A gas turbine engine includes a fan section, a gear arrangement configured to drive the fan section, a compressor section and a turbine section. The compressor section includes a low pressure compressor section and a high pressure compressor section. The turbine section is configured to drive compressor section and the gear arrangement. An overall pressure ratio, which is provided by a combination of a pressure ratio across said low pressure compressor section and a pressure ratio across said high pressure compressor section, is greater than about 35. The pressure ratio across the low pressure compressor section is between about 3 and about 8 whereas the pressure ratio across the high pressure compressor section is between about 7 and about 15.

Gas turbine engine compressor arrangement

A gas turbine engine includes a fan shaft and a support which supports the fan shaft. The support defines at least one of a support transverse and a support lateral stiffness. A gear system drives the fan shaft. A flexible support at least partially supports the gear system, and defines at least one of a flexible support transverse and a flexible support lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness. An input to the gear system defines at least one of an input transverse and an input lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness. A method of designing a gas turbine engine is also disclosed.

Flexible support structure for a geared architecture gas turbine engine

Gas turbines with multiple gas flow paths are provided. In this regard, a representative gas turbine includes: a spool; a compressor; a turbine mechanically coupled to the spool; the compressor having a first set of blades and a second set of blades, the second set of blades being located downstream of the first set of blades, the first set of blades and the second set of blades being driven by the spool; and means for enabling the first set of blades to rotate at a lower rotational speed than the second set of blades.

Gas Turbines with Multiple Gas Flow Paths

Gas turbine engine systems involving tip fans are provided. In this regard, a representative gas turbine engine system includes: a multi-stage fan having a first rotatable set of blades and a second counter-rotatable set of blades, the second rotatable set of blades defining an inner fan and a tip fan and being located downstream of the first set of rotatable blades; and an epicyclic differential gear assembly operative to receive a torque input and differentially apply the torque input to the first set of blades and the second set of blades.

Gas turbine engine systems involving tip fans

A gas turbine engine according to an exemplary aspect of the present disclosure includes a gear train defined along an engine centeriine axis, and a spool along said engine centeriine axis which drives the gear train, the spool includes a low stage count low pressure turbine. In a further non-limiting embodiment of any of the foregoing gas turbine engine embodiments, the low stage count may include three to six (3-6) stages. Additionally or alternatively, the low stage count may include three (3) stages. Additionally or alternatively, the low stage count may include five (5) or six (6) stages.

Gas turbine engine with low stage count low pressure turbine

An impeller is directly driven by an output shaft of a core engine. The airflow produced by the impeller rotates an air turbine and a fan disposed integrally with the air turbine. The impeller and the air turbine form a fluid coupling which serves also as a speed reducing mechanism. The rotational speed of the fan can be reduced to be lower than that of the output shaft while retaining efficiency of the core engine. The outer diameter of the fan can be increased, raising a bypass ratio.

Hideo Takeda

Papers

Turbofan engine including fans with reduced speed