| 1. |
- Gogan, Adina
(författare)
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Full Cycle Engine Simulations with Detailed Chemistry
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The modeling work developed in this thesis can be divided in two main areas of investigations: autoignition related to spark ignition engine and combustion and emissions formation in relation to diesel engines. A first version of a detailed kinetics engine simulation program, extended to handle full cycle calculations, was employed in order to demonstrate the strong effect that nitric oxide from the residual gas has on the autoignition onset. It was found that a concentration of about 500 ppm in the intake gas determines a maximal promotion of autoignition. Increased simulation capabilities were achieved by integrating the in house detailed kinetic code into a commercial 1-D engine program. By this it was possible on one hand to have a simulation tool able to handle detailed kinetics and thus have control over combustion and emissions, and on the other hand to monitor global engine operation conditions. Further accuracy on autoignition was achieved by employing a stochastic reactor model (SRM) for spark ignition engine calculations. Based on the probability density function (PDF) this approach was able to model phenomena with strong influence on engine knock as: turbulent mixing and inhomogeneities, phenomena usually neglected by regular existing engine programs. While keeping computational time low and still using detailed chemistry, good correlative results were obtained with the stochastic approach. For the second part of the work, the stochastic reactor model was applied for diesel engine combustion and emissions investigations. The purpose of this implementation was primarily the calculation of NOx emissions and soot within diesel engines. Soot calculations were based on the method of moments. Comparisons of soot production with measured data from a carbon black reactor indicate good agreement. The diesel SRM model was applied on a FIAT car engine and on a low speed marine engine. The model is capable to correlate the ignition timing and to indicate the trends in NOx and soot generation.
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| 2. |
- Gogan, Adina, et al.
(författare)
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Knock modeling: an integrated tool for detailed chemistry and engine cycle simulation
- 2003
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Ingår i: Spark Ignition and Compression Ignition Engines Modeling. - 9780768013214
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Konferensbidrag (refereegranskat)abstract
- For the simultaneous evaluation of the influence on engine knock of both chemical conditions and global operating parameters, a combined tool was developed. Thus, a two-zone kinetic model for SI engine combustion calculation (Ignition) was implemented into an engine cycle simulation commercial code. The combined model predictions are compared with experimental data from a single-cylinder test engine. This shows that the model can accurately predict the knock onset and in-cylinder pressure and temperature for different lambda conditions, with and without EGR. The influence of nitric oxide amount from residual gas in relation with knock is further investigated. The created numerical tool represents a useful support for experimental measurements, reducing the number of tests required to assess the proper engine control strategies.
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| 3. |
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| 4. |
- Gogan, Adina, et al.
(författare)
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Stochastic model for the investigation of the effect of inhomogeneities on engine knock
- 2004
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Ingår i: Proceedings of the 2004 Fall Technical Conference of the ASME Internal Combustion Engine Division. - 0791837467 ; , s. 399-408
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Konferensbidrag (refereegranskat)abstract
- A stochastic model based on a probability density function (PDF) approach was developed for the investigation of spark ignition (SI) engine knock conditions. The model is based on a two zone model, where the burned and unburned gases are described as stochastic reactors, and the movement of the turbulent flame front is expressed with a Wiebe function. Using a stochastic particle ensemble to represent the PDF of the scalar variables associated with the burned and unburned gases, allows the consideration of inhomogeneities in gas composition and temperature, as well as turbulence mixing effects. The turbulent mixing is described with the interaction by exchange with the mean model. A stochastic jump process is used for modeling the heat transfer, hence accounting for the temperature fluctuations and the fluid wall interaction. Detailed chemistry is used in the calculations. A parameter study investigates the effects of end gas inhomogeneities related to residual gas composition and temperature, on the autoignition process. adina.gogan@vok.lth.se.
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| 5. |
- Gogan, Adina, et al.
(författare)
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Stochastic model for the investigation of the influence of turbulent mixing on engine knock
- 2004
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Ingår i: SAE Transactions Journal of Engines. - 0096-736X. ; 113:3, s. 1594-1603
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Tidskriftsartikel (refereegranskat)abstract
- A stochastic model based on a probability density function (PDF) was developed for the investigation of different conditions that determine knock in spark ignition (SI) engine, with focus on the turbulent mixing. The model used is based on a two-zone approach, where the burned and unburned gases are described as stochastic reactors. By using a stochastic ensemble to represent the PDF of the scalar variables associated with the burned and the unburned gases it is possible to investigate phenomena that are neglected by the regular existing models (as gas non-uniformity, turbulence mixing, or the variable gas-wall interaction). Two mixing models are implemented for describing the turbulent mixing: the deterministic interaction by exchange with the mean (IEM) model and the stochastic coalescence/ dispersal (C/D) model. Also, a stochastic jump process is employed for modeling the irregularities in the heat transfer. Parameter studies are carried out in order to assess the influence of the turbulence intensity and of the fluctuations in the gas - wall interactions.
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| 6. |
- Grandin, Börje, et al.
(författare)
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Heat Release in the End-Gas Prior to Knock in Lean, Rich and Stoichiometric Mixtures With and Without Egr
- 2002
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Ingår i: SAE Technical Papers. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- SI Engine knock is caused by autoignition in the unburnt part of the mixture (end-gas) ahead of the propagating flame. Autoignition of the end-gas occurs when the temperature and pressure exceeds a critical limit when comparatively slow reactions - releasing moderate amounts of heat - transform into ignition and rapid heat release. In this paper the difference in the heat released in the end-gas - by low temperature chemistry - between lean, rich, stochiometric, and stoichiometric mixtures diluted with cooled EGR was examined by measuring the temperature in the end-gas with Dual Broadband Rotational CARS. The measured temperature history was compared with an isentropic temperature calculated from the cylinder pressure trace. The experimentally obtained values for knock onset were compared with results from a two-zone thermodynamic model including detailed chemistry modelling of the end-gas reactions.
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| 7. |
- Stenlåås, Ola, et al.
(författare)
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The Influence of Nitric Oxide on the Occurrence of Autoignition in the End Gas of Spark Ignition Engines
- 2002
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Ingår i: SAE Technical Papers.
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Tidskriftsartikel (refereegranskat)abstract
- Full-cycle simulations of a spark ignition engine running on a primary reference fuel have been performed using a two-zone model. A detailed kinetic mechanism is taken into account in each of the zones, while the propagating flame front is calculated from a Wiebe function. The initial conditions for the unburned gas zone were calculated as a mixture of fresh gas and rest gas. The composition of the burned gas zone at the end of the last engine cycle, including nitric oxide emissions, was taken as rest gas. The simulations confirm that the occurrence of autoignition in the end gas is sensitive on the amount of nitric oxide in the rest gas of the spark ignition engine. The comparison of autoignition timings calculated for a single-cylinder test engine are getting more accurate if the nitric oxide in the initial gases is taken into account.
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| 8. |
- Stenlåås, Ola, et al.
(författare)
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The influence of NO on the occurence of autoignition in the end-gas of SI-engines
- 2002
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Ingår i: SAE Paper 2002-01-2699.
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Konferensbidrag (refereegranskat)abstract
- Full-cycle simulations of a spark ignition engine running on a primary reference fuel have been performed using a two-zone model. A detailed kinetic mechanism is taken into account in each of the zones, while the propagating flame front is calculated from a Wiebe function. The initial conditions for the unburned gas zone were calculated as a mixture of fresh gas and rest gas. The composition of the burned gas zone at the end of the last engine cycle, including nitric oxide emissions, was taken as rest gas. The simulations confirm that the occurrence of autoignition in the end gas is sensitive on the amount of nitric oxide in the rest gas of the spark ignition engine. The comparison of autoignition timings calculated for a single-cylinder test engine are getting more accurate if the nitric oxide in the initial gases is taken into account.
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