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Tabulated pressure data are presented on the left upper wing surface of the integrated space shuttle vehicle configuration. For Vol. 1, see N76-15246.
Tabulated pressure data are presented on the right upper wing surface, right lower wing surface, and SRM booster of the integrated space shuttle vehicle configuration. For Vol. 1, see N76-15246.
Tabulated pressure data are presented on the external tank and miscellaneous orifices of the integrated space shuttle vehicle configuration. For Vol. 1, see N76-15246.
The design and capabilities of two digital controller systems for aeroelastic wind-tunnel models are described. The first allowed control of flutter while performing roll maneuvers with wing load control as well as coordinating the acquisition, storage, and transfer of data for on-line analysis. This system, which employs several digital signal multi-processor (DSP) boards programmed in high-level software languages, is housed in a SUN Workstation environment. A second DCS provides a measure of wind-tunnel safety by functioning as a trip system during testing in the case of high model dynamic response or in case the first DCS fails. The second DCS uses National Instruments LabVIEW Software and Hardware within a Macintosh environment.
Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.
Assigning capacity value to renewable energy sources (RES) is a challenge faced in planning their integration with the grid. The difficulties stem from the natural characteristics of variability and intermittency of wind and solar sources. The capacity credit (CC) analysis evaluates the system’s actual power output compared with a constant capacity generator, i.e., conventional generator and determines an effective capacity to use for planning and operation. Herein this paper presents different factors that could affect the CC of a system. Two methods are proposed to determine the CC, namely equivalent firm capacity (EFC) and effective load carrying capability (ELCC). Since these methods are based on satisfying reliability criteria, daily loss of load expectation (LOLE), hourly loss of load (LOLH), and expected energy not served (EENS) have been employed as indices. To obtain the CC value, both methods apply two techniques: traditional and optimization. Genetic algorithm (GA) is the optimization approach used in this paper. Then, this work compares the two techniques and shows the superior performance of the optimization approach. Two hybrid systems, stand-alone (SA) and grid-connected (GC) modes, are proposed and used as case studies. The hybrid systems consist of photovoltaic (PV), wind turbine (WT), and battery energy storage system (BESS). In this work, three different scenarios are used to compare capacity credit: system as a whole, only wind, and no batteries. Finally, sensitivity analysis is carried out to examine the impact of varying the wind speed, solar irradiation, and load. It is demonstrated that the choice of reliability index plays an important role in determining the capacity credit and it is shown that EENS is a more comprehensive and consistent index of reliability.
This paper proposes a method for the coordinated control of a wind turbine and an energy storage system (ESS). Because wind power (WP) is highly dependent on wind speed, which is variable, severe stability problems can be caused in power systems, especially when the WP has a high penetration level. To solve this problem, many power generation corporations or grid operators have begun using ESSs. An ESS has very quick response and good performance for reducing the impact of WP fluctuation; however, its installation cost is high. Therefore, it is important to design the control algorithm by considering both the ESS capacity and WP fluctuation. Thus, we propose a control algorithm to mitigate the WP fluctuation by using the coordinated control between the wind turbine and the ESS by considering the ESS capacity and the WP fluctuation. Using de-loaded control, according to the WP fluctuation and ESS capacity, we can expand the ESS lifespan and improve grid reliability by avoiding the extreme value of state of charge (SoC) (i.e., 0 or 1 pu). The effectiveness of the proposed method was validated via MATLAB/Simulink by considering a small power system that includes both a wind turbine generator and conventional generators that react to system frequency deviation. We found that the proposed method has better performance in SoC management, thereby improving the frequency regulation by mitigating the impact of the WP fluctuation on the small power system.
In this work, we present a proof of concept of a physics-based digital twin for a monopile structure (with overhead inertia) subjected to wave loading. The digital twin is formulated using reduced-order models derived from first principles and combined with a Kalman filter for state estimation. The proposed framework estimates the monopile top motion, the wave elevation, and the section forces and moments along the pile using primarily acceleration measurements at the monopile top. Key innovations include the use of a hydrodynamic shape function to represent distributed wave loading in a compact and computationally efficient manner, and the introduction of a shaping filter to augment the state-space with wave kinematics. Synthetic measurement data are generated using OpenFAST and used as a reference to assess the performance of the digital twin. Results demonstrate that the wave elevation can be accurately reconstructed without direct sea-state measurements as long as the wave regime is inertia-dominated. Under the ideal tested conditions, the total hydrodynamic force and sea-bed bending moment are estimated with relative errors on the order of 1% and correlation coefficients exceeding 96%. Future work will evaluate the estimator's performance under operational uncertainties and more complex loading conditions.
The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn, in the nearby galaxy, NGC 5806 (22.5 Mpc). Our spectral sequence in the optical and infrared suggests a Type Ib classification. We identify a blue progenitor candidate in deep pre-explosion imaging within a 2σ error circle of 80 mas (8.7 pc). The candidate has an M{sub B} luminosity of –5.52 ± 0.39 mag and a B – I color of 0.25 ± 0.25 mag. If confirmed by future observations, this would be the first direct detection for a progenitor of a Type Ib. Fitting a power law to the early light curve, we find an extrapolated explosion date around 0.6 days before our first detection. We see no evidence of shock cooling. The pre-explosion detection limits constrain the radius of the progenitor to be smaller than a few solar radii. iPTF13bvn is also detected in centimeter and millimeter wavelengths. Fitting a synchrotron self-absorption model to our radio data, we find a mass-loading parameter of 1.3×10{sup 12} g cm{sup –1}. Assuming a wind velocity of 10{sup 3} km s{sup –1}, we derive a progenitor mass-loss rate of 3 × 10{sup –5} M {sub ☉} yr{sup –1}. Our observations, taken as a whole, are consistent with a Wolf-Rayet progenitor of the supernova iPTF13bvn.
The emergence of carbon nanotube-copper composite conductors has opened a new degree of freedom in the electric machine design to improve the machine's performance: the conductivity of the winding. The goal of the present study is: 1) to determine how much improvement in power per unit volume and performance can be achieved with the increase in winding conductivity; and 2) to investigate any physical limitations on the effectiveness of this degree of freedom in improving the power per unit volume and performance of electric traction motors. Conventional electric motor topologies affected by ferromagnetic saturation as well as slotless topology that is not affected by saturation are analyzed. It was found that the ferromagnetic saturation of the lamination materials reduces the effectiveness of highly conductive winding in improving the power per unit volume. For machine topologies that are not affected by ferromagnetic saturation, the power density improvement reaches the theoretical expectation. In both cases, highly conductive winding improves the efficiency map by enlarging high efficiency operating area into light load as well as high speed operations.
Hall B at Jefferson Laboratory (JLAB) will need a 5 T, 78 cm bore polarized target magnet with a field uniformity of {Delta}B/B{sub 0} <; 10{sup -4} in a useful cylinder of the dimensions 0.04 m long x 0.02 m in diameter. The large magnet is designed with a superconducting coil that provides the solenoid with nearly perfect self shielding in order to reduce the fringe field at nearby photo multiplier tubes (PMTs) to less than 3.5 mT. Because the solenoid is also very close to the Clas12 Torus, the nearly perfect shielding provided by the self shielded solenoid greatly reduces force, field, and torque interactions with the six-coil Torus magnet. The solenoid coil consists of 18 coil modules which are made of coils mounted in aluminum plate discs. Each coil module consists of dual double pancake coils with main coils and shield coil partitioned into separate winding cavities in the aluminum plate discs to distribute and reduce radial hoop load and radial coil forces. Each coil module is effectively an enclosed aluminum box and this serves to partition the axial load and thus reduces coil axial forces. Since overall coil forces within each coil module are reduced, this will greatly reduce the number coil training quenches. This is a very important consideration for this solenoid coil because the coil cooling is adiabatic, using in-direct conduction cooling by 4.5 K supercritical helium, which will provide only a relatively small temperature stability margin. Super critical helium is used as per JLAB specification. Detail design of the coil structure, coil assembly, cold mass, and cryogenic control will be presented. The magnet protection system shall be capable of the following features: (1) quench and fault detection, (2) fast discharge of the magnet, (3) limit fault voltages to safe values, (4) monitor interlock signals to prevent unsafe operation, and (5) provide control logic necessary for safe operation of the solenoid. The instrument systems shall be capable of the following features: (1) monitors and display temperatures within the solenoid magnet, (2) measure loads or stress on the magnet suspension, (3) monitor voltages within the solenoid magnet and charging bus, (4) monitor pressures and (5) use data logging system to save all sensor data. These systems will be described and a quench analysis presented.
Circuit including feedback control elements automatically corrects the power factor of a reactive load. It maintains power supply efficiency where negative load reactance changes and varies by providing corrective error signals to the control windings of a power supply transformer.
The primary focus of this paper is to describe the challenges involved in creating this highly modified aircraft that carries a twenty ton telescope to the Stratosphere and then loiters at this desired altitude to act as the observatory "dome" or platform. When the aircraft has reached its nominal cruise condition in the stratosphere of Mach 0.84, a large cavity door opens (the dome opens), exposing a large portion of the interior of the fuselage containing the telescope optics, directly to the Universe. The breadth of topics covered in this paper includes; the relevant criteria and the evaluation process that resulted in the selection of a Boeing 747-SP, the evolution of the design concept, a description of the structural modification including the analysis methods and tools, the aerodynamic issues associated with an open port cavity and how they were addressed, the aero-loads/disturbances imparted to the telescope and how they were measured in the wind tunnel and extrapolated to full size. For completeness, this paper also provides a brief overview of the SOFIA project including the joint project arrangement between NASA and DLR, a top level overview of the science objectives and the resulting requirements, and finally the current project status.
Viscous Laminar-turbulent transition plays an important role in the design of the Mars Science Laboratory (MSL) entry vehicle. The lift-to-drag ratio required for the precision landing trajectory will be achieved via an angle of attack equal to 16 degrees. At this relatively high angle of attack, the boundary layer flow near the leeward meridian is expected to transition early in the trajectory, resulting in substantially increased heating loads. This paper presents stability calculations and transition correlations for a series of wind tunnel models of the MSL vehicle. Experimentally measured transition onset locations are used to correlate with the N-factor calculations for various wind tunnel conditions. Due to relatively low post-shock Mach numbers near the edge of the boundary layer, the dominant instability waves are found to be of the first mode type. The N-factor values correlating with measured transition onset at selected test points from the Mach 6 conventional facility experiments fall between 3.5 and 4.5 and apparently vary linearly with the wind tunnel unit Reynolds number, indicating strong receptivity effect. The small transition N value is consistent with previous correlations for second-mode dominant transition in the same wind tunnel facility. Stability calculations for stationary and traveling crossflow instability waves in selected configurations indicate that an N value of 4 and 6, respectively, correlates reasonably well with transition onset discerned from one experimentally measured thermographic image.
The 10- by 10-Foot Abe Silverstein Supersonic Wind Tunnel (10×10) is the largest and fastest wind tunnel facility at NASA’s Glenn Research Center(GRC) and is specifically designed to test supersonic propulsion components from inlets and nozzles to full-scale jet and rocket engines[1]. Recently, a critical part of the wind tunnel failed and required a redesign before reintegrating into the facility. The design requirements of this new component required that clearances between large metallic components exist, which have the potential for undesirable nonlinear dynamics to occur, in particular rattling. Rattling is feared to occur when the wind tunnel is being operated in certain flow regimes that induce cyclic aero loads on the new component near its natural frequencies. This paper describes the approach taken to better understand and resolve this vibration problem using modal testing. A modal test was developed and executed by GRC’s Structural Dynamics Lab to quantify the modal parameters of the structure, namely which specific excitation frequencies caused the structure to rattle. These results were shared with facility operators as frequency ranges that should be avoided to ensure maximum lifespan of the new structure. Additional means of structural health monitoring (SHM) as well as Vortex shedding are briefly discussed in this paper.
There is general concern in the power system industry regarding the degradation of frequency response due to various factors, such as the withdrawal of primary or governor response shortly after an event, the lack of in-service governors on conventional generation, and the unknown and changing nature of load frequency characteristics. Large penetrations of nonsynchronous or inverter-based generation (e.g., wind and solar photovoltaic) further contribute to the concerns. This paper reports on frequency stability research designed to explore the impact of high penetrations of inverter-based generation on the frequency response of a large interconnected grid as well as the potential contribution of those nonsynchronous resources to maintaining frequency stability.
MiGRIDS is a software that models islanded microgrid power systems with different controls and components. For example, using load and resource data from a microgrid, you could model it with additional wind turbines, battery etc. You could also try out different dispatch schemes to see which one worked best. MiGRIDS is designed to help optimize the size and dispatch of grid components in a microgrid. While a grid connect feature is expected to be added in the future, islanded operation is the focus. Note that this is a basic implementation and more features and functionality (such as a GUI) are coming! MiGRIDS runs time-step energy balance simulations for different grid components and controls. In smaller microgrid environments, dispatch decisions are being made on the order of seconds. In order to fully capture their effect, this tool lets you run simulations on the order of seconds. The end result is a more realistic representation of what can be achieved by integrating different components and control strategies in a grid.
The Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS) project is executing a program to qualify a parachute system for a next generation human spacecraft. Part of the qualification process involves predicting parachute riser tension during system descent with flight simulations. Human rating the CPAS hardware requires a high degree of confidence in the simulation models used to predict parachute loads. However, uncertainty exists in the heritage added mass models used for loads predictions due to a lack of supporting documentation and data. Even though CPAS anchors flight simulation loads predictions to flight tests, extrapolation of these models outside the test regime carries the risk of producing non-bounding loads. A set of equations based on empirically derived functions of skirt radius is recommended as the simplest and most viable method to test and derive an enhanced added mass model for an inflating parachute. This will increase confidence in the capability to predict parachute loads. The selected equations are based on those published in A Simplified Dynamic Model of Parachute Inflation by Dean Wolf. An Ames 80x120 wind tunnel test campaign is recommended to acquire the reefing line tension and canopy photogrammetric data needed to quantify the terms in the Wolf equations and reduce uncertainties in parachute loads predictions. Once the campaign is completed, the Wolf equations can be used to predict loads in a typical CPAS Drogue Flight test. Comprehensive descriptions of added mass test techniques from the Apollo Era to the current CPAS project are included for reference.