L. Allocca, A. De Vita, and L. Angelo (Italy)
GDI spray, CFD computation, spray model.
Numerical calculations and experimental analyses of hollow cone sprays, generated by pressure-swirl injectors for Direct Injection Spark Ignition (DISI) engines, have been performed. 3D computations are based on the KIVA 3V code in which basic spray sub models have been modified. Atomization has been simulated by injection of blobs having dimensions equal to the thickness of the liquid sheet at the exit of the nozzle. The parcels are considered to break when the traveling distance becomes greater than the sheet break up length. Break up of blobs has been simulated using the Taylor Break Analogy (TAB) model as modified by Han et al [1] and the break up length has been calculated from a semi-empirical correlation based on the wave instability due to Drombrosky and Hooper [2], with modifications introduced by Han and Reitz [3]. Spray characteristics have been measured using a system, able to gather and to process spray images, including a CCD camera, a frame grabber and a pulsed sheet obtained by the second harmonic of Nd-YAG laser (wavelength 532 nm, width 12 ns, thickness 100 µm). A digital image processing software has been used to analyze the collected pictures [4]. The present paper reports some results of an in progress work aiming to select and to validate proper models for the various phases of spray development. The final goal of the research activity is to setup the KIVA 3V code for its extensive use in the design and the development of DISI engines.
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