Abstract:
A dirt separator may be retrofit into existing gas turbine engines since it is formed of circumferentially separate pieces which may be assembled together in the gas turbine engine.

Description:
The government may have certain rights to this invention pursuant to Contract No. F33657-99-D-2051 awarded by the United States Air Force. 
    
    
     BACKGROUND OF THE INVENTION 
     This application relates to a dirt separator for a gas turbine engine formed of separate pieces that can be assembled together in the gas turbine engine such that it can be retrofit into existing gas turbine engines. 
     Gas turbine engines are known, and typically include a fan section delivering air to a compressor section. The air is compressed and delivered downstream into a combustor section within which the air is mixed with fuel and then combusted to release energy. The products of this combustion process proceed downstream into the turbine and over a set of turbine airfoils, driving the turbine blades to rotate as they extract energy from the flow. 
     The turbine typically includes a plurality of rotating blades and static vanes. Since the products of combustion are hot, both the blades and the vanes are provided with a thermal protection mechanism involving cooling air. Typically, the cooling air is delivered as a redirected portion of the pre-combustion compressor air into the turbine airfoils. The cooling air structure within both the blades and vanes include relatively small holes in the exterior surface of the airfoils so as to bathe the airfoil in a protective layer of relatively cooler air than the mainstream flow coming from the combustor. 
     When there are impurities such as dirt or sand in the cooling air, some of these holes can become clogged. This is undesirable as it may prevent the cooling air from adequately protecting the surface of the airfoil. This problem has become particularly acute recently with the increased use of gas turbine engines on aircraft within a desert environment. 
     New engine designs are often now provided with a dirt separator to address this concern. However, existing gas turbine engines may have cooling air flow passages for that do not easily lend themselves to the installation of a standard dirt separator. Standard dirt separators are generally formed of a single cylindrical, or frusto-conical piece. These separators may be difficult to install into existing gas turbine engines. 
     SUMMARY OF THE INVENTION 
     In a disclosed embodiment of this invention, a dirt separator for use in a gas turbine engine is provided by at least a pair of circumferentially separate components which can be inserted separately into the gas turbine engine. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a gas turbine engine. 
         FIG. 2  shows a sectional portion of the  FIG. 1  gas turbine engine. 
         FIG. 3  shows one component of a dirt separator. 
         FIG. 4  shows another feature of the  FIG. 2  dirt separator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A gas turbine engine  10 , such as a turbofan gas turbine engine, circumferentially disposed about an engine centerline X, is shown in  FIG. 1 . The engine  10  includes a fan  14 , compressors  18  and  22 , a combustion section  26  and turbines  30  and  34 . As is well known in the art, air compressed in the compressors  18  and  22  is mixed with fuel and burned in the combustion section  26 , and expanded across turbines  30  and  34 . Turbine blades with turbines  30  and  34  rotate in response to the expansion, which in turn drive the compressors  18  and  22 , and fan  14 . Turbines  30  and  34  are comprised of alternating rows of rotating airfoils, commonly referred to as blades, which are axially spaced from static airfoils, commonly referred to as vanes. This structure is shown schematically in  FIG. 1 . While one example gas turbine engine is illustrated, it should be understood this invention extends to any other type gas turbine engine for any application. 
       FIG. 2  shows a dirt separator associated with a high pressure turbine, and having turbine blades  90 , and vanes  91  and  92 . A cooling air supply is utilized to cool the blade  90 , vanes  91  and  92 , and a blade outer air seal  111 . 
     A plurality of case clevis tabs  100  extend radially inwardly from a core engine case  99 . Flow passages are defined between the circumferentially spaced clevis tabs  100  such that air F can be delivered from an upstream location downstream as cooling air. A mount ring  102  has tabs  103  bolted at  105  to the clevis tabs  100 . The mount ring  102  supports a dirt separator inner liner  104  and outer liner  106 . As shown, outer liner  106  may be provided with a bend  108  to fit within the case  99 , while inner liner  104  may be provided with a flange  110  to be held between a blade outer air seal support  111 , and an inner surface of the case  99 . As shown, louvers  112  may be formed in the outer liner  106  to divert dirt or other impurities in the air F into a collection area  116 . An opening  114  may be formed in the inner liner  104  aligned with the louvers  112 . The inner and outer liners may be welded together. 
     As shown in  FIG. 3 , the tabs  103  are circumferentially spaced. The support ring  102  may thus be inserted into the engine to the location shown in  FIG. 2  by initially moving the tabs  103  between clevis tabs  100 , until the ring is inside of the clevis tabs  100 . The ring may then be turned such that the tabs  103  align with the clevis tabs  100 , and the bolts  105  may then be inserted. While only two clevis tabs are illustrated, it should be understood that there will be many more circumferentially spaced tabs. 
     As shown in  FIG. 4 , the liner portions  104  and  106  are formed of two or more separate parts having ends  120 ,  122 ,  124  and  126  which overlap. Each of these circumferentially separate parts may be inserted separately, and then mounted on the support ring  102 , and also supported by the circumferential overlap between the ends  120 ,  122 ,  124  and  126 . That is, the end  122  sits radially underneath the end  124 , and will serve to support the end  124 , and hence the entire part. While  FIG. 4  shows only two separate parts for the liners, there may be any number of separate parts. 
     With this invention, existing gas turbine engines can now be provided with a dirt separator, without any necessary modification to the engine casing. 
     While an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.