The effect of thermal conductivity and stably dispersed graphene nanoplatelets on Sterculia foetida biodiesel-diesel blends for the investigation of performance, emissions, and combustion characteristics on VCR engine

The present study investigates the use of a Sterculia foetida biodiesel-diesel sample (B20) and graphene nanoplatelets (GNPs) at 60 ppm with different agents (non-ionic surfactant Span 80), surfactant cetyl trimethyl ammonium bromide (CTAB), and dispersant (QPAN 80) at various compression ratios (16:1, 17:1, and 18:1) in a diesel engine. The surface-modified GNPs (using an optimum ratio of 1:1 GNPs to agent) were added to the B20 blend using a bath and a probe sonicator. The prepared samples were analyzed for characterization using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), fourier transform infrared (FTIR), X-Ray diffraction (XRD), thermogravimetric analysis (TGA), and thermal conductivity. The highest stability was observed for the dispersant-added GNPs-B20 blend (B20 + GNPs 60 mg/L + QPAN 80 mg/L). In overall engine performance, brake thermal efficiency (BTE), cylinder pressure (CP), and net heat release rate (NHRR) were increased by 11.56, 18.61, and 15.88%, respectively, whereas brake-specific fuel consumption (BSFC), ignition delay (ID), and combustion duration (CD) were reduced by 27.5, 17.10, and 15.34%, respectively. Carbon monoxide (CO), unburnt hydrocarbon (UHC), nitrogen oxide (NO x ), and smoke opacity were reduced by 13.24, 23.04, 5.20, and 59.84%, respectively, for the B20 + GNPs 60 mg/L + QPAN 80 mg/L blend at a higher compression ratio and the maximum load condition. The results ultimately suggest that the blend B20 + GNPs 60 mg/L + QPAN 80 mg/L could be successfully used in diesel engines with no engine modifications.