2026-09-23T14:03:31Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/90562022-01-13T07:54:36Zcom_1721.1_7582com_1721.1_7581col_1721.1_131023
Wai K. Cheng.
Waero, Rolf Rikard, 1974-
Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
Massachusetts Institute of Technology. Department of Mechanical Engineering
2005-08-24T19:18:26Z
2005-08-24T19:18:26Z
2000
2000
http://hdl.handle.net/1721.1/9056
46240688
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.
Includes bibliographical references (p. 37).
Residual gas tests were done on a 2.4 liter commercial engine to find a correlation for the effect on spark timing on residual gas fraction. The tests were done by sampling the charge mass during a non-firing cycle through a small hole into cylinder 4. The residual gas fraction was determined by measuring the CO2 content of the sample. The experiments were conducted for a variety of different spark timing and valve timing settings. Since the data was taken over a limited range, a physical basis for a correlation was developed. Following the approach used in a previous modeling effort, the residual gas fraction was modeled as the sum of two contributing factors: backflow from the exhaust port to the cylinder during valve overlap and gas trapped inside the cylinder at the time of intake valve open. Additionally, the phenomenon of choked backflow was introduced in the model. Based on the data, a correlation was developed that estimates the residual gas fraction as a function of: intake to exhaust pressure ratio (Pi/Pe), valve profile, engine speed, compression ratio, and spark timing.
by Rolf Rikard Waero.
S.M.
46 p.
2781068 bytes
2780828 bytes
application/pdf
application/pdf
eng
Massachusetts Institute of Technology
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http://dspace.mit.edu/handle/1721.1/7582
Mechanical Engineering.
The effect of spark timing on residual gas fraction
Thesis
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<Abstract>Residual gas tests were done on a 2.4 liter commercial engine to find a correlation for the effect on spark timing on residual gas fraction. The tests were done by sampling the charge mass during a non-firing cycle through a small hole into cylinder 4. The residual gas fraction was determined by measuring the CO2 content of the sample. The experiments were conducted for a variety of different spark timing and valve timing settings. Since the data was taken over a limited range, a physical basis for a correlation was developed. Following the approach used in a previous modeling effort, the residual gas fraction was modeled as the sum of two contributing factors: backflow from the exhaust port to the cylinder during valve overlap and gas trapped inside the cylinder at the time of intake valve open. Additionally, the phenomenon of choked backflow was introduced in the model. Based on the data, a correlation was developed that estimates the residual gas fraction as a function of: intake to exhaust pressure ratio (Pi/Pe), valve profile, engine speed, compression ratio, and spark timing.</Abstract>
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