Results for “load balancing” — Page 25

NASA NTRS1980

Selected advanced aerodynamics and active controls technology concepts development on a derivative B-747

The feasibility of applying wing tip extensions, winglets, and active control wing load alleviation to the Boeing 747 is investigated. Winglet aerodynamic design methods and high speed wind tunnel test results of winglets and of symmetrically deflected ailerons are presented. Structural resizing analyses to determine weight and aeroelastic twist increments for all the concepts and flutter model test results for the wing with winglets are included. Control law development, system mechanization/reliability studies, and aileron balance tab trade studies for active wing load alleviation systems are discussed. Results are presented in the form of incremental effects on L/D, structural weight, block fuel savings, stability and control, airplane price, and airline operating economics.

Source record↗

NASA NTRS1999

Development of a 5-Component Balance for Water Tunnel Applications

The principal objective of this research/development effort was to develop a multi-component strain gage balance to measure both static and dynamic forces and moments on models tested in flow visualization water tunnels. A balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The balance mounts internally in the model and is used in a manner typical of wind tunnel balances. The key differences between a water tunnel balance and a wind tunnel balance are the requirement for very high sensitivity since the loads are very low (typical normal force is 90 grams or 0.2 lbs), the need for water proofing the gage elements, and the small size required to fit into typical water tunnel models. The five-component balance was calibrated and demonstrated linearity in the responses of the primary components to applied loads, very low interactions between the sections and no hysteresis. Static experiments were conducted in the Eidetics water tunnel with delta wings and F/A-18 models. The data were compared to forces and moments from wind tunnel tests of the same or similar configurations. The comparison showed very good agreement, providing confidence that loads can be measured accurately in the water tunnel with a relatively simple multi-component internal balance. The success of the static experiments encouraged the use of the balance for dynamic experiments. Among the advantages of conducting dynamic tests in a water tunnel are less demanding motion and data acquisition rates than in a wind tunnel test (because of the low-speed flow) and the capability of performing flow visualization and force/moment (F/M) measurements simultaneously with relative simplicity. This capability of simultaneous flow visualization and for F/M measurements proved extremely useful to explain the results obtained during these dynamic tests. In general, the development of this balance should encourage the use of water tunnels for a wider range of quantitative and qualitative experiments, especially during the preliminary phase of aircraft design.

Suarez, Carlos J.↗

NASA NTRS2021

Seasonal Glacier and Snow Loading in Svalbard Recovered from Geodetic Observations

We processed time series from seven Global Navigation Satellite System (GNSS) stations and one Very Long Baseline Interferometry (VLBI) station in Svalbard. The goal was to capture the seasonal vertical displacements caused by elastic response of variable mass load due to ice and snow accumulation. We found that estimates of the annual signal in different GNSS solutions disagree by more than 3 mm which makes geophysical interpretation of raw GNSS time series problematic. To overcome this problem, we have used an enhanced Common Mode (CM) filtering technique. The time series are differentiated by the time series from remote station BJOS with known mass loading signals removed a priori. Using this technique, we have achieved a substantial reduction of the differences between the GNSS solutions. We have computed mass loading time series from a regional Climatic Mass Balance (CMB) and snow model that provides the amount of water equivalent at a 1 km resolution with a time step of 7 days. We found that the entire vertical loading signal is present in data of two totally independent techniques at a statistically significant level of 95%. This allowed us to conclude that the remaining errors in vertical signal derived from the CMB model are less than 0.2 mm at that significance level. Refining the land water storage loading model with a CMB model resulted in a reduction of the annual amplitude from 2:1 mm to 1:1 mm in the CM filtered time series, while it had only a marginal impact on raw time series. This provides a strong evidence that CM filtering is essential for revealing local periodic signals when a millimetre level of accuracy is required.

H P Kierulf↗

NASA NTRS2003

Buckling Of Long Compression-Loaded Anisotropic Plates Restrained Against Inplane Lateral and Shear Deformations

An approach for synthesizing buckling results and behavior for thin balanced and unbalanced symmetric laminates that are subjected to uniform axial compression loads and elastically restrained against inplane expansion, contraction, and shear deformation is presented. This approach uses a nondimensional analysis for infinitely long, flexurally anisotropic plates (coupling between bending and twisting) that are subjected to combined mechanical loads and is based on nondimensional parameters. In addition, nondimensional loading parameters are derived that account for the effects of the elastic inplane deformation restraints, membrane orthotropy, and membrane anisotropy on the induced prebuckling stress state. The loading parameters are used to determine buckling coefficients that include the effects of flexural orthotropy and flexural anisotropy. Many results are presented, for some selected laminates, that are intended to facilitate a structural designer's transition to the use of the generic buckling design curves that are presented and discussed in the paper. Several buckling response curves are presented that provide physical insight into the behavior for combined loads, in addition to providing useful design data. An example is presented that demonstrates the use of the generic design curves, which are applicable to a wide range of laminate constructions. The analysis approach and generic results indicate the effects and characteristics of laminate orthotropy and anisotropy in a very general and unifying manner.

Nemeth, Michael P.↗

NASA NTRSDate not supplied

Design Implications of Rotordynamics and Mass Balancing on a 1.4 MW Partially Superconducting Machine

To ensure that rotating machines operate without excessive bearing loads, vibration, and dynamic stresses, their design must consider rotordynamic response and provisions for mass balancing of rotors, even when their rotational speeds are modest. This paper presents a rotordynamics design study for a 1.4 MW, partially superconducting electric machine proposed for electrified aircraft propulsion – NASA’s High Efficiency Megawatt Motor (HEMM). The study includes the selection of mass balancing grade and mount and bearing stiffnesses to yield satisfactory critical speeds, deflection, and unbalance force, and predictions of the expected mass unbalance caused by the superconducting rotor coils. The impact of the machine’s number of rotor poles on expected mass unbalance is also quantified. Design decisions and lessons learned are discussed.

hybrid electric aircraft↗

NASA NTRSDate not supplied

Design Implications of Rotordynamics and Mass Balancing on a 1.4 MW Partially Superconducting Machine

To ensure that rotating machines operate without excessive bearing loads, vibration, and dynamic stresses, their design must consider rotordynamic response and provisions for mass balancing of rotors, even when their rotational speeds are modest. This paper presents a rotordynamics design study for a 1.4 MW, partially superconducting electric machine proposed for electrified aircraft propulsion – NASA’s High Efficiency Megawatt Motor (HEMM). The study includes the selection of mass balancing grade and mount and bearing stiffnesses to yield satisfactory critical speeds, deflection, and unbalance force, and predictions of the expected mass unbalance caused by the superconducting rotor coils. The impact of the machine’s number of rotor poles on expected mass unbalance is also quantified. Design decisions and lessons learned are discussed.

hybrid electric aircraft↗

NASA NTRS1985

Evaluation of a load cell model for dynamic calibration of the rotor systems research aircraft

The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission system from the fuselage. An analytical model of the relationship between applied rotor loads and the resulting load cell measurements is derived by applying a force-and-moment balance to the isolated rotor/transmission system. The model is then used to estimate the applied loads from measured load cell data, as obtained from a ground-based shake test. Using nominal design values for the parameters, the estimation errors, for the case of lateral forcing, were shown to be on the order of the sensor measurement noise in all but the roll axis. An unmodeled external load appears to be the source of the error in this axis.

Duval, R. W.↗

NASA NTRS1987

Aerodynamic measurements and thermal tests of a strain-gage balance in a cryogenic wind tunnel

An internal strain-gage balance designed and constructed in Europe for use in cryogenic wind tunnels has been tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. Part of the evaluation was made at equilibrium balance temperatures and it consisted of comparing the data taken at a tunnel stagnation temperature of 300 K with the data taken at 200 K and 110 K while maintaining either the Reynolds number or the stagnation pressure. A sharp-leading-edge delta-wing model was used to provide the aerodynamic loading for these tests. Results obtained with the balance during the force tests were found to be accurate and repeatable both with and without the use of a convection shield on the balance. An additional part of this investigation involved obtaining data on the transient temperature response of the balance during both normal and rapid changes in the tunnel stagnation temperature. The variation of the temperature with time was measured at three locations on the balance near the physical locations of the strain gages. The use of a convection shield significantly increased the time required for the balance to stabilize at a new temperature during the temperature response tests.

Boyden, Richmond P.↗

NASA NTRS1973

Fluid and Electrolyte Balance model (FEB)

The effects of various oral input water loads on solute and water distribution throughout the body are presented in the form of a model. The model was a three compartment model; the three compartments being plasma, interstitial fluid and cellular fluid. Sodium, potassium, chloride and urea were the only major solutes considered explicitly. The control of body water and electrolyte distribution was affected via drinking and hormone levels.

Fitzjerrell, D. G.↗

NASA NTRS1972

Role of distal reabsorption and peritubular environment in glomerulotubular balance.

Total kidney glomerulotubular balance was examined during aortic constriction and release in saline-loaded dogs and in dogs undergoing water diuresis. Aortic constriction lowered the glomerular filtration rate by 45% in both groups, and glomerulotubular balance, as judged by changes in absolute sodium reabsorption, was also comparable. During water diuresis, a linear relationship was observed between free water clearance and urine flow during all maneuvers, suggesting that distal sodium reabsorption is related primarily to distal delivery. The results suggest that if alterations in the peritubular environment are responsible for the changes in tubular sodium reabsorption during aortic constriction in the saline- or water-loaded dog, then a change in renal plasma flow, and presumably delivery rate of oncotic force, may be the most likely mediator.

Schrier, R. W.↗

NASA NTRS1995

Pick-up ion pressure gradients modulating the solar wind dynamics

Neutral interstellar atoms penetrate deeply into the inner heliosphere before they become ionized by various processes. As ions they are picked-up by the frozen-in magnetic fields and are convected outwards with the solar wind plasma. Thereby the primary plasma flow is mass, momentum, and energy-loaded. The dynamics of the distant multi-constituent solar wind is, however, not solely determined by these loading processes, but is also affected by the wave-mediated pick-up ion pressure gradients derivable from the pick-up ion distribution function. The action of the radial components of these pressures essentially counter balances the decelerating effect of the solar wind momentum loading, diminishing strongly the deceleration of the distant solar wind. Furthermore the latitudinal components of the pick-up ion pressures induce latitudinal forces acting on the multiconstituent solar plasma outflow and inducing nonradial bulk flow components. The enforced nonradial outflow geometry on the upwind hemisphere may partly be responsible for the magnetic flux deficit which was claimed since several years in the PIONEER-10 magnetic flux data.

Fahr, Hans J.↗

NASA NTRS1998

Development of a Rotor-Body Coupled Analysis for an Active Mount Aeroelastic Rotor Testbed

At the Langley Research Center an active mount rotorcraft testbed is being developed for use in the Langley Transonic Dynamics Tunnel. This testbed, the second generation version of the Aeroelastic Rotor Experimental System (ARES-II), can impose rotor hub motions and measure the response so that rotor-body coupling phenomena may be investigated. An analytical method for coupling an aeroelastically scaled model rotor system to the ARES-II is developed in the current study. Models of the testbed and the rotor system are developed in independent analyses, and an impedance-matching approach is used to couple the rotor system to the testbed. The development of the analytical models and the coupling method is examined, and individual and coupled results are presented for the testbed and rotor system. Coupled results are presented with and without applied hub motion, and system loads and displacements are examined. The results show that a closed-loop control system is necessary to achieve desired hub motions, that proper modeling requires including the loads at the rotor hub and rotor control system, and that the strain-gauge balance placed in the rotating system of the ARES-II provided the best loads results.

Wilbur, Matthew L.↗

NASA NTRS2016

Photogrammetric Deflection Measurements for the Tiltrotor Test Rig (TTR) Multi-Component Rotor Balance Calibration

Calibrating the internal, multi-component balance mounted in the Tiltrotor Test Rig (TTR) required photogrammetric measurements to determine the location and orientation of forces applied to the balance. The TTR, with the balance and calibration hardware attached, was mounted in a custom calibration stand. Calibration loads were applied using eleven hydraulic actuators, operating in tension only, that were attached to the forward frame of the calibration stand and the TTR calibration hardware via linkages with in-line load cells. Before the linkages were installed, photogrammetry was used to determine the location of the linkage attachment points on the forward frame and on the TTR calibration hardware. Photogrammetric measurements were used to determine the displacement of the linkage attachment points on the TTR due to deflection of the hardware under applied loads. These measurements represent the first photogrammetric deflection measurements to be made to support 6-component rotor balance calibration. This paper describes the design of the TTR and the calibration hardware, and presents the development, set-up and use of the photogrammetry system, along with some selected measurement results.

Calibration↗

NASA NTRS2016

Photogrammetric Deflection Measurements for the Tiltrotor Test Rig (TTR) Multi-Component Rotor Balance Calibration

Calibrating the internal, multi-component balance mounted in the Tiltrotor Test Rig (TTR) required photogrammetric measurements to determine the location and orientation of forces applied to the balance. The TTR, with the balance and calibration hardware attached, was mounted in a custom calibration stand. Calibration loads were applied using eleven hydraulic actuators, operating in tension only, that were attached to the forward frame of the calibration stand and the TTR calibration hardware via linkages with in-line load cells. Before the linkages were installed, photogrammetry was used to determine the location of the linkage attachment points on the forward frame and on the TTR calibration hardware. Photogrammetric measurements were used to determine the displacement of the linkage attachment points on the TTR due to deflection of the hardware under applied loads. These measurements represent the first photogrammetric deflection measurements to be made to support 6-component rotor balance calibration. This paper describes the design of the TTR and the calibration hardware, and presents the development, set-up and use of the photogrammetry system, along with some selected measurement results.

Calibration↗

NASA NTRS1992

Elastomeric load sharing device

An elastomeric load sharing device, interposed in combination between a driven gear and a central drive shaft to facilitate balanced torque distribution in split power transmission systems, includes a cylindrical elastomeric bearing and a plurality of elastomeric bearing pads. The elastomeric bearing and bearing pads comprise one or more layers, each layer including an elastomer having a metal backing strip secured thereto. The elastomeric bearing is configured to have a high radial stiffness and a low torsional stiffness and is operative to radially center the driven gear and to minimize torque transfer through the elastomeric bearing. The bearing pads are configured to have a low radial and torsional stiffness and a high axial stiffness and are operative to compressively transmit torque from the driven gear to the drive shaft. The elastomeric load sharing device has spring rates that compensate for mechanical deviations in the gear train assembly to provide balanced torque distribution between complementary load paths of split power transmission systems.

Isabelle, Charles J.↗

NASA NTRS1977

Rolling moments in a trailing vortex flow field

Pressure distributions are presented which were measured on a wing in close proximity to a tip vortex of known structure generated by a larger, upstream semispan wing. Overall loads calculated by integration of these pressures are checked by independent measurements made with an identical model mounted on a force balance. Several conventional methods of wing analysis are used to predict the loads on the following wing. Strip theory is shown to give uniformly poor results for loading distribution, although predictions of overall lift and rolling moment are sometimes acceptable. Good results are obtained for overall coefficients and loading distribution by using linearized pressures in vortex-lattice theory in conjunction with a rectilinear vortex. The equivalent relation from reverse-flow theory that can be used to give economic predictions for overall loads is presented.

Mcmillan, O. J.↗

NASA NTRS1977

Rolling moments in a trailing vortex flow field

Pressure distributions are presented which were measured on a wing in close proximity to a tip vortex of known structure generated by a larger, upstream semispan wing. Overall loads calculated by integration of these pressures are checked by independent measurements made with an identical model mounted on a force balance. Several conventional methods of wing analysis are used to predict the loads on the following wing. Strip theory is shown to give uniformly poor results for loading distribution, although predictions of overall lift and rolling moment are sometimes acceptable. Good results are obtained for overall coefficients and loading distribution by using linearized pressures in vortex-lattice theory in conjunction with a rectilinear vortex. The equivalent relation from reverse-flow theory that can be used to give economic predictions for overall loads is presented.

Mcmillan, O. J.↗

NASA NTRS1992

Citraturic response to oral citric acid load

It is possible that some orally administered citrate may appear in urine by escaping oxidation in vivo. To determine whether this mechanism contributes to the citraturic response to potassium citrate, we measured serum and urinary citrate for 4 hours after a single oral load of citric acid (40 mEq.) in 6 normal subjects. Since citric acid does not alter acid-base balance, the effect of absorbed citrate could be isolated from that of alkali load. Serum citrate concentration increased significantly (p less than 0.05) 30 minutes after a single oral dose of citric acid and remained significantly elevated for 3 hours after citric acid load. Commensurate with this change, urinary citrate excretion peaked at 2 hours and gradually decreased during the next 2 hours after citric acid load. In contrast, serum and urinary citrate remained unaltered following the control load (no drug). Differences of the citratemic and citraturic effects between phases were significant (p less than 0.05) at 2 and 3 hours. Urinary pH, carbon dioxide pressure, bicarbonate, total carbon dioxide and ammonium did not change at any time after citric acid load, and did not differ between the 2 phases. No significant difference was noted in serum electrolytes, arterialized venous pH and carbon dioxide pressure at any time after citric acid load and between the 2 phases. Thus, the citraturic and citratemic effects of oral citric acid are largely accountable by provision of absorbed citrate, which has escaped in vivo degradation.

Non-NASA Center↗