Turbine arrangement

Abstract

A turbine arrangement for a gas turbine engine having a sloped gas flowpath through the turbine. The radial axes of the rotor blades and stator vanes in the sloped flowpath are tilted such that the axes are substantially normal to the mean flow streamline of the gases. This arrangement reduces tip losses and thereby increases engine efficiency.

What is claimed is: 
     
       1. In a gas turbine engine arranged substantially concentrically about a longitudinal axis thereof, a turbine arrangement for receiving and being rotated by hot gases exiting a combustor of said engine, said turbine arrangement comprising: a. an annular gas flowpath disposed about said engine longitudinal axis and defined by radially inner and outer boundaries, said flowpath being arranged such that in a downstream direction through at least a forward portion of said flowpath, a mean flow streamline of said hot gases flowing therethrough slopes away from said engine longitudinal axis and said flowpath increases in annular height; and   b. a plurality of blade rows and vane rows spaced alternately and within said flowpath, each of said blade rows and each of said vane rows comprising a plurality of circumferentially spaced rotor blades and stator vanes, respectively, said rotor blades extending radially outwardly from a turbine rotor, the rotor blades and the stator vanes of said blade and vane rows within said forward portion of said flowpath having radial axes tilted forward at an angle less than 90° from said engine longitudinal axis so that said radial axes are substantially normal to said mean flow streamline;   said forward portion of said gas flowpath having a slope greater than that of a reference flowpath wherein raidal axes of reference rotor blades are disposed substantially normal to said longitudinal axis, said forward portion of said gas flowpath being effective for increasing the slope of said gases flowing therethrough for permitting said rotor blades to be disposed at greater radial distances for more efficient transfer of energy from said gases to said turbine rotor relative to said reference flowpath.   
     
     
       2. The turbine arrangement of claim 1 wherein a downstream portion of said flowpath is arranged so that said mean flow streamline is substantially parallel to said engine longitudinal axis and at least one of said plurality of blade and vane rows has radial axes disposed substantially normal to said engine longitudinal axis for directing engine thrust substantially parallel to said longitudinal axis. 
     
     
       3. The turbine arrangement of claim 1 wherein said flowpath is arranged so that the angle which said mean flow streamline makes with said engine longitudinal axis decreases from an upstream end to a downstream end of said flowpath. 
     
     
       4. The turbine arrangement of claim 1 wherein the radial axes of said rotor blades and said stator vanes of all of said blade and vane rows of the turbine are arranged to be substantially normal to said mean flow streamline. 
     
     
       5. The turbine arrangement of claim 1 wherein said rotor blades include base portions disposed outside of said flowpath, said base portions having radial axes aligned normal to said engine longitudinal axis. .[.6. For a gas turbine engine including a combustor effective for generating combustion gases and a turbine effective for receiving said gases for driving a rotor, a method for arranging said turbine comprising the steps of: arranging an annular gas flowpath in a reference flowpath disposed about a longitudinal axis of said engine and defined by radially inner and outer boundaries, said flowpath being arranged so that in a downstream direction through at least a forward portion of said flowpath a means flow streamline of said combustion gases flowing therethrough slopes away from said engine longitudinal axis and said flowpath increases in annular height;   arranging a plurality of blade rows and vane rows spaced alternately and within said reference flowpath, each of said blade rows and each of said vane rows comprising a plurality of circumferentially spaced rotor blades and stator vanes, respectively, said rotor blades extending radially outwardly from said rotor, the rotor blades and the stator vanes of said blade and vane rows within said forward portion of said flowpath having radial axes disposed at about 90° from said engine longitudinal axis;   said reference flowpath and said blade and vane rows being arranged so that aerodynamic losses of said gases flowing over radially outer tip portions of said rotor blades are at acceptable standards;   arranging said rotor blades and said stator vanes within said forward portion of said flowpath so that said radial axes are tilted forward at an angle less than 90° from said engine longitudinal axis; and   arranging said annular gas flowpath so that said mean flow streamline of said forward portion of said flowpath slopes at angles greater than those in said reference arrangement thereof..]. .[.7. A method for arranging a turbine according to claim 6 further including:   arranging said plurality of blade rows and vane rows so that said blade and vane rows within said forward portion of said flowpath are disposed are radii greater than those of said blades and vanes in said reference flowpath for increasing tangential velocities and moment arms of said rotor blades for increasing efficiency of transfer of energy from said gases to said rotor..]. .[.8. A method for arranging a turbine according to claim 6 wherein said rotor blades and stator vanes within said forward portion of said flowpath are arranged so that said radial axes are substantially normal to said mean flow streamline..]. .[.9. In a method of arranging a gas turbine engine of the type including a combustor effective for generating combustion gases and a turbine effective for receiving said gases for driving a rotor, said turbine including an annular gas flowpath having a forward portion wherein a mean flow streamline slopes away from an engine longitudinal axis in a downstream direction and a plurality of blade rows and vane rows spaced alternately and within said flowpath, said blade rows extending radially outwardly from said rotor, the steps of:   arranging said blade rows and said vane rows within said forward portion of said flowpath for having radial axes tilted forward at an angle less than 90° from said engine longitudinal axis; and   arranging said annular gas flowpath so that said mean flow streamline of said forward portion of said flowpath has an increased slope for increasing efficiency of transfer of energy from said gases to said   
     
     
        rotor..]. 10. In a gas turbine engine including a combustor effective for generating combustion gases and a turbine effective for receiving said gases for driving a rotor, said turbine including an annular gas flowpath having a forward portion wherein a mean flow streamline slopes away from an engine longitudinal axis in a downstream direction and a plurality of blade rows and vane rows spaced alternately and within said flowpath, said blade rows extending radially outwardly from said rotor, an improved turbine comprising: said blade rows within said forward portion of said flowpath having radial axes tilted forward at an angle less than 90° from said engine longitudinal axis; and   said forward portion of said flowpath being arranged so that said mean flow   
     
     
        streamline of said gases has an increased slope. 11. An improved turbine arrangement according to claim 10 wherein said rotor blades are disposed at incrased radii for increasing tangential velocity and moment arm of said rotor blades for increasing efficiency of transfer of energy from 
     
     
        said gases to said rotor. 12. An improved turbine arrangement according to claim 10 wherein said blade rows within said forward portion of said flowpath are arranged said that said radial axes are substantially normal 
     
     
        to said mean flow streamline. .Iadd.13.  In a gas turbine engine including a combustor effective for generating combustion gases and a turbine effective for receiving said gases for driving a rotor, said turbine including an annular gas flowpath having a forward portion and a blade row within said forward portion of said flowpath, said blade row having a plurality of circumferentially spaced rotor blades extending radially outwardly from said rotor, an improved turbine comprising: said forward portion of said flowpath so arranged that said mean flow streamline of said gases slopes away from an engine longitudinal axis in a downstream direction; and   said blades within said forward portion of said flowpath having radial axes tilted forward at an angle less than 90° from said engine longitudinal axis. .Iaddend. .Iadd.14. An improved turbine according to claim 13 wherein said blade row is arranged such that each of said radial axes is substantially normal to said mean flow streamline. .Iaddend.