IC Engine Turbo Fan Turbo

Hi all
OK so I am trying to design a relatively small Turbo Fan Jet engine as an edition to an IC engine. The air that would normally be blown by the big fan in a turbo jet will actually be used to power the IC engine. Also I thought why not use the exhaust of the IC as the Heat source for the jet. I presume that it will still need some fuel injected, especially under acceleration.

Ok so I have an idea in my head of how all this will work. So now I want to crunch some numbers. I want to use this on a 12liter IC engine (yes 12). By my reckoning that means it will need something like 180000LPM of air or around 6800CFM. OK so how big a fan will I need I asked, 'I know a Google search will answer me'. Sadly not I cannot seem to find any useful information…

So if anyone can see my idea working could you guys here give me an idea on fan size, speed and if there are any similarly sized units you have built or commercially available?

Thnx Rufe0