Reduced Kinetic Mechanism for Methanol Combustion in Spark-Ignition Engines

Abstract

A reduced kinetic mechanism for methanol combustion at spark-ignition (SI) engine conditions is presented. The mechanism consists of 18 species and 55 irreversible reactions, small enough to be suitable for Large Eddy Simulations (LES). The mechanism was reduced and optimized using the comprehensive mechanism (AramcoMech 2.0) as a starting point, to maintain performance at stoichiometric conditions for the pressure (10-50 bar) and temperature ranges relevant for SIengine conditions. The mechanism was validated against experimental data for ignition delay at 1050 -1650 K, flow reactor at 783 K and jet-stirred reactors at 800-1150 K, and simulated validation targets for laminar burning velocity under conditions where no experimental data are available. The mechanism performs well for pollutant formation (CO and CH2O), ignition delay and laminar burning velocity, which are all important properties for LES of engines. Two other reduced mechanisms for methanol combustion, containing around the same number of species and reactions, were tested for comparison. The superior performance of the mechanism developed in the present work is likely a result of that it is specifically produced for the relevant conditions, while the other mechanisms were developed for a limited set of conditions compared to the present work. This highlights the importance of careful selection of reduced mechanisms for implementation in computational fluid dynamics simulations.

Skeletal chemical kinetic mechanism generation for methanol combustion and systematic analysis on the ignition characteristics

“…Besides the core 16 species, the skeletal mechanism by Pichler and Nilsson also contained CH 3 and CH 4 , whereas the Li et al mechanism contained CH 3 , CH 4 , and C 2 H 6 . The skeletal mechanism developed in this work includes CH 3 , CH 2 , and CH 2 (S) species instead of CH 4 and C 2 H 6 , in comparison with Pichler and Nilsson's and Li et al's mechanisms. However, further removal of any of the species would increase the maximum error of the predicted ignition delay times to more than 20% at temperatures above 1600 K. The CH 3 radical is included in Pichler and Nilsson's, Li et al's, and our skeletal mechanisms.…”

“…This mechanism was only validated against shock tube autoignition times and counterflow critical ignition conditions for methanol oxidation. The skeletal mechanism developed by Pichler and Nilsson was based on the AramcoMech 2.0 detailed mechanism, an earlier version of the AramcoMech 3.0 used in this work. Besides the core 16 species, the skeletal mechanism by Pichler and Nilsson also contained CH 3 and CH 4 , whereas the Li et al mechanism contained CH 3 , CH 4 , and C 2 H 6 .…”

“…The skeletal mechanism developed by Pichler and Nilsson was based on the AramcoMech 2.0 detailed mechanism, an earlier version of the AramcoMech 3.0 used in this work. Besides the core 16 species, the skeletal mechanism by Pichler and Nilsson also contained CH 3 and CH 4 , whereas the Li et al mechanism contained CH 3 , CH 4 , and C 2 H 6 . The skeletal mechanism developed in this work includes CH 3 , CH 2 , and CH 2 (S) species instead of CH 4 and C 2 H 6 , in comparison with Pichler and Nilsson's and Li et al's mechanisms.…”

“…The experimental results were measured by shock tube facilitated by Pinzón et al The detailed AramcoMech 3.0 mechanism was also simulated, and its results are compared with the experimental results by Pinzón et al As shown by Figure , the skeletal mechanism derived in this work, the detailed AramcoMech 3.0, and the Li et al mechanism exhibit accuracy similar to that of the measured ignition delay times. The skeletal mechanism derived by Pichler and Nilsson shows slightly deviations at high‐pressure and low‐temperature conditions. Overall, all the mechanisms exhibit good performance for ignition of methanol at high‐temperature conditions.…”

“…Seiser et al also proposed detailed and reduced mechanisms for methanol ignition and validated for high‐temperature ignition properties . More recently, a reduced mechanism for methanol combustion in spark‐ignition engines was developed by Pichler and Nilsson and validated against a wide range of combustion conditions. However, the low‐temperature ignition simulations were not included.…”