Steam powered turbine?
wouldn't that be ridiculously inefficient at such a small scale? You'd also need a way of storing the superheated steam to run the thing- under a great deal of compression- or a boiler.

Also, a steam turbine would spool up and down fairly quickly if you restricted the steam going through it at source / exhaust.

You could look into acetylene or Ammonia fuelled Stirling engines.

As a sidenote, I've often thought of creating the best engine ever for some of my favourite bands. It'd use limestone & from coal to create Acetylene. Then run the engine from that. So you'd have a vehicle that ran on ROCK itself.
( uberdeity Wondered why Owen Lars knew of the term "hell" on, Wed 5 Nov 2008, 13:26, Reply)