Coanda effect turbine nozzle vane cooling

Turbine nozzle vane cooling difficulties may be avoided in a gas turbine including a rotary compressor (10), (14) having a turbine wheel (10), (16) connected to the same; a nozzle (34) having a plurality of vanes (36) surrounding the turbine wheel (10), (16) for directing products of combustion thereat; and a combustor (28) for burning fuel and providing the products of combustion to the nozzle (34). The vanes (36) have elongated openings (54) in the leading edges (42) thereof, the openings terminating in generally parallel, curved surfaces (62), (64) that merge with the leading edges (42). The openings (54) are in fluid communication with the compressor (10), (14) and, as a consequence, compressed air flowing out of the openings (54) attaches itself to the surfaces (66), (68) of the leading edge (42) of the vanes (36) to provide exit cooling.

FIELD OF THE INVENTION 
This invention relates to the cooling of the vanes used in turbine engine 
nozzles and, more particularly, to the use of the Coanda effect to achieve 
enhanced cooling. 
BACKGROUND OF THE INVENTION 
As is well known, one significant factor in determining the life of a gas 
turbine engine revolves about the ability of the turbine nozzle to stand 
up to the temperatures of the hot gases of combustion that the nozzle 
receives from the engine combustor and directs against the turbine wheel. 
Too high temperatures will result in metal fatigue, while non-uniform 
temperatures will result in thermally generated stresses which will, over 
a period of time, literally pull the nozzle apart. 
While there are many ways of attacking these problems, one approach focuses 
itself on the cooling of the vanes that make up a typical nozzle. Cooling 
the vanes typically involves locating one or more passages within each 
vane that pass a cooling fluid through such a passage. Quite frequently, a 
variety of apertures extend from the coolant passages within the vanes to 
the surfaces of the vanes so that a coolant, typically compressed air from 
the compressor section of the engine, is discharged into the stream of 
gases flowing to the turbine wheel. Many of these proposals are extremely 
complicated and expensive to implement due to the need for specialized 
conduits, the forming of a multiplicity of apertures and the like. 
In the previously identified co-pending application, the details of which 
are herein incorporated by reference, there is disclosed a simplified 
means of cooling the vanes in a turbine nozzle. In particular, according 
to one embodiment disclosed therein, each vane, near its leading edge, 
includes a single internal passage that is connected to the discharge side 
of the turbine engine compressor to receive compressed air therefrom. An 
opening extends from the passage to the leading edge and opens thereat so 
that coolant first flows through each vane to cool the same by conduction 
and then is discharged at the leading edge to flow past the sides of the 
vanes to provide a further cooling effect. 
The present invention is intended to be an improvement on the invention 
disclosed in the previously identified, prior application. 
SUMMARY OF THE INVENTION 
It is the principal object of the invention to provide a new and improved, 
but simple means of cooling the vanes in a turbine nozzle. 
An exemplary embodiment of the invention achieves the foregoing object in a 
gas turbine including a rotary compressor, a turbine wheel connected to 
the compressor to drive the same, a nozzle having a plurality of vanes 
surrounding the turbine wheel for directing products of combustion thereat 
and a combustor for burning fuel to provide the products of combustion. 
The combustor has an outlet connected to the nozzle. 
An elongated opening is disposed in the leading edge of each of the vanes 
and each said opening terminates in generally parallel, curved surfaces 
that smoothly merge into the leading edge. Means are provided to establish 
fluid communication between the openings and the compressor. 
As a consequence of the foregoing structure, gas from the compressor 
exiting the openings will, as a result of the Coanda effect, attach itself 
to the curved surfaces and flow along the leading edge to assure good heat 
exchange contact and adequate cooling of the vanes. 
In a preferred embodiment, a divider is located within each such opening 
for dividing the flow of gas therethrough into two streams, one for each 
side of each vane. 
In a highly preferred embodiment, the divider is wedge-shaped with a 
pointed section extending into a corresponding one of the openings. 
Preferably, the wedge-shaped dividers have side surfaces merging at the 
pointed section and the side surfaces are curved and generally parallel 
the adjacent one of the curved surfaces. 
Other objects and advantages will become apparent from the following 
specification taken in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A typical turbine engine with which the engine may be employed is 
illustrated in FIG. 1 and with reference thereto is seen to include a 
rotor, generally designated 10, having a hub 12. On one side of the hub 12 
are a plurality of compressor blades 14 to define a radial compressor. On 
the opposite side of the hub 12 are a plurality of turbine vanes 16 which 
define a turbine wheel. Because the two sets of blades 14 and 16 are on a 
single hub 12, it will be appreciated that the turbine wheel thus defined 
is connected to the compressor to drive the same. At the same time, it 
should be understood that while the construction illustrated and just 
described is what might be termed a "monorotor," the invention is not 
limited to such but will find utility in other arrangements where, for 
example, the compressor and the turbine wheel are completely separate, and 
even on separate axes. 
A shaft 18 is connected to the rotor hub 12 and may be utilized to transmit 
power generated by operation of the engine to a point of use (not shown), 
as well as to journal the rotor 12 for rotation about an axis 20. 
Radially outward of the tips 22 of the compressor blades 14 is a 
conventional diffuser 24 and the same discharges compressed air into a 
plenum 26 in which is disposed a conventional, annular combustor 28. By 
means known in the art, air from the compressor is utilized to cool the 
combustor 28, as well as to provide an oxidant for fuel injected into the 
combustor 28 by any one of a series of fuel injectors 30 (only one of 
which is shown). 
The combustor 28 has an outlet area 32 through which hot gases of 
combustion pass to a turbine nozzle, generally designated 34 which directs 
such gases radially inward against the blades 16 to power the engine. The 
nozzle 34 is typically made up of a series of vanes 36 which extend 
between the front turbine shroud 38 and the rear turbine shroud 40 as is 
well known. 
As seen in FIG. 2, each vane 36 has a leading edge 42 and a trailing edge 
44. The leading edge 42 will, of course, be right at the combustor outlet 
32, while the trailing edge 44 will be adjacent radially outer tips 46 
(FIG. 1) of the turbine blades 16. 
With reference to FIGS. 2 and 3, at the location at each of the vanes 36, 
the front shroud 38 is provided with a bore 48 which aligns with a bore 50 
closely adjacent the leading edge 42 and located within the vane 36. The 
bore 50 is parallel to the leading edge 42 and extends more than a 
majority of the way across the vane 36. Near the center of the vane, the 
leading edge 42 is provided with an elongated opening 54 that is in fluid 
communication with the passage and thus the bore 48. 
The bore 48, in turn, is in fluid communication with the discharge side of 
the compressor as, for example, by means of a conduit shown somewhat 
schematically in FIG. 1 at 60. Preferably, however, the connection will be 
downstream of the diffuser 24 and may be as disclosed in the previously 
identified co-pending application. In any event, compressed air from the 
compressor can be flowed through the passage 50 to cool each of the vanes 
36 and then discharged from the openings 54 in the vanes to flow along the 
sides of the vanes to cool the same. 
To enhance this cooling effect, the opening 54 is elongated along the 
leading edge 42. Furthermore, the elongated sides of the opening 54 are 
curved as illustrated at 62 and 64 in FIG. 3 so as to smoothly merge into 
the leading edge 42. That is to say, the openings 54 are not ordinary 
bores or machined slots but, rather, smoothly curved so that the gas 
exiting the passage 50 through the opening 54 will not encounter a sharp 
edge. As a consequence of this construction, the Coanda effect is 
operative to cause the emanating streams to attach themselves to the 
adjacent exterior surfaces 66 and 68 on either side of the mid-point of 
the leading edge 42, notwithstanding the fact that hot gas from the 
combustor 28 will be flowing in the opposite direction as the gas from the 
compressor emerges from the openings 54. This attachment of the emanating 
air streams not only assures that the air streams will be in contact with 
the vanes 36 to cool the same, it also provides buffering streams to 
isolate the vanes 36 from direct contact with the hot gases of combustion 
thereby allowing the vanes 36 to operate more coolly. 
FIG. 4 shows a further embodiment of the invention and one that is 
preferred over FIG. 3. In the embodiment of FIG. 4, a thin baffle or 
divider 70 approximately parallels the sides of the opening 54 and is 
located midway between the two. As a result, it provides positive 
assurance that the air exiting the openings 54 will be divided into two 
discrete streams, one for each of the sides 66 and 68. FIG. 6 illustrates 
the disposition of the flow divider 70 in the opening 54, the same being 
anchored at its respective ends 72 and 74 within the vanes 36. 
Still another embodiment and a highly preferred embodiment is illustrated 
in FIG. 5. In this embodiment, a flow divider 80 much like the flow 
divider 70 is utilized, except that the flow divider 80 is wedge-shaped as 
illustrated. That is to say, the flow divider 80 has a pointed section 82 
which extends into the opening 54 towards the passage 50. Adjacent side 
surfaces 84 and 86 merge at the pointed section. The side surfaces 84 and 
86 of the wedge-shaped flow divider are curved and are somewhat concave as 
illustrated in FIG. 5. It will be appreciated from FIG. 5 that the same 
generally parallel, that is, are generally concentric width, the curved 
surfaces 62 and 64 forming the sides of the openings 54. Thus, the flow 
divider 80 not only serves to divide the flow into two discrete streams, 
but further serves to direct the flow at the curved surfaces 62 and 64 to 
minimize any possibility of separation. 
From the foregoing, it will be readily appreciated that the invention 
advantageously makes use of the Coanda effect to achieve enhanced cooling 
of the vanes employed in a turbine nozzle. Consequently, the invention 
will provide for longer life turbines.