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US3685946A - Combustion chamber supplemental air supply assembly and method - Google Patents

Combustion chamber supplemental air supply assembly and method Download PDF

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US3685946A
US3685946A US88819A US3685946DA US3685946A US 3685946 A US3685946 A US 3685946A US 88819 A US88819 A US 88819A US 3685946D A US3685946D A US 3685946DA US 3685946 A US3685946 A US 3685946A
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air
combustion chamber
assembly
recited
flame envelope
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US88819A
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Jack C Adams
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ECOLOGICAL CONTROLS Inc
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ECOLOGICAL CONTROLS Inc
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C7/00—Combustion apparatus characterised by arrangements for air supply
    • F23C7/02—Disposition of air supply not passing through burner
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

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  • ABSTRACT A supplemental air supply assembly and method for transporting and directionally orienting high pressure air impingement on a flame envelope within a combustion chamber. Ambient air is introduced into a fan connected to a conduit which forces inlet air into the combustion chamber. The inlet air is positioned to oppose the flame envelope and is vortexed by a series of angled vanes fastened to the conduit. The air is preheated within an elongated sleeve prior to interaction with the flame envelope. The amount of high pressure inlet air introduced into the chamber is regulated.
  • This invention relates to the fieldof air supply units for combustion chambers.
  • this invention pertains to an assembly and method of introducing supplemental air into a combustion chamber which is directionally oriented and has a particular streamline contour with respect to a flame envelope.
  • a supplemental air supply assembly and method for increasing fuel combustion efficiency within a combustion chamber includes a fuel burner which forms a flame envelope having both a longitudinal and transverse dimension.
  • the assembly comprises an air inlet device which extends through the wall of the combustion chamber. The air inlet device obtains ambient air external to the combustion chamber and produces a streamline contour air flow which is both opposed to the longitudinal dimension and forced in the transverse dimension of the flame envelope.
  • FIG. 1 is an elevational view of the supplemental air supply assembly
  • FIG. 2 is a perspective view of the elbow sectional element of the assembly showing the vortexing vanes
  • FIG. 3 is a cross-section view of the elbow sectional element taken along the section line 3-3 of FIG. 2;
  • FIG. 4 is a cross-section view of the invention installed in a furnace operation
  • FIG. 5 is a cross-section view of an embodiment of 0 DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • a supplemental air supply assembly or air system 10 to increase the fuel combustion efficiency of furnace 12.
  • Fuel burner 16 extends through furnace side wall 18 into combustion chamber 14 from the external environment.
  • a controlled fuel/air mixture is provided to burner 16 to produce flame front 20 after ignition, which in turn promotes a regulated heat source within chamber 14.
  • Flame front 20 forms a flame envelope having both a longitudinal 13 and transverse dimension 15 as shown in FIG. 4.
  • system 10 operates functionally to introduce a preheated air flow supply into chamber 14 being both vortexed and countercurrent to flame front 20.
  • the quantity of air inserted into furnace 12 is controlled to match the unburned gases and heavy carbon which wraps these compounds into the core of the flame to produce a higher flame temperature within a.
  • system 10 produces increased flame temperatures, as well as an increase in fuel efficiency through the release of greater radiant heat transfer energy which is proportional to the fourth power of the flame temperature produced.
  • Supplemental air supply assembly 10 comprises four major systems including fan or blower 24, damping device 34, conduit 28, and preheating air supply ceramic sleeve 54. Assembly 10 is fixedly located adjacent to furnace 12 to provide an air supply from the external ambient environment. Furnace wall 22 includes an opening passing therethrough and inlet airunder pressure may be incorporated into chamber 14 through conduit passage 40 longitudinally 13 opposing and impinging on flame front 20.
  • Fan or blower 24 has an inlet opening located external to furnace 12 to intake ambient air and an outlet passage coaxially positioned with respect to conduit 28 to provide a conduit pathway through which the high pressure air may be transferred.
  • Fan 24 may be of the standard centrifugal type whose selection is based on the empiracally derived necessary quantity of air determined for a specific furnace 12 application.
  • blower 24 mayconsist of a squirrel cage series of vanes or blades mounted on the rim of a wheel. The vanes are generally slanted forward in the direction of rotation of the wheel in such a manner as to provide a maximum discharge of air. It has been empiracally shown that up to 20 percent of the air input at fuel burner 16 must be accommodated byfan 24 in order to obtain maximum bunting efficiency within chamber 14. Selection of proper fans or blowers 24 may be made from a standardized grouping of high pressure air devices well.
  • Fan 24 is operated by motor 26 which may be wired to a potentiometer at the head end of furnace 12 in conjunction with burner 16 which then governs the fuel/air mixture being input to chamber 14. Therefore, ambient air intake of fan 24 is exhausted under pressure throughconduit 28' and enters furnace 12 through wall 22 as a function of the amount required to maximize fuel combustion efliciency of burner 16.
  • Damping device 34 may be one of a standard set of assemblies which restrict conduit passage 40 as a function of the amount of inlet air required within chamber 14.
  • Damping motor 30 operates linkage 32 external to conduit 28 and passes internal to conduit 28 to adjust an air shutter placed within passage 40. In this manner, the air shutter is angularly rotated within passage 40 to regulate the cross-sectional area of conduit passage 40 and supply the necessary quantity of air.
  • Automatic operation of device 34 may be maintained through a conventional thermostat connected to motor 30.
  • a thermostat may be connected to a temperature sensing device, such as a thermistor or thermocouple, which measures the temperature of the incoming inlet air within chamber 14.
  • Device 34 may then be operated automatically through motor 30 as a function of inlet air temperature.
  • Conduit 28 comprises upper conduit member 38 and elbow section 36 rigidly secured to each other to form a continuous conduit passage 40 terminating on opposing ends at damping device 34 and furnace wall 22.
  • conduit 28 provides a path for the high pressure inlet air from fan 24 or damping device 34 into combustion chamber 14.
  • Elbow section 36 of conduit 28 is fastened on opposing ends thereof to upper conduit member 38 and furnace wall 22 forming a constant diameter conduit passage 40 therebetween.
  • Section 36 forms a bend providing a normal vector air outlet to that of the incoming air from upper conduit member 38. This 90 degree bend provides for a tube or peepsight 46 to be incorporated into system 10, but is not necessary for operation.
  • elbow section 36 Rigid attachment of elbow section 36 to upper conduit member 38 and furnace wall 22 is made through elbow flange 42 and wall flange 44 respectively. Flange attachments may be by bolting, welding or some other means not important to the invention. In this manner ambient air input to fan 24, as shown in FIG. 4, may be transported under a high pressure through upper conduit member 38, elbow section 36 and through an opening in furnace wall 22 into combustion chamber 14 longitudinally opposing or counter-current to flame front 20.
  • Section 36 as depicted in FIGS. 2 and 3 includes a tube or peepsight 46 extending in longitudinal direction 13 through an outer wall of elbow 36 and into conduit passage 40 centrally terminating adjacent to furnace wall 22.
  • Tube 46 is fastened to the outer wall of section 36 by weld 45 or by bolting.
  • Tube passage 48 extending through peepsight 46 provides for visual observation of flame front to an observer located external to furnace l2. Passage 48 is covered on tube external end 49 by a disc of high temperature transparent glass 50 to protect the observer.
  • Tube end 47 of peepsight 46 includes a plurality of vanes 52 rigidly secured to the outer diameter of tube 46 and extending radially to the inner diameter wall of elbow section 36. Vanes 52 are angled with respect to longitudinal direction 13 to provide a vortex motion for the incoming inlet air. In this manner, inlet air which has been given a longitudinal flow contour velocity is now brought into chamber 14 having a combined motion.
  • System 10 extending through wall 22 of furnace 12 then obtains inlet air from the ambient environment and provides a streamline air flow contour which opposes flame front 20 longitudinally 13 and in a transverse direction 15.
  • Dependent on the angularization of vanes 52 and the plane to which they are formed air may be vortexed helically or in a vertical direction within chamber 14.
  • Ceramic sleeve 54 attached to elbow 36 through wall flange 44 extends longitudinally into chamber 14 through furnace wall 22. Sleeve 54 is directed toward flame front 20 to provide a path constraint for the inlet air as well as a preheating capability.
  • Ceramic sleeve 54 is tubular and made of a material such as silicon carbide which has a high termal conductivity and can withstand the elevated temperatures within chamber 14. A high thermal conductivity for sleeve 54 is required in order to transport as much heat as possible through the tubular walls into the incoming stream of supply air.
  • Thermal conductivity of silicon carbide in the chamber environment is seen to vary between -50 BTU/HRFI' F. for chamber 14 temperature range between 800-2400 F. respectively.
  • supply air passing through conduit passage 40 and sleeve through opening 56 may be heated by as much as several hundred degrees before impinging on flame front 20.
  • Nozzle end 58 of sleeve 54 provides a smaller diameter axial opening that is found in sleeve through opening 56.
  • the air supply as it is being heated upon passage through sleeve 54 has its velocity increased through the nozzle effect created by the throat of nozzle end 58.
  • the increased velocity of the inlet air in combination with the vortex motion created by angled vanes 52 provides for greater turbulance and agitation of the air supply in order to utilize a larger portion of the unburned gases and permit a larger heat source from flame front 20.
  • Fuel combustion within combustion chamber 14 is dependent upon the chemical formula of the specific fuel and the amount of air inlet to aid in combustion. Fuels from different geographical locations vary somewhat in their constituency, however, a fuel having the formula C H is taken to show operation of system 10 as described. In standard furnaces 12, a combustion process is found with atmospheric air and not with pure oxygen. Normally, the nitrogen and other gases in the air are merely dilutants of the incoming oxygen and appear in the products mainly unchanged in form. This may be seen from the well known combustion of carbon and oxygen:
  • the step of providing excess oxygen to chamber 14 is taken further to enable cracking of still more of the unburned fuel and reduce pollutants while at the same time increasing fuel efficiency.
  • Inlet air passing into chamber 14 opposes flame front 20, thereby forcing the flame envelope back and producing an effective heat source having a smaller surface area of radiation.
  • the heat radiated away from the flame envelope may be written:
  • system 10 The actual effect that is created by system 10 is to make an afterbumer of the primary flame. More time is allowed for combustion of the fuel within the oxidizing zone thereby providing for a greater fuel consumption than was previously obtainable.
  • the method for increasing fuel combustion efficiency within chamber 14 includes the introduction of inlet air into chamber 14 directed toward and impinging on flame front 20 being emitted from fuel burner 16.
  • Ambient air is inlet to fan 14 and is passed under high pressure through conduit 28 and introduced into chamber 14.
  • Inlet air flow is positioned in a streamline contour opposing flame front 20 in longitudinal direction 13.
  • the inlet air is vortexed upon passage through angled vanes 52 to produce a streamline air flow contour in transverse direction 15 to provide a flow combination motion.
  • the inlet air is transported within chamber 14, it is preheated by motion through a high thermally conductive sleeve 54 subsequent to chamber 14 introduction and prior to air inlet flow impingement on flame front 20.
  • the velocity of the inlet air is increased after preheating by nozzle end 58 of ceramic sleeve 54 to provide high velocity impingement on flame front 20.
  • FIG. 5 An embodiment of assembly 10 is shown in FIG. 5 where inlet air is drawn into furnace 12 through a pressure differential between internally heated air and the ambient external environment. As shown, ambient air enters partial passage 72 developed between inner furnace wall 74 and outer wall 76 through air inlet opening 60. Inlet air flows through partial passage 72 into combustion chamber 14 through fuel burner inlet opening 62 and ceramic sleeve opening 64. Damper door 66, hinged to face plate 68, is rotatable about a hinged axis. Ceramic sleeve opening 64 determines the amount of inlet air which will be preheated and vortexed into flame front 20.
  • Heater air within chamber 14 has a higher temperature than ambient external air and, therefore, will have a lower pressure to promote a continuous flow of external air through passage 72 into chamber 14.
  • Proper percentages of air flowing through fuel burner inlets 62 and ceramic sleeve opening 64 may be determined, and damper door 66 automatically adjusted to promote the most efficient burning of fuel within chamber 14.
  • Angled vanes 52 may be placed within face plate 68 or on side walls of ceramic sleeve 54 as shown in FIG. 7. Inlet air flowing through ceramic sleeve 54 is vortexed through angled vanes 52 in a direction countercurrent to flame front 20. Ceramic sleeve 54 extends longitudinally and in the same direction as fuel burner 16, however, vortexing of inlet air provides for a compression of flame front 20 in a manner similar to the counter current flow described previously.
  • FIG. 6 Another embodiment of the invention is shown in FIG. 6 where preheating sleeve 54 is spatially positioned similar to that shown in the embodiment described by FIG. 5. Induced draft is formed in this embodiment by fan 24 which inputs air into chamber 14 under high pressure. Sleeve 54 located below fuel burner 16 in furnace side wall 18 extends longitudinally and in the same direction as flame front 20. Air flowing longitudinally through preheating sleeve 54 is vortexed in a manner similar to that described for the embodiment of FIG. 5 and is driven into the flame front to compress and cause turbulent flow which increases heat transfer efficiency yielding a higher heat dissipation capability from flame front 20.
  • higher temperatures in the combusting zone are obtained by heating a predetermined proportional amount of secondary air within furnace 12.
  • the introduction of secondary air in the manner described produces more rapid and complete combustion within the flame envelope having a more uniform temperature throughout the combusting zone than was found in previous systems.
  • Temperature gradients from a hot to cold zone within chamber 14 produce vast quantities of pollutants in the form of smoke and soot.
  • a reduction in fuel consumption is found through the use of system 10 where a major proportion of radiant heat release is captured by steam generating tubes which may be exposed to the flame.
  • the shaping and directing of heated air in a vortexed and countercurrent manner reduces the requirement for high excess air to be maintained in order to provide a clean flame.
  • the lower requirement for clean, efficient combustion with less excess air will result in a further reduction of heat losses and higher combustion efficiency.
  • the forcing of air into chamber 14 with a controlled volume and velocity having a rotational direction into the main flame front concentrates the hydrocarbons in the highest temperature zone which assists in a high radiant heat release. Additional savings are realized in the reduction of soot, blowing requirements, cleaner tube surfaces, and maintenance of a maximum degree of convection gas heat transfer.
  • a supplemental air supply assembly to increase fuel combustion efficiency within a combustion chamber having a fuel burner forming a flame envelope having a surface area with a longitudinal and a transverse direction comprising:
  • high pressure air inlet means extending through a wall of said combustion chamber for decreasing said surface area of said flame envelope thereby increasing the radiant heat transport to enclosing internal boundaries of said combustion chamber, said high pressure air having a direction substantially opposing said longitudinal direction of said flame envelope;
  • vortexing means includes helical dispersion means to induce said streamline air flow helically about said longitudinal dimension of said flame envelope.
  • said air inlet means includes means for providing air flow pressure internal to said combustion chamber in excess of said ambient air pressure.
  • blower means external to said combustion chamber for producing a high pressure air flow
  • conduit means coupled to said blower means and said wall of said combustion chamber to direct a predetermined quantity of said high pressure air into said combustion chamber.
  • conduit means includes:
  • a temperature sensing element connected on opposing ends to said damping motor means and internal to said combustion chamber respectively, said temperature sensing element to measure said air flow temperature within said chamber and actuate said damping motor means.
  • conduit means is secured to said combustion chamber wall longitudinally opposed to said flame envelope to produce said air flow in a direction countercurrent to said longitudinal dimension.
  • conduit means includes a plurality of angled vanes secured to an inner diameter of said conduit means to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
  • the assembly as recited in claim 9 includes an elbow section to transform initially directed air flow from said blower means to a longitudinal flow within said combustion chamber.
  • said elbow sectional element includes a tube extending in said longitudinal dimension, said tube being fixedly secured central to said passage of said conduit means and passing external thereto through a wall of said elbow sectional element, said tubing having a central through opening sealed with a high temperature transparent material external to said elbow sectional element for visual observation internal to said combustion chamber.
  • said tube includes a plurality of formed vanes secured to the periphery of said tube within said passage of said conduit means to direct the flow of said air helically about said longitudinal dimension of said flame envelope.
  • said preheating air means includes a tubular sleeve having a through opening, said sleeve being coaxially displaced with respect to said air inlet means.
  • preheating air sleeve includes a plurality of helically extended air flow vanes secured to an internal diameter thereof to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
  • Equation (3) provides for the chemically correct, stoichiometric or theoretical amount of air necessary for the process to convert the fuel into completely oxidized products.
  • the time of the fuel/air mixture is not sufficient in the combustion zone to break down their atomic bond.
  • excess air may be incorporated to provide more oxygen. Assuming 25 percent excess air is supplied to the reaction as described in equation (3), it is seen:
  • the step of providing excess oxygen to chamber 14 is taken further to enable cracking of still more of the unburned fuel and reduce pollutants while at the same time increasing fuel efficiency.
  • Inlet air passing into chamber 14 opposes flame front 20, thereby forcing the flame envelope back and producing an effective heat source having a smaller surface area of radiation.
  • the heat radiated away from the flame envelope may be written:
  • the actual effect that is created by system is to make an afterbumer of the primary flame. More time is allowed for combustion of the fuel within the oxidizing zone thereby providing for a greater fuel consumption than was previously obtainable.
  • the method for increasing fuel combustion efficiency within chamber 14 includes the introduction of inlet air into chamber 14 directed toward and impinging on flame front 20 being emitted from fuel burner 16.
  • Ambient air is inlet to fan 14 and is passed under high pressure through conduit 28 and introduced into chamber 14.
  • Inlet air flow is positioned in a streamline contour opposing flame front 20 in longitudinal direction 13.
  • the inlet air is vortexed upon passage through angled vanes 52 to produce a streamline air flow contour in transverse direction 15 to provide a flow combination motion.
  • the inlet air is transported within chamber 14, it is preheated by motion through a high thermally conductive sleeve 54 subsequent to chamber 14 introduction and prior to air inlet flow impingement on flame front 20.
  • the velocity of the inlet air is increased after preheating by nozzle end 58 of ceramic sleeve 54 to provide high velocity impingement on flame front 20.
  • FIG. 5 An embodiment of assembly 10 is shown in FIG. 5 where inlet air is drawn into furnace 12 through a pressure differential between internally heated air and the ambient external environment. As shown, ambient air enters partial passage 72 developed between inner furnace wall 74 and outer wall 76 through air inlet opening 60. Inlet air flows through partial passage 72 into combustion chamber 14 through fuel burner inlet opening 62 and ceramic sleeve opening 64. Damper door 66, hinged to face plate 68, is rotatable about a hinged axis. Ceramic sleeve opening 64 determines the amount of inlet air which will be preheated and vortexed into flame front 20.
  • Heater air within chamber 14 has a higher temperature than ambient external air and, therefore, will have a lower pressure to promote a continuous flow of external air through passage 72 into chamber 14.
  • Proper percentages of air flowing through fuel burner inlets 62 and ceramic sleeve opening 64 may be determined, and damper door 66 automatically adjusted to promote the most efficient burning of fuel within chamber 14.
  • Angled vanes 52 may be placed within face plate 68 or on side walls of ceramic sleeve 54 as shown in FIG. 7. Inlet air flowing through ceramic sleeve 54 is vortexed through angled vanes 52 in a direction countercurrent to flame front 20. Ceramic sleeve 54 extends longitudinally and in the same direction as fuel burner 16, however, vortexing of inlet air provides for a compression of flame front 20 in a manner similar to the counter current flow described previously.
  • FIG. 6 Another embodiment of the invention is shown in FIG. 6 where preheating sleeve 54 is spatially positioned similar to that shown in the embodiment described by FIG. 5. Induced draft is formed in this embodiment by fan 24 which inputs air into chamber 14 under high pressure. Sleeve 54 located below fuel burner 16 in furnace side wall 18 extends longitudinally and in the same direction as flame front 20. Air flowing longitudinally through preheating sleeve 54 is vortexed in a manner similar to that described for the embodiment of FIG. 5 and is driven into the flame front to compress and cause turbulent flow which increases heat transfer efficiency yielding a higher heat dissipation capability from flame front 20.
  • higher temperatures in the combusting zone are obtained by heating a predetermined proportional amount of secondary air within furnace 12.
  • the introduction of secondary air in the manner described produces more rapid and complete combustion within the flame envelope having a more uniform temperature throughout the combusting zone than was found in previous systems.
  • Temperature gradients from a hot to cold zone within chamber 14 produce vast quantifies of pollutants in the form of smoke and soot.
  • a reduction in fuel consumption is found through the use of system 10 where a major proportion of radiant heat release is captured by steam generating tubes which may be exposed to the flame.
  • the shaping and directing of heated air in a vortexed and countercurrent manner reduces the requirement for high excess air to be maintained in order to provide a clean flame.
  • the lower requirement for clean, efficient combustion with less excess air will result in a further reduction of heat losses and higher combustion efficiency.
  • the forcing of air into chamber 14 with a controlled volume and velocity having a rotational direction into the main flame front concentrates the hydrocarbons in the highest temperature zone which assists in a high radiant heat release. Additional savings are realized in the reduction of soot, blowing requirements, cleaner tube surfaces, and maintenance of a maximum degree of convection gas heat transfer.
  • a supplemental air supply assembly to increase fuel combustion efficiency within a combustion chamber having a fuel burner forming a flame envelope having a surface area with a longitudinal and a transverse direction comprising:
  • high pressure air inlet means extending through a wall of said combustion chamber for decreasing said surface area of said flame envelope thereby increasing the radiant heat transport to enclosing internal boundaries of said combustion chamber, said high pressure air having a direction substantially opposing said longitudinal direction of said flame envelope;
  • vortexing means includes helical dispersion means to induce said streamline air flow helically about said longitudinal dimension of said flame envelope.
  • said air inlet means includes means for providing air flow pressure internal to said combustion chamber in excess of said ambient air pressure.
  • blower means external to said combustion chamber for producing a high pressure air flow
  • conduit means coupled to said blower means and said wall of said combustion chamber to direct a predetermined quantity of said high pressure air into said combustion chamber.
  • conduit means includes:
  • a temperature sensing element connected on opposing ends to said damping motor means and internal to said combustion chamber respectively, said temperature sensing element to measure said air flow temperature within said chamber and actuate said damping motor means.
  • conduit means is secured to said combustion chamber wall longitudinally opposed to said flame envelope to produce said air flow in a direction countercurrent to said longitudinal dimension.
  • conduit means includes a plurality of angled vanes secured to an inner diameter of said conduit means to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
  • the assembly as recited in claim 9 includes an elbow section to transform initially directed air flow from said blower means to a longitudinal flow within said combustion chamber.
  • said elbow sectional element includes a tube extending in said longitudinal dimension, said tube being fixedly secured central to said passage of said conduit means and passing external thereto through a wall of said elbow sectional element, said tubing having a central through opening sealed with a high temperature transparent material external to said elbow sectional element for visual observation internal to said combustion chamber.
  • said tube includes a plurality of formed vanes secured to the periphery of said tube within said passage of said conduit means to direct the flow of said air helically about said longitudinal dimension of said flame envelope.
  • said preheating air means includes a tubular sleeve having a through opening, said sleeve being coaxially displaced with respect to said air inlet means.
  • preheating air sleeve includes a plurality of helically extended air flow vanes secured to an internal diameter thereof to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.

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  • Combustion & Propulsion (AREA)
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  • General Engineering & Computer Science (AREA)
  • Pre-Mixing And Non-Premixing Gas Burner (AREA)
  • Combustion Of Fluid Fuel (AREA)

Abstract

A supplemental air supply assembly and method for transporting and directionally orienting high pressure air impingement on a flame envelope within a combustion chamber. Ambient air is introduced into a fan connected to a conduit which forces inlet air into the combustion chamber. The inlet air is positioned to oppose the flame envelope and is vortexed by a series of angled vanes fastened to the conduit. The air is preheated within an elongated sleeve prior to interaction with the flame envelope. The amount of high pressure inlet air introduced into the chamber is regulated.

Description

United States Patent Adams [54] COMBUSTION CHAMBER SUPPLEMENTAL AIR SUPPLY ASSEMBLY AND METHOD [72] Inventor: Jack C. Adams, Philadelphia, Pa.
[73] Assignee: Ecological Controls, Inc., Penndel,
22 Filed: Nov. 12,1970
21 Appl.No.: 88,819
52 us. c1. ..431/8, 431 190, 431/252 51 110. C1. ..F23c 7/00 581 Field of Search ..431/8, 10, 252, 190
[56] References Cited UNITED STATES PATENTS 2,022,512 11/1935 Macchi ..431/190 2,471,101 5/1959 Feinberg ..431/190 x 3,013,865 12/1961 Webster et a] ..431/190 x 3,291,182 12/1966 Dow 6161. ..431 165 2,489,244 11/1949 Stalego ..431/158 x 1 1 Aug. 22, 1972 2,368,827 2/1945 Hanson et al. ..431/190 X 1,734,669 11/1929 Frisch ..43 l/l90 X FOREIGN PATENTS OR APPLICATIONS 387,751 2/1933 Great Britain ..431/190 Primary ExaminerEdwa.rd G. Favors Attorney-Maleson, Kimmelman & Ratner and Allan Ratner [57] ABSTRACT A supplemental air supply assembly and method for transporting and directionally orienting high pressure air impingement on a flame envelope within a combustion chamber. Ambient air is introduced into a fan connected to a conduit which forces inlet air into the combustion chamber. The inlet air is positioned to oppose the flame envelope and is vortexed by a series of angled vanes fastened to the conduit. The air is preheated within an elongated sleeve prior to interaction with the flame envelope. The amount of high pressure inlet air introduced into the chamber is regulated.
20 Claims, 7 Drawing figures P'A'IENTEDmzz I912 3.685.946
SHEET 1 0F 2 I FIG.
FIG. 3 52; 46
/50 INVENTOR JACK c. ADAMS BY 48 49 mn 'W M ATTORNEYS COMBUSTION CHAMBER SUPPLEMENTAL AIR SUPPLY ASSEMBLY AND METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the fieldof air supply units for combustion chambers. In particular this invention pertains to an assembly and method of introducing supplemental air into a combustion chamber which is directionally oriented and has a particular streamline contour with respect to a flame envelope.
2. Prior Art air into a chamber at the periphery or under the flameenvelope, but none are known which directly force the inlet air into the flame envelope in a way which will compress the surface area thereby increasing the flame temperature to ensure substantially complete fuel combustion.
SUMMARY OF THE INVENTION A supplemental air supply assembly and method for increasing fuel combustion efficiency within a combustion chamber. Included within the chamber is a fuel burner which forms a flame envelope having both a longitudinal and transverse dimension. The assembly comprises an air inlet device which extends through the wall of the combustion chamber. The air inlet device obtains ambient air external to the combustion chamber and produces a streamline contour air flow which is both opposed to the longitudinal dimension and forced in the transverse dimension of the flame envelope.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of the supplemental air supply assembly;
FIG. 2 is a perspective view of the elbow sectional element of the assembly showing the vortexing vanes;
FIG. 3 is a cross-section view of the elbow sectional element taken along the section line 3-3 of FIG. 2;
FIG. 4 is a cross-section view of the invention installed in a furnace operation;
FIG. 5 is a cross-section view of an embodiment of 0 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1-4 there is shown a supplemental air supply assembly or air system 10 to increase the fuel combustion efficiency of furnace 12. Fuel burner 16 extends through furnace side wall 18 into combustion chamber 14 from the external environment. A controlled fuel/air mixture is provided to burner 16 to produce flame front 20 after ignition, which in turn promotes a regulated heat source within chamber 14. Flame front 20 forms a flame envelope having both a longitudinal 13 and transverse dimension 15 as shown in FIG. 4. In total, system 10 operates functionally to introduce a preheated air flow supply into chamber 14 being both vortexed and countercurrent to flame front 20. The quantity of air inserted into furnace 12 is controlled to match the unburned gases and heavy carbon which wraps these compounds into the core of the flame to produce a higher flame temperature within a.
more compact flame envelope. In other words, by compressing the effective surface area of the flame higher temperatures as well as heat source capabilities are achieved. As will later be described in greater detail, system 10 produces increased flame temperatures, as well as an increase in fuel efficiency through the release of greater radiant heat transfer energy which is proportional to the fourth power of the flame temperature produced.
Supplemental air supply assembly 10 comprises four major systems including fan or blower 24, damping device 34, conduit 28, and preheating air supply ceramic sleeve 54. Assembly 10 is fixedly located adjacent to furnace 12 to provide an air supply from the external ambient environment. Furnace wall 22 includes an opening passing therethrough and inlet airunder pressure may be incorporated into chamber 14 through conduit passage 40 longitudinally 13 opposing and impinging on flame front 20.
Fan or blower 24 has an inlet opening located external to furnace 12 to intake ambient air and an outlet passage coaxially positioned with respect to conduit 28 to provide a conduit pathway through which the high pressure air may be transferred. Fan 24 may be of the standard centrifugal type whose selection is based on the empiracally derived necessary quantity of air determined for a specific furnace 12 application. In general, blower 24 mayconsist of a squirrel cage series of vanes or blades mounted on the rim of a wheel. The vanes are generally slanted forward in the direction of rotation of the wheel in such a manner as to provide a maximum discharge of air. It has been empiracally shown that up to 20 percent of the air input at fuel burner 16 must be accommodated byfan 24 in order to obtain maximum bunting efficiency within chamber 14. Selection of proper fans or blowers 24 may be made from a standardized grouping of high pressure air devices well.
known in the art. Fan 24 is operated by motor 26 which may be wired to a potentiometer at the head end of furnace 12 in conjunction with burner 16 which then governs the fuel/air mixture being input to chamber 14.. Therefore, ambient air intake of fan 24 is exhausted under pressure throughconduit 28' and enters furnace 12 through wall 22 as a function of the amount required to maximize fuel combustion efliciency of burner 16.
The amount of high pressure inlet air being delivered to chamber 14 is regulated either by a control of fan or blower 24 through motor 26 through damping device 34 which is positioned coaxially with the outlet of fan 24 and conduit 28 on opposing ends thereof. Damping device 34, not shown in detail, may be one of a standard set of assemblies which restrict conduit passage 40 as a function of the amount of inlet air required within chamber 14. Damping motor 30 operates linkage 32 external to conduit 28 and passes internal to conduit 28 to adjust an air shutter placed within passage 40. In this manner, the air shutter is angularly rotated within passage 40 to regulate the cross-sectional area of conduit passage 40 and supply the necessary quantity of air. Automatic operation of device 34 may be maintained through a conventional thermostat connected to motor 30. A thermostat may be connected to a temperature sensing device, such as a thermistor or thermocouple, which measures the temperature of the incoming inlet air within chamber 14. Device 34 may then be operated automatically through motor 30 as a function of inlet air temperature.
Conduit 28 comprises upper conduit member 38 and elbow section 36 rigidly secured to each other to form a continuous conduit passage 40 terminating on opposing ends at damping device 34 and furnace wall 22. Functionally, conduit 28 provides a path for the high pressure inlet air from fan 24 or damping device 34 into combustion chamber 14. Elbow section 36 of conduit 28 is fastened on opposing ends thereof to upper conduit member 38 and furnace wall 22 forming a constant diameter conduit passage 40 therebetween. Section 36 forms a bend providing a normal vector air outlet to that of the incoming air from upper conduit member 38. This 90 degree bend provides for a tube or peepsight 46 to be incorporated into system 10, but is not necessary for operation.
Rigid attachment of elbow section 36 to upper conduit member 38 and furnace wall 22 is made through elbow flange 42 and wall flange 44 respectively. Flange attachments may be by bolting, welding or some other means not important to the invention. In this manner ambient air input to fan 24, as shown in FIG. 4, may be transported under a high pressure through upper conduit member 38, elbow section 36 and through an opening in furnace wall 22 into combustion chamber 14 longitudinally opposing or counter-current to flame front 20.
Section 36, as depicted in FIGS. 2 and 3 includes a tube or peepsight 46 extending in longitudinal direction 13 through an outer wall of elbow 36 and into conduit passage 40 centrally terminating adjacent to furnace wall 22. Tube 46 is fastened to the outer wall of section 36 by weld 45 or by bolting. Tube passage 48 extending through peepsight 46 provides for visual observation of flame front to an observer located external to furnace l2. Passage 48 is covered on tube external end 49 by a disc of high temperature transparent glass 50 to protect the observer.
Tube end 47 of peepsight 46 includes a plurality of vanes 52 rigidly secured to the outer diameter of tube 46 and extending radially to the inner diameter wall of elbow section 36. Vanes 52 are angled with respect to longitudinal direction 13 to provide a vortex motion for the incoming inlet air. In this manner, inlet air which has been given a longitudinal flow contour velocity is now brought into chamber 14 having a combined motion. System 10, extending through wall 22 of furnace 12 then obtains inlet air from the ambient environment and provides a streamline air flow contour which opposes flame front 20 longitudinally 13 and in a transverse direction 15. Dependent on the angularization of vanes 52 and the plane to which they are formed air may be vortexed helically or in a vertical direction within chamber 14.
In addition it has been found that supply air entering combustion chamber 14 of furnace 12 can substantially increase the fuel burning efficiency by incorporating preheated inlet air. Ceramic sleeve 54 attached to elbow 36 through wall flange 44 extends longitudinally into chamber 14 through furnace wall 22. Sleeve 54 is directed toward flame front 20 to provide a path constraint for the inlet air as well as a preheating capability. Ceramic sleeve 54 is tubular and made of a material such as silicon carbide which has a high termal conductivity and can withstand the elevated temperatures within chamber 14. A high thermal conductivity for sleeve 54 is required in order to transport as much heat as possible through the tubular walls into the incoming stream of supply air. Thermal conductivity of silicon carbide in the chamber environment is seen to vary between -50 BTU/HRFI' F. for chamber 14 temperature range between 800-2400 F. respectively. In this way, supply air passing through conduit passage 40 and sleeve through opening 56 may be heated by as much as several hundred degrees before impinging on flame front 20.
Nozzle end 58 of sleeve 54 provides a smaller diameter axial opening that is found in sleeve through opening 56. The air supply as it is being heated upon passage through sleeve 54 has its velocity increased through the nozzle effect created by the throat of nozzle end 58. The increased velocity of the inlet air in combination with the vortex motion created by angled vanes 52 provides for greater turbulance and agitation of the air supply in order to utilize a larger portion of the unburned gases and permit a larger heat source from flame front 20.
Fuel combustion within combustion chamber 14 is dependent upon the chemical formula of the specific fuel and the amount of air inlet to aid in combustion. Fuels from different geographical locations vary somewhat in their constituency, however, a fuel having the formula C H is taken to show operation of system 10 as described. In standard furnaces 12, a combustion process is found with atmospheric air and not with pure oxygen. Normally, the nitrogen and other gases in the air are merely dilutants of the incoming oxygen and appear in the products mainly unchanged in form. This may be seen from the well known combustion of carbon and oxygen:
In the chemically balanced equation for combustion of the fuel having the formula C ll it is seen:
combusting the total amount of fuel, excess air may be incorporated to provide more oxygen. Assuming 25 percent excess air is supplied to the reaction as described in equation (3 it is seen:
The excess air appears in the products unchanged in form. In this manner, excess oxygen is provided to oxidize some of the fuel which was not initially combusted.
In the present invention, the step of providing excess oxygen to chamber 14 is taken further to enable cracking of still more of the unburned fuel and reduce pollutants while at the same time increasing fuel efficiency. Inlet air passing into chamber 14 opposes flame front 20, thereby forcing the flame envelope back and producing an effective heat source having a smaller surface area of radiation. The heat radiated away from the flame envelope may be written:
Q12 A6 (5) where:
Q; Heat transport by radiation from flame envelope Stefan Boltzmann constant A Effective surface area of flame envelope 6 Emissivity of flame envelope T= Temperature of flame envelope As can be seen in equation (5) as the effective surface area of the flame envelope is compressed, the temperature of the envelope must be increased for the same amount of radiant heat generation. Increasing the flame front 20 temperature therein provides more cracking capability with an associated increase in the amount of heat being transported. Vortexing of the inlet air through preheating sleeve 54 also forces some of the unused fuel back into flame front 20 to increase the heating capability of furnace 12. The entire process is iterative wherein a lower flame envelope surface area causes a higher flame temperature which in turn causes a greater heat capability to burn more of the fuel.
The actual effect that is created by system 10 is to make an afterbumer of the primary flame. More time is allowed for combustion of the fuel within the oxidizing zone thereby providing for a greater fuel consumption than was previously obtainable.
It will now be understood that the method for increasing fuel combustion efficiency within chamber 14 includes the introduction of inlet air into chamber 14 directed toward and impinging on flame front 20 being emitted from fuel burner 16. Ambient air is inlet to fan 14 and is passed under high pressure through conduit 28 and introduced into chamber 14. Inlet air flow is positioned in a streamline contour opposing flame front 20 in longitudinal direction 13. At the entrance to chamber 14 the inlet air is vortexed upon passage through angled vanes 52 to produce a streamline air flow contour in transverse direction 15 to provide a flow combination motion. Once the inlet air is transported within chamber 14, it is preheated by motion through a high thermally conductive sleeve 54 subsequent to chamber 14 introduction and prior to air inlet flow impingement on flame front 20. In addition, the velocity of the inlet air is increased after preheating by nozzle end 58 of ceramic sleeve 54 to provide high velocity impingement on flame front 20.
An embodiment of assembly 10 is shown in FIG. 5 where inlet air is drawn into furnace 12 through a pressure differential between internally heated air and the ambient external environment. As shown, ambient air enters partial passage 72 developed between inner furnace wall 74 and outer wall 76 through air inlet opening 60. Inlet air flows through partial passage 72 into combustion chamber 14 through fuel burner inlet opening 62 and ceramic sleeve opening 64. Damper door 66, hinged to face plate 68, is rotatable about a hinged axis. Ceramic sleeve opening 64 determines the amount of inlet air which will be preheated and vortexed into flame front 20. Heater air within chamber 14 has a higher temperature than ambient external air and, therefore, will have a lower pressure to promote a continuous flow of external air through passage 72 into chamber 14. Proper percentages of air flowing through fuel burner inlets 62 and ceramic sleeve opening 64 may be determined, and damper door 66 automatically adjusted to promote the most efficient burning of fuel within chamber 14. Angled vanes 52 may be placed within face plate 68 or on side walls of ceramic sleeve 54 as shown in FIG. 7. Inlet air flowing through ceramic sleeve 54 is vortexed through angled vanes 52 in a direction countercurrent to flame front 20. Ceramic sleeve 54 extends longitudinally and in the same direction as fuel burner 16, however, vortexing of inlet air provides for a compression of flame front 20 in a manner similar to the counter current flow described previously.
Another embodiment of the invention is shown in FIG. 6 where preheating sleeve 54 is spatially positioned similar to that shown in the embodiment described by FIG. 5. Induced draft is formed in this embodiment by fan 24 which inputs air into chamber 14 under high pressure. Sleeve 54 located below fuel burner 16 in furnace side wall 18 extends longitudinally and in the same direction as flame front 20. Air flowing longitudinally through preheating sleeve 54 is vortexed in a manner similar to that described for the embodiment of FIG. 5 and is driven into the flame front to compress and cause turbulent flow which increases heat transfer efficiency yielding a higher heat dissipation capability from flame front 20.
In the invention as described, higher temperatures in the combusting zone are obtained by heating a predetermined proportional amount of secondary air within furnace 12. The introduction of secondary air in the manner described produces more rapid and complete combustion within the flame envelope having a more uniform temperature throughout the combusting zone than was found in previous systems. Temperature gradients from a hot to cold zone within chamber 14 produce vast quantities of pollutants in the form of smoke and soot. In boiler applications a reduction in fuel consumption is found through the use of system 10 where a major proportion of radiant heat release is captured by steam generating tubes which may be exposed to the flame.
The shaping and directing of heated air in a vortexed and countercurrent manner reduces the requirement for high excess air to be maintained in order to provide a clean flame. The lower requirement for clean, efficient combustion with less excess air will result in a further reduction of heat losses and higher combustion efficiency. The forcing of air into chamber 14 with a controlled volume and velocity having a rotational direction into the main flame front concentrates the hydrocarbons in the highest temperature zone which assists in a high radiant heat release. Additional savings are realized in the reduction of soot, blowing requirements, cleaner tube surfaces, and maintenance of a maximum degree of convection gas heat transfer.
What is claimed is:
1. A supplemental air supply assembly to increase fuel combustion efficiency within a combustion chamber having a fuel burner forming a flame envelope having a surface area with a longitudinal and a transverse direction comprising:
high pressure air inlet means extending through a wall of said combustion chamber for decreasing said surface area of said flame envelope thereby increasing the radiant heat transport to enclosing internal boundaries of said combustion chamber, said high pressure air having a direction substantially opposing said longitudinal direction of said flame envelope; and,
means for vortexing said high pressure air for encompassing said flame envelope surface area.
2. The assembly as recited in claim 1 wherein said vortexing means includes helical dispersion means to induce said streamline air flow helically about said longitudinal dimension of said flame envelope.
3. The assembly as recited in claim 1 wherein said air inlet means is positioned within said wall of said combustion chamber longitudinally opposing said flame envelope.
4. The assembly as recited in claim 1 wherein said air inlet means includes means for providing air flow pressure internal to said combustion chamber in excess of said ambient air pressure.
5. The assembly as recited in claim 1 wherein said air inlet means includes:
blower means external to said combustion chamber for producing a high pressure air flow; and,
conduit means coupled to said blower means and said wall of said combustion chamber to direct a predetermined quantity of said high pressure air into said combustion chamber.
6. The assembly as recited in claim wherein there is provided a damping device for controllably restricting the internal passage of said conduit means to regulate the amount of high pressure air flowing through said conduit means.
7. The assembly as recited in claim 5 wherein said conduit means includes:
a. damping motor means;
b. an air flow blocking panel angularly oriented with respect to said conduit means passage to restrict the cross-sectional area of said passage responsive to said damping motor means actuation; and,
c. a temperature sensing element connected on opposing ends to said damping motor means and internal to said combustion chamber respectively, said temperature sensing element to measure said air flow temperature within said chamber and actuate said damping motor means.
8. The assembly as recited in claim 5 wherein said conduit means is secured to said combustion chamber wall longitudinally opposed to said flame envelope to produce said air flow in a direction countercurrent to said longitudinal dimension.
9. The assembly as recited in claim 5 wherein said conduit means includes a plurality of angled vanes secured to an inner diameter of said conduit means to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
10. The assembly as recited in claim 9 includes an elbow section to transform initially directed air flow from said blower means to a longitudinal flow within said combustion chamber.
ll.'The assembly as recited in claim 10 wherein said elbow sectional element includes a tube extending in said longitudinal dimension, said tube being fixedly secured central to said passage of said conduit means and passing external thereto through a wall of said elbow sectional element, said tubing having a central through opening sealed with a high temperature transparent material external to said elbow sectional element for visual observation internal to said combustion chamber.
12. The assembly as recited in claim 9 wherein said tube includes a plurality of formed vanes secured to the periphery of said tube within said passage of said conduit means to direct the flow of said air helically about said longitudinal dimension of said flame envelope.
13. The assembly as recited in claim 1 including preheating air means rigidly secured to said air inlet means extending within said combustion chamber in said longitudinal dimension directed toward said flame envelope to heat said inlet air within said combustion chamber prior to entry into said flame envelope.
14. The assembly as recited in claim 13 wherein said preheating air means includes a tubular sleeve having a through opening, said sleeve being coaxially displaced with respect to said air inlet means.
15. The assembly as recited in claim 14 wherein said sleeve includes a first end fastened to said air inlet means and a second end having a decreased nozzle opening to increase the velocity of said air flow.
16. The assembly as recited in claim 14 wherein said sleeve is constructed of a high thermally conductive material to permit transport of heat from said combustion chamber to said air flowing therethrough.
17. The assembly as recited in claim 14 wherein said preheating air sleeve is constructed of silicon carbide.
18. The assembly as recited in claim 14 wherein said preheating air sleeve includes a plurality of helically extended air flow vanes secured to an internal diameter thereof to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
19. The method of increasing radiant heat transport from a flame envelope contained within a combustion chamber having a fuel burner, said flame envelope 0,11,a 12.50; 4am 8002 911,0 41m (3) Equation (3) provides for the chemically correct, stoichiometric or theoretical amount of air necessary for the process to convert the fuel into completely oxidized products. In present furnaces 12 the time of the fuel/air mixture is not sufficient in the combustion zone to break down their atomic bond. In order to aid in combusting the total amount of fuel, excess air may be incorporated to provide more oxygen. Assuming 25 percent excess air is supplied to the reaction as described in equation (3), it is seen:
031113 02. 5)Oz 4(47)N2 800 EH20 3.1202 75N7 (4) The excess air appears in the products unchanged in form. In this manner, excess oxygen is provided to oxidize some of the fuel which was not initially combusted.
In the present invention, the step of providing excess oxygen to chamber 14 is taken further to enable cracking of still more of the unburned fuel and reduce pollutants while at the same time increasing fuel efficiency. Inlet air passing into chamber 14 opposes flame front 20, thereby forcing the flame envelope back and producing an effective heat source having a smaller surface area of radiation. The heat radiated away from the flame envelope may be written:
QR: A6 (s) where:
Q Heat transport by radiation from flame envelope Stefan Boltzmann constant A Efl'ective surface area of flame envelope e= Emissivity of flame envelope T= Temperature of flame envelope As can be seen in equation (5) as the effective surface area of the flame envelope is compressed, the tempera ture of the envelope must be increased for the same amount of radiant heat generation. Increasing the flame front 20 temperature therein provides more cracking capability with an associated increase in the amount of heat being transported. Vortexing of the inlet air through preheating sleeve 54 also forces some of the unused fuel back into flame front 20 to increase the heating capability of furnace 12 The entire process is iterative wherein a lower flame envelope surface area causes a higher flame temperature which in turn causes a greater heat capability to burn more of the fuel.
The actual effect that is created by system is to make an afterbumer of the primary flame. More time is allowed for combustion of the fuel within the oxidizing zone thereby providing for a greater fuel consumption than was previously obtainable.
It will now be understood that the method for increasing fuel combustion efficiency within chamber 14 includes the introduction of inlet air into chamber 14 directed toward and impinging on flame front 20 being emitted from fuel burner 16. Ambient air is inlet to fan 14 and is passed under high pressure through conduit 28 and introduced into chamber 14. Inlet air flow is positioned in a streamline contour opposing flame front 20 in longitudinal direction 13. At the entrance to chamber 14 the inlet air is vortexed upon passage through angled vanes 52 to produce a streamline air flow contour in transverse direction 15 to provide a flow combination motion. Once the inlet air is transported within chamber 14, it is preheated by motion through a high thermally conductive sleeve 54 subsequent to chamber 14 introduction and prior to air inlet flow impingement on flame front 20. In addition, the velocity of the inlet air is increased after preheating by nozzle end 58 of ceramic sleeve 54 to provide high velocity impingement on flame front 20.
An embodiment of assembly 10 is shown in FIG. 5 where inlet air is drawn into furnace 12 through a pressure differential between internally heated air and the ambient external environment. As shown, ambient air enters partial passage 72 developed between inner furnace wall 74 and outer wall 76 through air inlet opening 60. Inlet air flows through partial passage 72 into combustion chamber 14 through fuel burner inlet opening 62 and ceramic sleeve opening 64. Damper door 66, hinged to face plate 68, is rotatable about a hinged axis. Ceramic sleeve opening 64 determines the amount of inlet air which will be preheated and vortexed into flame front 20. Heater air within chamber 14 has a higher temperature than ambient external air and, therefore, will have a lower pressure to promote a continuous flow of external air through passage 72 into chamber 14. Proper percentages of air flowing through fuel burner inlets 62 and ceramic sleeve opening 64 may be determined, and damper door 66 automatically adjusted to promote the most efficient burning of fuel within chamber 14. Angled vanes 52 may be placed within face plate 68 or on side walls of ceramic sleeve 54 as shown in FIG. 7. Inlet air flowing through ceramic sleeve 54 is vortexed through angled vanes 52 in a direction countercurrent to flame front 20. Ceramic sleeve 54 extends longitudinally and in the same direction as fuel burner 16, however, vortexing of inlet air provides for a compression of flame front 20 in a manner similar to the counter current flow described previously.
Another embodiment of the invention is shown in FIG. 6 where preheating sleeve 54 is spatially positioned similar to that shown in the embodiment described by FIG. 5. Induced draft is formed in this embodiment by fan 24 which inputs air into chamber 14 under high pressure. Sleeve 54 located below fuel burner 16 in furnace side wall 18 extends longitudinally and in the same direction as flame front 20. Air flowing longitudinally through preheating sleeve 54 is vortexed in a manner similar to that described for the embodiment of FIG. 5 and is driven into the flame front to compress and cause turbulent flow which increases heat transfer efficiency yielding a higher heat dissipation capability from flame front 20.
In the invention as described, higher temperatures in the combusting zone are obtained by heating a predetermined proportional amount of secondary air within furnace 12. The introduction of secondary air in the manner described produces more rapid and complete combustion within the flame envelope having a more uniform temperature throughout the combusting zone than was found in previous systems. Temperature gradients from a hot to cold zone within chamber 14 produce vast quantifies of pollutants in the form of smoke and soot. In boiler applications a reduction in fuel consumption is found through the use of system 10 where a major proportion of radiant heat release is captured by steam generating tubes which may be exposed to the flame.
The shaping and directing of heated air in a vortexed and countercurrent manner reduces the requirement for high excess air to be maintained in order to provide a clean flame. The lower requirement for clean, efficient combustion with less excess air will result in a further reduction of heat losses and higher combustion efficiency. The forcing of air into chamber 14 with a controlled volume and velocity having a rotational direction into the main flame front concentrates the hydrocarbons in the highest temperature zone which assists in a high radiant heat release. Additional savings are realized in the reduction of soot, blowing requirements, cleaner tube surfaces, and maintenance of a maximum degree of convection gas heat transfer.
What is claimed is:
1. A supplemental air supply assembly to increase fuel combustion efficiency within a combustion chamber having a fuel burner forming a flame envelope having a surface area with a longitudinal and a transverse direction comprising:
high pressure air inlet means extending through a wall of said combustion chamber for decreasing said surface area of said flame envelope thereby increasing the radiant heat transport to enclosing internal boundaries of said combustion chamber, said high pressure air having a direction substantially opposing said longitudinal direction of said flame envelope; and,
means for vortexing said high pressure air for encompassing said flarne envelope surface area.
2. The assembly as recited in claim 1 wherein said vortexing means includes helical dispersion means to induce said streamline air flow helically about said longitudinal dimension of said flame envelope.
3. The assembly as recited in claim 1 wherein said air inlet means is positioned within said wall of said combustion chamber longitudinally opposing said flame envelope.
4. The assembly as recited in claim 1 wherein said air inlet means includes means for providing air flow pressure internal to said combustion chamber in excess of said ambient air pressure.
5. The assembly as recited in claim 1 wherein said air inlet means includes:
blower means external to said combustion chamber for producing a high pressure air flow; and,
conduit means coupled to said blower means and said wall of said combustion chamber to direct a predetermined quantity of said high pressure air into said combustion chamber.
6. The assembly as recited in claim wherein there is provided a damping device for controllably restricting the internal passage of said conduit means to regulate the amount of high pressure air flowing through said conduit means.
7. The assembly as recited in claim 5 wherein said conduit means includes:
a. damping motor means;
b. an air flow blocking panel angularly oriented with respect to said conduit means passage to restrict the cross-sectional area of said passage responsive to said damping motor means actuation; and,
c. a temperature sensing element connected on opposing ends to said damping motor means and internal to said combustion chamber respectively, said temperature sensing element to measure said air flow temperature within said chamber and actuate said damping motor means.
8. The assembly as recited in claim 5 wherein said conduit means is secured to said combustion chamber wall longitudinally opposed to said flame envelope to produce said air flow in a direction countercurrent to said longitudinal dimension.
9. The assembly as recited in claim 5 wherein said conduit means includes a plurality of angled vanes secured to an inner diameter of said conduit means to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
10. The assembly as recited in claim 9 includes an elbow section to transform initially directed air flow from said blower means to a longitudinal flow within said combustion chamber.
11. The assembly as recited in claim 10 wherein said elbow sectional element includes a tube extending in said longitudinal dimension, said tube being fixedly secured central to said passage of said conduit means and passing external thereto through a wall of said elbow sectional element, said tubing having a central through opening sealed with a high temperature transparent material external to said elbow sectional element for visual observation internal to said combustion chamber.
12. The assembly as recited in claim 9 wherein said tube includes a plurality of formed vanes secured to the periphery of said tube within said passage of said conduit means to direct the flow of said air helically about said longitudinal dimension of said flame envelope.
13. The assembly as recited in claim 1 including preheating air means rigidly secured to said air inlet means extending within said combustion chamber in said lon gitudinal dimension directed toward said flame envelope to heat said inlet air within said combustion chamber prior to entry into said flame envelope.
14. The assembly as recited in claim 13 wherein said preheating air means includes a tubular sleeve having a through opening, said sleeve being coaxially displaced with respect to said air inlet means.
15. The assembly as recited in claim 14 wherein said sleeve includes a first end fastened to said air inlet means and a second end having a decreased nozzle opening to increase the velocity of said air flow.
16. The assembly as recited in claim 14 wherein said sleeve is constructed of a high thermally conductive material to permit transport of heat from said combustion chamber to said air flowing therethrough.
17. The assembly as recited in claim 14 wherein said preheating air sleeve is constructed of silicon carbide.
18. The assembly as recited in claim 14 wherein said preheating air sleeve includes a plurality of helically extended air flow vanes secured to an internal diameter thereof to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
19. The method of increasing radiant heat transport from a flame envelope contained within a combustion chamber having a fuel burner, said flame envelope defining a surface area having a longitudinal and transverse direction, said flame envelope surface area to be decreased, including the steps of a. positioning a high pressure inlet air flow in a streamline contour substantially opposing in direction said flame envelope longitudinal direction; and b. vortexing said high pressure inlet air flow to produce a streamline air flow contour in said trans- 1 verse direction of said flame envelope.

Claims (20)

1. A supplemental air supply assembly to increase fuel combustion efficiency within a combustion chamber having a fuel burner forming a flame envelope having a surface area with a longitudinal and a transverse direction comprising: high pressure air inlet means extending through a wall of said combustion chamber for decreasing said surface area of said flame envelope thereby increasing the radiant heat transport to enclosing internal boundaries of said combustion chamber, said high pressure air having a direction substantially opposing said longitudinal direction of said flame envelope; and, means for vortexing said high pressure air for encompassing said flame envelope surface area.
2. The assembly as recited in claim 1 wherein said vortexing means includes helical dispersion means to induce said streamline air flow helically about said longitudinal dimension of said flame envelope.
3. The assembly as recited in claim 1 wherein said air inlet means is positioned within said wall of said combustion chamber longitudinally opposing said flame envelope.
4. The assembly as recited in claim 1 wherein said air inlet means includes means for providing air flow pressure internal to said combustion chamber in excess of said ambient air pressure.
5. The assembly as recited in claim 1 wherein said air inlet means includes: blower means external to said combustion chamber for producing a high pressure air flow; and, conduit means coupled to said blower means and said wall of said combustion chamber to direct a predetermined quantity of said high pressure air into said combustion chamber.
6. The assembly as recited in claim 5 wherein there is provided a damping device for controllably restricting the internal passage of said conduit means to regulate the amount of high pressure air flowing through said conduit means.
7. The assembly as recited in claim 5 wherein said conduit means includes: a. damping motor means; b. an air flow blocking panel angularly oriented with respect to said conduit means passage to restrict the cross-sectional area of said passage responsive to said damping motor means actuation; and, c. a temperature sensing element connected on opposing ends to said damping motor means and internal to said combustion chamber respectively, said temperature sensing element to measure said air flow temperature within said chamber and actuate said damping motor means.
8. The assembly as recited in claim 5 wherein said conduit means is secured to said combustion chamber wall longitudinally opposed to said flame envelope to produce said air flow in a direction countercurrent to said longitudinal dimension.
9. The assembly as recited in claim 5 wherein said conduit means includes a plurality of angled vaneS secured to an inner diameter of said conduit means to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
10. The assembly as recited in claim 9 includes an elbow section to transform initially directed air flow from said blower means to a longitudinal flow within said combustion chamber.
11. The assembly as recited in claim 10 wherein said elbow sectional element includes a tube extending in said longitudinal dimension, said tube being fixedly secured central to said passage of said conduit means and passing external thereto through a wall of said elbow sectional element, said tubing having a central through opening sealed with a high temperature transparent material external to said elbow sectional element for visual observation internal to said combustion chamber.
12. The assembly as recited in claim 9 wherein said tube includes a plurality of formed vanes secured to the periphery of said tube within said passage of said conduit means to direct the flow of said air helically about said longitudinal dimension of said flame envelope.
13. The assembly as recited in claim 1 including preheating air means rigidly secured to said air inlet means extending within said combustion chamber in said longitudinal dimension directed toward said flame envelope to heat said inlet air within said combustion chamber prior to entry into said flame envelope.
14. The assembly as recited in claim 13 wherein said preheating air means includes a tubular sleeve having a through opening, said sleeve being coaxially displaced with respect to said air inlet means.
15. The assembly as recited in claim 14 wherein said sleeve includes a first end fastened to said air inlet means and a second end having a decreased nozzle opening to increase the velocity of said air flow.
16. The assembly as recited in claim 14 wherein said sleeve is constructed of a high thermally conductive material to permit transport of heat from said combustion chamber to said air flowing therethrough.
17. The assembly as recited in claim 14 wherein said preheating air sleeve is constructed of silicon carbide.
18. The assembly as recited in claim 14 wherein said preheating air sleeve includes a plurality of helically extended air flow vanes secured to an internal diameter thereof to direct said air flow in a transverse direction with respect to said longitudinal dimension of said flame envelope.
19. The method of increasing radiant heat transport from a flame envelope contained within a combustion chamber having a fuel burner, said flame envelope defining a surface area having a longitudinal and transverse direction, said flame envelope surface area to be decreased, including the steps of a. positioning a high pressure inlet air flow in a streamline contour substantially opposing in direction said flame envelope longitudinal direction; and b. vortexing said high pressure inlet air flow to produce a streamline air flow contour in said transverse direction of said flame envelope.
20. The method as recited in claim 19 including the step of: preheating said high pressure inlet air within said combustion chamber subsequent to said introduction and prior to said impingement of said high pressure inlet air on said flame envelope, said preheating for raising the temperature of said high pressure inlet air thereby increasing the fuel combustion efficiency.
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US2022512A (en) * 1930-12-31 1935-11-26 Gen Electric Combustion method and apparatus
GB387751A (en) * 1931-09-23 1933-02-16 John Hamilton Improvements relating to gaseous and liquid fuel burning apparatus
US2368827A (en) * 1941-04-21 1945-02-06 United Carbon Company Inc Apparatus for producing carbon black
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US3876362A (en) * 1973-04-23 1975-04-08 Yasuo Hirose Method of combustion
US5601425A (en) * 1994-06-13 1997-02-11 Praxair Technology, Inc. Staged combustion for reducing nitrogen oxides
US6109911A (en) * 1997-10-10 2000-08-29 Kvaerner Pulping Oy Method and arrangement for optimizing oxidation during burning of gaseous and liquid fuels
GB2412165A (en) * 2004-03-16 2005-09-21 Hon Tech Inc A Method and Apparatus for Modifying the Appearance of a Flame
US7160103B2 (en) 2004-03-16 2007-01-09 Hni Technologies Inc. Method and apparatus for modifying the path of a flame
EP3798513A1 (en) * 2019-09-26 2021-03-31 ÖKOFEN Forschungs- und Entwicklungsgesellschaft m.b.H. Heating device

Also Published As

Publication number Publication date
CA966059A (en) 1975-04-15
GB1370135A (en) 1974-10-09

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