Improvement and experimental validation of a multi-zone model for combustion and NO emissions in CNG fueled spark ignition engine |
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Authors: | Asgari Omid Hannani Siamak Kazemzadeh Ebrahimi Reza |
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Affiliation: | 1.Mechanical Engineering, Sharif University of Technology, Tehran, 11365-9567, Iran ;2.Mechanical Engineering, KNTU University of Technology, Tehran, 19697-64499, Iran ; |
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Abstract: | This article reports the experimental and theoretical results for a spark ignition engine working with compressed natural
gas as a fuel. The theoretical part of this work uses a zero-dimensional, multi-zone combustion model in order to predict
nitric oxide (NO) emission in a spark ignition (SI) engine. The basic concept of the model is the division of the burned gas
into several distinct zones for taking into account the temperature stratification of the burned mixture during combustion.
This is especially important for accurate NO emissions predictions, since NO formation is strongly temperature dependent.
During combustion, 12 products are obtained by chemical equilibrium via Gibbs energy minimization method and nitric oxide
formation is calculated from chemical kinetic by the extended Zeldovich mechanism. The burning rate required as input to the
model is expressed as a Wiebe function, fitted to experimentally derived burn rates. The model is validated against experimental
data from a four-cylinder, four-stroke, SI gas engine (EF7) running with CNG fuel. The calculated values for pressure and
nitric oxide emissions show good agreement with the experimental data. The superiority of the multizone model over its two-zone
counterpart is demonstrated in view of its more realistic in-cylinder NO emissions predictions when compared to the available
experimental data. |
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