TY - GEN
T1 - Effect of the Number of Injection Holes on the In-Cylinder Mixing and Performance of Low-Load Methanol Direct Injection Free Piston Engines
AU - Hu, Xiaoxu
AU - Feng, Huihua
AU - Wang, Zihan
AU - Jia, Boru
N1 - Publisher Copyright:
© The Author(s) 2026.
PY - 2026
Y1 - 2026
N2 - In this study, the effects of the number of injection holes on the in-cylinder mixing characteristics and combustion performance of a low-load methanol direct-injection free-piston engine generator (FPEG) were systematically investigated through a combination of numerical simulation and experiment. The results show that the increase in the number of injection holes significantly optimizes the in-cylinder equivalence ratio distribution, and the percentage of the extreme equivalence ratio region is reduced dramatically; at the same time, the increase in the number of holes shortens the spraying, the rise in the number of nozzles shortens the spraying time, prolongs the premixing time of oil and gas, and improves the mixing uniformity. In terms of combustion performance, the three-hole nozzle exhibits the best overall performance, with a 19% increase in peak cylinder pressure compared to the dual-hole nozzle, an indicated thermal efficiency above 40%, and the shortest combustion duration. In contrast, the six-hole nozzle produces an excessively dispersed spray, resulting in a dilute mixture in the vicinity of the spark plug, prolonged ignition delay, and lag in the cylinder pressure phase.
AB - In this study, the effects of the number of injection holes on the in-cylinder mixing characteristics and combustion performance of a low-load methanol direct-injection free-piston engine generator (FPEG) were systematically investigated through a combination of numerical simulation and experiment. The results show that the increase in the number of injection holes significantly optimizes the in-cylinder equivalence ratio distribution, and the percentage of the extreme equivalence ratio region is reduced dramatically; at the same time, the increase in the number of holes shortens the spraying, the rise in the number of nozzles shortens the spraying time, prolongs the premixing time of oil and gas, and improves the mixing uniformity. In terms of combustion performance, the three-hole nozzle exhibits the best overall performance, with a 19% increase in peak cylinder pressure compared to the dual-hole nozzle, an indicated thermal efficiency above 40%, and the shortest combustion duration. In contrast, the six-hole nozzle produces an excessively dispersed spray, resulting in a dilute mixture in the vicinity of the spark plug, prolonged ignition delay, and lag in the cylinder pressure phase.
KW - combustion performance
KW - free piston engine generator
KW - injection parameters
KW - methanol direct injection
KW - mixing equivalence ratio
UR - https://www.scopus.com/pages/publications/105035299336
U2 - 10.1007/978-981-95-6911-3_60
DO - 10.1007/978-981-95-6911-3_60
M3 - Conference contribution
AN - SCOPUS:105035299336
SN - 9789819569106
T3 - Lecture Notes in Mechanical Engineering
SP - 596
EP - 606
BT - The 10th International Conference on Advances in Construction Machinery and Vehicle Engineering - ICACMVE 2025
A2 - Halgamuge, Saman
A2 - Ma, Lifeng
A2 - Liang, Weiguo
A2 - Bian, Yongming
PB - Springer Science and Business Media Deutschland GmbH
T2 - 10th International Conference on Advances in Construction Machinery and Vehicle Engineering, ICACMVE 2025
Y2 - 22 August 2025 through 25 August 2025
ER -