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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Multi-scale evaluation of diesel commuter rail fuel use, emissions, and eco-driving

Diesel commuter rail emissions affect populations near rail corridors. An approach is demonstrated to quantify mesoscale and microscale diesel commuter rail fuel use and emission rates (FUERs) of CO 2 , CO, NO x , particulate matter, and total hydrocarbons based on two U.S. systems. A speed trajectory simulator, an energy model, and an emissions model were calibrated, evaluated, and applied. FUERs and potential reductions from eco-driving were quantified based on simulated trajectories. Hotspots were defined as sections with ≥ 90 th percentile of section-average FUERs by species. A few key variables explain 74–80% of variability in mesoscopic and microscopic FUERs. On average, FUERs are 7–8 times greater for hotspots than non-hotspots. Eco-driving was estimated to reduce segment-average FUERs by 3–33% and eliminate 2–11% hotspots. However, mesoscale oriented eco-driving can, at some locations, increase microscopic FUERs. The approach is adaptable to other diesel commuter rail systems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Genetic Algorithm-Based Commutation Angle Control for Torque Ripple Mitigation in Switched Reluctance Motor Drives

This work addresses the application of the Genetic Algorithm (GA) technique to optimize the commutation angles of a 2 kW 8/6 switched reluctance machine (SRM). The primary goal is to reduce the well-known drawback of SRMs: the torque ripple. Firstly, the machine was modeled in Matlab /Simulink ® using lookup tables obtained via finite element method (FEM) simulations. Subsequently, the model was used to perform the GA routine aiming to find the optimal phase commutation angles that minimize the torque ripple factor. Notably, the torque performance of the SRM was significantly affected by the commutation angles during the search for the optimal solution. Afterwards, the GA results for four different operation points were verified experimentally through a developed drive platform with digital signal processor-based (DSP) control and an asymmetric bridge converter. As showed by the experiments, the proposed approach was suitable to reduce the torque ripple by more than 50% for one of the evaluated operating points. Furthermore, it was confirmed that the torque ripple mitigation led to acoustic noise improvement.

42 ENGINEERING↗
DOE OSTI2018

High performance Data Driven Agent-based Modeling Framework for Simulation of Commute Mode Choices in Metropolitan Area

Active transportation, human-powered transportation modes such as walking and bicycling, not only reduces the carbon footprint from the transportation sector but also promotes healthy living by offering opportunities for people to build physical activity into their daily routine. To encourage active transportation through urban planning and public campaigns, it is of significant importance to infer factors that substantially influence commuters in their transportation mode choice process. This necessitates a flexible and repeatable tool that can evaluate how a policy is perceived by individual commuters and convert their decisions into macro level understanding. This paper introduces one such effort that is specifically designed for studies of transportation mode choices in metropolitan areas. It provides results from a high-resolution data driven simulation based on high performance computing implementation of the agent-based model framework for home-to-work commute trips. The framework uses a graph-partition based technique that can leverage the interaction structure of agents within a geographic proximity and can boost the simulation execution time. Further, based on a flexible design, it can run ABM with different levels of computing resources-from multi core workstations to an HPC grid. The framework has been tested on the Titan Cray XK7 supercomputer of the Oak Ridge Leadership Computing Facility.

Park, Byung↗
DOE OSTI2014

Radar Channel Balancing with Commutation

When multiple channels are employed in a pulse-Doppler radar, achieving and maintaining balance between the channels is problematic. In some circumstances the channels may be commutated to achieve adequate balance. Commutation is the switching, trading, toggling, or multiplexing of the channels between signal paths. Commutation allows modulating the imbalance energy away from the balanced energy in Doppler, where it can be mitigated with filtering.

42 ENGINEERING↗
NASA NTRS1972

Hybrid circuit modules for motor commutation and control

Thick film hybrid techniques are used to develop circuitry for a brushless dc motor commutator. The power commutator contains the driving circuit and an amplifier that controls the armature current. A position decoder contains digital integrated circuits which receive the signals from the armature position sensors and generate the driving signals for the power commutator in the proper sequence. These units drive motors with stall currents up to about 400 mA.

Dekramer, C.↗
NASA NTRS1976

A study of commuter airline economics

Variables are defined and cost relationships developed that describe the direct and indirect operating costs of commuter airlines. The study focused on costs for new aircraft and new aircraft technology when applied to the commuter airline industry. With proper judgement and selection of input variables, the operating costs model was shown to be capable of providing economic insight into other commuter airline system evaluations.

Summerfield, J. R.↗
NASA NTRS1980

Toward new small transports for commuter airlines

The article discusses the results of a survey of commuter airline operators and large and small airframe manufacturers conducted by the Small Transport Aircraft Technology Office of the NASA Ames Research Center. Attention is given to economic concerns of the operator and manufacturer, as well as social concerns of the passenger, community, and system. Discussion also covers research and technology opportunities for improving commuter aircraft, and provides a background of information on the commuter and short-haul local-service air carriers, regulations pertaining to their aircraft, and operations, overall airline interfaces, and facility requirements.

Giulianetti, D. J.↗
NASA NTRS1985

Commutating Permanent-Magnet Motors At Low Speed

Circuit provides forced commutation during starting. Forced commutation circuit diverts current from inverter SCR's and turns SCR's off during commutation intervals. Silicon controlled rectifier in circuit unnecessary when switch S10 replaced by high-current, high-voltage transistor. At present, high-current, low-voltage device must suffice.

Dolland, C.↗
NASA NTRS1984

Design of a digital ride quality augmentation system for commuter aircraft

Commuter aircraft typically have low wing loadings, and fly at low altitudes, and so they are susceptible to undesirable accelerations caused by random atmospheric turbulence. Larger commercial aircraft typically have higher wing loadings and fly at altitudes where the turbulence level is lower, and so they provide smoother rides. This project was initiated based on the goal of making the ride of the commuter aircraft as smooth as the ride experienced on the major commercial airliners. The objectives of this project were to design a digital, longitudinal mode ride quality augmentation system (RQAS) for a commuter aircraft, and to investigate the effect of selected parameters on those designs.

Hammond, T. A.↗
NASA NTRS1987

A cost analysis for the implementation of commonality in the family of commuter airplanes, revised

The acquisition costs determined for the NASA family of commute airplanes are presented. The costs of the baseline designs are presented along with the calculated savings due to the commonality in the family. A sensitivity study is also presented to show the major drivers in the acquisition cost calculations. The baseline costs are calculated with the Nicolai method. A comparison is presented of the estimated costs for the commuter family with the actual price for existing commuters. The cost calculations for the engines and counter-rotating propellers are reported. The effects of commonality on acquisition costs are calculated. The sensitivity calculations of the cost to various costing parameters are shown. The calculations for the direct operating costs, with and without commonality are presented.

Creighton, Tom↗
NASA NTRS1991

The FM-007: An advanced jet commuter for HUB to spoke transportation

Due to the increasing need for new commuter aircraft, the FM-007 is proposed, a technologically advanced jet propelled short takeoff and landing (STOL) airplane. The proposed commuter is designed for hub to spoke air travel. In order to reduce drag, natural laminar flow technology is integrated into the design using the natural laminar flow airfoil section for the wing. A three lifting surface configuration provides for more efficient cruise flight. This unique design includes a small forward wing (canard), a rear mounted high aspect ratio main wing, and a small horizontal stabilizer high atop the vertical tail. These three surfaces act together to reduce drag by minimizing the downward force the horizontal stabilizer has to account for due to the nose down pitching moment. Commuter aircraft must also incorporate passenger comfort. This is achieved by providing a spacious pressurized cabin with a large galley and reduced cabin noise due to incorporation of noise reduction gear. A basic oval design is adopted, as opposed to a circular design in order to allow for the seating of five passengers abreast. To get STOL capability, an over the wing blown flap is used using a Rolls Royce Tay series engine.

Blouke, Peter Scott↗
NASA NTRS1995

Mechanism For Adjustment Of Commutation Of Brushless Motor

Mechanism enables adjustment of angular position of set of Hall-effect devices that sense instantaneous shaft angle of brushless dc motor. Outputs of sensors fed to commutation circuitry. Measurement of shaft angle essential for commutation; that is, application of voltage to stator windings must be synchronized with shaft angle. To obtain correct angle measurement for commutation, Hall-effect angle sensors positioned at proper reference angle. The present mechanism accelerates adjustment procedure and makes it possible to obtain more accurate indication of minimum-current position because it provides for adjustment while motor running.

Schaefer, Richard E.↗
NASA NTRS1998

"2001: A Space Odyssey" Revisited--The Feasibility of 24 Hour Commuter Flights to the Moon Using NTR Propulsion with LUNOX Afterburners

The prospects for "24 hour" commuter flights to the Moon, similar to that portrayed in 2001: A Space Odyssey but on a more Spartan scale, are examined using two near term, "high leverage" technologies--liquid oxygen (LOX)-augmented nuclear thermal rocket (NTR) propulsion and "lunar-derived" oxygen (LUNOX) production. Ironrich volcanic glass, or "orange soil," discovered during the Apollo 17 mission to Taurus-Littrow, has produced a 4% oxygen yield in recent NASA experiments using hydrogen reduction. LUNOX development and utilization would eliminate the need to transport oxygen supplies from Earth and is expected to dramatically reduce the size, cost and complexity of space transportation systems. The LOX-augmented NTR concept (LANTR) exploits the high performance capability of the conventional liquid hydrogen (LH2)-cooled NTR and the mission leverage provided by LUNOX in a unique way, LANTR utilizes the large divergent section of its nozzle as an "afterburner" into which oxygen is injected and supersonically combusted with nuclear preheated hydrogen emerging front the engine's choked sonic throat--essentially "scramjet propulsion in reverse." By varying the oxygen-to-hydrogen mixture ratio, the LANTR engine can operate over a wide range of thrust and specific impulse (Isp) values while the reactor core power level remains relatively constant. The thrust augmentation feature of LANTR means that "big engine" performance can be obtained using smaller, more affordable, easier to test NTR engines. The use of high-density LOX in place of low-density LH2 also reduces hydrogen mass and tank volume resulting in smaller space vehicles. An implementation strategy and evolutionary lunar mission architecture is outlined which requires only Shuttle C or "in-line" Shuttle-derived launch vehicles, and utilizes conventional NTR-powered lunar transfer vehicles (LTVs), operating in an "expendable mode" initially, to maximize delivered surface payload on each mission. The increased payload is dedicated to installing "modular" LUNOX production units with the intent of supplying LUNOX to lunar landing vehicles (LLVS) and then LTVs at the earliest possible opportunity. Once LUNOX becomes available in low lunar orbit (LLO), monopropellant NTRs would be outfitted with an oxygen propellant module, feed system and afterburner nozzle for "bipropellant" operation. Transition to a "reusable" mission architecture now occurs with smaller, LANTR-powered LTVs delivering approximately 400% more payload on each piloted round trip mission than earlier expendable "all LH2" NTR systems. As initial lunar outposts grow to eventual lunar settlements and LUNOX production capacity increases, the LANTR concept can enable a rapid "commuter" shuttle capable of 24 hour "one way" trips to and from the Moon, A vast deposit of"iron-rich" volcanic glass beads identified at just one candidate site--located at the southeastern edge of Mare Serenitatis--could supply, sufficient LUNOX to support daily commuter flights to the Moon for the next 9000 years!

Borowski, Stanley K.↗
NASA NTRS2001

"2001: A Space Odyssey" Revisited: The Feasibility of 24 Hour Commuter Flights to the Moon Using NTR Propulsion with LUNOX Afterburners

The prospects for "24 hour" commuter flights to the Moon. similar to that portrayed in 2001: A Space Odyssey but on a more Spartan scale. are examined using two near term. "high leverage" technologies-liquid oxygen (LOX)-augmented nuclear thermal rocket (NTR) propulsion and "lunar-derived" oxygen (LUNOX) production. Iron-rich volcanic glass. or "orange soil," discovered during the Apollo 17 mission to Taurus-Littrow. has produced a 4% oxygen yield in recent NASA experiments using hydrogen reduction. LUNOX development and utilization would eliminate the need to transport oxygen supplies from Earth and is expected to dramatically reduce the size, cost and complexity of space transportation systems. The LOX-augmented NTR concept (LANTR) exploits the high performance capability of the conventional liquid hydrogen (LH2)-cooled NTR and the mission leverage provided by LUNOX in a unique way. LANTR utilizes the large divergent section of its nozzle as an "afterburner" into which oxygen is injected and supersonically combusted with nuclear preheated hydrogen emerging from the engine's choked sonic throat-essentially "scramjet propulsion in reverse." By varying the oxygen-to-hydrogen mixture ratio, the LANTR engine can operate over a wide range of thrust and specific impulse (Isp) values while the reactor core power level remains relatively constant. The thrust augmentation feature of LANTR means that "big engine" performance can be obtained using smaller. more affordable. easier to test NTR engines. The use of high-density LOX in place of low-density LH2 also reduces hydrogen mass and tank volume resulting in smaller space vehicles. An implementation strategy and evolutionary lunar mission architecture is outlined which requires only Shuttle C or "in-line" Shuttle-derived launch vehicles, and utilizes conventional NTR-powered lunar transfer vehicles (LTVs), operating in an "expendable mode" initially, to maximize delivered surface payload on each mission. The increased payload is dedicated to installing "modular" LUNOX production units with the intent of supplying LUNOX to lunar landing vehicles (LLVs) and then LTVs at the earliest possible opportunity. Once LUNOX becomes available in low lunar orbit (LLO), monopropellant NTRs would be outfitted with an oxygen propellant module, feed system and afterburner nozzle for "bipropellant" operation. Transition to a "reusable" mission architecture now occurs with smaller, LANTR-powered LTVs delivering approximately 400% more payload on each piloted round trip mission than earlier expendable "all LH2" NTR systems. As initial lunar outposts grow to eventual lunar settlements and LUNOX production capacity increases, the LANTR concept can enable a rapid "commuter" shuttle capable of 24 hour "one way" trips to and from the Moon. A vast deposit of "iron-rich" volcanic glass beads identified at just one candidate site - located at the southeastern edge of Mare Serenitatis - could supply sufficient LUNOX to support daily commuter flights to the Moon for the next 9000 years'.

Borowski, Stanley K.↗
NASA NTRS2003

2001: A Space Odyssey Revisited: The Feasibility of 24 Hour Commuter Flights to the Moon Using NTR Propulsion with LUNOX Afterburners

The prospects for 24 hour commuter flights to the Moon, similar to that portrayed in 2001: A Space Odyssey but on a more Spartan scale, are examined using two near term, high leverage technologies: liquid oxygen (LOX)-augmented nuclear thermal rocket (NTR) propulsion and lunar-derived oxygen (LUNOX) production. Iron-rich volcanic glass, or orange soil, discovered during the Apollo 17 mission to Taurus-Littrow, has produced a 4 percent oxygen yield in recent NASA experiments using hydrogen reduction. LUNOX development and utilization would eliminate the need to transport oxygen supplies from Earth and is expected to dramatically reduce the size, cost and complexity of space transportation systems. The LOX-augmented NTR concept (LANTR) exploits the high performance capability of the conventional liquid hydrogen (LH2)-cooled NTR and the mission leverage provided by LUNOX in a unique way. LANTR utilizes the large divergent section of its nozzle as an afterburner into which oxygen is injected and supersonically combusted with nuclear preheated hydrogen emerging from the engine's choked sonic throat, essentially scramjet propulsion in reverse. By varying the oxygen-to-hydrogen mixture ratio, the LANTR engine can operate over a wide range of thrust and specific impulse (Isp) values while the reactor core power level remains relatively constant. The thrust augmentation feature of LANTR means that big engine performance can be obtained using smaller, more affordable, easier to test NTR engines. The use of high-density LOX in place of low density LH2 also reduces hydrogen mass and tank volume resulting in smaller space vehicles. An implementation strategy and evolutionary lunar mission architecture is outlined which requires only Shuttle C or in-line Shuttle-derived launch vehicles, and utilizes conventional NTR-powered lunar transfer vehicles (LTVs), operating in an expendable mode initially, to maximize delivered surface payload on each mission. The increased payload is dedicated to installing modular LUNOX production units with the intent of supplying LUNOX to lunar landing vehicles (LLVs) and then LTVs at the earliest possible opportunity. Once LUNOX becomes available in low lunar orbit (LLO), monopropellant NTRs would be outfitted with an oxygen propellant module, feed system and afterburner nozzle for bipropellant operation. Transition to a reusable mission architecture now occurs with smaller, LANTR-powered LTVs delivering ~400% more payload on each piloted round trip mission than earlier expendable all LH2 NTR systems. As initial lunar outposts grow to eventual lunar settlements and LUNOX production capacity increases, the LANTR concept can enable a rapid commuter shuttle capable of 24 hour one way trips to and from the Moon. A vast deposit of iron-rich volcanic glass beads identified at just one candidate site located at the southeastern edge of Mare Serenitatis could supply sufficient LUNOX to support daily commuter flights to the Moon for the next 9000 years!

Borowski, Stanley↗
NASA NTRS1983

FET commutated current-FED inverter

A shunt switch comprised of a field-effect transistor (Q.sub.1) is employed to commutate a current-fed inverter (10) using thyristors (SCR1, SCR2) or bijunction transistors (Q.sub.2, Q.sub.3) in a full bridge (1, 2, 3, 4) or half bridge (5, 6) and transformer (T.sub.1) configuration. In the case of thyristors, a tapped inverter (12) is employed to couple the inverter to a dc source to back bias the thyristors during commutation. Alternatively, a commutation power supply (20) may be employed for that purpse. Diodes (D.sub.1, D.sub.2) in series with some voltage dropping element (resistor R.sub.12 or resistors R.sub.1, R.sub.2 or Zener diodes D.sub.4, D.sub.5) are connected in parallel with the thyristors in the half bridge and transformer configuration to assure sharing the back bias voltage. A clamp circuit comprised of a winding (18) negatively coupled to the inductor and a diode (D.sub.3) return stored energy from the inductor to the power supply for efficient operation with buck or boost mode.

Rippel, Wally E.↗
DOE OSTI2017

Phase–number uncertainty from Weyl commutation relations

We derive suitable uncertainty relations for characteristics functions of phase and number of a single-mode field obtained from the Weyl form of commutation relations. Some contradictions between the product and sums of characteristic functions are noted. - Highlights: • Phase–number uncertainty relations derived from Weyl commutation relations. • Phase–number uncertainty relations that include correlation terms. • Phase–number uncertainty relations in complete parallel with position–momentum.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Relativistic spectrum of hydrogen atom in the space-time non-commutativity

We study space-time non-commutativity applied to the hydrogen atom and its phenomenological effects. We find that it modifies the Coulomb potential in the Hamiltonian and add an r{sup -3} part. By calculating the energies from Dirac equation using perturbation theory, we study the modifications to the hydrogen spectrum. We find that it removes the degeneracy with respect to the total angular momentum quantum number and acts like a Lamb shift. Comparing the results with experimental values from spectroscopy, we get a new bound for the space-time non-commutative parameter.

74 ATOMIC AND MOLECULAR PHYSICS↗