Experimental evaluation of low-displacement compression ignited engines operating with hydroxy gas as a supplementary gaseous fuel

A large proportion of annual production of worldwide greenhouses gases results from the use of internal combustion engines. This experimental work evaluates the influence of dual-fuel operation on the overall emissions of a low-displacement compression-ignition engine based on operational conditions such as torque, rotational speed, and load. Hydroxy gas is used as a supplementary gaseous fuel while using pure diespel or palm oil biodiesel as baseline fuels. The CO, CO(2), NO(x), and HC emissions levels were carefully characterized through experimental measurements and statistical analysis. The influence of hydroxy enrichment was also examined on the engine's fuel consumption. The study incorporates an in-house hydroxy generator to store and supply the gas in the intake air system using an electrolyzer. The results demonstrated that the ANOVA analysis provides accurate predictions compared to experimental measurements with less than 5% relative error. The use of hydroxy reduces the SFC by up to 25%, which represents an economic advantage of dual-fuel operation, additionally it decreases CO, HC, and CO(2) emissions. However, with hydroxy enrichment, NO(x) emissions levels escalate at medium and high loads. Overall, hydroxy enrichment demonstrates to be a robust alternative from an environmental and economic perspective. Future research will be focused on evaluating the biodiesel – hydroxy dual operation, broadening the spectrum of biodiesel concentration percentages, and selecting different raw materials for biofuel production.