich genausogut um einen reinen Brauchwasserbereiter handeln oder um einen Speicher. Wesentlich ist, daß hier ein atmosphärischer Brenner 4 benutzt ist, der über die Gasleitung 22 über eine Gasarmatur 21 gespeist ist, die über einen Stellmotor 37 mit dem Regler 9 verbunden ist. Über den Stellmotor 37 kann das Gasventil 21 stetig proportional verstellt werden. Der Regler 9 ist mit dem Taupunkttemperaturfühler 11 über die Leitung 10 verbunden, gleichermaßen über die Leitung 8 mit dem Außentemperaturfühler 7. Es besteht die Möglichkeit, den Brenner 4 als Vormischbrenner auszugestalten, der Umlaufwasserheizer 30 ist mit einer Sekundär-Luftzufuhröffnung 38 verbunden, die als zylindrischer Kanal ausgebildet ist und mit einer Klappe 32 mehr oder weniger verschließbar ist. Die Klappe ist über eine Welle 33 mit einem Stellmotor 31 verbunden, der über die Stelleitung 24 vom Regler 9 beaufschlagt wird. Diese Regeleinrichtung arbeitet analog zu der nach Figur eins, ausgehend von der Außentemperatur oder einer anderen die Belastung vorgebenden Größe wird ein bestimmter Gasdurchsatz durch den Brenner 4 vorgegeben. Zu diesem Gasdurchsatz gehört eine bestimmte Luftzufuhrmenge in der Zeiteinheit, die durch mehr oder weniger großes Verstellen der Sekundär-Lufteinlaßöffnung 38 eingestellt werden kann. Die Einstellung der Sekundär-Luftzufuhr beziehungsweise auch der Primär-Luftzufuhr geschieht somit durch ein Verstellen der Welle 33 über den Stellmotor 31. Das vom Brenner 4 erzeugte Abgas wird im Wärmtauscher 36 abgekühlt und gelangt anschließend ins Abgasrohr 5. Hier wird vom Meßfühler 11 erfaßt, ob die Taupunkttempertur über- oder unterschritten ist. Im Falle der Unterschreitung der Taupunktemperatur wird der Luftdurchsatz erhöht bis die Taupunkttemperatur überschritten ist, im Falle der vorliegenden Taupunkttemperatur-Überschreitung wird die Luftzufuhr verringert, bis die Taupunkttemperatur gerade erreicht ist.Figure two shows the application of the ratio control according to the invention to a circulating water heater. This circulating water heater 30 is connected via the flow line 12 to the radiators 34, which in turn are connected to the return line 13 via a pump 35. The heat exchanger 36 is integrated in the housing of the circulating water heater. Instead of a circulation water heater, it could just as well be a pure water heater or a storage tank. It is essential that an atmospheric burner 4 is used here, which is fed via the gas line 22 via a gas valve 21, which is connected to the controller 9 via a servomotor 37. The gas valve 21 can be continuously adjusted proportionally via the servomotor 37. The controller 9 is connected to the dew point temperature sensor 11 via line 10, likewise via line 8 to the outside temperature sensor 7. It is possible to design the burner 4 as a premix burner, the circulating water heater 30 is connected to a secondary air supply opening 38, which is used as a cylindrical channel is formed and can be more or less closed with a flap 32. The flap is connected via a shaft 33 to a servomotor 31, which is acted upon by the controller 9 via the actuating line 24. This control device works analogously to that according to FIG. 1, starting from the outside temperature or another variable which specifies the load, a certain gas throughput is predetermined by the burner 4. This gas throughput includes a certain amount of air supply in the time unit, which can be adjusted by adjusting the secondary air inlet opening 38 to a greater or lesser extent. The setting of the secondary air supply and also the primary air supply thus takes place by adjusting the shaft 33 via the servomotor 31. The exhaust gas generated by the burner 4 is cooled in the heat exchanger 36 and then reaches the exhaust pipe 5. Here, the sensor 11 detects whether the dew point temperature is above or below. If the dew point temperature is undershot, the air throughput is increased until the dew point temperature is exceeded; if the dew point temperature is exceeded, the air supply is reduced until the dew point temperature has just been reached.

Aus der Figur drei geht der Aufbau des Meßfühlers beziehungsweise Istwertgebers 11 hervor. Bei diesem Istwertgeber 11 handelt es sich um ein doppeltes Peltierelement, dessen einer Teil 40 in das eigentliche Fühlerelement 41 integriert ist, während das andere Fühlerelement 42 im Abstand außerhalb des Abgasrohres 5 angeordet ist. Beide Peltierelemente sind über je eine Leitung 43 und 44 miteinander verbunden, wobei in der Leitung 44 eine Gleischspannungsquelle 45 angeordnet ist. Diese kann aus einer Batterie oder einem Netzteil bestehen. Die Gleischspannung kann auch von einem Elektronikteil 46 geliefert werden, das mit zwei Ausgangsleitungen 47 und 48 mit den beiden Anschlüssen der Leitung 44 verbunden ist. Von dem Elektronikteil 46 kann die Gleichspannung, die auf die Leitungen 47 und 48 gegeben wird, periodisch umgeschaltet werden. Auf die Oberfläche des Fühlers 41 sind Widerstandsbahnen 49 aufgebracht, die ihren Widerstand ändern, sowie sich auf der Oberfläche Feuchte niederschlägt.The structure of the sensor or actual value transmitter 11 is shown in FIG. This actual value transmitter 11 is a double Peltier element, one part 40 of which is integrated in the actual sensor element 41, while the other sensor element 42 is arranged at a distance outside the exhaust pipe 5. Both Peltier elements are connected to each other via a line 43 and 44, a line voltage source 45 being arranged in line 44. This can consist of a battery or a power supply. The same voltage can also be supplied by an electronic part 46 which is connected to the two connections of line 44 by two output lines 47 and 48. The electronic part 46 can periodically switch the direct voltage that is applied to the lines 47 and 48. Resistance tracks 49 are applied to the surface of the sensor 41, which change their resistance as well as moisture is deposited on the surface.

Die Peltierelemente bestehen aus Metallelementkombination, die, wenn man an sie eine Gleichspannung anlegt, unterschiedliche Temperaturniveaus annehmen. Bie Umpolung der Gleichspannung vertauschen die Kontaktstellen der Peltierelemente ihre Temperaturen. Bringt nunmehr die kalte Seite eines Peltierelements in ein Abgasgemisch einer brennstoffbeheizten Wärmequelle, so wird bei Erreichen der Taupunkttemperatur des Wasserdampfes Wasser als Kondensat ausfallen, wenn die Taupunkttemperatur unterschritten wird. Das Vorhandensein niedergeschlagenen Wasser als Kondensat kann dann durch die Widerstandsmessung der einzelnen Widerstandselemente 49 festgestellt werden. Die Widerstände sind heirzu über Leitungen 50 mit dem Elektronikteil 46 verbunden. Durch das leitende Kondenswasser ergibt sich im Bereich der Widerstände eine große Widerstandswertabnahme. In diesem Augenblick kann mit Hilfe eines NTC-Fühlers oder Thermoelements die Messung der Oberflächentemperatur des Fühlers erfolgen. Hierzu ist ein Temperaturfühler 51 vorgesehen, der über die Leitung 10 mit dem Regler 9 verbunden ist. Nach erfolgter Registrierung der Taupunkttemperatur wird die Gleichspannung auf den Leitungen 47 und 48 umgepolt. Damit erwärmt sich die kalte Meßstelle des Peltierelements, und das Kondensat verdampft. Nach diesem Vorgang erfolgt eine erneute Umpolung, wobei die Taupunkttemperatur an der Meßstelle im Abgasrohr wieder unterschritten wird. Im Moment des Feuchteniederschlags aufgrund des kondensierenden Abgases wird über den Temperaturfühler 51 wieder die Temperatur gemessen und auf den Regler 9 gegeben. Die zeitliche Folge der Messung ist von der thermischen Trägheit der Meßzelle und der Thermokraft des Peltierelements abhängig. Durch einen geeigneten Aufbau des Meßfühlers 41 wäre auch eine kontinuierliche Messung der Taupunkttemperatur möglich.The Peltier elements consist of a combination of metal elements which, when a DC voltage is applied to them, assume different temperature levels. When the polarity of the DC voltage is reversed, the contact points of the Peltier elements exchange their temperatures. If the cold side of a Peltier element is now brought into an exhaust gas mixture from a fuel-heated heat source, water will fail as condensate when the dew point temperature of the water vapor is reached if the temperature falls below the dew point. The presence of precipitated water as condensate can then be determined by measuring the resistance of the individual resistance elements 49. The resistors are connected to the electronics part 46 via lines 50. By the Conductive condensate results in a large decrease in the resistance value in the area of the resistors. At this moment, the surface temperature of the sensor can be measured with the help of an NTC sensor or thermocouple. For this purpose, a temperature sensor 51 is provided, which is connected to the controller 9 via the line 10. After the dew point temperature has been registered, the direct voltage on lines 47 and 48 is reversed. This heats up the cold measuring point of the Peltier element and the condensate evaporates. After this process, the polarity is reversed again, and the dew point temperature at the measuring point in the exhaust pipe is again undershot. At the moment of the moisture precipitation due to the condensing exhaust gas, the temperature is measured again via the temperature sensor 51 and passed to the controller 9. The timing of the measurement depends on the thermal inertia of the measuring cell and the thermal force of the Peltier element. A suitable construction of the sensor 41 would also enable a continuous measurement of the dew point temperature.

Claims (6)

1. A system for the automatic control of the fuel-air ratio in a heat source, comprising a controller (9) for an automatic control of the exhaust gas temperature by a control of a final control element (23) for controlling the supply of air, characterized in that an actual-value sensor (11) measures the dew point temperature and the exhaust gas temperature and that the controller (9) by means of the final control element (23) increases and decreases the supply of air in response to a drop and rise, respectively of the exhaust gas temperature through the dew point temperature.
2. An automatic control apparatus according to claim 1, characterized in that the actual-value sensor (11) consists of a humidity sensor (41).
3. An automatic control apparatus according to claim 1 or 2, characterized in that the actual-value sensor consists of a Peltier element.
4. An automatic control apparatus according to claim 3, characterized in that two Peltier elements (40, 42) are provided and one of them is disposed in the exhaust gas stream.
5. An automatic control apparatus according to any of claims 1 to 4, characterized in that a change-pole voltage source (46) is provided, which periodically applies to the two Peltier elements a d.c. voltage having a reversible polarity.
6. An automatic control system according to any of claims 1 to 5, characterized in that a temperature sensor (51) is provided on the surface of the sensor (41) and is used to measure the exhaust gas temperature at the instant at which a condensation occurs in the exhaust gas.
EP85104923A 1984-05-03 1985-04-23 Air to fuel-ratio controller for a heating source Expired - Lifetime EP0160884B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT85104923T ATE56084T1 (en) 1984-05-03 1985-04-23 CONTROL DEVICE FOR THE FUEL-AIR RATIO OF A HEAT SOURCE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE8413677 1984-05-03
DE8413677U 1984-05-03

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EP0160884A2 EP0160884A2 (en) 1985-11-13
EP0160884A3 EP0160884A3 (en) 1986-05-21
EP0160884B1 true EP0160884B1 (en) 1990-08-29

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Publication number Priority date Publication date Assignee Title
CA1253592A (en) * 1985-02-15 1989-05-02 Tatsuya Tsuda Heating apparatus with humidity sensor
ATE76957T1 (en) * 1987-10-24 1992-06-15 Mindermann Kurt Henry METHOD OF CONTROLLING THE COMBUSTION OF FUEL WITH LARGELY FLUSHING CALCULATORY VALUE.
AU3356995A (en) * 1994-08-16 1996-03-07 Industrial Research Limited A dew point sensor
DE19607854A1 (en) * 1996-03-01 1997-09-04 Bosch Gmbh Robert Heater and method for controlling a heater
FR2777075B1 (en) * 1998-04-02 2000-05-19 Air Liquide METHOD FOR OPERATING AN OVEN AND DEVICE FOR IMPLEMENTING THE METHOD
AT414037B (en) 2004-08-24 2006-08-15 Vaillant Gmbh METHOD FOR AVOIDING CONDENSATION ON FAN SUPPORTED FUEL-DRIVEN HEATING EQUIPMENT
EP2159525A1 (en) * 2008-08-29 2010-03-03 Air Liquide Deutschland GmbH Method for operating an oven and device for carrying out the method
CN112964747B (en) * 2021-03-10 2022-04-22 北京科技大学 Gas condensation visualization and heat exchange characteristic detection device and method

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EP0147632A1 (en) * 1983-12-24 1985-07-10 M.A.N. MASCHINENFABRIK AUGSBURG-NÜRNBERG Aktiengesellschaft Method to operate a burner

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US4033712A (en) * 1976-02-26 1977-07-05 Edmund D. Hollon Fuel supply systems
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DE3221660A1 (en) * 1981-06-11 1983-01-05 Paul G. Dipl.-Ing. Dr.techn. 8010 Graz Gilli Process for the purpose of optimum combustion in furnaces
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EP0147632A1 (en) * 1983-12-24 1985-07-10 M.A.N. MASCHINENFABRIK AUGSBURG-NÜRNBERG Aktiengesellschaft Method to operate a burner

Also Published As

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EP0160884A3 (en) 1986-05-21
EP0160884A2 (en) 1985-11-13
DE3579357D1 (en) 1990-10-04
ATE56084T1 (en) 1990-09-15

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