I was reading about a new serial hybrid that uses a micro-turbine, and that got me looking at automotive turbines of the past. We’ve come a long way, baby! One of the more interesting automotive turbine efforts was done by Chrysler. Turns out they started working on the issue in the 50s! In the mid 60s, they even made a fleet of 50 cars that they gave out to the public, with 203 drivers each getting a car for about three months. The program logged over 1.1 million miles!
So, what’s a gas turbine anyway? It basically is an engine based on fans. The fan on the front compresses air. A fuel is added and burned, and this larger volume of faster moving gas then turns a fan connected to the compressor. Things like cars and helicopters couple to the shaft, and things like airplanes use the exhaust thrust to push.
Why would one want to put a turbine into a car? There are a couple of reasons: The biggest is that the turbine is a much simpler engine than a piston engine. No valves, no camshafts, no reciprocating parts all mean that potential service issues would be much lower. The next big driver is that the torque curve of a turbine is a drag racers dream! Max torque at 0 RPM meant that you could accelerate quickly from a stand-still (and that’s always fun!) But there are some challenges as well. Materials have to be compatible with much higher temperatures, and the exhaust gas is really, really hot.
Now, the Chrysler program wasn’t the first automotive application of turbines, but it was the largest, and the only one to offer cars in volume to the public. Chrysler also solved both technical hurdles (materials and exhaust temp) in ways that not only made the engine work in cars, but also increased fuel efficiency greatly.
The key technical development that Chrysler developed was a novel heat exchanger called a “regenerator”. This would capture the heat from the exhaust gas and used it to pre-heat the intake air. To piston heads this is a bit crazy, because hot intake air leads to a bunch of problems, all that reduce power. But in a gas turbine engine, the intake air has to be heated to a temperature where the fuel can burn. If the air is cold, this takes a bunch of energy and really drops the overall fuel efficiency of the turbine. So the regenerator killed two birds with one stone: Exhaust temps were dropped lower (in some cases) than piston engines, and fuel efficiency was increased above equivalent piston engines. Pretty cool, huh?
So, if all this was so good, why did the automotive turbine fail in the market? There were really two reasons why, one technical, and one economic. The technical one was the delay between driver demand and full power. In the first version of the Chrysler turbine, it took about 7 seconds to go from idle to full power generation. Later on in the program, this was reduced to a bit over 1 second, but it was still the one of the largest complaints returned by the public comments. I think with modern engine management and some technical innovations (remember, this was over 40 years go), sub-second responses would be more than possible.
What’s interesting to me is that the economic constraints within Chrysler that helped kill the effort had to do with improving the piston engine! In the late 60s (yes, even before the catalytic converter), there was as drive to start cleaning up tail pipe emissions. This took engineering people and budget in corporate R&D and re-directed from the turbine efforts over to the piston efforts. But despite this, Chrysler turbine efforts continued and a lower level into the late 70s/early 80s, but none of these cars made it into public hands. But whatever the reasons, the program stalled and went the way of the Dodo. If you want to know more about the program, check out this excellent site: http://www.turbinecar.com/turbine.html
So much for Chrysler. What about today?
Well, the thing that triggered my interest in this is a start-up company called Velossithat is bringing together some serious players to make the next generation of serial hybrids. They have two cars in the pipeline: one is a supercar powered by a 770- HP A/C induction motor (a la Tesla to provide some splash). It’s targeted at 3 sec 0-60 and over 200 MPH top speed. While impressive indeed as a demonstration vehicle, what really got my interest was the SOLO.
The SOLO is a crossover that will be much less expensive. It will use a multi-fuel micro-turbine to charge the battery/super-capacitor combination electrical storage system. (BTW, using capacitors to boost short term acceleration allows for smaller, lighter battery packs without sacrificing peak power for some serious scoot.) Not only is the power system interesting, but Velozzi has partnered with Nanolegefor composite body panels as well as working with modern design and manufacturing to reduce structural complexity without sacrificing strength or rigidity.
According to Velozzi, “the SOLO will reach 100 MPG, 0 to 60 MPH in the 6 Sec and top speed of 130 MPH.” Not too shabby! Really, if the price point on this is good, one may sometime end up in my driveway (a guy can hope, can’t he?)
Other planned features include the ability to connect to home wiring or the grid (something A/C Propulsionhas offered in their electric car power-train systems, and bringing the promise of distributed generation a small step closer to reality.) This is worth a bit of comment on it’s own. One of the problems of lots of plug-in hybrids and electrics is peak grid load. While there is little problem at night when demand is low, if everyone plugged their car in while at work during the day, we’d have some serious problems. Cars like these, that can have give power to the grid, when coupled to smart infrastructure, offer the possibility of providing local load balancing and reduces grid strain. There’s a lot between the vision and the reality, but with stuff like this out there, it makes it more possible. Personally, I’d love it because I live in hills and suffer lots of power outages (see my “Blogging by firelight” post) and would love to just plug into the car for power when the lights go dark.
But one doesn’t really have to wait for turbine powered transportation. Turns out that there are some buses cruising around that are serial hybrids! A company called DesignLine Internationalis making buses (the ECOSaver IV, I have no clue about the first three!) in Charlotte, NC. While the buses aren’t cheap ($440k), each one gets about twice the gas mileage of conventional diesel buses and can save over 6000 gallons per year! They use turbines from Capstone Turbine Corp. What’s neat about these micro-turbines is that they use an air bearing to support the shaft. So no lubrication system is needed. If you don’t consider the drive-train, it’s practically a one moving part engine!
So, the automotive turbine is back, baby! Pretty soon, you’ll hear the whine of one near you….