| Abstract: | In this paper, high-speed imaging and spectrometry diagnostics were used to study the spray flame structures and emission spectra of polyoxymethylene dimethyl ethers(PODE) in an optical constant volume vessel. The effects of oxygen volume fraction(15% to 80%) on some typical combustion characteristics such as spatially integrated natural intensity, flame propagation speed, lift-off length and the distribution of flame emission spectra were investigated. The results show that the PODE spray flame mainly exhibits blue chemiluminescence, which is different from the diesel yellow diffusion flame dominated by soot radiation. As the oxygen concentration increases, the flame natural luminosity and propagation speed increases, the position of lift-off region and flame tip move towards the injector nozzle, and the flame width becomes narrower. According to the spectral results, the blue chemiluminescence generated by carbon monoxide oxidation dominates the PODE flame luminescence,suggesting that no soot is formed. The increase in oxygen concentration leads to enlarged intensity and gradient of PODE flame radiation. In summary, the combination of PODE and oxygen-enriched combustion shows no soot formation and promotes the oxidation of carbon monoxide and unburned hydrocarbon. This study can provide more insights into PODE spray combustion,and offer guidelines for achieving efficient and clean combustion. |
