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TECHNICAL PAPERS: Internal Combustion Engines

A New Criterion to Determine the Start of Combustion in Diesel Engines

[+] Author and Article Information
Tomaž Katrašnik

Faculty of Mechanical Engineering,  University of Ljubljana, Aškerčeva 6, SI-1000 Ljubljana, Sloveniatomaz.katrasnik@fs.uni-lj.si

Ferdinand Trenc, Samuel Rodman Oprešnik

Faculty of Mechanical Engineering,  University of Ljubljana, Aškerčeva 6, SI-1000 Ljubljana, Slovenia

J. Eng. Gas Turbines Power 128(4), 928-933 (Sep 26, 2005) (6 pages) doi:10.1115/1.2179471 History: Received January 14, 2005; Revised September 26, 2005

A new criterion for the determination of the start of combustion (SOC) from the diesel engine in-cylinder pressure diagram was developed. It is defined as the maximum of the third-order derivative of the cylinder pressure with respect to the crank angle. This criterion declares SOC more precisely than other previously published criteria based on pressure diagnostics. This fact was proven analytically and was discernable from the analysis of the experimental data. Besides its accuracy it is also robust enough to allow automatic evaluation of the SOC during processing of the pressure data for a large number of cycles. By applying the first law of thermodynamics analysis to the engine cylinder it was discovered that the third-order derivative of the in-cylinder pressure with respect to the crank angle is the most suitable criterion for determination of the SOC from the in-cylinder pressure diagram. Subsequently, the criterion was validated through experimental data analysis of the in-cylinder pressure diagrams for various engine speeds and loads. In order to evaluate the rate of heat release (ROHR), which formed the base for the experimental validation, in-cylinder pressure diagrams were processed with a computer code based on the first law of thermodynamics. The cylinder pressure was measured with an advanced piezoelectric sensor at the resolution 0.1 deg CA. Top dead center was determined with the capacitive top dead center sensor. Due to the analytic foundation of the developed method and its validation through highly accurate experimental data it can be concluded that new criterion is credible for the determination of the SOC.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

ROHR with indicated maximum values of its derivatives

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Figure 2

In-cylinder pressure at 1200rpm, 0.2MPa bmep for different sampling resolutions

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Figure 3

The magnitude of the numerator terms in Eq. 4 at 1200rpm, 0.2MPa bmep

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Figure 4

The magnitude of terms obtained after twofold differentiation of Eq. 10 at 1200rpm, 0.2MPa bmep

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Figure 5

Pressure derivatives and ROHR at 1200rpm, 0.2MPa bmep

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Figure 6

Pressure derivatives and ROHR at 2100rpm, 0.1MPa bmep

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Figure 7

Pressure derivatives and ROHR at 1500rpm, 1.2MPa bmep

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Figure 8

Third-order derivative and ROHR for different sampling resolutions at 1200rpm, 0.2MPa bmep

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Figure 9

Pressure derivatives and ROHR for sampling resolution 0.5deg CA at 1200rpm, 0.2MPa bmep

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Figure 10

Pressure derivatives and ROHR for sampling resolution 1deg CA at 1200rpm, 0.2MPa bmep

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