Numerical modelling of unsteady spray behaviour in moderately high-pressure regime

Abstract

The present study is mainly motivated to develop an unsteady computational code that simulates a transient behaviour of the spray injected into a moderately high-pressure environment. The moderately high-pressure regime is introduced to minimize some of the complexities that arise from considering the high pressure. In order to represent the spray development, the DDM (discrete droplet model), which is often identified as the PSIC (particle-source-in-cell) model, is employed among the SF (separate flow) models. Here, the Eulerian-Lagrangian formulation is used to analyse the two-phase interactions. For an accurate prediction of droplet evaporation rate in a high-pressure environment, a proper highpressure evaporation model is applied using thermodynamic and phase equilibrium conditions. Also, the effects of high pressure as well as high temperature are considered in the calculation of liquid and gas properties. Throughout the numerical simulation, a transient thermo-fluid mechanical behaviour of spray in a high-pressure environment is traced and visualized while its physical meaning is discussed in comparison with the case for normal pressure. Regarding the evaporation of spray, the effect of interactions between droplets is examined in comparison with the case for single droplet.

On the Rate of Heat Release for High-Boost, Low-Temperature Combustion Schemes: Accounting for Compressibility Effects

“…Real gas EOSs, however, have been used in a variety of other investigations relevant to combustion systems. Aggarwal and co-workers (e.g., Aggarwal et al, 2002;Yan & Aggarwal, 2006;Zhu & Aggarwal, 2000, 2002Zhu et al, 2001) as well as others (Hohmann & Renz, 2003;Kim & Sung, 2003;Wang & Baek, 2007) used cubic EOSs to predict isolated droplet evaporation times where non-ideality of the gas phase, especially in the region near the droplet surface, was taken into account. Three EOSs-Redlich-Kwong (RK), RKS, and Peng-Robinson (PR)-were employed.…”

Spray dynamics simulations for pulsatile injection at different ambient pressure and temperature conditions

“…The transfer of mass from the droplet to the gas phase is computed by determining the evaporative mass lost by the liquid droplets as they pass through a control volume. The vapour mass from droplet evaporation is represented in the gas-phase continuity equation as the volumetric source term (Sm) which is given as 26 where ΔV is the volume of the computational cell, m·d represents the evaporation rate of a typical droplet and n is the number of droplets within the cell. The abovementioned term appears as a source term in the species equation for the fuel vapour.…”

“…Here, Sh is the source term denoting the heat exchange to the droplet from the gas-phase which is given as 26 where Cpd is the droplet heat capacity, Hlat is the latent heat of the liquid, T∞ and Td are the gas phase and droplet temperatures, respectively.…”

“…The real gas effects are not considered, as the highest ambient pressure considered is less than 75% of the critical pressure of the liquid fuel. 26…”