Numerical Simulation of Multicomponent Diesel Fuel Spray Surrogates Using Real-Fluid Thermodynamic Modelling

Computational models widely employed for predicting the dispersion of fuel sprays in combustion engines suffer from well-known drawbacks associated with the utilization of case-dependent empirical phase-change models, describing the conversion of liquid into vapour during fuel injection. The present work couples the compressible Navier-Stokes and energy conservation equations with a thermodynamic closure approximation covering pressures from 25 to 2000bar and temperatures that expand from compressed liquid, vapor-liquid equilibrium to trans/supercritical mixing, and thus, cover the whole range of P-T values that diesel fuel undergoes during its injection into combustion engines. The model assumes mechanical and thermal equilibrium between the liquid, vapour and surrounding air phases and thus, it avoids utilization of case-dependent empirical phase-change models for predicting in-nozzle cavitation and vaporization of fuels. Model development is based on the recent works reported for one mono-component (n-dodecane) and extended here to consider the influence of two multicomponent diesel surrogates. Fuel properties are predicted via the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state (EoS). The tabulated thermodynamic approach proposed is based on P-T tables, providing very high accuracy across the range of conditions with only a small number of interpolation points. The developed model is validated against experimental data for the liquid and vapour penetration for the Spray A conditions reported in the Engine Combustion Network (ECN) database. Results show good agreement for three non-reacting target conditions. Then, from simulations obtained using the two multi-component fuel surrogates their effect can be quantified on spray development.