Effect of the Piston Bowl Geometry on In-Cylinder Flow and Combustion in a Hydrogen Internal Combustion Engine: A CFD Study

초록

This study investigates the combustion characteristics associated with three distinct piston geometries under 2000 RPM full-load conditions (fuel injection quantity: 62 mg). To optimize engine performance, the compression ratio was fixed at 11.0 for all cases. Piston designs include a squish-maximized Type-C, a tumble-enhanced Type-B with minimized squish area, and a baseline Type-A configuration. Simulations were performed across two continuous cycles, with analysis conducted on the second cycle. Results reveal that Type-B achieved the most favorable performance, including the highest gross indicated mean effective pressure (IMEP) of 1.92 MPa, the earliest combustion phasing (CA10 = 0.5 degrees aTDC), and the shortest combustion duration of 23.0 degrees CA. Type-B also recorded the highest peak heat release rate (381 J/CA) and turbulence kinetic energy (29.8 m2/s2) near ignition, promoting rapid and stable flame propagation. In contrast, Type-C exhibited delayed combustion (CA10 = 4.5 degrees aTDC), the longest duration (32.5 degrees CA), and the lowest IMEP (1.81 MPa), despite demonstrating improved knock resistance. The IMEP of Type-C was 6% lower than that of Type-B. These findings highlight the critical influence of piston crown design on in-cylinder flow development and hydrogen combustion performance.

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