Exhaust Gas Analysis of Various Potential GHG-Neutral Synthetic Fuels and Gasoline/Alkylate-Blends Including Variable Injection Timings

The exhaust gas composition of several potential greenhouse gas neutral C1-based synthetic fuels and gasoline/alkylate-blends are compared to each other and benchmarked against gasoline. The search for sustainable alternatives to conventional fossil fuels is still ongoing. Ideally, the exhaust gas of such an alternative should not deteriorate the environment’s air quality. The testing conducted here is focused on automotive application. However, promising fuel candidates could also be used elsewhere. The gasoline/alkylate blends investigated contain various percentages of dimethyl carbonate (DMC) or methyl formate (MeFo). Various methanol-MeFo mixtures as well as a 65 vol% DMC+ 35 vol% MeFo mixture are investigated as examples for a pure synthetic fuel. The tests are carried out on a single-cylinder spark ignition research engine. To analyze the gaseous emissions a state-of-the-art FTIR, equipped with a specifically tailored evaluation method, and conventional exhaust gas analyzers are used. In addition, particle emissions with 10 and 23 nm cut-off size are measured. Specific focus is set on the start of injection timing influence. Several possible injection-timing optimizations for a pure synthetic fuel are shown. The adequate functionality of a non-adapted three-way catalytic converter (TWC) is confirmed for such an oxygenated fuel. The working TWC validates the detected stoichiometric air-fuel ratio. Further, it was shown that unburned or only partially burned DMC and MeFo are converted by the TWC over a wide air-fuel ratio range, even up to an air-fuel equivalence ratio of 1.5.