**Diethyl Ether as an Oxygenated Additive for Fossil Diesel**/**Vegetable Oil Blends: Evaluation of Performance and Emission Quality of Triple Blends on a Diesel Engine**

**Laura Aguado-Deblas 1, Jesús Hidalgo-Carrillo 1, Felipa M. Bautista 1, Diego Luna 1, Carlos Luna 1, Juan Calero 1, Alejandro Posadillo 2, Antonio A. Romero 1 and Rafael Estevez 1,\***


Received: 14 February 2020; Accepted: 23 March 2020; Published: 25 March 2020

**Abstract:** The aim of this work is to analyze the effect of using diethyl ether (DEE) as an oxygenated additive of straight vegetable oils (SVOs) in triple blends with fossil diesel, to be used in current compression ignition (C.I.) engines, in order to implement the current process of replacing fossil fuels with others of a renewable nature. The use of DEE is considered taking into account the favorable properties for blending with SVO and fossil diesel, such as its very low kinematic viscosity, high oxygen content, low autoignition temperature, broad flammability limits (it works as a cold start aid for engines), and very low values of cloud and pour point. Therefore, DEE can be used as a solvent of vegetable oils to reduce the viscosity of the blends and to improve cold flow properties. Besides, DEE is considered renewable, since it can be easily obtained from bioethanol, which is produced from biomass through a dehydration process. The vegetable oils evaluated in the mixtures with DEE were castor oil, which is inedible, and sunflower oil, used as a standard reference for waste cooking oil. In order to meet European petrodiesel standard EN 590, a study of the more relevant rheological properties of biofuels obtained from the DEE/vegetable oil double blends has been performed. The incorporation of fossil diesel to these double blends gives rise to diesel/DEE/vegetable oil triple blends, which exhibited suitable rheological properties to be able to operate in conventional diesel engines. These blends have been tested in a conventional diesel engine, operating as an electricity generator. The efficiency, consumption and smoke emissions in the engine have been measured. The results reveal that a substitution of fossil diesel up to 40% by volume can be achieved, independently of the SVO employed. Moreover, a significant reduction in the emission levels of pollutants and better cold flow properties has been also obtained with all blends tested.

**Keywords:** diethyl ether; castor oil; sunflower oil; straight vegetable oils (SVO); biofuel; diesel engine; electricity generator; smoke opacity; Bosch smoke number
