A gas turbine engine includes a very high speed low pressure turbine such that a quantity defined by the exit area of the low pressure turbine multiplied by the square of the low pressure turbine rotational speed compared to the same parameters for the high pressure turbine is at a ratio between about 0.5 and about 1.5.

An unducted thrust producing system has a rotating element with an axis of rotation and a stationary element. The rotating element includes a plurality of blades, each having a blade root proximal to the axis, a blade tip remote from the axis, and a blade span measured between the blade root and the blade tip. The rotating element has a load distribution such that at any location between the blade root and 30% span the value of RCu in the air stream is greater than or equal to 60% of the peak RCu in the air stream.

For alignment of rotational shafts, two devices for attachment to circular faces of two shaft segments. Each of the two devices has a laser photoelectric device for ascertaining a dimension of displacement of the two shafts from a desired axis of rotation relative to each other. Each of the two devices having a base surface with two linear contact edges designed to engage with a circumferential surface of a shaft and to ensure alignment between the device and an axis of rotation of the shaft to within a tolerance compatible with alignment tolerances of the shaft. Each of the two linear contact edges includes at least two terminal end regions and a center region together defining a line contact at linear intersection of two surfaces meeting at a non-zero angle linear contact edges designed to affix and release from the shaft surface, and to ensure parallel alignment between the device and an axis of rotation of the shaft to a precision allowing measurements to within tolerances required by machinery driven by the shaft. The base surface of at least one of the devices has been modified from its commercially-delivered condition to provide raised rails designed to improve tactile feedback of to a user of the alignment between the base and an axis of rotation of the shaft, and has affixed thereto two rails designed to improve tactile feedback of to a user of the alignment between the base and an axis of rotation of the shaft. Each base has a magnet and a switch to vary magnetic flux for affixation and release from the shaft surface. Each device has brackets designed to securely and reproducibly position laser photoelectric devices relative to the base and axis of rotation of the shaft. The attaching includes a human placing at least one of the devices slightly askew relative to the axis of rotation of the shaft, and the human gently twisting the device to allow the liner contact edges to seat on the circumferential surface of the shaft, to provide tactile feedback to the human to confirm parallel alignment between the at least one device's laser photoelectronic device and the axis of rotation of the shaft.

An unducted thrust producing system has a rotating element with an axis of rotation and a stationary element. The rotating element includes a plurality of blades each having a blade root proximal to the axis, a blade tip remote from the axis, and a blade span measured between the blade root and the blade tip. The rotating element has a load distribution such that at any location between the blade root and 30% span the value of ?RCu in the air stream is greater than or equal to 60% of the peak ?RCu in the air stream.

A gas turbine engine according to an example of the present disclosure includes a turbine section having a very high speed fan drive turbine such that a quantity defined by the exit area of the fan drive turbine multiplied by the square of the fan drive turbine rotational speed compared to the same parameters for a second turbine is at a ratio between 0.5 and 1.5. The engine includes a power density greater than 1.5 lbf/in.sup.3.

A turbine debris filter apparatus for preventing clogging of cooling holes of a turbine vane, the apparatus including a filter having non-planar geometry configured to be disposed upon a shroud of the turbine vane and a support including an interface to which the filter is attached and an opening for allowing air flow, wherein the interface is configured to receive and support the non-planar geometry and the opening is configured to align with an air inlet of the shroud.

A gas turbine engine includes a very high speed low pressure turbine such that a quantity defined by the exit area of the low pressure turbine multiplied by the square of the low pressure turbine rotational speed compared to the same parameters for the high pressure turbine is at a ratio between about 0.5 and about 1.5.

A gas turbine engine comprises a fan for delivering air into a bypass duct as bypass flow, into a core housing as core flow, with the core housing containing an upstream compressor rotor and a downstream compressor rotor. An overall pressure ratio is defined across the upstream and downstream compressor rotors. A bypass ratio is defined as a volume of air delivered as bypass flow compared to a volume of air delivered into the core housing. The overall pressure ratio is greater than or equal to about 45.0, and the bypass ratio is greater than or equal to about 11.0.

A gas turbine engine comprises a fan for delivering air into a bypass duct as bypass flow, into a core housing as core flow, with the core housing containing an upstream compressor rotor and a downstream compressor rotor. An overall pressure ratio is defined across the upstream and downstream compressor rotors. A bypass ratio is defined as a volume of air delivered as bypass flow compared to a volume of air delivered into the core housing. The overall pressure ratio is greater than or equal to about 45.0, and the bypass ratio is greater than or equal to about 11.0.

A gas turbine engine has a compressor section, a compressor case substantially surrounding the compressor section, and a diffuser case attached at an attachment interface to the compressor case. The attachment interface is between a forward and an aft end of the compressor. A geared turbofan is also disclosed.