Effects of turbulence intensity and n-pentanol concentration on droplet evaporation and auto-ignition

Abstract

Evaporation and auto-ignition characteristics of an n-pentanol-diesel droplet are investigated under a high-temperature (900 K) and turbulent environment. Turbulence intensity and n-pentanol mass fraction are varied between 0 and 0.527 m/s and 0–50%, respectively. Droplet evaporation is controlled by the gas temperature, which is affected by turbulent transport and chemical reactions. Diesel vapor accumulates around the droplet at all turbulence intensities, whereas strong turbulence facilitates the transport of n-pentanol vapor to far areas. Turbulence intensity has little impact on the droplet temperature and evaporation rate of pure diesel. The addition of n-pentanol reduces both the evaporation rate and droplet temperature at a high turbulence intensity of 0.527 m/s, but it has little influence on droplet temperature in a static environment. The vapor distribution determines the chemical activity of gas phase around the droplet, and consequently the auto-ignition characteristics. With the increase of n-pentanol concentration, the auto-ignition delay firstly decreases and then increases under low turbulence intensities (0–0.264 m/s), while it monotonicallyincreases under a high turbulence intensity (0.395 and 0.527 m/s). The auto-ignition delay firstly decreases and then increases with the increase of turbulence intensity, regardless of n-pentanol concentration.