Comment by bob1029
8 hours ago
> To further improve fuel efficiency and output, ZR15DDTe engine uses Nissan's unique STARC*2 concept paired with a large turbocharger.
If we are able to consider fixed RPM operation and are willing to endure turbomachinery, I don't know why we wouldn't just go all in on a gas turbine. You can reduce the number of moving parts dramatically and accept a much wider range of fuels.
Being able to engineer everything around a one fixed operating speed makes a huge engineering difference. Reciprocating engines are responsive to load and speed changes, but there are trade offs in many other categories.
You can also make a gas turbine power module quite small relative to the alternatives. Replacing the it at major service intervals could be made economically viable.
I suspect that the improvement in efficiency is small enough at the scale of an automotive power plant that it wouldn't be worth it.
Reading around suggests that in order to achieve decent efficiency from a gas turbine, you need quite a few supporting systems that only really make economic sense at larger scales (like the 10's of MW scales, not the 100's of kW).
(Although just from a fun technology angle I'd love to see a gas turbine in a car).
The trick in this scenario is the fact that you can run it at a constant RPM + load for a reasonably long duration. The cost of warming up a recuperator and other masses is amortized across a dependable schedule each time. The controller can ensure that the turbine (assuming the drive is long enough) will run for a minimum duration given a certain battery charge level.
The reason this stuff didn't work before is because we couldn't run the turbine this way. Now we have viable energy storage technology and can make some of the most difficult variables into constants.
Chrysler built one in the 60s: https://en.wikipedia.org/wiki/Chrysler_Turbine_Car
afaik microturbines are less efficient, louder and hotter than piston engines.
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That would be very cool. I wonder if you could get it through legislation though. I think all the legislation is based around reciprocating IC engines.
This has been tried, but back in the day the automatic transmissions weren't really up to it, and they don't really like thermal cycling. And they're noisy. Exact opposite of modern stop/start petrol engines for urban driving.
I also suspect all attempts to keep doing combustion engines for mainstream driving are going to get gradually overtaken and lapped by BEVs.
It was tried in the 60s and 70s, most seriously by Chrysler, and the emissions and drivability weren't great because it was in the "we need to get it working good before we go back and mop up all the other stuff" phase or R&D. The fuel crisis plus the state of automatic transmissions at the tie kept it a back burner item so development was slow and not a priority nor did other OEMs invest seriously.
Chrysler flamboyantly gave this back burner project up and promised to halt further development as part of the wrangling around the government loan they got to save them from bankruptcy in 1979.
Basically it was a song and dance to win political points among the same generation of absolute genius environmentalist who thought moving a steel mill from Ohio where you can regulated it to China where you can't is a win.
I suspect that had the project died a natural death in the 80s rather than being publicly executed as a warning we likely would see some trickle of development these days since they see like a nice natural pairing for various sorts of EVs and CVT powertrains.
It's also worth noting the degree to which facilities and talent pool overlapped between Chrysler, Chrysler Defense, how much more porous the corporate world was 50yr ago and that that Chrysler did ultimately get someone else's turbine into a running driving mass production vehicles in the form of the M1 Abrams so it's not like the technology is unsuitable on a fundamental level.
Think if it like this - is the turbine exhaust hot? Then you are losing energy.
You can extract more energy by adding stages but that increases weight.
While a small and light weight diesel engine is already very close to the theoretical limit.
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> why we wouldn't just go all in on a gas turbine
Cost, reliability.
Gas turbines are not very fuel efficient.
Yeah but I suppose you'd only use them if your hybrid ran out of battery power.
You might as well just use a small regular petrol/diesel engine.
The argument about fewer moving parts is often made. But generally turbines are more expensive to make. They require precision engineering. Whereas regular engines (if you've ever worked on one) don't require that nearly as much.
I appreciate this if it's for turbochargers, but turbines share many similarities with them.
https://www.youtube.com/watch?v=-bZu8atQ8lY
BTW, Garett builds/rebuilds turbochargers in many vehicles. If you have a vehicle with a turbo, see if it says 'Garett' on the side.
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