Abstract:
A method of assembling an ejector is provided, wherein the method includes providing a motive nozzle tip having a centerline axis and including a nozzle tip edge having at least one protrusion extending through a plane substantially normal to the centerline axis. The method also includes coupling the motive nozzle tip to the ejector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/381,598 filed May 4, 2006 now U.S. Pat. No. 8,136,361, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to ejectors, and, more particularly, to an ejector motive nozzle that may be used in pumping, compression, or mixing applications. 
     At least some known ejectors mix two flow streams, a high-pressure (“motive”) stream and a low-pressure (“suction”) stream, so as to produce a discharge flow with pressure intermediate to or lower than the two input flows. The ejector motive nozzle facilitates this mixing process by accelerating the high-pressure motive flow, thereby creating a high speed jet that is channeled through a mixing tube or chamber to entrain the low pressure suction flow. The two mixed flows are then discharged, typically through a diffuser. 
     Some known ejectors use a motive nozzle that is surrounded by a casing and includes a nozzle tip having a round or rectangular cross-section oriented about an axis of the ejector. At least some known nozzles may create a motive jet that oscillates in a bending mode, producing coherent flow disturbances such as partial ring vortex structures at an edge of the jet. When these coherent flow disturbances strike a downstream wall of the casing, reflected acoustic waves may be produced and feedback towards the nozzle. The feedback waves may reinforce the jet bending oscillations and result in a fluid dynamic resonance that may produce damaging structural loads and/or high noise levels within the ejector. Over time, fluctuating loads produced by this fluid dynamic resonance may decrease the lifespan of the ejector or other hardware, add to maintenance costs, and/or create objectionable levels of environmental noise. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a method of assembling an ejector is provided, wherein the method includes providing a motive nozzle tip having a centerline axis and including a nozzle tip edge having at least one protrusion extending through a plane normal to the centerline axis. The method also includes coupling the motive nozzle tip to the ejector. 
     In another aspect, an ejector is provided, wherein the ejector includes a motive nozzle tip having a centerline axis and including a nozzle tip edge having at least one protrusion extending through a plane normal to the centerline axis. 
     In a further aspect, a gas turbine engine is provided, wherein the gas turbine engine includes a compressor and an ejector coupled in flow communication with and configured to receive air bled from the compressor. The ejector includes a motive nozzle tip having a centerline axis and including a nozzle tip edge having at least one protrusion extending through a plane normal to the centerline axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional schematic illustration of an exemplary gas turbine engine; 
         FIG. 2  is a schematic block diagram of the engine shown in  FIG. 1  and including a turbine cooling ejector; 
         FIG. 3  is an enlarged schematic illustration of the turbine cooling ejector shown in  FIG. 2 ; 
         FIG. 4  is a perspective view of an exemplary nozzle tip that may be used with the turbine cooling ejector shown in  FIG. 3 ; and 
         FIG. 5  is a perspective view of an exemplary cooling jet stream discharged from the nozzle tip shown in  FIG. 4 . 
         FIG. 6  is a perspective view of an alternative nozzle tip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic illustration of an exemplary gas turbine engine  100 . Engine  100  includes a compressor  102  and a combustor assembly  104 . Combustor assembly  104  includes a combustor assembly inner wall  105  that at least partially defines a combustion chamber  106 . Combustion chamber  106  has a centerline  107  that extends therethrough. In the exemplary embodiment, engine  100  includes a plurality of combustor assemblies  104 . Combustor assembly  104 , and, more specifically, combustion chamber  106  is coupled downstream from and in flow communication with compressor  102 . Engine  100  also includes a turbine  108  and a compressor/turbine shaft  110  (sometimes referred to as rotor  110 ). In the exemplary embodiment, combustion chamber  106  is substantially cylindrical and is coupled in flow communication with turbine  108 . Turbine  108  is rotatably coupled to, and drives, rotor  110 . Compressor  102  is also rotatably coupled to shaft  110 . The present invention is not limited to any one particular engine and may be implanted in connection with other engines or other devices which employ ejectors in any part of the processes by which they operate. For example, the present invention may be used with, but is not limited to use with oil refinery devices, chemical plant devices, and electric cars. 
     In operation, air flows through compressor  102  and a substantial amount of compressed air is supplied to combustor assembly  104 . Assembly  104  is also in flow communication with a fuel source (not shown in  FIG. 1 ) and channels fuel and air to combustion chamber  106 . In the exemplary embodiment, combustor assembly  104  ignites and combusts fuel, for example, synthetic gas (syngas) within combustion chamber  106  that generates a high temperature combustion gas stream (not shown in  FIG. 1 ). Alternatively, assembly  104  combusts fuels that include, but are not limited to natural gas and/or fuel oil. Combustor assembly  104  channels the combustion gas stream to turbine  108  wherein gas stream thermal energy is converted to mechanical rotational energy. 
       FIG. 2  is a schematic block diagram of engine  100  including a turbine cooling ejector  150  coupled in flow communication between compressor  102  and turbine  108 . Low-pressure air is extracted from compressor  102  from a plurality of outlets  152  and high-pressure air is extracted from a plurality of outlets  154 . In the exemplary embodiment, low-pressure air is extracted from the ninth stage of compressor  102  and high-pressure air is extracted from the thirteenth stage of compressor  102 . In alternative embodiments, low-pressure air may be extracted at any compressor low-pressure stage and high-pressure air may be extracted from any compressor high-pressure stage. 
     The high-pressure and low-pressure air is channeled to ejector  150 . Specifically, high-pressure air is channeled axially through a motive nozzle (not shown) within ejector  150 , and low-pressure air is channeled to a chamber (not shown) surrounding the motive nozzle. As high-pressure air is discharged from the motive nozzle, it entrains the low-pressure air, to facilitate mixing between the two air flows. The mixed air flow is discharged to turbine  108  wherein the air facilitates cooling turbine  108 . As such, ejector  150  facilitates cooling turbine  108  using low-pressure air, such that the efficiency of engine  100  is improved as compared to systems using high-pressure cooling air. 
       FIG. 3  is an enlarged schematic illustration of ejector  150 .  FIG. 4  is a perspective view of an exemplary motive nozzle tip  200  that may be used with ejector  150 .  FIG. 5  is a perspective view of an exemplary cooling jet  202  discharged from nozzle tip  200 . Ejector  150  includes a motive nozzle  204  and a casing  206  that extends radially outward from a downstream end  208  of motive nozzle  204 . Motive nozzle  204  includes a substantially annular body portion  210  and a tapered conical portion  212  extending from downstream end  208 . Nozzle tip  200  extends from downstream end  208  with a frusto-conical cross-sectional shape, such that motive nozzle body portion  210  has a larger radius R 1  than a radius R 2  of nozzle tip  200 . Body portion  210  also includes a high-pressure inlet  214 . 
     Casing  206  includes a substantially annular body portion  216  that is spaced radially outward from motive nozzle downstream end  208 , such that a low-pressure chamber  218  is defined therebetween. A frusto-conical portion  220  extends downstream from casing body portion  216 . Portion  220  is positioned such that low-pressure chamber  218  is coupled in flow communication with a chamber  222  defined by conical portion  220 . Furthermore, a substantially annular mixing channel  224  is coupled in flow communication with, and downstream from, conical portion  220 . Mixing channel  224  has a radius R 3  that is smaller than a radius R 4  of casing body portion  216 . An ejection end  226  of ejector  150  is defined at a downstream end  228  of casing  206 . Furthermore, casing body  216  includes a low-pressure inlet  230 . 
     The cross sectional area of nozzle tip  200  is convergent in the direction of flow and, in the exemplary embodiment, includes a plurality of protrusions  232  that extend substantially axially therefrom to define a nozzle lip  234 . In the exemplary embodiment, protrusions  232  are identical and each has a substantially triangular shape. Protrusions  232  extend circumferentially about nozzle tip  200 , such that a plurality of triangular recesses  236  are defined between each pair of circumferentially-adjacent protrusions  232 . Specifically, protrusions  232  define a chevron-shaped nozzle lip  234  at an end of nozzle tip  200 . In an alternative embodiment shown in  FIG. 6 , nozzle tip  200  is slotted and includes a plurality of protrusions extending from a nozzle lip defined at an edge of the slotted nozzle tip. Protrusions  232  may be rounded such that nozzle tip  200  includes a plurality of round-edged cutouts. Moreover, although only seven protrusions  232  are illustrated, it should be noted that nozzle tip  200  may include more or less protrusions  232 . In addition, the size, shape, number, and relative orientation of protrusions  232  is variably selected depending on the use of nozzle tip  200  to facilitate optimizing jet flow  238  discharged therefrom. More specifically, protrusions  232  and, more particularly, nozzle lip  234  facilitate creating a jet flow discharged therefrom with lobed-shaped vortices  240 , for example, a lobed-shaped jet  202 . 
     During operation, high-pressure air is channeled to ejector  150  and is discharged through inlet  214  into motive nozzle  204 . Air at relatively low pressure is discharged through low pressure inlet  230  into low pressure chamber  218 . The high-pressure air flows substantially axially through motive nozzle  204  and is accelerated to high speed prior to being discharged through nozzle tip  200 . The orientation of protrusions  232  facilitates discharged air from nozzle tip  200  creating lobed-shaped jet  202 . The shape, velocity, and pressure of lobed-shaped jet  202  facilitates jet  202  entraining the low-pressure air in low-pressure chamber  218  causing the high-pressure and low-pressure air to mix in mixing channel  224 . The mixed air is then discharged through ejector end  226 , such that the mixture of high-pressure and low-pressure air is utilized to facilitate cooling turbine  108 . In alternative embodiments, the mixed air may be used to cool other components of engine  100 . 
     The nozzle tip is configured to facilitate the formation of longitudinal flow structures (such as lobes or counter-rotating vortices) that stabilize the jet. Furthermore, the nozzle tip is configured to resist formation of other destabilizing flow structures (such as ring vortices) when the jet is perturbed by noise or other flow disturbances. Specifically, during engine operations, the lobed-shaped jet  202  created by protrusions  232  facilitates increasing the life-span of ejector  150 . Specifically, the protrusions  232  facilitate reducing the intensity and symmetry of flow disturbances produced by or associated with jet bending oscillations, such as coherent ring vortices. Typically, jet bending oscillations in an ejector cause acoustic waves to reflect off a casing wall and back towards the motive nozzle. The lobes created in jet  202  by protrusions  232  reduce the coherency of circumferential turbulent flow structure produced by jet bending, interfering with reinforcement of such flow structures by acoustic waves reflected from casing  206 . Furthermore, because the nozzle interior trailing edges produced by protrusions  232  lie outside of a plane normal to the nozzle, the ability of reflected acoustic waves to excite further jet bending oscillation is reduced. Specifically, protrusions  232  facilitate preventing a reflected wave from oscillating in phase with oscillations of jet  202 , such that the oscillations are disrupted and not enhanced. As such, protrusions  232  facilitate disrupting both the formation and excitation of jet bending oscillations, and thereby, facilitate reducing the effects that jet bending oscillations may have on ejector  150 . 
     As a result of protrusions  232 , less vibration is induced to ejector  150  by jet bending oscillations as flow is discharged from nozzle tip  200 . Furthermore, nozzle tip  200  and, more particularly, protrusions  232 , facilitate reducing the excitation of any resonance and vibrations induced to ejector  150 . Accordingly, ejector  150  generates substantially less noise, and experiences substantially reduced fluctuating structural loads than other known ejectors. As such, a useful life of ejector  150  and other connected devices is facilitated to be enhanced, and environmental noise produced by the ejector is reduced. 
     The above-described methods and apparatus facilitate increasing the life span of an ejector and reducing environmental noise produced by its operation. Specifically, the chevron-shaped nozzle tip produces a lobed-shape jet that facilitates reducing jet bending oscillations which may occur in an ejector motive nozzle. Furthermore, the lobed-shaped jet facilitates reducing the excitation of jet bending oscillations, such that vibrations induced to the ejector motive nozzle are reduced. Subsequently, less noise and fewer structural loads are generated within the ejector. Moreover, the chevron-shaped nozzle tip also increases entrainment of the low-pressure air, allowing the ejector to operate more efficiently. Ultimately, the above-described methods and apparatus facilitate providing a more efficient and more stable ejector, such that system engine efficiency may increase, costs associated with maintenance of the ejector and devices in flow communication with the ejector may decrease, and the life-span of the system may increase. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     Although the apparatus and methods described herein are described in the context of an ejector motive nozzle for a gas turbine engine, it is understood that the apparatus and methods are not limited to ejector motive nozzles or gas turbine engines. Likewise, the ejector motive nozzle components illustrated are not limited to the specific embodiments described herein, but rather, components of the ejector motive nozzle can be utilized independently and separately from other components described herein. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.