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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Capturing the Impact of Fuel Octane Number on Modern Gasoline Vehicles with Octane Indices

The need for high efficiency automotive engines has led to more complex air handling and fuel injection systems, higher compression ratios, more advanced combustion and aftertreatment systems, and the use of fuels with higher octane ratings. Higher octane number fuels have a lower propensity to knock. This work studies the influence of changing fuel octane rating on two modern production gasoline vehicles, one with a naturally aspirated, port injected engine and the other with a turbocharged, direct injected engine, using fuels with four different octane number grades (with 85, 87, 91, and 93 anti-knock indices) and operated over a variety of driving cycles and temperature conditions. Unlike previous studies, this effort develops and demonstrates a methodology that isolates fuel effects on fuel consumption and provides a clear view of the octane impact on existing vehicles. While fuel octane rating can also impact factors such as the allowable compression ratio and gear shifting strategies, this study examines fuel consumption changes that are solely attributable to octane rating on production vehicles. The developed approach uses results from drive cycle as well as steady-state tests along with response surface modeling to predict the engine combustion phasing and changes in efficiency for each fuel relative to the baseline 87 anti-knock index (AKI) fuel. The methodology is then used to capture the role of fuel octane rating on powertrain efficiency over Environmental Protection Agency (EPA) certification drive cycles and demonstrate the variation of that impact as a function of powertrain output power. Based on the vehicles and fuels tested in this study, the metrics indicate that the effects of octane on efficiency are limited to a portion of the operating modes represented in the driving cycles used for vehicle certification. In addition, an octane potential benefit index (OPBI) suggests that the vehicle with the turbocharged, direct injected engine has a greater potential to benefit from higher octane number fuel compared to the naturally aspirated, port injected engine and proposes a way to quantify this impact for production vehicles.

Jehlik, Forrest↗
DOE OSTI2018

Large-eddy Simulations of Spray Variability Effects on Flow Variability in a Direct-injection Spark-ignition Engine Under Non-combusting Operating Conditions

Large-eddy Simulations (LES) have been carried out to investigate spray variability and its effect on cycle-to-cycle flow variability in a direct-injection spark-ignition (DISI) engine under non-reacting conditions. Initial simulations were performed of an injector in a constant volume spray chamber to validate the simulation spray set-up. Comparisons showed good agreement in global spray measures such as the penetration. Local mixing data and shot-to-shot variability were also compared using Rayleigh-scattering images and probability contours. The simulations were found to reasonably match the local mixing data and shot-to-shot variability using a random-seed perturbation methodology. After validation, the same spray set-up with only minor changes was used to simulate the same injector in an optically accessible DISI engine. Particle Image Velocimetry (PIV) measurements were used to quantify the flow velocity in a horizontal plane intersecting the spark plug gap. The engine was operated in a skip-fired operating mode and comparisons focused on cycles that included fuel injection, but no spark event and therefore no combustion. 105 total LES engine cycles were simulated using a parallel cycle simulation approach and 3 different perturbation methods in an attempt to isolate the effects of shot-to-shot spray variability and the initial turbulent flow field as well as their interaction effects on overall engine CCVs. The experimental mean and standard deviations were reasonably well matched by the simulations, though quantitative comparisons near the injection event during the intake stroke were difficult due to the high uncertainty in the PIV measurements at these crank angles. The 3 simulation perturbation methods resulted in very similar results, though further analysis found the current parallel cycle approach may be limiting the ability of the simulations to isolate the spray and flow effects.

Cycle-to-cycle Variability↗
DOE OSTI2020

Detection of Polar Compounds Condensed on Particulate Matter Using Capillary Electrophoresis-Mass Spectrometry

A new analytical method to aid in the understanding of the organic carbon (OC) phase of particulate matter (PM) from advanced compression ignition (ACI) operating modes, is presented. The presence of NO2 and unburned fuel aromatics in ACI emissions, and the low exhaust temperatures that result from this low temperature combustion strategy, provide the right conditions for the formation of carboxylic acids and nitroaromatic compounds. These polar compounds contribute to OC in the PM and are not typically measured using nonpolar solvent extraction methods such as the soluble organic fraction (SOF) method. The new extraction and detection method employs capillary electrophoresis with electrospray ionization mass spectrometry (CE-ESI MS) and was specifically developed to determine polar organic compounds in the ACI PM emissions. The new method identified both nitrophenols and aromatic carboxylic acids in the ACI PM. The ACI air-fuel stratification mode and NOx emissions were found to correlate with the presence and amount of the individual polar species identified.

Lewis Sr, Samuel↗
DOE OSTI2019

Organic peroxy radical chemistry in oxidation flow reactors and environmental chambers and their atmospheric relevance

Abstract. Oxidation flow reactors (OFRs) are a promising complement to environmental chambers for investigating atmospheric oxidation processes and secondary aerosol formation. However, questions have been raised about how representative the chemistry within OFRs is of that in the troposphere. We investigate the fates of organic peroxy radicals (RO 2 ), which play a central role in atmospheric organic chemistry, in OFRs and environmental chambers by chemical kinetic modeling and compare to a variety of ambient conditions to help define a range of atmospherically relevant OFR operating conditions. For most types of RO 2 , their bimolecular fates in OFRs are mainly RO 2 + HO 2 and RO 2 + NO, similar to chambers and atmospheric studies. For substituted primary RO 2 and acyl RO 2 , RO 2 + RO 2 can make a significant contribution to the fate of RO 2 in OFRs, chambers and the atmosphere, but RO 2 + RO 2 in OFRs is in general somewhat less important than in the atmosphere. At high NO, RO 2 + NO dominates RO 2 fate in OFRs, as in the atmosphere. At a high UV lamp setting in OFRs, RO 2 + OH can be a major RO 2 fate and RO 2 isomerization can be negligible for common multifunctional RO 2 , both of which deviate from common atmospheric conditions. In the OFR254 operation mode (for which OH is generated only from the photolysis of added O 3 ), we cannot identify any conditions that can simultaneously avoid significant organic photolysis at 254 nm and lead to RO 2 lifetimes long enough ( ∼ 10 s) to allow atmospherically relevant RO 2 isomerization. In the OFR185 mode (for which OH is generated from reactions initiated by 185 nm photons), high relative humidity, low UV intensity and low precursor concentrations are recommended for the atmospherically relevant gas-phase chemistry of both stable species and RO 2 . These conditions ensure minor or negligible RO 2 + OH and a relative importance of RO 2 isomerization in RO 2 fate in OFRs within ∼ × 2 of that in the atmosphere. Under these conditions, the photochemical age within OFR185 systems can reach a few equivalent days at most, encompassing the typical ages for maximum secondary organic aerosol (SOA) production. A small increase in OFR temperature may allow the relative importance of RO 2 isomerization to approach the ambient values. To study the heterogeneous oxidation of SOA formed under atmospherically relevant OFR conditions, a different UV source with higher intensity is needed after the SOA formation stage, which can be done with another reactor in series. Finally, we recommend evaluating the atmospheric relevance of RO 2 chemistry by always reporting measured and/or estimated OH, HO 2 , NO, NO 2 and OH reactivity (or at least precursor composition and concentration) in all chamber and flow reactor experiments. An easy-to-use RO 2 fate estimator program is included with this paper to facilitate the investigation of this topic in future studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Calibration of the 2007–2017 record of Atmospheric Radiation Measurements cloud radar observations using CloudSat

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurements (ARM) facility has been at the forefront of millimeter-wavelength radar development and operations since the late 1990s. The operational performance of the ARM cloud radar network is very high; however, the calibration of the historical record is not well established. Here, a well-characterized spaceborne 94 GHz cloud profiling radar (CloudSat) is used to characterize the calibration of the ARM cloud radars. The calibration extends from 2007 to 2017 and includes both fixed and mobile deployments. Collectively, over 43 years of ARM profiling cloud radar observations are compared to CloudSat and the calibration offsets are reported as a function of time using a sliding window of 6 months. The study also provides the calibration offsets for each operating mode of the ARM cloud radars. Overall, significant calibration offsets are found that exceed the uncertainty of the technique (1–2 dB). The findings of this study are critical to past, ongoing, and planned studies of cloud and precipitation and should assist the DOE ARM to build a legacy decadal ground-based cloud radar dataset for global climate model validation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

915rwpprecipcor

Radar Wind Profiler (RWP) has operational modes: short duration high resolution (referred to as 'high' or 'high mode') and long duration low resolution (referred to as 'low' or 'low mode'). The motivation for this is to create a VAP that quality controls (noise, sig echo filtering), merges, co-grids, and performs initial analyses on these RWP modes. This is done to streamline downstream VAP development on the RWP, as well as enable incorporation of echo properties into the ARSCL chain. The proposed VAP will use the RWPPRECIP b0/b1 level data stream as input. Additional consideration for the incorporation of other ARM data streams to improve this VAP was performed, but not included at this time.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Predictions of core plasma performance for the SPARC tokamak

SPARC is designed to be a high-field, medium-size tokamak aimed at achieving net energy gain with Ion Cyclotron Range-of-Frequencies (ICRF) as its primary auxiliary heating mechanism. Empirical predictions with conservative physics indicate that SPARC baseline plasmas would reach Q~11, well above its mission objective of Q>2. To build confidence that SPARC will be successful, physics-based integrated modeling has also been performed. The TRANSP code coupled with the theory-based TGLF turbulence model and EPED predictions for pedestal stability find that Q~9 is attainable in standard H-mode operation and confirms Q>2 operation is feasible even with adverse assumptions. In this analysis, ion cyclotron waves are simulated with the full wave TORIC code and alpha heating is modeled with the Monte-Carlo fast ion NUBEAM module. Detailed analysis of expected turbulence regimes with linear and nonlinear CGYRO simulations is also presented, demonstrating that profile predictions with the TGLF reduced model are in reasonable agreement.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1967

Solid-state time-to-pulse-height converter developed

Solid-state circuit produces an output pulse with an amplitude directly proportional to the time interval between two input pulses. It uses selected circuit options to achieve variable mode operation and a tunnel diode controls the charging time of a capacitor in proportion to the time interval being measured.

Lynch, R. J.↗