Transcript Slide 1

Institute for Engineering Thermophysics
National Academy of Sciences of Ukraine
THERMOGASDYNAMICS AND ECOLOGICAL
CHARACTERISTICS OF COMBUSTION CHAMBERS
RUNNING THE NATURAL GAS
Prof. A. Khalatov, Dr. S. Kobzar, Dr. G. Kovalenko,
Dr. V. Demchenko
The 11th PHOENICS Users Conference,
London, UK, 2006
СОNTENTS
1. Introduction
2. Boiler «Victor» and Combustion Chamber
3. Results and Discussions:
3.1. Basic design
3.2. H2S in the natural gas
4. Conclusions.
1. Introduction
• Computer design is based on the flow, heat and mass
transfer modeling using numerical simulation of basic
transport equations.
• Commercial
packages
«FLUENT»,
«STAR-CD»,
«PHOENICS» and others are widely used in various
applications.
• Advantages:
- saving of time and money;
- wide range of designs and boundary conditions;
- easy changes in air and fuel regimes;
- easy changes in combustion chamber design;
- clear demonstration of results;
- finding of information not registered in experiments.
• Examples of Computer Modeling
• Flow streamlines inside
the burner.
• Aerodynamics of the beburner combustion chamber.
2. Boiler “Victor» and Combustion Chamber
Exit of gases
• Burner
• Boiler «Victor»
Boiler «Victor», 100 kWt power. Combustion chamber : D = 412mm, L = 1140 mm,
Burner: Giersсh–RG20 (gas flow rate – 12,6 m3/h; air excess – 1,2)
3. Results and Discussions
• Kintetics of natural gas burning:
1. Chemical reaction:
СН4 + 1,5·02
CO + 2·H20
CO + 0,5·O2
CO2
2. Average speed of the methane burning (first reaction; model of the vortex
breakdown - EBU):
RCH4 = - CEBU·min {CH4; O2/3,0}··k ,
кg/(m3с),
CEBU=2,0
3. Average speed of СО to СО2 oxidation (minimal magnitude of a speed
according to EBU-model and Arrenius law) :
- RCO = - min {REBU; RAr );
- RAr= 5,4 109 ·exp {- 15000 / T}·[CO]·[O2]0,25 ·[H20]0,5 ,
4. NOx formation : Thermal and Prompt мechanizm.
[к·mol / (m3·с)]
3.1. Basic design
Grid : (Х, Y, Z): 90 х 19 х 46; Global convergence parameter – 0,1%
Commercial CFD Package PHOENICS v.3.6 was used in all calculations
• Flow field.
• Temperature field: Tavr. = 1060 0C, Tмах = 1493 0C .
• NOx concentration .
• Prediction: 19,56 мg/м3,
Experiment: 24 мg/m3.
• Methane concentration.
• CO concentration.
- Prediction: 2,4 мg/m3, Experiment: 4 мg/m3
3.2. H2S in the natural gas
- Direct chemical reaction of H2S burning :
H2S + 1,5·O2
SO2 + H20
- Average speed of H2S burning (EBU - model):
RH2S = - CEBU ·min {H2S; O2 / 1,41 }·(·k),
[кg/(m3с)],
• Temperature field: Toutlet = 966 0C , Tмах = 1334 0C
CEBU=4,0
• Temperature field:
•Toutlet = 966 0C, Tмах = 1334 0C
• Temperature field (basic design):
Toutlet = 1060 0C, Tмах = 1493 0C
The primary reason of the temperature in the combustion chamber reduction :
decrease in the fuel “lowest” caloric value.
• NOx concentration
• СО concentration
Prediction : 20,83 мg/m3
Prediction : 6 мg/m3
Temperature decrease in the combustion chamber leads to
the increased carbon monoxide (CO) generation.
4. C o n c l u s I o n s
1. The modern computer technologies are widely employed for design
and modernization of boilers and combustion chambers.
2. Computer technologies enables to analyzing the number of design
variants and flow regimes before the fabrication or modernization;
this allows us to take more justified solutions, to save the time and
funding.
3. Computer modeling enables detecting some specific features of the
combustion chamber flow and temperature fields, which are
actually unable to be detected in experiments.
4. The experiment keeps its important meaning; however it should be
employed after basic decisions regarding combustion chamber
design and flow regimes.