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NASA NTRS1977

Thrust reverser design studies for an over-the-wing STOL transport

Aerodynamic and acoustics analytical studies were conducted to evaluate three thrust reverser designs for potential use on commercial over-the-wing STOL transports. The concepts were: (1) integral D nozzle/target reverser, (2) integral D nozzle/top arc cascade reverser, and (3) post exit target reverser integral with wing. Aerodynamic flowpaths and kinematic arrangements for each concept were established to provide a 50% thrust reversal capability. Analytical aircraft stopping distance/noise trade studies conducted concurrently with flow path design showed that these high efficiency reverser concepts are employed at substantially reduced power settings to meet noise goals of 100 PNdB on a 152.4 m sideline and still meet 609.6 m landing runway length requirements. From an overall installation standpoint, only the integral D nozzle/target reverser concept was found to penalize nacelle cruise performance; for this concept a larger nacelle diameter was required to match engine cycle effective area demand in reverse thrust.

Ammer, R. C.↗

NASA NTRS1976

Reverse-thrust technology for variable-pitch fan propulsion systems

Tests conducted to develop the technology necessary to meet the unique reverse-thrust performance requirements of a variable pitch fan propulsion system are discussed. The losses and distortion associated with the air entering the fan and core compressor from the rear of the engine, the direction of fan blade pitch rotation for best reverse-thrust aeroacoustic performance, and engine response and operating characteristics during forward- to reverse-thrust transients are among the factors studied. The test results of several scale fan models as well as a full-size variable pitch fan engine are summarized. Results show the following: a flared exhaust nozzle makes a good reverse-thrust inlet; acceptable core inlet duct recovery and distortion levels in reverse flow were demonstrated; adequate thrust levels were achieved; forward- to reverse-thrust response time achieved was better than the goal; thrust and noise levels strongly favor reverse through feather pitch; and finally, flight-type inlets make the establishment of reverse flow more difficult.

Sagerser, D. A.↗

NASA NTRS1985

Static internal performance of a single-engine onaxisymmetric-nozzle vaned-thrust-reverser design with thrust modulation capabilities

An investigation has been conducted at wind-off conditions in the stati-test facility of the Langley 16-Foot Transonic Tunnel. The tests were conducted on a single-engine reverser configuration with partial and full reverse-thrust modulation capabilities. The reverser design had four ports with equal areas. These ports were angled outboard 30 deg from the vertical impart of a splay angle to the reverse exhaust flow. This splaying of reverser flow was intended to prevent impingement of exhaust flow on empennage surfaces and to help avoid inlet reingestion of exhaust gas when the reverser is integrated into an actual airplane configuration. External vane boxes were located directly over each of the four ports to provide variation of reverser efflux angle from 140 deg to 26 deg (measured forward from the horizontal reference axis). The reverser model was tested with both a butterfly-type inner door and an internal slider door to provide area control for each individual port. In addition, main nozzle throat area and vector angle were varied to examine various methods of modulating thrust levels. Other model variables included vane box configuration (four or six vanes per box), orientation of external vane boxes with respect to internal port walls (splay angle shims), and vane box sideplates. Nozzle pressure ratio was varied from 2.0 approximately 7.0.

Leavitt, L. D.↗

NASA NTRS1988

Thrust-reverser flow investigation on a twin-engine transport

An investigation was conducted in the NASA Langley 14 x 22 foot Subsonic Tunnel to study the effects of engine thrust reversing on an aft-mounted twin-engine transport and to develop effective testing techniques. Testing was done over a fixed and a moving-belt ground plane and over a pressure instrumented ground board. Free-stream dynamic pressure was set at values up to 12.2 psf, which corresponded to a maximum Reynolds number based on the mean aerodynamic chord of 765,000. The thrust reversers examined included cascade, target and four-door configurations. The investigation focused on the range of free-stream velocities and engine thrust-reverser flow rates that would be typical for landing ground-roll conditions. Flow visualization techniques were investigated, and the use of water or smoke injected into the reverser flow proved effective to determine the forward progression of the reversed flow and reingestion limits. When testing over a moving-belt ground plane, as opposed to a fixed ground plane, forward penetration of the reversed flow was reduced. The use of a pressure-instrumented ground board enabled reversed flow ground velocities to be obtained, and it provided a means by which to identify the reversed flow impingement point on the ground.

Gatlin, Gregory M.↗

NASA NTRS1956

Performance Characteristics of Cylindrical Target-type Thrust Reversers

From tests on cylindrical target-type thrust reversers, it was found that the reverser frontal area, lip angle, end-plate angle, and end-plate depth had important effects on reverse-thrust performance. Frontal area, reverser depth, lip angle, and end-plate angele had important effects on the spacing required for unrestricted nozzle flow. For reverse-thrust ratios greater than 64 percent, the reversed flow attached to the 7 degree cowl in quiescent air. Swept-type cylindrical reversers were generally unstable. The thrust-modulation characteristics of a cylindrical target-type thrust reverser were found to be satisfactory.

Steffen, Fred W↗

DOE OSTI2024

Flow reversal benchmark of a one-sided heated narrow rectangular channel with CATHARE and RELAP5

Flow reversal in narrow coolant channels can be a crucial phenomenon for the safety of research reactors with a downward nominal flow direction. During a loss of forced flow accident, the downward flow stagnates briefly before transitioning into an upward natural circulation flow. The fuel may be damaged if dryout occurs and threshold fuel and/or cladding temperatures are exceeded. A comprehensive study is provided for flow reversal in narrow rectangular channels by examining experimental data and conducting software model analyses. The literature on flow reversal was reviewed, and selected experimental datasets were used to benchmark against CATHARE and RELAP5 models and also compare the code calculations with each other. The experimental data comes from flow reversal tests conducted with a narrow rectangular channel with one-sided heating. The results were compared with experimental data for successful flow reversal tests and predicted dryout power for dryout conditions. Also, the study examined the effects of the pump coastdown period, inlet liquid temperature, system pressure, and localized pressure drops. The experimental results showed that shorter coastdown periods, reduced pressure drops, and lower coolant inlet temperatures increased the dryout power. However, the system pressure did not noticeably affect the results. The simulation results showed that both CATHARE and RELAP5 agreed with experimental data, capturing the trends of the experimental results. Slight differences between each code calculation, as well as the predicted and measured dryout powers, were attributed to experimental uncertainties and the modeling of physical phenomena such as wall nucleation, interfacial heat transfer, drag coefficients, and critical heat flux. Overall, this study provides an understanding of flow reversal and the prediction capabilities of thermal-hydraulics software models. In conclusion, a future study of the flow reversal benchmark of a narrow rectangular channel with two-sided heating may provide additional valuable insights.

CATHARE↗

NASA NTRS1972

Preliminary experiments on the noise generated by target-type thrust reverser models

Experiments are reported on the noise generated by model V-gutter and semicylindrical target-type reversers with circular nozzles. Nozzles were 5.24 and 7.78 cm in diameter. Nozzle pressure ratio ranged from 1.25 to 1.72. The spacing between reversers and nozzle, as well as the reverser orientation, was also varied. More noise was generated with reversers than with the nozzle alone. The measured maximum overall sound pressure level varied with the sixth power of the nozzle exit velocity. Noise levels were more uniform in regard to directivity with reversers than with the nozzle alone. It is concluded that thrust reversers, can be a significant noise problem, especially for STOL aircraft using thrust reversers during approach.

Gutierrez, O. A.↗

NASA NTRS1972

Noise generated by STOL core-jet thrust reversers.

This paper summarizes the results of an experimental investigation on the noise generated by target-type thrust reversers. The experimental data are normalized and scaled up to sizes suitable for reversing the core jets of a 45,400-kg augmentor-wing-type STOL airplane. The scaling calculatings yield perceived noise levels well above the 95-PNdB design goal for both sideline and flyover at 152.5 m. V-gutter and semicylindrical reversers were tested with a 5.24-cm-diameter circular nozzle, and a semicylindrical reverser was also tested with a 7.78-cm-diameter circular nozzle. Other test variables were the spacing between nozzle and reverser, reverser orientation, and nozzle pressure ratio. The thrust reversers, in addition to being noisier than the nozzle alone, also had a more uniform directivity.

Stone, J. R.↗

NASA NTRS1974

Results from cascade thrust reverser noise and suppression experiments

Results from experimental work on model scale cascade reversers with cold airflow are presented. Sound power level directivity and spectral characteristics for cascade reversers are reported. Effect of cascade exit area ratio, vane profile shape, and emission arc are discussed. Model equivalent diameters varied from 3 to 5 inches, pressure ratios range from 1.15 to 3.0. Depending on the reverser type, acoustic power was proportional to the 4 1/2 to 6th power of ideal jet velocity. Reverser noise peaked at higher frequency and was more omnidirectional than nozzle-alone jet noise. Appreciable reduction in sideline noise was obtained from plane shields. Airfoil-vaned cascades were the most aerodynamically efficient and least noisy reversers. Scaling of cascade reverser data to example aircraft engines showed all cascades above the 95 PNdB sideline goal from STOL aircraft. However, the airfoil-vaned reverser has a good potential for meeting this goal for high-bypass (low pressure ratio) exhausts.

Gutierrez, O. A.↗

NASA NTRS1982

Static internal performance characteristics of two thrust reverser concepts for axisymmetric nozzles

The statis performance of two axisymmetric nozzle thrust reverser concepts was investigated. A rotating vane thrust reverser represented a concept in which reversing is accomplished upstream of the nozzle throat, and a three door reverser concept provided reversing downstream of the nozzle throat. Nozzle pressure ratio was varied from 2.0 to approximately 6.0. The results of this investigation indicate that both the rotating vane and three door reverser concepts were effective static thrust spoilers with the landing approach nozzle geometry and were capable of providing at least a 50 percent reversal of static thrust when fully deployed with the ground roll nozzle geometry.

Leavitt, L. D.↗

NASA NTRS1985

On reversion phenomena in Cu-Zr-Cr alloys

Reversion phenomena in aged Cu-0.12% Zr-0.28% Cr alloy were investigated by means of resistivity measurement and transmission electron microscopy and compared with those of Cu-0.30% Zr and Cu-0.26% Cr alloys. Specimens in the form of a 0.5 mm sheet were solution-treated at 950 F for 1 hr water-quenched, aged, and finally reversed. The reversion phenomena were confirmed to exist in Cu-Zr and Cu-Zr-Cr alloys as well as Cu-Cr alloys, at aging temperatures of 300 to 500 F. The critical aging temperature for the reversion was not observed in all the alloys. Split aging increased the amount of reversion, particularly in Cu-Zr and Cu-Zr-Cr alloys, compared with that by conventional aging. The amount of reversion in Cu-Zr-Cr alloy was greatly affected by the resolution of Cr precipitate formed by preaging. Structural changes in Cu-Zr-Cr alloy due to the reversion were hardly observed by transmission electron microscopy.

Suzuki, H.↗

NASA NTRS1989

Static internal performance of a nonaxisymmetric vaned thrust reverser with flow splay capability

An investigation was conducted in the Static Test Facility of the Langley 16-Foot Transonic Tunnel on a dual-port, nonaxisymmetric, block-and-turn type thrust reverser model with vane cascades in the reverser ports which turned the flow in the splay direction and aided in turning the flow in the reverse direction. Splaying reverser flow is a method of delaying to lower landing ground roll speeds the reingestion of hot exhaust flow into the inlets. Exhaust flow splay can also help prevent the impingement of hot exhaust gases on the empennage surfaces when the reverser is integrated into an actual airframe. The vane cascades consisted of two sets of perpendicular vanes with a variable number of turning and splay vanes. A skewed vane box was also tested which had only one set of vanes angled to provide both turning and splay. Vane cascades were designed to provide different amounts of flow splay in the top and bottom ports. Inner doors, trim tabs, and an orifice plate all provided means of varying the port area for reverser flow modulation. The outer door position was varied as a means of influencing the flow reverse angle. Nozzle pressure ratio was varied from 1.75 to approximately 6.00.

Bangert, Linda S.↗

NASA NTRS1989

Reverse Algols

Reverse Algols, binary systems with a semidetached configuration in which the more massive component is in contact with the critical equipotential surface, are examined. Observational evidence for reverse Algols is presented and the parameters of seven reverse Algols are listed. The evolution of Algols and reverse Algols is discussed. It is suggested that, because reverse Algols represent the premass-reversal semidetached phase of close binary evolution, the evolutionary time scale between regular and reverse Algols is the ratio of the number of confirmed systems of these two Algol types.

Leung, K. C.↗

NASA NTRS2003

The Geomagnetic Field During a Reversal

By modifying the IGRF it is possible to learn what may happen to the geomagnetic field during a geomagnetic reversal. If the entire IGRF reverses then the declination and inclination only reverse when the field strength is zero. If only the dipole component of the IGRF reverses a large geomagnetic field remains when the dipole component is zero and he direction of the field at the end of the reversal is not exactly reversed from the directions at the beginning of the reversal.

Heirtzler, James R.↗

NASA NTRS1998

Static Performance of a Wing-Mounted Thrust Reverser Concept

An experimental investigation was conducted in the Jet-Exit Test Facility at NASA Langley Research Center to study the static aerodynamic performance of a wing-mounted thrust reverser concept applicable to subsonic transport aircraft. This innovative engine powered thrust reverser system is designed to utilize wing-mounted flow deflectors to produce aircraft deceleration forces. Testing was conducted using a 7.9%-scale exhaust system model with a fan-to-core bypass ratio of approximately 9.0, a supercritical left-hand wing section attached via a pylon, and wing-mounted flow deflectors attached to the wing section. Geometric variations of key design parameters investigated for the wing-mounted thrust reverser concept included flow deflector angle and chord length, deflector edge fences, and the yaw mount angle of the deflector system (normal to the engine centerline or parallel to the wing trailing edge). All tests were conducted with no external flow and high pressure air was used to simulate core and fan engine exhaust flows. Test results indicate that the wing-mounted thrust reverser concept can achieve overall thrust reverser effectiveness levels competitive with (parallel mount), or better than (normal mount) a conventional cascade thrust reverser system. By removing the thrust reverser system from the nacelle, the wing-mounted concept offers the nacelle designer more options for improving nacelle aero dynamics and propulsion-airframe integration, simplifying nacelle structural designs, reducing nacelle weight, and improving engine maintenance access.

Asbury, Scott C.↗

DOE OSTI2024

Reverse-Bias Resilience of Monolithic Perovskite/Silicon Tandem Solar Cells

Metal halide perovskites have rapidly enabled a range of high-performance photovoltaic technologies. However, catastrophic failure under reverse voltage bias hinders their commercialization. In this work, we demonstrate that by employing a monolithic perovskite/silicon tandem structure, the perovskite subcell can be effectively protected by the silicon subcell under reverse bias, owing to the low reverse-bias diode current of the silicon subcell. As a result, the tested perovskite/silicon tandem devices show superior reverse-bias resilience compared to perovskite single-junction devices in both long-term reverse voltage biasing tests at the single-cell level and partial shading tests at the module level. These results highlight that, compared to other perovskite technologies, monolithic perovskite/silicon tandems are at a higher technology readiness level in terms of tackling the reverse-bias and partial shading challenge, which is a considerable advantage towards commercialization.

commercialization↗

NASA NTRS1972

Effect of pictorial display configuration on the frequency of control reversals during aircraft landing approaches

A fixed-base simulator study to determine the effect of increased pictorial display realism on the frequency of control reversals made with an inside-out landing display was conducted. Display conditions included the effects of collimation and scale (head-up versus head-down presentation), horizon symbology (simple line versus white-black sky-ground surfaces), and ground plane realism (computer generated perspective versus a TV picture of a realistic model). The number of control reversals was moderately high on all displays. Control reversals to roll disturbances occurred nearly twice as frequently as reversals to either pitch or lateral rate disturbances. Though there were no significant differences among the numbers of small control reversals for the different displays, there was some evidence that this conclusion may not apply to large control reversals.

Lincoln, R.↗

NASA NTRS1973

Experimental performance of cascade thrust reversers at forward velocity

A series of static and wind tunnel tests were performed on four cowl cascade thrust reverser configurations which had various reversed jet emission patterns applicable to an externally blown flap STOL aircraft. The work was performed using a model fan which was 14.0 cm in diameter and passed a fan mass flow of 2.49 kg/sec at an approximate fan pressure ratio of 1.22 and fan corrected rotational speed of 35,800 rpm. The tests demonstrated that the reingestion of fan flow significantly reduced the reverser efficiency and that the thrust reverser efficiency was improved by reducing the reversed jet azimuthal emmission angle. The reverser efficiency at STOL landing speeds was as high as 0.95; however, configurations with lateral emission were adversely affected by yawing the nacelle at forward velocity. Measurements of the internal static pressure at the stator exit showed significant increases in the local static pressure for configurations with reduced jet emission angles.

Dietrich, D. A.↗