Numerical Simulation of Diesel Spray Evaporation in a “Stabilized Cool Flame” Reactor: A Comparative Study

Abstract

The major objective of this work is to numerically investigate the interacting physical and chemical phenomena that characterize the flow in a stabilized cool flame diesel fuel spray evaporation system. A two-phase RANS computational fluid dynamics code has been developed and used to predict the characteristics of the developing turbulent, multiphase, multi-component, reactive flow-field. The code employs a Eulerian-Lagrangian approach, taking into account the mass, momentum, thermal and turbulent energy exchange between the phases. A variety of physical phenomena, such as turbulent dispersion, droplet evaporation, droplet-wall collision, conjugate heat transfer, drift correction, two-way coupling are taken into account by implementing respective sub-models. Two alternative modelling approaches for the simulation of cool flame reactions have been validated and evaluated by comparing numerical predictions with experimental data from two atmospheric pressure, evaporating Diesel spray, Stabilized Cool Flame reactors. Both models have achieved good quantitative agreement in the majority of the considered test cases. The results have been used to estimate the local physical and chemical characteristic time scales of the occurring phenomena, thus allowing, for the first time, the classification of stabilized cool flames.

Milestone Report #2: Direct Evaporator Leak and Flammability Analysis Modifications and Optimization of the Organic Rankine Cycle to Improve the Recovery of Waste Heat

“…The relatively large heat losses caused by turbulence in the other regions of the flow field tend to increase the autoignition delay time, since the rate of heat production by the chemical reaction is slower than the rate of heat loss. When heat losses at the system boundaries are completely balanced by heat generation resulting from the exothermal chemical reactions, such steady-state thermochemical conditions do not result in autoignition (Kolaitis and Founti, 2009).…”

A 3D CFD Modelling Study of a Diesel Oil Evaporation Device Operating in the Stabilized Cool Flame Regime

“…It is evident that, contrary to "conventional" non-premixed combustion technical devices, where chemical reactions occur mainly in a distinct "thin" flame zone, cool flame reactivity zones are "thick" and cover a significant part of the device's volume. In this context, numerical simulations, presented in a recent publication [32] attempting to classify SCF on the basis of characteristic time scales, revealed that the developing thermo-chemical conditions exhibit mainly characteristics of the "distributed reaction zones" regime.…”

“…Aiming to validate the developed computational approach, predictions are compared with available temperature measurements (c.f. Figure 1), obtained in the SCF reactor [32], for the three considered Test Cases. In Figure 11, temperature predictions along the reactor's symmetry axis are compared with the experimental data.…”

Features of Liquid Gas Spraying Process Simulation for Internal Combustion Engine

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