The aim of the present investigation is to examine the characteristics of diesel engine for varying concentrations of diethyl ether (DEE) as an oxygenated additive in repurpose used cooking oil (RUCO) biodiesel and diesel blends. In the beginning, several pilot experimentations are carried out on diesel and B20 blend. Afterward, 0.8%, 1.6%, 2.4%, 3.2%, and 4% of DEE was blended with biodiesel/diesel. The IS standards are followed for investigating the various properties of biodiesel blends. Property investigation results revealed that the increasing concentration of DEE reduces the density, viscosity, calorific value, flash point with increase in cetane number. All the prepared blends are examined on water-cooled diesel engine at six distinct loads and constant engine speed. The investigation revealed that the BTE (brake thermal efficiency) increased by 16.06% while BSFC (brake specific fuel consumption) decreased by 4.12% for 0.8% concentration of DEE in a blend when contrasted with diesel. All tested fuel shows nearly the same trend of BSEC at all loading conditions and compression ratios. Further, the CI engine fueled with biodiesel-DEE-diesel blends has shown 20.41%, 34.69%, and 23.33% a maximum reduction in CO, HC, and NOx emissions as compared to diesel fuel at notable working conditions. The CO₂ emission reduced in ternary blends due to lower carbon content in the blend. It can be noted that the minimum 0.8% concentration of DEE at CR15 in the ternary blend provided significant increment in BTE as 16.06%, with a 4.12% reduction in BSFC while CO, HC and NOx emissions minimized by 15.07%, 3.45%, and 14.70% than that of diesel fuel. In minimum concentration of DEE, the A0.8B19.2 blend provided luminous results in both performance and emission characteristics at CR15.

A study of the existing literature on the effects of diethyl ether with different biodiesels such as Fish, Neem, Calophyllum Inophyllum, Cottonseed, and Soybean biodiesel was undertaken. Till date, no study related to the combined effects of repurpose used cooking oil biodiesel/diethyl ether/diesel blends and different compression ratios with different loading conditions has been reported in the literature. Moreover, the current study reveals that there are some major flaws in the existing scenario such as no reduction in harmful exhaust gases such as carbon dioxide, hydrocarbon, carbon monoxide, and nitrogen oxide. There is no noticeable improvement in the performance characteristics such as brake thermal efficiency and brake specific fuel consumption. This investigation has been carried out for controlling harmful emissions and improving the performance of the engine. The present study investigates the combined impact of compression ratios on emission and performance characteristics of a diesel engine using ternary blends in comparison with diesel. This study provides eco-friendly working conditions that result in fewer emissions with improved performance. The results show that a higher compression ratio is useful for minimizing nitrogen oxide emission, while a lower compression ratio is useful for minimizing carbon monoxide emission. CR16 works effectively with a higher proportion of diethyl ether (2.4 and 3.2%) and provides better results for minimizing emissions with improved performance. The following eco-friendly blends delivered lower emissions with improved performance. These blends are: A0.8_B19.2: CR16 and CR15; A1.6_B18.4: CR17 and CR16; A2.4_B17.6: CR16, CR15, and CR14; A3.2_B16.8: CR16 and CR15.