Effect of toluene addition to waste cooking oil on combustion characteristics of a ci engine

•The usability of WCO in diesel engine has investigated.•Toluene were added to diesel-WCO blends and tested in a diesel engine.•Optimum toluene addition ratio investigated.•Successful results were obtained with the toluene addition to WCO-diesel blends. In recent years, significant emphasis has been placed on biodiesel as a renewable and environmentally friendly fuel. However, biodiesel production costs are still higher than commercial diesel fuel and it requires a lot of time and effort. In this study, the usability of waste cooking oils (WCO) in diesel engine without converting to biodiesel was investigated. We blended WCO with diesel fuel at 25% (in vol. 25% waste oil + 75% diesel fuel) and 50% (in vol. 50% waste oil + 50% diesel fuel) ratios. In addition, 5%, 10% and 15% toluene were added to the waste cooking oil-diesel fuel blends to improve its fuel properties. A single-cylinder, direct injection, air cooled, diesel engine was used for engine experiments. The experiments were conducted with a constant engine speed (1800 rpm) and different engine powers (2 kW and 4 kW). The results show that toluene addition is effective on density, viscosity and calorific value and in-cylinder pressure values. The toluene addition increased the maximum in-cylinder pressure values. The maximum pressure point approached the top dead center (TDC). Improvement in thermal efficiency and BSFC has occurred with the addition of toluene. With the exception of NOx emissions, other emissions were reduced by the toluene addition.