Patent ID: 6292763
Filing Date: 2001-09-18
Classification: F01D,F02C,F02K,F04D

Abstract:
A method for designing a variable cycle gas turbine engine, said variable cycle gas turbine engine having a fan assembly with a maximum air flow there through and a maximum pressure ratio there across during operation at a fan speed, said fan assembly having a plurality of variable pitch vanes, comprising the steps of:(a) selecting a first operating point of the variable cycle gas turbine engine at a fan speed having about said maximum air flow through said fan assembly at a pressure ratio substantially less than said maximum pressure ratio;(b) selecting a second operating point of the variable cycle gas turbine engine at about said fan speed, said second operating point having about said maximum pressure ratio across said fan assembly at an air flow through said fan assembly substantially less than said maximum air flow;(c) selecting a reference point having a reference air flow through said fan assembly and a reference pressure ratio across said fan assembly;(d) determining a geometry of said variable pitch vanes such that said variable pitch vanes can operate at said reference point without stalling;(e) determining whether said variable pitch vanes stall at said second operating point and repeating steps (c) and (d) until said variable pitch vanes do not stall at said second operating point;(f) determining an efficiency of said fan assembly at said first operating point and repeating steps (c) to (e) until said efficiency is at least about equal to a predetermined efficiency; and(g) employing the variable pitch vane geometry from step (d) for design of said variable cycle gas turbine engine.