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Sulfur free synthetic diesel fuels can be produced using gas to liquids (GTL) technology, and may prove useful as a substitute for conventional diesel fuels when oil reserves are depleted. With non-detectable amounts of sulfur and aromatics, these fuels should generate lower emissions and enable catalytic clean up. This paper presents the results of a durability test conducted on a Detroit Diesel Series 50 diesel engine-generator operating on two synthetic GTL diesel fuels. Besides providing a comparison of diesel emissions, the paper also provides a comparison of generator fuel efficiency and brake specific fuel consumption between the synthetic fuels and conventional diesel. Documented emissions include total hydrocarbons (THC), carbon monoxide (CO) and oxides of nitrogen (NOx). All tests on the diesel engine reported were conducted at the factory set injection timing. As the best performance of an engine on a particular fuel may be affected by injection timing, further tests of the synthetic fuels at different injection timings are needed and will be discussed in future work.

Recent claims of engine efficiency improvement via hydrogen generated by small electrolyzers have been made by numerous businesses selling these devices. The technical literature indicates that using hydrogen in gasoline internal combustion results in some improvement in engine emissions. Literature with detailed experimental results with hydrogen supplementation in a stationary diesel engine generator set was not found. This paper presents the results of the experiment that was conducted on a 125 kW stationary diesel engine generator set by addition of supplementary hydrogen in the intake air stream. The hydrogen was from a compressed hydrogen tank, and the testing was completed in two separate runs, the first with H 2 /air ratios by volume between 0 and 0.7% and the second with H 2 /air ratios by volume between 0 and 2.3%. The upper limits of these ranges are far above the levels provided by the small electrolyzers currently being sold. The experiments were conducted at a constant load of 56 kW and 1200 rpm. It was observed that the amount of fuel energy consumed (the sum of the diesel and H 2 fuel values) remained constant as the engine was run at constant load and that no increase in thermal efficiency occurred. Net indicated work per cycle per cylinder was measured using an in-cylinder pressure sensor. The net indicated work per cycle per cylinder was nearly constant throughout each experiment. Some combustion parameters, such as start of ignition and end of premixed combustion, have been checked and showed no significant variations due to the added hydrogen in the intake air stream. O 2 , SO 2 , and CO emissions decreased as the hydrogen in intake stream increased. As the hydrogen flow rate in intake air increased NO 2 emissions increased, NO emissions and NO x emissions decreased up to 50 dm 3 /min of H 2 and then increased up to 150 dm 3 /min of H 2 . All the above-mentioned changes are relatively small amounts. These results indicate that there is no change in engine efficiency with the addition of hydrogen and only minor changes in emissions. However, the efficiency of the engine system (the engine and its auxiliary components) may increase with the added hydrogen, if the hydrogen is generated from the engine waste energy, such as engine exhaust waste heat.