This is a little off topic but its fun to play around with and I'd like as many opinions as possible.

I am a second year mech engineering student, one of our assignments is a design and build competition, the basic requirements are a vehicle to move toward a fan, using an impellor to drive one or more wheels. The judging will be based on both starting distance from the fan and time over the final 2.5 meters.

I have a few theoretical questions.

Is it better to have a high or low pitch on an impellor?

Is it better to have the impellor turning the same way as the fan or against it?

Can anyone give me suggestions, either scientific or from experience?

Matt