Main sources of uncertainty in recent methanol/NOx combustion models

Abstract

The performance of 17 recent detailed reaction mechanisms describing the interactions of methanol and formaldehyde with nitrogen oxides in combustion systems was investigated based on large number of literature experimental data covering a wide range of conditions. This data collection consists of 2552 data points of concentration profiles in 243 datasets measured in jet stirred reactors, tubular flow reactors, and shock tubes. The two best mechanisms were found to be the Shrestha-2019 and Glarborg-2018 mechanisms, which were selected for further investigations. Two additional mechanisms were created via the replacement of the hydrogen, syngas, methanol submechanisms, and the parameters of nine N/H/O reactions to ones from our previous mechanism optimization studies. Local sensitivity analysis of the kinetic and thermodynamic parameters (Arrhenius A-factors, heat capacities, standard enthalpies of formation, and standard molar entropies) of these four mechanisms was carried out. The results were in good agreement and the most sensitive reactions belong to the neat hydrogen, syngas, or methanol oxidation. The most important reactions of the interaction between C 1 species and NOx are hydrogen-abstraction reactions CH 3 OH + NO 2 = HONO + CH 2 OH and CH 2 O + NO 2 = HONO + HCO.The most sensitive thermodynamic properties are the molar heat capacities of species OH, NO, HONO, and NO 2 , and the standard enthalpies of formation and entropies of these species have also significant sensitivities. According to the local uncertainty analysis of the kinetic and thermodynamic parameters, the rate coefficients of the NOx chemistry have the highest contribution to the overall uncertainty of the simulation results, especially those of the two reactions above. The highest uncertainty caused by the thermodynamic parameters is due to the heat capacity of HNO, OH, HO 2 , and NO 2 and some other species, whereas the uncertainty contributions of all enthalpies of formation and entropies were negligible.

Skeletal CH3OH/NOx Kinetic Model for Simulating Spark-Ignition and Turbulent Jet Ignition Engines

“…Figure 7 compares simulation results predicted by the present skeletal model and the detailed model from Glarborg et al 22 against experiments at 30 bar. In a previous study, 41 the performance of the Glarborg_2018 22 model was assessed in simulating CH 3 OH/NO x and formaldehyde (CH 2 O)/NO x interactions against a large number of existing experiments, covering a wide range of conditions. This study 41 revealed that among various detailed reaction mechanisms, the Glarborg_2018 22 model exhibited the best accuracy in reproducing these experiments.…”

Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion

“…The NOx emissions are heavily regulated due to environmental and health concerns. − The main formation pathways of NO are identified as the thermal, prompt, NNH, and N 2 O pathways. They are implemented in almost all reaction mechanisms and have been described or reviewed in several recent publications. − While the reaction mechanisms already describe many aspects of NOx formation in different combustion situations adequately, there are still subsets of high-temperature nitrogen chemistry where open questions remain . New nitrogen-containing fuels, for example, ammonia or biomass, are employed as energy carriers and storage to reduce CO 2 emissions.…”

Recent Progress on Hydrogen Storage and Production Using Chemical Hydrogen Carriers

“…Their source can be both the fuels themselves contaminated with nitrogen compounds and air. Pure methanol burns with no nitrogen oxides; moreover, the addiction of first-order alcohols (methanol, ethanol) to the combustion system allows for the reduction of nitrogen oxide emissions [53][54][55]. The last method for obtaining hydrogen-rich gas from methanol is autothermal reforming, combining POM and MSR.…”