Re: Re: Re: Heard on Car Talk (popular Public Radio Show)
Ooops. Edit induced error needs correcting on my previous post. Plus a fe additional points.
The Roots / Tilling Stevens engine used as a basis for Professor Timoneys work uses rocking levers to transmit the motion of the opposed pistons to the single crankshaft mounted centrally below the cylinders. Its the shafts carrying the rocking levers which are mounted in eccentrics not the crankshaft as stated.
A disadvantage of this configuration is that it needs two connecting rods per piston and the rocking levers so there much more mechanical inertia than with a conventional engine. I guess that modern design and materials could reduce this problem but, inevitably, the maximum rate of rpm change will be less than with a conventional engine. Whether that is actually important under load is another matter especially as the power output changes needed for acceleration can be as much due to shifting the operating point of the engine, which is a fast process, as due to rpm changes as with a conventional motor. Proper exploitation of this characteristic is difficult with conventional transmissions.
This engine was a two stroke, externally blown, uniflow diesel but there is no reason why the configuration couldn't be used in a petrol motor whether two or four stroke. Given the detonation suppressing properties of water injection it could probably be operated at a higher compression ratio than a conventional petrol motor too.
The main interest in water injection or FWE (Fuel water emulsions) is for heavy fuel oils which need to be heated to help with atomisation. The water flashes to steam and provides better atomisation and combustion with reduced pollution.
One of the main benefits is the reduction of NOX which is reduced due to the cooler temperatures during combustion. (as I understand it)