Molecular Dynamics Simulations Confirm Hydrogen Bond Mediated Stability in the Engineered FAST protein [Poster]
Abstract not provided.
59 BASIC BIOLOGICAL SCIENCES↗
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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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Multi-dimensional computational combustion of highly dilute, premixed spark-ignited opposed-piston gasoline engine using direct chemistry with a new Primary Reference Fuel mechanism
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Mittal, Anshul↗
Grizzly Development for Light Water Reactor and Advanced Reactor Applications in Fiscal Year 2021
This report summarizes work performed during Fiscal Year (FY) 2021 at Idaho National Laboratory (INL) for the U.S. Department of Energy’s Nuclear Engineering Advanced Modeling and Simulation (NEAMS) program for the Structural Materials and Chemistry Technical Area in the work package entitled “MS-21IN050106 - Structural Materials - INL.” This effort mainly focused on development and application of capabilities for engineering-scale analysis of nuclear reactor structural components in the Grizzly and BlackBear codes. These efforts include performance improvements and application of models for high-temperature component response, cluster dynamics modeling of precipitation in light water reactor pressure vessel steel, engineering-scale capability development in the areas of concrete simulation and reactor pressure vessel analysis, and preparation for and conducting an independent assessment of the adherence of these codes to software quality standards.
36 MATERIALS SCIENCE↗
Diagnostics of the Supernova Engine
The standard engine behind core-collapse supernovae is continuously evolving with increasingly detailed models. At this time, most simulations focus on an engine invoking turbulence above the proto-neutron star, sometimes termed the “convection-enhanced” engine. Finally, we review this engine and why it has become the standard for normal supernovae, focusing on a wide set of observations that provide insight into the supernova engine.
79 ASTRONOMY AND ASTROPHYSICS↗
Model Development and Analysis of Clean and Efficient Engine Combustion FY 2018 Annual Progress Report
Simulations of 1D laminar flames using detailed kinetic mechanisms are useful in a wide variety of engine combustion applications. The most common use is in the computation of laminar flame speeds, which are useful for chemical mechanism validation, as inputs to turbulent flame speed correlations, and to predict knocking in spark-ignition engines. Other applications include generation of flamelet libraries for CFD simulations and prediction of combustion dynamics in micro-flow reactors. These fundamental combustion simulations are an important component in the study of realistic transportation fuel models in boosted spark-ignition and multi-mode engine configurations.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Evolution at the Edge: Real-Time Evolution for Neuromorphic Engine Control
Neuromorphic computing systems are attractive for real-time control at the edge because of their low power operation, real-time processing capabilities and their potential ability to do online learning. In this work, we describe an approach for performing real-time evolution of spiking neural networks for neuromorphic systems at the edge called Neuromorphic Optimization using Dynamic Evolutionary Systems or NODES. We apply this approach to real-time combustion engine control and develop an engine-specific hardware platform for NODES called FireBox. We demonstrate how the real-time evolution approach works in simulation and the performance of networks trained in simulation on the physical engine.
Maldonado Puente, Bryan [ORNL] (ORCID:000000033880↗
Reduced chemical model for low and high-temperature oxidation of fuel blends relevant to internal combustion engines
A hybrid approach is proposed to develop reduced kinetic models for complex engine-relevant fuels. The reduced mechanism is composed of a core submechanism including C0-C4 chemistry, ethanol chemistry, and NOx chemistry and a fuel-dependent submechanism. The fuel-dependent submechanism consists of three species and ten reactions describing both the low and high-temperature fuel decomposition pathways. Calibrations for these reactions can be made for single component and multicomponent mixtures using experimental targets or results from detailed kinetic mechanisms. In the present study, the methodology is applied to the combustion of gasoline surrogates. Reduced mechanisms are calibrated for primary references fuels and multicomponent mixtures at engine-relevant pressures. The reduced mechanisms capture the low-temperature heat release and negative temperature coefficient (NTC) behavior, which are important to simulations of internal combustion engine performance. The mechanisms are very compact in size and can be easily calibrated for multicomponent mixtures without any detailed knowledge of the chemistry of the fuel components, making them well suited for CFD simulations of new fuel blends.
02 PETROLEUM↗
Numerical study of advanced compression ignition and combustion in a gasoline direct injection engine
Multi-mode combustion strategies may provide a considerable thermal efficiency improvement targeted at part-load operating conditions for light-duty spark-ignition (SI) engines. The extension from boosted SI mode at high loads to advanced compression ignition (ACI) mode at low loads can be achieved by increasing compression ratio and utilizing intake air heating. In order to enable an accurate control of intake charge condition for ACI control and rapid mode-switches, it is essential to gain fundamental insight into the autoignition process with regard to thermal and fuel-air mixture stratification in the combustion chamber. In this work, a computational fluid dynamics (CFD) study is carried out to reveal some degrees of correlation between the mixture and thermal stratifications induced by the cylinder wall temperature and combustion-phasing across varying engine load conditions. The computational analysis begins with a calibrated simulation setup best matching the engine experiments, and subsequently evaluates the baseline setup for an extended range of engine load conditions for two excess-air ratio cases. The present study emphasizes the dominance of thermal stratifications for autoignition process due to wall temperature effects depending on the engine load conditions of interest. In addition, this study also aims to provide insight into the impact of mixture stratification on cyclic variability, especially at colder wall engine conditions (e.g., cold start). Observations herein provide highlight of the propensity of autoignition in correlation with mixture reactivity space.
Advanced Compression Ignition (ACI) engine↗
NEAMS-Multiphysics MOOSE End Year Framework Activities FY20
The Multiphysics Object Oriented Simulation Environment (MOOSE) is a general finite element package meant for high performance solution of multiphysics problems in science and engineering. In this report, we present additions and enhancements to MOOSE funded by the Nuclear Engineering Advanced Modeling and Simulation (NEAMS) program. NEAMS-funded MOOSE framework library improvements include: expansion of support for multi-level multi-application restart; enhancement of coupling between native MOOSE applications and external libraries; addition of a sparse automatic differentiation (AD) container enabling non-local degree of freedom coupling; block-specific quadrature rules; further development of an eigenvalue executioner; faster setup of periodic boundary conditions; and creation of a mesh meta-data system streamlining simulation startup. Besides developing the framework library, NEAMS funds were used to overhaul a swath of important MOOSE infrastructure in order to substantially improve user experience. These critical infrastructure changes included adapting MOOSE to python 3, improving the test harness to catch race conditions, and most importantly transitioning MOOSE to use Conda, a globally known packaging system, that greatly eases software adoption.
97 MATHEMATICS AND COMPUTING↗
Preliminary Design Studies for a Hydro-Growth Radiography Platform to Study the Double Shell Ablator Joint
Double shell target assembly requires mating two hemispheres of aluminum to form the ablator, and the design of the mating joint governs the dimensions of the gap that remains following ablator assembly. Radiographic data from double shell implosions with two different joint designs demonstrate the importance of having a smaller outer gap to minimize perturbation growth, but higher quality data is desirable for validating simulations of such localized engineering features. A double shell hydrogrowth radiography platform is proposed to enable detailed measurements of the joint feature evolution for comparison to simulation predictions. The conservative design is based on a successfully fielded double shell keyhole target, but the tungsten inner shell is replaced with molybdenum to allow imaging with X-rays from a zirconium backlighter (16.3 keV). Eulerian radiation-hydrodynamics simulations with adaptive mesh refinement are used to predict joint feature evolution for several different joint designs. Synthetic radiographs produced from ablator-only calculations demonstrate that the evolution of different joint morphologies can be radiographed and distinguished. Feedthrough of the joint perturbation to a molybdenum inner shell is predicted to be measurable at a convergence ratio of 2.
36 MATERIALS SCIENCE↗
ExaDigiT/RAPS
ExaDigiT is a framework for developing comprehensive digital twins of liquid-cooled supercomputers, which has three main modules: (1) a python-based Resource Allocator and Power Simulator (RAPS), (2) a Modelica-based Thermo-Fluidic cooling model, and (3) a C++-based augmented reality model built on Unreal Engine 5. RAPS either simulates workloads or replays historical workloads from system telemetry, and is able to predict dynamic energy consumption, as well as interact with the cooling model to predict cooling system behavior. Such a tool can be used together with reinforcement learning algorithms to provide an end-to-end optimization tool for data centers.
Brewer, Wesley [Oak Ridge National Laboratory (ORN↗
Towards improved mesh-designing techniques of spark-ignition engines in the framework of spectral element methods
In the current paper we present an advanced meshing technique to perform high-fidelity numerical simulations in spark ignition (SI) engines. The design of the mesh is critical towards generating physically consistent, high fidelity data especially in regions of complex boundaries inside the cylinder, e.g., near the spark plugs. This is primarily due to the mesh deformation caused by the motion of the valve near the plug and also finer mesh sizes in the spark plug region. In the current work, we demonstrate the use of an overlapping grid (overset) methodology to design the mesh in the spark-plug region in a 2D SI engine-like geometry for a high-order simulation, based on the spectral element method (SEM). The data in the overlapping region is exchanged between the spark-plug geometry and the geometry containing rest of the objects like the piston, cylinder head, valve etc., using a high order spectral interpolation technique. The numerical simulations have been further compared against the standard, single (non-overset) grid, meshing technique for the whole 2D domain. The results further illustrate the capability of overlapping grid methodology in handling mesh deformation compared to the standard grid case and also the ability to capture the flow dynamics with a similar level of fidelity as the standard one
overlapping grids↗
Development of HELICS-Based High-Performance Cyber-Physical Co-Simulation Framework for Distributed Energy Resources Applications
The rapid growth of distributed energy resources (DERs) has prompted increasing interest in the monitoring and control of DERs through hybrid smart grid communications resulting in the typical smart grid cyber-physical system. To fully understand the interdependency between them, we propose to integrate the Network Simulator 3 (NS3) into the High Engine for Large-Scale Infrastructure Co-Simulation (HELICS), a new open-source, cyber-physical-energy co-simulation platform. This paper aims to the development and case study of the HELICS-based high performance distribution-communication co-simulation framework for the DER coordination. The novel co-simulation framework for the NS3 integrating into the HELICS is developed. The DER monitoring application about hybrid smart grid communication network design is simulated and validated on this proposed HELICS-based cyber-physical co-simulation platform.
41 EE - Solar Energy Technologies Office (EE-4S)↗
Flexible Production Systems with Probabilistic Perturbations
Probabilistic perturbations associated with scattering of the operating periods and equipment faults in flexible production systems are considered. The perturbations are taken into account in computer simulation of the operation of a flexible production system. The proposed modeling application is described.
42 ENGINEERING↗
Aerodynamic Improvement of a Compact Centrifugal Compressor
For the example of the JetCat P-200RX turbojet engine, optimization of the diffuser and straightening unit of a compact centrifugal compressor is considered, on the basis of a mathematical model of viscous turbulent air flow. The goal of optimization is to increase the isentropic (adiabatic) efficiency of the compressor.
42 ENGINEERING↗
Experimental realization of an extended Fermi-Hubbard model using a 2D lattice of dopant-based quantum dots
The Hubbard model is an essential tool for understanding many-body physics in condensed matter systems. Artificial lattices of dopants in silicon are a promising method for the analog quantum simulation of extended Fermi-Hubbard Hamiltonians in the strong interaction regime. However, complex atom-based device fabrication requirements have meant emulating a tunable two-dimensional Fermi-Hubbard Hamiltonian in silicon has not been achieved. Here, we fabricate 3 × 3 arrays of single/few-dopant quantum dots with finite disorder and demonstrate tuning of the electron ensemble using gates and probe the many-body states using quantum transport measurements. By controlling the lattice constants, we tune the hopping amplitude and long-range interactions and observe the finite-size analogue of a transition from metallic to Mott insulating behavior. We simulate thermally activated hopping and Hubbard band formation using increased temperatures. As atomically precise fabrication continues to improve, these results enable a new class of engineered artificial lattices to simulate interactive fermionic models.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Multidimensional Numerical Simulations of Knocking Combustion in a Cooperative Fuel Research Engine
A numerical approach was developed based on multidimensional computational fluid dynamics (CFD) to predict knocking combustion in a cooperative fuel research (CFR) engine. G-equation model was employed to track the turbulent flame front and a multizone model was used to capture auto-ignition in the end-gas. Furthermore, a novel methodology was developed wherein a lookup table generated from a chemical kinetic mechanism could be employed to provide laminar flame speed as an input to the Gequation model, instead of using empirical correlations. To account for fuel chemistry effects accurately and lower the computational cost, a compact 121-species primary reference fuel (PRF) skeletal mechanism was developed from a detailed gasoline surrogate mechanism using the directed relation graph (DRG) assisted sensitivity analysis (DRGASA) reduction technique. Extensive validation of the skeletal mechanism was performed against experimental data available from the literature on both homogeneous ignition delay and laminar flame speed. The skeletal mechanism was used to generate lookup tables for laminar flame speed as a function of pressure, temperature, and equivalence ratio. The numerical model incorporating the skeletal mechanism was employed to perform simulations under research octane number (RON) and motor octane number (MON) conditions for two different PRFs. Parametric tests were conducted at different compression ratios (CR) and the predicted values of critical CR, delineating the boundary between “no knock” and “knock,” were found to be in good agreement with available experimental data. The virtual CFR engine model was, therefore, demonstrated to be capable of adequately capturing the sensitivity of knock propensity to fuel chemistry.
CFD↗
Assessment of flamelet/progress variable methods for supersonic combustion
Tabulated chemistry models, including the flamelet/progress variable approach, have been successfully used for a variety of turbulent flame simulations. The progress variable describes the progress of reactions in a system and parameterizes a lookup table of thermochemical variables. This approach reduces the cost of simulations, transporting only one scalar (progress variable) instead of the many species mass fractions required for detailed chemistry. Originally developed for low Mach number flame simulations, recent works have focused on extensions of this approach to compressible flames, supersonic combustion, and detonations, with applications such as scramjet combustors and rotating detonation engines. Unlike low Mach simulations, compressible flow simulations require solving the energy transport equation, which is coupled to the equation of state. This leads to additional modeling challenges regarding the thermodynamics and its impact on the chemistry. The validity of modeling assumptions, for example the relationship between energy and temperature, also varies with the combustion regime. The present work provides a detailed assessment of the existing strategies for chemistry tabulation for compressible/supersonic combustion, including detonations. A priori analysis indicates that approximations which are reasonable for weakly compressible flames may break down for shock-induced combustion. Furthermore, the analysis identifies specific assumptions and approximations that do not hold for detonations, emphasizing that care must be taken when applying tabulated chemistry models outside their intended combustion regimes.
Detonations↗