Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
  • F23N5/10—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermocouples
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/46—Details, e.g. noise reduction means
  • F23D14/72—Safety devices, e.g. operative in case of failure of gas supply
  • F23D14/725—Protection against flame failure by using flame detection devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2208/00—Control devices associated with burners
  • F23D2208/10—Sensing devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2209/00—Safety arrangements
  • F23D2209/10—Flame flashback
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/08—Measuring temperature
  • F23N2225/14—Ambient temperature around burners

Definitions

• the invention relates to installation movens from the inside of the air-gas mixture supply duct of a gas burner. a conventional thermocouple to allow it to provide both
• thermocouple very strongly heated at the level of its elements close to the combustion chamber
• the device is particularly intended for devices whose combustion chamber operates in confinement at high temperatures and nevertheless requires the positioning of the thermocouple at the level of said chamber.
• thermocouples are components of a well-known safety device presented externally in the form of a metal sheath called an external conductor ending, side exposed to heat, by a probe tip. in a bulb forming a sheath subject to a socket, and at the other end by an electrical connection fitting to a safety valve
• thermocouple gives complete satisfaction in many applications or the configuration of combustion appliances gas allows the thermocouple to be placed so that only the hot solder of the probe tip is exposed to heat of a flame This is mainly the case with devices for pilot lights or combustion torches which are not confined in an enclosure for raising the temperature. And if the temperature, at the probe tip only, does not exceed 600 ° C.
• thermocouple remains within the limits of a normal service life and poses no particular problems except reasonable maintenance when the wear of the probe tip exposed to the oxidative combustion of an open flame ends up destroying the hot weld thus suppressing the generation of the electro-mot ⁇ ce force sought
• thermocouple To this is immediately added, upstream of the socket, the attack of the external conductor which becomes porous and particularly sensitive to oxidation and to the corrosive action of the burnt gases released by the neighboring combustion Under these conditions of temperature and proximity, the lifespan of a conventional thermocouple is very significantly reduced. The effort-deploves to extend this lifespan consists essentially in delaying these destructive effects.
• the known electrical switching devices are of "mechanical" design, whether this interruption is made by breaking a fuse or by the opening. of a thermostatic contact
• These devices obviously constitute an additional cost, with in addition the disadvantage of a "pirate” bypass always possible by an unconscious or reckless user
• the present invention therefore relates to cold security
• thermocouples to deal with the cause of the early deterioration of thermocouples when these are placed by necessity within combustion chambers brought to high temperature reaching more or less 950 ° C for hot secu ⁇ te
• thermocouple to perform the function, of hot safety without "mechanical" device for electrical shutdown And therefore to obtain overall with a conventional thermocouple long-term use at a minimum cost since it is used to provide both cold and hot safety functions on devices with confined combustion chamber having the advantage of generating high temperatures
• These high temperatures are particularly sought after for infrared light emitters in order to obtain electromagnetic wavelengths between 1.5 and 4 micrometers
• the invention consists of a device for arranging a thermocouple from the inside of the air-gas duct of a gas burner ensuring both the cold safety and hot safety functions, said thermocouple comprising a external conductor ending with a probe tip in a sheath bulb subject to a socket, characterized in that the part a al of the external conductor of the thermocouple, side probe tip, penetrates inside the inlet pipe of the mixture air-gas. in that the probe tip at the end of the bulb abuts on the internal surface of the contact area of the perforated wall of a diffusion chamber, and in that the arrangement device comprises a plate fixed transversely to the section of the air-gas duct opening.
• said plate having a surface of suitable size for fulfilling a screen-localizing function of the air-gas flow at the level of the zone of contact with the internal surface of the diffusion chamber, the base of the bulb support sleeve being also wedged in abutment in the light of the guide and positioning plate, the plate being subject either to the opening of the air-gas duct, or to the base of the diffusion chamber on the opening side of the duct
• thermocouple To position the thermocouple, by making it enter the interior of the inlet duct of the air-gas mixture. to open the probe tip at the end of the bulb inside the diffusion chamber in the center of the combustion chamber, or. if there is no diffusion chamber, at the outlet of the supply conduit into the combustion chamber itself according to details of arrangements which will be dec ⁇ ts later in an additional example with 1 aid of FIG. 3 - to guide the bulb 4 of the sensitive element (probe tip) of the thermocouple introduced into the duct, supplying the air-gas mixture and ensuring its exact positioning, the probe tip v abutting against the internal wall of the g ⁇ lle constituting the chamber of diffusion,
• This quieter mini-zone forces a plot of the grid wall of the diffusion chamber to blush very locally.
• the air-gas mixture enters combustion near the grid in the sheltered mini-zone. It is precisely at this very place that the probe tip abuts against the reddened grid or alone, therefore, the hot solder end is stressed by the necessary and sufficient heat to generate the electro-motive force sought and therefore to obtain the "cold" safety function thanks to the sheltered mini-zone.
• the temperature measurements at the probe tip are confined to around 500 ° C.
• thermocouple Upstream of the probe tip and the bulb, all the rest of the thermocouple being ventilated by the fresh air-gas flow sees its the temperature is established at a level much lower than that of the hot weld, this difference reaching several hundred degrees centigrade. Furthermore, this ventilation by the fresh and fresh flow protects it from any contact with the surrounding gases of neighboring combustion, gases which are all the more corrosive as they are extremely hot, and consequently very damaging for the thermocouple. as for its longevity. To perform the hot safety function, without additional mechanical device, if the injector ignites. it is the heat of this internal combustion itself, in the air-gas duct before its outlet in the diffusion chamber which is used.
• FIG. 1 shows in longitudinal section a first example of a embodiment of a thermocouple arrangement according to the invention, in a burner pipe ar ⁇ vee bent air-gas
• thermocouple arrangement in a burner pipe ar ⁇ vee not bent air-gas
• FIG. 3 shows in longitudinal section a third exemplary embodiment of a thermocouple arrangement according to the invention, in a burner comprising a flat g ⁇ lle called "flame catch" at the outlet of the tube
• FIG. 4 shows in longitudinal section a fourth exemplary embodiment of a thermocouple arrangement according to the invention, in a burner with a bent air-gas inlet pipe
• ventun tube 2 an air-gas mixture inlet pipe, also called ventun tube 2.
• This ventun tube has at its inlet end
• a gas supply safety valve 8 which supplies a gas injector 9 fixed to the end of an injector holder tube 10.
• This assembly is of conventional type.
• the ventun tube 2 bent in the example described, before its outlet 7 in the diffusion chamber 5 has a positioning and guide plate 11 of the tip probe 3 at the end of bulb 4 of the thermocouple. On this positioning plate 1 1 is formed a light 12 in which is engaged the bulb 4 of the thermocouple. Once this plate has been crossed, the probe tip 3 abuts against the internal surface 13 of the plate constituting the wall of the diffusion chamber 5 This solution for securing the plate to the base of the air mixture tube gas is, in the present example a convenient solution
• this solution is not exclusive, and it may be advantageous in other configurations, to fix the plate, not to the tube, but at the level of the diffusion chamber itself, at its base of contact with the tube.
• the main thing is that the guiding function, positioning of the bulb and contact with the grid of the diffusion chamber is ensured, whatever the equivalent means.
• the guide and positioning plate is o ⁇ entee across the longitudinal movement of the air-gas flow so that its surface forms a deflector screen at the velocity of the flow at the outlet of the ventun tube. This creates a quieter mid-flow zone between the unexposed face of the plate 1 1 and the internal surface portion 13 of the wall of the diffusion chamber because it is sheltered under the plate.
• thermocouple probe tips This calmer flow, when it ignites on the external face of the g ⁇ lle of the diffusion chamber at the level of the mini-zone, ignites flush with the grid which then presents a small area of localized reddening of the metal of the grid, precisely around the point of contact of the probe tip with the grid. This is the goal sought to heat only the end of the hot solder of the probe tip without affecting the rest of the thermocouple by the effects harmful from too high a temperature
• the interposition of a g ⁇ lle between the probe tip (hot solder) and the combustion flame present also has the advantage of protecting this tip from dete ⁇ oration fa orized by the oxvdant character d open flame. The exenceence shows the importance of this factor on the loss of longevity of thermocouple probe tips
• the tubular section. concave inside, from the bent part of the tube (convex to the extender), is particularly suitable for automatic guidance of the probe tip Like the talweg line of an ⁇ gole.
• FIG. 2 shows how the insertion guide and positioning of the thermocouple by an adjacent sheath 18 can also be rigorously ensured, thanks to the "groove" effect of the interior of the tube, immediately upstream of its opening in the diffusion chamber
• FIG. 4 illustrates this possibility, the adjacent sheath 18 joining the tube 2 at the most appropriate point of said tube, the essential being
• thermocouple 1 It also con ies in the configuration shown in Figure 4 and as in the case of the non-bent tube of the configuration shown in Figure 2. to close around the outer conductor of the thermocouple 1 free end of the adjacent tou ⁇ eau 18 by a blocking and obturation element beyond this free end of the sleeve external conductor of the thermocouple is located outside the air-gas duct and joins the safety valve 8 to which it is conventionally connected.
• the "combustion" part of the p ⁇ s burner with reference to desc ⁇ ption with FIG. 1 finally comprises a combustion chamber 6 whose volume is delimited - by the external face of the wall of the diffusion chamber mentioned above, and
• thermocouple By the internal face of the external enclosure of said combustion chamber. It is in this space compns between these two walls that ignition and combustion of the air-gas mixture takes place at high temperature, the latter possibly reaching more or less 950 ° C. It will therefore be noted that the thermocouple is found well, as to him. entirely separated from this space or had combustion, since even its probe tip 3 is on the other side of the diffusion chamber
• This plate must have a surface area less than the cross section of the mini diffusion chamber to allow the fresh (and therefore not ignited) flow of the air-gas mixture to fill through this inlet the metered volume of said mini-chamber.
• thermocouple including in these other configurations a thermocouple of conventional constitution and to arrange it as follows a) side probe tip at the end of the bulb the socket 14 for securing the bulb 4 is used on its first millimeters of junction with the bulb as support bearing in the lumen 12 of the guide and positioning plate 1 1, the probe tip, at its hot weld 3. meets as an abutment and support point the internal wall of the diffusion chamber .
• a) side probe tip at the end of the bulb the socket 14 for securing the bulb 4 is used on its first millimeters of junction with the bulb as support bearing in the lumen 12 of the guide and positioning plate 1 1, the probe tip, at its hot weld 3. meets as an abutment and support point the internal wall of the diffusion chamber .
• the bulb-socket assembly of the thermocouple is wedged, naturally, by "wedge” effect, between its two support points, this wedging being favese by the obhcite of the conical wall of the diffusion chamber 5, in other configurations such as for example that of a cylmd ⁇ que diffusion chamber 20, the "wedge" effect of the bulb assembly- sleeve against the g ⁇ lle of the diffusion chamber is advantageously obtained, for example by a cyhndron-conical protuberance 21 on the sleeve 14, plumb upstream of the guide and positioning plate This protrusion 21, which can be a threaded ring in force on the sleeve, by resting on the internal wall of the v entun tube.
• thermocouple 1 in the appropriate position by pressing it against the gas injector tube 10,
• a reference projection 17, forming a stop prevents the conductor from engaging more deeply in the tube. It also serves as a positioning marker if this engagement is, on the contrary, insufficient.
• Ln interesting means of producing this sailhe-reference 17 consists in using a segment of heat-shrinkable sheath having the advantage of being easily threaded into the thermocouple before heating of retraction and of being ⁇ gorously positioned after this heating. It goes without saying that any other means giving an equivalent result can be used, particularly in the case of other configurations, the main thing being to ensure the systematic maintenance of the internal thermocouple in the adequate securing position.
• the device and the exposed arrangement means allow the use of a conventional thermocouple, by installing its downstream part, probe tip side, inside the duct. air-gas mixture supplied to the burner. Its upstream part, meanwhile, opens to the outside, either by the air-gas inlet end of the ventun elbow tube, or by an adjacent sheath joining said tube, whether straight or elbow, upstream of its outlet inside the diffusion chamber Thus are ensured at once, after connection of the thermocouple to the safety valve. cold safety and hot safety functions in "high temperature" burners
• thermocouple by getting rid of the temperature limit above which the material resistance of the thermocouple is no longer ensured.
• the reversal of temperature between the hot junction and cold junction of the thermocouple due to its echautfement has the intenor of the duct or the air mixture -saz entered combustion. The result is the rapid interruption of this igniting of the injector by collapse of the electromotive force resulting in the final closure of the gas supply to the safety valve.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Control Of Combustion (AREA)

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• 2000
  • 2000-07-11 FR FR0009014A patent/FR2807145B1/fr not_active Expired - Fee Related
• 2001
  • 2001-03-28 WO PCT/FR2001/000938 patent/WO2001075367A1/fr active IP Right Grant
  • 2001-03-28 ES ES01919588T patent/ES2230289T3/es not_active Expired - Lifetime
  • 2001-03-28 DE DE60106584T patent/DE60106584D1/de not_active Expired - Lifetime
  • 2001-03-28 US US10/220,056 patent/US6702458B2/en not_active Expired - Fee Related
  • 2001-03-28 EP EP01919588A patent/EP1269080B1/de not_active Expired - Lifetime

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