Adjusting mixture composition of alcohol-based fuels for improving combustion in a 0.99cc miniature IC engine

[Display omitted] •Tested engine is the smallest IC engine that has been used for combustion diagnosis.•Effect of hydrogen peroxide addition on the micro-combustion was investigated.•The optimum amount of nitromethane added for the micro-combustion was determined.•Promotion effect of nitromethane on the micro-combustion is reflected in ignition stage. The method of adjusting alcohol-based fuel composition to improve the micro combustion of the miniature glow-ignition IC engine was studied experimentally. Combustion diagnosis of a 0.99cc IC engine indicates that when burning methanol-castor oil fuel or ethanol-castor oil fuel, combustion cyclic variation is severe, partial burning and misfiring is frequent, heat-release is slow, and combustion duration is rather long. Based on these two reference fuels, nitromethane and hydrogen peroxide solutions were added respectively for combustion-supporting investigation. It is confirmed that nitromethane can efficiently promote the improvement of combustion while hydrogen peroxide solution fails to show the expected effect. However, the combustion stability is sensitive to the amount of nitromethane added, the best combustion characteristics can be achieved for the methanol-castor oil-nitromethane fuel when the volume fraction of nitromethane is 15 %. On the other hand, combustion of ethanol-castor oil-nitromethane fuel is obviously worse than that of methanol-castor oil-nitromethane fuel, partial burning and misfiring can be diagnosed under all the condition of nitromethane volume fraction. For the glow-ignition micro combustion of the miniature IC engine, the benefits of adding nitromethane into the fuels are mainly embodied in affecting on the ignition stage, which results in a suppression for partial burning and misfiring.