The impact of spherical, flake, and fiber microparticle addition on frictional pressure loss in turbulent gas flows was experimentally investigated. Pressures up to 6.6 MPa (955 psig) were studied. Drag reduction (i.e., reduced frictional pressure loss) was clearly observed only at high dosages of >0.01 gsolid/cm3gas,actual. A "lubrication" effect though was evident at lower dosages where relatively minor drag increases occurred despite significant solid loadings. No trends in drag reduction were observed based on Reynolds number or pressure. Larger particles tended to increase frictional losses, especially at moderate dosages.

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