Local improvement of the mixture of air and fuel in burners comprising swirl generators having blade ends that are crossed in the outer region

Abstract

A burner having an air supply and a premix channel having an essentially annular cross-section, through which air and fuel flow during operation, and which is formed of an outer shell (5) and a hub (6). A plurality of swirl blades (7) arranged in the burner extend from the hub (6) to the outer shell (7) in a radial direction. Each blade's surface (11) is provided with a deflection in a radial outer region of the swirl blade (7), a downstream flow angle () to a main flow direction (13) increases at least once and decreases at least once in a radial direction at an outflow end (12) of the deflection surface (11).

Claims

1. A burner configured to inject fuel and air into a combustion chamber of a gas turbine, the burner comprising: a duct of substantially annular cross section formed by and between a radially outer annular shell and a radially inner annular hub, through which the air and the fuel flow and mix; multiple swirl blades arranged in the duct, each one of the multiple swirl blades including openings for supplying the fuel into the duct and extending a total radial length from the radially inner annular hub to the radially outer annular shell; each one of the multiple swirl blades having a deflection surface comprising an aft portion, the aft portion of each one of the multiple swirl blades having a first region having a first radial length extending from the radially inner annular hub to a radially inner boundary of a second region, the second region having a second radial length, and a third region having a third radial length extending from a radially outer boundary of the second region to the radially outer annular shell, wherein together the first radial length, the second radial length, and the third radial length extend the total radial length from the radially inner annular hub to the radially outer annular shell, each of the first region, the second region, and the third region having a respective flow-off angle along the first radial length, the second radial length and the third radial length, each respective flow-off angle being defined with respect to a main flow direction at a flow-off end of the aft portion of the deflection surface; wherein the respective flow-off angle of the first region along the first radial length is greater than the respective flow-off angle of the third region along the third radial length and less than the respective flow-off angle of the second region along the second radial length.

2. The burner as claimed in claim 1, wherein adjacent ones of the multiple swirl blades have different radial profiles with non-equal respective flow-off angles in at least one of: the first region, the second region, and the third region.

3. The burner as claimed claim 1, wherein each one of the multiple swirl blades are at least partially hollow.

4. The burner as claimed in claim 1, further comprising a central pilot burner system concentrically surrounded by the duct.

5. The burner as claimed in claim 3, wherein adjacent ones of the multiple swirl blades have different radial profiles with non-equal respective flow-off angles in at least one of: the first region, the second region, and the third region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a burner in a highly schematized basic diagram,

(2) FIG. 2 is a plan view of an unwound part of the main burner system,

(3) FIG. 3 is a plan view of a swirl blade and

(4) FIG. 4 shows sections through a swirl blade, showing their respective offsets in the radial direction from the hub to the outer shell.

(5) The burner 1 shown in FIG. 1, which may be used in connection with multiple similar burners for example in the combustion chamber of a gas turbine installation, comprises an inner pilot burner system 2 and a main burner system 3 which concentrically surrounds the pilot burner system 2. Both the pilot burner system 2 and the main burner system 3 can optionally be operated with gaseous and/or liquid fuels such as natural gas or heating oil.

(6) The main burner system 3 comprises a radially outer air supply and premix duct 4, also called an annular air duct, which is formed by an outer shell 5 and a hub 6 and through which there extend a plurality of swirl blades 7 of a swirl blading. These swirl blades 7 have outlet openings 8 for fuel, through which combustion gas can be injected into the air flowing in through the radial air supply and premix duct 4.

(7) FIG. 2 shows an unwound part of the main burner system 3 in plan view with a plurality of the swirl blades 7 and highlights the regions of good 9 and bad 10 admixing of the fuel in air. Radially inwards, that is to say in the vicinity of the hub 6, the blades 7 are comparatively close together, such that the fuel can be injected sufficiently far into the interspace between two blades 7 in order to achieve the best possible mixing. Radially outwards, in the vicinity of the outer shell 5, the blades 7 are accordingly further apart from each other, making it more difficult to inject the fuel sufficiently far into the air.

(8) FIG. 3 shows the view of the deflection surface 11 of a swirl blade 7 of a burner 1 according to the invention. The swirl blade 7 extends in the burner 1 from the radially inward hub 6 (to the right) to the radially outward outer shell 5 (to the left). Furthermore, in the exemplary embodiment of FIG. 3, the swirl blade 7 is embodied as a hollow blade with outlet openings 8 for fuel. For the purpose of improved understanding of the invention, three regions 101, 102 and 103 shown in respective radial direction lengths by the solid lines are labeled in the region of the flow-off end 12 of the deflection surface 11, wherein the regions 102 and 103 are to be attributed to the radially outer region of the blade 7.

(9) FIG. 4 shows the three sections, laid in the radial direction one after one the other, through the regions 101, 102 and 103 of the swirl blade 7 of FIG. 3, as seen from the hub 6 towards the outer shell 5. It can be seen that, at a radially inward flow-off end 12 of the deflection surface 11, i.e. in the section through the region 101, the flow-off angle .sub.1 with respect to a main flow direction 13 is between a flow-off angle .sub.3 of a radially outer flow-off end 12, i.e. in the section through the region 103, and a flow-off angle .sub.2 of a flow-off end therebetween, i.e. in the section through the region 102.

(10) Other embodiments of the swirl blade 7, in which in a radially outer region a flow-off angle with respect to a main flow direction 13 at a flow-off end 12 of the deflection surface 11 increases at least once and decreases at least once in the radial direction, are also possible as long as, in the outer region of the swirl blade 7, i.e. in the vicinity of the outer shell 5, a sort of crossover is achieved at the blade end, such that there, in the shear zone arising in operation, a mixing vortex is generated.