Counter rotation power turbine

A gas turbine engine for powering an aircraft at a cruise speed in excess of Mach 0.6 including a longitudinal axis comprising:

• an annular casing disposed coaxially about said axis;
• a gas generator disposed in said casing and including a compressor, combustor and a high pressure turbine in serial flow relationship, said high pressure turbine being effective for first receiving combustion gases from said combustor for driving said compressor through a drive shaft fixedly connected thereto, said gas generator being effective for exhausting said combustion gases therefrom substantially at a mean discharge radius from said longitudinal axis and in an aft direction;
• a power turbine disposed coaxially about said longitudinal axis and including:
• a first drum rotor arranged so as to define an inner flowpath surface for said combustion gases flowing through said power turbine;
• a plurality of first turbine blade rows extending radially outwardly from said first rotor and spaced axially thereon;
• a second drum rotor arranged so as to define an outer flowpath surface for said combustion gases flowing through said power turbine and disposed radially outwardly of said first rotor and said first turbine blade rows;
• and
• a plurality of second turbine blade rows extending radially inwardly from said second rotor and alternately spaced with respective ones of said plurality of said first turbine blade rows;
• said power turbine being effective for receiving said combustion gases from said gas generator and expanding said gases through said first and second turbine blade rows along a mean flowpath radius for extracting substantially all usable output power therefrom for driving said first and second rotors in counterrotating directions at speeds relatively lower than those of said drive shaft;
• a seal disposed between said casing and said second rotor to reduce the flow of combustion gases therethrough;
• and
• first and second counterrotating propellers driven by said first and second rotors, respectively, for producing substantially all thrust generated by said engine.

A gas turbine engine comprising:

• a gas generator effective for generating combustion gases;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a power turbine including a first rotor having a plurality of first turbine blade rows extending radially outwardly therefrom and a second rotor having a plurality of second turbine blade rows extending radially inwardly therefrom, wherein:
• i. said first and second rotors are arranged so as to define inner and outer flowpath surfaces, respectively, for said combustion gases flowing through said power turbine;
• and
• ii. said power turbine is effective for receiving said combustion gases and extracting usable output power therefrom for driving said first and second rotors in counterrotating directions;
• b. first and second counterrotating propellers, for producing substantially all thrust generated by said engine, each with a plurality of blades attached to first and second rotatable nacelle rings, respectively, wherein:
• i. said first and second propellers are directly coupled to and driven by said first and second rotors, respectively, and disposed radially outwardly of said power turbine;
• and
• ii. each of said blades has a relatively high hub radius to tip radius ratio.

A gas turbine engine comprising:

• a gas generator effective for generating combustion gases;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a power turbine including a first rotor having a plurality of first turbine blades extending radially outwardly therefrom and a second rotor having a plurality of second turbine blades extending radially inwardly therefrom, wherein:
• i. said first and second rotors are arranged so as to define inner and outer flowpath surfaces, respectively, for said combustion gases flowing through said power turbine;
• and
• ii. said power turbine is effective for receiving said combustion gases and extracting usable output power therefrom for driving said first and second rotors in counterrotating directions;
• b. first and second counterrotating propellers, for producing substantially all thrust generated by said engine, each with a plurality of blades attached to first and second rotatable nacelle rings at first and second radii, respectively, wherein:
• i. said first and second propellers are directly coupled to and driven by said first and second rotors, respectively, and disposed radially outwardly of said power turbine;
• and
• ii. each of said blades has a relatively high hub radius to tip radius ratio and relatively low thickness to chord ratio;
• c. an annular nacelle disposed radially outwardly of said gas generator and forming an outer contour, said contour having forward, intermediate, and aft portions, wherein:
• said intermediate portion defines the maximum radius of said nacelle which exceeds each of said first and second radii.

A gas turbine engine comprising:

• a gas generator effective for generating combustion gases;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a power turbine including a first rotor having a plurality of first turbine blade rows extending radially outwardly therefrom and a second rotor having a plurality of second turbine blade rows extending radially inwardly therefrom, wherein:
• i. said first and second rotors are arranged so as to define inner and outer flowpath surfaces, respectively, for said combustion gases flowing through said power turbine;
• and
• ii. said power turbine is effective for receiving said combustion gases and extracting usable output power therefrom for driving said first and second rotors in counterrotating directions;
• b. first and second counterrotating propellers, for producing substantially all thrust generated by said engine, each with a plurality of blades attached to first and second rotatable nacelle rings at first and second radii, respectively, wherein:
• i. said first and second propellers are directly coupled to and driven by said first and second rotors, respectively, and disposed radially outwardly of said power turbine;
• and
• ii. each of said blades has a relatively high hub radius to tip radius ratio and relatively low thickness to chord ratio;
• and
• c. an annular nacelle disposed radially outwardly of said gas generator and forming an outer contour, said outer contour being the only surface defining the flowpath of air to said propellers, said contour having forward, intermediate, and aft portions, wherein:
• said intermediate portion defines the maximum radius of said nacelle which exceeds each of said first and second radii.

A gas turbine engine comprising:

• a gas generator effective for generating combustion gases and having an annular casing disposed circumferentially thereabout;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a power turbine including a first rotor having a plurality of first turbine blade rows extending radially outwardly therefrom and a second rotor having a plurality of second turbine blade rows extending radially inwardly therefrom, wherein:
• i. said first and second rotors are arranged so as to define inner and outer flowpath surfaces, respectively, for said combustion gases flowing through said power turbine;
• and
• ii. said power turbine is effective for receiving said combustion gases and extracting substantially all output power therefrom for driving said first and second rotors in counterrotating directions;
• b. first and second counterrotating propellers, each with a plurality of blades attached to first and second rotatable nacelle rings at first and second radii, respectively, wherein:
• i. said first and second propellers are directly coupled to and driven by said first and second rotors, respectively, and disposed radially outwardly of said power turbine;
• and
• ii. each of said blades has a relatively high hub radius to tip radius ratio and relatively low thickness to chord ratio;
• c. an annular nacelle disposed radially outwardly of said gas generator and forming an outer contour, said outer contour being the only surface defining the flowpath of air to said propellers, said contour having forward, intermediate, and aft portions, wherein:
• said intermediate portion defines the maximum radius of said nacelle which exceeds each of said first and second radii;
• and
• d. a seal disposed between said casing and said second rotor to reduce the flow of combustion gases therethrough.

A gas turbine engine comprising:

• a gas generator effective for generating combustion gases and having an annular casing disposed circumferentially thereabout;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a power turbine including a first rotor having a plurality of first turbine blade rows extending radially outwardly therefrom and a second rotor having a plurality of second turbine blade rows extending radially inwardly therefrom, wherein:
• i. said first and second rotors are arranged so as to define inner and outer flowpath surfaces, respectively, for said combustion gases flowing through said power turbine;
• ii. said power turbine is effective for receiving said combustion gases and extracting substantially all usable output power therefrom for driving said first and second rotors in counterrotating directions;
• iii. the total number of said first and second rows is less than about 19 rows and more than about 9 rows;
• and
• iv. said combustion gases are exhausted from said gas generator at a mean discharge radius from the longitudinal axis of said engine, said gases are expanded through said power turbine along a mean flowpath radius, and said mean flowpath radius is about double the magnitude of said mean discharge radius;
• b. first and second counterrotating propellers, each with a plurality of blades attached to first and second rotatable nacelle rings at first and second radii, respectively, wherein:
• i. said first and second propellers are directly coupled to and driven by said first and second rotors, respectively, and disposed radially outwardly of said power turbine;
• and
• ii. each of said blades has a hub radius to tip radius ratio which is greater than about 0.4 and a thickness to chord ratio of less than 0.14 at the hub;
• c. an annular nacelle disposed radially outwardly of said gas generator and forming an outer contour, said outer contour being the only surface defining the flowpath of air to said propellers, said contour having forward, intermediate, and aft portions, wherein:
• said intermediate portion defines the maximum radius of said nacelle which exceeds each of said first and second radii;
• and
• d. a seal disposed between said casing and said second rotor to reduce the flow of combustion gases therethrough.

An unducted fan engine for subsonic aircraft comprising:

• a) a gas generator including a compressor, a combustor and a high pressure turbine for driving said compressor,
• b) a power turbine for receiving the hot gases exhausted from said high pressure turbine,
• c) said power turbine including a first rotor having a plurality of turbine blade rows extending radially outwardly therefrom and a second rotor having a plurality of turbine blade rows extending radially inwardly therefrom and interspersed with the blade rows of the first rotor,
• d) said first and second rotors having generally annular inner and outer surfaces defining the flowpath for the hot gases flowing through said power turbine, and
• e) first and second propeller systems each having an annular nacelle ring surrounding the power turbine and a plurality of propeller blades mounted on said ring,
• f) one of said rings being mounted on and driven directly by said first power turbine rotor and the second of said rings being mounted on and driven directly by the second power turbine rotor whereby said propeller systems are rotated in opposite directions by said rotors,
• g) said power turbine being effective to remove energy from the gases passing through it so that said propeller blades are driven thereby to produce substantially all the thrust generated by said engine.

A gas turbine engine for powering an aircraft at a cruise speed in excess of Mach 0.6 comprising:

• a gas generator effective for generating combustion gases;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a counterrotating power turbine which is effective for receiving said combustion gases and extracting usable output power therefrom;
• and
• b. counterrotating propeller blades directly coupled to and driven by said counterrotating power turbine to produce substantially all thrust generated by said engine, said blades having a sweep which provides reduced tip losses when the aircraft travels at a speed in excess of Mach 0.6, as compared with the tip losses which would occur with unswept blades traveling at Mach 0.6 and at the same rotational speed.

An unducted fan engine for subsonic aircraft comprising:

• a. a gas generator including a compressor, a combustor and a high pressure turbine for driving said compressor,
• b. a power turbine for receiving the hot gases exhausted from said high pressure turbine,
• c. said power turbine including a first rotor having a plurality of turbine blade rows extending radially outwardly therefrom and a second rotor having a plurality of turbine blade rows extending radially inwardly therefrom and interdigitated with the blade rows of the first rotor,
• d. said first and second rotors having generally annular inner and outer surfaces defining the flowpath for the hot gases flowing through said power turbine;
• e. first and second propeller systems each having;
• i. an annular nacelle ring surrounding the power turbine,
• ii. a plurality of propeller blades mounted on said ring, and
• iii. pitch control means for varying the pitch of the propeller blades;
• f. one of said rings being mounted on and driven directly by said first power turbine rotor and the second of said rings being mounted on and driven directly by the second power turbine rotor whereby said propeller systems are rotated in opposite directions by said rotors;
• and
• g. said power turbine being effective to remove energy from the gases passing through it so that said propeller blades are driven thereby to produce substantially all the thrust generated by said engine.

A gas turbine engine for powering an aircraft at a cruise speed in excess of Mach 0.6 including a longitudinal axis comprising:

• an annular casing disposed coaxially about said axis;
• a gas generator disposed in said casing and including a compressor, combustor and a high pressure turbine in serial flow relationship, said high pressure turbine being effective for first receiving combustion gases from said combustor for driving said compressor through a drive shaft fixedly connected thereto, said gas generator being effective for exhausting said combustion gases therefrom substantially at a mean discharge radius from said longitudinal axis and in an aft direction;
• a power turbine disposed coaxially about said longitudinal axis and including:
• a first drum rotor arranged so as to define an inner flowpath surface for said combustion gases flowing through said power turbine;
• a plurality of first turbine blade rows extending radially outwardly from said first rotor and spaced axially thereon;
• a second drum rotor arranged so as to define an outer flowpath surface for said combustion gases flowing through said power turbine and disposed radially outwardly of said first rotor and said first turbine blade rows;
• and
• a plurality of second turbine blade rows extending radially inwardly from said second rotor and alternately spaced with respective ones of said plurality of said turbine blade rows;
• said power turbine being effective for receiving said combustion gases from said gas generator and expanding said gases through said first and second turbine blade rows along a mean flowpath radius for extracting su bstantially all output power therefrom for driving said first and second rotors in counterrotating directions at speeds relatively lower than those of said drive shaft;
• a seal disposed between said casing and said second rotor to reduce the flow of combustion gases therethrough;
• first and second counterrotating propellers driven by said first and second rotors, respectively, for producing substantially all thrust generated by said engine;
• and
• pitch control means for independently controlling the pitch of said first and second propellers.

A gas turbine engine for powering an aircraft at a cruise speed in excess of Mach 0.6 comprising:

• a gas generator effective for generating combustor gases;
• and
• means for efficiently transferring the energy of said gases into a net engine thrust, said means including:
• a. a counterrotating power turbine which is effective for receiving said combustion gases and extracting substantially all output power therefrom;
• b. counterrotating propeller blades directly coupled to and driven by said counterrotating power turbine to produce substantially all thrust generated by said engine;
• and
• c. pitch control means for controlling independently the pitch of said counterrotating propeller blades.