ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety ... more ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety applications. Relevant literature has focused on characterizing mean radiation properties of exhaust plumes. Turbulent radiation properties reported for flames have been used to provide insight into scalar distribution within the flows, improve understanding of turbulence radiation interactions, and estimate integral time and length scales. Motivated by this, radiation intensity measurements of subsonic exhaust plumes were acquired using a high-speed infrared camera (up to 11,300 Hz). The mean, root mean square, probability density function, auto and spatial correlation coefficients, integral time and length scales, and power spectral density functions of the measured radiation intensity are reported near the tip of the potential core and downstream. Axial and radial variation in radiation intensity fluctuations is similar to those reported for flames. Autocorrelation coefficients of the radiation intensity are approximated reasonably well by exponential curves. Integral time and length scales increase monotonically downstream of the core region and are consistent with Taylor's hypothesis. The break frequency and slope of the normalized power spectral density function are comparable to those reported for turbulent jet flames. These findings suggest that reacting flows can be used to predict trends in turbulent radiation properties of exhaust plumes.
ABSTRACT Measurements of the reaction rates at high-pressures for gasification of low-ash pinewoo... more ABSTRACT Measurements of the reaction rates at high-pressures for gasification of low-ash pinewood char with CO2 are presented. A fixed-bed reactor operated at 1140–1260 K and 1–10 atm was utilized in the present study. Product gas sampling and gas chromatograph measurements enabled tracking of the gasification progress and mass loss data. The mass loss data are interpreted using the volumetric and non-reactive core models. Activation energy, collision frequency and reaction order are reported for each model. The experimental data show high sensitivity to temperature. The data also show an increase of the apparent gasification rates with higher CO2 pressures. Comparison of computed char conversion profiles and experimental data are discussed in the context of mass transport and effects on the gasification rates. The findings from this study have applications to gasification modeling and design of large-scale gasification systems.
Steady-state global chemistry calculations for 20 different flames were carried out using an axis... more Steady-state global chemistry calculations for 20 different flames were carried out using an axisymmetric Computational Fluid Dynamics (CFD) code. Computational results for 16 flames were compared with flame images obtained at the NASA Glenn Research Center. The experimental flame data for these 16 flames were taken from Sunderland et al. [4] which included normal and inverse diffusion flames of ethane
A Dynamic Data Driven Application System (DDDAS) was created to study interaction between fire an... more A Dynamic Data Driven Application System (DDDAS) was created to study interaction between fire and agent models during a fire evacuation. The analysis from that research can be used to validate proposed ideas in evacuation and building designs to ensure safety of buildings given various agent behaviors. Two separate models were used to simulate the components of the emergency situation: fire and agent. The independent models were able to run using data computed by the other interacting models, allowing careful examination of real-time interactions in a situation. Through study of the interactions, a better understanding is gained of how individual variables such as exit position and width affect the evacuation process and escape rate in the given scenario. Exits can be relocated and changed to quickly assess the effect on the model. The results can be used for improving building design and regulations as well as training first responders.
A society of simulations facilitates modelling a complex, real life system. Precise models result... more A society of simulations facilitates modelling a complex, real life system. Precise models result from the emergent behavior of specialized simulations grouped together as individual members in a society. Each member simulation independently operates on its own understanding of reality. Members cooperate with each other to achieve the goals of the society while satisfying their own local goals. When members
We describe, for the first time, the structure and steady-state performance of an effervescent Di... more We describe, for the first time, the structure and steady-state performance of an effervescent Diesel injector (EDI) having a needle and sac and being entirely contained in a conventional Diesel injector body. Experimental results help address key questions, including the single influences of needle lift, exit orifice diameter, aerator pore size, atomizing gas–liquid ratio, and injection pressure on injector performance
Time-series measurements of OH, as related to accompanying flow structures, are reported using pi... more Time-series measurements of OH, as related to accompanying flow structures, are reported using picosecond time-resolved laser-induced fluorescence (PITLIF) and particle-imaging velocimetry (PIV) for turbulent, swirling, nonpremixed methane–air flames. The [OH] data portray a primary reaction zone surrounding the internal recirculation zone, with residual OH in the recirculation zone approaching chemical equilibrium. Modeling of the OH electronic quenching environment, when compared
... Titre du document / Document title. Effects of combustion on the sound pressure generated by ... more ... Titre du document / Document title. Effects of combustion on the sound pressure generated by circular jet flows. Auteur(s) / Author(s). SINGH Kapil K. (1) ; FRANKEL Steven H. (1) ; GOREJay P. (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). ...
The occurrence of oscillating combustion and combustion instability has led to resurgence of inte... more The occurrence of oscillating combustion and combustion instability has led to resurgence of interest in causes, mechanisms, suppression, and control of flame noise. Nonpremixed flame noise is low frequency and difficult to control using conventional acoustic liner and so ...
Experimental data are essential for the validation of radiation submodels, which have been found ... more Experimental data are essential for the validation of radiation submodels, which have been found to be important for predicting pollutant formation in turbulent flames. Instantaneous radiation signals also provide fundamental information about scalar properties in turbulent combustion. Motivated by this, we report measurements of line-of-sight spectral radiation intensities from a non-premixed CH 4 /H 2 /N 2 turbulent jet flame. The burner and the operating conditions are selected to take advantage of extensive scalar property and velocity measurements available in the literature. At three axial locations in the flame, a fast IR array spectrometer was used to capture the instantaneous radiation intensities for diametric radiation paths. Radiation intensities for the chord-like paths along various radial positions at one of the axial locations were also measured. By using stochastic time and space series (TASS) analysis, the instantaneous emission spectra were also simulated accounting for the turbulence/radiation interactions. In the simulations, the measurements of scalar statistics and mean velocity data were adopted to avoid uncertainties of a combustion model. The calculated mean and root mean square spectral radiation intensities are within 10% of the experimental data. Since the calculated root mean square values are strongly dependent on the integral length scales used in the TASS, these scales were estimated by fitting the calculation to the data. A tomography-like technique was also adopted to simulate the radiation intensities for chord-like paths from the flame edge to the center to examine the radial variation of the integral length scale. The results show factors of 3 variations in the integral length scale that have been ignored in the past work.
Fast (6250 Hz) line-of-sight measurements of infrared spectral radiation intensities (I λ ) from ... more Fast (6250 Hz) line-of-sight measurements of infrared spectral radiation intensities (I λ ) from a luminous flame and a new deconvolution technique for the estimate of local scalar properties using inverse radiation calculations are reported. Time series data of I λ for one diametric ...
Numerical Heat Transfer, Part A: Applications, 2003
A weighted sum of gray gases model (WSGGM)-based low-resolution spectral model for calculating ra... more A weighted sum of gray gases model (WSGGM)-based low-resolution spectral model for calculating radiation transfer in combustion gases is applied to estimate self-absorption of radiation energy in one-dimensional opposed-flow flames. Development of such a model is necessary in order to enable detailed chemistry-radiation interaction calculations including self-absorption. A database of band model parameters which can be applied to various one-dimensional
ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety ... more ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety applications. Relevant literature has focused on characterizing mean radiation properties of exhaust plumes. Turbulent radiation properties reported for flames have been used to provide insight into scalar distribution within the flows, improve understanding of turbulence radiation interactions, and estimate integral time and length scales. Motivated by this, radiation intensity measurements of subsonic exhaust plumes were acquired using a high-speed infrared camera (up to 11,300 Hz). The mean, root mean square, probability density function, auto and spatial correlation coefficients, integral time and length scales, and power spectral density functions of the measured radiation intensity are reported near the tip of the potential core and downstream. Axial and radial variation in radiation intensity fluctuations is similar to those reported for flames. Autocorrelation coefficients of the radiation intensity are approximated reasonably well by exponential curves. Integral time and length scales increase monotonically downstream of the core region and are consistent with Taylor's hypothesis. The break frequency and slope of the normalized power spectral density function are comparable to those reported for turbulent jet flames. These findings suggest that reacting flows can be used to predict trends in turbulent radiation properties of exhaust plumes.
ABSTRACT An axisymmetric two-dimensional model of chemical reaction and heat transfer that accoun... more ABSTRACT An axisymmetric two-dimensional model of chemical reaction and heat transfer that accounts for the transport of mass, momentum, heat, and species in radial and axial directions has been developed to provide a fundamental understanding of the transport phenomena relevant to porous radiant burners made from ported ceramics. The passage geometry of practical porous media is modeled as a cylindrical tube in which combustion takes place, This enables treatment of the chemical reactions and transport processes in the gas phase, of heat conduction in the tube wall, and of radiation exchange on the inside surface of the tube to account for the conjugate heat transfer effects. The predictions are compared with available experimental data for the purpose of model validation. Parametric calculations are performed using the model to improve understanding of the phenomena.
Ammonia borane (AB) is a candidate material for on-board hydrogen storage, and hydrolysis is one ... more Ammonia borane (AB) is a candidate material for on-board hydrogen storage, and hydrolysis is one of the potential processes by which the hydrogen may be released. This paper presents hydrogen generation measurements from the hydrolysis of dilute AB aqueous solutions catalyzed by ruthenium supported on carbon. Reaction kinetics necessary for the design of hydrolysis reactors were derived from the measurements. The hydrolysis had reaction orders greater than zero but less than unity in the temperature range from 16 • C to 55 • C. A Langmuir-Hinshelwood kinetic model was adopted to interpret the data with parameters determined by a non-linear conjugate-gradient minimization algorithm. The rutheniumcatalyzed AB hydrolysis was found to have activation energy of 76 ± 0.1 kJ mol −1 and adsorption energy of −42.3 ± 0.33 kJ mol −1 . The observed hydrogen release rates were 843 ml H 2 min −1 (g catalyst) −1 and 8327 ml H 2 min −1 (g catalyst) −1 at 25 • C and 55 • C, respectively. The hydrogen release from AB catalyzed by ruthenium supported on carbon is significantly faster than that catalyzed by cobalt supported on alumina. Finally, the kinetic rate of hydrogen release by AB hydrolysis is much faster than that of hydrogen release by base-stabilized sodium borohydride hydrolysis.
... gains from improved thermal management and efficiency losses from additional weight and theen... more ... gains from improved thermal management and efficiency losses from additional weight and theenergy consumption of the thermal management system itself. Recently, several review articles have addressed various aspects of hydrogen storage technologies , but none has ...
ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety ... more ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety applications. Relevant literature has focused on characterizing mean radiation properties of exhaust plumes. Turbulent radiation properties reported for flames have been used to provide insight into scalar distribution within the flows, improve understanding of turbulence radiation interactions, and estimate integral time and length scales. Motivated by this, radiation intensity measurements of subsonic exhaust plumes were acquired using a high-speed infrared camera (up to 11,300 Hz). The mean, root mean square, probability density function, auto and spatial correlation coefficients, integral time and length scales, and power spectral density functions of the measured radiation intensity are reported near the tip of the potential core and downstream. Axial and radial variation in radiation intensity fluctuations is similar to those reported for flames. Autocorrelation coefficients of the radiation intensity are approximated reasonably well by exponential curves. Integral time and length scales increase monotonically downstream of the core region and are consistent with Taylor's hypothesis. The break frequency and slope of the normalized power spectral density function are comparable to those reported for turbulent jet flames. These findings suggest that reacting flows can be used to predict trends in turbulent radiation properties of exhaust plumes.
ABSTRACT Measurements of the reaction rates at high-pressures for gasification of low-ash pinewoo... more ABSTRACT Measurements of the reaction rates at high-pressures for gasification of low-ash pinewood char with CO2 are presented. A fixed-bed reactor operated at 1140–1260 K and 1–10 atm was utilized in the present study. Product gas sampling and gas chromatograph measurements enabled tracking of the gasification progress and mass loss data. The mass loss data are interpreted using the volumetric and non-reactive core models. Activation energy, collision frequency and reaction order are reported for each model. The experimental data show high sensitivity to temperature. The data also show an increase of the apparent gasification rates with higher CO2 pressures. Comparison of computed char conversion profiles and experimental data are discussed in the context of mass transport and effects on the gasification rates. The findings from this study have applications to gasification modeling and design of large-scale gasification systems.
Steady-state global chemistry calculations for 20 different flames were carried out using an axis... more Steady-state global chemistry calculations for 20 different flames were carried out using an axisymmetric Computational Fluid Dynamics (CFD) code. Computational results for 16 flames were compared with flame images obtained at the NASA Glenn Research Center. The experimental flame data for these 16 flames were taken from Sunderland et al. [4] which included normal and inverse diffusion flames of ethane
A Dynamic Data Driven Application System (DDDAS) was created to study interaction between fire an... more A Dynamic Data Driven Application System (DDDAS) was created to study interaction between fire and agent models during a fire evacuation. The analysis from that research can be used to validate proposed ideas in evacuation and building designs to ensure safety of buildings given various agent behaviors. Two separate models were used to simulate the components of the emergency situation: fire and agent. The independent models were able to run using data computed by the other interacting models, allowing careful examination of real-time interactions in a situation. Through study of the interactions, a better understanding is gained of how individual variables such as exit position and width affect the evacuation process and escape rate in the given scenario. Exits can be relocated and changed to quickly assess the effect on the model. The results can be used for improving building design and regulations as well as training first responders.
A society of simulations facilitates modelling a complex, real life system. Precise models result... more A society of simulations facilitates modelling a complex, real life system. Precise models result from the emergent behavior of specialized simulations grouped together as individual members in a society. Each member simulation independently operates on its own understanding of reality. Members cooperate with each other to achieve the goals of the society while satisfying their own local goals. When members
We describe, for the first time, the structure and steady-state performance of an effervescent Di... more We describe, for the first time, the structure and steady-state performance of an effervescent Diesel injector (EDI) having a needle and sac and being entirely contained in a conventional Diesel injector body. Experimental results help address key questions, including the single influences of needle lift, exit orifice diameter, aerator pore size, atomizing gas–liquid ratio, and injection pressure on injector performance
Time-series measurements of OH, as related to accompanying flow structures, are reported using pi... more Time-series measurements of OH, as related to accompanying flow structures, are reported using picosecond time-resolved laser-induced fluorescence (PITLIF) and particle-imaging velocimetry (PIV) for turbulent, swirling, nonpremixed methane–air flames. The [OH] data portray a primary reaction zone surrounding the internal recirculation zone, with residual OH in the recirculation zone approaching chemical equilibrium. Modeling of the OH electronic quenching environment, when compared
... Titre du document / Document title. Effects of combustion on the sound pressure generated by ... more ... Titre du document / Document title. Effects of combustion on the sound pressure generated by circular jet flows. Auteur(s) / Author(s). SINGH Kapil K. (1) ; FRANKEL Steven H. (1) ; GOREJay P. (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). ...
The occurrence of oscillating combustion and combustion instability has led to resurgence of inte... more The occurrence of oscillating combustion and combustion instability has led to resurgence of interest in causes, mechanisms, suppression, and control of flame noise. Nonpremixed flame noise is low frequency and difficult to control using conventional acoustic liner and so ...
Experimental data are essential for the validation of radiation submodels, which have been found ... more Experimental data are essential for the validation of radiation submodels, which have been found to be important for predicting pollutant formation in turbulent flames. Instantaneous radiation signals also provide fundamental information about scalar properties in turbulent combustion. Motivated by this, we report measurements of line-of-sight spectral radiation intensities from a non-premixed CH 4 /H 2 /N 2 turbulent jet flame. The burner and the operating conditions are selected to take advantage of extensive scalar property and velocity measurements available in the literature. At three axial locations in the flame, a fast IR array spectrometer was used to capture the instantaneous radiation intensities for diametric radiation paths. Radiation intensities for the chord-like paths along various radial positions at one of the axial locations were also measured. By using stochastic time and space series (TASS) analysis, the instantaneous emission spectra were also simulated accounting for the turbulence/radiation interactions. In the simulations, the measurements of scalar statistics and mean velocity data were adopted to avoid uncertainties of a combustion model. The calculated mean and root mean square spectral radiation intensities are within 10% of the experimental data. Since the calculated root mean square values are strongly dependent on the integral length scales used in the TASS, these scales were estimated by fitting the calculation to the data. A tomography-like technique was also adopted to simulate the radiation intensities for chord-like paths from the flame edge to the center to examine the radial variation of the integral length scale. The results show factors of 3 variations in the integral length scale that have been ignored in the past work.
Fast (6250 Hz) line-of-sight measurements of infrared spectral radiation intensities (I λ ) from ... more Fast (6250 Hz) line-of-sight measurements of infrared spectral radiation intensities (I λ ) from a luminous flame and a new deconvolution technique for the estimate of local scalar properties using inverse radiation calculations are reported. Time series data of I λ for one diametric ...
Numerical Heat Transfer, Part A: Applications, 2003
A weighted sum of gray gases model (WSGGM)-based low-resolution spectral model for calculating ra... more A weighted sum of gray gases model (WSGGM)-based low-resolution spectral model for calculating radiation transfer in combustion gases is applied to estimate self-absorption of radiation energy in one-dimensional opposed-flow flames. Development of such a model is necessary in order to enable detailed chemistry-radiation interaction calculations including self-absorption. A database of band model parameters which can be applied to various one-dimensional
ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety ... more ABSTRACT Improved understanding of radiation emissions from exhaust plumes are needed for safety applications. Relevant literature has focused on characterizing mean radiation properties of exhaust plumes. Turbulent radiation properties reported for flames have been used to provide insight into scalar distribution within the flows, improve understanding of turbulence radiation interactions, and estimate integral time and length scales. Motivated by this, radiation intensity measurements of subsonic exhaust plumes were acquired using a high-speed infrared camera (up to 11,300 Hz). The mean, root mean square, probability density function, auto and spatial correlation coefficients, integral time and length scales, and power spectral density functions of the measured radiation intensity are reported near the tip of the potential core and downstream. Axial and radial variation in radiation intensity fluctuations is similar to those reported for flames. Autocorrelation coefficients of the radiation intensity are approximated reasonably well by exponential curves. Integral time and length scales increase monotonically downstream of the core region and are consistent with Taylor's hypothesis. The break frequency and slope of the normalized power spectral density function are comparable to those reported for turbulent jet flames. These findings suggest that reacting flows can be used to predict trends in turbulent radiation properties of exhaust plumes.
ABSTRACT An axisymmetric two-dimensional model of chemical reaction and heat transfer that accoun... more ABSTRACT An axisymmetric two-dimensional model of chemical reaction and heat transfer that accounts for the transport of mass, momentum, heat, and species in radial and axial directions has been developed to provide a fundamental understanding of the transport phenomena relevant to porous radiant burners made from ported ceramics. The passage geometry of practical porous media is modeled as a cylindrical tube in which combustion takes place, This enables treatment of the chemical reactions and transport processes in the gas phase, of heat conduction in the tube wall, and of radiation exchange on the inside surface of the tube to account for the conjugate heat transfer effects. The predictions are compared with available experimental data for the purpose of model validation. Parametric calculations are performed using the model to improve understanding of the phenomena.
Ammonia borane (AB) is a candidate material for on-board hydrogen storage, and hydrolysis is one ... more Ammonia borane (AB) is a candidate material for on-board hydrogen storage, and hydrolysis is one of the potential processes by which the hydrogen may be released. This paper presents hydrogen generation measurements from the hydrolysis of dilute AB aqueous solutions catalyzed by ruthenium supported on carbon. Reaction kinetics necessary for the design of hydrolysis reactors were derived from the measurements. The hydrolysis had reaction orders greater than zero but less than unity in the temperature range from 16 • C to 55 • C. A Langmuir-Hinshelwood kinetic model was adopted to interpret the data with parameters determined by a non-linear conjugate-gradient minimization algorithm. The rutheniumcatalyzed AB hydrolysis was found to have activation energy of 76 ± 0.1 kJ mol −1 and adsorption energy of −42.3 ± 0.33 kJ mol −1 . The observed hydrogen release rates were 843 ml H 2 min −1 (g catalyst) −1 and 8327 ml H 2 min −1 (g catalyst) −1 at 25 • C and 55 • C, respectively. The hydrogen release from AB catalyzed by ruthenium supported on carbon is significantly faster than that catalyzed by cobalt supported on alumina. Finally, the kinetic rate of hydrogen release by AB hydrolysis is much faster than that of hydrogen release by base-stabilized sodium borohydride hydrolysis.
... gains from improved thermal management and efficiency losses from additional weight and theen... more ... gains from improved thermal management and efficiency losses from additional weight and theenergy consumption of the thermal management system itself. Recently, several review articles have addressed various aspects of hydrogen storage technologies , but none has ...
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