Lean Blowout Predictions of a Non-Premixed V-Gutter Stabilized Flame Using a Damkohler Number Methodology

2011 ◽  
Author(s):  
Hui-ru Wang ◽  
Jie Jin
Keyword(s):  
Experimental Data ◽  
Number Fields ◽  
Inlet Temperature ◽  
Damkohler Number ◽  
Atmosphere Pressure ◽  
Inlet Velocity ◽  
Lean Blowout ◽  
Cell Basis ◽  
Damköhler Number ◽  
A Cell

The lean blowout stability of a non-premixed, V-gutter stabilized flame was investigated using a Damkohler number methodology. The flow and chemical timescales were extracted from the reacting RANS CFD results on a cell-by-cell basis. Assessment of three representative definitions of flow and chemical timescales for Damkohler number based on different blowout mechanisms was performed. By examining the Damkohler number fields, the structure of the flame or the possibility of blowout can be estimated. The results demonstrated that a distinct transition between stable and unstable flames was observed by decreasing the fuel-air ratio or increasing the inlet velocity at atmosphere pressure and an inlet temperature of 537K. All three definitions can predict the lean blowout limit in a reasonable consistent with the available experimental data through adjusting the critical Damkohler number of each definition in the current study. The performances and physical differences of three definitions were also discussed.

Analysis of the Equilibrium Approximation in Chemical Ablation of Thermal Protective Systems

2012 ◽  
Author(s):  
B. W. Barr ◽  
O. A. Ezekoye
Keyword(s):  
Experimental Data ◽  
Complex Surface ◽  
Damkohler Number ◽  
Damköhler Number ◽  
Graphite Oxidation ◽  
Model Predictions ◽  
Surface Equilibrium ◽  
Carbon Combustion ◽  
New Formulation ◽  
Good Agreement

A quasi-steady-state ablation model is used to investigate the behavior of thermochemically ablating systems in equilibrium and nonequilibrium surface thermochemistry regimes. The model is simplified to allow extraction of relevant nondimensional parameters and comparison with existing experimental data on solid carbon combustion. Good agreement is found between model predictions and experimental data, and the data and model are collapsed in terms of the B number and surface Damkohler number. A new formulation for the surface Damkohler number is proposed, and a relationship between the B number and this Damkohler number is derived for the surface equilibrium and nonequilibrium regimes. The Damkohler formulation is applied to the reentry scenario, and the behavior of the B number in this context is explored. Nondimensional parameters governing behavior in the nonequilibrium regime are determined for graphite oxidation, and the results are extrapolated to more complex surface thermochemistry conditions.

Analysis of Radiation-Induced Chromosomal Aberrations on a Cell-by-Cell Basis after Alpha-Particle Microbeam Irradiation: Experimental Data and Simulations

2018 ◽  
Vol 189 (6) ◽  
pp. 597-604 ◽  
Author(s):  
Antonella Testa ◽  
Francesca Ballarini ◽  
Ulrich Giesen ◽  
Octávia Monteiro Gil ◽  
Mario P. Carante ◽  
...  
Keyword(s):  
Experimental Data ◽  
Alpha Particle ◽  
Chromosomal Aberrations ◽  
Cell Basis ◽  
Microbeam Irradiation ◽  
A Cell ◽  
Radiation Induced

Observation of the flame structures emerging at low Damköhler number fields

2007 ◽  
Vol 31 (1) ◽  
pp. 1353-1359 ◽  
Author(s):  
Manabu Fuchihata ◽  
Masashi Katsuki ◽  
Yukio Mizutani ◽  
Tamio Ida
Keyword(s):  
Number Fields ◽  
Damkohler Number ◽  
Damköhler Number ◽  
Flame Structures

SBES/FGM Simulation of Film-Cooled Surface Heat Transfer and Near-Wall Reaction

2020 ◽  
Author(s):  
Yu Xia ◽  
Patrick Sharkey ◽  
Stefano Orsino ◽  
Mike Kuron ◽  
Florian Menter ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Damkohler Number ◽  
Surface Heat Transfer ◽  
Damköhler Number ◽  
Aero Engine ◽  
Cooling Hole

Abstract Accurate numerical prediction of surface heat transfer in the presence of film cooling within aero-engine sub-components, such as blade effusion holes and combustor liners, has long been a goal of the aero-engine industry. It requires accurate simulation of the turbulent mixing and reaction processes between freestream and the cooling flow. In this study, the Stress Blended Eddy Simulation (SBES) turbulence model is used together with the Flamelet Generated Manifold (FGM) combustion model to calculate the surface heat flux upstream and downstream of an effusion cooling hole. The SBES model employs a blending function to automatically switch between RANS and LES based on the local flow features, and thus significantly reduces the computational cost compared to a full LES simulation. All simulations are run using ANSYS Fluent®, a commercial finite-volume CFD solver. The test case corresponds to an experimental rig run at MIT, which is essentially a flat plate brushed by a uniform freestream of argon with ethylene seeded inside, and is cooled by either a reacting air or non-reacting nitrogen jet inclined at 35 degrees to the freestream. Calculations are performed for both reacting and non-reacting jet cooling cases across a range of jet-to-stream blowing ratios, and compared with the experimental data. The effects of mesh resolution are also investigated. Calculations are also performed across a range of Damköhler number (i.e. flow to chemical time ratio) from zero to 30, with unity blowing ratio, and the differences in the maximum surface heat flux magnitude in the reacting and non-reacting cases at a specific location downstream of the hole are investigated. Results from these analyses show good correlation with the experimental heat flux data upstream and downstream of the cooling hole, including the heat flux augmentation due to local reaction. Results from the Damköhler number sweep also show a good match with the experimental data across the range investigated.

Influence of Fuel Characteristics in a Correlation to Predict Lean Blowout of Bluff-Body Stabilized Flames

2015 ◽  
Author(s):  
Bethany C. Huelskamp ◽  
Barry V. Kiel ◽  
Ponnuthurai Gokulakrishnan
Keyword(s):  
Ignition Delay ◽  
Delay Time ◽  
Bluff Body ◽  
Ignition Delay Time ◽  
Laminar Flame ◽  
Damkohler Number ◽  
Lean Blowout ◽  
Damköhler Number ◽  
Combining Data ◽  
Stabilized Flames

This study employed experimental data collected at the Air Force Research Laboratory (AFRL) as well as data from a review of past literature to develop a correlation for predicting lean blowout through the use of a least-squares curve-fit method. Combining data from the literature with data from AFRL allowed significant variations within the dataset with regard to velocity, flameholder diameter and shape, pressure, temperature, and fuel. Gaseous, single-component fuels as well as multi-component jet fuels were included in the study. The study reports new jet fuel blowout data. The laminar flame speed and ignition delay time calculated using detailed chemical kinetics mechanisms were used in the correlations to determine the chemical timescales relevant to lean blowout. The correlation presented here indicates that the lean blowout of bluff-body stabilized flames is dependent on the Damköhler number, with fuel variation being a significant factor. The ratio of the flameholder diameter to the lip velocity was found to influence the lean blowout. This ratio represents the fluid-mechanic timescale in the Damköhler number. Pressure, temperature, and the hydrogen-to-carbon ratio of the fuel affect the reactivity of the mixture, contributing to the chemical timescale in the Damköhler number. For a limited dataset, the ignition delay time is an adequate representation of the chemical timescale.

scholarly journals Minimum Number of Experimental Data for the Thermal Characterization of a Hot Water Storage Tank

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4741
Author(s):  
María Gasque ◽  
Federico Ibáñez ◽  
Pablo González-Altozano
Keyword(s):  
Experimental Data ◽  
Water Temperature ◽  
Temperature Profile ◽  
Storage Tank ◽  
Water Storage ◽  
Hot Water ◽  
Experimental Temperature ◽  
Inlet Temperature ◽  
Water Storage Tank ◽  
Minimum Number

This paper demonstrates that it is possible to characterize the water temperature profile and its temporal trend in a hot water storage tank during the thermal charge process, using a minimum number of thermocouples (TC), with minor differences compared to experimental data. Four experimental tests (two types of inlet and two water flow rates) were conducted in a 950 L capacity tank. For each experimental test (with 12 TC), four models were developed using a decreasing number of TC (7, 4, 3 and 2, respectively). The results of the estimation of water temperature obtained with each of the four models were compared with those of a fifth model performed with 12 TC. All models were tested for constant inlet temperature. Very acceptable results were achieved (RMSE between 0.2065 °C and 0.8706 °C in models with 3 TC). The models were also useful to estimate the water temperature profile and the evolution of thermocline thickness even with only 3 TC (RMSE between 0.00247 °C and 0.00292 °C). A comparison with a CFD model was carried out to complete the study with very small differences between both approaches when applied to the estimation of the instantaneous temperature profile. The proposed methodology has proven to be very effective in estimating several of the temperature-based indices commonly employed to evaluate thermal stratification in water storage tanks, with only two or three experimental temperature data measurements. It can also be used as a complementary tool to other techniques such as the validation of numerical simulations or in cases where only a few experimental temperature values are available.

A Critical Review of NOx Correlations for Gas Turbine Combustors

1975 ◽  
Author(s):  
D. A. Sullivan ◽  
P. A. Mas
Keyword(s):  
Experimental Data ◽  
Data Base ◽  
Gas Turbine ◽  
Critical Review ◽  
Inlet Temperature ◽  
Nox Emissions ◽  
Empirical Correlations ◽  
Gas Turbine Combustors ◽  
Semi Empirical ◽  
Adequate Data

The effect of inlet temperature, pressure, air flowrate and fuel-to-air ratio on NOx emissions from gas turbine combustors has received considerable attention in recent years. A number of semi-empirical and empirical correlations relating these variables to NOx emissions have appeared in the literature. They differ both in fundamental assumptions and in their predictions. In the present work, these simple NOx correlations are compared to each other and to experimental data. A review of existing experimental data shows that an adequate data base does not exist to evaluate properly the various NOx correlations. Recommendations are proposed to resolve this problem in the future.

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