MODELING SPRAY ATOMIZATION WITH THE KELVIN-HELMHOLTZ/RAYLEIGH-TAYLOR HYBRID MODEL

TLDR

Previous KH‑RT models applied Rayleigh‑Taylor breakup only to drops beyond the breakup length. The paper presents an improved spray atomization model for diesel and gasoline sprays. The model uses Kelvin‑Helmholtz instability for primary breakup of the liquid core, then models secondary breakup of drops with a combined Kelvin‑Helmholtz and Rayleigh‑Taylor approach, extending Rayleigh‑Taylor effects to all drops outside the core and employing a Rosin‑Rammler distribution for child drop sizes. The modified KH‑RT model yields satisfactory results, improves the temperature dependence of diesel spray penetration, and accurately predicts spray shape, penetration, and local SMD of hollow‑cone gasoline sprays comparable to TAB models.

Abstract

An improved spray atomization model is presented for use in both diesel and gasoline spray computations. The KH-RT hybrid atomization model consists of two distinct steps: primary and secondary breakup. The Kelvin-Helmholtz (KH) instability model was used to predict the primary breakup of the intact liquid core of a diesel jet. The secondary breakup of the individual drops was modeled with the Kelvin-Helmholtz model in conjunction with the Rayleigh-Taylor (RT) accelerative instability model. A modification was made to the KH-RT hybrid model that allowed the RT accelerative instabilities to affect all drops outside the intact liquid core of the jet. In previous implementations, only the drops beyond the breakup length are affected by RT breakup. Furthermore, a Rosin-Rammler distribution was used to specify the sizes of children drops after the RT breakup of a parent drop. The modifications made to the KH-RT hybrid model were found to give satisfactory results and to improve the temperature dependence of the liquid fuel penetration of the diesel sprays significantly. The KH-RT model was also found to predict the spray shape, penetration, and local SMD of hollow-cone sprays as well as previous gasoline spray models based on the TAB model.