Numerical analysis of ammonia HCCI combustion in a free piston engine through trajectory-based combustion control

Chen Zhang, Biaowu Lu, Jinlong Wang, Lei Zhu, Jin Xiao, Zongxuan Sun, Zhen Huang

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Ammonia is a promising carbon–neutral fuel, able to power heavy-duty vehicles, non-road machineries and ocean ships with zero CO2 emission. However, practical challenges still exist when applying ammonia in traditional internal combustion engines (ICEs) due to its high ignition energy, slow flame propagation and significant NOx emissions. Free piston engine (FPE) is a flexible alternative to ICE whose piston can move freely without the constraints of crankshaft. Therefore, its piston trajectory can be leveraged as a new control means to facilitate ammonia combustion. In this paper, a numerical analysis investigating ammonia HCCI combustion in FPE was presented. A physical-based model was developed at first, including a unique trajectory synthesizing mechanism and a detailed reaction mechanism of ammonia oxidation. Various asymmetric piston trajectories were then employed into the model and the simulated HCCI combustion were analyzed through six characteristics, namely indicated thermal efficiency, location of peak pressure, exhaust gas temperature, combustion duration, ignition delay, and NOx emissions. This investigation not only determines the best compression ratio (CR = 25) for ammonia ignition, but also shape the optimal piston trajectory (symmetric trajectory with Ω = 0.5) for ammonia HCCI combustion to enhance thermal efficiency and reduce NOx emission simultaneously.

Original languageEnglish (US)
Article number127634
StatePublished - Jun 1 2023
Externally publishedYes

Bibliographical note

Funding Information:
The authors would like to acknowledge the financial support from Shanghai Jiao Tong University through the “Double World-class” research grant project number: WH220445004.

Publisher Copyright:
© 2023 Elsevier Ltd


  • Ammonia
  • Carbon–neutral fuel
  • Free piston engine
  • HCCI
  • Numerical analysis
  • Trajectory-based combustion control


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