Combined effects of a novel reduced graphene oxide-enriched diesel-hazelnut biodiesel-tetrahydrofuran blend on combustion and emission characteristics of a compression ignition engine

Abstract The gradual exhaustion of fossil fuel reserves and the enforcement of stricter emission regulations have driven the search for sustainable and environmentally friendly alternative fuels for compression-ignition engines. In this study, the effects of the combined use of hazelnut biodiesel, tetrahydrofuran (THF), and reduced graphene oxide (rGO) nanoparticles on combustion characteristics, engine performance, and exhaust emissions were experimentally investigated in a diesel engine. Pure diesel, biodiesel–diesel blends, THF-containing blends, and nanofuel blends enriched with 50, 100, and 150 ppm rGO nanoparticles were tested under three engine loads (11, 16.5, and 22 Nm). Combustion analysis was performed using in-cylinder pressure data. The indicated mean effective pressure (IMEP), thermal efficiency (TE), specific fuel consumption (SFC), ringing intensity, combustion duration, maximum pressure rise rate, cyclic variations, and CO, CO₂, HC, and NOx emissions were evaluated. The experimental results showed differences in combustion characteristics, engine performance, and exhaust emissions among the tested fuel blends. Among the tested nanofuels, the highest IMEP increase reached 21.79% at low engine load, and cyclic variations were reduced through improving combustion stability. In addition, CO and NOx emissions decreased by up to 29.41% and 13.09%, respectively. The rGO-containing fuel blends reduced HC emissions by up to 14.9% at high engine load and increased thermal efficiency by up to 3.92%. These findings indicate that fuel blends containing hazelnut biodiesel, THF, and rGO nanoparticles can contribute to improved engine performance and reduced harmful exhaust emissions under the investigated operating conditions.