Abstracts

Structured laser illumination planar imaging(SLIPI) is a technique capable of suppressing multiple lightscattering effects in optically dense sprays, resulting in sprayimages without blurs and with enhanced contrast. The novelty of thework presented in this thesis concerns the applications of avariety of SLIPI-based techniques for the measurement of dropletsize, droplet concentration, and liquid temperature in atomizingsprays. Two types of spray systems are investigated here: 1) Steadyhollow-cone water sprays using temporally averaged imaging. 2)Transient Direct-Injection spark ignition (DISI) biofuel spraysusing instantaneous imaging. The temporally averaged measurementsare performed using three-phase SLIPI (3p-SLIPI) with liquidinjection pressures in the range of 2050 bar and at ambientconditions. Droplet sizing is obtained by combining SLIPI with thelaser-induced fluorescence (LIF)/Mie ratio approach, where thedroplet Sauter mean diameter is deduced after calibration withphase Doppler anemometry measurements. The droplet concentrationand liquid volume fraction are obtained by combining theSLIPI-LIF/Mie method with light transmission measurements. This isperformed using a laser sheet scanning approach, which providesthree-dimensional quantitative reconstructions. Finally, the spraytemperature is obtained by combining SLIPI with two-color LIF ratiothermometry for a liquid temperature ranging from 2555C. It isfound that multiple light scattering induces measurement errorseven for sprays having singly scattered photons in majority. Thisfinding, therefore, strongly supports the application of SLIPI forquantitative spray measurements, even for optically dilute sprays.The 3p-SLIPI approach is based on recording a minimum of threemodulated sub-images successively, each having a different spatialphase; therefore, it has been primarily used for temporallyaveraged imaging. To circumvent this limitation, two novelinstantaneous imaging approaches, 2p-SLIPI and 1p-SLIPI(corresponding to two-phase and one-phase, respectively), have beendeveloped. In the 2p-SLIPI optical setup, the lines structure isoptically shifted by exploiting the birefringence property of acalcite crystal. This novel optical approach is used to image spraydynamics in ethanol and butanol DISI sprays at liquid fuelinjection pressures of 80 and 160 bar, where the spray chamber isoperated at 2-bar air pressure. Finally, the results frominstantaneous 2p-SLIPI and 1p-SLIPI imaging have been compared,showing promising applications for the study of spraydynamics.