Investigation on the Potential of High Efficiency for Internal Combustion Engines

Haifeng Liu, Junsheng Ma, Laihui Tong, Guixiang Ma, Zunqing Zheng and Mingfa Yao
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Haifeng Liu: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Junsheng Ma: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Laihui Tong: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Guixiang Ma: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Zunqing Zheng: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Mingfa Yao: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China

Energies, 2018, vol. 11, issue 3, 1-20

Abstract: The current brake thermal efficiency of advanced internal combustion engines is limited to 50%, and how to further improve the efficiency is a challenge. In this study, a theoretical investigation on engine thermal efficiency was carried out using one-dimension simulations based on the first law of thermodynamics. The energy balance was evaluated by varying parameters such as compression ratio (CR); heat transfer coefficient; intake charge properties; and combustion phasing etc.—their influences on the efficiency limits were demonstrated. Results show that for a given heat transfer coefficient, an optimal CR exists to obtain the peak efficiency. The optimal CR decreases with the increase of heat transfer coefficient, and high CR with a low heat-transfer coefficient can achieve a significantly high efficiency. A higher density and specific heat ratio of intake charge, as well as a shorter combustion duration with a proper CA50 (crank angle at 50% of total heat release), can increase efficiency significantly. Methanol shows an excellent ability in decreasing the peak in-cylinder temperature; and the peak indicated efficiency is relatively higher than other tested fuels. The displacement has few effects on the indicated efficiency, while it shows a strong effect on the energy distribution between heat transfer and exhaust energy. All these strategies with high CR result in high in-cylinder pressure and temperature; which means a breakthrough of material is needed in the future.

Keywords: engine; thermal efficiency; heat transfer; first law of thermodynamics; losses; high compression ratio (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (13)

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