Unducted fans for aircraft propulsion

Article By:

Murrow, Kurt Advanced Technology and Preliminary Design Division, GE Aviation, Cincinnati, Ohio.

Breeze-Stringfellow, Andrew Advanced Technology and Preliminary Design Division, GE Aviation, Cincinnati, Ohio.

Wojno, John Advanced Technology and Preliminary Design Division, GE Aviation, Cincinnati, Ohio.

Last reviewed:2012

DOI:https://doi.org/10.1036/1097-8542.YB120383

The application of the gas turbine toward aviation propulsion, leading to the turbojet engines of Frank Whittle and Hans Von Ohain in the late 1930s, redefined aviation transportation for generations to come. The turbojet supplanted the then prevalent internal combustion engine technology with a simple, lightweight, and low-cost alternative. It allowed aircraft to climb to altitudes well beyond those attainable for a conventional internal combustion engine. It also enabled flight speeds to advance from the low subsonic arena of propeller-driven airplanes into the high subsonic and supersonic flight regimes. However, the benefit of increased flight speed offered by the turbojet came at the expense of reduced propulsive efficiency. Propulsive efficiency is a measure of how well jet exhaust power is transferred to the airplane. A slow-turning propeller imparting a small change in velocity over a large stream of air had been replaced with a small but high-velocity airflow to produce thrust.

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