fan

[sebastian]

I am making my first combustion cannon and I was looking for some pointers.

for example what is the purpose of a fan in the combustion chamber how far in do i put it and which direction should it blow?

[SEAKING9006]

Try here.

[starman]

The purpose of the fan is to vigorously mix the fuel air mixture before and during the shot and to assist ventilating spent gases after the shot. It makes a noticable difference in performance. The fan is typically mounted at the rear of the chamber and close to an air inlet. It sucks from that inlet and blows down the chamber and out the breech or barrel.

Use brushless fans only, typical of those used for computer case ventilation.

Here's a shot of the typical setup, breech view:


Outside rear view:


Also take a good long read at Latke's site...defacto standard resource for advanced combustion design.