Flashback control in supplying onboard-produced HHO to enrich gasoline-fueled motorcycle engines

Abstract

Enriching gasoline with onboard-produced HHO presents a promising solution to enhance motorcycle engine performance and mitigate greenhouse gas emissions. However, flashback, arising from residual HHO in the intake manifold, poses a significant challenge. This study examines the distribution of the hydrogen-air equivalence ratio in the intake manifold using various HHO supplying methods: continuous induction method (CIM), discontinuous induction method (DIM), and venturi injection method (VIM). The results identify the maximum HHO flow rate for each method to prevent flashback occurrence. Supplying HHO through CIM with the nozzle located at the butterfly valve is suitable for HHO flow rates below 8 LPM, corresponding to a gasoline substitution of 7.3%. When supplying HHO through the nozzle positioned at the venturi throat using CIM and DIM methods, the maximum flow rates are 2 LPM and 5.33 LPM, respectively, corresponding to gasoline substitutions of 1.6% and 2.5%. HHO can be safely supplied at higher flow rates through the vacuum valve by controlling the pressure at the retrofitted venturi throat. With an injection pressure of 0.7 bar and an injection duration angle of 80 degrees CA, the gasoline substitution can reach 17.7% without the risk of flashback. The CIM with the nozzle located at the butterfly valve is an appropriate solution for supplying the minimum HHO flow rate to enhance combustion characteristics. The VIM is advantageous for supplying high HHO flow rates, significantly improving engine performance, increasing gasoline substitution, and reducing greenhouse gas emissions.