This investigation implies that typical high performance cyclone designs are inhibited in two significant areas. With small inlets and small outlets, it appears that large scale turbulence inhibits collection. The use of a large inlet contracting the flow into a relatively narrow annular region minimizes the production of large scale turbulence. Similarly, increased engagement length improves the length-to-annulus width and suppresses the turbulence that is formed. It is postulated that inlet vanes or baffling might play a similar role. The use of air shielding is found to be an alternative means of performance improvement and is of special interest in systems that can use clean dilution gas, e.g., cyclone combustors.