TUBULAR BURNER

Abstract: A tubular burner has a body (1) comprising a diffuser portion (3, 8, 13, 22) over the surface of which openings are distributed for discharging a mixture of air and fuel fed to said body (1) through a Venturi tube (2) arranged at the side of said body (1), said body (1) has a cross section shaped in such a way that the distance between the outer wall of the Venturi tube (2) and the inner wall of said body, when measured in a radial direction of the Venturi tube (2), has a first value substantially constant over a first portion of the perimeter of the Venturi tube (2) and a second value greater than said first value over a second portion of said perimeter.

Description: Tubular burner The invention concerns a tubular burner provided with a Venturi tube arranged at the inside of the body of the burner, a mixture of air and fuel being fed to the burner through the Venturi tube. The mixture is discharged from the body of the burner through openings made on a diffuser portion of the body and is then caused to bum. Form the prior art tubular burners are known having a tubular body, with circular or elliptic cross section, and a Venturi tube coaxial with the burner body. A limited volume is defined at the inside of the burner body between the inner surface of the burner body and the outer surface of the Venturi tube. The flow of the air and fuel mixture, which is discharged from the Venturi tube, must reverse its own direction of flow in order to enter said limited volume and reach said openings. Said reversal of flow direction causes high losses of energy and considerable variations of the values of the characterising parameters of the mixture discharged from said openings, such as pressure, speed, air/fuel rate, over said diffuser portion. Said variations leads to incorrect combustion of the mixture of air and fuel, which is not acceptable and can be remedied with great difficulty. Said incorrect combustion may cause, for instance, flame detachment or an increase of the harmful emission of the burner. Someone has tried to eliminate said drawbacks by arranging the Venturi tube in such a position that the axis of the Venturi tube is separate from the axis of the burner body, particularly by shifting the Venturi tube downward with respect to the diffuser portion of the burner body. However, said solution has proved to be unsatisfactory because of an increase of losses of energy at the inside of the burner body caused by the asymmetric position of the Venturi tube. A further drawback in the known tubular burners, caused by variations of the values of the characterising parameters of the air-fuel mixture discharged from said openings, is a local overheating of the surface of the burner body. Said local overheating is caused by the fumes produced by the combustion that lick the surface of the burner body near said diffuser portion and transmit heat to the burner body by convection. The present invention intends to overcome the drawbacks mentioned above. According to the present invention, there is provided a tubular burner having a body on the surface of which openings are made for discharging a mixture of air and fuel fed to said body through a Venturi tube arranged at the inside of said body, characterised in that said body has a cross section shaped in such a way that the distance between the outer wall of the Venturi tube and the inner wall of said body, when measured in a radial direction of said Venturi tube, has a first value substantially constant in a first portion of the perimeter of the Venturi tube and a second value greater than said first value in a second portion of said perimeter That makes possible to make available for the flow of said mixture discharged from the Venturi tube a volume wide enough to allow said flow to reverse the direction of its motion between the outlet of the Venturi tube and the openings made in the burner body without causing variations of the values of the characterising parameters of said mixture across said diffuser portion, when the mixture is discharged from said openings The invention will now be described, by way of non-limiting example, with reference to the enclosed drawings, in which Figure 1 is a cross section of a first embodiment of a burner according tot he invention, Figure 2 is a side view of the burner of Figure 1 , Figure 3 is a cross section of a second embodiment of a burner according to the invention, Figure 4 is a side view of the burner of Figure 3, Figure 5 is a cross section of a third embodiment of a burner according to the invention, Figure 6 is a side view of the burner of figure 5, Figure 7 is a cross section of a fourth embodiment of a burner according tot he invention, Figure 8 is a side view of the burner of Figure 7 With reference to Figure 1 , the reference numeral 1 indicates the body of a burner according to the invention, inside which a Venturi tube is arranged A mixture of air and fuel is fed into the burner body 1 through the Venturi tube and is then discharged through openings distributed, for instance, over an upper diffuser portion 3 of the burner body The burner body 1 has a cross section shaped as a triangle, for instance an isosceles triangle, having a base 15, sides 16, an upper vertex 3 and lower vertices 18, all the vertices 3 and 18 being rounded The Venturi tube 2 is arranged at the inside of the burner body 1 in such a way that the distance between the outer surface of the Venturi tube 2 and the inner surface of the burner body 1 is substantially constant across a significant portion of the perimeter of the Venturi tube 2 and increases progressively across the remaining portion of the perimeter until it reaches a maximum value in the region of the diffuser portion 3 of the burner body 1 A chamber 19 is defined between upper portion of the Venturi tube 2 and said diffuser portion 3 of the burner body 1 , the mixture discharged from the Venturi tube 2 passing through said chamber 19 The presence of the chamber 19 makes possible to decrease the losses of energy suffered by the mixture discharged from the Venturi tube 2, when the mixture reverses the direction of its own motion In addition, when the mixture passes through said chamber 19, before being discharged through the openings made in the burner body 1 , the characterising parameters of the mixture tends to become uniform and the speed vector of the mixture tends to become substantially perpendicular to the burner body 1 The uniformity of the characterising parameters of the mixture may be further improved by providing laminar flow generating means 4 between the Venturi tube 2 and the diffuser portion 3 of the burner body 1 When said mixture passes through said laminar flow generating means 4, a substantially laminar flow of the mixture is generated Said laminar flow generating means 4 may consist, for instance, of a mesh element 4, shaped as a sector of a cylindrical surface, In addition, the laminar flow generating means 4 may consists of a perforated plate element, or a honeycomb shaped element, or baffle means, etc Figures 3 and 4 show a second embodiment of the present invention in which the cross section of the burner body 1 comprises a lower portion 5 having a substantially circular shape and an upper portion 6 consisting of a pair of sides converging upwards and connected by a curvilinear stretch 8 Said curvilinear stretch 8 constitutes the diffuser portion of the burner body 1 over which the openings for discharging said mixture of air and fuel are distributed The lower portion 5 of said cross section extends over an angle of more than 180° The distance between the outer wall of the Venturi tube 2 and the the inner wall of the burner body 1 in said lower portion 5 is substantially constant, whilst said distance increases progressively in said upper portion 6 up to a maximum value in the central part of said curvilinear portion 8 At inside of said upper portion 6 a chamber 9 is defined having the same purpose as the chamber 19 previously described Laminar flow generating means 4 may be interposed between the Venturi tube 2 and the chamber 9 Figures 5 and 6 show a third embodiment of a burner according to the invention, in which the cross section of the burner body 1 comprises a lower portion 10 having a substantially circular shape and an upper portion 11 consisting of a pair of substantially vertical sides 12, the upper ends of which are connected by a curvilinear stretch 13 Said curvilinear stretch 13 constitutes the diffuser portion of the burner body 1 over which the openings for discharging the mixture of air and fuel are distributed The lower portion 10 of said cross section extends over an angle of more than 180° The distance between the outer wall of the Venturi tube 2 and the the inner wall of the burner body 1 in said lower portion 10 is substantially constant, whilst said distance increases suddenly in said upper portion 11 up to a maximum value in the central part of said curvilinear portion 13 At inside of said upper portion 11 a chamber 14 is defined having the same purpose as the chambers 9 and 19 previously described Laminar flow generating means 4 may be interposed between the Venturi tube 2 and the chamber 14 Figures 7 and 8 show a fourth embodiment of a burner according to the invention, in which the cross section of the burner body 1 comprises a lower portion 20 comprising a pair of substantially rectilinear sides 26 the lower ends of which are connected by a curvilinear stretch 25, and an upper portion 24 consisting of a pair of substantially vertical sides 21 , the upper ends of which are connected by a further curvilinear stretch 22 Said further curvilinear stretch constitutes the diffuser portion of the burner body over which the openings for discharging the mixture of air and fuel are arranged The lower ends of the substantially vertical sides 21 are connected to corresponding ends of the rectilinear sides 26 by means of still further curvilinear stretches 27 The Venturi tube 2 may be arranged at the inside of said lower portion 20 in a symmetric or asymmetric position In a still further embodiment of a burner according to the invention, not shown, the lower portion 20 of the burner body may have an elliptic shape At inside of said upper portion 24 a chamber 23 is defined having the same purpose as the chambers 9, 14 and 19 previously described In all the embodiments shown, the slope of the sides of burner body 1 , in the regions near the diffuser portion 3, 8, 13, 22 of the burner body, makes possible to prevent the fumes produced by the combustion from licking the surface of the burner body in said regions, thus causing overheating.

Claims: CLAIMS 1. A tubular burner having a body (1 ) comprising a diffuser portion (3, 8, 13, 22) over the surface of which openings are distributed for discharging a mixture of air and fuel fed to said body (1 ) through a Venturi tube (2) arranged at the inside of said body (1 ), characterised in that said body (1 ) has a cross section shaped in such a way that the distance between the outer wall of the Venturi tube (2) and the inner wall of said body, when measured in a radial direction of the Venturi tube (2), has a first value substantially constant over a first portion of the perimeter of the Venturi tube (2) and a second value greater than said first value over a second portion of said perimeter. 2. A tubular burner according to claim 1 , wherein said second value increases from the ends of said second portion towards the centre of said second portion. 3. A tubular burner according to claim 1 , or 2, wherein a chamber (9; 14; 19; 23) is defined in said second portion between the outer wall of the Venturi tube (2) and the inner wall of said body (1 ), said mixture passing through said chamber before being discharged through said openings. 4. A tubular burner according to claim 3, wherein said chamber (9; 14; 19; 23) is delimited at its bottom by laminar flow generating means (4) for generating a substantially laminar flow of said mixture. 5. A tubular burner according to claim 4, wherein said laminar flow generating means comprises mesh means (4). 6. A tubular burner according to claim 5, wherein said mesh means (4) has a curvilinear shape. 7. A tubular burner according to any of preceding claims, wherein said first portion extends over an angle of more than 180°. 8. A tubular burner according to any of preceding claims, wherein said cross section is shaped as a triangle with rounded vertices. 9. A tubular burner according to claim 8, wherein said triangle is an isosceles triangle. 10. A tubular burner according to any of claims 1 to 7, wherein said cross section comprises a lower portion (5) having a substantially circular shape and an upper portion (6) comprising a pair of sides (7) converging upwards, the upper ends of said sides (7) being connected by a curvilinear stretch (8). 11. A tubular burner according to any of claims 1 to 7, wherein said cross section comprises a lower portion (10) having a substantially circular shape and an upper portion (11 ) comprising a pair of substantially vertical sides (12), the upper ends of said sides (12) being connected by a curvilinear stretch (13). 12. A tubular burner according to claim 10, or 11 , wherein said lower part (5; 10) extends an angle of more than 180°. 13. A tubular burner according to any of claims 1 to 6, wherein said cross section comprises a lower portion (20) substantially elliptic and an upper portion comprising a pair of substantially vertical sides (21 ) the upper ends of which are connected by a curvilinear stretch (22). 14. A tubular burner according to any of claims 1 to 6, wherein said cross section comprises a lower portion (20) provided with a pair of substantially rectilinear sides (26) the lower ends of which are connected by a curvilinear stretch (25) and an upper portion (24) comprising a pair of substantially vertical sides (21 ) the upper ends of which are connected by a further curvilinear stretch (22). 15. A tubular burner according to claim 14, wherein the lower ends of said substantially vertical sides (21 ) are connected to corresponding ends of said rectilinear sides (26) by means of still further curvilinear stretches (27).

Inventors: BUCCILLI GIORGIO, FOGLIANI GIUSEPPE, BUCCILLI, GIORGIO, FOGLIANI, GIUSEPPE
Applicants: BUCCILLI GIORGIO, FOGLIANI GIUSEPPE, WORGAS BRUCIATORI SRL, BUCCILLI, GIORGIO, FOGLIANI, GIUSEPPE, WORGAS BRUCIATORI S.R.L.
Application year: 1999
Main classification: F23D14
IPC codes: F23D14