A thermodynamic approach to energy, exergy, exergoeconomic, enviroeconomic, and sustainability assessments involving an VCR diesel engine employing third-generation biodiesel with TiO2 NPs and n-heptane

[Display omitted] •Analyzing the properties of the third-generation biodiesel using n-heptane and TiO2 nanoparticles.•The SI was determined to ascertain the most effective fuel option.•A detailed analysis is conducted on several fuel samples to assess their energy, exergy, exergoeconomics, enviroeconomic, and SI aspects.•The addition of n-heptane and NPs in the diesel–biodiesel mix resulted in an enhancement in thermal and exergy efficiency.•Increasing the nanoparticle proportion in fuel blends leads to a reduction in exergy losses. Fossil fuels serve as the predominant source of energy for many sectors globally. Still, the stocks of these resources are limited and declining, and usage releases harmful gasses, contributing to both climate change and negative impacts on human health. Hence, it is crucial to ascertain alternate fuels or formulate fuel additives that may diminish fuel consumption and the discharge of pollutants. Diesel engines run on biofuel, and their performance has dropped, although it can potentially be improved with the use of different additives. The objective of this research is to experimentally investigate azolla pinnata algal fuel characteristics as a sustainable alternative fuel added with titanium dioxide nanoparticles (TiO2 NPs-10, 40, and 80 ppm) and higher alcohols (n-heptane-10 and 15 % by vol.). Energy, exergy, exergoeconomic, enviroeconomic, entropy generation, and sustainability index (SI) analyses were conducted on a VCR diesel engine operating at varying loads (25, 50, 75 & 100 % load) and constant speed (1500 rpm) with different test fuels in varying proportions containing diesel-algal biodiesel-n-heptane-TiO2 NPs fuel blends. D80A10H10TNP40 (diesel80% + biodiesel10% + n-heptane10% + TiO2 NPs 40 ppm) outperformed in all the condition with maximum energy and exergy efficiency of 27.26 % and 29.45 % at full load, respectively. The highest SI and lowest relative cost difference with minimum entropy generation rate are obtained for D80A10H10TNP40 with values of 1.42, 3.05, and 0.0214, respectively. Increasing fuel consumption and engine load raise all environmental effect rates while the exergy unit rate decreases. Although NPs-added fuels have high unit prices, these are preferred biofuels because of exergoeconomic and sustainability aspects because of their substantial exergy efficiency. After considering all of the fuels evaluated, it is clear that D80A10H10TNP40 is the best option.