Pulse detonation engines, active flow control, nano-engineered materials and open rotor noise reduction were among the technologies on show when I toured General Electric's Global Research Center in upstate New York this week.
You can see some of the technologies in action at the research centre’s blog, From Edison’s Desk, at www.grcblog.com. (Thomas Edison’s actual desk is in the foyer of the centre.)
Many of the technologies are aimed at GE’s jet engine business, but some have application elsewhere in the aircraft. It was a glimpse into the future - how far into the future I’m not sure.
A detonation wave exits a PDE (GE photo)
PDEs are pulsejets that use supersonic detonation rather than subsonic combustion to produce thrust. With almost no moving parts, they are simpler and lighter than gas turbines, and more fuel-efficient.
GE believes PDEs could replace turbomachinery cores in 10 years for industrial gas turbines and within 20 for aero-engines. But a lot of work lies ahead, and research centre is just preparing to mate its experimental PDE to a small turbine to see how well it extracts power from the rapid-fire pulses.
Even through the thick wall of the test cell, the experimental PDE was loud, each of its three tubes firing 20 times a second. And it looked crude, even compared with GE’s first jet engine, the J33, one of which sits at propulsion lab’s entrance - having been purchased via ebay! But it shows promise.
In the nearby fluidics lab was a bewildering array of devices for the active control of airflow and combustion – vibrating panels that act as on-demand vortex generators; synthetic jets that help keep airflow attached and reduce wake turbulence; pulse-detonation actuators that could allow fluidic thrust-vectoring.
Most astonishing were the cold plasma actuators, thin-film electronic devices on the aerofoil surface that accelerate the airflow, keeping it attached and reducing drag (even potentially producing thrust). A variation on this technology could keep the combustor flame lit to leaner fuel:air ratios than possible in today’s engines.
Over in another lab, researchers are working to reduce engine noise. Finding ways to reduce the noise tones caused when fan-blade wakes fit outlet guide-vanes. Looking at how to improve the mixing of core and bypass air to reduce jet noise.
The centre has restarted work on reducing the noise produced by open-rotor engines because of their potential to power next-generation narrowbody airliners. Researchers think they have ways to allow open rotors to meet Stage 4 noise limits, but say they won’t be ready until the latter half of next decade.
Located elsewhere on the campus, and looking further in the future, GE’s nanotechnology lab is turning to nature for inspiration. The natural crack-stopping microstructure of conch shells has led to work on impact-resistant nanostructured ceramics. The water-repelling lotus leaf has lead to work on superhydrophobic metals.
Self-assembled nanostructured ceramic (GE photo)
More-robust ceramics could allow higher temperatures within jet engines without the need for efficiency-sapping cooling air. Surfaces or coatings with nanotextures that repel water could reduce ice adhesion on aerofoils and prevent oil and soot from fouling blades. The possibilities seem limitless, if still rather distant.