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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.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Status of the US Space Station ECLSS and internal TCS

The U.S. Space Station includes many elements and systems. Responsibility for these have been delegated to four NASA centers via a work packaging concept. Marshall Space Flight Center (MSFC) is responsible for work package one (WPOI) which includes the habitation, laboratory modules, the logistic carrier elements, as well as the environmental control and life support system (ECLSS), the internal thermal control system (ITCS), and the internal audio and video systems. Current status of the ECLSS and internal thermal are the subjects of this paper. The ECLSS is composed of six subsystem groups: the temperature humidity control, the atmosphere control and supply, the air revitalization, water reclamation and management, fecal waste management, and the fire detection and suppression subsystems. The internal TCS consists of all WP01 elements of passive and active thermal measures. The ECLSS and ITCS provide services for the permanently orbiting pressurized modules as well as the pressurized and unpressurized logistics carriers. The logistics carriers are used as ground-to-station ferries for both resupply and initial delivery of selected new equipment and later replacement items. Equipment, which cannot be subjected to the rigors of the space environment, will be carried in the pressurized logistic carrier; while an unpressurized carrier is used to resupply other commodities, such as external fluid consumables. The laboratory module houses the equipment for both payloads and subsystem maintenance and repair. The habitation module is dedicated to providing living and sleeping quarters including a galley, sleeping provisions, hygiene facilities, medical services as well as services for exercise and relaxation. The four nodes that join the two modules at their ends also house electronics as well as work stations and outside viewing cupolas. The airlocks, one providing an emergency hyperbaric chamber capability, are also attached. This assembly constitutes the U.S. provided portion of the initial station. Additional international modules and docking provisions for future attached pressurized payload as well as dual logistic module and growth capabilities are also provided. The primary heat rejection mechanism is achieved via a central set of radiators provided by another work package. The interface with the central TCS at the module heat exchangers defines the active control interface boundary of the ITCS with the central TCS. All internal cooling of the permanent orbital elements are provided via internal active fluid loops within the elements utilizing water as the transport media. Cabin and equipment cooling are provided by forced air flow and cold plate heat sinks. A special active cooling loop is provided in the laboratory module to accommodate experiments and other payloads. Coatings and insulation are used in conjunction with the active components to passively limit heat losses/gains. The most challenging ECLSS new technology issues relate to oxygen and water recovery. Closure of the oxygen loop requires the use of new regenerative CO 2 removal and concentration techniques, CO 2 reduction to convert the CO 2 to water with a waste by-product, and the electrolysis of water to produce breathing oxygen for water recovery. For water recovery three separate loops are currently planned. One loop provides potable water by utilizing a combination of recovered condensate and CO 2 reduction water. A second loop purifies hygiene water from waste from the showers, clothes washer, hygiene/hand wash stations and a dishwasher. The third loop provides hygiene water by the reclamation and purification of urine water. This paper outlines the basic services provided by the ECLSS and ITCS and describes the ECLSS functional distribution throughout the pressurized assembly.

R. Humphries↗
NASA NTRS1999

Entry Trajectory Issues for the Stardust Sample Return Capsule

The Stardust mission was successfully launched on February 7, 1999. It will be the first mission to return samples from a comet. The sample return capsule, which is passively controlled during the fastest Earth entry ever, will land by parachute in Utah. The present study describes the analysis of the entry, descent, and landing of the returning sample capsule utilizing the final, launch configuration capsule mass properties. The effects of two aerodynamic instabilities are revealed (one in the high altitude free molecular regime and the other in the transonic/subsonic flow regime). These instabilities could lead to unacceptably large excursions in the angle-of-attack near peak heating and main parachute deployment, respectively. To reduce the excursions resulting from the high altitude instability, the entry spin rate of the capsule is increased. To stabilize the excursions from the transonic/subsonic instability, a drogue chute with deployment triggered by a gravity-switch and timer is added prior to main parachute deployment. A Monte Carlo dispersion analysis of the modified entry (from which the impact of off-nominal conditions during the entry is ascertained) predicts that the capsule attitude excursions near peak heating and drogue chute deployment are within Stardust mission limits. Additionally, the size of the resulting 3-sigma landing ellipse is 60.8 km in downrange by 19.9 km in crossrange, which is within the Utah Test and Training Range boundaries.

Desai, Prasun N.↗
NASA NTRS1999

Entry Trajectory Issues for the Stardust Sample Return Capsule

The Stardust mission was successfully launched on February 7, 1999. It will be the first mission to return samples from a comet. The sample return capsule, which is passively controlled during the fastest Earth entry ever, will land by parachute in Utah. The present study describes the analysis of the entry, descent, and landing of the returning sample capsule utilizing the final, launch configuration capsule mass properties. The effects of two aerodynamic instabilities are revealed (one in the high altitude free molecular regime and the other in the transonic/subsonic flow regime). These instabilities could lead to unacceptably large excursions in the angle-of-attack near peak heating and main parachute deployment, respectively. To reduce the excursions resulting from the high altitude instability, the entry spin rate of the capsule is increased. To stabilize the excursions from the transonic/subsonic instability, a drogue chute with deployment triggered by a gravity-switch and timer is added prior to main parachute deployment. A Monte Carlo dispersion analysis of the modified entry (from which the impact of off-nominal conditions during the entry is ascertained) predicts that the capsule attitude excursions near peak heating and drogue chute deployment are within Stardust mission limits. Additionally, the size of the resulting 3-sigma landing ellipse is 60.8 km in downrange by 19.9 km in crossrange, which is within the Utah Test and Training Range boundaries.

Desai, Prasun N.↗
NASA NTRS1999

Constrained Vapor Bubble

The nonisothermal Constrained Vapor Bubble, CVB, is being studied to enhance the understanding of passive systems controlled by interfacial phenomena. The study is multifaceted: 1) it is a basic scientific study in interfacial phenomena, fluid physics and thermodynamics; 2) it is a basic study in thermal transport; and 3) it is a study of a heat exchanger. The research is synergistic in that CVB research requires a microgravity environment and the space program needs thermal control systems like the CVB. Ground based studies are being done as a precursor to flight experiment. The results demonstrate that experimental techniques for the direct measurement of the fundamental operating parameters (temperature, pressure, and interfacial curvature fields) have been developed. Fluid flow and change-of-phase heat transfer are a function of the temperature field and the vapor bubble shape, which can be measured using an Image Analyzing Interferometer. The CVB for a microgravity environment, has various thin film regions that are of both basic and applied interest. Generically, a CVB is formed by underfilling an evacuated enclosure with a liquid. Classification depends on shape and Bond number. The specific CVB discussed herein was formed in a fused silica cell with inside dimensions of 3x3x40 mm and, therefore, can be viewed as a large version of a micro heat pipe. Since the dimensions are relatively large for a passive system, most of the liquid flow occurs under a small capillary pressure difference. Therefore, we can classify the discussed system as a low capillary pressure system. The studies discussed herein were done in a 1-g environment (Bond Number = 3.6) to obtain experience to design a microgravity experiment for a future NASA flight where low capillary pressure systems should prove more useful. The flight experiment is tentatively scheduled for the year 2000. The SCR was passed on September 16, 1997. The RDR is tentatively scheduled for October, 1998.

Huang, J.↗
NASA NTRS1999

Advanced Aerodynamic Control Effectors

A 1990 research program that focused on the development of advanced aerodynamic control effectors (AACE) for military aircraft has been reviewed and summarized. Data are presented for advanced planform, flow control, and surface contouring technologies. The data show significant increases in lift, reductions in drag, and increased control power, compared to typical aerodynamic designs. The results presented also highlighted the importance of planform selection in the design of a control effector suite. Planform data showed that dramatic increases in lift (greater than 25%) can be achieved with multiple wings and a sawtooth forebody. Passive porosity and micro drag generator control effector data showed control power levels exceeding that available from typical effectors (moving surfaces). Application of an advanced planform to a tailless concept showed benefits of similar magnitude as those observed in the generic studies.

Wood, Richard M.↗
NASA NTRS1999

Advanced Aerodynamic Control Effectors

A 1990 research program that focused on the development of advanced aerodynamic control effectors (AACE) for military aircraft has been reviewed and summarized. Data are presented for advanced planform, flow control, and surface contouring technologies. The data show significant increases in lift, reductions in drag, and increased control power, compared to typical aerodynamic designs. The results presented also highlighted the importance of planform selection in the design of a control effector suite. Planform data showed that dramatic increases in lift (greater than 25%) can be achieved with multiple wings and a sawtooth forebody. Passive porosity and micro drag generator control effector data showed control power levels exceeding that available from typical effectors (moving surfaces). Application of an advanced planform to a tailless concept showed benefits of similar magnitude as those observed in the generic studies.

Wood, Richard M.↗
NASA NTRS2009

Design Analysis of the Ares 1 Pogo Accumulator

Several accumulator designs and gas charge systems are considered in order to suppress POGO within the Ares I vehicle Upper Stage Liquid Ox ygen System. The thermodynamic and flow analysis completed to evaluat e candidate designs are presented and the results are used to evaluat e the ability of each concept to meet the levied suppression requirements. One annular accumulator design meets all suppression requirement s while also providing manufacturability and operability advantages. Of the two proposed charge systems to provide and maintain gas within the accumulator, a passive level control design meets the charge req uirements and maximizes reliability.

Swanson, Luke A.↗
NASA NTRS2011

Evaluation of a Passive Heat Exchanger Based Cooling System for Fuel Cell Applications

Fuel cell cooling is conventionally performed with an actively controlled, dedicated coolant loop that exchanges heat with a separate external cooling loop. To simplify this system the concept of directly cooling a fuel cell utilizing a coolant loop with a regenerative heat exchanger to preheat the coolant entering the fuel cell with the coolant exiting the fuel cell was analyzed. The preheating is necessary to minimize the temperature difference across the fuel cell stack. This type of coolant system would minimize the controls needed on the coolant loop and provide a mostly passive means of cooling the fuel cell. The results indicate that an operating temperature of near or greater than 70 C is achievable with a heat exchanger effectiveness of around 90 percent. Of the heat exchanger types evaluated with the same type of fluid on the hot and cold side, a counter flow type heat exchanger would be required which has the possibility of achieving the required effectiveness. The number of heat transfer units required by the heat exchanger would be around 9 or greater. Although the analysis indicates the concept is feasible, the heat exchanger design would need to be developed and optimized for a specific fuel cell operation in order to achieve the high effectiveness value required.

Colozza, Anthony J.↗
NASA NTRS1999

Effects of Passive Fuel-Air Mixing Control on Burner Emissions Via Lobed Fuel Injectors

The present experimental study examines the effects of differing levels of passive fuel-air premixing on flame structures and their associated NO(x) and CO emissions. Four alternative fuel injector geometries were explored, three of which have lobed shapes. These lobed injectors mix fuel and air and strain species inter-faces to differing extents due to streamwise vorticity generation, thus creating different local or core equivalence ratios within flow regions upstream of flame ignition and stabilization. Prior experimental studies of two of these lobed injector flowfields focused on non-reactive mixing characteristics and emissions measurements for the case where air speeds were matched above and below the fuel injector, effectively generating stronger streamwise vorticity than spanwise vorticity. The present studies examine the effects of airstream mismatch (and hence additional spanwise vorticity generation), effects of confinement of the crossflow to reduce the local equivalence ratio, and the effects of altering the geometry and position of the flameholders. NO(x) and CO emissions as well as planar laser-induced fluorescence imaging (PLIF) of seeded acetone are used to characterize injector performance and reactive flow evolution.

Mitchell, M. G.↗
NASA NTRS2009

Simplified Ion Thruster Xenon Feed System for NASA Science Missions

The successful implementation of ion thruster technology on the Deep Space 1 technology demonstration mission paved the way for its first use on the Dawn science mission, which launched in September 2007. Both Deep Space 1 and Dawn used a "bang-bang" xenon feed system which has proven to be highly successful. This type of feed system, however, is complex with many parts and requires a significant amount of engineering work for architecture changes. A simplified feed system, with fewer parts and less engineering work for architecture changes, is desirable to reduce the feed system cost to future missions. An attractive new path for ion thruster feed systems is based on new components developed by industry in support of commercial applications of electric propulsion systems. For example, since the launch of Deep Space 1 tens of mechanical xenon pressure regulators have successfully flown on commercial spacecraft using electric propulsion. In addition, active proportional flow controllers have flown on the Hall-thruster-equipped Tacsat-2, are flying on the ion thruster GOCE mission, and will fly next year on the Advanced EHF spacecraft. This present paper briefly reviews the Dawn xenon feed system and those implemented on other xenon electric propulsion flight missions. A simplified feed system architecture is presented that is based on assembling flight-qualified components in a manner that will reduce non-recurring engineering associated with propulsion system architecture changes, and is compared to the NASA Dawn standard. The simplified feed system includes, compared to Dawn, passive high-pressure regulation, a reduced part count, reduced complexity due to cross-strapping, and reduced non-recurring engineering work required for feed system changes. A demonstration feed system was assembled using flight-like components and used to operate a laboratory NSTAR-class ion engine. Feed system components integrated into a single-string architecture successfully operated the engine over the entire NSTAR throttle range over a series of tests. Flow rates were very stable with variations of at most 0.2%, and transition times between throttle levels were typically 90 seconds or less with a maximum of 200 seconds, both significant improvements over the Dawn bang-bang feed system.

Snyder, John Steven↗
NASA NTRS1999

Solar Thermal Upper Stage Cryogen System Engineering Checkout Test

The Solar Thermal Upper Stage technology (STUSTD) program is a solar thermal propulsion technology program cooperatively sponsored by a Boeing led team and by NASA MSFC. A key element of its technology program is development of a liquid hydrogen (LH2) storage and supply system which employs multi-layer insulation, liquid acquisition devices, active and passive thermodynamic vent systems, and variable 40W tank heaters to reliably provide near constant pressure H2 to a solar thermal engine in the low-gravity of space operation. The LH2 storage and supply system is designed to operate as a passive, pressure fed supply system at a constant pressure of about 45 psia. During operation of the solar thermal engine over a small portion of the orbit the LH2 storage and supply system propulsively vents through the enjoy at a controlled flowrate. During the long coast portion of the orbit, the LH2 tank is locked up (unvented). Thus, all of the vented H2 flow is used in the engine for thrust and none is wastefully vented overboard. The key to managing the tank pressure and therefore the H2 flow to the engine is to manage and balance the energy flow into the LH2 tank with the MLI and tank heaters with the energy flow out of the LH2 tank through the vented H2 flow. A moderate scale (71 cu ft) LH2 storage and supply system was installed and insulated at the NASA MSFC Test Area 300. The operation of the system is described in this paper. The test program for the LH2 system consisted of two parts: 1) a series of engineering tests to characterize the performance of the various components in the system: and 2) a 30-day simulation of a complete LEO and GEO transfer mission. This paper describes the results of the engineering tests, and correlates these results with analytical models used to design future advanced Solar Orbit Transfer Vehicles.

Olsen, A. D↗
NASA NTRSDate not supplied

AERACEPT (AErosol Rapid Analysis Combined Entry Probe/sonde Technology) for the Nephele Venus Cloud Mission Concept

Nephele is a small atmospheric probe mission concept to determine whether the Venus clouds contain organic matter. Nephele complements larger missions that seek to conduct Venus atmospheric analyses, such as DAVINCI, Venera-D, and the Morning Star missions, by directly sampling and analyzing cloud and haze particles. AERACEPT is an aerosol sampling technology designed to minimize the mass, volume, and complexity required for in situ planetary atmosphere characterization. A single aeroshell functions as a combined entry vehicle, descent probe, and instrumented sonde, combining recent advances in thermal protection materials with heritage technology from planetary and airborne science. The velocity of descent drives aerosol through inlets embedded in the aeroshell’s thermal protection material; inertial separation isolates the particles from the gas stream; and the particle capture surface doubles as the analysis substrate. This method can work without heat shield separation, descent control, or active sample handling; these advantages trade against a smaller sample volume, higher risk of sample heating, and shorter time for analysis and data return. AERACEPT further benefits from modeling of the internal and external flow to understand the particle capture efficiency and bias for size and concentration distributions. AERACEPT is well suited for a Venus mission such as Nephele, where a passive descent trajectory is both subsonic over the altitudes of interest and provides sufficient velocity and pressure differential for the particle sizes of interest. A thermal and flow toolchain developed in-house (Traj→ DPLR→ PATO→ openFOAM) was used to model an 80-cm aeroshell with science operations 63–39 km. These models indicate that AERACEPT will provide ~24 µL accumulated sample of particles ≥ 0.2 µm, substantially above the 2 µL threshold requirement. The worst-case particle heating will be ~14 K above ambient, for the smallest particles at the lowest altitude; most particles will experience ≤ 1 K rise, at which almost all analytes of interest will be unaffected. Plasma jet testing of a small-scale aeroshell-material inlet was recently conducted to validate the thermal model parameters; wind tunnel testing to validate the flow model parameters is underway.

AERACEPT↗
NASA NTRS2007

Turbomachinery Clearance Control

Controlling interface clearances is the most cost effective method of enhancing turbomachinery performance. Seals control turbomachinery leakages, coolant flows and contribute to overall system rotordynamic stability. In many instances, sealing interfaces and coatings are sacrificial, like lubricants, giving up their integrity for the benefit of the component. They are subjected to abrasion, erosion, oxidation, incursive rubs, foreign object damage (FOD) and deposits as well as extremes in thermal, mechanical, aerodynamic and impact loadings. Tribological pairing of materials control how well and how long these interfaces will be effective in controlling flow. A variety of seal types and materials are required to satisfy turbomachinery sealing demands. These seals must be properly designed to maintain the interface clearances. In some cases, this will mean machining adjacent surfaces, yet in many other applications, coatings are employed for optimum performance. Many seals are coating composites fabricated on superstructures or substrates that are coated with sacrificial materials which can be refurbished either in situ or by removal, stripping, recoating and replacing until substrate life is exceeded. For blade and knife tip sealing an important class of materials known as abradables permit blade or knife rubbing without significant damage or wear to the rotating element while maintaining an effective sealing interface. Most such tip interfaces are passive, yet some, as for the high-pressure turbine (HPT) case or shroud, are actively controlled. This work presents an overview of turbomachinery sealing. Areas covered include: characteristics of gas and steam turbine sealing applications and environments, benefits of sealing, types of standard static and dynamics seals, advanced seal designs, as well as life and limitations issues.

Chupp, Raymond E.↗
DOE OSTI2022

Refueling water storage tank (RWST) with tailored passive emergency core cooling (ECC) flow

A nuclear reactor comprises a pressure vessel containing a nuclear reactor core. A reactor core cooling system comprises a standpipe including a plurality of orifices in fluid communication with a refueling water storage tank (RWST) to drain water from the RWST into the standpipe, and an injection line configured to drain water from the standpipe to the pressure vessel. In some embodiments the standpipe is disposed in the RWST, while in other embodiments the standpipe is disposed outside of the RWST and cross-connection pipes connect the plurality of orifices with the RWST. The reactor core cooling system may further comprise a valve configured to control flow through one orifice of the plurality of orifices in fluid communication with the RWST based on water level in the standpipe. The valve may comprise a float valve having its float disposed in the standpipe.

Watson, Ronald C.↗
DOE OSTI2024

Interactions between phosphate and arsenic in iron/biochar-treated groundwater: Corrosion control insights from column experiments

An increasing number of studies have reported the coexistence of arsenic (As) and phosphorus at high concentrations in groundwater, which threatens human health and increases the complexity of groundwater remediation. However, limited work has been done regarding As interception in the presence of phosphate in flowing systems. In this study, a series of experiments were conducted to evaluate the interactions between phosphate and As during As removal by iron (Fe)-based biochar (FeBC). The addition of phosphate promoted As removal by FeBC in the batch and column experiments. X-ray absorption near edge structure (XANES) analysis provided evidence of simultaneous oxidation and reduction of trivalent arsenic in the FeBC column experiment, accompanied by corrosive Fe oxidation. However, the addition of phosphate enhanced As stabilization, attributed to the As-incorporated Fe-Ca-phosphates precipitates. The involvement of phosphate decelerated the Fe corrosion and the formation of secondary minerals in the column, mediating the risk of passivation and clogging. The As retained by Fe-Ca-phosphate precipitates was more readily oxidized, resulting in higher proportions of pentavalent arsenic. In conclusion, the results of this work identify the corrosion control and sustained-release roles of phosphate in FeBC application, informing the perspective of FeBC in As-contaminated groundwater remediation and providing new insights into the interactions between phosphate and As.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2017

Sample Processor for Life on Icy Worlds (SPLIce): Design and Test Results

We report the design, development, and testing of the Sample Processor for Life on Icy Worlds (SPLIce) system, a microfluidic sample processor to enable autonomous detection of signatures of life and measurements of habitability parameters in Ocean Worlds. This monolithic fluid processing-and-handling system (Figure 1; mass 0.5 kg) retrieves a 50-L-volume sample and prepares it to supply a suite of detection instruments, each with unique preparation needs. SPLIce has potential applications in orbiter missions that sample ocean plumes, such as found in Saturns icy moon Enceladus, or landed missions on the surface of icy satellites, such as Jupiters moon Europa. Answering the question Are we alone in the universe? is captivating and exceptionally challenging. Even general criteria that define life very broadly include a significant role for water [1,2]. Searches for extinct or extant life therefore prioritize locations of abundant water whether in ancient (Mars), or present (Europa and Enceladus) times. Only two previous planetary missions had onboard fluid processing: the Viking Biology Experiments [3] and Phoenixs Wet Chemistry Laboratory (WCL) [4]. SPLIce differs crucially from those systems, including its capability to process and distribute L-volume samples and the integration autonomous control of a wide range of fluidic functions, including: 1) retrieval of fluid samples from an evacuated sample chamber; 2) onboard multi-year storage of dehydrated reagents; 3) integrated pressure, pH, and conductivity measurement; 4) filtration and retention of insoluble particles for microscopy; 5) dilution or vacuum-driven concentration of samples to accommodate instrument working ranges; 6) removal of gas bubbles from sample aliquots; 7) unidirectional flow (check valves); 8) active flow-path selection (solenoid-actuated valves); 9) metered pumping in 100 nL volume increments. The SPLIce manifold, made of three thermally fused layers of precision-machined cyclo-olefin polymer, supports all fluidic components (Figure 1) and integrated microchannels (125 x 250 m). Fluid is pumped by a stepper-motor-driven pump (Lee Co.). The functionality of the integrated MEMS pressure sensor (Honeywell) and passive check valves (Figure 2) were tested in conjunction with our newly designed integral bubble traps (Figure 3) and hydrophobic membrane-based concentrator (Figure 4). The concentrator (initially tested as a standalone component) demonstrated 5-fold vacuum-evaporative concentration. Polyethylene fused bead beds (PEFBBs; 50 porosity) store drylyophilized buffers, calibrants, and fluorescent dyes, and also promote mixing of sample with calibrant, dye, or H2O. Software-controlled automated tests demonstrated successful 1) fluid delivery to each component 2) valve and pump synchronization 3) sample aliquot delivery to instrument interface ports, and 4) rehydration of vacuum-dried fluorescent dye. In Figure 5, fluorescein on PEFBBs was rehydrated for 15 min using a pump-delivered water aliquot; it is displaced as H2O enters the bottom of the channel and pushes the dye into a check valve. Ultimately, SPLIce will fluorescently label amino acids in the sample for microchip-based electrophoretic (MCE) chiral separation and detection to seek and quantify key organic bio-signatures [5]; it will also deliver sample to a microfluidic version of WCL (mWCL) to measure soluble ions and redox-active species.

Life detection↗
DOE OSTI2020

Hydrokinetic Power Conversion Using Vortex-Induced Oscillation with Cubic Restoring Force

A cubic-spring restoring function with high-deformation stiffening is introduced to passively improve the harnessed marine hydrokinetic power by using flow-induced oscillations/vibrations (FIO/V) of a cylinder. In these FIO/V experiments, a smooth, rigid, single-cylinder on elastic end-supports is tested at Reynolds numbers ranging from 24,000 < Re < 120,000. The parameters of the tested current energy converter (CEC) are cubic stiffness and linear damping. Using the second generation of digital virtual spring-damping (Vck) controller developed by the Marine Renewable Energy Laboratory (MRELab), the cubic modeling of the oscillator stiffness is tested. Experimental results show the influence of the parameter variation on the amplitude, frequency, energy conversion, energy efficiency, and power of the converter. All experiments are conducted in the low turbulence-free surface water (LTFSW) channel of the MRELab of the University of Michigan. The main conclusions are: (1) The nonlinearity in the cubic oscillator is an effective way to extend the vortex-induced vibration (VIV) upper branch, which results in higher harnessing power and efficiency compared to the linear stiffness cylinder converter. (2) Compared to the linear converter, the overall power increase is substantial. The nonlinear power optimum, occurring at the end of the VIV upper branch, is 63% higher than its linear counterpart. (3) The cubic stiffness converter with low harnessing damping achieves consistently good performance in all the VIV regions because of the hardening restoring force, especially at higher flow velocity.

13 HYDRO ENERGY↗
DOE OSTI2022

Rapid manufacturing of tailored preforms

A method for rapid manufacturing of three dimensional discontinuous fiber preforms is provided. The method includes the deposition of a polymeric material containing fibers on a surface to form a tailored charge for compression molding. The reinforced polymeric material may be a thermoplastic or a reactive polymer with viscosity low enough to allow flow through an orifice during deposition, yet high enough zero shear viscosity to retain the approximate shape of the deposited charge. The material can be deposited in a predetermined pattern to induce the desired mechanical properties through alignment of the fibers. This deposition can be performed in a single layer or in multiple layers. The alignment is achieved passively by shear alignment of the fibers or actively through fiber orientation control or mixing. The fibers can be of the desired material, length, and morphology, including short and long filaments.

Kunc, Vlastimil↗