Burner for gas turbine engines with axially adjustable swirler

A burner for gas turbine engines is provided in which a ring-shaped swirling device is coaxially assigned to a fuel nozzle. The swirling device forms tangential ducts for an adjustable feeding of combustion air between profiles arranged along the circumference. In this case, the profiles are to be formed by corresponding sections of components which are arranged to be axially movable relative to one another. One respective section of a profile is to be a hollow body in which the corresponding other section engages in a movable manner. With the burner, a combustion is made possible that is low in pollutants while the swirling efficiency and the rotational swirl development are optimal.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to a burner and, more particularly, to a burner for 
gas turbine engines having a ring-shaped swirling device which is 
coaxially assigned to a fuel nozzle. The swirling device forms tangential 
ducts between profiled surfaces distributed along the circumference for an 
adjustable feeding of combustion air. 
In the case of modern burners and combustion chamber designs for gas 
turbine engines, a combustion that is low in pollutants is endeavored, 
particularly in the primary zone of the combustion chamber. It was found 
that a significant reduction of the emission of pollutants can be achieved 
in the case of a comparatively low combustion temperature of 
&lt;1,900.degree. K by means of a comparatively high proportion of air with 
respect to the fed fuel in the primary zone. 
In addition, relatively low pollutant emissions require, among other 
things, a uniform processing of the fuel-air mixture to be supplied to the 
primary zone as well as good combustion efficiency. This is particularly 
true in the case of burners known according to German Patent Document 
DE-PS 24 42 895 which operate with air support as "low-pressure systems" 
with a high fuel atomization efficiency and a partial wall-side and 
aerodynamic fuel evaporation. However, the known case does not provide 
swirling devices which can be adjusted with respect to the air flow rate 
in order to control different operating conditions with respect to 
correspondingly required variable fuel-air flow rates, in a manner that is 
as low in pollutants as possible. 
Furthermore, combustion chamber concepts which, in the interest of a 
combustion that is low in pollutants, provide a "variable chamber 
geometry" in order to supply combustion air and possibly mixed air by way 
of holes of the rows of holes are high in construction expenditures, 
technically complex, susceptible to disturbances and expensive. These 
devices can be controlled in their cross-sections by pipe sections of the 
flame tube jacket of the combustion chamber which can be displaced 
relative to one another in the axial or circumferential direction. 
From European Patent Document EP-PS 0251895, an annular combustion chamber 
for a gas turbine engine is known. In this case, for a combustion that is 
low in pollutants, an "external" swirling device is assigned to each 
burner which can be regulated with respect to the supply of a portion of 
the combustion air. 
In the known case, the regulating takes place via a screen which can be 
rotated on the outside on a central body in the circumferential direction 
and which has webs on openings distributed along the circumference. The 
webs, according to their length, project only partly into 
radial/tangential openings of the central body. The webs project in such a 
manner that, in intermediate positions of the screen, they each have an 
angular position which deviates from the openings. In the intermediate 
positions which are decisive for the regulating, a guiding of the duct is 
obtained which throttles the air flow at the inlet, is divergent in the 
direction of the flow and expands abruptly downstream of the trailing edge 
of the web in the direction of a large-surface duct outlet. In the 
process, the respective circumferential component of the flow at the 
respective outlet of an opening is clearly weakened in the, manner of a 
separating diffuser flow, whereby the required generating of the swirl is 
impaired considerably. This is a significant disadvantage with respect to 
obtaining a uniform development of turbulence which is required during the 
whole, operating condition and a resulting uniform and stable combustion 
that is low in pollutants. 
There is therefore needed a burner of the initially mentioned type wherein 
in a relatively simple manner, at least one swirling device permits over a 
large control range the air flow rate operationally required for a 
combustion which is uniform and low in pollutants while a uniformly 
pronounced rotational swirl is maintained. 
According to the present invention, these needs are met by a burner for gas 
turbine engines having a ring-shaped swirling device which is coaxially 
assigned to a fuel nozzle. The swirling device forms tangential ducts 
between profiled surfaces distributed along the circumference for an 
adjustable feeding of combustion air. The profiled surfaces are formed by 
corresponding sections of components which are arranged to be axially 
movable relative to one another. One respective section of a profiled 
surface is a hollow body in which the corresponding other section engages 
in a movable manner. 
According to the present invention, the sections which form the profiles or 
profiled surfaces are arranged in an axially projecting manner on mutually 
opposite faces of two, possibly ring-shaped, or annual-disk-shaped 
components. Preferably, the profile sections constructed as hollow bodies 
may be designed to be relatively thin-walled and to be precisely 
coordinated with the outer profile geometry of the profile sections of the 
respective other components which can be axially moved into it. 
In the case of the present invention, an axial profile lengthening or 
shortening is virtually obtained during the relative adjustment with the 
significant advantage that the recesses which are in each case mutually 
opposite between the profile sections, develop axially enlargeable or 
reducible cross-sections of the swirling ducts. This occurs in suck a 
manner that in all positions, along the whole duct length, flow 
cross-sections exist which are always maintained to be constant. The front 
wail course of the hollow-body-type, section which projects slightly in 
intermediate positions or in the maximally opened end position presents no 
significant aerodynamic "obstacle". In the case of the present invention, 
swirling ducts are constructed with respectively continuous square or 
rectangular cross-sections. The possibility exists to construct the 
profile sections and thus the profiles and swirling ducts to be 
radially/tangentially curved in the circumferential direction. 
The aerodynamic impairments or disadvantages which were mentioned with 
respect to the known prior art do not occur either on the inflow or on the 
outflow side. Despite the adjustment in the sense of a change of the air 
flow rate, a speed profile exists which, on the outlet side, is uniform 
along the circumference. 
Therefore, because of the indicated characteristics, the swirling flow and 
thus the desired rotational swirl geometry, which is also responsible for 
an optimal processing of the fuel/air mixture, will not be impaired in the 
different intermediate positions. 
Using the adjustable swirling device, the whole or a significant portion of 
the primary air which is required for a combustion that is low in 
pollutants can be supplied. The swirling device can be adjusted for the 
flow rate of relatively small and relatively large amounts of air. 
In an advantageous further development, the present invention permits the 
combination of at least one controllable or adjustable swirling device 
with a stationary swirling device which makes available a constant air 
supply during the whole operating condition. The fuel supply is varied 
depending on the load condition, in which case an air supply is 
"superimposed" on the variable operating conditions which, while being 
adapted to the respective operating conditions, meets the air requirement 
with respect to a combustion that is low in pollutants. The latter air 
requirement may be regulated, for example, as a function of an 
operationally increasing combustion temperature and/or, pressure in the 
combustion chamber. 
The present invention includes the possibility of burning, for example, 
stoichiometrically, in certain engine conditions, as well as dependent on 
the design and use spectrum of the engine, i.e. during the igniting and 
the start of the operation as well as, possibly, during an extreme full 
load. The invention also provides burning, predominantly in the cruising 
operation, with a large amount of air and therefore in a manner that is 
low in pollutants. 
The concerned swirling devices may generate in approximately the same 
direction or in mutually opposite directions rotational or mixed air 
swirls which rotate with respect to the burner axis or nozzle axis. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
According to FIG. 1, a ring-shaped swirling device 2 is coaxially assigned 
to a fuel nozzle 1 in the case of a burner of a gas turbine engine. It 
will be understood that all directions used herein are in reference to an 
axis extending axially through the fuel nozzle 1 unless otherwise 
indicated. In this case, a portion of the air removed at the compressor 
end flows according to arrow D as primary air first in the axial direction 
of the engine into an upstream annulus 3 constructed at the head end of 
the combustion chamber. By way of the annulus 3, the fed primary air D is 
fed from above and from the outside in the radial direction of the engine 
over the component 10 of the swirling device 2 after being locally 
deflected according to the direction of the arrow D'. The component 10 is 
frontally closed in itself. The annulus 3 is formed between a closing hood 
4 as well as, viewed from the left to the right, a section of the fuel 
nozzle 1, the swirling device 2 and the rear, wall 5 of the flame tube 6 
of the combustion chamber. 
As illustrated particularly by the completely opened end position according 
to FIG. 4, the profiles 7 of the swirling device 2 which are arranged to 
be distributed uniformly along the circumference are formed by 
corresponding sections 8, 9 which each project axially with respect to the 
engine from mutually opposite faces of two annular-disk-shaped components 
10, 11. 
In this case, one section 9 of a profile 7 is constructed as a hollow body 
20 (see also FIG. 5) into which the respective other section 8 can be 
moved axially more or less far in the axial direction of the engine. Thus, 
sections 8 engage in an axially movable manner in the other sections 9. In 
the case of an axial adjustment of at least one component 10, variable 
radial/tangential swirling ducts K (FIG. 3) and K' (FIG. 4), respectively, 
which have flow cross-sections which remain constant along their whole 
length and are rectangular in this case can be adjusted between the 
profiles 7. In the end position according to FIG. 3, sections 8, 9 of the 
profiles 7 are axially moved completely into one another so that the 
respective swirling ducts K form the smallest possible overall flow 
cross-section of the swirling device. This contrasts with the end position 
according to FIG. 4 in which the swirling ducts K' make available the 
largest possible overall flow cross-section. 
Particularly in contrast to the embodiment according to FIGS. 3 and 4, 
within the scope of the invention, an arrangement would be possible in the 
case of which hollow bodies and full profiles follow one another in 
sections continuously in the circumferential direction on each face of a 
component 10 and 11. 
According to FIGS. 1 and 2, it is also assumed that one component 11 is 
fixedly connected with the combustion chamber, in this case, therefore, 
with the rear wall 5 of the flame tube 6. Component 11 is centered on the 
rear wall 5 and firmly anchored via a recess 13 ending in a radially 
interior nose edge 12. The nose edge 12 forms a guide for the duct which 
is convergent/divergent in the direction of the flow. 
As also illustrated in FIGS. 1 and 2, the other component 10 is radially 
arranged, by way of a sleeve-shaped section, on the inside slidable or 
adjustable in the axial direction on the fuel nozzle. The other component 
10 may also be axially adjustable on a cylindrical nozzle carrier or 
nozzle assembly. 
According to another further development, the fuel nozzle 1 or its housing 
jacket is axially adjustable in the axial direction (arrows F, F') in 
order to achieve along the whole adjusting range of the swirling device 2, 
a positioning of the fuel spray cone Kg which is optimally coordinated 
with the respective flow-off direction of the swirled primary air D'' 
(FIG. 2). This allows a rotational swirl W (FIG. 1) to be generated in the 
primary zone which is optimally enriched with fuel and is uniform along 
the circumference of the swirl in the extremely different end positions of 
the swirling device 2 according to FIGS. 3 or 4. 
FIG. 5 clearly illustrates the construction and arrangement of the 
essentially triangular profile sections 8 as thin-walled hollow bodies 
inside the geometrically correspondingly adapted profile sections 9. The 
profile sections 8, 9 have cross-sections which taper in a wedge shape in 
the direction from the outside to the inside diameter (outlet side) of the 
swirling device, while enclosing the swirling ducts K and K' which are 
uniformly and evenly distributed along the circumference, in this case, in 
a straight tangential construction. 
However, within the scope of the present invention, the swirl ducts and/or 
the profile sections may also be constructed to be curved or may be 
constructed in the manner of blade ducts and/or in a blade shape. 
FIG. 6 illustrates another embodiment of the invention with a burner 
constructed on the head end of the combustion chamber in combination with 
a swirling device 2. The, swirling device 2 can be adjusted in the sense 
of FIGS. 1 to 5. A stationary swirling device 14 is arranged behind the 
swirling device 2. A radial inflow (arrow D''') is supplied from the 
primary air D flowing-in in the axial direction. 
In contours illustrated by the solid lines, the adjustable swirling device 
2 represents the end position with the respective smallest overall flow 
cross-section according to ducts K, in the sense of FIGS. 1 and 3. This is 
in contrast to the largest overall flow cross-section shown by an 
interrupted line and with the ducts K' which in this case are maximally 
opened in the sense of FIGS. 2 and 4. 
According to FIG. 6, the adjustable swirling device 2 has the 
annular-disk-type component 10 arranged to be axially displaceable or 
adjustable on the fuel nozzle 1 and has the sleeve-shaped inner shaft and 
the sections 8 (FIG. 2 and 4) that can be moved axially into the sections 
9 (FIG. 4, 5) of the other component 11 which are constructed as hollow 
bodies. The other or stationary component 11 forms a shielding wall in 
FIG. 6 which separates the swirling ducts K, K'' from one another and 
which extends downstream radially/axially in the shape of a sleeve (H) as 
well as coaxially to the nozzle axis or burner axis A. By way of 
respective fixed profiles, which form the swirling ducts K'' of the 
stationary swirling device 14, the fixed component 11 of the adjustable 
swirling device 2 is held centrally and firmly by way of a deflecting 
piece 15 on the flame tube rear wall 5 or on the combustion chamber 
housing. The deflecting piece 15'' has a convergent/divergent radially 
interior wall contour which is also rotationally symmetrical to the nozzle 
axis or burner axis A. Radially on the outside, the deflecting piece 15 is 
continued as the shielding wall 16 at a distance axially with respect to 
the rear wall 5. 
By way of the two swirling devices 2, 14 (FIG. 6), rotational swirls W1, W2 
may be generated in the primary zone which are rotated in the same 
rotational direction or in opposite directions to one another and which 
are enriched with fuel B from nozzle 1 or mixed intimately. 
In the end position of the swirling device 2 which is illustrated fully 
open by an interrupted line, in combination with the stationary swirling 
device 14, a combustion in the primary zone can be achieved which is 
extremely rich in air or "cold" and low in pollutants. 
The axial adjustment of one of the two components, for example component 
10, of the adjustable swirling device 2 may take place by hydraulically, 
pneumatically or electrically actuated adjusting devices. 
Particularly in the case of an annular combustion chamber with burners 
which are arranged at the head end to be distributed uniformly along the 
circumference, there is the possibility for such an operation that a 
rotatory adjusting movement of a common ring by way of levers as well as 
oblong-hole slot guides, the latter in each case arranged obliquely to the 
burner axis, is in each case converted into an axial adjusting movement. 
In the case of a corresponding axial adjustment of the at least one 
component, such as 10, the corresponding swirling device 2 can adjust or 
control the air flow rate as a function of the engine load condition from 
individual engine parameters or variables or as a function of locally 
measured pressure and temperature courses in the combustion chamber. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.