A new experimental technique for the simultaneous determination of single droplets size, velocity and optical properties inside an evaporating hydrocarbons spray

A new experimental technique for the determination of the size, velocity and/or the optical properties of single droplets is proposed. It is based on the different behaviour of scattering cross sections upon the size for vertically and horizontally polarized incident light, as it is predicted by the Lorenz-Mie theory. Measurements of the scattering polarization ratio y = CHH/CVV in the side scattering region can be employed for sizing transparent droplets while the optical depth kD can be obtained in the forward region for absorbing droplets. An interpherometric apparatus has been realized for the simultaneous determination of the polarization ratio and velocity of individual droplets. Experimental results obtained on arrays of monodisperse and bidisperse droplets with different refractive index illustrate the potentiality of the method.