Search NASA⌕ Search

SEARCH · Search NASA

Results for “temperature attack”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Cyclic Oxidation and Hot Corrosion of NiCrY-Coated Disk Superalloys

Powder metallurgy disk superalloys have been designed for higher engine operating temperatures through improvement of their strength and creep resistance. Yet, increasing disk application temperatures to 704 degrees Centigrade and higher could enhance oxidation and activate hot corrosion in harmful environments. Protective coatings could be necessary to mitigate such attack. Cylindrical coated specimens of disk superalloys LSHR and ME3 were subjected to thermal cycling to produce cyclic oxidation in air at a maximum temperature of 760 degrees Centigrade. The effects of substrate roughness and coating thickness on coating integrity after cyclic oxidation were considered. Selected coated samples that had cyclic oxidation were then subjected to accelerated hot corrosion tests. This cyclic oxidation did not impair the coating's resistance to subsequent hot corrosion pitting attack.

protective coating↗
NASA NTRS1974

Lee surface flow phenomena over space shuttle at large angles of attack at M sub infinity equal 6

Surface pressure and heat transfer, flow separation, flow field, and oil flow patterns on the leeward side of a space shuttle orbiter model are investigated at a free stream Mach number of 6. The free stream Reynolds numbers are between 1.64 times 10 to the 7th power and 1.31 times 10 to the 8th power per meter, and the angle of attack is varied between 0 deg and 40 deg for the present experiments. The stagnation temperatures for the tests are approximately 500 K and the wall temperature is maintained at 290 K. Existing numerical methods of three-dimensional inviscid supersonic flow theory and compressible boundary layer theory are used to predict the present experimental measurements. Results of the present tests indicate two distinct types of flow separation and surface peak heating depending on the angle of attack.

Zakkay, V.↗
NASA NTRS2001

Qualitative Assessment of the Acoustic Disturbance Environment in the NASA LaRC 20-Inch MACH 6 Wind Tunnel

An experimental investigation was conducted on a 5-degree-half-angle cone with a flare in a conventional Mach 6 wind tunnel to examine the effect of facility noise on boundary layer transition. The effect of tunnel noise was inferred by comparing transition onset locations determined from the present test to that previously obtained in a Mach 6 quiet tunnel. Together, the two sets of experiments are believed to represent the first direct comparison of transition onset between a conventional and a quiet hypersonic wind tunnel using a common test model. In the present conventional hypersonic tunnel experiment, adiabatic wall temperatures were measured and heat transfer distributions were inferred on the cone flare model at zero degree angle of attack over a range of length Reynolds numbers (2 x 10(exp 6) to 10 x 10(exp 6)) which resulted in laminar and turbulent flow. Wall-to-total temperature ratio for the transient heating measurements and the adiabatic wall temperature measurements were 0.69 and 0.86, respectively. The cone flare nosetip radius was varied from 0.0001 to 0.125-inch to examine the effects of bluntness on transition onset. At comparable freestream conditions the transition onset Reynolds number obtained on the cone flare model in the conventional "noisy" tunnel was approximately 25% lower than that measured in the low disturbance tunnel.

Horvath, Thomas J.↗
NASA NTRS1979

Effects of precursor heating on radiative and chemically reacting viscous flow around a Jovian entry body

The influence of change in the precursor region flow properties on the entire shock layer flow phenomena around a Jovian entry body was investigated. The flow in the shock layer was assumed to be steady, axisymmetric, and viscous. Both the chemical equilibrium and the nonequilibrium composition of the shock layer gas were considered. The effects of transitional range behavior were included in the analysis of high altitude entry conditions. Realistic thermophysical and radiation models were used, and results were obtained by employing the implicit finite difference technique in the shock layer and an iterative procedure for the entire shock layer precursor zone. Results obtained for a 45 degree angle hyperboloid blunt body entering Jupiter's atmosphere at zero angle of attack indicates that preheating the gas significantly increases the static pressure and temperature ahead of the shock for entry velocities exceeding 36 km/sec. The nonequilibrium radiative heating rate to the body is found to be significantly higher than the corresponding equilibrium heating. The precursor heating generally increases the radiative and convective heating of a body. That increase is slightly higher for the nonequilibrium conditions.

Tiwari, S. N.↗
NASA NTRS1981

Evaluation of a pneumatic boot deicing system on a general aviation wing model

The aerodynamic characteristics of a typical modern general aviation airfoil were investigated with and without a pneumatic boot ice protection system. The ice protection effectiveness of the boot was studied. This includes the change in drag on the airfoil with the boot inflated and deflated, the change in drag due to primary and residual ice formation, drag change due to cumulative residual ice formation, and parameters affecting boot effectiveness. Boot performance was not affected by tunnel total temperature or velocity. Marginal effect in performance was associated with angle of attack. Significant effects on performance were caused by variations in droplet size, LWC, ice cap thickness inflation pressure, and surface treatment.

Albright, A. E.↗
NASA NTRS1991

Calibration of the ER-2 meteorological measurement system

The Meteorological Measurement System (MMS) on the high altitude ER-2 aircraft was developed specifically for atmospheric research. The MMS provides accurate measurements of pressure, temperature, wind vector, position (longitude, latitude, altitude), pitch, roll, heading, angle of attack, angle of sideslip, true airspeed, aircraft eastward velocity, northward velocity, vertical acceleration, and time, at a sample rate of 5/s. MMS data products are presented in the form of either 5 or 1 Hz time series. The 1 Hz data stream, generally used by ER-2 investigators, is obtained from the 5 Hz data stream by filtering and desampling. The method of measurement of the meteorological parameters is given and the results of their analyses are discussed.

Bowen, Stuart W.↗
NASA NTRS1994

STOVL CFD model test case

The transitional flight characteristics of a geometrically simplified Short Take-Off Vertical Landing (STOVL) aircraft configuration have been measured in the NASA Ames 7- by 10-Foot Wind Tunnel. The experiment is the first in a sequence of tests designed to provide detailed data for evaluating the capability of computational fluid dynamics methods to predict the important flow parameters for powered lift. The model consists of a 60 deg cropped delta wing platform, blended fuselage and two circular in-line jets that exit perpendicularly from the flat lower surface. The measured flows have a maximum freestream Mach number of 0.2. Model angle of attack is varied between -10 and +20 deg. The flow is ambient temperature in both jet exits and the nozzle pressure ratios are varied between 1 and 3. The data presented includes forces and moments, pressures measured at 281 surface pressure ports and the pressures of the jets. Measurements of the flow are also made in the tunnel test section upstream and downstream of the model and at the jet exits to guide boundary condition selection for the planned computations. Flow visualization and total pressure measurements in the jet plumes provide a description of the three-dimensional jet efflux flowfield.

Roth, Karlin R.↗
NASA NTRS2007

Aeroheating Analysis for the Mars Reconnaissance Orbiter with Comparison to Flight Data

The aeroheating environment of the Mars Reconnaissance Orbiter (MRO) has been analyzed using the direct simulation Monte Carlo and free-molecular techniques. The results of these analyses were used to develop an aeroheating database to be used for the preflight planning and the in-flight operations support for the aerobraking phase of the MRO mission. The aeroheating predictions calculated for the MRO include the heat transfer coefficient (CH) over a range of angles-of-attack, sideslip angles, and number densities. The effects of flow chemistry, surface temperature, and surface grid resolution were also investigated to determine the aeroheating database uncertainties. Flight heat flux data has been calculated from surface temperature sensor data returned to Earth from the MRO in orbit around Mars during the aerobraking phase of its mission. The heat flux data have been compared to the aeroheating database and agree favorably.

Liechty, Derek S.↗
NASA NTRS2017

Coatings for Oxidation and Hot Corrosion Protection of Disk Alloys

Increasing temperatures in aero gas turbines is resulting in oxidation and hot corrosion attack of turbine disks. Since disks are sensitive to low cycle fatigue (LCF), any environmental attack, and especially hot corrosion pitting, can potentially seriously degrade the life of the disk. Application of metallic coatings are one means of protecting disk alloys from this environmental attack. However, simply the presence of a metallic coating, even without environmental exposure, can degrade the LCF life of a disk alloy. Therefore, coatings must be designed which are not only resistant to oxidation and corrosion attack, but must not significantly degrade the LCF life of the alloy. Three different Ni-Cr coating compositions (29, 35.5, 45wt. Cr) were applied at two thicknesses by Plasma Enhanced Magnetron Sputtering (PEMS) to two similar Ni-based disk alloys. One coating also received a thin ZrO2 overcoat. The coated samples were also given a short oxidation exposure in a low PO2 environment to encourage chromia scale formation. Without further environmental exposure, the LCF life of the coated samples, evaluated at 760C, was less than that of uncoated samples. Hence, application of the coating alone degraded the LCF life of the disk alloy. Since shot peening is commonly employed to improve LCF life, the effect of shot peening the coated and uncoated surface was also evaluated. For all cases, shot peening improved the LCF life of the coated samples. Coated and uncoated samples were shot peened and given environmental exposures consisting of 500 hrs of oxidation followed by 50 hrs of hot corrosion, both at 760C). The high-Cr coating showed the best LCF life after the environmental exposures. Results of the LCF testing and post-test characterization of the various coatings will be presented and future research directions discussed.

LCF life↗
NASA NTRS2018

Effect of Pre- and Post-Coat Processing on the Fatigue Life of Coated Disk Alloys

Increasing temperatures in aero gas turbines is resulting in oxidation and hot corrosion attack of turbine disks. Since disks are sensitive to low cycle fatigue (LCF), any environmental attack, and especially hot corrosion pitting, can seriously degrade the life of the disk. Application of metallic coatings is one means of protecting disk alloys from this environmental attack. However, since LCF is sensitive to surface conditions, pre- and post-coat processing can have a significant effect on the LCF life of coated bars. Various pre-and post-coating conditions were examined with a Ni-45wt. Cr coating applied by High-power impulse magnetron sputtering (HiPiMS) to a Ni-based disk alloy. Initial pre-coat surface conditions examined a grit blasted surface. Later pre-coat surface treatments involved wet blasting, two shot peening levels (8N-200 and 16N-200) and a highly polished surface. Post-coat treatments involved two shot peening levels (4N-100 and 16N-200) and a post-coat diffusion anneal in high purity Ar or a low PO2 environment to encourage chromia scale formation. Half of the coated and uncoated bars were LCF tested at 760C without further environmental exposure to evaluate the pre- and post-coat treatments. The second half of samples were either oxidized for 500 hours at 760C in air, hot corroded for 50 hours at 760C in air using a Na2SO4-MgSO4 salt, or subjected to both exposures. Results of the LCF testing and post-test characterization of the various coatings will be presented and future research directions discussed.

LCF Life↗
NASA NTRS2019

LCF Life of As-Deposited and Annealed NiCr-Y Coatings for Oxidation and Hot Corrosion Protection of Disk Alloys

Increasing temperatures in aero gas turbines is resulting in oxidation and hot corrosion attack of turbine disks. Since disks are sensitive to low cycle fatigue (LCF), any environmental attack, and especially hot corrosion pitting, can seriously degrade the life of the disk. Application of metallic coatings is one means of protecting disk alloys from this environmental attack. However, the presence of a metallic coating can degrade the LCF life of a disk alloy. Therefore, coatings must be designed which are not only resistant to oxidation and corrosion attack, but do not significantly degrade the LCF life of the alloy.Three different NiCr-Y coating compositions (29, 35.5, 44 wt.% Cr, all with 0.1 wt.% Y) were applied at two thicknesses by Plasma Enhanced Magnetron Sputtering (PEMS) to two similar Ni-based disk alloys. One Ni-35.5Cr-0.1Y coating also received a thin ZrO2 overcoat. The coated samples were also given a short thermal anneal in a low PO2 environment to encourage bonding of the coating and substrate as well as initiating formation of a chromia scale. Without further environmental exposure, the LCF life of coated and uncoated samples was evaluated at 760°C in air. The LCF lifetime of all coated samples was less than that of uncoated samples. The LCF life scaled with the Cr content and the high-Cr, thin coating showed the highest LCF life. Pre and post-test characterization of the various coatings, including identification of crack initiation sites, will be presented and the effect of the coating on the LCF life discussed.

low cycle fatigue↗
NASA NTRS2011

Effect of Environmental Exposures on Fatigue Life of P/M Disk Superalloys

As the temperature capability of Ni-base superalloy powder metallurgy disks is steadily increased, environmental resistance and protection of advanced nickel-based turbine disk components are becoming increasingly important. Localized surface hot corrosion attack and damage from oxidation have been shown to impair disk fatigue life and may eventually limit disk operating temperatures. NASA Research Announcement (NRA) contracts have been awarded to GE Aviation and Honeywell Aerospace to separately develop fatigue resistant metallic and ceramic coatings for corrosion resistance and the corrosion/fatigue results of selected coatings will be presented. The microstructural response of a bare ME3 disk superalloy has been evaluated for moderate (704 C) and aggressive (760-816 C) oxidizing exposures up to 2,020 hours. Cross section analysis reveals sub-surface damage (significant for aggressive exposures) that consists of Al2O3 "fingers", interfacial voids, a recrystallized precipitate-free layer and GB carbide dissolution. The effects of a Nichrome corrosion coating on this microstructural response will also be presented.

Draper, Susan↗
NASA NTRS1992

Unsteady separation in sharp fin-induced shock wave/turbulent boundary layer interaction at Mach 5

Fluctuating wall-pressure measurements are made in shock-wave/turbulent-boundary-layer interactions generated by sharp/unswept fins at angles of attack of 16, 18, 20, 22, 24, 26, and 28 degrees at Mach 5. The experiment was conducted under approximately adiabatic wall temperature conditions. The mean and rms pressure distributions can be collapsed in conical coordinates. The wall-pressure signal near separation is intermittent for all angles of attack (16-28 deg) and is qualitatively similar to that measured in unswept flows. However, the shock frequencies are higher - about 5 kHz compared to 0.5-1 kHz. Over the range of sweepbacks examined, from 25-55 deg, the spectral content of the fluctuating pressures does not change. Thus, the increase in separation-shock frequency from 1 to 5 kHz occurs at lower interaction sweepback and is not a continuous process with increasing sweepback. Power spectra at the position of maximum rms in the intermittent region for interactions in different incoming boundary layers have the same center frequency. The maximum rms in the intermittent region correlates with interaction sweepback, not with overall inviscid pressure rise.

Schmisseur, J. D.↗
NASA NTRS1960

Mixing Characteristics Downstream of Core Region of High-Temperature Axisymmetric Jets Exhausting Into Transonic and Supersonic Streams

A series of rocket motors with varying exit to throat area ratios was tested in the 8- by 6-foot wind tunnel to determine the effects of mixing on jet diameter and temperature decay at large distances (x/d > 30) from the nozzle exit. An approximate method to account for effects of the initial expansion was evolved. It was determined that the combustion efficiency has an important effect on jet spreading, since the unburned products can burn downstream of the nozzle. The data showed considerable scatter; however, mixing rates were, in general, lower than those observed for subsonic jets. Data for angles of attack of 5 and 10 deg are also presented, giving the respective centerline shift and temperature decay as a function of axial distance.

Huff, Ronald G.↗
NASA NTRS2009

The Active Oxidation of Silicon Carbide

The high temperature oxidation of silicon carbide occurs in two very different modes. Passive oxidation forms a protective oxide film which limits further attack of the SiC: SiC(s) + 3/2 O2(g) = SiO2(s) + CO(g) Active oxidation forms a volatile oxide and may lead to extensive attack of the SiC: SiC(s) + O2(g) = SiO(g) + CO(g) Generally passive oxidation occurs at higher oxidant pressures and active oxidation occurs at lower oxidant pressures and elevated temperatures. Active oxidation is a concern for reentry, where the flight trajectory involves the latter conditions. Thus the transition points and rates of active oxidation are a major concern. Passive/active transitions have been studied by a number of investigators. An examination of the literature indicates many questions remain regarding the effect of impurity, the hysteresis of the transition (i.e. the difference between active-to-passive and passive-toactive), and the effect of total pressure. In this study we systematically investigate each of these effects. Experiments were done in both an alumina furnace tube and a quartz furnace tube. It is known that alumina tubes release impurities such as sodium and increase the kinetics in the passive region [1]. We have observed that the active-to-passive transition occurs at a lower oxygen pressure when the experiment is conducted in alumina tubes and the resultant passive silica scale contains sodium. Thus the tests in this study are conducted in quartz tubes. The hysteresis of the transition has been discussed in the detail in the original theoretical treatise of this problem for pure silicon by Wagner [2], yet there is little mention of it in subsequent literature. Essentially Wagner points out that the active-to-passive transition is governed by the criterion for a stable Si/SiO2 equilibria and the passive-to-active transition is governed by the decomposition of the SiO2 film. A series of experiments were conducted for active-to-passive and passive-to-active transitions by increasing and decreasing oxygen pressure, respectively. For pure silicon a dramatic difference was found; whereas for SiC the difference was not as great. This may be due to the oxidation of the carbon in SiC which may break down the scale [3]. The third area is the effect of total pressure. In the literature, low oxygen potentials are achieved via either low total pressure or low oxygen pressure in an O2/Ar mixture. Both types of experiments are done in this study and the differences are discussed with regard to the presence or absence of a boundary layer.

Jacobson, Nathan S.↗
NASA NTRS1975

Experimental and theoretical study of shuttle lee-side heat transfer rates

The experimental program which was conducted in the Calspan 96-inch hypersonic shock tunnel to investigate what effect the windward surface temperature had on the heat transfer to the leeward surface of the space shuttle orbiter is discussed. Heat-transfer distributions, surface-pressure distributions, and schlieren photographs were obtained for an 0.01-scale model of the 139 configuration space shuttle orbiter at angles-of-attack of 30 and 40 deg. Similar data were obtained for an 0.01 scale wingless model of the 139 configuration at angles-of-attack of 30 and 90 deg. Data were obtained for Mach numbers from Reynolds numbers, and surface temperatures and compared with theoretical results.

Mruk, G. K.↗
NASA NTRS2005

Heat Transfer on a Flat Plate with Uniform and Step Temperature Distributions

Heat transfer associated with turbulent flow on a step-heated or cooled section of a flat plate at zero angle of attack with an insulated starting section was computationally modeled using the GASP Navier-Stokes code. The algebraic eddy viscosity model of Baldwin-Lomax and the turbulent two-equation models, the K- model and the Shear Stress Turbulent model (SST), were employed. The variations from uniformity of the imposed experimental temperature profile were incorporated in the computations. The computations yielded satisfactory agreement with the experimental results for all three models. The Baldwin- Lomax model showed the closest agreement in heat transfer, whereas the SST model was higher and the K-omega model was yet higher than the experiments. In addition to the step temperature distribution case, computations were also carried out for a uniformly heated or cooled plate. The SST model showed the closest agreement with the Von Karman analogy, whereas the K-omega model was higher and the Baldwin-Lomax was lower.

Bahrami, Parviz A.↗
NASA NTRS1971

Time dependent shear stress and temperature distribution over an insulated flat plate moving at hypersonic speed.

The laminar two-dimensional flow over a stepwise accelerated flat plate moving with hypersonic speed at zero angle of attack is analysed. The governing equations in the self-similar form are linearized and solved numerically for small times. The solutions obtained are the deviations of the velocity and the temperature profiles from those of steady state. The presented results may be used to find the first order boundary layer induced pressure on the plate.

Rodkiewicz, C. M.↗