Potential of Negative Valve Overlap for Part Load Efficiency Improvement in Gasoline Engines
Name
2018-01-0377_Final.pdf
Description
Pre-print of main article
Size
2.35 MB
Format
Adobe PDF
Checksum (MD5)
90784668d161e9f4bbd25b48ec7ac8ea
Author(s)
Cheng, Wai K
Rodriguez, Juan Felipe
Date Issued
April 2018
Journal
SAE Technical Papers
Publisher
SAE International
Citation
Rodriguez, J. Felipe, and Wai Cheng. "Potential of Negative Valve Overlap for Part Load Efficiency Improvement in Gasoline Engines." WCX: SAE World Congress Experience, 10-12 April, 2018, Detroit, Michigan, SAE International, 2018.
Version
Author's final manuscript
Abstract
This paper reports on the potential of negative valve overlap for improving the net indicated thermal efficiency of gasoline engines during part load. Three fixed fuel flow rates, resulting in indicated mean effective pressures of up to 6 bar, were investigated. At low load, negative valve overlap (NVO) significantly reduces the pumping loses during the gas exchange loop, achieving up to 7% improvement in indicated efficiency compared to the baseline. Similar efficiency improvements are achieved by positive valve overlap (PVO), with the disadvantage of worse combustion stability from a higher residual gas fraction. As the load increases, achieving the wide-open throttle limit, the benefits of NVO for reducing the pumping losses diminish, while the blow-down losses from early exhaust valve opening increase.
However, a symmetric NVO strategy combined with a shorter exhaust duration has a higher potential for reduction in part-load fuel consumption, as the exhaust valve opening timing can be optimized to minimize the blow-down losses.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Terms of Use
Creative Commons Attribution-Noncommercial-Share Alike
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.4271/2018-01-0377
