A turbofan engine has an engine case and a gaspath through the engine case. A fan has a circumferential array of fan blades. The engine further has a compressor, a combustor, a gas generating turbine, and a low pressure turbine section. A speed reduction mechanism couples the low pressure turbine section to the fan. A bypass area ratio is greater than about 6.0. The low pressure turbine section airfoil count to bypass area ratio is below about 170.

Aspects of the disclosure are directed to a structure comprising: a plurality of cells, a first non-permeable insert in a first cell of the plurality of cells, the first insert configured to constrict, by at least a first threshold amount, a flow of fluid in the first cell such that: acoustic power over a frequency range is attenuated by the structure by at least a second threshold amount, and a resonant frequency associated with the structure is shifted by at least a third threshold amount.

Aspects of the disclosure are directed to a structure comprising: a plurality of cells, a first non-permeable insert in a first cell of the plurality of cells, the first insert configured to constrict, by at least a first threshold amount, a flow of fluid in the first cell such that: acoustic power over a frequency range is attenuated by the structure by at least a second threshold amount, and a resonant frequency associated with the structure is shifted by at least a third threshold amount.

Apparatus (2) for generating electricity from a tidal or ocean current water flow, which apparatus (2) comprises: a plurality of electrical generators (4) for generating electricity; and each electrical generator (4) comprises a rotor (8), a stator (10), and a housing (12); the housing (12) is a multi-sided housing constructed such that the electrical generators (4) are stably connected together; the apparatus (2) includes positioning means (20) for positioning the apparatus (2) above a waterbed (22); and the apparatus (2) includes position-adjusting means (24) for adjusting the height and/or the direction of the housing (12) such that the housing (12) is always able to be at a height and pointing in a direction for receiving maximum flow of water through the housing (12), and thereby to enable the apparatus (2) to generate a maximum amount of electricity from the water flow.

Apparatus (2) for generating electricity from a tidal water flow, which apparatus comprises: a plurality of electrical generators (4) for generating electricity; and connection means for electrically connecting the electrical generators (4) together; wherein each electrical generator (4) comprises a rotor (6), a stator (8), and a housing (10); the housing (10) is a multi-sided housing constructed such that the electrical generators (4) are stably connectable together; the housing (10) is open at both ends; the stator (8) is inside at least a part of the housing (10); the rotor (6) comprises a plurality of magnets (18) positioned around the periphery of the rotor (6); the magnets (18) are encased in a protective material (20) which protects the magnets (18) from the water; and the rotor (6) has vanes (22) which cause the rotor (6) to rotate within the stator (8) as the water flows through the housing (10).

A turbofan engine has an engine case and a gaspath through the engine case. A fan has a circumferential array of fan blades. The engine further has a compressor, a combustor, a gas generating turbine, and a low pressure turbine section. A speed reduction mechanism couples the low pressure turbine section to the fan. A bypass area ratio is greater than about 6.0. The low pressure turbine section airfoil count to bypass area ratio is below about 170.

A turbofan engine has an engine case and a gaspath through the engine case. A fan has a circumferential array of fan blades. The engine further has a compressor, a combustor, a gas generating turbine, and a low pressure turbine section. A speed reduction mechanism couples the low pressure turbine section to the fan. A bypass area ratio is greater than about 6.0. The low pressure turbine section airfoil count to bypass area ratio is below about 170.

A turbofan engine has an engine case and a gaspath through the engine case. A fan has a circumferential array of fan blades. The engine further has a compressor, a combustor, a gas generating turbine, and a low pressure turbine section. A speed reduction mechanism couples the low pressure turbine section to the fan. A bypass area ratio is greater than about 6.0. The low pressure turbine section airfoil count to bypass area ratio is below about 170.

A panel for lining a gas turbine engine fan casing includes a honeycomb core sandwiched between a backing skin and an outer skin. The backing skin is attached to an inner surface of the casing such that the outer skin forms a radially inward facing surface of a fan duct of the engine. The panel is joined along its sides to similar neighbouring panels such that, in use, the joined panels form a row of panels along the inner surface of the casing. The outer skin or the backing skin includes two face sheets bonded on top of each other, which are arranged such that their edges along each panel side that joins to a neighbouring panel are staggered in the direction of the row. The interfaces between the abutting face sheet edges are therefore correspondingly staggered in the direction of the row.

A diffuser component for a gas turbine is provided, where a fluid flow in the direction of a combustion chamber of the gas turbine can be slowed down by the diffuser component, and a flow cross-section of the diffuser component, which is defined by a diffuser wall is widened to do so. The diffuser wall is at least locally braced, in that at least one stiffening element with a lattice-type structure is provided on the diffuser wall.