Study on fermentation gas combustion with hydrogen addition under various throttle openings

Regional energy systems are designed to contribute to a green and “carbon neutral” economy of localities. In this system, the engine combustion is significant for power generation. Therefore, this study mainly investigated the effect of throttle openings on the combustion characteristics of hydrogen (H2) and methane (CH4) mixtures to achieve high efficiency. Throttle opening has a strong relationship with combustion performance, particularly for power output and efficiency. Therefore, 10%, 20%, 40%, and 100% throttle openings were tested to obtain higher efficiency for power generation. Combustion characteristics of CH4 and CH4+H2 were also compared. With H2 addition, the volume percentage of H2 varied between 10%, 30%, and 50%. The ratio of air to gas fuel was controlled to determine λ varying from 1.0 to 1.4. Subsequently, the effect of throttle openings under different λ with H2 addition was examined. Finally, brake thermal efficiency (BTE), power output, brake mean effective pressure (BMEP) and brake specific fuel consumption (BSFC) were compared. Moreover, the maximum value of the cylinder pressure in cycles (Pmax) and the coefficient of variation (COV) in Pmax were discussed. The results showed that the torque and power output decreased slightly from full throttle opening to 40% throttle opening. The 30% H2 addition in Case # 5 (full opening under lean-burn conditions) is the best working condition to satisfy both the power generation and energy-saving requirements in this study. Furthermore, Pmax decreased with smaller throttle opening, and H2 addition increased Pmax. In addition, H2 addition decreased COV, but throttle opening had less effect on COV.