Abstract:
A compressor section to be mounted in a gas turbine engine has a plurality of axial compressor rotors arranged from an upstream location toward a downstream location. A tie shaft applies an axial force at one end of the compressor section and biases the compressor rotors against a hub at the opposite end. The downstream compressor is an axial compressor rotor. A gas turbine engine incorporating this structure is also claimed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a gas turbine engine with an axial high pressure compressor, wherein a tie shaft holds the high pressure compressor section together. 
         [0002]    Gas turbine engines are known, and typically include a compressor, which compresses air and delivers it downstream into a combustion section. The air is mixed with fuel in the combustion section and combusted. Products of this combustion pass downstream over turbine rotors, driving the turbine rotors to rotate. 
         [0003]    Typically, the compressor section is provided with a plurality of stages or rotors. Traditionally, these rotors were bolted together and included bolt flanges, or other structure to receive the attachment bolts. Other applications have rotors welded together. 
         [0004]    More recently, it has been proposed to eliminate all of the bolts or weld joints with a single coupling which applies a force through the compressor rotors by using a tie shaft. These proposals have utilized a high pressure compressor with a centrifugal stage as the most downstream compressor rotor, and it is this centrifugal rotor which imparts the force from the tie shaft to the stack of rotors upstream. 
       SUMMARY OF THE INVENTION 
       [0005]    A compressor section to be mounted in a gas turbine engine has a plurality of compressor rotors arranged from an upstream location toward a downstream location. The compressor rotors stack is bounded by one hub at the upstream end and another hub at the downstream end. A tie shaft is secured to one of the hubs and applies an axial force to the opposite hub that will hold together the rotors stack and provide sufficient friction to transmit torque. The compressor is an axial compressor rotor. 
         [0006]    A gas turbine engine incorporating this structure is also claimed. 
         [0007]    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 
         [0008]      FIG. 1  is a cross-sectional view through a gas turbine engine incorporating this invention. 
           [0009]      FIG. 2  shows an alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]    A portion of gas turbine engine  20  is illustrated in  FIG. 1 . A high pressure compressor section  21  includes an upstream hub  24  which is threadably connected at  26  to a tie shaft  22  for the gas turbine engine. A plurality of compressor rotors  28  are aligned axially from left to right in this view, and compress air and pass it downstream toward the combustion section  50 . Spaced between the compressor rotors  28  are a plurality of vanes  30  and  40 . The vanes  30  are variable position vanes, and include actuators or drive structure  31  at an outer periphery, a pivot mounts  29  at both an inner and an outer periphery. 
         [0011]    More downstream fixed position vanes  40  are cantilever mounted, or unsupported at their inner periphery. 
         [0012]    The compressor rotors  30  are clamped together between the upstream and downstream hubs,  24  and  34  respectively using the tie shaft  22  to apply the axial force. The axial force is applied to the downstream hub  34  by nut  32  that is threadably secured to the tie shaft  22 ; the force is transmitted from nut  22  to the downstream hub  34  through an end  35  abutting a ledge  33  on a nut  32 . The upstream hub  34  applies a force at contact face  38  on the most downstream compressor rotor  37 . This rotor  37  includes airfoils  36  positioned to be radially outwardly of contact face  38 . In this manner, force is loaded onto the most downstream compressor rotor section  37 , which in turn applies the force to hold all of the other compressor rotors against the upstream hub  24  and creates the friction necessary to transmit torque. 
         [0013]    The axial force is set by mechanical stretch of tie shaft  22  prior to tightening of nut  32  so that the high friction on the interface between nut  32  and downstream hub  34  is eliminated; a similar stretching of tie shaft  22  is used prior to disassembly. 
         [0014]    Notably, the nut  32  could also be positioned to be upstream of the tie shaft  22 , and provide an appropriate tightening. 
         [0015]    The single tie shaft precludes stresses associated with holes in the compressor rotors, high part count and weight associated with multiple sets of fasteners used at each rotor interface. 
         [0016]    As can be appreciated from  FIGS. 1 , the downstream rotor  37  is an axial compressor. 
         [0017]    While a single blade and a single vane is shown in the  FIG. 1  for each of the stages, it should be appreciated that all of these stages surround a central drive axis for the tie shaft  22 , and include a plurality of circumferentially spaced blades and vanes. 
         [0018]    Further, as can be appreciated, a combustion section  50  is positioned downstream of the compressor section  21 , and a low pressure compressor section  100  is positioned upstream of the high pressure compressor section  21 . Products of combustion from the combustion section  50  pass downstream over a turbine section  60 . The turbine section  60  includes rotors driven to rotate the compressor rotor. The downstream hub  34  provides the coupling between the compressor and turbine sections, in disclosed embodiments. 
         [0019]    As also can be appreciated in  FIG. 1 , the portion of the tie shaft extends upstream, and holds the turbine rotors together also. This feature is better described in co-pending patent application serial number, entitled “Single Tie Rod Connection for Securing Compressor Section and Turbine Section,” filed on even date herewith. 
         [0020]    Downstream hub  34  extends radially outwardly from radially inner end  35 . The radially inner end abuts nut  32  secured to tie shaft  22 , and said radially outer end abutting said downstream compressor rotor. 
         [0021]    The nut or other securement member includes a ledge  33  extending radially outwardly to capture radially inner end  35 . Ledge  33  applies force to downstream hub  34  when the nut is tightened on tie shaft  22 . 
         [0022]    In addition, as can be appreciated, the contact face  38  is radially inward of the blades  36 . The use of the axial compressor as the most downstream compressor thus provides a smaller radial envelope for the compressor section. 
         [0023]      FIG. 2  shows an alternative fixed (non-adjustable) mount between a tie shaft  22  and downstream hub  150 . In this embodiment, the tie shaft  155  has a ledge portion  154  that that abuts against the downstream hub end  152 . Tie shaft  155  is stretched prior to assembly to a preset axial displacement, then released to apply the axial force to the compressor stack. 
         [0024]    Co-pending application serial number , entitled “Compressor Section with Tie Shaft Mount and Cantilever Mounted Vanes” and filed on even date herewith focuses on the use of the downstream cantilever mount vanes. The co-pending patent application serial number , entitled “Single Tie Rod Connection for Securing Compressor Section and Turbine Section” and filed on even date herewith focuses on the assembly of the compressor and rotor sections. In addition, co-pending application serial number , entitled “Gas Turbine Engine Rotor Sections Held Together by Tie Shaft, and With Blade Rim Undercut,” filed on even date herewith, focuses on structure for an integrally bladed rotor. 
         [0025]    Although 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.