| Effect of the Piston Bowl Geometry on In-Cylinder Flow and Combustion in a Hydrogen Internal Combustion Engine: A CFD Study |
| Seongsu Kim1, Wookeun Choi1, Myungjik Bae2, Junghwan Kim3 |
1Department of Energy Systems Engineering, Chung-Ang University, Seoul, 06974, Korea
2Advanced Engine Development Team, HD Hyundai Infracore, 489, Injung-ro, Dong-gu, Incheon, 22502, Korea
3School of Energy Systems Engineering, Chung-Ang University, Seoul, 06974, Korea |
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Received: May 13, 2025; Revised: June 5, 2025 Accepted: August 16, 2025. Published online: September 22, 2025. |
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| ABSTRACT |
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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° aTDC), and the shortest combustion duration of 23.0° 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° aTDC), the longest duration (32.5° 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. |
| Key Words:
Piston geometry · Squish flow · Tumble flow · Hydrogen engine · Combustion analysis · TKE · Knock suppression |
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Corresponding Author.
Junghwan Kim , Email. 
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