Efeito da adição de hidrogênio produzido a partir de eletrólise alcalina no desempenho de um motor de combustão interna

Abstract

Hydrogen has important physicochemical and combustion properties that can be used to improve performance and pollutant emissions by vehicles. However, storage difficulties may limit the use of the same in internal combustion engines. Thus, in this research, developed in partnership with the Faculty of Mechanical Engineering (FEMEC/UFU), hydrogen gas was produced and consumed immediately to eliminate the need for a storage device. Firstly, a cell for alkaline electrolysis of water was built to produce hydrogen and to use it as a supplementary fuel in an internal combustion engine. In order to analyze the energy efficiency and the capacity of this electrolyzer, three different electrolytes (LiOH, NaOH and KOH) were analyzed. The experimental tests occurred at concentrations of 1 to 10 gmol/L of each electrolyte, with a variation of 1 gmol /L. The highest hydrogen flow rate was obtained using potassium hydroxide as electrolyte and a current of 23.5 A. Three different hydrogen flows (0, 150 and 300 mL/min) were introduced into the engine at three different speeds (1573, 2692 and 3879 rpm). In addition, the torque and power characteristic curves were obtained for each hydrogen flow added to the engine. According to the results, the emissions of unburned hydrocarbons and carbon monoxide decreased, while carbon dioxide emissions increased with the addition of hydrogen. The specific fuel consumption suffered reductions of between 0.20 to 10.43% when compared to the operation without hydrogen. There was an increase in engine torque and power, however, for rotations above approximately 4500 rpm, the addition of hydrogen did not result in changes in these properties. MBT and MBP values presented an average increase of 5.8 and 7.6%, respectively. The most significant effects were obtained with the introduction of 300 mL / min of the gas. It can be concluded that the use of hydrogen as supplementary fuel presented satisfactory results in both engine performance and pollutant emissions. It is believed that more promising results can be obtained with the addition of larger quantities of hydrogen and with control of the other parameters of the engine.