Back in the mid 1980s, GE and NASA began testing on a new propulsion system that used counter rotating fan assemblies in an attempt to boost efficiency. The testing ultimately led to the design of the GE36 experimental aircraft engine, but was then set aside to explore other options. Now, GE and NASA are planning on revisiting the design and adding some new technology to the mix.
GE36 Demonstration Engine The design is ultimately a hybrid between a Turbofan and Turboprop, which was aptly named a Propfan or Unducted Fan. The process begins by using a turbofan engine with the fans relocated to the outside of the engine housing. As the exhaust from the turbofan engine is forced out, they pass over a turbine which is connected to a prop on the exterior, while the other prop is driven by the turbofan.
Both sets of props have variable pitch blades that featured a dramatic curve, similar to a scimitar, which would allow the engine to reach speeds close to Mach .75. Along with the high flight speeds, the engine also showed a 30% to 35% decrease in fuel consumption. The only real drawback to using a Propfan engine was the noise that was present inside the cabin. This, when combined with a shifting market, ultimately led to the design being shelved.
Skip to today's market, where the price of fuel is driving everyone in the transportation business to find ways to increase efficiency and decrease consumption, and the Propfan engine could change the air transportation industry as we know it.
Refurbished Testing Assembly GE and NASA are planning on performing tests throughout the summer and into next year, using the same rig they had employed for testing on the GE36. They hope the advances in wind tunnel diagnostics and aerodynamic modeling will be able to offer a better picture of the feasibility of the experimental engine.
The testing itself will be conducted at the Glenn Research Center in Ohio and will focus more on the blade design rather than the engine itself. They plan on testing 6 different styles of blades, each with different lengths and sweeps, and determine which is able to provide the best performance for its intended application.
Assuming the tests are successful, it might not be very long until we start to see open rotor engines on commercial aircraft. Aside from decreasing costs for the airline, a 30% reduction in fuel usage would have a huge impact on the prices of airline tickets as well as the amount of emissions being released into our atmosphere. Green Car Congress