Theoretical Analysis and Numerical Simulation of Spectral Radiative Properties of Combustion Gases in Oxy/Air-Fired Combustion Systems
Maximov, Alexander (2012-12-11)
Väitöskirja
Maximov, Alexander
11.12.2012
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-265-347-5
https://urn.fi/URN:ISBN:978-952-265-347-5
Tiivistelmä
Energy efficiency is one of the major objectives which should be achieved in order to
implement the limited energy resources of the world in a sustainable way. Since radiative
heat transfer is the dominant heat transfer mechanism in most of fossil fuel combustion
systems, more accurate insight and models may cause improvement in the energy efficiency
of the new designed combustion systems. The radiative properties of combustion
gases are highly wavelength dependent. Better models for calculating the radiative properties
of combustion gases are highly required in the modeling of large scale industrial
combustion systems. With detailed knowledge of spectral radiative properties of gases,
the modeling of combustion processes in the different applications can be more accurate.
In order to propose a new method for effective non gray modeling of radiative heat transfer
in combustion systems, different models for the spectral properties of gases including
SNBM, EWBM, and WSGGM have been studied in this research. Using this detailed
analysis of different approaches, the thesis presents new methods for gray and non gray
radiative heat transfer modeling in homogeneous and inhomogeneous H2O–CO2 mixtures
at atmospheric pressure. The proposed method is able to support the modeling of a
wide range of combustion systems including the oxy-fired combustion scenario. The new
methods are based on implementing some pre-obtained correlations for the total emissivity
and band absorption coefficient of H2O–CO2 mixtures in different temperatures, gas
compositions, and optical path lengths. They can be easily used within any commercial
CFD software for radiative heat transfer modeling resulting in more accurate, simple, and
fast calculations.
The new methods were successfully used in CFD modeling by applying them to industrial
scale backpass channel under oxy-fired conditions. The developed approaches are more
accurate compared with other methods; moreover, they can provide complete explanation
and detailed analysis of the radiation heat transfer in different systems under different
combustion conditions. The methods were verified by applying them to some benchmarks,
and they showed a good level of accuracy and computational speed compared to
other methods. Furthermore, the implementation of the suggested banded approach in
CFD software is very easy and straightforward.
implement the limited energy resources of the world in a sustainable way. Since radiative
heat transfer is the dominant heat transfer mechanism in most of fossil fuel combustion
systems, more accurate insight and models may cause improvement in the energy efficiency
of the new designed combustion systems. The radiative properties of combustion
gases are highly wavelength dependent. Better models for calculating the radiative properties
of combustion gases are highly required in the modeling of large scale industrial
combustion systems. With detailed knowledge of spectral radiative properties of gases,
the modeling of combustion processes in the different applications can be more accurate.
In order to propose a new method for effective non gray modeling of radiative heat transfer
in combustion systems, different models for the spectral properties of gases including
SNBM, EWBM, and WSGGM have been studied in this research. Using this detailed
analysis of different approaches, the thesis presents new methods for gray and non gray
radiative heat transfer modeling in homogeneous and inhomogeneous H2O–CO2 mixtures
at atmospheric pressure. The proposed method is able to support the modeling of a
wide range of combustion systems including the oxy-fired combustion scenario. The new
methods are based on implementing some pre-obtained correlations for the total emissivity
and band absorption coefficient of H2O–CO2 mixtures in different temperatures, gas
compositions, and optical path lengths. They can be easily used within any commercial
CFD software for radiative heat transfer modeling resulting in more accurate, simple, and
fast calculations.
The new methods were successfully used in CFD modeling by applying them to industrial
scale backpass channel under oxy-fired conditions. The developed approaches are more
accurate compared with other methods; moreover, they can provide complete explanation
and detailed analysis of the radiation heat transfer in different systems under different
combustion conditions. The methods were verified by applying them to some benchmarks,
and they showed a good level of accuracy and computational speed compared to
other methods. Furthermore, the implementation of the suggested banded approach in
CFD software is very easy and straightforward.
Kokoelmat
- Väitöskirjat [1037]