United Technologies Corporation

Raytheon Technologies Corporation

William H Greene, Jr

Jorn Axel Glahn

Matthew R Feulner

John P Virtue

Matthew D Teicholz

Jason B Solomonides

Jeffrey W Sutliff

Kenneth J White

Philip D Hoover

Victor M Pinedo

Douglas E Duke

Karl J Yaeger

James A Sunamoto

A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed, where the controller modulates a duty cycle of the discrete starter valve via pulse width modulation.

Modified start sequence of a gas turbine engine

A system for controlling a start sequence of a gas turbine engine includes an electronic engine control system, a thermal model, memory, a model for determining a time period (t), and a controller. The thermal model synthesizes a heat state of the gas turbine engine. The memory records the current heat state at shutdown and a shutdown time of the gas turbine engine. The model for determining the time period is for motoring the gas turbine engine at a predetermined speed Nthat is less than a speed to start the gas turbine engine, where tis a function of the heat state recorded at engine shutdown and an elapsed time of an engine start request relative to a previous shutdown time. The controller modulates a starter valve to maintain the gas turbine engine within a predetermined speed range of Nto Nfor homogenizing engine temperatures.

A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed.

An array (32) of flow directing elements such as fan blades (20) for a turbine engine (10) is disclosed. Each blade in the array has a set of circumferentially shrouds (42, 44) whose contact edges (46, 48) abut each other during engine operation. A shroud angle .sigma. establishes the running chord angle .alpha. of the airfoil (30) portion of the array. Slight differences in the shroud angles of adjacent blades cause corresponding differences in the running chord angles so that the array is detuned and airfoil flutter is precluded.

Flutter resistant blades, vanes and arrays thereof for a turbomachine

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Coventry, CT, United States of America

William H Greene, Jr