BURNER AND COMBUSTION METHOD FOR A BURNER

Abstract

A burner designed to be fitted in a combustion chamber, the burner including: a central nozzle configured to have an oxidizer and fuel supply; several peripheral nozzles configured to have an oxidizer and fuel supply and which each have at least one upstream fuel injector in order to pre-mix the fuel and the oxidizer in the nozzle; at least one oxidizer input connected to the said central and/or peripheral nozzles; wherein peripheral nozzles each have a flame stabilizer located at the end of the peripheral nozzle designed to exit into the combustion chamber, as well as a tip injector to inject fuel at the end of the peripheral nozzle.

Claims

1. A burner designed to be fitted in a combustion chamber, the burner including having at least: a central nozzle configured to have an oxidizer and fuel supply; several peripheral nozzles configured to have an oxidizer and fuel supply and which each have at least one upstream fuel injector in order to pre-mix the fuel and the oxidizer in the said nozzle; at least one oxidizer input operably connected to the central and/or peripheral nozzles; the peripheral nozzles each have a flame stabilizer located at the end of the peripheral nozzle designed to exit in the combustion chamber, as well as a tip injector to inject fuel at the end of the peripheral nozzle.

2. A burner, as claimed in claim 1, wherein the flame stabilizer has a surface area of between 40 and 70% of the associated peripheral nozzle's cross section.

3. A burner as claimed in claim 1 wherein the central nozzle includes a central injector configured to inject fuel, and the injector includes radial injection openings that are orthogonal to the burner's main axis (A).

4. A burner as claimed in claim 1 wherein the central nozzle includes an oxidizer injector which has oxidizer injector openings that are straight and almost parallel to the burner's main axis.

5. A burner as claimed in claim 1 including injection lances configured to inject fuel into the periphery of the central nozzle and/or the peripheral nozzles.

6. A combustion process for a burner according to any one of the preceding claim 1, the burner is configured to burn a total flow of fuel noted Q.sub.T circulating through the burner and in which the central nozzle is configured to deliver a fuel flow C, all the upstream injectors are configured to deliver a fuel flow P, all the tip injectors are configured to deliver a fuel flow S, the fuel flow P representing at the maximum 85% of the total fuel flow Q.sub.T, the fuel flow C representing at the maximum 10% of the total fuel flow Q.sub.T, the fuel flow S representing at the maximum 15% of the total fuel flow Q.sub.T.

7. A combustion process according to claim 6, wherein the fuel flow P represents at least 70% of the total fuel flow Q.sub.T, the C fuel flow represents at least 5% of the total fuel flow Q.sub.T.

8. A combustion process according to claim 6 wherein the fuel flow S represents at least 1% of the total fuel flow Q.sub.T.

9. A combustion process according to claim 8 wherein all the injection lances deliver a fuel flow G representing at the maximum 20% of the total fuel flow Q.sub.T.

10. A combustion process according to claim 6, wherein the oxidizer includes a maximum of 35% of combustion gases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0086] The invention will be better understood and other purposes, details, characteristics, and advantages of the invention will appear more clearly on reading the following description given by way of an illustrating and non-limiting example and with reference to the accompanying drawings, in which:

[0087] FIGS. 1a, 1b, 2a and 2b are schematic cross sectional views of a burner fitted to a combustion chamber according to an embodiment of the invention.

[0088] FIG. 3 a perspective schematic view of a burner according to the invention;

[0089] FIGS. 4 to 6 are highly schematic transverse and longitudinal cross section views of burners from FIG. 3.

DETAILED DESCRIPTION

[0090] FIG. 3 is a schematic representation of a burner 11 according to the invention designed to be fitted in a combustion chamber with reduced dimensions for example.

[0091] Burner 11 has a main body 13, for example of an almost cylindrical shape, in which an oxidizer input 13a is created. Oxidizer input 13a also generally includes a regulation device, such as a flap, to regulate the quantity of oxidizer entering the main body 13. In this example, the oxidizer used is air, but any oxidizer that allows combustion can be used.

[0092] Burner 11 also includes a fuel supply resource (not shown on FIG. 3), in particular a gas supply, such as methane propane, as well as one or more nozzles 15 and 17. More particularly, burner 11 has a central nozzle 15 and so-called peripheral nozzles 17 arranged around central nozzle 15.

[0093] Central nozzle 15 is designed to create a radial flame, whereas the peripheral nozzles 17 are designed to create mainly axial flames. The radial flame created by central nozzle 15 is also intended to provide at least part of the ignition between the peripheral nozzles 17.

[0094] Generally, the peripheral nozzles 17 are arranged circularly around the central nozzle 15 according to a diameter φ.sub.P, the diameter φ.sub.P being identified by the peripheral injection diameter described previously.

[0095] One can also note that the different burner nozzles have at least one flow flue, as well as one or more oxidizer injectors, fuel injectors or oxidizer/fuel injectors.

[0096] Thus, the flow flue has an end part connected to oxidizer input 13a, and a second end coming out in a zone in which the combustion occurs and in which the flame is generated.

[0097] More particularly, all the nozzles, central 15 and peripheral 17 lead to a tip 11a designed to exit into the combustion chamber when the burner is in the fitted position, a zone also known as the burner tip. This tip or zone is the place where combustion occurs (it is a zone in which the fuel and oxidizer that have been brought by the different nozzles will come together in order to generate a combustion reaction). A tip (or nose) can also be defined for each nozzle 15 and 17, all the nozzle ends defining the burner tip 11a.

[0098] Burner 11 has a main axis A (or central), which is, for example, the rotating axis of the central nozzle 15 (it can also be the burner's rotating axis). Each peripheral nozzle 17 rotating axis is in a circle of diameter φ.sub.P, of which the centre is part of the central axis A.

[0099] Furthermore, in the shown embodiment, burner 11 has fuel injection lances 19 arranged on the periphery, towards the outside, of the peripheral nozzles 17.

[0100] The fuel lances 19 are preferably arranged in a circular manner, between or around the peripheral nozzles 17. One can however note that the presence of injection lances in the burner is only an option in an embodiment of the invention and that the injection lances 19 are not required for the burner 11 to operate properly.

[0101] On can thus define a circle of diameter φ.sub.B in which the central nozzle 15, the peripheral nozzles 17 and the injection lances 19, when burner 11 has them, are to be found, the diameter φ.sub.B being the burner 11 diameter (detailed previously).

[0102] Furthermore, when burner 11 is fitted in a combustion chamber, the combustion chamber is over the diameter φ.sub.B circle. One can then define an equivalent combustion chamber diameter φ.sub.E corresponding to a circle inside the combustion chamber walls and which encircles the diameter φ.sub.B circle.

[0103] One can thus see, more particularly visible in FIG. 3, that the central nozzle 15 is in two parts: [0104] a central fuel injector 151 configured to radially inject fuel into a combustion chamber (radially relative to the main axis A of the central nozzle 15); [0105] an oxidizer injector 153 surrounding the central injector 151.

[0106] The central injector 151 protrudes, is of an almost cylindrical shape, and has several openings 157.

[0107] FIG. 4 is a schematic longitudinal cross section view of the central nozzle 15 of the burner in FIG. 3.

[0108] The central nozzle 15 has a flow flue 154 that has a first 154a and second 154b end, as well as a fuel supply flue 152 connecting the terminal part of the central injector 151 to a fuel source.

[0109] The first end 154a of the central nozzle 15 is connected to the oxidizer input 13a in order to allow the oxidizer to circulate inside the flue 154. The second end 154b leads to the tip 11a of the burner when the burner is fitted in the combustion chamber.

[0110] The details of the terminal part, i.e. the part located near the combustion tip 11a of burner 11, of the central nozzle 15 are shown in FIGS. 5a to 5c and will be detailed below using these figures.

[0111] Thus, FIGS. 5a to 5c are very schematic views of the central injector 151, respectively in transverse and longitudinal cross sections. The openings 157 are radial, arranged circularly around main axis A (which is also the rotating axis of central nozzle 15) and oriented orthogonally to the main axis A of burner 11.

[0112] The oxidizer injector 153 has several openings 159 mainly oriented along main axis A (i.e. the normal at the passage cross section of opening 159 is almost parallel to main axis A).

[0113] Openings 157 and 159 respectively of the central injector 151 and the oxidizer injector 153 are preferably straight.

[0114] As for FIG. 6, it is a highly schematic view of a longitudinal cross section of a peripheral nozzle 17.

[0115] As explained previously, peripheral nozzle 17 has a flow flue 171 that has a first and second tip 171b, as well as two fuel injectors respectively referred to as upstream (or pre-mix) 172 and tip 173.

[0116] The first end of peripheral nozzle 17 is connected to the oxidizer input 13a in order to allow the oxidizer to circulate inside the flue 171. The second tip 171b leads to the burner combustion tip 11a.

[0117] The upstream injector 172 is placed in flow flue 171 and is configured to inject fuel so that it mixes with the oxidizer, there is therefore a fuel-oxidizer pre-mix that occurs in peripheral nozzle 17. The pre-mix occurs in the time needed for the fuel to reach the second tip 171b.

[0118] Amongst other things, the peripheral nozzle 17 has a flame stabilizer 175. The flame stabilizer 175, usually placed at the second tip 171b, has a central part 175a placed at the centre of peripheral nozzle 17, more particularly at the centre of the flow flue 171.

[0119] The tip injector 173 is configured to inject fuel at the peripheral nozzle 17 tip, which also corresponds to the burner tip 11a. More particularly, the tip injector 173 leads to the flame stabilizer 175, for example by passing through its centre (which is also the centre of peripheral nozzle 17).

[0120] The upstream injector 172 and the tip injector 173 can be separate and independent fuel injectors, but can be, as in this embodiment, connected to each other, the tip injector 173 being connected fluidly to the upstream injector 172.

[0121] One can also note that the flame stabilizer 175 is held in the centre of peripheral nozzle 17 using the tip injector 173 (the injector 173 is used as a support for the stabilizer 175).

[0122] Thus, when burner 11 is operating, oxidizer enters through the oxidizer input 13a and circulates in the central nozzle 15 and the peripheral nozzles 17. The oxidizer comes out of the burner 11 through openings 159 of the oxidizer injector 153 and the peripheral nozzles 17, using the two tips 171b by passing around the flame stabilizers 175.

[0123] Furthermore, burner 11 delivers total a flow of fuel Q.sub.T.

[0124] The central nozzle 15 delivers a fuel flow noted C, all the upstream injectors 172 for the peripheral nozzles 17 have a fuel flow noted P, all the tip injectors 173 for the peripheral nozzles 17 have a fuel flow noted S and all the peripheral lances 19 deliver a fuel flow noted G.

[0125] Thus, the total fuel flow Q.sub.T circulating through the burner 11 is the sum of the flows indicated above: C, P, S and G.

[0126] One will however note that the presence of the injection lances is optional and that if the burner has no injection lances, the total fuel flow Q.sub.T circulating through the burner 11 is the sum of flows C, P and S.

[0127] The combustion process according to the invention has at least: [0128] a fuel flow P of between 70 and 85% of the total fuel flow Q.sub.T; [0129] a fuel flow C of between 5 and 10% of the total fuel flow Q.sub.T; [0130] a fuel flow S of between 1 and 15% of the total fuel flow Q.sub.T, and preferably between 7 and 15% of the total fuel flow Q.sub.T.

[0131] Furthermore, when burner 11 has injection lances 19, all the injection lances deliver a fuel flow G which represents a maximum of 20% of total fuel flow Q.sub.T, and preferably less than 10% of the total fuel flow Q.sub.T.

[0132] Furthermore, the oxidizer used in the combustion process contains a maximum of 35% of combustion gases (i.e. a %.sub.FGR less than or equal to 35%), and preferably between 20 and 35% of combustion gases (i.e. an %.sub.FGR included between 20 and 35%).