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

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.