An Assessment of the Performance and Emissions of an Otto Power Generator Group Operating with Wet Ethanol at a High Volumetric Compression Ratio

Abstract

This work presents an experimental study of the performance and emissions of an internal combustion engine operating in the Otto cycle with a high volumetric compression ratio (17:1). The engine was initially fueled with the standard ethanol used in Brazil, with 7% distilled water (E93W07); we then studied the effects of using different ethanol-in-water mixtures, or ‘wet ethanol’, with 17%, 27%, 37%, and 47% distilled water concentrations. The tests were carried out with power loads of 5.0–25.0 kW at 5.0 kW intervals and with power loads of 27.5–35.0 kW at 2.5 kW intervals, whether by adding up the loads or by taking them away. The ignition timing was changed to evaluate each load imposed on the engine to avoid knocking. Specific fuel consumption (SFC), brake thermal efficiency (BTE), carbon dioxide emissions (CO2), carbon monoxide (CO), nitrogen oxides (NOx), and total hydrocarbon content (THC), as well as the internal pressure in the cylinder and the heat release rate, were measured, and the results are compared. The results show a reduction in CO and NOx and an increase in THC emissions. However, there were no significant changes in CO2 emissions when the distilled water percentage in ethanol increased. Regarding the brake thermal efficiency, it was observed that it remained approximately constant for all blends, with the same load being applied to the engine shaft, reaching a maximum value of 35%. The results obtained confirm the technical feasibility of operating an internal combustion engine in the Otto cycle with a high volumetric compression ratio using ethanol with up to 47% distilled water without significant loss of performance.

Keywords

• power generation group
• biofuel
• wet ethanol
• performance
• emissions
• high compression