3-component-Doppler-laser-2-focus: a new kind of three component velocimeter

The conventional Laser-Two-Focus (L2F) method measures the two components of the flow vector in the plane normal to the optical axis by measuring the time of flight of particles crossing the two laser beams in the probe volume. Recently a new three component system was developed, named 3D-Doppler-L2F, which operates with the same confocal optical set-up as the two component L2F system, thus enabling three component measurements even under difficult conditions, for example in centrifugal compressors. The technique combines the L2F with the technique of the Doppler Global Velocimeter. The set-up of a 3D-Doppler-L2F, especially designed for 3D-velocity measurements in a turbine is presented as well as measurement results from a free jet.