EP0007198B1 - Dispositif d'allumage - Google Patents

Dispositif d'allumage Download PDF

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Publication number
EP0007198B1
EP0007198B1 EP19790301238 EP79301238A EP0007198B1 EP 0007198 B1 EP0007198 B1 EP 0007198B1 EP 19790301238 EP19790301238 EP 19790301238 EP 79301238 A EP79301238 A EP 79301238A EP 0007198 B1 EP0007198 B1 EP 0007198B1
Authority
EP
European Patent Office
Prior art keywords
filament
ignition
ceramic
heating
fuel
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
Application number
EP19790301238
Other languages
German (de)
English (en)
Other versions
EP0007198A1 (fr
Inventor
Lawrence Miller Bryce
Peter Hamish Athey Roebuck
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
MORGANITE ELECTROHEAT Ltd
Original Assignee
MORGANITE ELECTROHEAT Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by MORGANITE ELECTROHEAT Ltd filed Critical MORGANITE ELECTROHEAT Ltd
Publication of EP0007198A1 publication Critical patent/EP0007198A1/fr
Application granted granted Critical
Publication of EP0007198B1 publication Critical patent/EP0007198B1/fr
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/22—Details

Definitions

  • the invention relates to fuel-ignition in heating boilers or other domestic or industrial gas or oil fuelled appliances.
  • DE-A1-2 501 894 a fuel-ignition device comprising an electrically conductive carbide heating element and means for passing a heating current to the element to raise it to fuel-ignition temperature. Further, the use of other ceramic materials as heating elements is known, (DE-B-1 238 126).
  • the present invention is a.
  • a fuel-ignition device comprising an electrically conductive carbide, boride, silicide, nitride, oxide or other ceramic monofilament as a heating element and means for passing a heating current to the filament to raise it to fuel-ignition temperature.
  • the filaments on which the success of the invention depends are made for example, by vapour deposition onto a preformed core or by drawing from a melt, and show a high tensile strength, up to 340 Kg/mm 2 in one particular silicon carbide filament we have tested. Such strengths may be contrasted with typical strengths below 10 Kg/mm 2 for ceramic bodies made by conventional ceramic techniques such as extrusion of plastic mixes, pressing, tamping and the like, whether or not followed by final machining stages.
  • the filament has a more conductive core of carbon or of tungsten or other metal.
  • a carbon core is preferred, on which for example silicon carbide, the preferred ceramic, is readily vapour deposited.
  • Silicon carbide filaments are produced for example for reinforcement purposes in composite materials, and one particular filament that is suitable for the present purpose is produced by continuous vapour deposition of A-silicon carbide on a carbon filament core, final diameter 140 microns. Such a filament is strong enough to stand repeated thermal cycling from room temperature to over 1100°C in ignition, as well as mechanical shocks to which equipment may be subjected.
  • the carbon core is important to the functioning of the device. At low temperatures, the carbon core itself carries the bulk of the current due to the relatively high cold resistance of the surrounding silicon carbide. Similar solid or tungsten-core silicon carbide filaments require increased power compared to the carbon core filament to attain ignition temperature due to their higher cold resistances. Power requirements can be controlled by varying the filament diameter and in particular the cross-sectional ratio of carbon core to silicon carbide annulus.
  • a continuous pre- heating current should be passed through the filament, when for example it is readily provided that the filament shall reach the ignition temperature in five seconds or less on passage of the heating current.
  • the presence of a conductive core is desirable for passage of such a current, which for example may be 20-30 mA at 10-15 V in the particular 140 micron carbon core silicon carbide filament described above.
  • a suitable preheating current for given circumstances is readily found by experiment, though the filament temperature it corresponds to is not easily measured.
  • Ignition temperatures readily measured by pyrometer observations, vary according to the conditions but sample figures for stoichiometric mixtures with air are:
  • a suitable nominal filament temperature for ignition as measured by the final filament temperature under a given power in still air, is readily established for given conditions of fuel/air flow, uniformity of mixing and temperature. It cannot be less than the ignition temperatures quoted above and for practical conditions is likely to be 1000°C or above and in any event not less than 800° or 900°C.
  • the mounting of the filament is preferably in a tubular or other disposable holder for impingement of a fuel/air flow on the filament.
  • the filament is retained in place by a crimped mounting of copper or other metal freely conductive of heat and electricity.
  • the terminals were then connected in a test circuit with a mains transformer (50 cycles), a voltmeter and an ammeter and a current of 250 mA at 40 volts applied.
  • the fibre heated to 1180°C and gave ignition in less than a second.
  • a further 1 cm sample of the fibre was then tested for resistance at different temperatures.
  • the resistance dropped from 260 ohms at 600°C (the lowest temperature used) to 155 ohms at 800°C and 140 ohms at 1000°C, and levelled off at 110 ohms at 1300 0 C, giving a valuable protection against overheating but a temperature sufficient to secure ignition in all reasonable circumstances (see Fig. 2).
  • the cold resistance was 435 ohms.
  • This graph differs from that of ⁇ -SiC due to the role played by the carbon core.
  • the igniter fibre itself is fitted in a small holder rather like a domestic fuse and equally easily replaceable.
  • the holder consists of a ceramic tube 1 with opposed holes 2 for gas flow, and terminal caps 5 with solder connections 3 for the fibre 4.
  • the holder is clipped at 7 into copper mountings 6 to which current supply wires 8 are fixed. Gas is directed onto the fibre by a burner nozzle 9 fed from a supply pipe 10 through a solenoid operated valve 11, the supply wires 12 of which are also shown.
  • the copper tube was soldered into the fuse housing and tested using the same apparatus as described in Fig. 3.
  • the already heated fibre igniter is introduced into the natural gas flame, the temperature of the fibre increases by up to 200°C. Though this should theoretically enhance oxidation, and reduce the service life, it appears that the natural gas shroud about the igniter actually forms a protective barrier against oxidation.
  • Cycling on this basis (30 minutes to 1 hour off period) showed a time delay prior to ignition (a slow power build up to overcome the cold resistance).
  • the time delay in the range 5 to 20 seconds, is undesirable but is readily overcome by applying a constant low power current of for example 0.5 watt to maintain the temperature above ambient, e.g. at 200°C.
  • one igniter in the centre of the hob can light a small auxiliary burner and flame tubes then light the main burners as required.
  • a separate igniter is used for the oven.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)

Claims (6)

1. Dispositif d'allumage de combustible comprenant un élément céramique de chauffage conducteur de l'électricité en carbure, borure, siliciure, nitrure, oxyde, ou autre, et des moyens pour faire passer un courant de chauffage dans l'élément pour élever sa température à celle l'allumage du combustible, caractérisé en ce que l'élément est un monofilament à noyau en tungstène ou autre métal, ou en carbone, sur lequel la céramique a été formée par dépôt par vaporisation, ou autrement, et qui a une conductivité électrique plus élevée que la céramique.
2. Dispositif selon la revendication 1, caractérisé en ce que le céramique est du carbure de silicium.
3. Dispositif selon la revendication 1 ou la revendication 2, caractérisé en ce que le filament est monté dans un support démontable tubulaire ou autre, pour qu'un flux de mélange combustible/air frappe le filament.
4. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que le filament est maintenu en place par une monture sertie en cuivre ou en un autre métal conducteur.
5. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comprend en outre des moyens pour faire passer un courant de préchauffage continu dans le filament pour lui permettre d'atteindre la température d'allumage en 5 secondes ou moins lors du passage du courant de chauffage.
6. Chaudière de chauffage ou autre appareil domestique ou industriel à gaz ou à mazout équipée d'un dispositif d'allumage selon l'une quelconque des revendications précédentes.
EP19790301238 1978-06-29 1979-06-26 Dispositif d'allumage Expired EP0007198B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2835778 1978-06-29
GB7828357 1978-06-29

Publications (2)

Publication Number Publication Date
EP0007198A1 EP0007198A1 (fr) 1980-01-23
EP0007198B1 true EP0007198B1 (fr) 1982-08-04

Family

ID=10498198

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19790301238 Expired EP0007198B1 (fr) 1978-06-29 1979-06-26 Dispositif d'allumage

Country Status (2)

Country Link
EP (1) EP0007198B1 (fr)
DE (1) DE2963478D1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2133866B (en) * 1983-01-19 1986-02-19 Atomic Energy Authority Uk Gas ignition
JPS62731A (ja) * 1985-06-27 1987-01-06 Jidosha Kiki Co Ltd デイ−ゼルエンジン用グロ−プラグ

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1238126B (de) * 1953-06-04 1967-04-06 Kanthal Ab Elektrisches Widerstandselement
DE1133842B (de) * 1959-01-15 1962-07-26 Auergesellschaft Ges Mit Besch Elektrische Heizleiter
DE1930018U (de) * 1965-09-30 1965-12-30 Walter Strohmaier Niederspannungs-elektrozuender fuer oel und gas, insbesondere fuer erdgas.
US3372305A (en) * 1966-04-15 1968-03-05 Carborundum Co Silicon carbide igniter
JPS5111558B2 (fr) * 1971-08-12 1976-04-12
FR2176596B1 (fr) * 1972-03-24 1974-12-13 Wonder
US3928910A (en) * 1972-09-18 1975-12-30 Tappan Co Gas igniter
GB1497871A (en) * 1974-01-21 1978-01-12 Carborundum Co Electrical igniter elements

Also Published As

Publication number Publication date
DE2963478D1 (en) 1982-09-30
EP0007198A1 (fr) 1980-01-23

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