Beating neat fuels by dedicated blending: Performance analysis of bio-hybrid fuel blends on a spark-ignition engine for passenger car applications

Abstract

The alcohol fuel ethanol is well known for its favorable engine performance in terms of both high net indicated efficiency and low nitrogen oxide emissions. Other alternative neat fuels such as 2-butanone were not able to outperform ethanol in its engine performance. In addition, ethanol has lower production costs compared to 2-butanone, which makes ethanol even more attractive. To compete with neat fuels, model-based fuel design was introduced to tailor fuels by means of dedicated blending of neat alternative components. First, a blend consisting of ethanol, 2-butanone, cyclopentane, and cyclopentanone (EBCC) was defined. Second, a ketone–ester–alcohol–alkane (KEAA) blend consisting of methyl isopropyl ketone, methyl acetate, ethyl acetate, ethanol, methanol, and pentane was developed. Both blends were optimized regarding their production costs while simultaneously considering fuel properties such as the octane number, the oxygen content, and the enthalpy of vaporization. Although both blends showed promising fuel properties, their performance in an internal combustion engine was not evaluated in the fuel design process. This study presents investigations of both blends on a thermodynamic spark-ignition single-cylinder engine for passenger car applications with a compression ratio of 16.4. In particular, a variation of the engine load at an engine speed of 2000 1/min and two variations of the relative air/fuel ratio at the same engine speed and net indicated mean effective pressures of 6 bar and 15 bar were performed. The combustion behavior of the two blends was compared to that of neat ethanol, neat 2-butanone, and conventional gasoline pump fuel. In addition, 0D/1D simulations were performed to evaluate the efficiency losses during the combustion. EBCC achieved a maximum net indicated efficiency of 46.9% at a net indicated mean effective pressure of 15 bar and a relative air/fuel ratio of 1.7, exceeding ethanol’s maximum net indicated efficiency of 46.0% in the same operating point. KEAA achieved a lower net indicated efficiency than ethanol and was on the same level as neat 2-butanone, resulting in a maximum net indicated efficiency of 45.0% in the same operating point. This work shows that the combustion performance in an internal combustion engine should be considered in the fuel design process to better predict promising fuel candidates from an engine perspective.