An experimental and modeling study on polyoxymethylene dimethyl ether 3(PODE_(3))oxidation in a jet stirred reactor

Polyoxymethylene dimethyl ether(PODE n,n≥1)is a class of oxygenated fuels containing unique carbon-oxygen chain structure and a promising alternative fuel for diesel engines.In this study,low-temperature oxidation characteristics of PODE_(3) were studied experimentally and numerically.Experiments were performed in a jet-stirred reactor(JSR)at equivalence ratios of 0.5,1.0 and 2.0,in the temperature range of 500 to 950 K,and at atmospheric pressure.Mole fractions of PODE_(3),O_(2),H_(2),CO,CO_(2),CH_(3) OH and C_(1)-C_(2) hydrocarbons were measured by gas chromatograph(GC).Experimental measurements were compared with the simulation results based on two literature low-temperature oxidation models,denoted as the He model and the Cai model,respectively.Good agreement was obtained between the measured and simulated fuel consumption profiles,while a deviation was observed between the experimental and simulation results on the mole fractions of O_(2) and intermediate products at medium temperatures.Reaction pathway analyses based on the two models were performed,revealing that the second O_(2)-addition reaction pathway is more significant in the prediction by the Cai model than that by the He model.Sensitivity analyses pointed out that the most important reactions affecting fuel consumption are the H-abstraction reactions of PODE_(3),and the decomposition of H_(2) O_(2) and the consumption of CH_(2)O become more sensitive at medium temperatures.

Numerical study of novel OME1-6 combustion mechanism and spray combustion at changed ambient environments

For a climate-neutral future mobility,the socalled e-fuels can play an essential part.Especially,oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly lower soot levels.In particular,polyoxymethylene dimethyl ethers or oxymethylene ethers(PODEs or OMEs)do not contain carbon-carbon bonds,prohibiting the production of soot precursors like acetylene(C2H2).These properties make OMEs a highly interesting candidate for future climate-neutral compression-ignition engines.However,to fully leverage their potential,the auto-ignition process,flame propagation,and mixing regimes of the combustion need to be understood.To achieve this,efficient oxidation mechanisms suitable for computational fluid dynamics(CFD)calculations must be developed and validated.The present work aims to highlight the improvements made by developing an adapted oxidation mechanism for OME1-6 and introducing it into a validated spray combustion CFD model for OMEs.The simulations were conducted for single-and multi-injection patterns,changing ambient temperatures,and oxygen contents.The results were validated against high-pressure and high-temperature constantpressure chamber experiments.OH*-chemiluminescence measurements accomplished the characterization of the auto-ignition process.Both experiments and simulations were conducted for two different injectors.Significant improvements concerning the prediction of the ignition delay time were accomplished while also retaining an excellent agreement for the flame lift-off length.The spatial zones of high-temperature reaction activity were also affected by the adaption of the reaction kinetics.They showed a greater tendency to form OH*radicals within the center of the spray in accordance with the experiments.