In 1983, engineers at General Electric experimented with an “unducted fan” engine. Without the external casing, airflow through the blades increased, delivering more power for the same amount of fuel. The thing was loud, but the company pressed on because the trick could reduce fuel consumption by as much as 26 percent. Then fuel prices dropped, gas guzzling became acceptable, and GE mothballed the project. Now that airlines are again conscious of fuel costs and carbon, the idea is back, and new tech is making it feasible.
Last September, GE began wind-tunnel testing a one-fifth-scale set of the blades at NASA’s Glenn Research Center. Using computational-design advances, engineers are redesigning the original blades to evenly distribute the air coming off the tips when they spin at supersonic speeds, which should reduce the noise. The setup more than triples the airflow through the blades, says Theresa Zeug, the project’s lead engineer, and allows them to be 14 feet wide, four feet wider than today’s largest. The engine also saves fuel by tilting the blades to control speed—rather than throttling up or down—which lets it run at a constant, efficient rate.
GE will probably have to execute some spin of its own to get the public on board with the fearsome design, which engineers have dubbed the “flying Cuisinart.” But GE has time to figure that one out: The engine won’t be ready for midsize jets, such as the Boeing 737, until at least 2020.