Little blade, big role
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.