The present investigation uses a blend of Nigella sativa biodiesel, diesel, n-butanol, and graphene oxide nanoparticles to enhance the performance, combustion and symmetric characteristics and to reduce the emissions from the diesel engine of a modified common rail direct injection (CRDI). A symmetric toroidal-type combustion chamber and a six-hole solenoid fuel injector were used in the current investigation. The research aimed to study the effect of two fuel additives, n-butanol and synthesized asymmetric graphene oxide nanoparticles, in improving the fuel properties of Nigella sativa biodiesel (NSME25). The concentration of n-butanol (10%) was kept constant, and asymmetric graphene oxide nano-additive and sodium dodecyl benzene sulphonate (SDBS) surfactant were added to n-butanol and NSME25 in the form of nanofluid in varying proportions. The nanofluids were prepared using a probe sonication process to prevent nanoparticles from agglomerating in the base fluid. The process was repeated for biodiesel, n-butanol and nanofluid, and four different stable and symmetric nanofuel mixtures were prepared by varying the graphene oxide (30, 60, 90 and 120 ppm). The nanofuel blend NSME25B10GO90 displayed an enhancement in the brake thermal efficiency (BTE) and a reduction in brake-specific fuel consumption (BSFC) at maximum load due to high catalytic activity and the enhanced microexplosion phenomenon developed by graphene oxide nanoparticles. The heat release rate (HRR), in-cylinder temperature increased, while exhaust gas temperature (EGT) decreased. Smoke, hydrocarbon (HC), carbon monoxide (CO2) and carbon monoxide (CO) emissions also fell, in a trade-off with marginally increased NOx, for all nanofuel blends, compared with Nigella sativa biodiesel. The results obtained indicates that 90 ppm of graphene oxide nanoparticles and 10% n-butanol in Nigella sativa biodiesel are comparable with diesel fuel.

Research on and use of biodiesels for engines is growing continuously in the present era. Compression ignition (CI) engine performance for biodiesels of blends B20 from Acid oil, Mahua oil, and Castor oil is experimentally investigated. The engine performance analysis in the form of brake-specific fuel consumption, brakespecific energy consumption, brake thermal efficiency (BTE), exhaust gas temperature (EGT), and air fuel ratio are compared with diesel as base fuel. Emission characteristics like CO, CO 2 , NOx, and opacity are comparatively studied in detail for the considered biodiesels. The entire study is compared with the performance of engine when pure diesel is chosen as fuel. From the complete analysis it was observed that the BTE was higher for Acid oil and Mahua oil among the biodiesels used. And regarding CO emissions, Mahua oil showed lower effect than other biodiesels. Upto 6% increase in EGT of Mahua oil was obtained at no load and for other loads the percent reduced. For all the biodiesels the % enhancement in Co, CO 2 , and NOx was more than 60% at highest load compared with diesel.

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An experimental study on optimum spacing between grooved tubes is reported in this paper. Two grooved tubes having pitch of 10 mm and 15 mm and a plain tube were considered for the heat transfer analysis. The spacing between two tubes with same pitch was varied from 10 mm to 35 mm with a step size of 5 mm. Velocity of air flowing over the tube surfaces was changed from 0.4 m/s to 1 m/s using a blower fan. Based on Nusselt number (Nu) the optimum spacing between the tubes was decided. The optimum spacing between grooved tubes of pitch 10 mm and 2