Developing a CFD Model to Predict Radiological Materials Packaging Temperatures within a Generic Staging Building
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Adiabatic Temperature↗
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Elastic constants of single-crystal forsterite as a function of temperature and pressure
Adiabatic elastic stiffness constants of single crystal forsterite measured as function of hydrostatic pressure and temperature, using pulse superposition technique
Barsch, G. R.↗
Investigation of 10-Stage Axial-Flow X24C-2 Compressor: Performance at Inlet Pressure of 21 Inches Mercury Absolute and Inlet Temperature of 538 R - 1
The performance at inlet pressure of 21 inches mercury absolute and inlet temperature of 538 R for the 10-stage axial-flow X24C-2 compressor from the X24C-2 turbojet engine was investigated. the peak adiabatic temperature-rise efficiency for a given speed generally occurred at values of pressure coefficient fairly close to 0.35.For this compressor, the efficiency data at various speeds could be correlated on two converging curves by the use of a polytropic loss factor derived.
Schum, Harold J.↗
Flame kinetics at scramjet-engine-relevant conditions: Role of prompt dissociation of weakly-bound radicals
Combustion in high-speed ram-based propulsion engines occurs under distinct thermodynamic conditions of high reactant temperatures (greater than 1000 K) and relatively low pressures (<5 atm). There is a lack of fundamental flame measurements at such conditions that result in adiabatic flame temperatures (T ad ) exceeding 2500 K. In this work, we have measured laminar flame speeds of oxygen-enriched CH 4 /oxidizer mixtures at sub-atmospheric conditions to probe kinetics at high T ad using the isobaric spherically expanding flame approach. Simulations with recent kinetic models revealed increasing differences between data and model predictions with increasing T ad , reaching up to 25 %. Kinetic analyses reveal that at the thermodynamic conditions in these O 2 -enriched flames, i.e., lower pressures and higher T ad , the effects of HCO prompt dissociation are accentuated. In addition to HCO, the prompt dissociations of CH 2 OH and C 2 H 5 are also considered. Here, the prompt dissociations of all three radicals were evaluated and their effects considered in flame speed simulations. Reaction path analysis for the present flames revealed that approximately half of the reaction flux for HCO formation undergoes prompt dissociation to H + CO. Furthermore, these analyses also revealed that the pathways and sensitive reactions are similar between oxygen-enriched fuel/oxidizer mixtures and preheated fuel/air mixtures, if both have similar T ad . Thus, flames of oxygen-enriched mixtures could be a surrogate to probe the flame chemistry of highly preheated mixtures at relatively low pressures that are often encountered in ram-based propulsion engine combustors.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
An ALMA+ACA measurement of the shock in the Bullet Cluster
Context: The thermal Sunyaev-Zeldovich (SZ) effect presents a relatively new tool for characterizing galaxy cluster merger shocks, traditionally studied through X-ray observations. Widely regarded as the “textbook example” of a cluster merger bow shock, the western, most-prominent shock front in the Bullet Cluster (1E0657-56) represents the ideal test case for such an SZ study. Aims: We aim to characterize the shock properties using deep, high-resolution interferometric SZ effect observations in combination with priors from an independent X-ray analysis. Methods: Our analysis technique relies on the reconstruction of a parametric model for the SZ signal by directly and jointly fitting data from the Atacama Large Millimeter/submillimeter Array (ALMA) and Atacama Compact Array (ACA) in Fourier space. Results: The ALMA+ACA data are primarily sensitive to the electron pressure difference across the shock front. To estimate the shock Mach number M, this difference can be combined with the value for the upstream electron pressure derived from an independent Chandra X-ray analysis. In the case of instantaneous electron-ion temperature equilibration, we find M = 2.08 (+0.12,−0.12), in ≈ 2.4σ tension with the independent constraint from Chandra, M(X)= 2.74 ± 0.25. The assumption of purely adiabatic electron temperature change across the shock leads to M = 2.53 (+0.33,−0.25), in better agreement with the X-ray estimate M(X) = 2.57 ± 0.23 derived for the same heating scenario. Conclusion: We have demonstrated that interferometric observations of the thermal SZ effect provide constraints on the properties of the shock in the Bullet Cluster that are highly complementary to X-ray observations. The combination of X-ray and SZ data yields a powerful probe of the shock properties, capable of measuring M and addressing the question of electron-ion equilibration in cluster shocks. Our analysis is however limited by systematics related to the overall cluster geometry and the complexity of the post-shock gas distribution. To overcome these limitations, a simultaneous, joint-likelihood analysis of SZ and X-ray data is needed.
Luca Di Mascolo↗
Turbulent boundary-layer velocity profiles on a nonadiabatic at Mach number 6.5
Velocity profiles were obtained from pitot-pressure and total-temperature measurements within a turbulent boundary layer on a large sharp-edged flat plate. Momentum-thickness Reynolds number ranged from 2590 to 8860 and wall-to-adiabatic-wall temperature ratios ranged from 0.3 to 0.5. Measurements were made both with and without boundary layer trips. Five methods are evaluated for correlating the measured velocity profiles with the incompressible law-of-the-wall and the velocity defect law. The mixing-length generalization of Van Driest gives the best correlation.
Keener, E. R.↗
Effect of inlet temperature on the performance of a catalytic reactor
A 12-cm-diameter by 15-cm-long catalytic reactor was tested with No. 2 diesel fuel in a combustion test rig at inlet temperatures of 700, 800, 900, and 1000 K. Other test conditions included pressures of 300,000 and 600,000 Pa, reference velocities of 10, 15, and 20 m/s, and adiabatic combustion temperatures in the range from 1100 to 1400 K. The combustion efficiency was calculated from measurements of carbon monoxide and unburned hydrocarbon emissions. Nitrogen oxide emissions and reactor pressure drop were also measured. At a reference velocity of 10 m/s, the CO and unburned hydrocarbons emissions and, therefore, the combustion efficiency were independent of inlet temperature. At an inlet temperature of 1000 K, they were independent of reference velocity. Nitrogen oxides emissions resulted from conversion of the small amount of fuel-bound nitrogen in the fuel. Up to 90% conversion was observed with no apparent effect of any of the test variables. For typical gas-turbine operating conditions, all three pollutants were below levels which would permit the most stringent proposed automotive emissions standards to be met.
Anderson, D. N.↗
Heat transfer characteristics for jet array impingement with initial crossflow
Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. In addition to the crossflow which originates from the jets following impingement, an initial crossflow is present which approaches the array through an upstream extension of the channel. The temperature of the initial crossflow air may differ from the jet air temperature. The configurations considered are intended to model the impingement cooled midchord region of gas turbine airfoils in cases where an initial crossflow is also present. Nusselt numbers and dimensionless adiabatic wall temperatures resolved to one streamwise jet hole spacing were experimentally determined for ratios of the initial crossflow rate to the total jet flow rate ranging from zero to unity. These are presented and discussed relative to the flow and geometric parameters.
Florschuetz, L. W.↗
Evaluation of Equilibrium Turbulence for a Hypersonic Boundary Layer at Nonadiabatic Wall Conditions
This paper presents an experimental study to characterize the naturally developing compressible turbulent boundary layer produced along a flat plate measuring 9.7 feet long in the NASA Langley 8-Foot High Temperature Tunnel and to determine the test conditions necessary to achieve equilibrium turbulence. The measurements consist of pitot pressure, static pressure, and total temperature distributions in the boundary layer. In addition, surface measurements consisting of heat transfer and pressure distributions were obtained. The tests were conducted at a nominal free-stream Mach number of 6.5, total temperatures of 2700 and 3300 R, and angles of attack of 5 and 13 degrees. The corresponding nominal boundary-layer edge Mach numbers were 6.2 and 5.0. The nominal ratios of adiabatic wall temperature to cold wall temperature were 4.4 and 5.4 and the momentum thickness Reynolds numbers at the boundary layer probe locations ranged from 400 to 7800. The results of this study indicate that momentum thickness Reynolds numbers of at least 4000 are required to obtain an equilibrium turbulent boundary layer in the Langley 8-Foot High Temperature Tunnel. This evaluation is based primarily on the behavior of shape factors inferred from the boundary-layer measurements.
Albertson, Cindy W.↗
Effect of inlet temperature on the performance of a catalytic reactor
A 12 cm diameter by 15 cm long catalytic reactor was tested with No. 2 diesel fuel in a combustion test rig at inlet temperatures of 700, 800, 900, and 1000 K. Other test conditions included pressures of 3 and 6 x 10 to the 5th power Pa, reference velocities of 10, 15, and 20 m/s, and adiabatic combustion temperatures in the range 1100 to 1400 K. The combustion efficiency was calculated from measurements of carbon monoxide and unburned hydrocarbon emissions. Nitrogen oxide emissions and reactor pressure drop were also measured. At a reference velocity of 10 m/s, the CO and unburned hydrocarbons emissions, and, therefore, the combustion efficiency, were independent of inlet temperature. At an inlet temperature of 1000 K, they were independent of reference velocity. Nitrogen oxides emissions resulted from conversion of the small amount (135 ppm) of fuel-bound nitrogen in the fuel. Up to 90 percent conversion was observed with no apparent effect of any of the test variables. For typical gas turbine operating conditions, all three pollutants were below levels which would permit the most stringent proposed automotive emissions standards to be met.
Anderson, D. N.↗
A Warm Garage for a Lunar Rover
Approach: One approach to heating a rover during the lunar night is the so-called thermal wadis concept [1]. This involves heating the regolith with solar concentrators and placing the rover on the heated surface for the night. Since the regolith is heated by a relatively weak heat flux, a high thermal conductivity is required for heating a sufficiently large mass of regolith. However, lunar regolith has a low thermal conductivity. Therefore, the concept involves increasing the conductivity by sintering the regolith, which requires a significant energy input and complex procedures. Here we propose an alternative approach where the low thermal conductivity of regolith is an advantage. Specifically, we propose to use a highly exothermic combustible mixture for heat generation. The mixture pellets are placed in the surface layer of regolith and ignited. The combustion forms condensed products and releases heat, which then slowly spreads to the surrounding regolith. Heat can also be transferred, for example, by heat pipes, into radiant heating surfaces installed on the ground. A greenhouse that transmits sunlight during the day and decreases the radiative heat losses during the night can also be installed. Selection of the Heat-generating Mixture: The reactive mixture should have a high specific energy and generate only condensed products since gases could disturb the regolith layer, carry enthalpy out of the system, and lead to an explosion. There are mixtures, (sometimes called pyrolants) that possess very high specific energies. One example is magnesium-Teflon-Viton mixtures used in flares. However, they produce gases and may cause explosions. Other mixtures that include magnesium cannot be used either because of the high vapor pressure of Mg at temperatures well below the combustion temperature. Recently, mixtures that involve lithium peroxide (Li2O2) have been proposedfor using in space power systems [2]. However, they produce lithium oxide (Li2O), which boils at 2800 K at 1 atm and hence at a lower temperature in vacuum. Fortunately, there exist many mixtures that release a lot of heat and form only condensed products during the combustion. Many such mixtures have been used for self-propagating high-temperature synthesis (SHS) of various materials [3, 4]. For the application discussed here, t itanium/boron (1:2 mole ratio) mixture appears to be particularly promising. The specific energy is 4.0 MJ/kg (1.1 kWh/kg), the adiabatic flame temperature is about 3200 K, and the reaction forms solid titanium diboride (TiB2, melting point: 3500 K). The mixture can be ignited easily with a heated tungsten wire, and it has been used widely as a booster to ignite the main mixture in the SHS process.Estimates: Assuming that specific heat of regolith is 500 J/(kg∙K) [5] and all generated heat is transferred to regolith, 12.5 kg of the Ti/B mixture would increase the temperature of 1000 kg of regolith by 100 K. To evaluate the rate of heat transfer in the regolith, a spherical model was analyzed where the heat released by a 12.5 kg Ti/B core propagates by thermal conduction through a 1000 kg regolith shell with no heat loss from its outer surface. At a bulk density of 1500 kg/m3 [5], the radius of the shell was 54 cm, while the radius of the core was about 11 cm. The calculations were conducted using Thermal Desktop SINDA/FLUINT (Cullimore and Ring Technologies) software at two constant values of bulk thermal conductivityk of the regolith: 0.001 and 0.01 W/(m∙K). The results show that after 14.5 days the core lost 31% of the released heat at the lower k and 77% at the higher k. At a distance of 20 cm from the core surface, the temperature of the regolith increased by only 1 K at the lower k and by 132 K at the higher k. In reality, the regolith near the heat source will be melted, so its thermal conductivity will increase significantly. Nevertheless, the conducted estimates indicate that combustion-based heat generators, placed directly in the regolith, could provide heat during a rather long period such as the lunar night.Conclusion: Heat generators based on gasless combustion of highly energetic reactive mixtures could be installed directly in the surface layer of lunar regolith. Because of the low thermal conductivity of the regolith, such generators would keep thermal energy for days and gradually supply heat to a rover/lander.Acknowledgment: The material presented in this work is based upon the work supported by National Aeronautics and Space Administration (NASA) under Grant #80NSSC20K0293.References: [1] Balasubramaniam R. et al. (2011) J. Thermophys. Heat Trans., 25,130−139. [2] Blair R.G. and Vasu S.S. (2022) Conf. Advanced Power Systems for Deep Space Exploration. [3] Varma A. et al. (1998) Adv. Chem. Eng., 24,79−226. [4] Levashov E.A. et al. (2017) Int. Mater. Rev., 62,203−239. [5] Wood-Robinson R. et al. (2019) J. Geophys. Res. Planets, 124, 1989−2011.
lunar↗
The temperature gradient in the solar nebula
The available compositional data on planets and satellites can be used to place stringent limits on the thermal environment in the solar nebula. The densities of the terrestrial planets, Ceres and Vesta, the Galilean satellites, and Titan; the atmospheric compositions of several of these bodies; and geochemical and geophysical data on the earth combine to define a strong dependence of formation temperature on heliocentric distance. It is impossible to reconcile the available compositional data with any model in which the formation temperatures of these bodies are determined by radiative equilibrium with the sun, regardless of the sun's luminosity. Rather, the data support Cameron's hypothesis of a dense, convective solar nebula, opaque to solar radiation, with an adiabatic temperature-pressure profile.
Lewis, J. S.↗
Validation of chemistry models employed in a particle simulation method
The chemistry models employed in a statistical particle simulation method, as implemented in the Intel iPSC/860 multiprocessor computer, are validated and applied. Chemical relaxation of five-species air in these reservoirs involves 34 simultaneous dissociation, recombination, and atomic-exchange reactions. The reaction rates employed in the analytic solutions are obtained from Arrhenius experimental correlations as functions of temperature for adiabatic gas reservoirs in thermal equilibrium. Favorable agreement with the analytic solutions validates the simulation when applied to relaxation of O2 toward equilibrium in reservoirs dominated by dissociation and recombination, respectively, and when applied to relaxation of air in the temperature range 5000 to 30,000 K. A flow of O2 over a circular cylinder at high Mach number is simulated to demonstrate application of the method to multidimensional reactive flows.
Haas, Brian L.↗
Effects of Structure and Hydrodynamics on the Sooting Behavior of Spherical Microgravity Diffusion Flames
Recent experimental, numerical and analytical work has shown that the stoichiometric mixture fraction (Z(sub st)) can have a profound effect on soot formation in diffusion flames. These findings were obtained at constant flame temperature (T(sub ad)), employing the approach described in Du and Axelbaum (1995, 1996). For example, a fuel mixture containing 1 mole of ethylene and 11.28 moles of nitrogen burning in pure oxygen ((Z(sub st)) = 0.78) has the same adiabatic flame temperature (2370 K) as that of pure ethylene burning in air ((Z(sub st)) = 0.064). An important finding of these works was that at sufficiently high (Z(sub st)), flames remain blue as strain rate approaches zero in counterflow flames, or as flame height and residence time approach infinity in coflowing flames. Lin and Faeth (1996a) coined the term permanently blue to describe such flames. Two theories have been proposed to explain the appearance of permanently-blue flames at high (Z(sub st)). They are based on (1) hydrodynamics and (2) flame structure. Previous experimental studies in normal gravity are not definitive as to which, if either, mechanism is dominant because both hydrodynamics and structure suppress soot formation at high (Z(sub st)) in coflowing and counterflowing diffusion flames. In counterflow flames with (Z(sub st)) < 0.5 streamlines at the flame sheet are directed toward the fuel. Newly formed soot is convected into richer regions, favoring soot growth over oxidation. For (Z(sub st)) > 0.5, convection at the flame is toward the oxidizer, thus enhancing soot oxidization. Thus, in counterflow flames, hydrodynamics causes soot to be convected towards the oxidizer at high (Z(sub st)) which suppresses soot formation. Axelbaum and co-workers maintain that while the direction of convection can impact soot growth and oxidation, these processes alone cannot cause permanently-blue flames. Soot growth and oxidation are dependent on the existence of soot particles and the presence of soot is invariably accompanied by yellow luminosity. Soot-particle inception, on the other hand, arises from gas-phase reactions and its dependence on flow direction is weak, similar to that of other gas-phase reactions in flames. For example, when the flame moves across the stagnation plane no significant changes in flame chemistry are observed. Furthermore, since the soot-inception zone has a finite thickness, soot has been produced in counterflow flames with (Z(sub st)) > 0.5. For large (Z(sub st)) the fuel concentration decreases and oxygen concentration increases in the soot forming regions of the flame. This yields a shift in the OH profile toward the fuel side of the flame, and this shift can dramatically influence soot inception because it essentially narrows the soot inception zone. Soot-free (permanently-blue) conditions can be realized when the structure of the flame is adjusted to the extent that significant oxidizing species exist on the fuel side of the flame at temperatures above the critical temperature for soot inception, ca. 1250 K. In previously considered flames it was impossible to independently vary flame structure and convection direction. In contrast, spherical diffusion flames (which generally require microgravity) allow both properties to be varied independently. We altered structure (Z(sub st)) by exchanging inert between the oxidizer and the fuel and we independently varied convection direction at the flame sheet by interchanging the injected and ambient gases. In this work we established four flames: (a) ethylene issuing into air, (b) diluted ethylene issuing into oxygen, (c) air issuing into ethylene, and (d) oxygen issuing into diluted ethylene. (Z(sub st)) is 0.064 in flames (a) and (c) and 0.78 in flames (b) and (d). The convection direction is from fuel to oxidizer in flames (a) and (b) and from oxidizer to fuel in flames (c) and (d). Under the assumption of equal diffusivities of all species and heat, the stoichiometric contours of these flames have identical temperatures and nitrogen concentrations.
Sunderland, P. B.↗
Effects of C/O Ratio and Temperature on Sooting Limits of Spherical Diffusion Flames
Limiting conditions for soot particle inception in spherical diffusion flames were investigated numerically. The flames were modeled using a one-dimensional, time accurate diffusion flame code with detailed chemistry and transport and an optically thick radiation model. Seventeen normal and inverse flames were considered, covering a wide range of stoichiometric mixture fraction, adiabatic flame temperature, residence time and scalar dissipation rate. These flames were previously observed to reach their sooting limits after 2 s of microgravity. Sooting-limit diffusion flames with scalar dissipation rate lower than 2/s were found to have temperatures near 1400 K where C/O = 0.51, whereas flames with greater scalar dissipation rate required increased temperatures. This finding was valid across a broad range of fuel and oxidizer compositions and convection directions.
Lecoustre, V. R.↗
Performance of J33-A-27 Turbojet-Engine Compressor: Center for Infrastructure Engineering Studies - 1
The J33-A-27 compressor was operated at an inlet pressure of 14 inches of mercury absolute and ambient inlet temperature over a range of equivalent impeller speeds from 6100 to 11,800 rpm. At the design equivalent speed of 11,800 rpm, the J33-A-27 compressor had a peak pressure ratio of 4.40 at an equivalent weight flow of 105.7 pounds per second and a peak adiabatic temperature-rise efficiency of 0.745. The maximum equivalent weight flow at design speed was 113.5 pounds per second.
Kovach, Karl↗
Simplified Model and Approach to Transform Infrared Surface Temperature to Film Effectiveness in a Conjugate Heat Transfer Experiment
This paper describes a simplified engineering model based on a one-dimensional thermal resistance network. The model is used to develop a new method to relate film cooling effectiveness and heat transfer augmentation to local overall cooling effectiveness in a conjugate flat plate experiment. This paper presents experimental proof-of-concept data to demonstrate the potential for this model. In contrast to previous approaches, neither the wall heat flux nor the adiabatic wall temperature is required to estimate the local film cooling performance parameters. The model predicts surface temperatures that are within the experimental uncertainties over the range for which the model is trained, and to within five percent when the model is extrapolated to higher coolant channel Reynolds numbers. This paper is relevant to conjugate test rigs that can measure the hot surface temperature distribution with and without film cooling. This information may also be relevant to designers as a method to approximate surface temperatures or used as an approximate heat transfer model for optimization studies.
advanced gas turbines↗
Nitric oxide formation in a lean, premixed-prevaporized jet A/air flame tube: An experimental and analytical study
An experimental and analytical study was performed on a lean, premixed-prevaporized Jet A/air flame tube. The NO(x) emissions were measured in a flame tube apparatus at inlet temperatures ranging from 755 to 866 K (900 to 1100 F), pressures from 10 to 15 atm, and equivalence ratios from 0.37 to 0.62. The data were then used in regressing an equation to predict the NO(x) production levels in combustors of similar design. Through an evaluation of parameters it was found that NO(x) is dependent on adiabatic flame temperature and combustion residence time, yet independent of pressure and inlet air temperature for the range of conditions studied. This equation was then applied to experimental data that were obtained from the literature, and a good correlation was achieved.
Lee, Chi-Ming↗