Hydrogen‐Enriched Tri‐Fuel Combustion for Low‐Carbon Engines at Medium Engine Load: A Comprehensive CFD Analysis

ABSTRACT The global commitment to achieve net‐zero carbon emissions by 2050 has intensified the growing demand for sustainable and low‐carbon energy systems. Inspired by this vision, hydrogen (H 2 ) has attracted massive attention as a clean and highly reactive alternative fuel in this era of sustainable energy. Although H 2 ‐assisted dual‐fuel combustion has been widely investigated, very little research has been conducted on the H 2 ‐assisted tri‐fuel mode. Accordingly, a numerical analysis of this tri‐fuel concept is documented in this paper, where the effects of various hydrogen energy shares (HESs) on the performance, combustion, and emissions of a diesel‐CH 4 ‐H 2 fueled engine are investigated. The ANSYS Forte CFD software, linked with the ANSYS CHEMKIN tool, is employed for this numerical investigation. The results indicate that H 2 addition improves in‐cylinder fuel‐air mixing and, as a result, more uniform combustion occurs with lower emission levels. The in‐cylinder maximum pressure rises from 8.6 MPa for the pure diesel case to 10.3 MPa at the 60% HES case. This is an improvement of around 20%. The maximum in‐cylinder temperature also increases from 1437 K to 1649 K, which represents a 15% rise. The ignition timing also advances from about TDC to 2.3 CA bTDC. The maximum chemical heat release rate increases from 500 J/°CA for the pure diesel case to 1400 J/°CA in the 60% HES case. The 10%–90% heat‐release duration shortens by nearly half, and the indicated specific fuel consumption lowers by 26%. These findings suggest more rapid and complete combustion with the addition of H 2 . At this highest HES level, carbon monoxide and soot emissions measured at the exhaust valve opening reduce by almost 61% and 95%, respectively, compared to the pure diesel case. However, NO x emissions show a 31% rise in this case due to higher combustion temperatures. Unburned hydrocarbon and volatile organic compound emissions initially increase but decrease at higher HES levels.