Abstract: Apparatus for imparting a spiral spin on a fluid in zone 2 surrounding a columnar substance in zone 1 which may be a metal electrode or a fluid, such as gas for welding. The spirally spinning fluid may be an inert gas for sheathing zone 1 down to the welding site on a workpiece. For a four-stroke-cycle internal combustion engine, exhaust gas return (EGR) in zone 1 is sheathed from a fuel-air mixture in zone 3 by the spirally spinning fluid (fresh air) in zone 2. In a two-stroke-cycle engine, the spirally spinning fluid in zone 2 may be injected gas while the EGR is injected in zone 1. Fresh air, precharged in the cylinder at the end of the power stroke, constitutes zone 3.