Results for “emission control” — Page 40

NASA NTRS2017

Concerns for Ozone Recovery

Reactive halogen gases containing chlorine (Cl) or bromine (Br) can destroy stratospheric ozone via catalytic cycles. The main sources of atmospheric reactive halogen are the long-lived synthetic chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride (CCl4), methyl chloroform (CH3CCl3), and bromine-containing halons, all of which persist in the atmosphere for years. These ozone-depleting substances are now controlled under the Montreal Protocol and its amendments. Natural methyl bromide (CH3Br) and methyl chloride (CH3Cl) emissions are also important long-lived sources of atmospheric reactive halogen. Rising concentrations of very-short-lived substances (VSLSs) with atmospheric lifetimes of less than half a year may also contribute to future stratospheric ozone depletion. A greater concern for ozone layer recovery is incomplete compliance with the Montreal Protocol, which will impact stratospheric ozone for many decades, as well as rising natural emissions as a result of climate change.

VSLS↗

NASA NTRS2021

Supersonic Transport Optimization to Mach 4

Commercially viable supersonic transports require solution spaces to a longish list of serious issues including high drag, heating, emissions, costs, weights, acoustics, etc. Report addresses potential approaches to these issues including drag reduction, flow control, propulsion/ fuels/energetics, and synergistic frontier aircraft configurations across the board proffering large increases in lift to drag ratio.

Dennis M Bushnell↗

NASA NTRSDate not supplied

Ab Initio Electronic Structure Calculations of CNN for CN Excitation Studies

Titan’s atmosphere is composed mostly of N 2 with a small amount of CH 4 , and so, shock layers around craft entering Titan’s atmosphere will contain a variety of molecules formed from H, C, and N atoms, including the cyanogen radical CN. Sensitivity analysis has shown that the radiative heat flux predicted by computational fluid dynamics (CFD) simulations of Titan entry has up to 14% uncertainty due to the rate coefficients for collisional (de)excitation reactions that control the population of CN in its first and second excited states. The red and violet emission bands from CN’s first and second excited states, respectively, are known to be large sources of radiative heat flux on capsules entering Titan’s atmosphere.[2, 3] So, the simulated population of CN in its first and second excited states is very important, but currently has some inherent uncertainty coming from the data for the rate coefficients for reaction 1. The goal of the present project is to provide improved rate coefficient data for these reactions from first principles quantum chemistry calculations. This work reports on preliminary electronic structure calculations generated at a large number of triatomic geometries of interest, which show multiple avoided crossings at collinear arrangements. This suggests that collisional (de)excitation of CN by N atoms is likely to proceed through these geometries.

Eric Geistfeld↗

NASA NTRS2010

Options to Accelerate Ozone Recovery: Ozone and Climate Benefits

The humankind or anthropogenic influence on ozone primarily originated from the chlorofluorocarbons and halons (chlorine and bromine). Representatives from governments have met periodically over the years to establish international regulations starting with the Montreal Protocol in 1987, which greatly limited the release of these ozone-depleting substances (DDSs). Two global models have been used to investigate the impact of hypothetical reductions in future emissions of ODSs on total column ozone. The investigations primarily focused on chlorine- and bromine-containing gases, but some computations also included nitrous oxide (N2O). The Montreal Protocol with ODS controls have been so successful that further regulations of chlorine- and bromine-containing gases could have only a fraction of the impact that regulations already in force have had. if all anthropogenic ODS emissions were halted beginning in 2011, ozone is calculated to be higher by about 1-2% during the period 2030-2100 compared to a case of no additional ODS restrictions. Chlorine- and bromine-containing gases and nitrous oxide are also greenhouse gases and lead to warming of the troposphere. Elimination of N 20 emissions would result in a reduction of radiative forcing of 0.23 W/sq m in 2100 than presently computed and destruction of the CFC bank would produce a reduction in radiative forcing of 0.005 W/sq m in 2100. This paper provides a quantitative way to consider future regulations of the CFC bank and N 20 emissions

Fleming, E. L.↗

NASA NTRSDate not supplied

Enabling a Weight Efficient Power System for an Electrified Turbofan Through Gearbox Design and Control

Electrified Aircraft Propulsion (EAP) concepts could enable various benefits through a variety of use-cases. Benefits are sought in the form of reduced fuel burn and emissions. Many of these concepts involve the electrification of gas turbine engines. Electrification is accomplished through the integration of electric machines (EMs) with the engine shafts, providing the ability to inject and/or extract power as desired. Energy storage is also a common feature. An often-overlooked feature of the analysis is the means of integrating the EMs with the engine shafts. A trivial solution is to allow each shaft to have its own dedicated EM through independent geartrains. However, non-trivial mechanical integration solutions could provide benefits when considered in coordination with control logic to manage the operation of the propulsion system. Here, such a solution is considered and is shown to have the potential to reduce weight for a relevant conceptual electrified propulsion system. Weight saving benefits are demonstrated for various EAP use-cases. In particular, the mild hybrid application was shown to benefit from a power system weight reduction of 47% and an overall system weight reduction of 29%.

Hybrid Electric Propulsion↗

NASA NTRSDate not supplied

Enabling a Weight Efficient Power System for an Electrified Turbofan Through Gearbox Design and Control

Electrified Aircraft Propulsion (EAP) concepts could enable various benefits through a variety of use-cases. Benefits are sought in the form of reduced fuel burn and emissions. Many of these concepts involve the electrification of gas turbine engines. Electrification is accomplished through the integration of electric machines (EMs) with the engine shafts, providing the ability to inject and/or extract power as desired. Energy storage is also a common feature. An often-overlooked feature of the analysis is the means of integrating the EMs with the engine shafts. A trivial solution is to allow each shaft to have its own dedicated EM through independent geartrains. However, non-trivial mechanical integration solutions could provide benefits when considered in coordination with control logic to manage the operation of the propulsion system. Here, such a solution is considered and is shown to have the potential to reduce weight for a relevant conceptual electrified propulsion system. Weight saving benefits are demonstrated for various EAP use-cases. In particular, the mild hybrid application was shown to benefit from a power system weight reduction of 47% and an overall system weight reduction of 29%.

Hybrid Electric Propulsion↗

NASA NTRS2000

Process for Ignition of Gaseous Electrical Discharge Between Electrodes of a Hollow Cathode Assembly

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.

Patterson, Michael J.↗

NASA NTRS2002

Design and Manufacturing Processes of Long-Life Hollow Cathode Assemblies

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma at voltages of less than 20 Volts.

Michael J Patterson↗

NASA NTRS2004

Process for testing a xenon gas feed system of a hollow cathode assembly

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.

Patterson, Michael J.↗

NASA NTRS1993

The Earth Observing System AM Spacecraft - Thermal Control Subsystem

Mission requirements for the EOS-AM Spacecraft intended to monitor global changes of the entire earth system are considered. The spacecraft is based on an instrument set containing the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER), Clouds and Earth's Radiant Energy System (CERES), Multiangle Imaging Spectro-Radiometer (MISR), Moderate-Resolution Imaging Spectrometer (MODIS), and Measurements of Pollution in the Troposphere (MOPITT). Emphasis is placed on the design, analysis, development, and verification plans for the unique EOS-AM Thermal Control Subsystem (TCS) aimed at providing the required environments for all the onboard equipment in a densely packed layout. The TCS design maximizes the use of proven thermal design techniques and materials, in conjunction with a capillary pumped two-phase heat transport system for instrument thermal control.

Chalmers, D.↗

NASA NTRS2013

Flight Hardware Packaging Design for Stringent EMC Radiated Emission Requirements

This packaging design approach can help heritage hardware meet a flight project's stringent EMC radiated emissions requirement. The approach requires only minor modifications to a hardware's chassis and mainly concentrates on its connector interfaces. The solution is to raise the surface area where the connector is mounted by a few millimeters using a pedestal, and then wrapping with conductive tape from the cable backshell down to the surface-mounted connector. This design approach has been applied to JPL flight project subsystems. The EMC radiated emissions requirements for flight projects can vary from benign to mission critical. If the project's EMC requirements are stringent, the best approach to meet EMC requirements would be to design an EMC control program for the project early on and implement EMC design techniques starting with the circuit board layout. This is the ideal scenario for hardware that is built from scratch. Implementation of EMC radiated emissions mitigation techniques can mature as the design progresses, with minimal impact to the design cycle. The real challenge exists for hardware that is planned to be flown following a built-to-print approach, in which heritage hardware from a past project with a different set of requirements is expected to perform satisfactorily for a new project. With acceptance of heritage, the design would already be established (circuit board layout and components have already been pre-determined), and hence any radiated emissions mitigation techniques would only be applicable at the packaging level. The key is to take a heritage design with its known radiated emissions spectrum and repackage, or modify its chassis design so that it would have a better chance of meeting the new project s radiated emissions requirements.

Lortz, Charlene L.↗

NASA NTRS1965

Surfaces of controlled spectral absorptance

Calculation of film thickness in two and three layer systems required to achieve high absorption for solar radiation and low thermal emission

THERMAL EMISSION↗

NASA NTRS1993

Noise control in aeroacoustics; Proceedings of the 1993 National Conference on Noise Control Engineering, NOISE-CON 93, Williamsburg, VA, May 2-5, 1993

In the conference over 100 papers were presented in eight sessions: (1) Emission: Noise Sources; (2) Physical Phenomena; (3) Noise ControlElements; (4) Vibration and Shock: Generation, Transmission, Isolation, and Reduction; (5) Immission: Physical Aspects of Environmental Noise; (6) Immission: Effects of Noise; (7) Analysis; and (8) Requirements. In addition, the distinguished lecture series included presentations on the High Speed Civil Transport and on research from the United Kingdom on aircraft noise effects.

Hubbard, Harvey H.↗

NASA NTRS2004

Portable Integrated Wireless Device Threat Assessment to Aircraft Radio Systems

An assessment was conducted on multiple wireless local area network (WLAN) devices using the three wireless standards for spurious radiated emissions to determine their threat to aircraft radio navigation systems. The measurement process, data and analysis are provided for devices tested using IEEE 802.11a, IEEE 802.11b, and Bluetooth as well as data from portable laptops/tablet PCs and PDAs (grouping known as PEDs). A comparison was made between wireless LAN devices and portable electronic devices. Spurious radiated emissions were investigated in the radio frequency bands for the following aircraft systems: Instrument Landing System Localizer and Glideslope, Very High Frequency (VHF) Communication, VHF Omnidirectional Range, Traffic Collision Avoidance System, Air Traffic Control Radar Beacon System, Microwave Landing System and Global Positioning System. Since several of the contiguous navigation systems were grouped under one encompassing measurement frequency band, there were five measurement frequency bands where spurious radiated emissions data were collected for the PEDs and WLAN devices. The report also provides a comparison between emissions data and regulatory emission limit.

Salud, Maria Theresa P.↗

NASA NTRS2002

Method and apparatus for chemical and topographical microanalysis

A scanning probe microscope is combined with a laser induced breakdown spectrometer to provide spatially resolved chemical analysis of the surface correlated with the surface topography. Topographical analysis is achieved by scanning a sharp probe across the sample at constant distance from the surface. Chemical analysis is achieved by the means of laser induced breakdown spectroscopy by delivering pulsed laser radiation to the sample surface through the same sharp probe, and consequent collection and analysis of emission spectra from plasma generated on the sample by the laser radiation. The method comprises performing microtopographical analysis of the sample with a scanning probe, selecting a scanned topological site on the sample, generating a plasma plume at the selected scanned topological site, and measuring a spectrum of optical emission from the plasma at the selected scanned topological site. The apparatus comprises a scanning probe, a pulsed laser optically coupled to the probe, an optical spectrometer, and a controller coupled to the scanner, laser and spectrometer for controlling the operation of the scanner, laser and spectrometer. The probe and scanner are used for topographical profiling the sample. The probe is also used for laser radiation delivery to the sample for generating a plasma plume from the sample. Optical emission from the plasma plume is collected and delivered to the optical spectrometer so that analysis of emission spectrum by the optical spectrometer allows for identification of chemical composition of the sample at user selected sites.

Kossakovski, Dmitri A.↗

NASA NTRS1976

Development of EPA aircraft piston engine emission standards

Piston engine light aircraft are significant sources of carbon monoxide in the vicinity of high activity general aviation airports. Substantial reductions in carbon monoxide were achieved by fuel mixture leaning using improved fuel management systems. The air quality impact of the hydrocarbon and oxides of nitrogen emissions from piston engine light aircraft were insufficient to justify the design constraints being confronted in present control system developments.

Houtman, W.↗

NASA NTRS1977

Aircraft Engine Emissions

A conference on a aircraft engine emissions was held to present the results of recent and current work. Such diverse areas as components, controls, energy efficient engine designs, and noise and pollution reduction are discussed.

Source record↗

NASA NTRS1982

Combustor development for automotive gas turbines

The development of a combustion system for the AGT 100 automotive gas turbine engine is described. A maximum turbine inlet temperature of 1288 C is reached during the regenerative cycle, and air up to 1024 C is supplied to the combustor inlet. A premix/prevaporization ceramic combustor employing variable geometry to control burning zone temperature was developed and tested. Tests on both metal and ceramic combustors showed that emissions were a function of burner inlet temperature (BIT). At 999 C BIT, NO(x) emissions were two orders of magnitude below program goals, and at the same temperature but at a different variable geometry position, the CO was 30 times below program goal. Tests to evaluate the durability of the ceramic materials showed no failures during steady-state operation; however, some cracks developed in the dome during extended transient operation.

Ross, P. T.↗