OPTIMIZATION OF BREAKUP MODEL USING LES OF DIESEL SPRAY

In this study, an application of an original combined spray breakup model is proposed to simulate the transmit diesel spray feature by use of large eddy simulation (LES) analysis. The spray model is combined with the Kelvin-Helmholtz (KH) and Rayleigh-Taylor (RT) model (i.e., the KHRT model), which is a combination of the surface wave instability (WAVE) model, RT model, and modified Taylor analogy breakup (MTAB) model. Here, the spatial heterogeneous structure inside the spray is focused to assess the dispersion and mixing processes by applying an accurate spray breakup model. It is well known that the KHRT model can properly estimate the spray shape by underestimating the Sauter mean diameter (SMD) of the droplet within the spray, while the MTAB model can predict the SMD adequately by overestimating the parcel diffusion at the upper stream region of the spray. The KHRT model is based on the breakup regime of a higher droplet Weber number. The MTAB model is based on the breakup regime of a comparatively lower Weber number. In diesel sprays, high Weber number droplets can be observed at the upper spray region and low Weber number droplets can be observed downstream from the spray due to the momentum exchange between the liquid and gas phases. In this study, a breakup model was developed in order to improve the prediction accuracy of non-evaporating diesel spray. For analysis of the primary breakup regime, the WAVE model is employed in the higher droplet Weber number region and for the secondary breakup, the MTAB model is introduced into the lower Weber number region. This model is applied at different fuel injection pressures in order to validate the WAVE-MTAB model. As a result, the effect of the fuel injection pressure was successfully predicted by this WAVE-MTAB model.