One of my favourite songs as a child was “It’s not easy being green” as sung by Kermit the Frog. Can you blame me? I was taller than everyone else in my class, including the teacher. I stood out like a sore thumb.
If you’re an engine manufacturer today, you just might find yourself humming that tune as you stare at the face of one very tall order - airlines want a new narrowbody aircraft that is ultra-fuel efficient, dramatically cuts emissions AND offers big gains in economics (and doesn't split your eardrums). Oh yes, and they’d like to have it in about seven years (some even earlier). It’s a lofty request. And even the biggest Boeing 737 operator in the world, Southwest Airlines, has expressed the difficulty that proposition entails.
“Some of these goals like super-low emissions and super-low noise and super-low NOx and super-low CO2 are diametrically opposed to each other when you get down to the basic chemistry and physics of it,” says Southwest senior director of engineering and maintenance programs Dale Stolzer, noting that “you can design an engine that’s fuel efficient, and lower NOx” but you will have to compromise elsewhere, such as on noise.
Southwest was one of the first carriers to call for the start of work on a new aircraft to counter the rising cost of fuel. I remember a luncheon in DC two years ago during which Southwest co-founder Herb Kelleher said Boeing should incorporate 787 technology into a new 737 design. Unlike other airlines that have shown open preference for open rotor engine technology, however, Southwest has been relatively quiet on this point.
Stolzer says that an ideal 737 replacement for Southwest would be a next generation narrowbody that offers the purported operational efficiencies over current designs but has “a common type rating” with the 737. Check out my article here.
Whether such a replacement will include open rotor technology remains to be seen. To be sure, engine makers are pushing ahead with new designs. During the recent Singapore Airshow, CFM International - the joint venture between Snecma and GE – reiterated that it is “actively pursing counter-rotating fan technology, as well as open rotor designs that build on the experience of the unducted fan from the late 1980s”. Two potential open rotor designs are being validated for an engine in the 25,000-pound (111 kN) thrust class that could provide a 35:1 bypass ratio.
I think Kermit would approve. As he says, green is “beautiful and I think it’s what I want to be”.
on February 27, 2008 1:56 PM | Reply
I was always partial to 'Ladybug Picnic'
:)
on February 28, 2008 6:15 PM | Reply
Are there any indications of where the "tug-of-war" 'twixt low emissions and low noise will eventually settle out? A reduction in fuel use (and associated emissions) of several percent could be achieved very simply by letting the engines run as loud as possible, but this has very negative implications for people (and other animals) near airports. Somewhere there's a balance. Do you know where that is? Do you think anyone knows right now?
on February 29, 2008 10:45 AM | Reply
Why not add "and makes a significant contribution to World Peace" as well. It is such a tall order that you might as well go for the whole schebang.
Seriously though, I would guess that the next great leap forward for better engine performance would be in increasing the computing power on a jet - monitoring actual outputs (emissions and power) and inputs (pilot commands and fuel used) and computing the best combinations would provide as good yields as the physical design of the new power units.
on March 1, 2008 12:47 AM | Reply
With respect to the emissions reduction/noise reduction balance, it appears to be anybody's guess right now. IATA is studying the issue and hopes its members will be able to offer a unified voice, especially since this will make its job easier on the regulatory front. Convincing airport-area residents to accept vastly louder aircraft, however, may be a very tough proposition, no matter the efficiency gains.