US3718321A - Combined burner, fan and igniter - Google Patents

Abstract

A combination burner, fan and igniter for an air heating device for use in a grain dryer or the like which combination takes cognizance of the non-uniform distribution of air from the fan around the burner to locate the igniter where it will be subject to the least heat from the burner. As a result, the life of the igniter is increased from approximately two weeks to a year or more.

Description

United States Patent Alms 1 1 Feb. 27, 1973 [54] COMBINED BURNER, FAN AND 3,301,308 l/l967 Briggs ...263/19 A IGNITER 3,401,920 9/1968 Berkhoudt et a1. ..263/|9 A [76] Inventor: E. Alms, Barrmgton, Ill. Primary ExamineF-Edward G Favors AttorneyCharles F. Voytech [22] Filed: Jan. 17, 1972 [21] App]. No.: 218,450 [57] ABSTRACT Related s Application Data A combination burner, fan and igniter for an air heating device for use in a grain dryer or the like which [63] 58 121 21 25 of June I970 combination takes cognizance of the non-uniform distribution of air from the fan around the burner to 521 US. c1..... ..263/19 A, 431/263 locate the ignite where h will be Subject to the least 51 1m. (:1 ..F23l 9/04 heat from the burner- AS a result, the life of the igniter 58 Field of Search ..263/19 A; 431/263 is increased from approximately two weeks to a y OI more.

[56] References Cited UNITED STATES PATENTS 6 Claims, 4 Drawing Figures 3,109,481 11/1963 Yahnke ..263/l9 A 1 a 0 00 H /5 0:0 25 K i e 24 o /9 27 2 '1" 0/ g 6 WEE o ojo o o o o o o o o o o o 0541] fl rxrsy 0 Li L- 2 28 1 O po '1 34 o o ck o W 3 *%ZJ 0 O O O o o o 20 0 0 0 0 3 23 O l O O I 76 4 O I W o PATENTEU FEBET 3 5 N VEN TOR Erhard E Alms COMBINED BURNER, FAN AND IGNITER This is a continuation of application Ser. No. 50,687, filed June 29, 1970, now abandoned.

This invention relates to igniters for high capacity gas burners which are operated in a fan-driven stream of air. The invention will be described with reference to its application to gas burners used to supply hot air to grain dryers, although it is not limited to such application.

Certain devices such as dryers for grain and the like require large quantities of hot air for removing moisture rapidly and uniformly from the grain. The hot air is supplied from furnaces forming part of the dryers, the furnaces using gas as fuel, the burning gas discharging directly into a plenum chamber in the dryer. A safe temperature is maintained in the plenum chamber by mixing external air with the products of combustion from the gas. Both the air for combustion and the air for assuring correct temperature in the plenum chamber is obtained from a single high capacity fan, generally of the radial blade propeller type.

It is characteristic of radial blade propeller fans that the air stream issuing therefrom has both a helical movement and a radial movement as well as the intended axial movement. In the furnaces used with grain dryers, the general shape of the furnace is cylindrical and the fan and the motor are mounted at the input end of the furnace ahead of the gas burner. A convenient mounting for the motor comprises a horizontal plate which extends across the lower portion of the furnace in the air stream from the fan. The burner may be a T- shaped unit which is mounted in the airstream adjacent the plate.

The operation of the burner is an on and off" operation during the drying cycle, which requires the use of an electric spark to ignite the burner. The electric spark is generated by an electrical igniter or spark plug located adjacent the burner, the spark plug being of well known internal combustion engine design incorporating a pair of electrodes across which a spark is created when ignition is desired. Thus, the igniter is subject to the heat from the main burner whenever the latter is operative.

It has been found that the igniter in the burner for a dryer has a very short life, on the order of two or three weeks, the heat of the burner destroying the electrodes and requiring a frequent replacement of the igniter in which the electrodes are contained. It is accordingly an object of this invention to provide a design of burner and igniter for use in an airstream for a furnace by which the life of the igniter is increased from a life of approximately two weeks, to a life of one or more years.

A more specific object of this invention is to provide a design of burner and igniter wherein the life of the igniter is materially increased without requiring the use of a special igniter, nor necessitating a major redesign of the burner or furnace.

These and other objects of this invention will become apparent from the following detailed description of a preferred embodiment of the invention when taken together with the accompanying drawings in which:

FIG. 1 is an end elevational view ofa cylindrical furnace incorporated this invention looking toward the input end;

FIG. 2 is a fragmentary side elevation in section of the furnace of FIG. 1, the section being taken along line 22 of FIG. 1;

FIG. 3 is an enlarged front elevational view at the burner of FIG. 1; and 1 FIG. 4 is an enlarged side elevational view of the burner of FIG. 1 showing the location of the igniter.

The present invention is based upon a study of the conditions existing in a furnace of the type used with dryers, and particularly of the effect of the air-stream on the distribution of the flame across the burner. It was noted that although such furnace is cylindrical and the burner is centrally located in the furnace, the flow of air across the burner is not uniform at all points on the periphery of the burner, despite the normal symmetrical design of a radial blade fan and its electrical drive motor. It was further noted that necessary obstructions in the airstream between the fan and burner, such as the platform on which the fan motor is mounted, had an especially marked influence on the airstream and created an unsymmetrical flame in the burner relative to the burner structure. Thus, where there was no obstruction, the air velocity was at a maximum, and where there was the greatest obstruction, the air velocity was at a minimum. This created a pressure differential across the burner which shifted the flame to the low pressure side of the burner and created at this location an area of maximum temperature. I

For many years burner manufacturers have been unaware of the pressure differential created across their burners and have adopted as a standard design an arbitrary location of the igniter which, when the burner was used with dryers of the type herein described, was on the low pressure side of the burner and hence at the point of maximum heat produced by the burner. According to the present invention, the igniter is located in the area of greatest air pressure at the burner consistent with good operation of the igniter, which corresponds to the point at which the temperature is the lowest. It has been found that in the dryer in which the burner of this invention is installed, the igniter should be located on the opposite side of the burner from that selected by the manufacturer and slightly farther forward of the burner fuel gas openings. When the igniter is so located, its life has been found to increase from a life of two weeks to a life of 1 year or more.

The fan, burner and igniter combination illustrative of this invention are shown in FIGS. 1 and 2. This combination is particularly well adapted for use with grain dryers of the type shown in A. Andersen, .Ir., US. Pat. No. 3,056,214, dated Oct. 2, I962. The combination comprises the furnace section of the dryer wherein the hot air is generated for use in the drying operation performed by the dryer. Thus, a substantially cylindrical furnace wall 10 is provided, said furnace wall being attached to a front wall (not shown) of the dryer in a horizontal position. Said furnace section is provided with a gas burner, shown generally at 11, and a fan 12 of the radial propeller type located at the input end of the furnace wall 10. A guard 14 of any suitable mesh or grid construction is placed over open end 13 to protect the operator or other nearby individual from possible injury by the fan, and also to prevent the ingress of large foreign material into the furnace section.

Fan 12 is driven by an electric motor 15 mounted on a horizontal platform 16 appropriately secured to the wall of the furnace section. Said platform may be a sheet of steel of sufficient rigidity to effectively resist deformation under the weight of motor as well as the torque produced thereby during operation of the fan.

Gas burner 11, in the form chosen to illustrate this invention, is of T-shape (FIG.3) which includes a horizontal section 17 and a vertical section 18. A hollow T-shaped casting 19 with openings 20 therein serves to distribute gaseous fuel such as natural gas or propane through the burner, and sheet metal shields 21, 22, and 23 are disposed on the sides of the casting l9 and positioned to diverge from the casting to protect the burning gas issuing from openings 20 from the air blast created by fan 12, said shields being perforated as at 24 to permit some of the air from the fan to mix with the gaseous fuel to promote the combustion thereof.

Shields 21 and 22 on the one side, and 21 and 23 on the other, are secured to end plates 25 and 26 which are appropriately secured to the ends of the T-shaped casting and serve to hold the shields in place. The burner 11 is secured to the furnace wall 10 by any suitable means (not shown).

Burner 11 is provided with an igniter 27, said igniter comprising a commercially available spark plug such as is used in internal combustion engines. The spark plug is appropriately mounted in an opening 31 (FIG. 4) in end plate 25. I

At the beginning of a grain drying run, igniter 27, through appropriate controls (not shown), ignites the main burner 11. Included in the said appropriate controls are the controls for starting fan motor 15 to drive the propeller fan 12. With burner 1 l ignited and fan 12 rotating, air is drawn from the outside atmosphere into cylindrical furnace wall 10 where it is given both a helical and radial movement by the radially disposed blades of the fan 12. In moving from fan 12 to burner 11, the air strikes the upper surface of the horizontal platform 16 on which motor 15 is mounted and is deflected upward toward the igniter unit 27. The deflected air is combined with air moving normally in a helical downward path above the deflected air so that there is an excess of pressure exerted upon the lefthand side of the burner, as viewed in FIGS. 1 and 3, over that which would normally be expected. With the air continuing to move in a counter-clockwise direction as viewed in FIG. 1, that air which strikes the bottom of the platform 16 on the righthand side thereof as viewed in FIG. 1 is deflected downwardly, rather than upwardly, so that above platform 16 on the righthand side as viewed in FIG. 1, there is less pressure created by the fan than would normally be expected. 4

Thus, there is a pressure differential created across burner 11 from left to right as viewed in FIG. 1, with the pressure on the lefthand side higher than that on the righthand side. This blows the flame and the products of combustion to the right as viewed in FIG. 3 so that in an area such as that defined by the dotted line 32 in FIG. 3, the temperature is the highest, and in an area such as that defined by dotted line 33 wherein the pressure is the greatest, that is to say the greatest amount of air is moving thereacross, the temperature is the lowest.

In the standard construction used by manufacturers of burners, however, the igniter was located in end plate 26 as shown in dotted line at 34. It is apparent that the location on end plate 26 placed the igniter in the area of the highest temperature and accordingly, the igniter electrodes 28 were subjected to a very high temperature whenever the burner was functioning. This temperature was higher than was desirable for the material of the electrodes, and hence the electrodes burned off in approximately two weeks of normal operation of the dryer. According to this invention, however, the perimeter of the burner 11 is tested to determine the location of the region of highest velocity of air from the fan 12, and the igniter is then placed at that location. Thus, in the furnace illustrated herein, the igniteris located in end plate 25 in the region of highest pressure and lowest temperature 33.

A determination of the position of greatest air flow is not dependent solely upon differences in air velocity around the perimeter of the burner but is also dependent upon the flow of air through the openings 24 in the shields 21, 22 and 23, the latter giving the air a component of movement inward and forward, as shown in FIG. 4. The fore-and-aft location of the igniter previously selected by burner manufacturers is shown in dotted outline at 35', said old location being closer to the openings 20 in the T-shaped casting 19 than the location selected in accordance with this invention. It

may be noted from the arrows indicating the flow of air through the openings 24 in the shields that the air flow is greater at the present location than at the old location, and hence the old fore-and-aft location is in a hotter area than in the new location.

Thus by determining the region at the burner at which the air flow is the maximum, the coolest location in the burner can be found, and when utilized as a location for the igniter, the latter can be made to last over a year, that is, for one or more seasons of drying crops, instead of for only two weeks in a single drying season. The longer life of the igniter not only decreases the maintenance expense of a crop dryer insofar as replacing the burned out igniters is concerned, but also saves down time on the dryer itself and hence permits longer periods of continuous operation of the dryer without stopping for repairs.

I claim: g

1. In combination, a tubular furnace, a gas burner in the furnace forsupplying heat thereto, a fan in the furnace for moving air toward said burner, means in the furnace intermediate the burner and fan modifying the flow of air from said fan to said burner to produce a pressure differential across the burner, and an igniter fixedly disposed adjacent the gas burnersubstantially in the region of the highest pressure thereacross.

2. The combination described in claim 1, said fan being of the radial propeller type and imparting a helical movement to said air, and said means comprising a substantially flat plate disposed in the helically moving air.

3. The combination described in claim 1, said means comprising a motor for driving the fan, and a flat plate extending across said furnace and supporting said motor.

4. The combination described in claim 1, said burner comprising a central conduit for the gas having orifices for the gas, perforated shields diverging from said conduit, said pressure differential across the burner being oriented relative to the burner to produce a region of high pressure at one end of the conduit and a region of low pressure at the other end of the conduit, and an end plate at the region of high pressure and securing the diverging shields to said conduit, said igniter being supported on said end plates.

5. The combination described in claim 4, said fan being of the radial propeller type and imparting a helical movement to said air, and said means comprising a motor for driving the fan and a substantially flat plate extending across said furnace and supporting said motor.

6. The combination described in claim 1, said burner comprising a central T-shaped conduit for the gas having orifices for the gas, perforated shields diverging from the cross bar and tail of the T-shaped conduit, said pressure differential across the burner being oriented relative to the burner to produce a region of high pressure at one end of the cross bar of the T- shaped conduit and a region of low pressure at the other end of the said cross bar, and an end plate at the region of high pressure and securing the diverging shields to said cross bar, said end plate having an opening symmetrically disposed with respect to the shields, said igniter extending through said opening.

Claims (6)

1. In combination, a tubular furnace, a gas burner in the furnace for supplying heat thereto, a fan in the furnace for moving air toward said burner, means in the furnace intermediate the burner and fan modifying the flow of air from said fan to said burner to produce a pressure differential across the burner, and an igniter fixedly disposed adjacent the gas burner substantially in the region of the highest pressure thereacross.

2. The combination described in claim 1, said fan being of the radial propeller type and imparting a helical movement to said air, and said means comprising a substantially flat plate disposed in the helically moving air.

3. The combination described in claim 1, said means comprising a motor for driving the fan, and a flat plate extending across said furnace and supporting said motor.

4. The combination described in claim 1, said burner comprising a central conduit for the gas having orifices for the gas, perforated shields diverging from said conduit, said pressure differential across the burner being oriented relative to the burner to produce a region of high pressure at one end of the conduit and a region of low pressure at the other end of the conduit, and an end plate at the region of high pressure and securing the diverging shields to said conduit, said igniter being supported on said end plates.

5. The combination described in claim 4, said fan being of the radial propeller type and imparting a helical movement to said air, and said means comprising a motor for driving the fan and a substantially flat plate extending across said furnace and supporting said motor.

6. The combination described in claim 1, said burner comprising a central T-shaped conduit for the gas having orifices for the gas, perforated shields diverging from the cross bar and tail of the T-shaped conduit, said pressure differential across the burner being oriented relative to the burner to produce a region of high pressure at one end of the cross bar of the T-shaped conduit and a region of low pressure at the other end of the said cross bar, and an end plate at the region of high pressure and securing the diverging shields to said cross bar, said end plate having an opening symmetrically disposed with respect to the shields, said igniter extending through said opening.

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