ID 113

LIF/Mie planar droplet sizing in IC engine sprays using single-droplet calibration data

 

Abstract:

This paper presents an improved method for planar measurement of the droplet size distribution of sprays, which is applied to an ethanol multi-jet DISI (direct-injection spark-ignition) spray studied in an injection chamber. The method is based on simultaneous detection of Mie-scattering and liquid Laser-Induced Fluorescence (LIF) using two sCMOS-cameras. Two-phase SLIPI (Structured Laser Illumination Planar Imaging) is applied for both techniques for suppression of multiple light scattering. As fluorescent tracer, the organic luminescence dye Eosin-Y is added to the liquid fuel, which is excited at 532 nm using a Nd:YAG laser. From the instantaneous LIF/Mie ratio images, quantitative planar measurements of the droplet Sauter Mean Diameter (SMD) are conducted using calibration data from single spherical droplets. For this purpose, a droplet generator was employed, which produces a droplet chain with a wide range of droplet sizes relevant for DISI-sprays. A high-resolution microscopic setup was used for calibration of the LIF/Mie ratio as a function of SMD. Effects of liquid fuel temperature, laser power and dye concentration on the LIF/Mie ratio are studied in detail. The calibration data is used to quantify the droplet size distribution of the DISI spray, which was studied for an injection pressure of 8 MPa and ambient conditions of 0.2 MPa and 298K. The spray evolution and structure were analyzed in various planes in terms of SMD. From these measurements, a complete 3-dimensional spray data set has been generated.