A comparative study on methanol and n-dodecane spray flames using Large-Eddy Simulation

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Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2024-02
Major/Subject
Mcode
Degree programme
Language
en
Pages
17
Series
Combustion and Flame, Volume 260
Abstract
Methanol (CH3OH) is an attractive alternative fuel that can reduce net carbon release and decrease pollutant emissions. In this study, methanol and n-dodecane spray flames were investigated using Large-Eddy Simulation (LES) and direct coupling with finite-rate chemistry. The selected ambient conditions are relevant to engines and were previously unreported for numerical methanol spray studies, i.e. high pressure (60 bar) and temperature (900 – 1200 K) with high injection pressure (1500 bar). The Engine Combustion Network (ECN) Spray A case was used to validate the n-dodecane spray flame. For methanol, a modified ECN Spray A condition was used with a high initial ambient temperature (1100 K-1200 K) to ensure fast enough ignition relevant to engine time scales. The performed homogeneous reactor (0D) simulations revealed a new phenomenon of a two-stage ignition process for methanol, confirmed by the 3D LES at high pressure, high temperature, and lean conditions. The present numerical results also show that: 1) there is a strong ambient temperature sensitivity for methanol ignition delay time (IDT) with a five-fold decrease in IDT (IDT1100K/IDT1200K=5) and a factor of 2.6 decrease in the flame lift-off length (FLOL1100K/FLOL1200K=2.6) as the ambient temperature is increased from 1100 K to 1200 K, 2) methanol spray ignition takes place at a very lean mixture (ϕMR≈0.2) consistent with the 0D predicted most reactive mixture fraction (ZMR), 3) on average, methanol sprays are significantly leaner than n-dodecane sprays at quasi-steady-state (ϕmeoh,ave≈0.2 vs ϕndod,ave≈0.7), implying very low soot emissions, and 4) the methanol spray flames could have similar temperatures as the n-dodecane sprays depending on the initial conditions, thus a similar level of NOx emissions.
Description
Funding Information: The first author acknowledges financial support from the Henry Ford Trust (grant numbers 20220058 and 20230071). This study is also financially supported by the Academy of Finland (grant number 332835 ) and Aalto University. The authors acknowledge the computational resources provided by the Aalto Science-IT project and Aalto Research Software Engineers (RSEs). Funding Information: The first author acknowledges financial support from the Henry Ford Trust (grant numbers 20220058 and 20230071). This study is also financially supported by the Academy of Finland (grant number 332835) and Aalto University. The authors acknowledge the computational resources provided by the Aalto Science-IT project and Aalto Research Software Engineers (RSEs). Publisher Copyright: © 2023 The Author(s)
Keywords
0D, 3D, Chemistry, combustion, LES, methanol, n-dodecane, spray
Other note
Citation
Kaario, O T, Karimkashi, S, Bhattacharya, A, Vuorinen, V, Larmi, M & Bai, X S 2024, ' A comparative study on methanol and n-dodecane spray flames using Large-Eddy Simulation ', Combustion and Flame, vol. 260, 113277 . https://doi.org/10.1016/j.combustflame.2023.113277