Abstract:
A diffuser particle separator may be integrated into a gas turbine engine to remove corrosive dust and salt particles from the engine&#39;s core air flow. The air flow may pass over a series of particle accumulator entrance orifices, trapping particles in a particle accumulator while allowing the air flow to continue unimpeded. Since dust deposits may become molten at high temperatures, removal of dust from the core and secondary airflow may be critical for long-life superalloy and ceramic components, particularly those with small diameter air-cooling holes and thermal barrier coatings.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to apparatus and methods for providing clean core air in an engine and, more specifically, to apparatus and methods for separating particles from diffuser air.  
         [0002]     Corrosive dust and salt particle deposits may be responsible for hot corrosion in the turbine and blockage of air-cooling passages (effusion cooling holes) in the combustion liner and internal cooling passages in turbine airfoils. Removal of dust from the core airflow is required to significantly improve turbine and combustor durability.  
         [0003]     For example, as turbine inlet temperatures continue to increase to improve the efficiency of modern gas turbine engines, a large number of small cooling holes are required along combustor liners and turbine airfoils to cool the components. These small cooling holes can plug with dust particles, reducing the effectiveness of the cooling and causing oxidation and thermal-mechanical fatigue. Distress may also be observed on high performance turbine stator and blade leading edges and airfoil pressure side surfaces due to glass deposits on the thermal barrier coating (TBC). The dust particles may melt and wick into the TBC, reducing the compliance of the TBC micro-structure. The result may be spallation of the TBC coating which may elevate the airfoil metal temperatures and cause oxidation and thermal-mechanical fatigue distress.  
         [0004]     U.S. Pat. No. 4,463,552, issued to Monhardt et al., discloses that a surge valve in the compressor may be used to remove dirt from the air flowpath. The surge valve is placed between the low and high pressure compressor, diverting dust into the bypass air. The &#39;552 patent, however, does not disclose apparatus or methods for removing particles from an air flow within the diffuser or at the exit of the diffuser.  
         [0005]     U.S. Pat. No. 3,338,049, issued to Fernberger, describes a particle separator in front of the inlet to the compressor. This separator has an inflatable inner wall to alter air flow and divert particles into a bypass duct. The &#39;049 patent, however, does not disclose apparatus or methods for removing particles from an air flow within or at the exit of the diffuser.  
         [0006]     As can be seen, there is a need for improved methods and apparatus to improve the air quality in the core of gas turbine engines for improved durability.  
       SUMMARY OF THE INVENTION  
       [0007]     In one aspect of the present invention, a diffuser particle separator, comprises a diffuser-deswirler for moving an air flow through an engine; at least one particle accumulator entrance orifice impinged by the air flow; a particle accumulator in communication with the particle accumulator entrance orifice for collecting and removing particles from the air flow; and a purge air duct for transporting accumulated particles out of an engine core.  
         [0008]     In another aspect of the present invention, a diffuser particle separator comprises a hollow toroidal-shaped particle accumulator located in a diffuser-deswirler air flow just downstream from the exit of a diffuser-deswirler; and a plurality of particle accumulator entrance orifices communicating an exterior of the particle accumulator with an interior portion thereof; and a purge air duct for transporting accumulated particles out of an engine core.  
         [0009]     In yet another aspect of the present invention, a diffuser particle separator comprises a set of particle accumulator entrance orifices formed through an inner wall of a diffuser-deswirler; and a particle accumulator in communication with the set of particle accumulator entrance orifices for collecting and removing particles from an air flow through the diffuser-deswirler; and a purge air duct for transporting accumulated particles out of an engine core.  
         [0010]     In a further aspect of the present invention, a gas turbine engine comprises a diffuser-deswirler for carrying core air flow to the exterior of a combustor liner; at least one particle accumulator entrance orifice within the air flow; and a particle accumulator in communication with the particle accumulator entrance orifice for collecting and removing particles from the air flow; and a purge air duct for transporting accumulated particles out of an engine core.  
         [0011]     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a cross-sectional view showing a diffuser particle separator according to one aspect of the present invention integrated into a turbine engine;  
         [0013]      FIG. 2  is a side view of the diffuser particle separator of  FIG. 1 ;  
         [0014]      FIG. 3  is a cross-sectional view showing a diffuser particle separator according to another aspect of the present invention integrated into a turbine engine;  
         [0015]      FIG. 4  is a cross-sectional view of a diffuser particle separator at a diffuser inner wall according to another aspect of the present invention; and  
         [0016]      FIG. 5  is a cross-sectional view of a diffuser particle separator at a diffuser inlet according to another aspect of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.  
         [0018]     Broadly, the present invention provides an inertial and/or electronic particle separator located in a diffuser or at the exit of a diffuser of a gas turbine engine. The diffuser particle separator may capture and remove salt and dust particles from the core airflow. This efficient means of dust collection may improve component environmental life while reducing thermal-mechanical fatigue distress on components such as the combustion liner and turbine airfoils. The apparatus of the present invention may be useful on any turbine engine, including those found in aircraft, ground vehicles, generators and other industrial gas turbine engines.  
         [0019]     Unlike conventional turbine engine particle removal systems which are located at various other locations of the engine, the diffuser particle separator according to the present invention may remove particles immediately prior to entry into the combustor plenum and secondary airflow cooling passages.  
         [0020]     Referring to  FIG. 1 , there is shown a cross-sectional view showing a diffuser particle separator  10 , according to one aspect of the present invention, integrated into a turbine engine  12 . Diffuser particle separator  10  may include at least one particle accumulator entrance orifice  14  and a particle accumulator  16  in communication with the particle accumulator entrance orifice  14 . Turbine engine  12  may include a combustor  25  having a combustor lining  26  upstream of a high pressure turbine rotor  28 . In one embodiment of the present invention, as shown in  FIG. 1 , the particle accumulator entrance orifices  14  may be cut into an outer wall  18  of a diffuser  20  near a diffuser-deswirler exit  22 . The diffuser particle separator  10  may be designed to enable particles in the airflow to impinge on the particle accumulator entrance orifices  14  and be captured for removal in the particle accumulator  16 . The particle accumulator  16  may be connected to a purge air duct  40  which may vent to a low pressure sink such as the fan duct or outside of the engine. The flow through the purge air duct  40  may be metered by use of a purge valve  45 .  
         [0021]     The particle accumulator entrance orifices  14  may be prepared from a screen (not shown) affixed over a hole in the diffuser  20 . Alternatively, particle accumulator entrance orifices  14  may be formed of holes or slots cut into a section of the diffuser outer wall  18 . For example, the particle accumulator entrance orifices  14  may be laser-machined or electrical discharged machined (EDMed) through the diffuser outer wall  18 . In either case, particle accumulator entrance orifices  14  may be formed to allow dust and other particles to impinge on the surface of the particle accumulator entrance orifices  14  and pass therethrough into the particle accumulator  16 . The particle accumulator entrance orifices  14  may have an average width of 0.005 to 0.05 inches.  
         [0022]     Referring now to  FIG. 2 , there is shown a side view of an isolated diffuser particle separator  10  of  FIG. 1 . Arrows  24  show the airflow through the diffuser  20 , over the particle accumulator entrance orifices  14  and out of the diffuser-deswirler exit  22 . Particle accumulator  16  may be used to accumulate particulate matter from the airflow through diffuser  20 .  
         [0023]     Referring to  FIG. 3 , there is shown a cross-sectional view showing a diffuser particle separator  30 , according to another aspect of the present invention, integrated into a turbine engine  12 . Diffuser particle separator  30  may include at least one particle accumulator entrance orifice  14  and a particle accumulator  16 ′ in communication with the particle accumulator entrance orifice(s)  14 . In this embodiment of the present invention, particle accumulator entrance orifices  14  may be located just beyond the diffuser-deswirler exit  22 . The particle accumulator  16 ′ may be a hollow toroidal-shaped accumulator with localized perforations (particle accumulator entrance orifices  14 ) communicating an exterior of the particle accumulator  16 ′ with an interior portion  32  thereof. Other hollow non-toroidal shapes may be configured for non-annular diffusers such as pipe diffusers.  
         [0024]     Interior portion  32  of particle accumulator  16 ′ may also include an electrically charged rod  34 . Since a significant amount of dust exiting the diffuser  20  may be electrically charged, the efficiency of the diffuser particle separator  10  may be enhanced by creating an electrical field, e.g., via electrically charged rod  34 , within the particle accumulator  16 ′. The shape of particle accumulator  16 ′ may have an aerodynamic contour to minimize any effect on engine performance. A purge air duct, not shown, transports accumulated particles out of the engine core.  
         [0025]      FIG. 4  shows a variation of the diffuser particle separator located in a diffuser inner wall  19 . The natural contour of the centrifugal impeller  29  may force particulates along an impeller inner wall  27 . The diffuser may be aerodynamically designed to force particulates along the diffuser inner wall  19  where particles may be collected in a diffuser particle separator accumulator  52 . The diffuser particle separator along the diffuser inner wall  19  may be used independently or in conjunction with a diffuser particle separator along an outer wall  18 . A purge air duct, not shown, transports accumulated particles out of the engine core.  
         [0026]      FIG. 5  shows another variation of a diffuser particle separator which is located at the diffuser inlet  21 . The natural contour of the centrifugal impeller  29  may force particulates along an impeller inner wall  27 . A diffuser particle separator accumulator  54  may be located at the diffuser inlet  21  just above and aft of the centrifugal impeller  29  to collect any particles that may be flowing in a secondary cooling flow that may proceed down the aft face of the impeller  29 . The diffuser particle separator located at the diffuser inlet  21  may be used independently or in conjunction with a diffuser particle separator along an outer wall  18  or in conjunction with a diffuser particle separator along an inner wall  19 , as previously described with reference to  FIG. 4 . A purge air duct, not shown, transports particles captured in accumulator  54  out of the engine core.  
         [0027]     The particle accumulators  16 , 16 ′,  52 , and  54  may be cleaned with a purge flow of air activated at engine idle. At other duty cycle power points of the engine  12 , utilization of purge flow may be optional. Purging of the accumulator utilizing various flow rates may be accomplished at high particulate ingestion operating conditions to improve particle separator efficiency. Purge flow rates may be metered at the desired level using the purge valve  45 . Purge air flow need not be utilized during performance critical operating conditions.  
         [0028]     By means of a non-limiting example, one may assume that the rate of deposition of corrosive salt and dust onto combustor and turbine airfoil surfaces may be dependent upon the amount of particulate contaminants in the core air flow. A 70% efficient inertial/electronic particle separator may approximately triple the lives of components that are currently life-limited by deposition of corrosive dust. Performance penalties may be avoided by using core airflow to purge the particle accumulator ( 16 ,  16 ′,  52 , and  54 ) when the engine is at idle or other non-performance-critical operating condition. In addition, the purge valve  45  may be closed to obtain optimal engine performance during take-off and at operating conditions that do not experience dust/salt environments, such as high altitude cruising.  
         [0029]     The diffuser particle separator  10  may be made of a titanium alloy or of an oxidation-resistant steel or a nickel-base or cobalt-base superalloy. A hard, oxidation resistant coating, such as (Ti, Al, Zr)N, may be used to increase the erosion life of diffuser particle separator  10 . The diffuser particle separator  10  may be made with ceramic or ceramic matrix composite materials.  
         [0030]     It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.