Evaluation of the performance and emission and spectroscopic analysis of an improved soy methyl ester

Abstract

Herein, the performance, emission and physiochemical properties of a soy methyl ester (SME) and its combination with methyl oleate (MO) in a common rail direct injection (CRDI) engine were investigated. Moreover, the performance of the engine in terms of brake power (BP), brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and NO_x emission was assessed to compute the characteristics of the combination of SME with MO; the reasons for using MO in the blending process were the better ignition quality, oxidative stability and low-temperature flow properties of MO, striking a balance between oxidative stability and low flow properties. A remarkable reduction in the BSFC and an increase in the BTE were found in the blended biodiesel (S80-MO20, S70-M30, and S50-M50) as compared to the case of SME. The blended biodiesel was also characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis) and nuclear magnetic resonance (NMR) spectroscopy. In the FTIR spectra, a peak was observed at 1745 cm⁻¹, confirming the presence of a triglyceride ester linkage. Since UV-vis spectroscopy is an affordable technique, herein, it has been employed to detect the presence of conjugated dienes in the oxidized biodiesel. The linear line fitted for absorbance versus the percentage of the blended fuel at 320 nm showed a high coefficient of determination (R² = 0.9454). In addition, H NMR spectroscopy was employed to study the oxidative stability of the blended fuel. Different functional groups with their respective peaks (in ppm) are indicated in the NMR spectra.