Patent Application
20250052417
The invention relates to the field of burners arranged in combustion chambers with low nitrogen oxide emissions.
There are numerous applications wherein burners are used in conjunction with cramped combustion chambers. This is the case for boilers, for example.
In said combustion chambers where the volume is limited, the furnace (the site of the combustion) is small and has a particularly high volume load.
Under these difficult conditions, controlling nitrogen oxide emissions is a major challenge.
In order to reduce nitrogen oxide emissions, manufacturers have introduced flue gas recirculation systems. The function of said systems is to recycle some of the flue gas in order to deplete the oxidant of oxygen, thereby reducing the production of nitrogen oxides.
Although these systems have proven their effectiveness, they also have other drawbacks.
The flue gas recirculation function adds complexity to the architecture of said installations. In fact, they must contain a network of specific ducts and a suitable ventilation device. The installations are then bulkier and more expensive to purchase.
The flue gas recirculation function leads to higher energy consumption, as the ventilation device is energy-intensive and consumes electricity. In addition, the combustion reaction is affected by the recirculated fumes, which reduces the efficiency of the installation.
The challenge for users is therefore to overcome these disadvantages by having installations without flue gas recirculation systems, while benefiting from low nitrogen oxide emissions.
To this end, firstly a premixing burner is proposed, intended to be mounted in a combustion chamber, said burner being configured to be supplied with oxidant and with fuel, said burner comprising:
The applicant has determined that a peripheral angle α within this range reduces nitrogen oxide emissions without the use of a recirculation system.
Various additional features can be provided alone or in combination:
Secondly, an installation is proposed comprising a burner as previously disclosed and a combustion chamber delimited laterally by a wall, said wall comprising an opening through which the burner can be inserted into said combustion chamber, an installation wherein a longitudinal end of the peripheral shroud located in the combustion chamber is arranged at a first insertion length K1 measured from the opening and along the longitudinal central axis.
Various additional features can be provided alone or in combination:
Further features and advantages of the invention will become apparent on reading the following detailed description, which can be understood with reference to the accompanying drawing, wherein:
The burner 2 is of the premixing type. This means that the oxidant and the fuel are mixed inside the burner 2. The burner 2 is therefore configured to be supplied with both oxidant and fuel. The burner 2 is suitable and is inserted into the combustion chamber 3.
The burner 2 comprises:
The central shroud 4 is positioned inside the peripheral shroud 5 so as to form an annular space 6 therebetween. The burner 2 comprises at least one injection of fuel and at least one injection of oxidant into the annular space 6. The fuel and oxidant are thus premixed in the annular space 6.
The peripheral shroud 5 comprises a second angled portion 8. The second angled portion 8 defines a peripheral angle α with a central longitudinal axis C of burner 2.
The central shroud 4 comprises a first angled portion 7. The first angled portion 7 defines a central angle β with the central longitudinal axis C. The central angle β has a value between 0° and α°.
As can be seen in
Said burner 2 reduces the production of nitrogen oxides, notably due to the peripheral and central angles α, β defining the convergent zone 26.
Advantageously, the peripheral and central angles α and β are measured counterclockwise or trigonometrically. Thus, it is possible to obtain the convergent zone 26.
Advantageously, the peripheral angle α is between 30° and 70°. The applicant has determined that a peripheral angle α within this range reduces nitrogen oxide emissions without the use of a recirculation system.
Advantageously, the central shroud 4 comprises a first linear portion 9. The first linear portion 9 is substantially parallel to the central longitudinal axis C and is located upstream of the first angled portion 7 in the direction of travel of the oxidant.
The direction of travel of the oxidant is represented by an arrow F on
The peripheral shroud 5 is provided with a second linear portion 10. The second linear portion 10 is substantially parallel to the central longitudinal axis C and is located upstream of the second angled portion 8 in the direction of travel of the oxidant. The second linear portion 10 of the peripheral shroud 5 faces the first linear portion 9 of the central shroud 4.
The annular space 6 thus comprises a linear premixing zone 11. The linear premixing zone 11 is delimited transversely, that is in a direction perpendicular to the central longitudinal axis C, by the first linear portion 9 on the one hand, and by the second linear portion 10 on the other hand.
The linear premixing zone 11 is defined by a linear length H measured along the central longitudinal axis C and by a spacing e measured between the first linear portion 9 and the second linear portion 10 in a transverse direction perpendicular to the central longitudinal axis C. The spacing e is therefore measured between the peripheral shroud 5 and the central shroud 4. In the linear premixing zone 11, the spacing e is constant along the linear length H.
The linear premixing zone 11 is thus delimited longitudinally, that is, along the central longitudinal axis C, by a proximal end 12 and by a distal end 13. The proximal end 12 is located on the side of the convergent zone 26, that is, the proximal end 12 is closest to the convergent zone 26. The distal end 13 is opposite the proximal end 12 and is therefore further away from the convergent zone 26.
The linear premixing zone 11 thus arranged, enables good quality premixing. Thus the production of nitrogen oxides is reduced.
Advantageously, the linear length H is defined so that it is at least equal to three times the spacing e. The applicant has thus determined that such a linear length H makes it possible to obtain a sufficiently homogeneous premix, thus reducing the production of nitrogen oxides by the burner 2.
Advantageously, the burner 2 comprises a fuel injection system 14. The fuel injection system 14 is positioned so as to inject fuel into the linear premixing zone 11. The fuel injection system 14 is located at a fuel injection distance V measured from the distal end 13 and along the central longitudinal axis. The distance V is at least equal to 0.5e.
By positioning the fuel injection system 14 at a distance from the distal end 13 in the linear premixing zone 11, the flow of oxidant between the distal end 13 and the fuel injection system 14 has time to stabilize, thereby improving the quality of the premix and reducing the production of nitrogen oxides.
Advantageously, the linear premixing zone 11 is fluidly connected to an oxidant supply sleeve 27. The annular space 6 is thus supplied with an oxidant, in this case air, which can be mixed with a fuel, in this case hydrocarbon gas.
Advantageously, the central shroud 4 comprises a first annular end portion. The first end portion 15 is arranged downstream of the first angled portion 7, in the direction of travel of the oxidant. The first end portion 15 defines a first end diameter D1.
The peripheral shroud 5 comprises a second annular end portion 16. The second end portion 16 is arranged downstream of the second angled portion 8, in the direction of travel of the oxidant. The second end portion 16 defines a second end diameter D2.
Note that the first end diameter D1 is measured from an outer face of the central shroud and the second end diameter D2 is measured from an inner face of the peripheral shroud.
The first end portion 15 and the second end portion 16 are substantially parallel to the central longitudinal axis. The first end portion 15 and the second end portion 16 together form an end duct 17. The end duct 17 thus ejects part of the fuel/oxidant mixture from the burner 2 in a direction substantially parallel to the central longitudinal axis C. This ensures a stable flame while reducing the production of nitrogen oxides.
The first end portion 15 has a first end length L1. The second end portion 16 has a second end length L2. The end lengths L1, L2 are measured along the central longitudinal axis C. The first end length L1 is less than or equal to the second end length L2. This provides a good compromise between flame stability and low nitrogen oxide production.
Advantageously, the central shroud 4 comprises fuel supply tubes 24 opening onto a central end 25 and capable of injecting fuel through said central end 25.
As previously mentioned, the installation 1 comprises a combustion chamber 3.
The combustion chamber 3 is delimited laterally by a wall 18. The wall 18 comprises an opening 19 through which the burner 2 can be inserted into the combustion chamber 3. A longitudinal end 20 of the peripheral shroud 5 is located in the combustion chamber 3. The longitudinal end 20 is arranged at a first insertion length K1 measured from the opening 19 and along the central longitudinal axis C.
Advantageously, the burner 2 comprises fuel injection devices 21. The fuel injection devices 21 are arranged in the peripheral shroud 5. The fuel injection devices 21 are capable of injecting fuel through an injection end 22.
The longitudinal end 20 and the injection end 22 are separated from one another by an offset length N between 0 and the first insertion length K1. The offset length N is measured along the central longitudinal axis C, and the injection end 22 is arranged upstream of the longitudinal end 20 in the direction of travel of the oxidant. This delays the ignition of the fuel, therefore allowing combustion fumes to recirculate, which reduces the production of nitrogen oxides.
The fuel injection devices 21 are arranged in an annular manner in the peripheral shroud 5. A distance U is defined which corresponds to the length separating two fuel injection devices 21 arranged in opposed position by a center G of the burner 2. The fuel injection devices 21 have an injection diameter D3. The distance U is between D2+D3 and an equivalent diameter Df of the wall 18 of the combustion chamber 3.
The equivalent diameter is a mathematical concept used to characterize any shape in the form of a circle, and therefore a diameter of the circle.
In this case, the combustion chamber 3 can take three different forms:
Said distance U makes it possible to obtain low nitrogen oxide production. In particular, when the distance U is close to the value of the equivalent diameter Df, nitrogen oxide emissions are particularly low.
Advantageously, the peripheral shroud 5 comprises an annular protuberance 23. The annular protuberance 23 comprises housings into which a fuel injection device 21 is inserted. In the zone wherein the protuberance 23 is located, the peripheral shroud 5 advantageously has an external diameter D4 greater than the diameter of said peripheral shroud 5 in the linear premixing zone 11. This allows the fuel injection devices 21 to be offset away from the central longitudinal axis C, thus enabling them to cool.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2114684 | Dec 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/087820 | 12/23/2022 | WO |
