Experimental Observation and Numerical Modelling of a Laminar Double Coflow Methane/Air Diffusion Flame

2007 ◽  
Author(s):  
Fengshan Liu ◽  
Wenjun Kong
Keyword(s):  
Flow Rate ◽  
Diffusion Flame ◽  
Soot Formation ◽  
Control Volume ◽  
Air Flow ◽  
Double Diffusion ◽  
Radiative Properties ◽  
Discrete Ordinates ◽  
Air Flow Rate ◽  
Air Diffusion

The effect of the central air flow rate on the structure and sooting characteristics of a laminar double coflow methane/air diffusion flame was experimentally observed and recorded by a digital camera. The double diffusion flame was generated using a modified Gu¨lder laminar coflow diffusion flame burner by introducing an air flow in the centre of the fuel pipe. Numerical calculations of the double diffusion flame at different central air flow rates were conducted by solving the elliptic conservation equations of mass, momentum, species, and energy in axisymmetric cylindrical coordinates using a standard control volume method. Detailed multi-component thermal and transport properties and detailed combustion chemistry were employed in the modelling. Soot formation was modeled using a semi-empirical acetylene based model in which two transport equations for soot mass fraction and soot number density per unit mass were solved. Thermal radiation was calculated using the discrete-ordinates method and a 9-band non-grey model for the radiative properties of the CO-CO2-H2O-soot mixture. The numerical model reproduced qualitatively the experimental observations of the effect of central air flow rate on the structure and sooting characteristics.

Effects of Hydrogen and Helium Addition to Fuel on Soot Formation in Axisymmetric Coflow Laminar Methane-Air Diffusion Flame

2007 ◽  
Author(s):  
Fengshan Liu ◽  
Francesca Migliorini ◽  
Francesco Cignoli ◽  
Silvana De Iuliis ◽  
Giorgio Zizak
Keyword(s):  
Diffusion Flame ◽  
Volume Fraction ◽  
Soot Formation ◽  
Experimental Studies ◽  
Wide Band ◽  
Radiative Properties ◽  
Discrete Ordinates ◽  
Band Model ◽  
Hydrogen Addition ◽  
Air Diffusion

Numerical and experimental studies were conducted to investigate the effects of hydrogen and helium addition to fuel on soot formation in atmospheric axisymmetric coflow laminar methane-air diffusion flame. Soot temperature and volume fraction distributions were measured using a two-dimensional two-color technique. Numerically the conservation equations of mass, momentum, energy, and species in the limit of low-Mach number were solved. Detailed gas-phase chemistry and thermal and transport properties were accounted for. Radiative heat transfer by CO, CO2, H2O, and soot was calculated using the discrete-ordinates method with the radiative properties of the mixture obtained from a wide-band model. Soot was modeled using a two-equation semi-empirical model in which the mechanisms for inception and surface growth are assumed to be PAH coagulation and H-abstraction acetylene addition. Both experimental and numerical results show that helium addition is more efficient than hydrogen addition in reducing soot formation in the methane flame. These results are different from the previous investigations in ethylene flames where the hydrogen addition was found to be more effective in reducing soot formation than helium addition due to the additional chemical suppression of hydrogen on soot. It is suggested here that hydrogen chemically enhances soot formation when added to methane.

scholarly journals Numerical Study of the Effects of Pressure and Gravitational Acceleration on Soot Formation in Laminar Axisymmetric Coflow Methane/Air Diffusion Flame

2009 ◽  
Author(s):  
Fengshan Liu ◽  
Gregory J. Smallwood ◽  
Wenjun Kong
Keyword(s):  
Mass Flow ◽  
Diffusion Flame ◽  
Soot Formation ◽  
Radiative Properties ◽  
Gravitational Acceleration ◽  
Gravity Level ◽  
Flow Rates ◽  
Scaling Relationship ◽  
Mass Flow Rates ◽  
Air Diffusion

The structure and soot formation characteristics of a coflow laminar methane/air diffusion flame under conditions of constant p2g and mass flow rates of the air and fuel streams were numerically investigated in order to examine the validity of the p2g scaling relationship. The p2g scaling relationship has been used to experimentally investigate soot formation in weakly-buoyant laminar diffusion flames by conducting experiments at reduced pressures. Detailed numerical calculations were conducted by solving the elliptic conservation equations of mass, momentum, species, and energy in axisymmetric cylindrical coordinates using a standard control volume method. Detailed multi-component thermal and transport properties and detail combustion chemistry were employed in the modelling. Soot formation was modeled using a semi-empirical acetylene based model in which two transport equations for the soot mass fraction and soot number density per unit mass were solved. Thermal radiation was calculated using the discrete-ordinates method and a 9-band non-grey model for the radiative properties of the CO-CO2-H2O-soot mixture. The flame structure and soot formation characteristics exhibit strong dependence on the ambient pressure even though p2g and the mass flow rates are kept constant. Significantly more soot is produced with increasing the pressure and decreasing the gravity level. Numerical results clearly demonstrate that the p2g scaling relationship is invalid as far as soot formation is concerned.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

scholarly journals Modeling and optimization of radish root extract drying as peroxidase source using spouted bed dryer

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shahrbanoo Hamedi ◽  
M. Mehdi Afsahi ◽  
Ali Riahi-Madvar ◽  
Ali Mohebbi
Keyword(s):  
Kinetic Parameters ◽  
Flow Rate ◽  
Air Flow ◽  
Cost Effective ◽  
Industrial Applications ◽  
Interactive Effects ◽  
Root Extract ◽  
Air Flow Rate ◽  
Spouted Bed ◽  
Radish Root

AbstractThe main advantages of the dried enzymes are the lower cost of storage and longer time of preservation for industrial applications. In this study, the spouted bed dryer was utilized for drying the garden radish (Raphanus sativus L.) root extract as a cost-effective source of the peroxidase enzyme. The response surface methodology (RSM) was used to evaluate the individual and interactive effects of main parameters (the inlet air temperature (T) and the ratio of air flow rate to the minimum spouting air flow rate (Q)) on the residual enzyme activity (REA). The maximum REA of 38.7% was obtained at T = 50 °C and Q = 1.4. To investigate the drying effect on the catalytic activity, the optimum reaction conditions (pH and temperature), as well as kinetic parameters, were investigated for the fresh and dried enzyme extracts (FEE and DEE). The obtained results showed that the optimum pH of DEE was decreased by 12.3% compared to FEE, while the optimum temperature of DEE compared to FEE increased by a factor of 85.7%. Moreover, kinetic parameters, thermal-stability, and shelf life of the enzyme were considerably improved after drying by the spouted bed. Overall, the results confirmed that a spouted bed reactor can be used as a promising method for drying heat-sensitive materials such as peroxidase enzyme.

Method to Determine an Optimal Air-Flow Rate in Solar Collectors

1979 ◽  
Vol 3 (6) ◽  
pp. 357-362
Author(s):  
H. C. Hewitt ◽  
E. I. Griggs
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Solar Collectors ◽  
Air Flow Rate

Model-Based Analysis of Transient Behavior of Large Scale CFB Boilers

2003 ◽  
Author(s):  
Ari Kettunen ◽  
Timo Hyppa¨nen ◽  
Ari-Pekka Kirkinen ◽  
Esa Maikkola
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Model Parameters ◽  
Air Flow Rate ◽  
Process Data ◽  
Cfb Boiler ◽  
Flow Rates ◽  
Load Change ◽  
Secondary Air

The main objective of this study was to investigate the load change capability and effect of the individual control variables, such as fuel, primary air and secondary air flow rates, on the dynamics of large-scale CFB boilers. The dynamics of the CFB process were examined by dynamic process tests and by simulation studies. A multi-faceted set of transient process tests were performed at a commercial 235 MWe CFB unit. Fuel reactivity and interaction between gas flow rates, solid concentration profiles and heat transfer were studied by step changes of the following controllable variables: fuel feed rate, primary air flow rate, secondary air flow rate and primary to secondary air flow ratio. Load change performance was tested using two different types of tests: open and closed loop load changes. A tailored dynamic simulator for the CFB boiler was built and fine-tuned by determining the model parameters and by validating the models of each process component against measured process data of the transient test program. The know-how about the boiler dynamics obtained from the model analysis and the developed CFB simulator were utilized in designing the control systems of three new 262 MWe CFB units, which are now under construction. Further, the simulator was applied for the control system development and transient analysis of the supercritical OTU CFB boiler.

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