Experimental and statistical investigation of MgO ‐assisted microalgae biodiesel–hydrogen dual‐fuel combustion in an RCCI engine

Abstract

Abstract In Reactivity‐Controlled Compression Ignition (RCCI) operation, hydrogen was inducted through the intake manifold as a low‐reactivity fuel (LRF), whereas microalgae biodiesel‐diesel blends enriched with magnesium oxide (MgO) nanoparticles were directly injected into the combustion chamber as high‐reactivity fuel (HRF). This study explored a unique tri‐fuel combination consisting of microalgae biodiesel, magnesium oxide nanoparticles (25 and 50 ppm), and hydrogen (5 and 10 L/min). The experimental investigation was conducted at varying loads with different blends to evaluate engine performance, combustion characteristics, and emission characteristics. The results showed that the blend B20D80 + 50 ppm MgO + 10 lpm H 2 achieved the highest brake thermal efficiency, increasing from 29.5% to 33.8%, represented as 14.58% increase, along with a decrease in brake‐specific energy consumption from 6373 kJ/kWh to 6027 kJ/kWh, corresponding to a 5.43% reduction compared with diesel. The improved combustion performance can be attributed to the enhanced oxidation of biodiesel, the catalytic activity of MgO, and the high flame speed of hydrogen, leading to notable reductions in hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO 2 ), and soot emissions. However, NO x emissions increased due to the higher in‐cylinder temperatures. Combustion analysis further indicated increased in‐cylinder peak pressure and heat release rate, from 65 to 75 bar and 63 to 74 J/°CA, respectively, indicating a faster and more efficient combustion process under hydrogen‐assisted RCCI operation. Overall, the proposed tri‐fuel approach demonstrated enhanced engine efficiency, albeit with a trade‐off in terms of increased NO x emissions and potential long‐term engine durability concerns.