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Empirical combustion modeling in SI engines
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This licentiate thesis concerns the modeling of spark ignition engine combustion for use in one dimensional simulation tools. Modeling of knock is of particular interest when modeling turbocharged engines since knock usually limits the possible engine output at high load. The knocking sound is an acoustic phenomenon with pressure oscillations triggered by autoignition of the unburned charge ahead of the propagating flame front and it is potentially damaging to the engine. To be able to predict knock it is essential to predict the temperature and pressure in the unburned charge ahead of the flame front. Hence, an adequate combustion model is needed.

The combustion model presented here is based on established correlations of laminar burning velocity which are used to predict changes in combustion duration relative to a base operating condition. Turbulence influence is captured in empirical correlations to the engine operating parameters spark advance and engine speed. This approach makes the combustion model predictive in terms of changes in gas properties such as mixture strength, residual gas content, pressure and temperature. However, a base operating condition and calibration of the turbulence correlations is still needed when using this combustion model.

The empirical models presented in this thesis are based on extensive measurements on a turbocharged four cylinder passenger car engine. The knock model is simply a calibration of the Arrhenius type equation for ignition delay in the widely used Livengood-Wu knock integral to the particular fuel and engine used in this work.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , xii, 72 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2005:19
Keyword [en]
spark ignited engines, combustion modeling, knock, 1D simulation, Wiebe, divided exhaust period
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-575OAI: oai:DiVA.org:kth-575DiVA: diva2:14480
Presentation
2005-09-26, B1, KTH, Brinellvägen 23, Stockholm, 13:00
Note
QC 20101209Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2010-12-09Bibliographically approved
List of papers
1. Optimizing engine concepts by using a simple model for knock prediction
Open this publication in new window or tab >>Optimizing engine concepts by using a simple model for knock prediction
Show others...
2003 (English)In: SAE Paper 2003-01-3123, SAE , 2003Conference paper, Published paper (Refereed)
Abstract [en]

The objective of this paper is to present a simulation model for controlling combustion phasing in order to avoid knock in turbocharged SI engines. An empirically based knock model was integrated in a one-dimensional simulation tool. The empirical knock model was optimized and validated against engine tests for a variety of speeds and λ . This model can be used to optimize control strategies as well as design of new engine concepts.

Place, publisher, year, edition, pages
SAE, 2003
Series
SAE Technical Paper Series, ISSN 0148-7191
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-6543 (URN)10.4271/2003-01-3123 (DOI)
Conference
SAE Powertrain & Fluid Systems Conference & Exhibition, October 2003, Pittsburgh, PA, USA
Note
QC 20101111Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2010-12-09Bibliographically approved
2. Divided exhaust period: a gas exchange system for turbocharged SI engines
Open this publication in new window or tab >>Divided exhaust period: a gas exchange system for turbocharged SI engines
2005 (English)In: SAE Paper 2005-01-1150, SAE , 2005Conference paper, Published paper (Refereed)
Abstract [en]

The necessity to limit the boost pressure in turbocharged gasoline engines results in higher exhaust pressure than inlet pressure at engine speeds when the wastegate is opened. This imbalance has a negative influence on the exhaust scavenging of the engine and results in high levels of residual gas and consequently the engine is more prone to knock.

Place, publisher, year, edition, pages
SAE, 2005
Series
SAE technical paper series, ISSN 0148-7191
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-6542 (URN)10.4271/2005-01-1150 (DOI)2-s2.0-79959817910 (Scopus ID)
Conference
SAE 2005 World Congress & Exhibition, April 2005, Detroit, MI, USA
Note
QC 20101111Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2010-12-09Bibliographically approved
3. An empirical SI combustion model using laminar burning velocity correlations
Open this publication in new window or tab >>An empirical SI combustion model using laminar burning velocity correlations
2005 (English)In: SAE transactions, ISSN 0096-736X, Vol. 114, no 4, 833-846 p.Article in journal (Refereed) Published
Abstract [en]

Predictive simulation models are needed in order to exploit the full benefits of 1-D engine simulation. Simulation model alterations such as cam phasing affect the gas composition and gas state in the cylinders and have an effect on the combustion. Modelling of these effects is particularly important when the engine is knock limited. A knock model, able to phase the combustion towards the knock limit, was previously developed by the authors. A major challenge in such knock models is to predict the pressure and temperature evolution in the end-gas accurately through an adequate combustion model. The Wiebe function is often used to model the combustion in Sl engine simulations, owing to its ease of use and computational efficiency. The Wiebe function simply imposes a curve shape for the fuel burn rate and the parameters are easily determined from calculated heat release. Detailed models of turbulent combustion also exist which require more knowledge or assumptions about combustion chamber turbulence. The combustion model proposed in this paper uses existing correlations of laminar burning velocity to predict the parameters of the Wiebe function relative to a base operating condition. The model aims at predicting combustion at high load operation. Experimental and simulation data from a gasoline fuelled 4-cylinder turbo charged port injected spark ignition engine are used to correlate the Wiebe function parameters dependence on laminar burning velocity.

National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-27214 (URN)10.4271/2005-01-2106 (DOI)2-s2.0-79959840667 (Scopus ID)
Note

QC 20101209

Available from: 2010-12-09 Created: 2010-12-09 Last updated: 2016-12-14Bibliographically approved

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