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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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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Steady-State Solution of a Flexible Wing

A fluid-structure interaction code, ENSAERO, has been used to compute the aerodynamic loads on a swept-tapered wing. The code has the capability of using Euler or Navier-Stokes equations. Both options have been used and compared in the present paper. In the calculation of the steady-state solution, we are interested in knowing how the flexibility of the wing influences the lift coefficients. If the results of a flexible wing are not affected by the flexibility of the wing significantly, one could consider the wing to be rigid and reduce the problem from fluid-structure interaction to a fluid problem.

Karkehabadi, Reza↗
NASA NTRS1991

Steady-state phase error for a phase-locked loop subjected to periodic Doppler inputs

The performance of a carrier phase locked loop (PLL) driven by a periodic Doppler input is studied. By expanding the Doppler input into a Fourier series and applying the linearized PLL approximations, it is easy to show that, for periodic frequency disturbances, the resulting steady state phase error is also periodic. Compared to the method of expanding frequency excursion into a power series, the Fourier expansion method can be used to predict the maximum phase error excursion for a periodic Doppler input. For systems with a large Doppler rate fluctuation, such as an optical transponder aboard an Earth orbiting spacecraft, the method can be applied to test whether a lower order tracking loop can provide satisfactory tracking and thereby save the effect of a higher order loop design.

Chen, C.-C.↗
NASA NTRS1984

Dendritic solidification in a binary alloy melt: Steady-state versus morphological stability theories

A model for dendritic growth in a binary alloy melt, in the presence of a positive temperature gradient in the liquid, is presented. The model describes satisfactorily the transition from a dendritic interface to a planar interface at very low and very large growth rates. A dendrite tip stability parameter is derived, strictly from steady state considerations, without resorting to a perturbation analysis. The estimates of the parameter agree with those obtained by models based on perturbation analyses.

Laymanan, V.↗
DOE OSTI2020

Steady-state off-design modeling of the supercritical carbon dioxide recompression cycle for concentrating solar power applications with two-tank sensible-heat storage

Concentrating solar power researchers are evaluating the potential of the supercritical carbon dioxide recompression cycle to improve the thermal efficiency and decrease the capital costs of next-generation systems. This analysis investigates the steady-state off-design performance of a recompression cycle integrated with two-tank sensible-heat thermal energy storage as the ambient temperature and heat-transfer fluid (HTF) inlet conditions to the cycle change. This paper presents off-design component models and then cycle convergence and control models to maximize net cycle power output while constraining the high-side pressure and air-cooler fan power to their respective design values and fixing the cycle HTF outlet temperature to its design value. Results show that inventory control and air-cooler fan power are important control parameters that can be optimized to maximize off-design power output as the ambient temperature and HTF mass flow rate diverge from design. The high-side pressure and fan power constraints cause the cycle net power to degrade when the ambient temperature is warmer than the design value, and this study calculates a maximum mass flow rate for hot days above which the cycle cannot achieve the design HTF outlet temperature. Finally, the analysis shows that optimizing compressor shaft speeds can improve cold-day performance by around 1.5 percentage points and part-load performance by up to 2.5 percentage points versus a baseline case with no active compressor control.

14 SOLAR ENERGY↗
DOE OSTI2024

Optimization of District Heating Network Parameters in Steady-State Operation

Here we examine the modeling, simulation, and optimization of district heating systems, which are widely used for thermal transport using steam or hot water as a carrier. We propose a generalizable framework to specify network models and scenario parameters, and develop an optimization method for evaluating system states including pressures, fluid flowrates, and temperatures throughout the network. The network modeling includes pipes, thermal plants, pumps, and passive or controllable loads as system components. We propose basic models for thermodynamic fluid transport and enforce the balance of physical quantities in steady-state flow over co-located outgoing and return networks. We formulate an optimization problem with steam and hot water as the outgoing and return carriers, as in legacy twentieth century systems. The physical laws and engineering limitations are specified for each component type, and the thermal network flow optimization problem is formulated and solved for a realistic test network under several scenarios.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Evaluation of a quasi-steady-state approximation of the cloud droplet growth equation (QDGE) scheme for aerosol activation in global models using multiple aircraft data over both continental and marine environments

This research introduces a numerically efficient aerosol activation scheme and evaluates it by using stratus and stratocumulus cloud data sampled during multiple aircraft campaigns in Canada, Chile, Brazil, and China. The scheme employs a quasi-steady-state approximation of the cloud droplet growth equation (QDGE) to efficiently simulate aerosol activation, the vertical profile of supersaturation, and the activated cloud droplet number concentration (CDNC) near the cloud base. The calculated maximum supersaturation values using the QDGE scheme were compared with multiple parcel model simulations under various aerosol and environmental conditions. The differences are all below 0.18 %, indicating good performance and accuracy of the QDGE scheme. We evaluated the QDGE scheme by specifying observed environmental thermodynamic variables and aerosol information from 31 cloud cases as input and comparing the simulated CDNC with cloud observations. The average of mean relative error ($\overline{MRE}$) of the simulated CDNC for cloud cases in each campaign ranges from 17.30 % in Brazil to 25.90 % in China, indicating that the QDGE scheme successfully reproduces observed variations in CDNC over a wide range of different meteorological conditions and aerosol regimes. Additionally, we carried out an error analysis by calculating the maximum information coefficient (MIC) between the MRE and input variables for the individual campaigns and all cloud cases. MIC values were then sorted by aerosol properties, pollution level, environmental humidity, and dynamic condition according to their relative importance to MRE. Based on the error analysis, we found that the magnitude of MRE is more relevant to the specification of input aerosol pollution level in marine regions and aerosol hygroscopicity in continental regions than to other variables in the simulation.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1993

Non-steady-state transport of superthermal electrons in the plasmasphere

Numerical solutions to the time-dependent kinetic equation, which describes the transport of superthermal electrons in the splasmasphere between the two conjugate ionospheres, are presented. The model calculates the distribution function as a function of time, field-aligned distance, energy, and pitch-angle. The processes of refilling, depleting, and establishing steady-state conditions of superthermal electrons in the plasmasphere are discussed.

Khazanov, George V.↗
NASA NTRS1994

Electronically Controlled Mechanical Seal for Aerospace Applications -- Part 1: Design, Analysis, and Steady State Tests

An electronically-controlled mechanial seal, for use as the purge gas seal in a liquid oxygen turbopump, has been designed, analyzed, and built. The thickness of the lubricating film between the faces is controlled by adjusting the coning of the carbon face. This is done by applying a voltage across a piezoelectric element to which the carbon face is bound. Steady state tests have shown that the leakage rate (and film thickness) can be adjusted over a substantial range, utilizing the available range of voltage.

Salant, Richard F.↗
DOE OSTI2023

Capturing Time-Varying Wake Dynamics Using Hybridized Actuator Disks in Steady-State Simulations for Improved Optimization Efficiency

When optimizing turbine blade properties, using a time varying, unsteady simulation allows for high-fidelity representations of the wake dynamics. Unfortunately these types of optimizations are prohibitively expensive in terms of computation time and memory requirements. This presentation aims to show a method of transferring the wake dynamics of an unsteady simulation to a much more computationally tractable steady state simulation using hybrid actuator disks informed by unsteady, actuator line model dynamics.

actuator disk model↗
DOE OSTI2023

Simulation of a strong steady-state plasma shock in a warm dense matter regime

The structure of collisional plasma shocks has been subject to an extensive, multi-decadal investigation—in the hydrodynamic, hybrid kinetic ion/electron fluid, and fully kinetic ion/electron limits. Despite this thoroughness, all of these studies apply exclusively to classical, weakly coupled plasmas. Here, we report the first results for a planar hydrodynamic simulation of a strong, steady-state shock in a subspace of the warm dense matter (WDM) regime. Specifically, we consider a plasma of fully degenerate electrons with moderate-to-strongly coupled ions. Since the WDM ion and electron transport coefficients and equation of state differ markedly from their non-degenerate, weak-coupling equivalents, we find that the structure of a WDM plasma shock notably deviates from the ideal plasma picture.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1987

Steady state flow/field model of solar wind interaction with Venus - Global implications of local effects

Physical and chemical processes in the Venus ionosphere driven by the interaction of the solar wind with the atmosphere of Venus are described, and a model describing the interrelationships of these processes in a self-consistent manner is formulated. It is shown that the magnetic field configuration of the ionosphere is a steady state global structure which results from a combination of a large-scale 'open' current system connecting through the ionopause to the postshock solar wind and two small-scale 'closed' current systems entirely confined within the ionosphere and generated by ionospheric flows and shears. A previously detected ionospheric layer in O2(+) near 170 km altitude is shown to be a new type of ionospheric layer resulting from transition of solar-wind-driven vertical flow to velocities approaching Mach 1.

Cloutier, P. A.↗
DOE OSTI2021

Impact of Non-Steady State Operation on Cooling Water Consumption at Coal- and Natural Gas-Fired Power Plants

Increased renewable energy penetration in the electricity grid in coming decades will result in more frequent cycling at thermal power plants. Simultaneously, thermal power plants may face water scarcity with declining availability of cooling water. Therefore, to enhance thermal power plants’ resiliency to water shortages it is important to understand how non-steady conditions due to cycling will impact cooling water consumption and withdrawal intensity. Non-steady operation at power plants has been previously shown to decrease power plant thermal efficiency. Energy balance models have also demonstrated that a decrease in thermal efficiency is expected to increase cooling water consumption intensity. Furthermore, past work has used operating hours data to show idling and cycling gaps where cooling systems operate more than corresponding generators. As a result, an increase in cycling behavior may impact cooling water consumption and withdrawal intensity. This study uses data from the Energy Information Administration (EIA) and Environmental Protection Agency (EPA) to quantify the impact of cycling cooling water consumption intensity for recirculating cooling systems and withdrawal intensity for once-through cooling systems using energy balance and statistical approaches. In a novel application of a fixed effects model to study the effect of temperature on cooling water consumption and withdrawal intensity, this study finds temperature was consistently expected to increase consumption intensity and withdrawal intensity. Non-steady state conditions do not increase cooling water consumption intensity with statistical significance across unit types. However, additional validation of cooling water data is required to confirm these observed trends due to the sensitivity of these findings to model form and concerns with data quality of the dependent variables, cooling water consumption and withdrawal.

20 FOSSIL-FUELED POWER PLANTS↗
NASA NTRS1992

A two-dimensional MHD global coronal model - Steady-state streamers

A 2D, time-dependent, numerical, MHD model for the simulation of coronal streamers from the solar surface to 15 solar is presented. Three examples are given; for dipole, quadrupole and hexapole (Legendre polynomials P1, P2, and P3) initial field topologies. The computed properties are density, temperature, velocity, and magnetic field. The calculation is set up as an initial-boundary value problem wherein a relaxation in time produces the steady state solution. In addition to the properties of the solutions, their accuracy is discussed. Besides solutions for dipole, quadrupole, and hexapole geometries, the model use of realistic values for the density and Alfven speed while still meeting the requirement that the flow speed be super-Alfvenic at the outer boundary by extending the outer boundary to 15 solar radii.

Wang, A.-H.↗
DOE OSTI2021

Ion heating in the PISCES-RF liquid-cooled high-power, steady-state, helicon plasma device

Radio frequency (RF) driven helicon plasma sources are commonly used for their ability to produce high-density argon plasmas ( n > 10 19 m -3 ) at relatively moderate powers (typical RF power < 2 kW). Typical electron temperatures are <10 eV and typical ion temperatures are <0.6 eV. A newly designed helicon antenna assembly (with concentric, double-layered, fully liquid-cooled RF-transparent windows) operates in steady-state at RF powers up to 10 kW. We report on the dependence of argon plasma density, electron temperature and ion temperature on RF power. At 10 kW, ion temperatures >2 eV in argon plasmas are measured with laser induced fluorescence, which is consistent with a simple volume averaged 0D power balance model. 1D Monte Carlo simulations of the neutral density profile for these plasma conditions show strong neutral depletion near the core and predict neutral temperatures well above room temperatures. The plasmas created in this high-power helicon source (when light ions are employed) are ideally suited for fusion divertor plasma-material interaction studies and negative ion production for neutral beams.

Physics↗
DOE OSTI2021

A non‐intrusive domain‐decomposition model reduction method for linear steady‐state partial differential equations with random coefficients

Abstract Domain decomposition methods have been proved to be an effective strategy to reduce the dimension of parametric partial differential equations (PDEs). However, existing domain decomposition methods for parametric PDEs are usually intrusive, which means domain decomposition based solvers need to be implemented from scratch for each target parametric PDE. To address this issue, we develop a new non‐intrusive domain‐decomposition model reduction method for linear steady‐state PDEs with random‐field coefficients. As a variant of our previous work by Mu and Zhang, the new method only needs access to the final linear system, that is, the global stiffness matrix and the right hand side, of a deterministic PDE solver, in order to build a domain‐decomposition‐based reduced model without intrusive implementation from scratch. The key idea is to remove the interface condition between sub‐domains and rely on the correlation between columns of the linear system to couple the sub‐domains. The non‐intrusive feature enables the applicability of the proposed method to a broader class of uncertainty quantification problems, where many legacy codes/solvers can be fully reused by our method. Two numerical examples including diffusion equations with random diffusivity and convection‐dominated transport with random velocity, are provided to demonstrate the effectiveness and efficiency of our method.

Zhang, Guannan↗
NASA NTRS1986

An experimental investigation of the aerodynamics of a NACA 64A010 airfoil-flap combination with and without flap oscillations. Part 1: Steady-state characteristics

A NACA 64A010 airfoil with a sealed-gap 1/4-chord flap was tested between splitter plates in the NASA Ames 11- by 11-Foot Transonic Wind Tunnel at Mach numbers from 0.50 to 0.85, and Reynolds numbers based on chord from 3 to 13 million. Although the main purpose of the test was to obtain unsteady pressure data with the flap oscillating, no unsteady data are presented in this paper. The steady-state data are presented and compared with other test data to provide a basis for evaluating the results. Pressure data at two span stations are used to deduce early boundary-layer transitions at the midspan at higher Mach numbers, angles of attack, and flap angles. The effects of flap angle on pressures, normal force, pitching moment, and hinge moment are also presented in the report. Mach number errors caused by the splitter-plate configuration and the angle of attack are evaluated using pressure measurements near the floor and ceiling of the wind tunnel.

Buell, Donald A.↗
NASA NTRS1972

A study of the steady state spray equation.

A constant cross-sectional area rocket motor was used to study the combustion of a spray of ethanol in gaseous oxygen. The variables of the combustion gas and the flux of liquid ethanol versus the distance from the injector, were determined by an experimental-analytical method which did not require any assumption about the distribution, drag, and vaporization of the fuel drops (static pressure measurements were used instead). The steady-state spray equation is solved, for various drag and vaporization models, and the local flux of liquid ethanol thus calculated is compared with the experimentally determined one for the purpose of selecting a proper spray combustion model.

Bracco, F. V.↗
NASA NTRS1992

Steady state composition with low Fe(2+) concentrations for efficient O2 production by 'magma' electrolysis of lunar soils

Parameters are estimated for a hypothetical, well stirred, continuous-feed electrolytic cell that converts 20 percent of a lunar soil feedstock to O2 gas, 26 percent to Fe-Si metal, 13 percent to spinel, and 41 percent to slag. Advantages of a molten Fe-Si cathode for trapping metal on reduction, a relatively conductive steady-state composition in equilibrium with spinel (a proposed container material), and close electrodes (less than 1 cm cathode-anode distance) are discussed. To produce 1 ton of O2, about 6 MHW of energy are required for the electrolysis and IR heating within the melt, and another about 6 MHW may be introduced as waste heat through internal resistance of the electrodes. Thus, to produce 1 ton of O2 per 24 hours, about 0.5 MW of power delivered to the cell would be required.

Haskin, Larry A.↗