Lookup NU author(s): Dr Boru Jia,
Dr Andrew Smallbone,
Professor Tony Roskilly
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Free-piston engines (FPEs) are known to have a greater thermal efficiency (40-50%) than an equivalent and more conventional four-stroke reciprocating engines (30-40%). Modern FPEs are proposed for the generation of electric and hydraulic power, with a potential application in hybrid electric vehicles. The numerous FPE configurations considered to date have almost exclusively operated using a two-stroke thermodynamic cycle to improve the thermal efficiency, however it is well known that the application of two-stoke cycles can be limited by noise and exhaust gas emissions constraints. In this article, a numerical model is used to investigate the techno-feasibility of operating Newcastle University's FPE prototype using a two- or four-stroke thermodynamic cycle. If operated as a four-stroke cycle, the linear generator must be used as both a motor and a generator resulting in a more irregular piston motion compared to corresponding operating in a two-stroke cycle. In four-stroke cycles, almost half the indicated power is consumed in overcoming the pumping losses of the motoring process. Whilst the heat release process is appears to be closer to a constant volume process when operated on two-stroke engine cycle, the peak cylinder pressure and compression ratio proved lower. In addition, a narrower power range is reported for a four-stroke cycle despite a corresponding higher thermal efficiency. (C) 2016 Elsevier Ltd. All rights reserved.
Author(s): Jia BR, Smallbone A, Zuo ZX, Feng HH, Roskilly AP
Publication type: Article
Publication status: Published
Journal: Energy Conversion and Management
Print publication date: 01/03/2016
Online publication date: 08/01/2016
Acceptance date: 27/12/2015
ISSN (print): 0196-8904
ISSN (electronic): 1879-2227
Publisher: Elsevier Ltd
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