Abstract: A method and apparatus for producing a design for a system (2) that comprises a plurality of subsystems (4, 6) is provided. Criteria to be satisfied by the system (2) are identified. For each subsystem (4, 6), further criteria that are to be satisfied by that subsystem (4, 6) are determined and a parametric model (8, 16) is then determined. These comprise inputs (10, 18) and outputs (14, 22) that are dependent on the inputs (10, 18). A systems engineering model (100) comprising, as inputs, parametric model inputs (10, 18) is then determined. System model outputs (28) are dependent on the system model inputs. Groups consisting of some of the system model inputs are formed and an optimization process is performed, for each group, to determine inputs that optimize the system model outputs (28). A set of inputs that optimize the system model outputs (28) provides a design for the system.

Abstract: A leaf seal is proposed for effecting a seal between two coaxial and relatively rotating components. The seal has an annular pack of stacked leaves, the pack being mountable to a first one of the components at root portions of the leaves and extending towards the other component such that end edges of the leaves cooperate to define a seal surface of the pack which is presented for air-riding interaction with a surface of the other component during relative rotation between the components such that, in use, a pressure drop is maintained axially across the pack. The seal surface of the pack incorporates a plurality of hydrodynamic lift-generating recesses spaced circumferentially around the pack. Each said recess extends circumferentially across a plurality of adjacent leaves in the pack, each of which leaves being spaced radially from said surface of the other component along at least part of its end edge.

Abstract: A method and apparatus for producing a design for a system (2) that comprises a plurality of subsystems (4, 6) is provided. Criteria to be satisfied by the system (2) are identified. For each subsystem (4, 6), further criteria that are to be satisfied by that subsystem (4, 6) are determined and a parametric model (8, 16) is then determined. These comprise inputs (10, 18) and outputs (14, 22) that are dependent on the inputs (10, 18). A systems engineering model (100) comprising, as inputs, parametric model inputs (10, 18) is then determined. System model outputs (28) are dependent on the system model inputs. Groups consisting of some of the system model inputs are formed and an optimisation process is performed, for each group, to determine inputs that optimise the system model outputs (28). A set of inputs that optimise the system model outputs (28) provides a design for the system.

Abstract: A leaf seal is proposed for effecting a seal between two coaxial and relatively rotating components. The seal has an annular pack of stacked leaves, the pack being mountable to a first one of the components at root portions of the leaves and extending towards the other component such that end edges of the leaves cooperate to define a seal surface of the pack which is presented for air-riding interaction with a surface of the other component during relative rotation between the components such that, in use, a pressure drop is maintained axially across the pack. The seal surface of the pack incorporates a plurality of hydrodynamic lift-generating recesses spaced circumferentially around the pack. Each said recess extends circumferentially across a plurality of adjacent leaves in the pack, each of which leaves being spaced radially from said surface of the other component along at least part of its end edge.