Little blade, big role

Photo via Thinkstock.

Photo via Thinkstock.

When­ever I fly, I almost always get seated near the engine. In the past this has made me  grumpy. Not only are those big cylin­ders ridicu­lously loud, they also obstruct my view of the beau­tiful clouds and the earth below. But after meeting with mechan­ical and indus­trial engi­neering pro­fessor Mo Taslim last week I think I’ll be taking a new tack from now on.

He named the beastly gas tur­bine engine among “the major engi­neering won­ders of the 20th-​​century.” While GTs were orig­i­nally devel­oped 80 years ago, they’ve come into their own of late, reaching “near per­fec­tion” according to Taslim.

First, a quick primer for those of you who know as much about gas tur­bine engines as I did a week ago (which is to say, absolutely nothing). The front of the engine con­sists of a ginor­mous fan, whose swirling motion sucks air into the vessel and through a com­pressor before it gets mixed with fuel and then set aflame to reach tem­per­a­tures of a few thou­sand degrees Fahren­heit! The air is then shot out the back end of the com­bus­tion chamber and through a tur­bine (hence the name), which is cov­ered in hun­dreds of little blades, called air­foils, col­lec­tively spin­ning at rates between about 30 thou­sand and 50 thou­sand rota­tions per minute, depending on the appli­ca­tion (aka supremely fast).

While Taslim studies the whole “hot sec­tion” of the gas tur­bine engine, he’s par­tic­u­larly enam­ored of the air­foils. Here’s why: if just one of these little blades fails, it takes the whole entire engine down with it. The whole entire $12 mil­lion engine in the $200 mil­lion plane, that is.

Each blade costs on the order of sev­eral thou­sand dol­lars, Taslim told me, so clearly you’d want to be as effi­cient as pos­sible in making air­foils, not to men­tion keeping them in ship shape.

Both of these are chal­lenges that Taslim and his lab have been working on for a few decades. With funding from a recently awarded grant from GE Avi­a­tion, they’re working on yet another design for the air­foils that will hope­fully make them last longer as well as make them cheaper to manufacture.

For air­foils, there’s one major thing standing in the way of  a long life­time: high tem­per­a­tures and par­tic­u­late debris. To deal with that stag­ger­ingly high tem­per­a­ture, some research team are devel­oping new mate­rials that can with­stand the heat. But Taslim’s approach is dif­ferent. Instead of new mate­rials, he’s been exploring new designs–designs that redi­rect a little bit of the cool air bled from the com­pressor through the blade body. His team develops intri­cate pat­terns that increase sur­face area while dimin­ishing both the com­plexity of the design and also the amount of cool air able to do the job.

You want to design the best cooling pas­sage inside the air­foil in order to use the least amount of air for the same amount of cooling,” he explained. That’s because any air directed away from the com­bus­tion chamber equals a reduc­tion in the engine’s overall efficiency.

Of all the flights I’ve been on in my life, I never once con­sid­ered the air­foil. Research like this always gets my engines going (sorry, I couldn’t help myself), because it points out just how much world there is hidden under­neath the world we know and are familiar with. We like to think that it’s the big prob­lems, the over­ar­ching chal­lenges, that need our undi­vided atten­tion. But if we’re going to talk about sus­tain­ability, we need to talk about air travel (in terms of fuel, money, mate­rials, etc). And if we want to talk about air travel, it turns out we’ve got to talk about air­foils, along with all the other bits and pieces that go into making a whole.