Non-linear and multi-domain modelling of a free piston engine with linear electric machine

• Published in: Energy conversion and management. X Vol. 20; p. 100413
• Main Authors: Brosnan, Patrick, Tian, Guohong, Montanaro, Umberto, Cockerill, Sam
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-10-2023; Elsevier
• Subjects: Biomass Hydrous Ethanol Fuel; Free-Piston Engine (FPE); Homogeneous Charge Compression Ignition (HCCI); Machine Learning (ML); Multi-Domain Modelling; Permanent Magnet Linear Synchronous Machine (PMLSM); Machine Learning (ML); Biomass Hydrous Ethanol Fuel; Homogeneous Charge Compression Ignition (HCCI); Free-Piston Engine (FPE); Permanent Magnet Linear Synchronous Machine (PMLSM); Multi-Domain Modelling
• ISSN: 2590-1745; 2590-1745
• DOI: 10.1016/j.ecmx.2023.100413

•A non-linear and multi-domain description of the FPE is presented.•The dynamics of the FPE during its motoring and generating phases are presented.•A surrogate chemical-kinetics description of the in-cylinder process is presented.•Hydrous ethanol auto-ignition combustion is considered and presented.•Validation of the proposed modelling approach is conducted and presented.
In the current technological era, with the rapid advances in low-carbon power generation solutions, there has been renewed interest in the Free Piston Engine (FPE) as a viable thermal propulsion technology. However, describing and capturing the intrinsic non-linear dynamics of the FPE is computationally challenging and, understandably, is generally characterised by a simplified linear description, which may inherently omit the dominant dynamics.
Consequently, this study considers the non-linear and multi-directional nature of the coupled translation loads during motoring and power generation. Thus, presenting a non-linear and multi-domain description of the FPE. The proposed model was implemented in an opposed-piston free-piston engine configuration and validated during motoring and generating against experimental data captured from a prototype with identical parameters. The simulation results strongly correlate to the experimental data with similar translator displacement, in-cylinder pressure and bounce chamber pressure traces. Furthermore, the study demonstrated that the proposed modelling approach captured the dominant dynamics of the FPE and proved satisfactory accuracy and performance. In addition to validating the proposed modelling approach, this paper concludes with a simulation study that demonstrates the embedding of a novel surrogate Chemical Kinetics (CK) description of the hydrous ethanol auto-ignition process and the resultant influence on the FPE dynamics, most importantly, on gaseous emission formation.
Therefore, this paper aims to extend the current knowledge in this novel and emerging technology by considering the characteristic non-linearity and multi-directional nature of its coupling with multi-physical domains such as mechanical, chemical and electrical.