No abstract

A comparative experimental and numerical study is conducted to establish the significance of the use of single-component over multi-component representatives of biodiesel, diesel and their blend for predicting spray tip penetration. Methyl oleate and methyl laurate are used as single-component representative fuels for biodiesel. The pure components n-heptane, n-dodecane and n-tetradecane are used as single-component representative fuels for diesel. Methyl laurate is found to represent biodiesel of coconut, whereas methyl oleate is found to represent biodiesel having high percentage of long-chain fatty acid esters. The spray tip penetration of methyl oleate is found to be in good agreement with the measured spray tip penetration of karanja biodiesel. The spray tip penetration prediction of n-heptane fuel is closely following diesel spray tip penetration along with that of n-tetradecane and n-dodecane. The study suggests that the knowledge of the single-component representatives of biodiesel, diesel and their blend is sufficient to predict the spray tip penetration of the corresponding biodiesel, diesel and their blend under non-evaporating environment.

This paper compares the evaporating spray characteristics of biodiesel and biofuel pure component spray at engine-relevant conditions such as late-cycle postinjection and near top-dead-center injection conditions. The spray characteristics, liquid length, vapor length, and spray vapor area are predicted using an OpenFOAM CFD code. The liquid length of methyl oleate is observed to be longer under late-cycle postinjection conditions, which may lead to the impingement of liquid fuel on the combustion-chamber walls. The liquid length for methyl laurate is shorter than that of methyl oleate at high ambient temperature and density conditions. The vapor length at top-dead-center conditions for all of the biodiesel pure components is similar. The liquid length and vapor length of the straight vegetable oil pure components, triolein and trilaurin, is longer than those of their corresponding biodiesels. The liquid length, vapor length, and spray vapor area for methyl laurate are similar to those of dodecane. The liquid length of all of the pure components is found to be related to the specific energy ratio and boiling temperature of the fuel.

The vapor mass fraction distribution of the multicomponent surrogate of diesel and biodiesel fuel is studied using multicomponent evaporation model at engine-relevant conditions. The numerical model is validated with experimental liquid tip penetration and vapor penetration for diesel and biodiesel. The vapor distribution for a multicomponent surrogate is significantly different than that of single-component fuel. The tetradecane, single-component surrogate for diesel has different vapor mass distribution unlike in multicomponent diesel fuel. The spatial mass fraction distribution profile of biodiesel is found to be the function of volatility differential of the pure components and their proportion in the composition. The vapor mass fraction distribution for biodiesel of palm and soybean is found to be similar to that of their single-component surrogate due to comparable volatility of components of these biodiesels. However, methyl laurate in coconut biodiesel has volatility differential with other components and also has a significant share of 40% to 50% in the coconut biodiesel composition. The change in percentage of methyl laurate in coconut composition is found to have strong impact on vapor distribution. The vapor mass fraction distribution is observed to be affected by the change in the biodiesel composition specifically volatile component.