PIV snapshot of the flow field within a swirl flame. The streamline plot shows the vortical structures in the shear layers of the flow field.
Particle image velocimetry (PIV) is the preferred measurement technique for 2D measurement of all three velocity components in turbulent flames. By means of light scattering from small metal oxide particles added to the flow, the path covered by particles and hence the flow velocity is determined by double-pulse illumination. Both mean values and fluctuations in flow velocity can be determined, and turbulent structures can be visualised. In addition to tests on laboratory flames, this technique is also used to characterise combustion processes under real conditions in gas turbines.