Abstract:
Oxymethylene ethers (OMEn) are discussed as attractive carbon-reduced alternative fuels because they offer the potential to inhibit the formation of soot particles. In the present study, the effect of oxymethylene ether-1 (OME1) addition to a gasoline surrogate, here the primary reference fuel 90 (PRF90), on ignition delay times and laminar burning velocities was investigated. Ignition delay times of OME1, PRF90, and their blend with OME1 blending fraction of 70% (by liquid vol.) were measured in a shock tube over a wide range of conditions: fuel-air ratio φ = 1.0, dilution of 1:5 with N2, T = 950 K-2000 K, and initial pressures of 1, 4, and 16 bar. Laminar burning velocities of OME1, PRF90, and their blend with OME1 blending fraction of 30% (w/w) were measured by using the cone angle method at a preheat temperature of 473 K, φ = 0.6–2.0, and at pressures of 1, 3, and 6 bar. The experimental data sets have been compared to predictions made using the in-house DLR reaction mechanism, which was developed for surrogate modeling of gasoline, diesel, and jet fuels as well as oxygenated species such as alcohols (C1C4) and oxymethylene ether (OMEn, n = 1–5). The results revealed that the DLR mechanism satisfactorily predicts the experimental data for ignition delay times and laminar burning velocities of both the individual fuels and the blend. Both the experimental and calculation results show that ignition delay times of OME1 / PRF90 are shorter than those of PRF90 for 1, 4, and 16 bar. The values of the measured burning velocities also agree with the corresponding predicted laminar flame speed data, except at high pressure (6 bar) and at high φ values. The effects of increasing OME1 fraction in the blend was tested, with the results showing a corresponding non-linear decrease of ignition delay times. Sensitivity analyses and radical mole fractions analysis calculations were performed to interpret the effect of adding OME1 to PRF90 on ignition delay times and laminar flame speeds.
