US2532740A - Fuel burner provided with combustion gas recirculating means - Google Patents

Description

Dec. 5, 1950 Filed Feb. 10, 1948 W. H. SPEER FUEL BURNER PROVIDED WITH COMBUSTION GAS RECIRCULATING MEANS 2 Sheets-Sheet l 41 5 /zr 19 c :1 IHHHHHHHHHI INVENTOR.

Dec. 5, 1950 w, sPEER $532,740

FUEL BURNER PROVIDED WITH COMBUSTION GAS RECIRCULATING MEANS Filed Feb. 10, 1948 2 Sheets-Sheet 2 INVENTOR. WE Swear Patented Dec. 5, 1950 FUEL BURNER PROVIDED WITH COMBUS- TION GAS RECIRCULATING MEANS William H. Speer, Moosup, Conn. v Application February 10, 1948, Serial No. 7,370

4 Claims.

This invention relates to heating apparatus and particularly to systems of combustion where mechanical firing of oil, gas or otherfuel receives air from a blower or other pressure source to support combustion. This is a continuationin-part of my prior application Number 585,111, filed March 27, 1945, now abandoned.

recirculation passages. 20. The liner n is adjusted longitudinally by sliding it in the re- The object of the invention is to provide for the combustion of a fluid fuel by control of jet and air supply formations and in particular by combining with the main air supply a recirculation of gases from the combustion chamber and the supply of these gases to the flame by syphonic action in the air supply. I

Further objects of the invention particularly in the construction of the combustion member to provide for this recirculation and admixture of gases will appear from the following description taken in connection with the following drawings in which Fig. 1 is a sectional view taken on the line ll of Fig. 2 and showing a typical combustion head with a periphera1 recirculation area around the central burner parts;

Fig. 2 is a front elevation of the apparatus shown in Fig. l; and

Fig. 3 is a view similar to Fig. 1 and illustrating a modification.

In the specific embodiment illustrated, the

burner head 5 is set in place in the furnace wall F and opens to the right into the combustion chamber C. The burner head comprises an inner cylindrical portion 8 and an outer ribbed portion I of annular form providing the air inlet 8 leading to the contracting wall 9 concentrating the air stream and delivering it through the opening l into the space within the head portion 6.

A liner member H has an air inlet l2 positioned to receive the air entering from the opening Hi, this liner being slidably supported coaxially within the head portion 8 by ribs IS.

The oil supply tube l leads to the nozzle [6 forming the spray jet l'l under pressure, which jet is surrounded by the air stream from openings l0, l2. Ignition terminals l8 are provided supported from the insulators I 9 at the outer portion of the head.

The liner II is surrounded by annular recircutaining ribs I3 and rod 24 engages lug 23 to provide for this adjustment from the outside of the apparatus. The front edge 25 of the liner is positioned near the base of the jet and preferably within theedge 26 of the burner 'head 5.

Preferably the nozzle I6. is of the atomizing type giving a jet mist of very finely divided particles. The air stream is ample in cross section with correspondingly moderate velocity completely surrounding each atom of oil and holding the particles in suspension. This together with the ignition gives control of the resulting flame and results in complete combustion within the high temperature of the flame generated gases within the high temperature refractory zone and until combustion is completed.

In the modification illustrated in Fig. 3 the body of the burner comprises a tubular member 36 sleeved on the inner end 31 of an outer housing member 38, the oil pipe 35 being located at the center and mounted to be longitudinally adjustable fromoutside the unit so as to position the nozzle 39 at the inner end of the burner as shown or a few inches forward or back of this position. The oil supply to this nozzle is under pressure, low or high, sufiicient to atomize the oil being. used into a spreading jet having an angle of spread of about or or of about 50 to where conditions make it preferable. The burner is thus of the gun type producing a spray jet by pressure and burning this jet by a supply of air to the jet as atomized and spread.

I have found it important to suspend or float this pressure formed jet in the combustion chamber by surrounding gases and to this end the' fresh air supply is brought longitudinally around the nozzle and is supplemented by a recirculation of gases drawn from the combustion chamber and preferably from the space S back of the floating flame as in the forms illustrated in the drawings.

In Fig. 3 this recirculation is provided by the annular members 40, 4|. The outer member 40 is press fitted or otherwise fastened in place in the inner end of tube 36 as shown so that the inturned end 42 of the insert will be at a slant across the path of the main air supply. The inner member 4| is of less diameter and is slid-- ingly centered and supported in thecylindrical end of member 40 by radial fins 44 carried either by the outer member 40 orthe inner member member 40 and having between them an inward directed passage 48. opening into the venturi formed by the contraction of the air flow by the conical flange 42. The suction of the flow through the venturi draws gases inward from passage 46 supplied from the annular entrance 41 between the members 40, 4| leading to the space S which intervenes between this passage and the base of the flame H. The width of the passage 48 may be varied by longitudinal adjustment of the member 4| for instance by the rod 48 leading to adjusting means accessible from outside of the burner and engaging the lug 49 projecting upward from the member 4|. The size of the intervening space S may be varied by longitudinal adjustment of the oil supply pipe 35 to shift nozzle 39 forward or back from the position shown.

This recirculation of gases from the space S around the jet l1 uses these gases to decrease the amount of fresh air supplied while at the same time maintaining an adequate volume of gas mixture to float the flame as well as maintain the combustion.

The result is a lowering of the excess air passing through the combustion chamber and an increase in the percentage of carbon dioxide in the flue gases. In the apparatus as illustrated in Fig. 3 the Venturi action is concentrated at or just back of the base of the flame.

Consequently the main air supply and the recirculated gases combine with the jet all around in the space S as the jet is projected from the burner holding the flame in suspension in the high temperature combustion chamber to complete the burning of the oil. Contact of the flame with surrounding surfaces of the burner is avoided altogether and there is ample separation preventing any coking or accumulation of deposits on the metal parts.

In the device shown the supply for the recirculation is drawn in through an annular area surrounding the space S and thus includes a large part of the unconsumed air and gases around the flame and not mixing therewith, the recirculation being remixed with the main air stream on its way to the flame. Increments of the unconsumed air are thus carried around in the recirculation circuit and the combustion is rendered more complete. The action automatically adjusts itself to the varying conditions in the furnace permitting a wide control of the flame while attaining eflicient conditions of combustion.

At the same time the recirculation of the accessory gases from the combustion chamber and its admixture with the incoming air aids in insuring efllcient overall combustion and adds to the control of the combustion gases in the burner and the combustion chamber. 1

By withdrawing and recirculating the gases from the combustion chamber, the pressure in the boiler is reduced. The draft requirements as ordinarily flgured are necessarily less and the release of products of combustion through the boiler is slowed down with consequent permissible restriction of the boiler passages and greater efliciency in their heat absorption.

The combustion itself is quieter due to the mufliing eflect of the recirculation, and the creation of a Venturi pressure area in the air stream tends to equalize the fan impulses. Good flring adjustment is not dependent upon higher draft setting and a lower more normalized draft pull may be employed and thus fluttering is obthrough the venturi 2|, 4'6 thus rat ng the temperature of the mixture. The air consumption is made more complete and the volume of new air to be supplied is correspondingly reduced, avoiding excess air and improving the overall eiflciency.

The particular adjustment of the liner 4| will depend upon the Venturi action desired and most eflicient in each individual case. The wider the venturi 2| the further the orifice I! will be spaced from the air jet orifice l0 and the narrower will be the air jet at the point of entry into the oriflce l2, so that the tendency will be to increase recirculation with widening of the Venturi neck by inward movement of the liner.

Normally the atomized fuel and the air mixture will float the flame a predetermined distance into the combustion chamber C and the recirculated gases will be drawn in through the annular area surrounding the base of the flame so that the flame near the burner head is encased in counter currents of the combustion gases.

The burner head may be supplied as an accessory or may be built into the equipment as originally installed. It is nonmechanical in operation. The fuel is burned at approximately atmospheric pressure due to the relief of pressure either directly in the combustion chamber or from some remote point, for instance adjacent the smoke pipe. The mixture is accomplished by the Venturi action which produces a partial vacuum at 20, 41 resulting in a mixture of the fresh and recirculated gases at 2|, 46 (Figs. 2 and 3). Theactual primary air for combustion is relatively reduced in amount due to the pick-up of gases from the combustion chamber or other source. The flame is' thus supported by the recirculated gases with a consequent saving in the primary air and greater efliciency in the overall burning of the fuel.

It also provides, for favorable expansion of the flame in a heating boiler permitting it to be distributed and supplied most advantageously to the surfaces to be heated. The only draft needed is from the breach to the chimney in order to vent the released products of combustion from the heat unit.

In the burner shown, the oil pressure line is at relatively high pressure but the air supply and recirculation is equally applicable to burners using a lower pressure oil supply in the neighborhood of five pounds for instance or less. The burner head of Figs. 1 and 2 is of simple forma- .tion involving merely the tubular casting 6, l-

and the liner- H with the rod 24 extending backward for accessible manipulation at the outside of the burner. The burner head of Fig. 3 involves in its structure a simple assembly of the recirculation rings 40, 4| at the inner end of the tubular member 36. These typical embodiments illustrate the operation and advantages of this system of recirculation, but the invention is not limited to the specific details shown. It is intended to cover such modifications as fall within the scope of the appended claims.

I claim:

1. A fuel burner adapted to project a flame into the combustion chamber of a furnace comprising a forward member having an outer wall adapted to fit into the furnace wall and formed with a nozzle chamber and with a rear air supply opening, a fuel nozzle at the forward portion of said chamber adapted to atomize a liquid fuel supply and direct the atomized jet into the combustion chamber, a rear conduit providing a fresh air supply flowing through said opening forward into the rear air supply opening of said nozzle chamber, an inward directed wall member around said rear air supply opening, and a liner spaced from said outer wall surrounding said fuel nozzle to provide a passage and having a rear wall cooperating with said inward directed wall to form an inward directed passage opening into said air supply at the rear of said nozzle chamber to feed auxiliary gases into said air supply on the way to said nozzle, said passage leading from the combustion chamber to said inward directed passage for withdrawing gases from said chamber and leading said withdrawn gases into said inward directed passage for blending with the said air flow on its way to the nozzle.

2. A fuel burner as set forth in claim 1 in which the conduit for the fresh air is tapered to a contraction forming a Venturi passage into which the inwardly directed passage opens at the rear wardly open end and an air supply portion rearwardly thereof, aliner slidingly mounted in said head portion, a fuel supply means having a nozzle positioned in the forward portion of said head, a contraction of said air supply portion forming a Venturi passage directing the air flow into said head portion, said liner and head portion being spaced to form passages between them for supplying gases to said Venturi passage, and means for relatively adjusting said liner and said casing to vary the cross sectional areas of said passages and correspondingly vary the induction or Venturi effect of the air flow into said head portion and the relative proportions of the fresh air and auxiliary gases.

WILLIAM H. SPEER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'IE'NTS

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