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.

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 Fuel Utilization Through Oxygen-Enriched Combustion in a Reheat Furnace Pusher-Type

2021 ◽  
Author(s):  
Francisco J. Martinez Zambrano ◽  
Armin K. Silaen ◽  
Kelly Tian ◽  
Joe Maiolo ◽  
Chenn Zhou
Keyword(s):  
Heat Flux ◽  
Fuel Injection ◽  
Combustion Process ◽  
Oxygen Enrichment ◽  
Rolling Temperature ◽  
Heating Zone ◽  
Reheat Furnace ◽  
Steel Slabs ◽  
The Impact ◽  
Reheating Process

Abstract Steelmaking is an energy-intensive process. Thus, energy efficiency is highly important. Several stages of steelmaking involve combustion processes. One of the most energy-consuming processes in steelmaking is the slab reheating process in a reheat furnace (RF). The energy released by fuel combustion is used to heat steel slabs to their proper hot-rolling temperature. The steel slabs move through the reheat furnace passing the three stages of heating called: Preheating Zone (PZ), Heating Zone (HZ), and Soaking Zone (SZ) to finally leave the discharge door at a rolling temperature of 2375 °F. One way to improve a reheat furnace’s fuel consumption is by implementing oxygen-enriched combustion. This study investigates the implementation of oxygen-enriched combustion in a pusher-type reheat furnace. The increment of oxygen in the combustion process allows for increasing the furnace gas temperature. Consequently, the oxygen enrichment approach allows for the reduction of fuel injection. The principal goal of this investigation is to model the combustion-based on oxygen-enrichment and develop parametric studies of fuel injection rates. The different simulations aim to match the slab heat flux profile of the industrial reheat furnace pusher-type. Computational fluid dynamics are used to generate the slab heat flux distribution. To reach more uniform slab heating, oxygen and fuel ports were alternated. Also, injection angles were modified to optimize slab heating and avoid the impact of hot spots. Thermocouple readings of the industrial reheat furnace are compared to simulation results. The results determined that 40–45% fuel reduction can be achieved.

scholarly journals Analytical and Numerical Feasibility Analysis of a Contra-Rotary Ramjet Engine

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 163
Author(s):  
Tomasz Laube ◽  
Janusz Piechna
Keyword(s):  
Numerical Simulations ◽  
Stokes Equations ◽  
Analytical Data ◽  
Combustion Process ◽  
Flow Characteristics ◽  
Combustion Model ◽  
Similar Data ◽  
High Rotational Speed ◽  
Jet Engine ◽  
Ramjet Engine

A new idea for a contra-rotary ramjet engine is presented. To define the theoretical limits of the non-typical, contra-rotary ramjet engine configuration, its analytical model was developed. The results obtained from that model and the analytical results were compared with those received from numerical simulations. The main weakness of existing rotary ramjet engine projects is the very high rotational speed of the rotor required for achieving supersonic inlet flow. In this paper, a new idea for a contra-rotary ramjet engine (CORRE) is presented and analyzed. This paper presents the results of analytical analysis and numerical simulations of a jet engine system with two rotors rotating in opposite directions. Contra-rotating rotors generate a supersonic air velocity at the inlet to the compressor at two times slower rotor’s speed. To determine the flow characteristics, combustion process, and engine efficiency of the double-rotor engine, a numerical solution of the average Navier-Stokes equations was used with the k-eps turbulence model and the non-premixed combustion model. The results of numerical simulations of flow and the combustion process inside the contra-rotary jet engine achieving a shockwave compression are shown and compared with similar data for a single-rotor engine design and analytical data. This paper presents only the calculation results of the flow processes and the combustion process, indicating the advantages of the proposed double-rotor design. The results of the numerical analysis were presented on the contours and diagrams of the pressure and flow velocity, temperature distribution, and mass fraction of the fuel.

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.

Analysis of a HSDI Diesel Engine Intake System by Means of Multi-Dimensional Numerical Simulations: Influence of Non Uniform EGR Distribution

2006 ◽  
Author(s):  
Giuseppe Cantore ◽  
Carlo Arturo De Marco ◽  
Luca Montorsi ◽  
Fabrizio Paltrinieri ◽  
Carlo Alberto Rinaldini
Keyword(s):  
Diesel Engine ◽  
Numerical Simulations ◽  
Mutual Influence ◽  
Combustion Process ◽  
Engine Performance ◽  
Pollutant Emissions ◽  
Combustion Model ◽  
3D Analysis ◽  
Intake System ◽  
Hsdi Diesel Engine

In order to comply with stringent pollutant emissions regulations a detailed analysis of the overall engine is required, assessing the mutual influence of its main operating parameters. The present study is focused on the investigation of the intake system under actual working conditions by means of 1D and 3D numerical simulations. Particularly, the effect of EGR distribution on engine performance and pollutants formation has been calculated for a production 6 cylinder HSDI Diesel engine in a EUDC operating point. Firstly a coupled 1D/3D simulation of the entire engine geometry has been carried out to estimate the EGR rate delivered to every cylinder; subsequently the in-cylinder flow field has been evaluated by simulating the intake and compression strokes. Finally the spray and combustion processes have been studied accounting for the real combustion chamber geometry and particularly the pollutants formation has been determined by using a detailed kinetic mechanism combustion model. The 1D/3D analysis highlighted a significant cylinder to cylinder EGR percentage variation affecting remarkably the pollutant emissions formation, as evaluated by the combustion process simulations. A combined use of commercial and in-house modified codes has been adopted.

scholarly journals Numerical comparative analysis of the combustion process in an engine powered by CNG

2012 ◽  
Vol 148 (1) ◽  
pp. 62-70
Author(s):  
Ryszard MICHAŁOWSKI ◽  
Krzysztof MIKSIEWICZ ◽  
Marcin TKACZYK
Keyword(s):  
Fuel Injection ◽  
Combustion Process ◽  
Qualitative Evaluation ◽  
Fuel Mixture ◽  
Diesel Oil ◽  
Numerical Results ◽  
Combustion Model ◽  
Numerical Application ◽  
Gas Combustion ◽  
Natural Gas Combustion

This paper contains the analysis of Compressible Natural Gas combustion process in engine dedicated to diesel oil. The analysis was performed on the basis of the numerical results of two systems for methane dosing. The first simulation considers the CNG delivery into the suction manifold, and subsequent production of air-fuel mixture as well as separate combustion model of a homogenous mixture. The second simulation comprises a numerical application of the fuel injection directly into the combustion chamber. Therefore it is also a simulation of a combustion process. Among the numerical results conducted with the aid of Computational Fluid Dynamics the following parameters were selected for the combustion qualitative evaluation in terms of mechanical, heat and flow properties: fields of pressure and temperature, mass fraction of the fuel and turbulence intensity. All test were conducted on the engine adopted to be fed with CNG.

Effects of Damköhler Number on Methane/Oxygen Tubular Combustion Diluted by N2 and CO2

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Baolu Shi ◽  
Qingzhao Chu ◽  
Run Chen
Keyword(s):  
Reaction Time ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Mixing Time ◽  
Velocity Ratio ◽  
Inert Gases ◽  
Injection Velocity ◽  
Damkohler Number ◽  
Helical Structures ◽  
Damköhler Number

To fundamentally elucidate the mixing and its effects on the characteristics of methane/oxygen flame in a rapidly mixed tubular flame burner, experiments were conducted under various oxygen mole fractions and flow rates. Two inert gases of nitrogen and carbon dioxide were used, respectively. The inert gas was added to both the oxidizer and fuel slits to maintain the oxidizer/fuel injection velocity ratio near unity. Based on flow visualization, the mixing process around injection slits and that in the axial downstream were discussed. The Damköhler number (Da1), defined as the ratio of molecular mixing time to reaction time, was selected as a parameter to quantitatively examine the criterion for the establishment of tubular flame from low to ultrahigh oxygen mole fractions (0.21–0.86). The mixing around slit exit determined the tubular flame establishment. Due to a flow time between two neighboring injection slits of fuel and oxidizer, part of the fuel was mixed in the downstream swirling flow, resulting in luminous helical structures. Hence, the Damköhler number (Da2), defined as the flow to the reaction time ratio, was examined. Detailed observations indicated that when Da2 was smaller than unity, the flame was uniform in luminosity, whereas the flame was nonuniform when Da2 ≥ 1. The value of Da2 was about 1.5 times as Da1; however, they correspond to different mixing zones and Da2 can be more easily calculated. The differences in flame stability between N2 and CO2 diluted combustion were also studied.

1D Engine Simulation of a Small HSDI Diesel Engine Applying a Predictive Combustion Model

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
T. Cerri ◽  
A. Onorati ◽  
E. Mattarelli
Keyword(s):  
Diesel Engine ◽  
High Speed ◽  
Fuel Injection ◽  
Direct Injection ◽  
Combustion Process ◽  
Numerical Approach ◽  
Operating Conditions ◽  
Combustion Model ◽  
Full Load ◽  
Partial Load

The paper analyzes the operations of a small high speed direct injection (HSDI) turbocharged diesel engine by means of a parallel experimental and computational investigation. As far as the numerical approach is concerned, an in-house 1D research code for the simulation of the whole engine system has been enhanced by the introduction of a multizone quasi-dimensional combustion model, tailored for multijet direct injection diesel engines. This model takes into account the most relevant issues of the combustion process: spray development, air-fuel mixing, ignition, and formation of the main pollutant species (nitrogen oxide and particulate). The prediction of the spray basic patterns requires previous knowledge of the fuel injection rate. Since the direct measure of this quantity at each operating condition is not a very practical proceeding, an empirical model has been developed in order to provide reasonably accurate injection laws from a few experimental characteristic curves. The results of the simulation at full load are compared to experiments, showing a good agreement on brake performance and emissions. Furthermore, the combustion model tuned at full load has been applied to the analysis of some operating conditions at partial load, without any change to the calibration parameters. Still, the numerical simulation provided results that qualitatively agree with experiments.

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.

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