This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Research on Improving Thermal Efficiency through Variable Super-High Expansion Ratio Cycle
Technical Paper
2010-01-0174
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
The compression ratio and expansion ratio are fundamental parameters that determine the thermal efficiency of an SI engine, and the potential of setting these ratios to arbitrary values was studied as a way of improving engine efficiency. First, the efficiency resulting from different compression and expansion ratios was calculated from a theoretical formula. As a result, it was verified that a 20% improvement in thermal efficiency could be expected by adopting a super-high expansion ratio of 20 or higher, which is an extremely large value for an SI engine, while keeping the compression ratio within a range that can ensure appropriate combustion. Subsequently, this research calculated the possibility of improving engine efficiency under a condition that constrains the swept volume to a constant value in consideration of practicability. The results indicated that in this case the expansion ratio is determined by load, and that ideal engine characteristics can be produced in which high efficiency is attained in practical load regions while producing maximum power under full load. Finally, based upon the above efficiency calculations, the thermal efficiency was verified using an actual engine in the load region with the greatest efficiency improvement effect. In tests, the evaluations utilized a high-efficiency commercially available compact 4-cylinder SI engine with a compression ratio of 13:1. By adopting a super-high expansion ratio, the test results showed an improvement in thermal efficiency of 80% with respect to the theoretically predicted value. In addition, issues related to the adoption of a super-high expansion ratio cycle (a reduction in the degree of constant volume and an increase in cooling loss) were analyzed theoretically and some strategies for minimizing these issues were studied. The overall results indicated that the adoption of the variable super-high expansion ratio cycle proposed in this paper is highly effective as a realistic means of improving the thermal efficiency of an engine.
Recommended Content
Topic
Citation
Akihisa, D. and Daisaku, S., "Research on Improving Thermal Efficiency through Variable Super-High Expansion Ratio Cycle," SAE Technical Paper 2010-01-0174, 2010, https://doi.org/10.4271/2010-01-0174.Also In
SI Combustion and Direct Injection SI Engine Technology, 2010
Number: SP-2278; Published: 2010-04-13
Number: SP-2278; Published: 2010-04-13
References
- Ueda, T. Hirose, T. Takaoka, T. “A high expansion ratio gasoline engine for the hybrid vehicle,” JSAE Symposium No.9802 32 39 1998
- Shiga, S. et al “Effect of the Application of Over-Expansion Cycle on the Improvement of Thermal efficiency in a Gasoline Engine,” JSAE Symposium No.17-04 13 19 2004
- Shimizu, T. et al “Characteristics of an Over-Expansion Cycle Gasoline Engine with Late Closing of Intake Valves by supercharging introduction,” Proceedings of the Japan Society of Mechanical Engineers Congress 2009 83 84 2008
- Heywood, J. B. “Internal Combustion Engine Fundamentals,” McGraw-Hill Book Co. 978-0070286375 161 186 1988
- Takanashi, J. Takazawa, M. Urata, Y. “A Study of High Compression Ratio and High Efficiency Gasoline Engine with VVT Mechanism,” Transactions of the Japan Society of Mechanical Engineers. B 74 746 2205 2212 2008
- Roberts, M. “Benefits and Challenges of Variable Compression Ratio (VCR),” SAE Technical Paper 2003-01-0398 2003
- Schwaderlapp, M. Habermann, K. Yapici, K.I. “Variable Compression Ratio - A Design Solution for Fuel Economy Concepts,” SAE Technical Paper 2002-01-1103 2002
- Rabhi, V. Beroff, J. Dionnet, F. “Study of a Gear-Based Variable Compression Ratio Engine,” SAE Paper 2004-01-2931 2004
- Tanaka, Y. Hiyoshi, R. Takemura, S. Ikeda, Y. et al. “A Study of a Compression Ratio Control Mechanism for a Multiple-Link Variable Compression Ratio Engine,” SAE Technical Paper 2007-01-3547 2007
- Nagao, F. “Internal Combustion Engine Lecture,” Yokendo Print Co., Ltd 978-4842501789