Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
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| Other Authors: | |
| Format: | Thesis |
| Language: | eng |
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Massachusetts Institute of Technology
2006
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| Online Access: | http://hdl.handle.net/1721.1/32369 |
| _version_ | 1811093252606001152 |
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| author | Gerty, Michael D |
| author2 | John B. Heywood. |
| author_facet | John B. Heywood. Gerty, Michael D |
| author_sort | Gerty, Michael D |
| collection | MIT |
| description | Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. |
| first_indexed | 2024-09-23T15:42:17Z |
| format | Thesis |
| id | mit-1721.1/32369 |
| institution | Massachusetts Institute of Technology |
| language | eng |
| last_indexed | 2024-09-23T15:42:17Z |
| publishDate | 2006 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/323692019-04-10T15:09:56Z Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits Gerty, Michael D John B. Heywood. Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Mechanical Engineering. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. Includes bibliographical references (p. 133-135). A set of experiments was performed to investigate the effects of air-fuel ratio, inlet boost pressure, hydrogen rich fuel reformate, and compression ratio on engine knock behavior. For each condition the effect of spark timing on torque output was measured. Knock limited spark advance was then found for a range of octane number (ON) for each of three fuel types; primary reference fuels (PRFs), toluene reference fuels (TRFs), and test gasolines. A new combustion phasing parameter based on the timing of 50% mass fraction burned, ternled "combustion retard", was found to correlate well to engine performance. Increasing air- fuel ratio increases the combustion retard required to just avoid knock for PRFs and has little effect for TRFs. Combustion retard also increases more with inlet pressure and decreases more with reformate addition for PRFs than for TRFs. Both fuel types responded similarly to increased compression ratio. The trends for gasoline are about halfway between PRFs and TRFs. Experiments were also performed to determine the response of mid-load indicated efficiency to air-fuel ratio, load, and compression ratio. At a compression ratio of 9.8:1, relative net efficiency improvement is about 2.5% per unit compression ratio. Efficiency peaks at about 14:1 with a maximum benefit of 6-7%. Detailed chemical kinetics were combined with a cylinder pressure based end-gas modeling methodology to successfully predicted the response of PRFs to compression ratio and air-fuel ratio, and the response of TRFs to boost. The difference between the response of PRFs and TRFs to air-fuel ratio was also captured. (cont.) Constant volume chemistry modeling found that hydrogen slows alkane autoignition reactions by consuming hydroxy radicals in the end gas. Reforming 30% of the fuel entering an engine decreases the required fuel quality 10 ON or more, which would allow increased compression ratio or increased turbocharging without increasing combustion retard. A simplified analysis indicates that increasing compression ratio and downsizing the engine to maintain constant maximum torque would increase fuel efficiency by about 9%. Turbocharging and downsizing would increase fuel efficiency by about 16%. by Michael D. Gerty. S.M. 2006-03-29T18:38:14Z 2006-03-29T18:38:14Z 2005 2005 Thesis http://hdl.handle.net/1721.1/32369 61515970 eng M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 173 p. 8229807 bytes 8239911 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Mechanical Engineering. Gerty, Michael D Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits |
| title | Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits |
| title_full | Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits |
| title_fullStr | Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits |
| title_full_unstemmed | Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits |
| title_short | Effects of operating conditions, compression ratio, and gasoline reformate on SI engine knock limits |
| title_sort | effects of operating conditions compression ratio and gasoline reformate on si engine knock limits |
| topic | Mechanical Engineering. |
| url | http://hdl.handle.net/1721.1/32369 |
| work_keys_str_mv | AT gertymichaeld effectsofoperatingconditionscompressionratioandgasolinereformateonsiengineknocklimits |