Experimental evaluation of a hydroxyl (HHO) assists effect on combustion, emissions and engine performance for the Gasoline/CNG Bi-fuel engine

Abstract

Hydrogen is a promising alternative energy source with many good combustion qualities that can be applied to enhance the bi-fuel engine performance emissions. This study aims to evaluate the gasoline/CNG bi-fuel engine combustion characteristics, performance, and emissions by an oxy-hydrogen (HHO) boost. HHO kit gas production at various electrolyte concentrations following the installation of the generators with two catalysts for KOH and NaOH was investigated to be optimal in terms of energy efficiency. Extensive experimental studies were carried out for engine speeds between 1500 and 5000 rpm under WOT conditions at the HHO boost rate of 0.4, 0.8 and 1.2 LPM with intake air of the engine while monitoring variables like brake-specific fuel consumption (BSFC), in-cylinder pressure (ICP), in-cylinder temperature (ICT), exhaust gas temperature (EGT), heat release rate (HRR) and emissions for both fuels. The findings suggest that HHO boost enhances a bi-fuel engine's combustion and performance compared to pure fuel at a constant engine load of 60 Nm, the peak ICP, ICT and HRR increased by 5.3 %, 13 % and 7 % respectively under a 1.2 LPM HHO additive. The experimental results demonstrated that HHO boost generally had lower BSFC approximately (6.5 %–18.8 %) for gasoline and (3.6 %–10.2 %) for CNG fuel. Additionally, the overall thermal efficiency (OTE) increases around (5.1 %–17.3 %) for gasoline and (6.1 %–16.2 %) for CNG fuel with an HHO boost. The average values of THC, CO₂, and CO concentrations are considerably reduced by 12 %, 22.5 % and 25.5 % for gasoline and 15.6 %, 19.7 % and 35.7 % for CNG fuel respectively. Nonetheless, NO_X emission was increased in the gasoline fuel but exhibits erratic behavior for CNG fuels. HHO addition is therefore a practical and efficient strategy to improve emission and performance in gasoline/CNG bi-fuel engines.