A researcher at Brunel University in the UK has identified an optimal blend comprising oxymethylene ethers (OMEn = 1–5 series) with diesel aimed at simultaneously reducing soot and NO_x emissions while enhancing fuel efficiency.

Farhad Mazari identified the optimal blend through experimentation and computational fluid dynamics (CFD) modeling. The study employs the response surface method (RSM) for regression analysis and integrates machine learning techniques for predictive modeling to assess various fuel compositions and optimize the mixture for improved combustion dynamics.

The paper is published in the journal Fuel.

Oxymethylene ethers (OMEs), characterized by the formula H₃CO–(CH₂O) n–CH₃ (n = 1–5), have emerged as promising synthetic fuels due to their oxygenated nature. A key advantage of OMEs is the absence of carbon–carbon (C–C) bonds, resulting in lower carbon emissions and soot-free combustion.

Previous studies underscore the environmental benefits of OMEs, particularly OME₁ through OME₅ as standalone fuels, consistently demonstrating near-zero soot emissions and improved combustion efficiency. … However, blending OMEs presents challenges, including reduced thermal efficiency … despite decreases in soot, hydrocarbons (HC), and carbon monoxide (CO) emissions. This trade-off is primarily due to the lower energy density of OMEs compared to traditional diesel fuel, leading to higher fuel consumption and operational costs.

… The challenge of utilizing OMEs with varying chain lengths lies in striking a balance between reducing emissions and optimizing efficiency. Short-chain OMEs like OME₁ typically improve emissions profiles, while longer chains such as OME_3-5 may lead to increased NO_x emissions and present challenges related to heat capacity and viscosity … This study aims to address this gap in knowledge by optimizing fuel through a blend of OME_1-5 with diesel to enhance combustion efficiency and achieve the most favorable trade-off between soot and NO_x emissions while investigating the impact of different OME chains on combustion timing and characteristics.

The novelty of this study lies in investigating an optimal blend of diesel and OMEs to enhance the fuel mixture’s energy density and heating value while reducing soot and NO_x emissions. By utilizing computational fluid dynamics (CFD) and a linear regression machine learning method, this research aims to identify the most effective blend. This approach not only tackles the low heating value problem of OMEs but also optimizes the combustion process for improved efficiency and reduced emissions, offering a comprehensive solution to the challenges linked with utilizing OMEs as alternative fuels.

—Mazari 2024

Mazari used an optical constant volume combustion chamber (CVCC) to confirm the blend’s effectiveness in reducing both soot and NO_x emissions. The investigation thoroughly analyzes spray combustion properties, including injection duration, Start of Combustion (SOC), End of Combustion (EOC), Lift-Off length of fuels, spray tip penetration, and their impact on combustion efficiency.

Analysis of energy densities between the blends revealed that OME-Diesel (OMED) blend exhibits a heating value superior to OME_2-5 but inferior to diesel, striking a balance in energy output. Furthermore, OMED demonstrates superior energy density compared to OME_1-3 and diesel, highlighting its potential for enhanced fuel efficiency.

The optimized blend achieves a significant 78.2% reduction in soot emissions and a 31.3% reduction in NO_x emissions compared to conventional diesel, underscoring its efficacy in mitigating harmful emissions without compromising combustion performance.

Resources

• Farhad Mazari, “A study on emission reduction and combustion efficiency, analyzing oxymethylene ether (OME1-5) with diesel fuel,” Fuel, Volume 375, 2024, doi: 10.1016/j.fuel.2024.132578.