Yes, the velocity of the air would inascere, no doubt about that!However, along with that velocity inascere comes a proportional decrease in the cross-sectional area (8 down to 1/2 ), and therefore the net result would be the same amount of work energy , minus the losses due to turbulence and friction in the process of narrowing down the air stream. But keep on trying you never know, you might hit on a great idea that will save the world!
