Experimental investigation and parametric modeling of the effect of alcohol addition on the performance and emissions characteristics of a diesel engine fueled with biodiesel-diesel-hydrogen fuel mixtures

•Effects of adding varying percentages of alcohol in biodiesel-diesel mixture on engine performance and emission using RSM approach.•Impacts of replacing hydrogen with diesel in the fuel mixture.•Combinations of two-zone simulation and Random Forest model to assess performance and emissions of the engine. This study aims to evaluate the impact of various blends of diesel, biodiesel, and alcohols (n-butanol or ethanol) as triple fuels, along with the effects of replacing hydrogen (H2) with diesel in the fuel mixture, on the performance and emissions of a single-cylinder diesel engine. The results obtained using the Response Surface Methodology (RSM) revealed that incorporating alcohol into the fuel mixture reduced brake power by up to 20 %. Additionally, alcohol addiction increased brake-specific fuel consumption (BSFC) by up to 8 %. Overall, including alcohol raised carbon monoxide (CO) emissions by up to 28 %, reducing carbon dioxide (CO2) emissions by 16 % to 19 %. Furthermore, adding alcohol to the diesel–biodiesel blend lowered nitrogen oxide (NOx) emissions by 18% compared to the diesel–biodiesel mixture alone. In the study’s second phase, parametric analyses were conducted using a two-zone simulation model and a random forest machine learning model to examine the effects of replacing diesel with hydrogen in the fuel mixture on performance and emission characteristics. The findings demonstrated that increasing the hydrogen proportion in the mixture enhanced power output and thermal efficiency. Conversely, increasing n-butanol and ethanol ratios decreased power output and thermal efficiency. Specific fuel consumption (SFC) increased with a reduction in the hydrogen ratio and an increase in the n-butanol-ethanol ratios. Nitric oxide (NO) emissions rose with higher hydrogen and lower n-butanol- ethanol ratios. CO2 emissions decreased as the hydrogen ratio increased but increased with higher biodiesel content. While EtOH and n-butanol blends produced more CO2 than hydrogen, their CO2 emissions were still lower than diesel ones. Due to its higher calorific value, the minimum SFC and CO2 emissions were observed with 100% hydrogen. It was also noted that power, brake thermal efficiency (BTE), SFC, and CO2 emissions decreased, while NO emissions increased by 23 %, 11 %, 58 %, 100 %, and 190 %, respectively, when hydrogen was replaced with diesel in the fuel mixture. Comparing the two alcohols in the biodiesel-diesel mixture, n-butanol demonstrated a more favo