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TDC Offset Estimation from Motored Cylinder Pressure Data based on Heat Release Shaping

Tunestål, Per LU (2011) In Oil & Gas Science and Technology 66(4). p.705-716
Abstract (Swedish)
Abstract in Undetermined

Finding the correct Top Dead Center (TDC) offset for an internal combustion engine is harder than it seems. This study introduces a novel method to find the TDC offset based on the simple assumption that the heat loss power through the combustion chamber walls is constant for motored cycles in a narrow Crank Angle interval around TDC. The proposed method uses nonlinear least squares optimization to find the combination of specific heat ratio and TDC offset that makes the heat loss power as constant as possible. An important subproblem is to determine the peak pressure location with high accuracy. Fitting a third order Fourier series to the motored cylinder pressure allows the pressure maximum to be... (More)
Abstract in Undetermined

Finding the correct Top Dead Center (TDC) offset for an internal combustion engine is harder than it seems. This study introduces a novel method to find the TDC offset based on the simple assumption that the heat loss power through the combustion chamber walls is constant for motored cycles in a narrow Crank Angle interval around TDC. The proposed method uses nonlinear least squares optimization to find the combination of specific heat ratio and TDC offset that makes the heat loss power as constant as possible. An important subproblem is to determine the peak pressure location with high accuracy. Fitting a third order Fourier series to the motored cylinder pressure allows the pressure maximum to be estimated with a standard deviation of 0.005° Crank Angle (CA) and it can also be used instead of the measured pressure to reduce the uncertainty of the TDC estimate by approximately 50%. The standard deviation of a single-cycle TDC estimate is approximately 0.025° CA when using a crank resolution of 0.2° CA for the measurements. The bias of the TDC estimate is in the 0-0.02° CA range both when comparing to measurements with a TDC sensor and with simulated motored cycles. The method can be used both for calibration and on-board diagnostics purposes e.g. during cranking, fuel cut-off or engine switch-off. The third order Fourier series fit comes with a significant computational penalty but since it is only applied very intermittently this does not have to be a serious issue. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
combustion engine, cylinder pressure, crank angle, top dead center, least squares estimation, optimization
in
Oil & Gas Science and Technology
volume
66
issue
4
pages
705 - 716
publisher
IFP Energies nouvelles
external identifiers
  • wos:000297969200014
  • scopus:80655147977
ISSN
1294-4475
DOI
10.2516/ogst/2011144
project
Competence Centre for Combustion Processes
language
English
LU publication?
yes
id
4278d016-f431-4ada-a86b-1266468474f9 (old id 2370927)
date added to LUP
2012-03-13 16:15:33
date last changed
2017-10-29 04:03:53
@article{4278d016-f431-4ada-a86b-1266468474f9,
  abstract     = {<b>Abstract in Undetermined</b><br/><br>
Finding the correct Top Dead Center (TDC) offset for an internal combustion engine is harder than it seems. This study introduces a novel method to find the TDC offset based on the simple assumption that the heat loss power through the combustion chamber walls is constant for motored cycles in a narrow Crank Angle interval around TDC. The proposed method uses nonlinear least squares optimization to find the combination of specific heat ratio and TDC offset that makes the heat loss power as constant as possible. An important subproblem is to determine the peak pressure location with high accuracy. Fitting a third order Fourier series to the motored cylinder pressure allows the pressure maximum to be estimated with a standard deviation of 0.005° Crank Angle (CA) and it can also be used instead of the measured pressure to reduce the uncertainty of the TDC estimate by approximately 50%. The standard deviation of a single-cycle TDC estimate is approximately 0.025° CA when using a crank resolution of 0.2° CA for the measurements. The bias of the TDC estimate is in the 0-0.02° CA range both when comparing to measurements with a TDC sensor and with simulated motored cycles. The method can be used both for calibration and on-board diagnostics purposes e.g. during cranking, fuel cut-off or engine switch-off. The third order Fourier series fit comes with a significant computational penalty but since it is only applied very intermittently this does not have to be a serious issue.},
  author       = {Tunestål, Per},
  issn         = {1294-4475},
  keyword      = {combustion engine,cylinder pressure,crank angle,top dead center,least squares estimation,optimization},
  language     = {eng},
  number       = {4},
  pages        = {705--716},
  publisher    = {IFP Energies nouvelles},
  series       = {Oil & Gas Science and Technology},
  title        = {TDC Offset Estimation from Motored Cylinder Pressure Data based on Heat Release Shaping},
  url          = {http://dx.doi.org/10.2516/ogst/2011144},
  volume       = {66},
  year         = {2011},
}