MXPA97010309A - Ignition and detection of flame in a degas combusti burner - Google Patents

Abstract

The present invention relates to a system and method for igniting the gaseous fuel mixture and air flowing from the flame generating orifices in a burner tube having a plate welded on the side of the tube and extending from the tube very close to one of the holes that generate the flame. The plate has a free exhaust or opening that forms a plenum that reduces the flow velocity and the plate is electrically grounded. A spark electrode has an end disposed in the opening and when a high voltage potential is applied to the electrode, a spark is discharged into the opening and the mixture in the plenum ignites and a portion of the resulting flame is retained in the opening of the plenum for detecting the presence of the flame by rectifying the current

Description

IGNITION AND FLAME DETECTION IN A COMBUSTIBLE GAS BURNER BACKGROUND OF THE INVENTION The present invention relates to the ignition of a mixture of fuel gas and air in a burner, such as is used in an oven and is particularly applicable to ignite such mixture in a domestic cooking oven, especially of the type produced in large quantities for home kitchens. Up to now, the ignition of the fuel gas and air mixture in the burners for ovens was generally carried out in one of two ways: a) by providing an incandescent ignition surface adjacent to the gas outlet in the burner, thus allowing that the mixture of fuel gas and air collides against the glowing surface whose temperature is increased to the ignition temperature in order to obtain the flame, and b) providing a discharge spark of high voltage discharged in the path of the gas mixture fuel and air flowing from the burner opening. The mode of ignition of the mixture of fuel gas and air by the discharge of a spark has had a widespread application due to the relatively low manufacturing cost and the ease of installation in the furnace of its components, as well as for the minimum space that it is required for such ignition by discharge of sparks in the burner region. However, there were problems with the ignition by a spark igniter of a mixture of fuel gas and air flowing from an outlet of the burner due to the high speed of the mixture discharging from the burner orifice and the erosion the spark causes the single-ended electrode during spark ignition. Difficulties arose in the alignment of the electrode both in its manufacture and in maintaining it during its useful life, which caused irregular and unreliable ignitions. The holes generating the flame should be kept at a minimum size to avoid the formation of too large and difficult to regulate flames, which tend to be of rich combustion generated by soot-like hydrocarbons in the furnace. For this reason, the holes generating the flame are designed with a relatively small diameter and this causes a relatively high velocity of the fuel gas-air mixture discharged by the orifice. The relatively high velocity of the mixture discharged through the orifice makes it rather difficult to place the spark igniter in a correct location to ignite the flame as the mixture is discharged through the orifice when the flow regulating valve is opened from the burner. It has long been desired to provide a way or means to improve the initiation of the flame in the burner discharge orifice with the use of a spark igniter type igniter, and to provide such an improvement without increasing the cost of the manufacture of lighter components. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved igniter of the spark discharge type for igniting a mixture of fuel gas and air leaving the burner orifice. It is another object of the present invention to provide a spark igniter type igniter system to ignite the fuel gas flowing from a hole in the burner and to provide such a system with a multiple sparks exit electrode, which are equidistant from the electrode with high voltage potential. It is yet another object of the present invention to provide detection of the presence of the flame by rectifying the current. The present invention provides a plenum, adjacent to the discharge orifice of the burner, and an electrode disposed in the plenum for the provision thereto of a spark discharge to ignite the mixture of combustion gas and air leaving the burner orifice. . In the preferred embodiment, the plenum chamber is formed as a free outlet or opening in an impeller member fixed to the burner and the periphery of the plenum provides a plurality of spark discharge points, all equidistant from an electrode centrally disposed with respect to the opening. In one embodiment the opening is formed substantially at right angles to the direction of flow from the burner orifice. In another embodiment, the plenum opening is arranged in a plate substantially parallel with the surface of the burner orifice, which generates the flame. A portion of the burner orifice stream is trapped in the plenum and the velocity is reduced so much that when the spark is discharged the fuel gas-air mixture is easily ionized and ignited by the spark discharge. After ignition, the impeller opening surrounding the tip of the electrode tends to direct and retain the flame around the electrode and reinforce rectification of the current to detect the presence of the flame. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates, in axonometric projection, a part of the fuel burner tube with the impeller opening arranged at right angles to the flow from the generatrix openings of the flame. Figure 2 is a side elevational view of the front of another preferred embodiment of the invention having the plenum opening in a plate parallel with the surface of the orifice that generates the flame.

Figure 3 is an enlarged scale view of the circumscribed part of Figure 2; Figure 4 is a top view, or plan view, of the right end portion of Figure 2, and Figure 5 is a sectional view taken along the section indicated by lines 5-5 of Figure 3. Detailed Description of the Invention With reference to Figure 1, an embodiment of the ignition system is generally indicated 10 and includes a burner tube 12, such as the furnace burner, the hollow interior of which is shaped to receive a quantity of mixture of fuel-air gas from a source (not shown), which enters the burner tube 12 from the direction indicated by the black arrow. A plurality of flame generating orifices, identified by the reference numbers 14, 16, 18 are provided in a substantially spaced relation along a side wall of the burner tube 12, which has, in the illustrated embodiment, a section transverse substantially rectangular or square. However, it will be understood that the burner orifice may have any suitable configuration such as, for example, a circular or oval cross section. The burner tube, in the illustrated embodiment, has a seamless configuration, but can also be fabricated by joining two semi-shells with soldering iron, for example.

A plenum forming member, in the form of a plate 20, has one of its sides fixed to the wall 22 of the burner, and is disposed very close to it but spaced to the hole 18 of the burner. The forming plate of the impellent enclosure 20 has formed a free-flowing exhaust 24 which has a notch 26 disposed on one of its sides, which notch 26 extends to the burner wall 22, so that a part of the mixture gaseous-air fuel that emanates or flows from the orifice 18 moves through the slot towards the plenum 24. In the present embodiment of the invention, the free exhaust 24 has a substantially circular configuration, and the plate 20 is welded to the burner wall so as to extend therefrom substantially in a right angle configuration. This arrangement serves to trap at least part of the fuel-air mixture that flows from the generating hole of the flame 18 and to reduce its speed. An electrode 28 is disposed adjacent the free exhaust 24 and preferably has its end 30 disposed centrally within the circular free exhaust 24 so that the periphery of the free exhaust is equidistant from the end 30 of the electrode. The remote or remote end of the electrode, identified with the reference number 32, is connected to a source of electric potential of relatively high voltage with respect to the plate 20, which, in the present embodiment of the invention, is connected to ground .

It will be understood that upon initiation of the flow of the gaseous-air fuel mixture into the burner gap 12, the mixture flows at an increased rate through the orifices 14, 16, 18, with the flow from the orifice 18 entering the notch 26. and the circular opening 24 where the speed is reduced. When a regulator (not shown) acts on the oven user, a high voltage (+ v) is applied to the electrode 28 and an arc or a spark is discharged from the end 30 of the electrode to the periphery of the free exhaust 24 and ignition occurs and the flame is generated in the hole 18. It will be understood that the plate can be located between the holes 16 and 18 so that the flame will start practically simultaneously in the holes 16 and 18. With reference now to Figures 2 to 5 , another embodiment of the system is illustrated, with general indication 40, which includes a burner tube 42 with a plurality of flame generating orifices 44 and an aspirator for air intake, indicated generally at 46, which is provided in FIG. an end 48 of the tube formed at right angles to the tube 42. A support member for mounting the burner, identified in general with the reference number 50, has one of its part, indicated by the reference number 52, configured to fit over the outer surface of the tube 42 and is fixed thereon with any suitable resource such as, for example , a welding. The support member for arming the burner 50 includes flange 54 for arming the burner tube inside the furnace. A support bracket 54 for the lighter is fixed to the support member 50 with any suitable resource, such as, for example, welding or riveting a flange portion 56 welded to the plate 58 which comprises a part of the support member of the burner tube 50. A portion of the lighter bracket 54, remote from the flange 56, is shaped to have a substantially circular configuration, such as is identified with the reference number 57 and in which an ignition probe is housed 60 firmly embraced in it and held in a predetermined position. The probe 60 has an electrode 62 extending from its end, which electrode is formed substantially bent at right angles to have one end 64 thereof disposed, preferably centrally, within the opening 66 formed in the plate 58, disposed and positioned so that the opening 66 is in a position above at least one of the holes 44 generating the burner flame and spaced therefrom at a predetermined distance by a flange 68 formed in the plate 58. , when the fuel valve (not shown) is opened, fuel enters the aspirator 46 and a mixture of gaseous fuel and air flows in the tube 42 and is discharged through the orifices 44 and a part of it is retained in the container. Free Exhaust Enclosure 66. When a spark is discharged by the end of the lighter 64 towards the multiple points around the circular free escape periphery or opening 66, the mixture is ignited and the flame is retains in the opening 66. The flame retained in the opening 66 is used to rectify a current flowing from the end of the electrode 64 to the opening 66, which rectification can be detected by suitable circuitry (not illustrated) of a As is well known in the art and in such a way the ignition arrangement provides an inherent ability for the detection of the flame to the ignition system of the present invention. It will be understood that, although a circular configuration of the opening 66 is preferred to provide an increased area for spark discharge, equidistant from the end of the electrode 64, other configurations for the opening 66 may be used, such as, for example, oval, elliptical, elongated slots, or a free open U escape. The present invention provides an improved ignition system of the spark discharge type for igniting the fuel gas mixture and air flowing from the burner orifices and is particularly applicable in burner tubes of the type used in domestic kitchen ovens. The present invention provides a multiple discharge of the sparks at a plurality of surface points by placing the spark electrode in a free opening or exhaust that serves to retain the flame when the fuel-air mixture has been ignited from the generator orifice. the flame. The flame retained in the free exhaust or the opening is then used to rectify the flow of the detector current, whose rectification is detected to check the presence of the flame. Although the present invention has been described herein with respect to the illustrated embodiments, it will be understood that the invention is apt to be modified and varied and that it is limited only by the claims that follow.

Claims (7)

1. CLAIMS 1. An ignition system for a gaseous fuel burner, comprising: a) a burner member connected to receive a mixture flow of fuel gas and air and which is provided with at least one orifice generating the flame; b) a support structure with said burner adjacent to said at least one hole, said support having a free escape separated from said orifice by a relatively small space, and c) an electrode disposed in said free escape and defining a clearance of air between them, substantially surrounding said free escape to said electrode, in which, after the application of a high voltage potential to said electrode, a spark is discharged to said free exhaust to effect the ignition of said gaseous fuel leaving said at least one hole, wherein said flame is retained in said free exhaust and causes the rectification of a sensing current, which rectification can be detected as proof of the presence of the flame.
2. 2. The ignition system defined in claim 1, wherein said free exhaust has the substantially circular configuration.
3. 3. The ignition system defined in claim 1, wherein said burner has a tubular configuration and said support structure comprises a plate fixed on the wall of said tubular burner.
4. 4. A method for igniting a mixture of gaseous fuel and air flowing from a burner orifice and comprising: a) providing a hollow burner having at least one orifice generating the flame and flowing a gaseous fuel mixture and air through said hole; b) arranging an impellent member adjacent to said orifice and forming a free exhaust in said member; c) arranging an electrode in said free escape and defining an air gap between them; d) applying a relatively high voltage potential to said electrode with respect to said impeller member and discharging a spark therebetween and igniting said mixture of fuel gas and air, and e) retaining at least a part of the flame in said free exhaust for detect the flame by rectification of the current. The method defined in claim 4, wherein said disposition step includes fixing said impeller member to said burner. The method defined in claim 4, wherein said disposition step includes providing a plate and said step of forming a free escape includes the formation of a substantially circular opening in said plate. The method defined in claim 4, wherein said step of forming a free escape includes the formation of a substantially circular opening and said step of disposing an electrode includes placing the end of said electrode centrally in said circular opening.