Quote:
Originally Posted by elhigh
Boy, I remember those articles. Pop Sci did a big piece on Yunick's engine - he called it the Adiabatic Stage II, and he projected development that would necessitate Stages III and IV - and they asked the same questions my dad and I did: how the hell does he get it to run reliably without melting?
My dad even had this to say: "You don't usually see temperatures like this without it being a jet engine." Dad's not an engineer, he's a psychologist. But he reads a lot, and I read a lot of what he did. He was right. And now of course we see jet engines that run even hotter, and they use exotic monocrystal turbine blades, ceramic parts, etc. They're damned expensive but screwed into machines that generate millions and millions of dollars over tens of thousands of hours of runtime so the cost is justified. If we could bring the per-piece costs down, we could have some of those esoteric parts in our cars.
Smokey described his vision of the Stage IV as not even needing a radiator. That captivated me more than anything else he said in the entire article. If we could stop throwing heat away, we could use it productively instead.
Then I remember the other side of the coin, the old Shell Mileage competitions. They usually looked like velomobiles with engines in them, and they would mosey along at a brisk jogging pace, and the engine would fire every thirty feet or so. Often the engine was tightly wrapped in insulation to keep from throwing heat away. "A-ha!" I thought. Heat conservation again.
But NOx production becomes a thing above certain temperatures. Dang it.
Nice little blast from the past. I'm pretty sure that raising internal temperatures is a big, wide open door to increased economy but there are tradeoffs. I'm not familiar enough with the chemistry of internal combustion to say what happens, but is there something we could do to minimize NOx production? A sort of gasoline oriented DEF, for instance?
Sorry, I'm probably opening myself to flaming for that. I don't even own a diesel and I hate DEF-dependent engines just on general principle.
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People mistakenly think that at 2300 deg C you automatically see a large production of NOx. However, another condition to the formation of NOx is time - if the combustion and pressure are held for only a short period, the "lazy" rate of formation of NOx means it can be minimized.
This is how HCCI engines can have low NOx output even with high combustion temperatures. The rate of combustion is so high and the pressure fall off ( RPM ) can be monitored that little NOx will be formed.