Steady Flamelet Model Research Articles

Effects of Hydrogen on Ammonia/Methane/Air Combustion in a Can-type Combustor

In recent years, the importance of blending traditional methane gas with alternative fuels in combustion to reduce emissions has gained increasing recognition. Existing literature has demonstrated the successful operation of ammonia and hydrogen as fuels in diesel engines. However, there is still insufficient information regarding the combustion of methane in combination with ammonia and hydrogen. This paper investigates the effects of replacing ammonia with hydrogen in blends consisting of 70% CH4 and 30% NH3, with hydrogen substitution levels of 0%, 10%, 30%, 50%, 70%, and 90%. The simulation was carried out using the SST k-ω turbulence model and steady diffusion flamelet model. Calculations using Okafor-mech to predict the emission characteristics were also attempted to determine concentration values more accurately. Results show that as the proportion of hydrogen in the blended fuel increases, the maximum temperature rises by 29.28 K. There is an increase in emissions of carbon dioxide and carbon monoxide, while nitrogen oxide emissions decrease.

Investigation of Thermal Radiation, Atomization Air, and Fuel Temperature Effects on Liquid Fuel Combustion

Abstract The purpose of the present study is to investigate the effects of radiative heat transfer, atomization air temperature and mass flowrate, and fuel initial temperature on liquid diesel fuel (C16H34) combustion. Fuel is injected by an airblast atomizer inside a model cylindrical combustion chamber. Geometry of the airblast atomizer is modeled in detail so that its impacts on droplet breakup and flow formation are accurately considered. Evaporating fuel spray is simulated by the discrete phase model based on the Eulerian–Lagrangian approach. Turbulent viscosity is numerically computed by the realizable k–ɛ turbulence model while the discrete ordinates model and the steady flamelet model are applied for modeling the radiative heat transfer and combustion, respectively. NO species concentrations are achieved using post-processing. It turns out that neglecting thermal radiation in well-atomized spray combustion only affects high-temperature zones by increasing the axial temperature values of the mixture by almost 8%. Thermal radiation has an imperative effect on producing NO species. Without considering thermal radiation, axial NO concentration becomes almost doubled. Augmentation in mass flowrate and temperature values of atomization air enhances spray formation and combustion efficiency by increasing the evaporation rate. Changing the fuel temperature from 300 K to 325 K rises the total temperature at the end of the centerline of the model combustion chamber by 9.8%. It is shown that increasing the fuel’s initial temperature is not a suitable choice compared to enhancing the temperature and mass flowrate of the atomization air.

Non-premixed combustion and NOX emission characteristics in a micro gas turbine swirl combustor fueled by methane and ammonia at various heat loads

In comparison to methane (CH4), ammonia (NH3) is considered a potential carbon-free alternative fuel that can reduce greenhouse gas emissions. But a principal concern is the generation of elevated nitrogen oxide (NOX) emissions from NH3 flame. In this study, the detailed reaction mechanisms and thermodynamic data of CH4 oxidation and NH3 oxidation were performed using the steady and unsteady flamelet models. After validation of the turbulence model, the combustion and NOX emission characteristics of CH4/air and NH3/air non-premixed flames in a micro gas turbine swirl combustor under a series of identical heat loads were numerically investigated and compared. The present results show that the high-temperature zone of the NH3/air flame migrates more rapidly toward the outlet of the combustion chamber than that of the CH4/air flame as the heat load increases. The average NO, N2O, and NO2 emission concentrations at all heat loads from NH3/air flame are respectively 6.12, 161.05 (given the very low N2O emission concentration from CH4/air flame), and 2.89 times higher than those from CH4/air flame. There are correlation trends between some parameters (e.g. characteristic temperature and OH emissions) with the variation of the heat load, and the relevant parameters can be tracked to predict the emission trends after changing the heat load.

산업용 가스터빈 연소기에서 연소 모델에 따른 수소 화염의 역화 특성 비교연구

Four different combustion models were investigated to test hydrogen flame flashback prediction capability in an industrial gas turbine combustor. The applied combustion models are (i) flamelet generated manifold -finite rate (FGM-FR) model, (ii) flamelet generated manifold - turbulent flame speed (FGM-ST) model, (iii) steady diffusion flamelet (SDF) model, and (iv) eddy dissipation concept (EDC) model. Two conditions were simulated which showed experimentally non-flashback and flashback respectively. For the experimentally non-flashback condition, FGM-ST, SDF, and EDC model simulations show flashback, while FGM-FR did not show flashback. For the experimentally flashback condition, FGM-ST, SDF, and EDC model simulations show flashback, while FGM-FR did not show flashback. To be able to predict hydrogen-flame flashback, further investigation on combustion model are needed.

Optimization of a gas turbine model combustor due to variations in geometrical characteristics of stabilizing air jets

• Interaction of input parameters (diameter, angle, and position) is considered. • ANN is used to extract fitness (trained) function for GA. • NOx, CO, and PF are improved by up to 11.31%, 2.88%, and 21.07%, respectively. • Soot is decreased by up to 24.46%. The main purpose of this paper is to optimize the objective parameters in a gas turbine model combustor. These parameters include N O x and C O pollutants as well as pattern factor. C O is based on a maximum produced value in the model combustor. To optimize the objective parameters, the input characteristics (such as diameter, angle, and position of the stabilizing air jets) are varied. Simulation of the combustion process comprises turbulent flow, combustion, radiative heat transfer, and fuel injection modeling. The models employed for this simulation, based on RANS approach, are realizable k - ε for flow turbulence, steady flamelet model for combustion, discrete ordinates model for radiative heat transfer, and Eulerian-Lagrangian approach for fuel injection. A diesel fuel (C 10 H 22 ) is used in the model combustor and N O x modeling is conducted via post-processing. Artificial neural network is applied to gain an approximated trained function based on results and input geometrical characteristics. Data for training the artificial neural network is generated by means of design of experiments. For finding the optimum point, genetic algorithm is utilized. The obtained neural network function is applied to genetic algorithm so as to extract the optimum points. Since there is more than one objective parameter a set of optimum points is obtained which is called the Pareto front. Using multiple-criteria decision making method (LINMAP model), the final optimum point is achieved. The optimum point shows that the amounts of N O x , C O , and pattern factor are improved by up to 11.31 %, 2.88 %, and 21.07 %, respectively. The value of soot which is not a part of optimization is also improved by up to 24.46 %.

Validation of a coupled 3D CFD simulation model for an oxy-fuel cross-fired glass melting furnace with electric boosting

Glass furnaces represent a continuous challenge for CFD simulations, which is attributed to the complex description of multiple phases: the turbulent gas phase, raw materials from a solid glass batch and the laminar liquid phase of the glass melt. Prevalence of unsuitable oxy-fuel combustion models, like the eddy-dissipation model, and the lack of advanced coupling methods for the coupling of combustion chamber and glass tank domains have been identified as research gaps in glass furnace simulations. These are tackled in a 3D CFD simulation model for an oxy-fuel glass furnace with electric boosting by introducing two significant improvements compared to previous approaches: (1) The partially-premixed steady diffusion flamelet model in combination with a skeletal25 reaction mechanism was used for combustion modelling. (2) An advanced iterative coupled simulation method is presented, which introduces damping of the solution and a rigorous termination condition. By employing the presented models, the respective temperatures in the combustion chamber and the glass tank were predicted within less than 1.93% and 3.81% of the experimental data.

Numerical Simulation of Turbulent Non-premixed Combustion Processes for Methane and Dimethyl Ether Binary Fuels.

The C1ε = 1.6 standard k – ε equation combined with the steady flamelet model was applied to a methane/dimethyl ether swirl combustion field, and the effects of the dimethyl ether (DME) blending ratio and operating pressure on the flame behavior, including species variation, reaction zone behavior, and flame entrainment, were investigated. The results demonstrated that selected models could better reproduce the trends of the experimental measurements. The downstream reaction zone achieved better calculation accuracy than the outer shear layer of the first recirculation zone. The addition of DME accelerated the accumulation process of H2, O, H, and OH radicals. The intermediate radical CH2O was rapidly developed by the influence of the H extraction rate under a constant fuel volume flow rate. The reaction zone dimensions were approximately linearly and positively correlated with the DME blending ratio, whereas flame entrainment expressed a lower DME concentration dependence in the high-DME mass-dominated system. The operating pressure significantly impacted the distribution of reactive radicals in the turbulent flame; meanwhile, the flame and reaction zone length showed nonlinear inverse behavior with pressure variation, while the thickness of the reaction zone was always linearly and negatively correlated with pressure. Moreover, the peak flame entrainment rate also experienced a nonlinear decline with pressure elevation; however, the peak positions were not sensitive to pressure fluctuation. Concurrently, the response surface functions for the reaction zone dimensions were established covering the range of 0–1 for the DME blending ratio and 1–5 atm operating pressure, which could provide assistance for combustion condition optimization and combustion chamber design.

CFD modelling and numerical investigation of a large marine two-stroke dual fuel direct injection engine

ABSTRACT This study aims at developing a CFD model for large marine two-stroke dual fuel engine with gaseous fuel direct injection at high pressure. For the gaseous fuel, the shock tube theory and the pseudo-diameter concept are employed to model the injection, jet penetration and air entrainment processes, whereas its non-premixed combustion is represented by a steady diffusion flamelet model along with a pilot fuel ignition kernel. Following this model validation, a large marine two-stroke dual fuel engine closed cycle is simulated for both the gas and diesel modes at 75% load, and the involved phenomena are comparatively assessed. The derived results demonstrate that the gas mode combustion takes place in lower maximum temperature and leaner conditions compared to the diesel mode, resulting in lower NOx emissions. This study is expected to benefit the development of future engine designs and the engine settings optimisation for reducing emissions and increasing efficiency.

Analysis of flow-field in a dual mode ramjet combustor with boundary layer bleed in isolator

A two-dimensional Reynolds averaged Navier Stokes (RANS) simulation of a dual mode ramjet (DMRJ) combustor is performed, modeling the University of Michigan dual-mode combustor experimental setup operating in reacting mode with different equivalence ratios (φ). The simulations are carried out using a k-ω SST turbulence model and a steady diffusion flamelet model for non-premixed combustion. Air enters the isolator at Mach 2.2, stagnation pressure and temperature of 549.2 kPa and 1400 K respectively. Hydrogen is injected transverse to the flow direction and upstream of the cavity flame holder to simulate ramjet (φ = 0.29) and scramjet (φ = 0.19) modes of operation. Wall static pressure plots are used to validate numerical results against experimental data. Analysis of flow separation in ramjet mode due to the presence of a shock train in the isolator is carried out by means of numerical Schlieren images overlapped with contours of negative axial velocity, showing the effects of shock wave boundary layer interaction (SWBLI). Active control through wall normal boundary layer bleed in the separated flow region is implemented, which weakens the shock train and moves it downstream closer to the cavity. Bleed results in an improved stagnation pressure recovery in ramjet mode, with a marginal increase in combustion efficiency.

Numerical Investigation of Combustion Instabilities in a Single-Element Lean Direct Inject Combustor Using Flamelet Based Approaches

Abstract In this paper, high-fidelity large eddy simulations (LES) along with flamelet-based combustion models are assessed to predict combustion dynamics in low-emission gas turbine combustor. A model configuration of a single-element lean direct injection (LDI) combustor from Purdue University (Huang et al., 2014, “Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor,” 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, OH, July 28–30.) is used for the validation of simulation results. Two combustion models based on the flamelet concept, i.e., steady diffusion flamelet (SDF) model and flamelet generated manifold (FGM) model are employed to predict combustion instabilities. Simulations are carried out for two equivalence ratios of φ = 0.6, and 0.4. The results in the form of mode shapes, peak to peak pressure amplitude and power spectrum density (PSD) are compared with the experimental data of Huang et al. (2014, “Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor,” 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, OH, July 28–30.). The effect of variation in the time-step size hence acoustic courant number is studied. Further, two numerical solver options, i.e., pressure-based segregated solver and pressure-based coupled solver, are used to understand their effect on the solution convergence regarding the number of time-steps required to reach the limit cycle of the pressure oscillations. A truncated (half) domain simulation is performed by applying an appropriate acoustic impedance boundary condition at the truncated location. Overall, the simulation results compare well with the experimental data and trends are captured accurately in all simulations. It builds confidence in flamelet-based combustion models for the use in combustion instability modeling which is traditionally done using finite rate chemistry models based on reduced kinetics.

Hierarchical model form uncertainty quantification for turbulent combustion modeling

All models invoke assumptions that result in model errors. The objective of model form uncertainty quantification is to translate these assumptions into mathematical statements of uncertainty. If each assumption in a model can be isolated, then the uncertainties associated with each assumption can be independently assessed. In situations where a series of assumptions leads to a hierarchy of models with nested assumptions, physical principles from a higher-fidelity model can be used to directly estimate a physics-based uncertainty in a lower-fidelity model. Turbulent nonpremixed combustion models fall into a natural hierarchy from the full governing equations to Conditional Moment Closure to flamelet-like models to thermodynamic equilibrium, and, at each stage of the hierarchy, a single assumption can be isolated. In this work, estimates are developed for the uncertainties associated with each assumption in the hierarchy. The general method identifies a trigger parameter that can be obtained with information only from the lower-fidelity model that is used to estimate the error in the lower-fidelity model using only physical principles from the higher-fidelity model. Starting from the lowest fidelity model, the trigger parameters identified in this work are the product of a chemical time scale and the scalar dissipation rate for the equilibrium chemistry model, which characterizes the errors associated with neglecting finite-rate chemistry and transport; the reciprocal of the product of a generalized Lagrangian flow time and the scalar dissipation rate for the steady flamelet model, which characterizes the errors associated with neglecting flow history effects; and the relative magnitude of the conditional fluctuations for Conditional Moment Closure. The approach is applied in LES to a turbulent nonpremixed simple jet flame to quantify the errors associated with the equilibrium chemistry model and the steady flamelet model. The results indicate that errors associated with neglecting finite-rate chemistry and transport in the equilibrium chemistry model are dominant upstream while errors associated with neglecting flow history in the steady flamelet model become more important downstream.

Numerical model incorporating different oxidizer in a reheating furnace fired with natural gas

The call for an increase in efficiency and performance leads to constant developments of furnaces and burners. For this purpose, a propagated application of different burner types, often operating with pure oxygen or oxygen enrichment, can be determined. As a consequence numerical models have to be adapted incorporating industrial needs. This work has developed an approach based on the spatial separation of the whole domain into parts, capable of various oxidizer and fuels to be considered. Each of these parts operates with a single oxidizer and fuel each. The advantages are possible improvements on each small part separately, decreasing computational effort needed. Furthermore, different numerical models, for e.g. combustion and turbulence, can be applied. Moreover, the steady flamelet model (SFM), limited to the usage of a single oxidizer and fuel, can be applied. The results, using the SFM have been compared to the eddy dissipation (EDM) and eddy-dissipation concept model (EDC). Clear differences in the highly reactive areas become obvious using the different combustion models. Though the influence on the remaining combustion chamber is low. Consequently, the heating characteristic of the tubes revealed negligible differences. The calculated temperatures inside the combustion chamber and the transient tube temperature have been compared to measurements at the real size furnace disclosing a high consistency. Thus, the presented approach presents a good alternative for researchers and operators to investigate real-size furnaces.

Numerical Investigation of Coaxial GCH4/LOx Combustion at Supercritical Pressures

ABSTRACT This article aims to numerically investigate the combustion phenomenon of coaxial gaseous CH4/LOx at supercritical pressures. The choice of turbulence model, real gas model, and chemical kinetics model are the critical parameters in numerical simulations of cryogenic combustion at high pressure. At this supercritical operating pressure, the ideal gas law does not remain valid for such cases. Therefore, we have systematically carried out a comparative study to analyze the importance of real gas models, turbulence parameters, and chemical kinetics at such conditions. The comparison of real gas models with the NIST database reveals better conformity of SRK (Soave Redlich Kwong – Equation of State (EoS)) model predictions with the database. Further, the computed results indicate that the Standard k-ε turbulence model with modified constant (Cε1 = 1.4) captures the better flame shape and temperature peak position compared to other RANS based turbulence models while invoking the non-premixed steady β-PDF flamelet model for simulating the combustion process. Furthermore, a comparative study comparing two different chemical kinetics models indicates that the reduced Jones-Lindstedt mechanism (JL-R) can accurately predict the flame characteristics with the least computational cost. Finally, we have studied the effect of chamber pressure and LOx inlet temperature on the flame characteristics. The flame characteristics exhibit a strong sensitivity toward the chamber pressure due to the weakening of the pseudo-boiling effect with an increase in pressure. As a consequence of lower turbulent rates of energy and mass transfer through the transcritical mixing layer, the flame spreading becomes narrower at elevated pressure and temperature, thereby yielding an increased flame length at transcritical conditions.

Fast and accurate CFD-model for NOx emission prediction during oxy-fuel combustion of natural gas using detailed chemical kinetics

Accurate prediction of NOx emission is essential in designing combustion devices and troubleshooting of existing ones. The aim of this work is to investigate the sensitivity of NOx formation during the combustion of natural gas with oxygen using a numerically inexpensive computational fluid dynamics model. To this end, an industrial jet burner was experimentally and numerically analysed for NOx formation at 600 kW controlled at 1320 and 1450°C during the combustion of natural gas with pure oxygen and oxidizer mixtures containing up to 10%v nitrogen. Two mixture-fraction based and two classical species transport models were investigated for their ability to: (1) predict the flame shape and temperature, (2) calculate the OH and CH emissions driving the NOx formation, and (3) fast and accurately predict the NOx emissions during oxy-fuel combustion and during the presence of low nitrogen amounts in the oxidizer. The study shows that the widely-used steady-flamelet model fails to correctly predict the flame shape and temperature, due to a too low velocity difference between the oxidizer and the fuel. It is highlighted that only the partially-premixed steady flamelet model predicted the flame shape and the NOx formation rates adequately, fitting the experimental and numerical data closely. Moreover, the shear rate in the annular gap was identified as a crucial parameter for the applicability of mixture fraction-based models. Species transport models should be used for validity checks but they disqualify as fast-solving alternatives due to their high computational demand (EDC) or lack of detailed chemistry interaction (EDM).

Multi-dimensional and transient effects on flamelet modeling for turbulent pulverized coal combustion

The transport along mixture fraction iso-surfaces is generally denoted as multi-dimensional effect, which is not considered in the classical one-dimensional (1D) flamelet model. This work investigates multi-dimensional and transient effects on flamelet modeling for turbulent pulverized coal combustion. To this end, instantaneous flamelets are extracted from a fully resolved 3D DNS database generated for a turbulent pulverized coal flame with a 33 array of particles. At first, the importance of transport along the iso-mixture fraction surface is analyzed based on the flamelet regime diagram. By this means, the flamelet regime of the local combustion is clarified. Then, the relevance of transient effects is investigated using budget analyses for transient terms in both physical space and composition space. Particularly, the significance of the Eulerian and Lagrangian transient terms is quantified. It is found that compared to the other transient processes, the transient change in the inner flame structure, i.e., the Lagrangian transient process, is dominant. Interestingly, the budget analyses show that the Lagrangian transient term can be partially recovered by the steady flamelet model. The findings obtained from the flamelet regime diagram and the budget analyses are consistent with the flamelet solutions where the multi-dimensional and transient terms are included in/excluded from the flamelet equations. The generalized flamelet equations including both multi-dimensional and transient terms can effectively reproduce the instantaneous flamelets in the DNS. Finally, a priori analyses are conducted to evaluate the multi-dimensional and transient effects on the final performance of the flamelet model. Overall, the a priori results are consistent with findings obtained from the budget analyses.

Computational investigations of the coupling between transient flame dynamics and thermo-acoustic instability in a self-excited resonance combustor

Combustion instability due to thermo-acoustic interactions is a critical combustion problem that requires a thorough understanding because of its adverse impact on stable and reliable operation of combustors in high-speed propulsion devices like gas turbines and rockets. This work conducts computational investigations of the coupling between the transient flame dynamics such as the ignition delay and local extinction and the thermo-acoustic instability developed in a self-excited resonance combustor to gain deep insights into the mechanisms of thermo-acoustic instability. A 2D modelling framework that employs different flamelet models (the steady flamelet model and the flamelet/progress variable approach) is developed to enable the examination of the effect of the transient flame dynamics caused by the strong coupling of the turbulent mixing and finite-rate chemical kinetics on the occurrence of thermo-acoustic instability. The models are validated by using the available experimental data for the pressure signal. Parametric studies are performed to examine the effect of the occurrence of the transient flame dynamics, the effect of artificial amplification of the Damköhler number, and the effect of neglecting mixture fraction fluctuations on the predictions of the thermo-acoustic instability. The parametric studies reveal that the occurrence of transient flame dynamics has a strong influence on the onset of the thermo-acoustic instability. Further analysis is then conducted to localise the effect of a particular flame dynamic event, the ignition delay, on the thermo-acoustic instability. The reverse effect of the occurrence of the thermo-acoustic instability on the transient flame dynamics in the combustor is also investigated by examining the temporal evolution of the local flame events in conjunction with the pressure wave propagation. The above observed two-way coupling between the transient flame dynamics (the ignition delay) and the thermo-acoustic instability provides a plausible mechanism of the self-excited and sustained thermo-acoustic instability observed in the combustor despite the fact that the results are obtained from 2D simulations. The same analysis is expected to be extensible to fully 3D simulations.

Direct Numerical Simulation of turbulent nonpremixed “cool” flames: Applicability of flamelet models

“Cool” flames result from the coupling of low-temperature chemistry with molecular transport. These flames have been experimentally and computationally observed under laminar flow conditions but have not been isolated under turbulent flow conditions. In this work, a skeletal n-heptane chemical mechanism including low-temperature chemistry is used to conduct two-dimensional Direct Numerical Simulations (DNS) of nonpremixed “cool” flames subjected to unsteady, two-dimensional flow initialized from a plane of isotropic turbulence. Like conventional “hot” flames, at high Damköhler numbers, these “cool” flames are found to be adequately described by a steady flamelet model. However, at low Damköhler numbers, both nonpremixed and premixed behavior is observed locally. When the combustion is locally nonpremixed, these “cool” flames can be described by the unsteady flamelet model only if the correct scalar dissipation rate profile and associated boundary conditions are considered.

Assessment of steady and unsteady flamelet models for MILD combustion modeling

Moderate or intense low-oxygen dilution (MILD) combustion is a novel combustion technology with the comparable chemical and turbulent mixing timescales. In the most of literatures, relatively expensive volume-based models are recommended for this combustion regime while this regime is not completely idealized homogenized reactor and nor strong flamelet like. This paper is focused on the assessment of the lower cost, flamelet approach for MILD condition. In this way, simplifying JHC burner of Dally et al. is considered to model using RANS approach. The effects of inclusion of unity versus non-unity Lewis numbers, radiation heat transfer, and various scalar dissipation rates are evaluated. Results show that the flamelet model may not be totally rejected for the MILD condition because it could still capture flame characteristics relatively acceptable. Choosing an appropriate scalar dissipation rate value is discussed for single flamelet and higher values are recommended by O2 increment. Moreover, considering non-unity Lewis numbers improved species concentration at the jet centerline for low O2 levels. Furthermore, the unsteady flamelet model with radiation had a better prediction for NOx especially for higher O2 Levels.

Numerical study on supersonic combustion of hydrogen and its mixture with Ethylene and methane with strut injection

In this paper, supersonic combustion and flow field of hydrogen and its mixture with ethylene and methane from strut injections in a Mach 2 supersonic flow are studied numerically. The fuel mixture of hydrogen, methane and ethylene represents the major products of pyrolysis of hydrocarbon fuels with large molecules such as kerosene as it acts as coolant and flows through cooling channels and absorbs heat. Detached Eddy Simulation with a reduced kinetic mechanism and steady flamelet model are applied to simulate turbulent combustion. The calculated temperature profiles of hydrogen are compared to the experimental results of DLR supersonic combustor for validation of the present numerical method. The supersonic combustion flows associated with shock waves, turbulent vortices and flame structures are studied. With addition of methane and ethylene, the flame zone moves further downstream of the strut and the maximum flow temperature at chamber exit decreases by 200 K. With analysis of total temperature ratios, it is found that combustion efficiency for hydrogen combustion is 0.91 and it decreases to 0.78 for the fuel mixture. The calculation of ignition delay time and flame speed reveals that fuel mixture of hydrogen and hydrocarbons has considerably larger delay time and smaller flame speed, that contributes to the weakened flame zone and lower combustion efficiency.

Characterization of the temperature distribution on steel tubes for different operating conditions in a reheating furnace using CFD and three different measuring methods

In the steel industry, there are a number of common methods for determining the temperature distribution of steel goods. In a reheating furnace, knowledge of the inlet and the outlet temperatures is of great importance since these temperatures have a significant effect on both the gas input to the furnace as well as downstream processes. Excessive temperature fluctuations can also be prevented, ensuring uniform temperature distribution, close to the target temperature. In this work, three different measuring methods, differing in their measuring principles, are compared and validated using computational fluid dynamics (CFD). These methods include a two-colour pyrometer and an infrared camera (IC), which measures the surface temperature of the tubes. Furthermore, local temperatures are evaluated using the results of a test tube equipped with several thermocouples. In order to verify the measurements and the CFD simulations, an additional operating condition is taken into account. The operating conditions differ in their gas distribution to the individual zones, and, thus, in the heating characteristics of the tubes. The numerical model used is based on both a steady and a transient simulation, keeping the calculation time low. In the steady state simulation, the steady flamelet model (SFM), using the detailed CH4 mechanism skeletal25, serves to characterise combustion. The heating of the tubes is depicted by means of the transient simulation. These different methods of measuring temperature show good agreement with the CFD results, and their respective advantages and disadvantages are apparent.