Fuel nozzles with water injection for gas turbine engines

A pressure atomizing fuel nozzle of the type that has a primary and secondary fuel system for a gas turbine engine and includes air swirl means and water injection is designed so that the water laden airstream is swirling in the same direction as both the fuels egressing from the primary fuel system and the secondary fuel system.

DESCRIPTION 
TECHNICAL FIELD 
This invention relates to fuel nozzles for gas turbine engines and 
particularly to fuel nozzles having a combined primary and secondary fuel 
injection system and adapted for water injection. 
BACKGROUND ART 
There has been a constant endeavor to increase the time between overhaul of 
jet engines that power aircraft and to reduce smoke and pollutants emitted 
into the atmosphere. This invention addresses itself to both of these 
problems. 
As is well known, thrust of the engine can be increased by adding water to 
the burner section. In fuel nozzles for certain engines both the primary 
and secondary fuels are injected into the burner in conically radiating 
spray patterns that are in coaxial relationship. Such nozzles are, for 
example, utilized on the JT-9D engine manufactured by Pratt & Whitney 
Aircraft Group of United Technologies Corporation, the assignee of this 
patent application and the details of which are incorporated herein by 
reference. In this configuration, water is admitted upstream of the fuel 
spray and passes through the fuel support heat shields prior to being 
injected into the burner section via the burner swirlers. The problem with 
this configuration is that a significant deterioration in burner 
performance was evidenced. Also, this type of water injection system 
manifested a high smoke density, produced excessive hot spots at the 
turbine inlet as well as excessive distortions of the turbine inlet 
temperature radial profile. 
It is also well known that fuel and air are injected into a burner with a 
tangential component so as to achieve a fast and complete mixing. Since 
water is admitted upstream of the juncture where it mixes with the fuel, 
it is carried in the airstream and assumes the same rotational direction. 
Hence, the fuel nozzle contains spin slots and vanes that are designed to 
impart a swirl to both the fuel and air. Further, the fuel nozzle is 
designed so that the fuel and air pattern in the burner combustion zone 
take the form of cones radiating from the apex as it leaves the fuel 
nozzle and flares into a cone as it propagates downstream in the burner. 
In heretofore nozzle configurations it has been conventional to impart the 
swirl of the fuel in a direction that is counter to the direction of the 
swirl of the air. 
We have found that we can obviate the problems noted above in the water 
injection mode by changing the relationship of the direction of the swirl 
so that the fuel and air/water mixture both swirl in the same direction. 
This inhibits the tendency of the outer cone (air/water mixture) to 
collapse the inner cone (fuel spray) as is the case in the counter 
rotation swirl patterns and improves the circumferential uniformity of 
burning and thus prevents localized hot spots that manifest into the 
turbine. The water in the airstream does not collapse the fuel pattern and 
does not tend to conglomerate in individualize streams. Actual tests have 
shown a remarkable reduction in smoke emission during wet performance as 
compared with wet performance of heretofore known water injection systems. 
DISCLOSURE OF INVENTION 
An object of this invention is to provide for a gas turbine engine an 
improved water injection fuel nozzle. 
A feature of this invention is to provide means in the fuel nozzle that 
produce swirling of the fuel, air, and air/water mixture so that the 
tangential component is in the same direction for each stream being 
injected into the burner. 
Other features and advantages will be apparent from the specification and 
claims and from the accompanying drawing which illustrates an embodiment 
of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION 
In its preferred embodiment this invention has particular utility for 
pressure atomized fuel nozzles that include both the primary and secondary 
fuel systems. For details of this type of nozzles reference should be made 
to the fuel nozzles utilized in the JT-8D and JT-9D engines manufactured 
by Pratt & Whitney Aircraft Group of United Technologies Corporation, the 
assignee of this patent application. Inasmuch as this invention only 
relates to the fuel nozzle the details of the engine and its combustor, 
fed by these nozzles, are eliminated herefrom for the sake of convenience 
and simplicity. Suffice it to say that the engines noted above utilize 
dual orifice fuel nozzles having pressure atomizing primary and pressure 
atomizing or air atomizing secondary nozzles where the primary nozzle is 
utilized for both low and high thrust engine operation and the secondary 
nozzle is operative only at the higher thrust regimes. 
As can be seen in the sole FIGURE, the nozzle generally illustrated by 
reference numeral 10 comprises a generally dome shaped body 12 including 
the cone body 14 defining the primary nozzle. Fuel issues from orifice 16 
in a swirling pattern imparted thereto by the swirl plug 18. As can be 
seen the swirling fuel flares into a conical pattern as it progresses into 
the combustion zone (not shown). 
Secondary fuel is introduced into the combustion zone through the annular 
orifice 20 which is fed thereto through this annular passageway 22 formed 
between the primary nozzle 14 and the nozzle structure 12. The swirl ring 
24 serves to inpart a vortex swirl pattern similar to the primary fuel 
pattern generated by swirl plug 18. This fuel likewise flares into a 
conical pattern as it progresses into the fuel zone. As is well known, the 
angle of the slots in the swirl ring 24 and swirl plug 18 serve to provide 
the direction of the swirl. The tangential velocity and the strength of 
the swirl will depend on the particular environment to which this nozzle 
is utilized. 
Air, likewise, is injected into the combustion zone in a swirling fashion. 
A portion of the air from the compressor (not shown) is admitted 
internally of nozzle nut 30, via swirl slots 32 and assumes the conical 
flow pattern as it progresses into the combustion zone. The remaining air 
is directed to the swirl vanes 34 in the swirl cup 36 where a portion 
thereof is split by splitter 38 and assumes the flow patterns as shown. As 
is well known, for water injection, water is admitted into the airstream 
at a given location upstream of the swirling means shown as inlet 40 and 
is carried in the airstream and swirled therewith through nozzle nut 30 
and cup 36. 
As can be seen by the sole FIGURE the direction of swirl for both the fuel 
and air/water mixture streams are in the same direction. This 
co-rotational aspect serves to prevent the water droplets from coalescing 
into a localized stream that would otherwise distort the temperature 
profile emanating from the combustor. From actual tests, it has been found 
that the co-rotational aspect has improved burner performance and reduced 
smoke emissions from the engine's exhaust during water injection modes. 
It should be understood that the invention is not limited to the particular 
embodiments shown and described herein, but that various changes and 
modifications may be made without departing from the spirit and scope of 
this novel concept as defined by the following claims.