Prediction method for ignition delay time of liquid spray combustion in constant volume chamber

Abstract

A prediction method, known as the Coupled Time Scale (CTS) method, is proposed in the current work to estimate the ignition delay time (IDT) of liquid spray combustion by only performing an inert spray simulation and a zero-dimensional (0-D) homogeneous reactor (HR) simulation. The method is built upon the assumption that if the majority of the vapor regions in a spray has a composition close to the most reactive mixture fraction, which can be obtained by performing 0-D HR calculations, these regions will then have a high probability to undergo high-temperature ignition in the spray. The proposed method is applied to estimate the high-temperature IDT of n-dodecane sprays. Two nozzle diameters (Dnoz) of 90μm and 186μm which correspond to Spray A and Spray D in the Engine Combustion Network [1] respectively, are considered. Both Dnoz are tested at three ambient temperatures (Tam) of 800 K, 900 K, and 1000 K. The fidelity of the proposed CTS method is verified by comparing the predicted IDT against CFD simulated IDT and measured IDT. Comparison of the estimated IDT from the CTS method to the measured IDT yields a maximum relative difference of 24%. Meanwhile, a maximum relative difference of 33% is found between the IDTs computed from the CTS method and the large eddy simulations of the associated reacting sprays across the different Tam,Dnoz, and chemical mechanisms considered in this study. © 2020 Elsevier