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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

High Fidelity Simulations of a Non-Premixed Rotating Detonation Engine

Over the last two decades, detonation based propulsion concepts have received a great deal of attention as a means to achieve significant improvement in the performance of air-breathing and rocket engines. Detonative combustion mode is particularly interesting due to the resulting pressure gain from reactants to products, faster heat release, decreased entropy generation, more available work and higher thrust compared to conventional deflagrative combustion. Rotating detonation engine (RDE) is one such class of novel combustor concepts. Realistic RDE configurations utilize separate fuel and air injection schemes, hence are not perfectly premixed. Moreover, the performance of RDEs is governed by a large number of design parameters and operating conditions. In this context, computational fluid dynamics (CFD) has the potential to enhance the understanding of RDE combustion and aid future development/optimization of this technology. In the present work, a CFD model was developed to simulate a representative non-premixed RDE combustor at the US Air Force Research Laboratory (AFRL). To resolve the reacting flow in the combustor, a finite-rate chemistry model was employed. In addition, adaptive mesh refinement (AMR) was incorporated to achieve a good trade-off between model accuracy and computational expense. Unsteady Reynolds-Averaged Navier-Stokes (RANS) simulations were performed for the full combustor (including the separate fuel and air injection ports) geometry, with hydrogen as fuel and air as the oxidizer. A 10-species detailed kinetic mechanism was employed to describe the H2-Air combustion chemistry. Two different operating conditions were simulated, corresponding to the same global equivalence ratio of unity but different fuel and air mass flow rates. For both conditions, the capability of the model to capture the essential detonation wave dynamics was assessed. A validation study was performed against a wide variety of experimental data available on detonation wave frequency/height, reactant fill height, oblique shock angle, axial pressure distribution in the channel, and fuel/air plenum pressure. The CFD model predicted the sensitivity of all these wave characteristics to the operating conditions with good accuracy, both qualitatively and quantitatively. The present CFD model offers a potential capability to perform rapid design space exploration and/or performance optimization studies for realistic full-scale RDE configurations.

Cocks, Peter A.↗
DOE OSTI2023

High-Fidelity Simulations of Plasma-Assisted Oxidation of Hydrocarbon Fuels Using Nanosecond Pulsed Discharges

Next, a robust and efficient framework for simulating NSPD in multiple dimensions is developed. The reactive Navier-Stokes equations are extended to include a drift-diffusion plasma-fluid model with a local field approximation (LFA) in a finite-volume solver, which uses an adaptive mesh refinement (AMR) strategy to address the wide separation of length scales in the problem. A two-way coupling strategy is used whereby the plasma-fluid model and reactive Navier-Stokes equations are integrated simultaneously. The oxidation of ethylene/air mixtures mediated by NSPD is simulated in a pin-to-pin configuration. All phases of the plasma discharge are simulated explicitly (including streamer ignition, propagation, and connection, as well as the subsequent spark phase), along with the evolution of the plasma during the inter-pulse period. Temporally and spatially-resolved results are presented, with an emphasis on the analysis of heating and energy deposition, as well as of the evolution of the concentration of active particles generated during the NSPD and their influence on ignition.

adaptive mesh refinement↗
DOE OSTI2024

Modeling Dense Particle Flow in Multistage and Obstructed Flow Receivers Using High Fidelity Simulations

Particles are a leading contender for next-generation, concentrating solar power technologies, and the design of the particle receiver is critical to minimize the levelized cost of electricity. Falling particle receivers (FPRs) are a viable receiver concept, but many new designs feature complex particle obstructions that include dense discrete phase flows. This creates additional challenges for modeling as particle-to-particle interactions (i.e., collisions) and particle drag become more complex. To improve upon existing modeling strategies, a CFD-DEM simulation capability was created by coupling two independent codes: Sierra/Fuego and LAMMPS. A suitable receiver model was then defined using a traditional continuum-based model for the air and a granular model for the particle curtain. A sensitivity study was executed using this model to determine the relevance of different granular model inputs on important quantities of interest in obstructed flow FPRs: the particle velocity and curtain opacity. The study showed that the granular model inputs had little effect on the particle velocity magnitude and curtain opacity after an obstruction.

Mills, Brantley↗
DOE OSTI2012

Preliminary high-fidelity simulation of duct wall deformation in sodium fast reactor subassembly

Computational Fluid Dynamics simulations of nuclear energy systems have received extensive interest and have achieved a certain level of maturity. This gives opportunities for a more realistic mechanical analysis of a sodium fast reactor subassembly that is based on more accurate estimates of pressure and temperature distributions within a subassembly. In fast reactor systems, important reactivity feedbacks can be a result of such subassembly duct wall deformation, with an impact on reactor safety considerations. The structural analysis in this work focuses on the stress-strain distributions in a fast reactor subassembly duct wall that are the result of pressure and temperature gradients across the duct. The RANS-based commercial CFD software STAR-CCM+ was used to perform the structural analysis of the duct wall in a 61-pin subassembly that was irradiated in EBR-II as a lead test subassembly. A loose coupling was performed for the thermal-hydraulics and structural mechanics to reduce the mesh cell number and computation time. It is found that the duct wall displacements are dominated by the thermal expansion, but the stress distributions are dominated by the pressure gradients between the inside and outside of the duct. However, the predicted stresses were far less than the yield stress, indicating large margin to the structural integrity of the non-irradiated duct wall. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Review of recent activities with MOOSE, an open-source finite element & finite volume multi-fidelity simulation framework

Modeling and simulation are an increasing part of engineering. This is undoubtedly driven by the high costs of constructing experimental facilities, but also enabled by the exponential increase in computing powers over the last decades, which allows computational models to be closer than ever to reality. One of the main drivers for the development of MOOSE is supporting advanced nuclear reactor simulations. A challenging aspect of modeling advanced nuclear reactors is the plurality of physics involved, including neutronics, thermal hydraulics and fuel performance. These physics are all coupled to some extent and are generally solved in a sequential but iterative fashion. The United States (U.S.) national laboratories have been developing MOOSE, an open source multiphysics framework since its inception at the Idaho National Laboratory (INL) in 2008. This framework enables seamless coupling of multiphysics simulations and facilitates the implementation of new physics and material governing laws. It is continuously expanded with novel numerical methods and new pre-implemented physics module. Numerous applications, developed within the Department of Energy (DOE) laboratories, academia, and industry, including outside of nuclear engineering, have been developed to study specialized physics problems. International collaborations are welcome on this open-source modeling and simulation project.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗