A Sensitivity Study of NOx Emission to the Change in the Input Variables of a FGR Industrial Furnace

2003 ◽  
Author(s):  
Q. Jiang ◽  
C. Zhang ◽  
J. Jiang
Keyword(s):  
Dynamic Models ◽  
Mixture Fraction ◽  
Combustion Process ◽  
Sensitivity Study ◽  
Nox Emission ◽  
Moment Closure ◽  
Combustion Model ◽  
Transfer Model ◽  
Nitric Oxides ◽  
Input Variables

Preliminary study has shown that the flue gas recirculation (FGR) is one of the effective ways to reduce the Nitric Oxides (NOx) emission in industrial furnaces. The research reported in this paper concentrates mainly on the development of dynamic models suitable for on-line and real-time feedback control to reduce the NOx emission in industrial furnaces with FGR. To construct an appropriate dynamic model, the relationship between the NOx emission and the furnace input variables, such as the inlet combustion air mass flow rate, inlet combustion air temperature, and the pressure head of the FGR fan, has been investigated. A moment closure method with the assumed β probability density function (PDF) for the mixture fraction is used to model the turbulent non-premixed combustion process in the furnace. The combustion model is derived based on the assumption of instantaneous full chemical equilibrium. The discrete transfer radiation model is chosen as the radiation heat transfer model, and the weighted-sum-of-gray-gases model is used to calculate the absorption coefficient.

Sensitivity Analysis of a FGR Industrial Furnace for NOx Emission Using Frequency Domain Method

2005 ◽  
Vol 129 (2) ◽  
pp. 134-143 ◽  
Author(s):  
Qing Jiang ◽  
Chao Zhang ◽  
Jin Jiang
Keyword(s):  
Frequency Domain ◽  
Mixture Fraction ◽  
Combustion Process ◽  
Nox Emission ◽  
Moment Closure ◽  
Combustion Model ◽  
Frequency Domain Method ◽  
Transfer Model ◽  
Industrial Furnace ◽  
Nitric Oxides

Preliminary study has shown that the flue gas recirculation (FGR) is one of the effective ways to reduce the nitric oxides (NOx) emission in industrial furnaces. The sensitivity of the NOx emission from a FGR industrial furnace to the change in three major furnace input variables—inlet combustion air mass flow rate, inlet combustion air temperature, and pressure head of the FGR fan—is investigated numerically in this study. The investigation is carried out in frequency domain by superimposing sinusoidal signals of different frequencies on to the furnace control inputs around the design operating condition, and observing the frequency responses. The results obtained in this study can be used in the design of active combustion control systems to reduce NOx emission. The numerical simulation of the turbulent non-premixed combustion process in the furnace is conducted using a moment closure method with the assumed β probability density function for the mixture fraction. The combustion model is derived based on the assumption of instantaneous full chemical equilibrium. The discrete transfer radiation model is chosen as the radiation heat transfer model, and the weighted-sum-of-gray-gases model is used to calculate the absorption coefficient.

A Study of the NOx Emission in a Regenerative Industrial Furnace

2001 ◽  
Author(s):  
Qing Jiang ◽  
Chao Zhang
Keyword(s):  
Mixture Fraction ◽  
Combustion Process ◽  
Nox Emission ◽  
Moment Closure ◽  
Combustion Model ◽  
Industrial Furnace ◽  
Low Emission ◽  
Reduction Of Nox ◽  
Closure Method ◽  
Probability Density Function Pdf

Abstract A study of the nitrogen oxides (NOx) emission and combustion process in a gas-fired regenerative, high temperature, low emission industrial furnace has been carried out numerically. The effect of two additives, methanol (CH3OH) and hydrogen peroxide (H2O2), to fuel on the NOx emission has been studied. A moment closure method with the assumed β probability density function (PDF) for mixture fraction is used in the present work to model the turbulent non-premixed combustion process in the furnace. The combustion model is based on the assumption of instantaneous full chemical equilibrium. The results showed that CH3OH is effective in the reduction of NOx in a regenerative industrial furnace. However, H2O2 has no significant effect on the NOx emission.

Reduction of NOx in a Regenerative Industrial Furnace With the Addition of Methanol in the Fuel

2004 ◽  
Vol 126 (2) ◽  
pp. 159-165 ◽  
Author(s):  
Q. Jiang ◽  
C. Zhang ◽  
J. Jiang
Keyword(s):  
Mixture Fraction ◽  
Nox Reduction ◽  
Combustion Process ◽  
Nox Emission ◽  
Moment Closure ◽  
Combustion Model ◽  
Industrial Furnace ◽  
Reduction Of Nox ◽  
Closure Method ◽  
Probability Density Function Pdf

The analysis of the combustion process and NOx emission in a gas-fired regenerative industrial furnace has been carried out numerically. The effect of the additive, methanol CH3OH, to the fuel on the NOx emission is studied. A moment closure method with the assumed β Probability Density Function (PDF) for the mixture fraction is used to model the turbulent non-premixed combustion process in the furnace. The combustion model is based on the assumption of instantaneous full chemical equilibrium. The P-1 model is chosen as the radiation model, and the Weighted-Sum-of-Gray-Gases Model is used to calculate the absorption coefficient. The numerical results showed that the use of CH3OH is effective in the reduction of NOx in a regenerative industrial furnace. The mechanism of NOx reduction by the use of CH3OH is also discussed.

Parameter Based Combustion Model for Large Prechamber Gas Engines

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Jianguo Zhu ◽  
Andreas Wimmer ◽  
Eduard Schneßl ◽  
Hubert Winter ◽  
Franz Chmela
Keyword(s):  
Computing Time ◽  
Combustion Process ◽  
Combustion Model ◽  
Operating Parameters ◽  
Transfer Model ◽  
Boost Pressure ◽  
Considerable Difficulty ◽  
Single Cylinder ◽  
Simulation And Optimization ◽  
Short Computing Time

Challenging requirements for modern large engines regarding power output, fuel consumption, and emissions can only be achieved with carefully adapted combustion systems. With the improvement of simulation methods simulation work is playing a more and more important role for the engine development. Due to their simplicity and short computing time, one-dimensional and zero-dimensional calculation methods are widely applied for the engine cycle simulation and optimization. While the gas dynamic processes in the intake and exhaust systems can already be simulated with sufficient precision, it still represents a considerable difficulty to predict the combustion process exactly. In this contribution, an empirical combustion model for large prechamber gas engines is presented, which was evolved based on measurements on a single cylinder research engine using the design of experiment method. The combustion process in prechamber gas engines is investigated and reproduced successfully by means of a double-vibe function. The mathematical relationship between the engine operating parameters and the parameters of the double-vibe function was determined as a transfer model on the base of comprehensive measurements. The effects of engine operating parameters, e.g., boost pressure, charge temperature, ignition timing, and air/fuel ratio on the combustion process are taken into account in the transfer model. After adding modification functions, the model can be applied to gas engines operated with various gas fuels taking into account the actual air humidity. Comprehensive verifications were conducted on a single-cylinder engine as well as on full-scale engines. With the combination of the combustion model and a gas exchange simulation model the engine performance has been predicted satisfactorily. Due to the simple phenomenological structure of the model, a user-friendly model application and a short computing time is achieved.

scholarly journals Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

2019 ◽  
Vol 103 (4) ◽  
pp. 847-869 ◽  
Author(s):  
A. Giusti ◽  
E. Mastorakos
Keyword(s):  
Turbulent Combustion ◽  
Mixture Fraction ◽  
Moment Closure ◽  
Combustion Model ◽  
Complex Geometries ◽  
Conditional Moment ◽  
Practical Applications ◽  
Spray Flames ◽  
Reaction Zones ◽  
Soot Emissions

AbstractThe development of better laser-based experimental methods and the fast rise in computer power has created an unprecedented shift in turbulent combustion research. The range of species and quantities measured and the advent of kHz-level planar diagnostics are now providing great insights in important phenomena and applications such as local and global extinction, pollutants, and spray combustion that were hitherto unavailable. In simulations, the shift to LES allows better representation of the turbulent flow in complex geometries, but despite the fact that the grid size is smaller than in RANS, the push towards realistic conditions and the need to include more detailed chemistry that includes very fast species and thin reaction zones emphasize the necessity of a sub-grid turbulent combustion model. The paper discusses examples from current research with experiments and modelling that focus on flame transients (self-excited oscillations, local extinction), sprays, soot emissions, and on practical applications. These demonstrate how current models are being validated by experimental data and the concerted efforts the community is taking to promote the modelling tools to industry. In addition, the various coordinated International Workshops on non-premixed, premixed, and spray flames, and on soot are discussed and some of their target flames are explored. These comprise flames that are relatively simple to describe from a fluid mechanics perspective but contain difficult-to-model combustion problems such as extinction, pollutants and multi-mode reaction zones. Recently, swirl spray flames, which are more representative of industrial devices, have been added to the target flames. Typically, good agreement is found with LES and some combustion models such as the progress variable - mixture fraction flamelet model, the Conditional Moment Closure, and the Transported PDF method, but predicting soot emissions and the condition of complete extinction in complex geometries is still elusive.

Parameter Based Combustion Model for Large Pre-Chamber Gas Engines

2009 ◽  
Author(s):  
Jianguo Zhu ◽  
Andreas Wimmer ◽  
Eduard Schneßl ◽  
Hubert Winter ◽  
Franz Chmela
Keyword(s):  
Computing Time ◽  
Combustion Process ◽  
Combustion Model ◽  
Operating Parameters ◽  
Transfer Model ◽  
Boost Pressure ◽  
Single Cylinder ◽  
Simulation And Optimization ◽  
Short Computing Time ◽  
Chamber Gas

Challenging requirements for modern large engines regarding power output, fuel consumption and emissions can only be achieved with carefully adapted combustion systems. With the improvement of simulation methods simulation work is playing a more and more important role for the engine development. Due to their simplicity and short computing time, one-dimensional and zero-dimensional calculation methods are widely applied for the engine cycle simulation and optimization. While the gas dynamic processes in the intake and exhaust system can already be simulated with sufficient precision, it still represents a considerable difficulty to predict the combustion process exactly. In this contribution, an empirical combustion model for large pre-chamber gas engines is presented, which was evolved based on measurements on a single cylinder research engine using the DOE (Design of Experiments) method. The combustion process in pre-chamber gas engines is investigated and reproduced successfully by means of a Double-Vibe function. The mathematical relationship between the engine operating parameters and the parameters of the Double-Vibe function was determined as a transfer model on the base of comprehensive measurements. The effects of engine operating parameters e.g. boost pressure, charge temperature, ignition timing, air/fuel ratio on the combustion process are taken into account in the transfer model. After adding modification functions, the model can be applied to gas engines operated with various gas fuels taking into account the actual air humidity. Comprehensive verifications were conducted on a single cylinder engine as well as on full scale engines. With the combination of the combustion model and a gas exchange simulation model the engine performance has been predicted satisfactorily. Due to the simple phenomenological structure of the model, a user-friendly model application and a short computing time is achieved.

Numerical Investigation of Flame Structure and Soot Formation in a Lab-Scale Rich-Quench-Lean Burner

2018 ◽  
Author(s):  
Andrea Giusti ◽  
Savvas Gkantonas ◽  
Jenna M. Foale ◽  
Epaminondas Mastorakos
Keyword(s):  
Numerical Simulations ◽  
Soot Formation ◽  
Mixture Fraction ◽  
Flame Structure ◽  
Swirling Flows ◽  
Operating Conditions ◽  
Moment Closure ◽  
Combustion Model ◽  
Ethylene Flame ◽  
Soot Precursors

The understanding of the processes involved in soot formation and oxidation is a critical factor for a reliable prediction of emissions in aero-engines, particularly as legislation becomes increasingly stringent. This work studies the flame structure and soot formation in a lab-scale burner, which reproduces the main features of a Rich-Quench-Lean (RQL) combustor, using high-fidelity numerical simulations. The investigated burner, developed at the University of Cambridge, is based on a bluff-body swirl-stabilised ethylene flame, with air provided in the primary region through two concentric swirling flows and quenching enabled by means of four dilution jets at variable distance downstream. Measurements for different air split between the two inlet swirling flows and dilution ports, and different height of the dilution jets, indicate noticeable differences in the soot tendency. Numerical simulations have been performed using Large-Eddy Simulation with the Conditional Moment Closure combustion model and a two-equation model for soot, allowing a detailed resolution of the mixing field and to directly take into account the effect of turbulent transport on the flame structure, which has been shown to have an important effect on the soot formation and evolution. The main objective of this work is to study the flow field and mixing characteristics in the burner’s primary region, in order to improve the understanding of the mechanisms leading to the soot behaviour observed in the experiment at different operating conditions. Results show the key role of mixing in determining the level of soot in the burner, with the soot production mainly related to the extension of the flame zone characterized by a rich mixture, with pyrolysis products and soot precursors. The presence of additional dilution air seems to improve the oxidation and leads to a leaner mixture in the primary combustion region whereas the air added through the outer swirl stream seems to have less impact on the mixture formation in the primary region. Analysis of the solution in mixture fraction space shows the importance of residence time for the soot formation and highlights the existence of a range of values of mixture fraction, between 0.1 and 0.2, where the soot production terms are maximum. High residence times and local air-to-fuel ratio in the range of high soot production should be avoided to decrease the level of soot mass fraction in the burner.

A Study on Biodiesel NOx Emission Control With the Reduced Chemical Kinetics Model

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Juncheng Li ◽  
Zhiyu Han ◽  
Cai Shen ◽  
Chia-fon Lee
Keyword(s):  
Chemical Kinetics ◽  
Combustion Process ◽  
Operating Conditions ◽  
Nox Emission ◽  
Kinetics Model ◽  
Combustion Model ◽  
Nox Emissions ◽  
Soot Emission ◽  
Start Of Injection ◽  
Combustion Processes

In this paper, the effects of the start of injection (SOI) timing and exhaust gas recirculation (EGR) rate on the nitrogen oxides (NOx) emissions of a biodiesel-powered diesel engine are studied with computational fluid dynamics (CFD) coupling with a chemical kinetics model. The KIVA code coupling with a CHEMKIN-II chemistry solver is applied to the simulation of the in-cylinder combustion process. A surrogate biodiesel mechanism consisting of two fuel components is employed as the combustion model of soybean biodiesel. The in-cylinder combustion processes of the cases with four injection timings and three EGR rates are simulated. The simulation results show that the calculated NOx emissions of the cases with default EGR rate are reduced by 20.3% and 32.9% when the injection timings are delayed by 2- and 4-deg crank angle, respectively. The calculated NOx emissions of the cases with 24.0% and 28.0% EGR are reduced by 38.4% and 62.8%, respectively, compared to that of the case with default SOI and 19.2% EGR. But higher EGR rate deteriorates the soot emission. When EGR rate is 28.0% and SOI is advanced by 2 deg, the NOx emission is reduced by 55.1% and soot emission is controlled as that of the case with 24% EGR and default SOI. The NOx emissions of biodiesel combustion can be effectively improved by SOI retardation or increasing EGR rate. Under the studied engine operating conditions, introducing more 4.8% EGR into the intake air with unchanged SOI is more effective for NOx emission controlling than that of 4-deg SOI retardation with default EGR rate.

Numerical Simulations of Highly Preheated Air Combustion in an Industrial Furnace

1998 ◽  
Vol 120 (4) ◽  
pp. 276-284 ◽  
Author(s):  
T. Ishii ◽  
C. Zhang ◽  
S. Sugiyama
Keyword(s):  
Numerical Simulations ◽  
Production Rate ◽  
Fuel Injection ◽  
Velocity Ratio ◽  
Combustion Process ◽  
Moment Closure ◽  
Combustion Model ◽  
Injection Velocity ◽  
Heating Efficiency ◽  
Reheat Furnace

The numerical simulations of reactive turbulent flows and heat transfer in an industrial slab reheat furnace in which the combustion air is highly preheated have been carried out. The influence of the ratio of the air and fuel injection velocities on the NOx production rate in the furnace has also been studied numerically. A moment closure method with the assumed β probability density function (PDF) for mixture fraction was used in the present work to model the turbulent non-premixed combustion process in the furnace. The combustion model was based on the assumption of instantaneous full chemical equilibrium. The turbulence was modeled by the standard k-ε model with a wall function. The numerical simulations have provided complete information on the flow, heat, and mass transfer in the furnace. The results also indicate that a low NOx emission and high heating efficiency can be achieved in the slab reheat furnace by using low NOx regenerative burners. It is found that the air/fuel injection velocity ratio has a strong influence on the NOx production rate in the furnace.

Numerical Simulation of Furnace Combustion Characteristic in HTAC

2011 ◽  
Vol 84-85 ◽  
pp. 274-278
Author(s):  
Tao Du ◽  
Li Sheng Ji ◽  
Guang Yi Gao
Keyword(s):  
Radiative Heat ◽  
Combustion Process ◽  
Concentration Field ◽  
Calorific Value ◽  
Combustion Characteristic ◽  
Combustion Model ◽  
Discrete Ordinates ◽  
Transfer Model ◽  
Field Temperature ◽  
Fluent Software

In this thesis, in the double preheating system of air and gas, the high temperature air combustion process of low calorific value gas, in which the FLUENT software is used as the calculating tool and furnace model as the object, is numerically simulated by use of the k-ε turbulent two-way model, the PDF combustion model, discrete-ordinates-method radiative heat transfer model and the modified NOX -generation thermal model. Get the flow field, temperature field and concentration field inside the furnace in different times.

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