Abstract:
An acoustic-structural LPC splitter assembly which comprises a structural acoustic splitter through which are arranged a plurality of bleed exhaust ports, the acoustic splitter having a first and second end, an inner and outer surface, a front joint for securing the first end, and a slip joint formed at an FEGV interface for securing the second end, wherein the structural acoustic splitter provides support sufficient to maintain concentricity of an LPC inner case.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an acoustic-structural low-pressure compressor (LPC) splitter assembly constructed so as to reduce weight and increase structural support. More specifically, this invention relates to an acoustic-structural LPC splitter assembly providing integral support for a plurality of low-compressor bleed exhaust ports. 
     (2) Description of the Prior Art 
     A gas turbine splitter is located axially downstream of the engine&#39;s fan stage. The fan exit stream air is “split” by the splitter assembly into two flow streams: core flow and bypass flow. 
     A standard gas turbine splitter assembly consists of: the splitter nose, acoustic panel cowling, low-compressor bleed exit duct, and low-pressure compressor (LPC) stator case support structure. This configuration consists of a large quantity of parts and is heavy, especially on large thrust engines. The low-compressor bleed is used during engine starting and surge conditions. 
     What is needed is a gas turbine splitter assembly that is strong enough to withstand the gas loading of fan exit streams and maneuver loading, covered with acoustic material to attenuate fan noise, and is lightweight. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an acoustic-structural LPC splitter assembly providing integral support for a plurality of low-compressor bleed exhaust ports. 
     In accordance with the present invention, an acoustic-structural splitter assembly for use in an engine which comprises a structural acoustic splitter through which are arranged a plurality of bleed exhaust ports, the acoustic splitter having a first and second end, an inner and outer surface, a front joint for securing the first end, and a slip joint formed at an FEGV interface for securing the second end, wherein the structural acoustic splitter provides support sufficient to maintain concentricity of an LPC inner case. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 A cross-section illustration of an LPC splitter known in the art. 
     FIG. 2 A cross-section illustration of the acoustic-structural LPC splitter of the present invention. 
     FIG. 3 A diagram of the aft slip joint of the present invention. 
     FIG. 4 A diagram of an alternative embodiment of the acoustic-structural LPC splitter of the present invention. 
     FIG. 5 A cross-section illustration of the acoustic structural splitter of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention integrates several low-pressure compressor (LPC) static structure part functions into a single part while simultaneously reducing weight and cost and increasing acoustic treatment. The present invention combines the load bearing and hoop stiffness of the LPC bleed cavity structure with the acoustic treatment of the flowpath fairing. The resulting design is a sandwich construction of structural and acoustic materials providing the hoop and flexural stiffness and acoustic treatment needed in LPC fairings. 
     With reference to FIG. 1, there is illustrated in cross section a conventional commercial LPC known to the art. The following described elements comprising the LPC are formed from rotating the cross section about a center axis 19 through 360 degrees. The flowpath fairing  1  with attached acoustic treatment bridges the expanse formed between the fairing front bolted joint  6  oriented towards the front of the engine and the fairing slip joint  5  located further aft of the fairing front bolted joint  6 . Fairing slip joint  5  is supported in part by flowpath fairing support and stator case stiffener  3  which extends from the LPC inner case  17  to the fairing slip joint  5 . Between the fairing bolted joint  4  and the fairing slip joint  5 , there may be inserted one or more low compressor bleed exhaust ports  2 . 
     With reference to FIG. 2, there is illustrated the acoustic-structural LPC splitter of the present invention. The flowpath fairing, is extended from splitter  22  to the fan exit guide vane (FEGV) interface  9 , whereby there is formed fairing slip joint  21 . By extending the flowpath fairing  1  to the FEGV interface  9  and using structural materials, flowpath fairing  1  becomes structural acoustic splitter  11 . Structural acoustic splitter  11  is a load carrying member of full hoop construction. Structural acoustic splitter  11  is self supporting with regards to any attached acoustic treatment and provides support to the LPC inner case  17 . 
     In a preferred embodiment, the acoustic treatment is integral to structural acoustic splitter  11 . As illustrated in FIG. 5, structural acoustic splitter  11  may be formed of an acoustic material  53  with composite backing skin  51  bonded to one or both sides. The acoustic material  53  may be comprised of metallic or composite material. In an alternative embodiment, the acoustic material  53  may be omitted entirely or sprayed or otherwise attached to an existing structural acoustic splitter  11 . 
     As a result of these structural alterations, there is eliminated the need for the flowpath fairing support and stator case stiffener  3 . Being of full hoop construction, the structural acoustic splitter  11  improves LPC case concentricity, resulting in longer performance retention. Extending the flowpath fairing  1  to form structural acoustic splitter  11  also improves noise attenuation via an increase in acoustically treated surface area. In a preferred embodiment, low-compressor bleed exhaust ports  2  are periodically cut through the structural acoustic splitter  11 . By doing so, the metallic structure and bolts supporting these ports are eliminated. Low compressor bleed exhaust ports  2  may be glued in from the inner or outer diameter, bolted in, or otherwise fastened to structural acoustic splitter  11 . 
     The structural acoustic splitter  11  can still accommodate thermal growth along the engine axis by including an aft slip joint  21  at the FEGV interface  9 . Positive circumferential, radial and axial restraint is still maintained by the conventional bolted joint  10 . 
     With reference to FIG. 3, there is illustrated in detail an aft slip joint  21  in accordance with the present invention. Aft slip joint  21  is formed from full hoop slot  31  into which is inserted an end of structural acoustic splitter  11 . Surrounding the end of structural acoustic splitter  11  and in contact with an inner surface  37  of full hoop slot  31  there is dispersed a sacrificial wear material  33 . As structural acoustic splitter  11  undergoes thermal expansion and contraction, it slides forwards and backwards inside of full hoop slot  31 . Sacrificial wear material  33  serves to prevent wear on structural acoustic splitter  11  and can be replaced when a quantity has been compromised sufficient to impede the performance of structural acoustic splitter  11 . In addition, a lap seal  35  may be attached to structural acoustic splitter  11  and extend rearward to cover the interface between structural acoustic splitter  11  and full hoop slot  31 . 
     With reference to FIG. 4 there is illustrated an alternative embodiment of the present invention. A radial stiffener  41  is attached between the LPC inner case  17  and structural acoustic splitter  11 . Radial stiffener  41  attaches to an underside of structural acoustic splitter  11  between aft slip joint  21  and bolted joint  10 . 
     The structural acoustic splitter  11  of the present invention weighs less than a standard splitter assembly due to reduced part count and a reduction in size of the LPC stator case support structure. The structural acoustic splitter  11  of the present invention is axially longer than a typical flowpath fairing  1  and provides a greater surface area for application of acoustic material, which will result in less fan noise. In addition, low-compressor stage bleed exit ports radially flow core air into the bypass air stream and are positioned at discrete locations circumferentially around the cowl. 
     It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are susceptible of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its spirit and scope as defined by the claims.