Energy Effect of the Degree of Hydration of Ethanol and the Air Excess Coefficient (a) on the Use of Ethanol-Gasoline Mixtures in Spark Ignition Engines

Abstract

The objective of this study was to evaluate energetically the effect of hydration degree and mixture type (rich mixture α = 0,85 and lean mixture α = 0,15) on the use of ethanol and gasoline mixtures in spark ignition engines. The experiments were carried out in the Propulsion Laboratory of the Faculty of Engineering Sciences of Agrarian University of Havana (AUH). The JACTO model engine used has an effective power of 1,2 kW, speed 580 rpm, combustion chamber volume 34 cm³. Before combustion, the degree of ethanol hydration was determined (80 %; 85 %; 90 %; 95 %). Taking into account the influence of the percentage of purity of ethanol and air excess coefficient (α), when using combustible mixtures, analyses were carried out on the following parameters: air-fuel ratio (r_a/f) and fuel-air ratio (r_f/a); internal energy of combustion products (U_z); the number of moles of raw materials in the mixture for gasoline engines (M₁) and the number of moles of products during combustion (M₂). Based on the experimental work performed and the energy analysis of the combustion process, it was shown that the mixture of gasoline E-10-EH-80 % received more air and fuel than ratio necessary to achieve combustion, reaching 11,781 kg (air)/kg (fuel) for α = 0,85 and 15,309 kg (air)/kg (fuel) for α = 1,15. This is due to the fact that this is a mixture with increased moisture, because it contains more oxygen atoms, which impoverishes the mixture, and guarantees the best quality in the combustion process. But rich mixtures (α = 0,85) were the most energy efficient, which is associated with an increase in the octane number, that is, the antiknock ability of the fuel mixture used, which improves the quality of combustion, although it reduces the energy output during an explosion (detonation).