Evaluating ignition improvers on performance and emissions of Calophyllum inophyllum biodiesel in turbocharged diesel engines

•Di-tertiary-butyl peroxide, n-pentanol, and n-butanol evaluated as potential ignition improver additives.•Analysis of the impact of biodiesel blends containing ignition improvers on engine performance.•BD10+DTBP20 blend exhibits physicochemical properties closely matching those of diesel fuel.•BD20+DTBP20 shows increased BSFC, reduced BTE, and lower EGT compared to diesel fuel.•Significant enhancements in combustion efficiency and emission reductions observed with BD20+DTBP20. The rising demand for eco-friendly fuels has sparked interest in biodiesel as a sustainable alternative to conventional diesel. This study evaluates the effects of various additives—di-tertiary-butyl peroxide (DTBP), n-pentanol, and n-butanol—blended with Calophyllum inophyllum biodiesel-diesel blends on diesel engine performance, combustion, and emissions. The engine's compression ratio, injection timing, injector opening pressure, and speed were kept constant. DTBP proved to offer the best balance between performance and emissions. The BD20+DTBP20 blend showed minor differences from regular diesel in heating value, density, and viscosity, with reductions in brake thermal efficiency by 2.83 % and a 9.67 % increase in brake-specific fuel consumption at maximum load. Emission analysis revealed reductions of 58.52 % in CO, 41.17 % in HC, and 33.89 % in smoke, with only a slight increase in NOx by 1.97 %. Combustion analysis indicated a 68.65 % longer ignition delay, with reductions in in-cylinder pressure by 5.47 % and heat release rate by 9.07 %. These findings suggest that the BD20+DTBP20 blend meets emission standards and performs comparably to diesel, offering immediate applicability for existing diesel engines. This study supports global sustainability efforts by reducing dependence on fossil fuels and mitigating environmental pollution, contributing to international goals like the UN SDGs and stringent emissions standards such as Euro VI and BS VI. The research provides critical insights for future biodiesel development with ignition improvers, promoting sustainable energy transitions in the transportation and industrial sectors.