Patent ID: 7921637

Claim:
A high bypass-ratio turbofan jet engine, comprising: a core engine that generates a propulsive force by ejecting combustion gas rearward; and a fan that generates a propulsive force by ejecting an airflow rearward while compressing the airflow, and suppresses a noise of an exhaust stream of the core engine, wherein the fan includes a front fan disposed in the vicinity or upstream of a compressor of the core engine, and an aft fan disposed in the vicinity or downstream of a turbine, and wherein a front fan duct that discharges air compressed by the front fan to the outside and an aft fan duct that introduces air into the aft fan are disposed along a longitudinal direction of the core engine in such a manner to spirally twist relative to each other such that cross-sectional shapes of the front fan duct and the aft fan duct change relative to each other by rotating around the core engine in one direction.