Simple Expression for the Emittance of H2O–CO2 Mixtures in Zonal Methods of Radiation Transfer Modeling

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Lisienko Vladimir ◽  
Malikov German ◽  
Titaev Alexander ◽  
Raymond Viskanta
Keyword(s):  
Radiation Transfer ◽  
Gas Mixtures ◽  
Simple Expression ◽  
Computational Time ◽  
Combustion Gas ◽  
Model Based ◽  
Total Emittance

A new and simple expression for the calculation of the total gas emittance of H2O–CO2 mixtures for modeling radiation transfer in combustion furnaces is presented. Its accuracy is established by comparing the predictions with those based on the well established the model based on Hitemp database. The computational time was found to be reduced by a factor of 3 in comparison to other methods for computing the total emittance of combustion gas mixtures.

Simple Expression for the Emittance of H2O-CO2 Mixtures in Zonal Methods of Radiation Transfer Modelling

2013 ◽  
Author(s):  
German Malikov ◽  
Alexandr Titaev ◽  
Vladimir Lisienko ◽  
Raymond Viskanta
Keyword(s):  
Radiation Transfer ◽  
Wide Band ◽  
Gas Mixtures ◽  
Simple Expression ◽  
Computational Time ◽  
Band Model ◽  
Combustion Gas ◽  
Transfer Modelling ◽  
Wide Band Model ◽  
Total Emittance

A new and simple expression for the calculation of the total gas emittance of H2O-CO2 mixtures for modeling radiation transfer in combustion furnaces is presented. Its accuracy is established by comparing the predictions with those based on the well established exponential wide band model. The computational time was found to be reduced by a factor of 10–30 in comparison to other methods for computing the total emittance of combustion gas mixtures.

scholarly journals Model-Based Control of Torque and Nitrogen Oxide Emissions in a Euro VI 3.0 L Diesel Engine through Rapid Prototyping

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1107
Author(s):  
Stefano d’Ambrosio ◽  
Roberto Finesso ◽  
Gilles Hardy ◽  
Andrea Manelli ◽  
Alessandro Mancarella ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Rapid Prototyping ◽  
Nitrogen Oxide ◽  
Thermal State ◽  
Pollutant Emissions ◽  
Computational Time ◽  
Nox Emissions ◽  
Model Based ◽  
Brake Mean Effective Pressure ◽  
The Impact

In the present paper, a model-based controller of engine torque and engine-out Nitrogen oxide (NOx) emissions, which was previously developed and tested by means of offline simulations, has been validated on a FPT F1C 3.0 L diesel engine by means of rapid prototyping. With reference to the previous version, a new NOx model has been implemented to improve robustness in terms of NOx prediction. The experimental tests have confirmed the basic functionality of the controller in transient conditions, over different load ramps at fixed engine speeds, over which the average RMSE (Root Mean Square Error) values for the control of NOx emissions were of the order of 55–90 ppm, while the average RMSE values for the control of brake mean effective pressure (BMEP) were of the order of 0.25–0.39 bar. However, the test results also highlighted the need for further improvements, especially concerning the effect of the engine thermal state on the NOx emissions in transient operation. Moreover, several aspects, such as the check of the computational time, the impact of the controller on other pollutant emissions, or on the long-term engine operations, will have to be evaluated in future studies in view of the controller implementation on the engine control unit.

scholarly journals Performances of different DFT functionals to calculate the anodic limit of fluorinated sulphonyl-imide anions for lithium cells

2021 ◽  
Vol 2090 (1) ◽  
pp. 012078
Author(s):  
A Paolone ◽  
S Brutti
Keyword(s):  
Ionic Liquids ◽  
Lithium Batteries ◽  
Basis Set ◽  
Basis Sets ◽  
Computational Time ◽  
Generalized Gradient ◽  
Neutral Species ◽  
Generalized Gradient Approximation ◽  
Model Based ◽  
Computationally Expensive

Abstract In this paper we investigated the calculation of the anodic limit of two anions of ionic liquids, largely used as electrolyte of lithium batteries. Starting from a model based on calculations performed on single ions at the MP2 level of theory, we showed that the matching between calculation and experiments decreases while using more expanded basis set with respect to 6-31G**, possibly because of the destabilization of the neutral species when larger basis sets are considered. Additionally, in order to decrease the computational time, the performances for the calculation of the anodic limit obtained by means of a series of DFT functionals with increasing level of complexity (from the Generalized Gradient Approximation to the Range Separated Hybrid meta-Generalized Gradient Approximation) were compared. Overall, the best performing functionals are BMK, ωB97M-V and MN12-SX, while acceptable results can be obtained by M06-2X, M11, M08-HX and M11-L. Some less computationally expensive functionals, like CAM-B3LYP and ωB97X-D, also provide reasonable values of the anodic limit.

Mathematical Models for Model-Based Control in Offshore Pipelay Operations

2009 ◽  
Author(s):  
Gullik A. Jensen ◽  
Thor I. Fossen
Keyword(s):  
Mathematical Models ◽  
Dynamic Models ◽  
Controller Design ◽  
Computational Time ◽  
Beam Model ◽  
Time Dynamic ◽  
Model Based ◽  
On Line ◽  
Stability And Accuracy ◽  
Control Application

This paper considers mathematical models for model-based controller design in offshore pipelay operations. Three classes of models for control design are discussed, real-world models suitable for controller design verification, controller and observer models which are used on-line in the control system implementation. The control application place requirements on the model with respect to the computational time, dynamic behavior, stability and accuracy. Models such as the beam model, two catenary models, as well as general finite element (FE) models obtained from computer programs were not able to meet all of the requirements, and two recent dynamic models designed for control are presented, which bridge the gap between the simple analytical and more complex FE models. For completeness, modeling of the pipelay vessel, stinger and roller interaction, soil and seabed interaction and environmental loads are discussed.

Characterization of the PSD of activated carbons from peach stones for separation of combustion gas mixtures

Adsorption ◽  
2011 ◽  
Vol 17 (5) ◽  
pp. 853-861 ◽  
Author(s):  
Débora A. Soares Maia ◽  
J. C. Alexandre de Oliveira ◽  
Juan Pablo Toso ◽  
Karim Sapag ◽  
Raul H. López ◽  
...  
Keyword(s):  
Activated Carbons ◽  
Gas Mixtures ◽  
Combustion Gas

Mathematical Modeling of Direct Flame Impingement Heat Transfer

2006 ◽  
Author(s):  
German Malikov ◽  
Vladimir Lisienko ◽  
Yuri Malikov ◽  
John Wagner ◽  
Harry Kurek ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Radiation Transfer ◽  
Convective Diffusion ◽  
Heat Fluxes ◽  
Nox Emissions ◽  
Gas Temperature ◽  
Fine Grid ◽  
Combustion Gas ◽  
Calculation Domain ◽  
Diffusion Transfer

Direct flame impingement (DFI) furnaces consist of large arrays of high velocity combusting jets with temperatures up to 1700 K and impinging on complex configuration surfaces of the work pieces. This results in serious convergence problems DFI modeling and computational efforts. A new method of modeling convective-diffusion transfer (CDT) and zone radiation transfer (RT) employing different calculation schemes with a multi-scale grid is presented. Relatively coarse grid calculation domain allows use of conservative and accurate zone radiation transfer method with only modest computational efforts. A fine grid calculation domain is used to predict convective -diffusion transfer for a representative furnace section, containing a small number of jets that allows to significantly decrease the computer time. The main difficulty of coupling between convective-diffusion transfer (CDT) and radiation heat transfer numerical computations is successfully overcome using a relatively simple algorithm. The method allows one to model the physicochemical process taking place in the DFI and reveals as well as explains many features that are difficult to evaluate from experiments. The results were obtained for high velocities (up to 400 m/s) and high firing rates. Maximum (available for natural gas-air firing) total heat fluxes up to 500 kW/m2 and convective heat fluxes of up to 300 kW/m2 were obtained with relatively 'cold' refractory wall temperatures not exceeding 1300 K. The combustion gas temperature range was 1400-1700 K. A simplified analysis for NOx emissions has been developed as post-processing and shows extremely low NOx emissions (under 15 ppm volume) in DFI systems. Good agreement between measurements and calculations has been obtained. The model developed may be regarded as an efficient tool to compute and optimize industrial furnaces designs in limited time.

SLW-1 Modeling of Radiative Heat Transfer in Non-Isothermal Non-Homogeneous Gas Mixtures With Soot

2010 ◽  
Author(s):  
Vladimir P. Solovjov ◽  
Denis Lemonnier ◽  
Brent W. Webb
Keyword(s):  
Radiative Heat ◽  
Gaseous Medium ◽  
Good Accuracy ◽  
Radiation Transfer ◽  
Gas Mixtures ◽  
Optimal Choice ◽  
Distribution Functions ◽  
Gas Absorption ◽  
Individual Species ◽  
Benchmark Solutions

The Spectral Line Weighted-sum-of-gray-gases (SLW) model consisting only of a single gray gas and of one clear gas is developed as an efficient spectral method for modeling radiation transfer in gaseous medium. The model is applied here in prediction of radiative transfer in non-isothermal and non-homogeneous gas mixtures with non-gray soot. The absorption spectrum of the gas mixture and soot particles is treated as a spectrum of a single effective gas reducing the problem to the simplest case of the SLW model with a single gray gas. Good accuracy can be achieved by the optimal choice of the model’s gray gas absorption coefficient and its weight by application of the Absorption-Line Blackbody Distribution Functions of individual species in the mixture calculated with a high-resolution spectral database. The SLW-1 model is validated by comparison with benchmark solutions using the Line-by-Line method, the SLW method with a large number of gray gases, and the SNB model.

Prediction of Radiative Transport in Nonhomogeneous Combustion Gas Mixtures With a Wide Band G(K) Model

2013 ◽  
Author(s):  
Liping Liu ◽  
Jing He
Keyword(s):  
Radiative Transfer ◽  
Narrow Band ◽  
Gaussian Quadrature ◽  
Wide Band ◽  
Gas Mixtures ◽  
Source Distribution ◽  
Distribution Model ◽  
Band Model ◽  
Radiative Transport ◽  
Combustion Gas

A wide band cumulative absorption coefficient distribution, g(k), model is adopted to predict radiative transport in combustion gas mixtures. Prior research has demonstrated similar accuracy of the model to the statistical narrow-band model and superiority to the exponential wideband model under isothermal and homogeneous conditions. This study aims to assess its usefulness in nonhomogeneous media. Sample calculations are performed in a 1D planar slab containing H2O/CO2 mixtures. The six-flux discrete ordinate method (S6-DOM) is employed to solve the radiative transfer equation (RTE), followed by an eight-point Gaussian quadrature of moments with zeroth-order fit. Predictions on the radiative source distribution along the slab and the net radiative flux at the walls are compared to the benchmark line-by-line calculation (LBL) and the statistical narrow-band correlated-k distribution model using the 7-point Gauss-Lobatto quadrature scheme (SNBCK-7). The differences between the g(k) model and LBL are below 5% for a large domain of the layer, with a CPU reduction by a factor of over 30 compared to SNBCK-7 and on the order of 104∼105 compared to LBL. The wide band g(k) model shows significant promise as an accurate and efficient tool to predict radiative transfer in nonhomogenerous media for combustion and fire simulations.

scholarly journals Improvement of Fast Model-Based Acceleration of Parameter Look-Locker T1 Mapping

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5371
Author(s):  
Michał Staniszewski ◽  
Uwe Klose
Keyword(s):  
T1 Mapping ◽  
Region Of Interest ◽  
Computational Time ◽  
Single Shot ◽  
Mean Values ◽  
Model Based ◽  
Fitting Procedure ◽  
Novel Method ◽  
Space Data ◽  
Brain Measurements

Quantitative mapping is desirable in many scientific and clinical magneric resonance imaging (MRI) applications. Recent inverse recovery-look locker sequence enables single-shot T1 mapping with a time of a few seconds but the main computational load is directed into offline reconstruction, which can take from several minutes up to few hours. In this study we proposed improvement of model-based approach for T1-mapping by introduction of two steps fitting procedure. We provided analysis of further reduction of k-space data, which lead us to decrease of computational time and perform simulation of multi-slice development. The region of interest (ROI) analysis of human brain measurements with two different initial models shows that the differences between mean values with respect to a reference approach are in white matter—0.3% and 1.1%, grey matter—0.4% and 1.78% and cerebrospinal fluid—2.8% and 11.1% respectively. With further improvements we were able to decrease the time of computational of single slice to 6.5 min and 23.5 min for different initial models, which has been already not achieved by any other algorithm. In result we obtained an accelerated novel method of model-based image reconstruction in which single iteration can be performed within few seconds on home computer.

Sign in / Sign up

Export Citation Format

Share Document