Study on using graphene and graphite nanoparticles as fuel additives in waste cooking oil biodiesel

Abstract

• Graphene and graphite nanoparticle additives showed lower NO emissions and higher thermal efficiency. • Graphene and graphite nanoparticle additives showed lower BSFC than neat biodiesel fuel. • At full load, both nanoparticles showed similar heat release as compared to neat diesel operation. • The combustion characteristics of fuel blends with graphite additives outperformed that of those with graphene additives. Utilising waste cooking oil biodiesel in internal combustion engines for power generation and transport is of increasing importance, as it is the least pollutant disposal method for waste cooking oil. Besides, researchers have recently shown an increasing interest in utilising graphene and its derivatives in different applications due to its unique thermal and physical characteristics, including enhancing the combustion characteristics of biofuels. Therefore, this article studies the characteristics of waste cooking oil biodiesel blended with few-layered graphene and graphite nanoparticles additives and their influence on combustion and engine emissions and benchmark them against neat biodiesel and diesel fuels. The biodiesel was synthesised through a transesterification method from waste cooking oil and blended with diesel or butanol after adding few-layered graphene and graphite nanoparticles. Few-layered graphene and graphite nanoparticle additives led to greater peak in-cylinder pressure by 0.5–2.5% increment and 1–4% lower heat released rate at full load. As such, employing few-layered graphene and graphite in a fuel mix reduced NOx emission by 0.7–5 % compared to 100% diesel counterpart. Besides, at full engine load, waste cooking biodiesel blended with 100 ppm few-layered graphene and graphite nanoparticles showed an increment in brake thermal efficiency by 8–10% compared to pure fossil diesel and waste cooking biodiesel. The results show the feasibility of using graphene-based nanoparticle additives in biodiesel to enhance biodiesel fuel combustion characteristics, hence lowering NOx emissions.