Impact of various lambda values on engine performance, combustion and emissions of a SI engine fueled with methanol-gasoline blends at full engine load

Abstract

The aim of this study is to investigate experimentally the effects of methanol-gasoline fuel blend on engine performance, combustion process, and exhaust emissions of a spark ignition (SI) engine under various lambda values at full engine load. Firstly, the methanol was blended with gasoline by volume fraction of 20%, which renamed as M20. The experiments were performed a constant engine speed at 2000 rpm and full load conditions. Then, the M20 fuel blend effects on the engine performance, combustion and exhaust emission characteristics were compared with pure gasoline fuel in terms of brake engine torque, brake specific fuel consumption (BSFC), thermal efficiency, combustion process, CO, CO2, HC and NO emissions at three different lambda values such as 0.8, 1, 1.2. It was found that the addition of methanol substantially affected the engine performance, combustion process, and exhaust emissions at various lambda values. The methanol properties such as higher oxygen content, octane number, laminar flame speed (LFS), latent heat vaporization, and lower calorific value, and also the variation of the air-fuel ratio of the test fuels substantially influenced on the test results. Furthermore, these properties considerably affected the combustion characteristics such as ignition delay (ID), and combustion duration (CD). According to obtained results, the highest engine performance was observed for gasoline at λ=1. The M20 test fuel was exhibited a better combustion process when at λ=0.8 among other lambdas compared to gasoline. However, the best emission performance was obtained at λ=1 for the M20. Thus, the M20 test fuel can be used as a fuel considering the combustion and exhaust emissions. Overall, the engine performance, combustion, and exhaust emission characteristics are considerably affected by the variety of air-fuel ratio, oxygen content, octane number, LFS, and latent heat vaporization properties.