Evaluation of oxidation stability and engine behaviors operated by Prosopis juliflora biodiesel/diesel fuel blends with presence of synthetic antioxidant

This experimental study focuses on analyzing the oxidation stability, engine performance, and combustion characteristics of Prosopis juliflora biodiesel blended with synthetic antioxidants. In the first stage, four synthetic antioxidants such as Butylated Hydroxy Toluene, Propyl Gallate, Pyrogallol, Tert-Butyl-Hydroquinone (TBHQ) were selected to evaluate their oxidation stability. Resultantly, TBHQ was the best synthetic antioxidant with the highest induction period, corresponding to 10.19 h, among the above-mentioned synthetic antioxidants while it was added to the B20 blend (20% Prosopis juliflora biodiesel/80% diesel fuel). In the second stage, different concentrations of TBHQ (500, 1000, and 1500 ppm) were added to B20 sample for the test of performane, combustion, and emission characteristics of a 4-stroke diesel engine. Indeed, adding TBHQ to the B20 sample increased brake thermal efficiency and emissions of CO and HC, while it reduced brake-specific fuel consumption and emissions of NOx and CO₂. Furthermore, it could be observed a decrease in peaks of in-cylinder pressure and heat release rate, and an increase in mass fraction burned as adding TBHQ. In general, the use of TBHQ antioxidant-included biodiesel for diesel engines could improve engine performance and emission, and enhance the fuel' oxidation stability.