A gas turbine engine is provided. The gas turbine engine includes a turbomachine defining an engine inlet to an inlet duct, a fan duct inlet to a fan duct, and a core inlet to a core duct; a primary fan driven by the turbomachine; and a secondary fan located downstream of the primary fan within the inlet duct. The gas turbine engine defines a thrust to power airflow ratio between 3.5 and 100 and a core bypass ratio between 0.1 and 10, wherein the thrust to power airflow ratio is a ratio of an airflow through a bypass passage over the turbomachine plus an airflow through the fan duct to an airflow through the core duct, and wherein the core bypass ratio is a ratio of the airflow through the fan duct to the airflow through the core duct.

A gas turbine engine is provided. The gas turbine engine includes: a turbomachine having a compressor section, a combustion section, and a turbine section arranged in serial flow order, the compressor section having a high pressure compressor defining a high pressure compressor exit area (A.sub.HPCExit) in square inches; wherein the gas turbine engine defines a redline exhaust gas temperature (EGT) in degrees Celsius, a total sea level static thrust output (Fn.sub.Total) in pounds, and a corrected specific thrust, wherein the corrected specific thrust is greater than or equal to 42 and less than or equal to 90, the corrected specific determined as follows: Fn.sub.Total?EGT/(A.sub.HPCExit.sup.2?1000).

A gas turbine engine comprises a main compressor section having a high pressure compressor with a downstream discharge, and more upstream locations. A turbine section has a high pressure turbine. A tap taps air from at least one of the more upstream locations in the compressor section, passes the tapped air through a heat exchanger and then to a cooling compressor. The cooling compressor compresses air downstream of the heat exchanger, and delivers air into the high pressure turbine. The cooling compressor is connected to be driven with at least one rotor in the main compressor section. A source of pressurized air is selectively sent to the cooling compressor to drive a rotor of the cooling compressor to rotate, and to in turn drive the at least one rotor of the main compressor section at start-up of the gas turbine engine. An intercooling system is also disclosed.

A gas turbine engine comprises a fan at an axially outer location, the fan rotating about an axis of rotation, delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct. Air from the inner core duct is directed into a compressor, and then flows axially in a direction back toward the fan through a combustor section, and across a core turbine section, and is then directed into the middle duct. A gear reduction drives the fan from a fan drive turbine section. A method of operating a gas turbine engine is also disclosed.

A gas turbine engine comprises a fan at an axially outer location, the fan rotating about an axis of rotation, delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct. Air from the inner core duct is directed into a compressor, and then flows axially in a direction back toward the fan through a combustor section, and across a core turbine section, and is then directed into the middle duct. A gear reduction drives the fan from a fan drive turbine section. A method of operating a gas turbine engine is also disclosed.

A gas turbine is provided, the gas turbine engine including a turbomachine having an inlet splitter defining in part an inlet to a working gas flowpath and a fan duct splitter defining in part an inlet to a fan duct flowpath. The gas turbine engine also includes a primary fan driven by the turbomachine defining a primary fan tip radius R1, a primary fan hub radius R2, and a primary fan specific thrust rating TP; and a secondary fan downstream of the primary fan and driven by the turbomachine, the secondary fan defining a secondary fan tip radius R3, a secondary fan hub radius R4, and a secondary fan specific thrust rating TS; wherein the gas turbine engine defines an Effective Bypass Area, and wherein a ratio of R1 to R3 equals $\frac{R_1}{R_3}=\sqrt{\left(\mathrm{EFP}\right)\frac{\left(1-{\mathrm{RqR}}_{\left(\mathrm{Sec}.-\mathrm{Fan}\right)}^2\right)}{\left(1-{\mathrm{RqR}}_{\mathrm{Prim}.-\mathrm{Fan}}^2\right)}\left(\frac{T_P}{T_S}\right)\left(\mathrm{EBA}\right)}.$

A turbojet of the unducted rotor type and an aircraft including such a turbojet, the turbojet comprising a gas generator (3-8), a first unducted propeller (21) connected to a shaft (81) of the gas generator (3-8) via first reduction gearing (23), and a second unducted propeller (91) connected to a shaft (81) of the gas generator (3-8) via second reduction gearing (93), wherein the first propeller (21) and the first reduction gearing (23) are mounted at the front of the gas generator (3-8), and wherein the second propeller (91) and the second reduction gearing (93) are mounted at the rear of the gas generator (3-8).

A gas turbine engine comprises a fan at an axially outer location, the fan rotating about an axis of rotation, delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct. Air from the inner core duct is directed into a compressor, and then flows axially in a direction back toward the fan through a combustor section, and across a core turbine section, and is then directed into the middle duct. A gear reduction drives the fan from a fan drive turbine section. A method of operating a gas turbine engine is also disclosed.

A gas turbine engine comprises a fan at an axially outer location, the fan rotating about an axis of rotation, delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct. Air from the inner core duct is directed into a compressor, and then flows axially in a direction back toward the fan through a combustor section, and across a core turbine section, and is then directed into the middle duct. A gear reduction drives the fan from a fan drive turbine section. A method of operating a gas turbine engine is also disclosed.

A gas turbine engine is provided. The gas turbine engine includes: a turbomachine having a compressor section, a combustion section, and a turbine section arranged in serial flow order, the compressor section having a high pressure compressor defining a high pressure compressor exit area (A.sub.HPCExit) in square inches; wherein the gas turbine engine defines a redline exhaust gas temperature (EGT) in degrees Celsius, a total sea level static thrust output (Fn.sub.Total) in pounds, and a corrected specific thrust, wherein the corrected specific thrust is greater than or equal to 42 and less than or equal to 90, the corrected specific determined as follows: Fn.sub.Total?EGT/(A.sub.HPCExit.sup.2?1000).