Inside the PDE Lab
Hi Everyone…
The past few weeks have been a blast… literally!! I am smack in the middle of some exciting, ground-shaking experiments testing a new kind of airplane engine called a Pulsed Detonation Engine (PDE). These aren’t just any experiments, they happen to be the first of their kind in the world. I’ll tell you more about them, but first… let me tell you some more about PDEs.
As the name implies, a PDE uses “detonations” to burn the fuel in a more explosive and more efficient manner compared to your usual steady deflagration flame. A deflagration is the normal way to burn fuel… you see it everywhere… a fireplace, a candle burning, inside an internal combustion engine, and inside today’s aircraft engines. It’s also what powers the world in today’s large megawatt scale gas turbine based powerplants. A detonation, on the other hand, looks nothing like a deflagration. A detonation is a shock wave travelling at Mach 5 (5 times the speed of sound!!) that ignites the fuel-air mixture as it passes. The combustion products are at higher pressure (this is a key difference from a deflagration) and that translates into a more efficient conversion of the chemical energy stored in the fuel into useful work.
The reason why I am so excited about PDE’s is that we can potentially reduce the amount of fuel burned by a whopping 5%!! That might not sound like much, but in the aircraft propulsion world a 1% improvement translates into hundreds of millions of dollars of savings per year!! Considering that present day deflagration-based gas turbine engines have already been highly optimized over the past 50 years (a 0.2% improvement is considered a major breakthrough)… PDE’s represent a possible game-changing technology that could revolutionize aerospace propulsion. Equally important, by reducing the amount of fuel burned, PDE’s also reduce the amount of emissions and greenhouse gases that get put up in the atmosphere… it’s good for the environment too!
So… back to my experiments… what exactly am I doing? Well, we’ve designed and built an eight-combustor version of a PDE and integrated it with a turbine… the first steps to understanding how to integrate a PDE in a real gas turbine engine. I’ve been leading this collaborative effort with NASA for the past two years and we’re in our final phases of the program. Now, this particular laboratory experimental engine will not be flying anytime soon, but we’ve gathered some unique data that has increased our understanding and has moved us one step closer.
Well… I’d better go… time to get back to my experiments… there’s nothing like the sound of the turbine spooling up as the PDE’s fire. I’ll see if I can find some video of an experiment, then you’ll see why this is so much fun!
Don’t get so carried away having fun that you lose sight of an important detail. Increasing efficiency in this case implies higher peak combustion temperature, which inevitably means formation of more NOx. Aircraft burn a lot of fuel. Do you have any concerns about developing an engine which adds to acid rain?