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At least 937 records · Page 52

All sources NASA NTRS DOE OSTI

NASA NTRS1991

Near-term, 100-kW class ion engines

A design approach for large area, high power ion engines is presented. This approach conceptually divides a single engine into a combination of smaller discharge chambers (or segments) configured to operate as a single large area engine. This segmented ion thruster (SIT) approach is shown to enable the immediate development of 100-kW class argon ion engines for operation at a specific impulse of 10,000 s. A combination of six 30-cm diameter ion chambers operating as a single engine can process over 100 kW. Such a segmented ion engine could be built today and would operate from a single power processor unit. The segmented engine design approach may also enable the development of megawatt class ion engines. Potential benefits of the segmented ion thruster design include: mitigation of the span-to-gap problem central to the development of large area, high power ion engines; reduction in hollow cathode emission current requirements; improved fault tolerance; and reduced vacuum system pumping speed requirements for engine development testing.

Brophy, John R.↗

NASA NTRS1976

Computer method for design of acoustic liners for turbofan engines

A design package is presented for the specification of acoustic liners for turbofans. An estimate of the noise generation was made based on modifications of existing noise correlations, for which the inputs are basic fan aerodynamic design variables. The method does not predict multiple pure tones. A target attenuation spectrum was calculated which was the difference between the estimated generation spectrum and a flat annoyance-weighted goal attenuated spectrum. The target spectrum was combined with a knowledge of acoustic liner performance as a function of the liner design variables to specify the acoustic design. The liner design method at present is limited to annular duct configurations. The detailed structure of the liner was specified by combining the required impedance (which is a result of the previous step) with a mathematical model relating impedance to the detailed structure. The design procedure was developed for a liner constructed of perforated sheet placed over honeycomb backing cavities. A sample calculation was carried through in order to demonstrate the design procedure, and experimental results presented show good agreement with the calculated results of the method.

Minner, G. L.↗

DOE OSTI2022

Full-scale FEED Study for Retrofitting the Prairie State Generating Station with an 816 MWe Capture Plant using Mitsubishi Heavy Industries Post-Combustion CO 2 Capture Technology

A full front-end engineering design (FEED) study to for a carbon capture system for Unit #2 (816 MWe) at the Prairie State Generating Company’s (PSGC) Energy Campus in Marissa, IL based on the KM CDR Process CO 2 capture technology from Mitsubishi Heavy Industries (MHI) using their proprietary solvent KS-21TM. If built this carbon capture plant would be the world's largest to date. The cost of capture of 100 percent of the plant emissions was calculated to be $43.42 per metric tonne of CO 2 based on levelized costs for 30 years of operation (85% capacity factor), and includes Interest on Debt and Return on Equity During Operation.

01 COAL, LIGNITE, AND PEAT↗

NASA NTRS1996

Cascade Optimization Strategy for Aircraft and Air-Breathing Propulsion System Concepts

Design optimization for subsonic and supersonic aircraft and for air-breathing propulsion engine concepts has been accomplished by soft-coupling the Flight Optimization System (FLOPS) and the NASA Engine Performance Program analyzer (NEPP), to the NASA Lewis multidisciplinary optimization tool COMETBOARDS. Aircraft and engine design problems, with their associated constraints and design variables, were cast as nonlinear optimization problems with aircraft weight and engine thrust as the respective merit functions. Because of the diversity of constraint types and the overall distortion of the design space, the most reliable single optimization algorithm available in COMETBOARDS could not produce a satisfactory feasible optimum solution. Some of COMETBOARDS' unique features, which include a cascade strategy, variable and constraint formulations, and scaling devised especially for difficult multidisciplinary applications, successfully optimized the performance of both aircraft and engines. The cascade method has two principal steps: In the first, the solution initiates from a user-specified design and optimizer, in the second, the optimum design obtained in the first step with some random perturbation is used to begin the next specified optimizer. The second step is repeated for a specified sequence of optimizers or until a successful solution of the problem is achieved. A successful solution should satisfy the specified convergence criteria and have several active constraints but no violated constraints. The cascade strategy available in the combined COMETBOARDS, FLOPS, and NEPP design tool converges to the same global optimum solution even when it starts from different design points. This reliable and robust design tool eliminates manual intervention in the design of aircraft and of air-breathing propulsion engines where it eases the cycle analysis procedures. The combined code is also much easier to use, which is an added benefit. This paper describes COMETBOARDS and its cascade strategy and illustrates the capability of the combined design tool through the optimization of a subsonic aircraft and a high-bypass-turbofan wave-rotor-topped engine.

Patnaik, Surya N.↗

NASA NTRSDate not supplied

Predictive Modeling to Assess and Address Challenges and Limitations Associated with Clinical Care and Decision Support in Deep Space

Probabilistic risk assessment (PRA) is a method for assessing and integrating the risk of failure in a multivariate system. While it is often applied by engineers designing complex machines, it could also be applied to humans to assess the probability of a health “failure” treating diseases as the multiple “variables” and the human as the “complex machine.” The Medical Extensible Dynamic Probabilistic Risk Assessment Tool (MEDPRAT) was developed to apply PRA to assess medical risk for exploration spaceflight and inform the design of medical systems for space flight. The NASA engineering community utilizes event-driven and fault tree probabilistic techniques to classify risk in the space flight environment by leveraging the inherent knowledge of complex space flight system design and testing to quantify risk. However, in harmonizing the risk of human space flight, answering the question of “How do we balance astronaut health, performance and resource risks with other engineering risks on exploration space missions?” remains a profoundly challenging and largely qualitative practice. The Medical Extensible Dynamic Probabilistic Risk Assessment Tool (MEDPRAT) is one aspect of the Human Research Program’s efforts to represent space fight human health and performance risks quantitatively.

L Mcintyre↗

DOE OSTI2020

An Update to the National Renewable Energy Laboratory Baseline Wind Turbine Controller

The National Renewable Energy Laboratory's 5-MW wind turbine model is well established as an industry standard and is often used as a comparison model, or a model on which to build upon. Though effective, the legacy controller for the 5-MW wind turbine uses a simple algorithm that is not up to date with many industry standards. Additionally, as the research community has advanced into fast-paced development cycles, as systems engineering tools such as Wind-Plant Integrated System Design & Engineering Model (WISDEM ®) [1] are employed, and as a greater focus on controls co-design practices is encouraged, demand for a generic wind turbine controller has arisen. This work presents updates for the NREL 5-MW controller to a more modern control architecture, and establishes a generic tuning framework that can be easily adapted to various wind turbines. Based on initial results, the updated generic controller eases the automatic tuning process while maintaining or improving the performance of the legacy NREL 5-MW controller.

17 WIND ENERGY↗

NASA NTRS1981

Performance deterioration: An airline perspective

Certain features of engine design and installation are clearly demonstrating important advantages in engine performance retention. Bearing arrangement no doubt has an important role in performance retention. Four bearings seem to be insufficient while six are probably more than are required. A well designed five-bearing system would seem to be an optimum configuration. Bearings with over-hung components such as fans, should be designed to minimize such over-hang to limit associated wobble, which in turn leads to shroud rub, or to allow closer running clearances. Almost any effort to improve stiffness and generally reduce flexing of the engine structure will pay off significantly in performance retention, even at a weight penalty. For this reason cowl load sharing to provide additional rigidity at a low cost in additional weight and complexity is favored.

Andersen, N. B.↗

DOE OSTI2021

Towards standardized nuclear reactors: Seismic isolation and the cost impact of the earthquake load case

We report nuclear energy has a key role to play in global decarbonization. Impediments to the widespread deployment of reactors are their projected high capital cost and levelized cost of energy, and time required to analyze, design, license, construct, and commission them. The earthquake load case is a key cost driver for a new build nuclear plant, because near-surface soils and seismic hazard are different at each site, requiring site-specific analysis, design, engineering, qualification, licensing, and regulatory review, essentially making every design First-of-a-Kind (FoaK). To enable deployment at the scale needed for deep decarbonization, the cost and time impact of the seismic load case must be significantly mitigated, and plants must be standardized. Seismic base isolation has been proven to considerably reduce the earthquake response of structures and equipment but has yet to be applied to a nuclear power plant in the United States, in part because the financial impacts, positive or negative, are not known. Because there are no recent non-proprietary data to characterize the influence of the seismic load case on capital cost, it is difficult to confidently quantify the financial benefits of seismic isolation. Scheme-level designs of two fundamentally different advanced reactor buildings were developed to assemble cost data on the influence of the seismic load case. Both buildings were equipped with three bespoke pieces of safety-related equipment and analyzed for incremented levels of earthquake shaking to quantify the seismic penalty on equipment, in terms of vessel weights and horizontal accelerations. Using analysis results, a questionnaire was developed and transmitted to nuclear utilities, reactor developers, engineers, and equipment suppliers to collect cost data on engineering and fabrication costs for these unique pieces of safety-class equipment. Synthesis of the cost data showed that the seismic load case significantly affects the capital cost (sum of engineering and fabrication cost) of safety-class equipment, with engineering costs being comparable to fabrication costs. Standardization of safety-class equipment is made possible by seismic isolation, that is, equipment designed for minimal seismic robustness can resist earthquake shaking at a site of much higher seismic hazard. The average reduction in the capital cost of the safety-related equipment, enabled by seismic isolation, is a factor of two for FoaK equipment and a factor of five for standardized equipment.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2019

E-Area LLWF Final Closure Cap Design – Constructability Evaluation Criteria for the Plot 8 and NR07E Disposal Areas

SRNS Design Engineering has been asked to complete a constructability evaluation of the proposed final closure cap designs for the Plot 8 (Engineered Trenches ET07, ET08, and ET09) and 643-7E NRCDA (NR07E) disposal areas located outside the original E-Area Low-Level Waste Facility (ELLWF) footprint. This memorandum presents the guidelines and criteria for the constructability evaluation. A new conceptual design for the ELLWF closure cap is not requested at this time.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

In-Cylinder Diagnostics to Overcome Efficiency Barriers in Natural Gas Engines (LDRD 200166)

The high-level objective of this project is to solve national-security problems associated with petroleum use, cost, and environmental impacts by enabling more efficient use of natural-gas-fueled internal combustion engines. An improved science-base on end-gas autoignition, or “knock,” is required to support engineering of more efficient engine designs through predictive modeling. An existing optical diesel engine facility is retrofitted for natural gas fueling with laser-spark-ignition combustion to provide in-cylinder imaging and pressure data under knocking combustion. Zero-dimensional chemical-kinetic modeling of autoignition, adiabatically constrained by the measured cylinder pressure, isolates the role of autoignition chemistry. OH* chemiluminescence imaging reveals six different categories of knock onset that depend on proximity to engine surfaces and the in-cylinder deflagration. Modeling results show excellent prediction regardless of the knock category, thereby validating state-of-the-art kinetic mechanisms. The results also provide guidance for future work to build a science base on the factors that affect the deflagration rate.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2019

Scale-Up of Coal-Based Supercritical CO 2 cycle technology

The Allam Cycle is a transformational technology that enables a step change in the performance, efficiency, and cost of electricity for electrical generating units by using supercritical CO 2 (sCO 2 ) as the working fluid in the turbine for power generation. The objectives of this Phase I effort were to select a host site for a large pilot system through a process of down selection, develop a conceptual design, and conduct a pre-front-end engineering design (pre-FEED) study for a sCO 2 cycle pilot plant that uses domestic coal reserves as the primary feedstock, thereby furthering technology development of the coal-based Allam Cycle. The project was divided into four main tasks: 1) Project Management and Planning; 2) Conceptual Pilot Plant Definition and Host Site Selection; 3) Preliminary Design, Cost, and Schedule Development; and 4) Commitments and Environmental Information Volume (EIV). All project management activities occurred in Task 1. Host site selection was conducted in Task 2, while conceptual design and pre-FEED activities took place under Task 3. Task 4 enhanced the project by securing commitments for the next phase of the program and completing an initial EIV. The Great Plains Synfuels Plant (GPSP) has been selected as the host site for the large-scale pilot, and its owner, Dakota Gasification Company (DGC), is a committed partner. GPSP was compared to two other host site candidates during Phase I: the existing natural gas Allam Cycle facility in La Porte, Texas, and the Energy & Environmental Research Center’s (EERC) high-bay demonstration facility in Grand Forks, North Dakota. Costs for hosting the pilot plant were estimated for each facility, and those costs are shown in Table ES-1. Based on these estimates, the DGC site was clearly shown to be the lowest cost option and was selected as the host site for the project.

01 COAL, LIGNITE, AND PEAT↗

NASA NTRS1974

Enhancing simulation of efficiency with analytical tools

Some means of combining both computer simulation and anlytical techniques are indicated in order to mutually enhance their efficiency as design tools and to motivate those involved in engineering design to consider using such combinations. While the idea is not new, heavy reliance on computers often seems to overshadow the potential utility of analytical tools. Although the example used is drawn from the area of dynamics and control, the principles espoused are applicable to other fields. In the example the parameter plane stability analysis technique is described briefly and extended beyond that reported in the literature to increase its utility (through a simple set of recursive formulas) and its applicability (through the portrayal of the effect of varying the sampling period of the computer). The numerical values that were rapidly selected by analysis were found to be correct for the hybrid computer simulation for which they were needed. This obviated the need for cut-and-try methods to choose the numerical values, thereby saving both time and computer utilization.

Seltzer, S. M.↗

NASA NTRS1976

Future higher performance O2/H2 engine combustion cycle alternatives

The status of current and projected advanced O2/H2 rocket engine configurations for high-efficiency engine designs is examined. Particular attention is given to engine cycle configurations, operating pressures, and performance characteristics which can be foreseen for the engine configurations past the 1980 era for single-stage-to-orbit boosters and advanced space engines. The discussion covers potential O2/H2 performance gains achievable, engine cycle improvements, and projected O2/H2 engine component efficiency, weight, and other improvements foreseen through future development.

Wagner, W. R.↗

NASA NTRS1980

Orbit transfer vehicle engine study, phase A extension. Volume 1: Executive summary

A 1980 state-of-the-art advanced expander engine was configured that delivers near-optimum payload-performance and exhibits the simplicity reliability, and life characteristics required of the OTV mission. Engine optimization studies indicate that the performance of the conventional expander cycle engine can be improved substantially through combustion chamber surface area enhancement, thermal enhancement, turbine regeneration, and power cycle efficiency enhancement procedures. The 20K lb. thrust staged combustion engine can be adapted to operate at extended periods in the 1 to 2K lb. thrust regime. The study results indicate that long-life, high performnce operation in the low thrust mode can be achieved with minimum modifications (kitting) of the engine. Although the main contribution to mission success and crew safety stems from propulsion system redundancy, significant reliability can be gained from engine component redundancy, specific engine design features ensuring safety and reliability, including an engine health monitoring system, and from a total program approach to safety and reliability, such as that presently applied to the space shuttle.

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NASA NTRS1988

Research Reports: 1988 NASA/ASEE Summer Faculty Fellowship Program

The basic objectives are to further the professional knowledge of qualified engineering and science faculty members; to stimulate an exchange of ideas between participants and NASA: to enrich and refresh the research and teaching activities of the participants' institutions; and to contribute to the research objectives of the NASA centers. Topics addressed include: cryogenics; thunderstorm simulation; computer techniques; computer assisted instruction; system analysis weather forecasting; rocket engine design; crystal growth; control systems design; turbine pumps for the Space Shuttle Main engine; electron mobility; heat transfer predictions; rotor dynamics; mathematical models; computational fluid dynamics; and structural analysis.

Freeman, L. Michael↗

NASA NTRS1989

Materials compatibility with oxidizer-rich gases at elevated temperatures and pressure

An investigation of oxygen compatibility and resistance to ignition of candidate materials for use in a liquid rocket engine designed to incorporate an oxidizer rich preburner-LOX turbopump configuration was discussed. The program was divided into two basic tasks. The first task was to develop a preliminary design of an oxidizer turbopump preburner section complete with thermal and MS Parameter analyses and to develop a conceptual design of the main injector with a preliminary engine specification as the final product. The second task was directed totally at testing materials in oxygen-rich environments.

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NASA NTRS1990

Recent Stirling engine loss-understanding results

For several years, NASA and other U.S. government agencies have been funding experimental and analytical efforts to improve the understanding of Stirling thermodynamic losses. NASA's objective is to improve Stirling engine design capability to support the development of new engines for space power. An overview of these efforts was last given at the 1988 IECEC. Recent results of this research are reviewed.

Tew, Roy C.↗

NASA NTRS1990

Recent Stirling engine loss-understanding results

Tew, Roy C.↗