Numerical study of novel OME1–6 combustion mechanism and spray combustion at changed ambient environments
image: Measured and 0D-simulated O2, CO, CO2, H2, CH4 mole fraction profiles in OME oxidation (symbols: measurements; red lines: simulation results with the Niu mechanism; blue lines: simulation results with the SJTU mechanism).
Credit: Frederik Wiesmann, Zeyan Qiu, Dong Han, Lukas Strauβ, Sebastian Rieβ, Michael Wensing & Thomas Lauer.
Oxymethylene ethers (OMEs), a class of oxygenated e-fuels, are recognized for their potential to enable soot-free combustion due to the absence of carbon–carbon bonds. These properties make OMEs promising candidates for climate-neutral compression-ignition engines. However, accurate computational fluid dynamics (CFD) simulations of OME combustion require reliable oxidation mechanisms. Previous mechanisms, such as the one developed by Niu et al., consistently underestimated ignition delay times (IDTs) and high-temperature reaction intensities under varied ambient conditions, limiting predictive accuracy.
In a study published in Frontiers in Energy, Frederik Wiesmann and collaborators from TU Wien, Shanghai Jiao Tong University (SJTU) and Friedrich-Alexander-Universität Erlangen-Nürnberg introduced a refined oxidation mechanism for OME1-6. The new SJTU mechanism modifies key reaction rates in the Niu mechanism based on sensitivity analysis and validation against jet-stirred reactor (JSR) experiments and shock tube IDT data from the literature. This mechanism improves the prediction of intermediate species and ignition behavior while maintaining compatibility with CFD frameworks.
The SJTU mechanism was integrated into spray combustion simulations under high-pressure, high-temperature constant-pressure chamber conditions and validated using OH+-chemiluminescence measurements. Results demonstrated significant improvements in IDT predictions across temperatures ranging from 800 K to 1000 K and oxygen levels of 15% and 21%, while retaining accurate predictions for flame lift-off length. The new mechanism also enhanced the prediction of formaldehyde (CH2O) distribution, showing elevated concentrations along the spray centerline, which aligns more closely with experimental observations. However, both mechanisms still overpredicted high-temperature reaction zones in spray shear layers.
This work provides a validated reaction mechanism that enhances the predictive capability of OME spray combustion simulations, supporting the development of efficient and clean combustion systems. The study highlights the importance of accurate low-to-high temperature reaction transitions and suggests further investigation into turbulence modeling. These findings contribute to supporting the design of future combustion systems using oxygenated e-fuels, as outlined in the paper's conclusion.
Original source:
https://link.springer.com/article/10.1007/s11708-024-0926-8
https://journal.hep.com.cn/fie/EN/10.1007/s11708-024-0926-8
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