Experimental Study of the Performance of a Stationary Diesel Engine Generator with Hydrogen Supplementation

Abstract

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 H2/air ratios by volume between 0 and 0.7% and the second with H2/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 H2 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. O2, SO2, and CO emissions decreased as the hydrogen in intake stream increased. As the hydrogen flow rate in intake air increased NO2 emissions increased, NO emissions and NOx emissions decreased up to 50 dm3/min of H2 and then increased up to 150 dm3/min of H2. 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.