Green Car Congress -- rapidly becoming one of my favorite sites, and a daily must-read for anyone interested in energy technology, environmental technology, and/or cars -- tells us today about Fiat's plan to introduce a "four fuel" vehicle into the Brazilian market. The car will be designed to run on gasoline, diesel, ethanol, and natural gas. This will be a challenging develoment, but not without its rewards:
Delivering a single-fuel HCCI [Homogenous Charge Compression Ignition -- explained here] platform will be challenging enough on the engine management side. Adding in the capability to switch fuels will require much additional software intelligence and control over the engine and emissions mechanisms. If successful, though, the result would be greater fuel-efficiency and emissions control.
If oil continues its price climb, expect to see more of these sorts of announcements, particularly for vehicles in parts of the world not so tightly wedded to an existing gasoline infrastructure. While there are plenty of potential candidates, there isn't a single obvious replacement for the gasoline-powered internal combustion engine in current use. Over the next decade, we'll see a lot more experimentation and multi-fuel systems (including "plug-in" hybrids) as nations and corporations try to figure out what will provide the best combination of low cost, low emissions, and low disruption.
Interesting. One problem with extremely lean mixtures like in HCCI is that they can lead to excessive cylinder head temperature. You can literally burn up an engine by running it too lean; this occasionally happens in aviation piston engines, for example.
I need to read up on it, but on the surface it is quite confusing to me. A diesel engine requires upwards of a 20:1 compression ratio...at which gasoline won't work at all. Gasoline engines are down in the 8:1 to 10:1 range...at which diesel fuel won't work at all. So unless they have found a way to double the compression ratio on the fly (which to my mind would mean halving the displacement of the combustion chamber, no?) then I'm confused. I'm just not clear on how you could auto-ignite diesel any lower, or get any useful power out of gasoline's auto-ignition. But I'm all ears!
Stratified charge engines have been around for a a while now. Eaton Corp. has developed them for military applications.
You only need 9.5:1 or greater compressio. The trick is the custom piston have cavities (micro chambers) EDM'ed into the tops of them. They contain free radical combustion particles (drawn in and out due to pressure differences) which help to initiate combustion (slowly) prior to the engines developing full compression. Very interesting technology, allows one engine to run all sorts of fuel.
The military was developing it to allow normal gasoline engines to run on heavy fuels such as J2 (jet fuel), Bunker crude, deisel, kerosene, etc. Hoping that the single fuel would allow them to simplify logistics.