NASA and GE will conduct cooperative research on initial open rotor concepts to determine noise and performance characteristics in Glenn’s 9’x15’and 8’x6’ wind tunnels.The test model is approximately one-sixth the size of a full-scale engine. Up to seven blade designs will be tested on Glenn’s counter-rotating propulsion rig (also known as the open rotor propulsion rig). Each design will be evaluated for aerodynamic performance (actual thrust output versus predicted) and acoustic performance (noise generated in the “far field,” or the surrounding community). Wind tunnel tests will be performed both at low speed, which simulates initial takeoff or landing, and at high speed, which simulates cruising at Mach .7 to Mach .8.

The current test program represents the renewal of an old partnership. GE and NASA first began working on open rotor concepts in the 1970s, and the research continued for the better part of two decades. When the price of oil plummeted in mid-1990s, however, the viability of an open rotor propulsion system disappeared, and the project lost support.

Chris Hughes, manager of the Ultra-High Bypass (UHB) Engine Technology Development Partnership Element at Glenn for the Fundamental Aeronautics Program Subsonic Fixed Wing Project, notes that there have been enormous strides in technology since the first generation of open rotor testing. “The tools to analyze these technologies — the fan blades — have come a long way in the last 15-20 years. We’re now working with three-dimensional type airfoil sections, all custom-made,” he says. “It used to be in the old days that we went with the old NACA blade sections and stacked them up to make the propeller blade, but now with the computing power and the (software) codes we have, we’re able to custom design the airfoil shapes to get the best performance.”

The most important advances have been in the area of modeling and simulation tools. “There has been a lot of advancement in technology and prediction tools that can help us now address the things that we were not able to address back in the 1980s, such as how we can make this configuration more acoustic-friendly,” says Ruben Del Rosario, Project Manager of the Subsonic Fixed Wing Project in ARMD’s Fundamental Aeronautics Program.

The potential gains in engine performance could also result in cleaner aircraft engines in the future. “This design is being put forth not only to address fuel burn and noise, but also environmental concerns. Less fuel burn means less carbon footprint,” says Hughes. “The emissions goals of NASA would be addressed with this particular concept.”

The refurbishment of the open rotor drive rig for the wind tunnel tests was supposed to take six to nine months, but once the work began it became clear that the overhaul would require closer to a year. “One of the things that came up for us was just how old our technology was from our propulsion rig from the 1980s,” Hughes says. “We ended up having to do a lot more work (than anticipated) to bring it up to quality standards in terms of data.”

Hughes sees the investment as a technology enabler that will pay off for NASA. “We had requests from every (aircraft) engine company wanting to know how they could get involved with this, because really low fuel burn and high performance numbers are the way of the future,” he said. “Everybody is interested. Now that we have this capability, everybody wants to come and use it.”

Del Rosario views the new partnership with GE as a model for future collaboration between NASA and industry. “We were able to reach an agreement where we could satisfy our mission, which is to share data openly with the whole world about what we learn, and at the same time GE is getting some testing time and some additional data that they need. It is a win-win situation for NASA ARMD and GE.”