Search NASA⌕ Search

SEARCH · Search NASA

Results for “ENGINES - FUEL INJECTION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Investigation of long-term light stability of negative charge injected into oxide-nitride-oxide passivation stack of crystalline silicon solar cells

A negatively charged oxide-nitride-oxide stack for field-effect passivation of crystalline silicon solar cells is discussed. The negative charge was injected into the stack by a plasma charge injection technology. Charge stability was studied by exposing samples to AM1.5 simulation visible light and full-spectrum light at temperatures ranging from 55 to 78 °C for up to 300 h. Charge injection and loss were quantified based on shifts in the flatband voltage of capacitance–voltage curves measured with a mercury probe. The most probable mechanism of charge loss was found to be diffusion of negative charged hydrogen atoms through nitride and bottom oxide. The optimum recipe for each layer of the stack was investigated to minimize the loss of injected charge. The flatband voltage decay of the optimized stack was found to fit a power-law trend, suggesting the dispersive transport of hydrogen atoms with a dispersion parameter of ~0.06–0.07. The optimized stack is projected to maintain a negative charge density of about 3.6 × 10 12 cm –2 or more after 25 years of field operation in an environment such as Arizona, which would be sufficient for field-effect passivation under one-sun illumination. Furthermore, the high stability of the negative injected charge makes the plasma charging technology a safer and lower cost alternative to Al 2 O 3 -passivation technology commonly used to passivate p-type surfaces.

14 SOLAR ENERGY↗
DOE OSTI2020

Use of Commercial Off-The-Shelf Parts with 3-D Printed Connectors for Powered Air Purifying Respirators

This report presents preliminary results from the performance evaluation of a powered air purifying respirator (PAPR) assembled from commercial off-the-shelf (COTS) parts. Cost is a major limiting factor to PAPR adoption in healthcare. Moreover, the lack of standardization for filters and batteries poses a challenge for clinics and hospitals. Rapid prototyping of connectors, both mechanical and electrical, offers a possible solution in addressing both issues. We used 3-D printed connectors to assemble COTS components into a prototype PAPR. Large-scale manufacturing of 3-D printed connectors may be accomplished by converting the computer-aided design (CAD) drawings to pressure-injection molds.

42 ENGINEERING↗
DOE OSTI2022

Synchrophasors-based Master State Awareness Estimator for Cybersecurity in Power Grid: Testbed Implementation & Field Demonstration

The integration of distributed energy resources(DERs) and expansion of complex network in the distribution grid requires an advanced distributed state estimator to monitor the grid health at micro-level. The distribution state estimator will improve the situational awareness and resiliency of distributed power system. This paper proposes a synchrophasors-based master state awareness (MSA) estimator to enhance the cybersecurity in distribution grid by providing a real-time estimation of system operating states to control center operators. In this paper, the proposed MSA estimator utilizes only phasor measurements, bus magnitudes and angles, from phasor measurement units (PMUs),deployed in local substations, to estimate the system states and also detects data integrity attacks, such as load tripping attack that disconnects the load. To validate the proof of concept, we implement the proposed methodology in cyber-physical testbed environment at the Idaho National Laboratory (INL) Electric Grid Security Testbed. Further, to address the “valley of death” and support technology commercialization, field demonstration is also performed at the Critical Infrastructure Test Range Complex(CITRC) at the INL. Our experimental results reveal a promising performance in detecting load tripping attack and providing an accurate situational awareness through an alert visualization dashboard in real-time

42 ENGINEERING↗
DOE OSTI2026

Modeling supercritical CO 2 flow and mineralization in reactive host rocks with PFLOTRAN v7.0

Understanding the flow and reactivity of CO 2 injected into geological reservoirs is important for many subsurface applications including secure geologic carbon storage (GCS), critical mineral extraction, enhanced geothermal systems (EGS), and enhanced oil recovery (EOR). Traditionally, subsurface CO 2 injection for GCS applications has focused on geologic formations with favorable subsurface configurations for CO 2 migration and trapping through non-reactive mechanisms such as structural, solubility, and petrophysical trapping. Recently, CO 2 -reactive rocks such as mafic and ultramafic basalts have been investigated for their potential to react with injected CO 2 in situ to simultaneously dissolve host rock minerals and mineralize CO 2 as carbonates. Engineering rapid CO 2 mineralization in the subsurface is attractive because of the increased density of stored CO 2 , the additional safety factors associated with solidification, and the potential to extract valuable critical minerals. Here we present recent developments in the parallel flow and reactive transport simulator PFLOTRAN to model coupled CO 2 -brine flow and reactive transport for a wide range of injection and production applications involving reactive CO 2 -brine systems. These developments are based on the well established and trusted CO 2 flow capabilities in the STOMP-CO 2 simulator. New capabilities added to PFLOTRAN include new CO 2 -brine equations of state with optional thermal coupling, several new constitutive relationships like capillary pressure smoothing and scanning path hysteresis, a fully implicit well model, and native linkage with PFLOTRAN's well-established reactive transport libraries. A series of benchmarks between PFLOTRAN and STOMP-CO 2 verify the newly developed CO 2 -brine flow capabilities. Demonstrations of coupled CO 2 -brine flow modeling and reactive transport show how CO 2 mineralization can be engineered in reactive host rocks. Finally, an example use case involving copper leaching by CO 2 and critical mineral extraction is presented to showcase the strengths of this new implementation. Several limitations still remain, including limited availability of field data to parameterize models. Future work should constrain the evolution of mineral surface area during mineralization and the temperature and/or pH dependence of geochemical reactions for specific systems of interest.

Critical Minerals↗
DOE OSTI2022

A review on nearly isothermal compression technology

Compressors can be described as the heart of a vapor compression refrigeration system, circulating the working fluid in the system. Significant benefits can be gained from improving its efficiency since energy consumption is responsible for almost the entire system's power input. An effort has been made to achieve isothermal compression through liquid refrigerant injection or inter-stage cooling in refrigeration systems. In recent years, much effort has been invested into isothermal compression technology for air compressors or compressed air energy storage systems with the rise of renewable energy. Here, this work has explored the advancements made in this area and categorized them to discuss the benefits, limitations, and tradeoffs. Evidently, increasing heat transfer area is a significant aid in improving heat transfer, resulting in better isothermal compression. However, liquid pistons open more avenues for this to be pursued, and therefore, are limited to air compression applications. In addition, water injection proved to be the most effective among the methods. Finally, there is a need for more experimental research on refrigeration applications and the field is still in its infancy.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Immunity Study: Port Impedance Measurement of PMU and PCI testing under EMP

With the increased requirements of real-time grid monitoring, disturbance location, and situation awareness, Phasor Measurement Units (PMUs) have become more critical for the Wide Area Measurement System (WAMS). However, the vulnerability of PMUs has not been well studied, especially under electromagnetic pulse (EMP) scenarios. The stable operation of the power system will be affected directly once EMP damages them. Therefore, studying their immunity to EMP events is urgent and necessary. In this paper, the effective impedance measurement scheme and pulsed current injection (PCI) testing are proposed for the port impedance measurement and immunity levels of PMUs. The equivalent non-uniform transmission line model is established to eliminate the impact of the fixture in the de-embedding process. Then, the circuit of the pulsed current generator is set to generate a damping sinusoid, and the double exponential wave is applied to the port. Finally, using measured impedance as a generator load, the voltage and current responses of different ports are calculated in the PCI testing simulation. In conclusion, results reveal the characteristics of port impedance, waveforms of voltage and current, and distribution of accumulative energy. The relation between port impedance and the waveforms is discussed.

42 ENGINEERING↗
DOE OSTI2023

Radiation Damage and Mitigation by Minority Carrier Injection in InAsSb/AlAsSb Heterojunction Barrier Mid-Wave Infrared Detector

Here, the effects of gamma and proton irradiation, and of forward bias minority carrier injection, on photo-response were investigated for InAsSb/AlAsSb pBn mid-wave infrared (MWIR) detectors with an engineered majority-carrier barrier. Room-temperature gamma irradiation had an insignificant effect on 77 K photo-response. Gamma irradiation at 77 K detector temperature, however, decreased in situ photo-response by 19% after a cumulative dose of ~ 500 krad(Si). Subsequent forward bias minority carrier injection had no effect on photo-response. The 77 K detectors irradiated with 30 MeV protons up to 2 Mrad(Si) had photo-response degraded by up to 70%, but here forward bias minority carrier (hole) injection caused up to 12% recovery that persisted more than 30 min. These results suggest a mitigation strategy for maintaining the photo-response of similar detectors in radiation environments that cause displacement damage defects.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Planarization of p -GaN surfaces on MOCVD grown V-defect engineered GaN-based LEDs

The large polarization barriers between the quantum wells and quantum barriers in long-wavelength GaN-based light-emitting diodes (LEDs) inhibit their performance by requiring excess driving voltages to reach standard operating current densities. Lateral injection of carriers directly into quantum wells is required to circumvent this issue. V-defects are naturally occurring inverted hexagonal defects with semipolar {$10\bar{1}1$}-plane sidewalls generated on surface depressions from threading dislocations. LEDs engineered to intentionally generate V-defects below the active region of the LED can achieve lateral carrier injection through the V-defect sidewalls and have already been able to demonstrate world record wall-plug efficiencies for LEDs in the green-red wavelengths. V-defects can be enlarged during kinetically limited growth where the growth rate of the c-plane GaN is faster than that of their sidewalls, leaving them unfilled. We report on the metal organic chemical vapor deposition growth conditions required to fill in V-defects with p-GaN during epitaxial growth of the LED post the active region. Circular transmission length measurements of Pd/Au contacts processed on p-GaN surfaces with various amounts of unfilled V-defects showed no significant difference in their sheet resistance and specific contact resistance. J–V measurements of LEDs grown with varying unfilled V-defect densities showed no significant difference in the forward bias regime. However, in the reverse bias regime, catastrophic breakdown occurred at markedly lower voltages for samples with larger unfilled V-defect densities. This suggests that unfilled V-defects may act as hotspots for device failure, and planarizing LED surfaces may help prevent early degradation of LED devices.

Chemical vapor deposition↗
DOE OSTI2024

Containment strategy for subsurface H 2 storage based on time-dependent soft solids

Here, we propose an innovative containment strategy based on time-dependent soft solids, namely 2 wt% Laponite suspensions, to reinforce natural subsurface seals and engineer flow barriers, with an eye toward making H 2 subsurface storage scalable and geographically agnostic. This suspension can be injected at its initial low viscosity and elasticity into a porous medium, allowing for easy pumping and targeted delivery. Once inside the target zone, it matures into a soft solid with much higher viscosity and elasticity, acting as a potential flow barrier. We discuss the rheological properties of the suspensions and demonstrate that hydrogen does not adversely affect their microstructure, but rather increases the suspensions’ viscosity and elasticity. Moreover, the suspensions enhance the rock samples’ compressive strength, while hydrogen exposure increases their stiffness and ductility. The ability of rock samples saturated with the suspensions to contain higher injected gas pressures is enhanced by aging at higher temperatures.

08 HYDROGEN↗
DOE OSTI2021

Design, synthesis, and characterization of vinyl-addition polynorbornenes with tunable thermal properties

Unfunctionalized vinyl-addition polynorbornene (VAPNB) possesses many outstanding properties such as high thermal, chemical, and oxidative stability. These features make VAPNB a promising candidate for many engineering applications. However, VAPNB has a small service window between its glass transition temperature (T g ) and decomposition temperature (T d ), and it cannot be readily processed in a melt state. In this work, we demonstrate that the service window of VAPNBs can be tailored through the use of norbornene monomers bearing alkyl, aryl, and aryl ether substituents. The vinyl addition homopolymerization and copolymerization of these functionalized norbornyl-based monomers yielded VAPNBs with high T' g s (>150 °C) and large service windows (T d –T g > 100 °C), which are comparable to other commercial engineering thermoplastics. To further establish the feasibility of melt processing, a functionalized VAPNB material with T g = 209 °C and a service window of 170 °C was successfully extruded and molded into bars. Subsequent characterization of the bars by dynamic mechanical analysis (DMA), nuclear magnetic resonance spectroscopy (NMR), and gel permeation chromatography (GPC) revealed only minor signs of polymer degradation. Furthermore, these studies suggest that substituted VAPNBs could be developed into a new class of engineering thermoplastics that is compatible with workhorse melt processing techniques such as extrusion and injection molding, as well as emerging techniques such as extrusion-based 3D printing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

maranasgroup/uncFBA

In the repository are example scripts that perform uncertainty injection and propagation to flux balance analysis with outputs for a small sample size (for demonstration purpose only). For proper analysis, user should download the scripts and run for a large sample size (e.g., 10,000 samples). If you use the scripts, please cite the following Metabolic Engineering article: “Quantifying the propagation of parametric uncertainty on flux balance analysis” (https://doi.org/10.1016/j.ymben.2021.10.012) There are two subdirectories: /uncFBA/uncBiom: injection of normally distributed noise to biomass precursor coeffcients and ATP maintenance (growth-associated ATP maintenance (GAM) and non-growth associated ATP maintenance (NGAM)) /uncFBA/uncRHS: departure from steady-state by adding noise drawn from normal distribution to the RHS terms of mass balance constraints

Dinh, Hoang↗
DOE OSTI2021

Binary and Ternary Colloidal Cu–Sn–Te Nanocrystals for Thermoelectric Thin Films

Recent advances in copper chalcogenide-based nanocrystals (NCs), copper sulfide, and copper selenide derived nanostructures, have drawn considerable attention. However, reports of crystal phase and shape engineering of binary or ternary copper telluride NCs remain rare. Here, a colloidal hot-injection approach for producing binary copper/tin telluride, and ternary copper tin telluride NCs with controllable compositions, crystal structures, and morphologies is reported. Here, the crystal phase and growth behavior of these tellurides are systematically studied from both experimental and theoretical perspectives.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Basin Management of Geologic CO2 Storage: Effect of Well Spacing on CO2 Plume and Pressure Interference

This is the conference paper accompanying an oral presentation made at the Society of Petroleum Engineers (SPE) Western Regional Meeting (WRM) held in Bakersfield, California, April 26–28, 2022. The paper provides the results of a basin-scale CO2 storage modeling project investigating subsurface pressure interference among CO2 injection wells located in proximity to each other.

Wijaya, Nur↗
DOE OSTI2023

Anomaly Detection in Power System State Estimation: Review and New Directions

Foundational and state-of-the-art anomaly-detection methods through power system state estimation are reviewed. Traditional components for bad data detection, such as chi-square testing, residual-based methods, and hypothesis testing, are discussed to explain the motivations for recent anomaly-detection methods given the increasing complexity of power grids, energy management systems, and cyber-threats. In particular, state estimation anomaly detection based on data-driven quickest-change detection and artificial intelligence are discussed, and directions for research are suggested with particular emphasis on considerations of the future smart grid.

42 ENGINEERING↗
DOE OSTI2022

Use of Multiple Tracer Gases to Quantify Vane Trailing Edge Flow Into Turbine Rim Seals

Abstract Overlapping features are commonly used as rim seals between stationary and rotating components in a turbine stage. These rim seals are used to prevent main gas path ingestion to the wheelspace cavity, which reduces the lifespan of critical engine components such as the turbine disk. In addition to the overlapping features, purge flow, diverted from the compressor, is injected into the rim cavity to act as an airflow sealing mechanism. Previous research identified that in addition to the purge flow in the rim cavity, cooling flow from the vane trailing edge (VTE) is ingested into the rim seal cavity carrying the potential to cool components in the wheelspace. These previous findings, however, were not able to distinctly separate purge from VTE cooling flows, which is the contribution of this paper based on uniquely using two different tracer gases. A one-stage test turbine operating at engine-relevant conditions and consisting of real engine hardware was used to validate and quantify the ingestion of the VTE flow by independently seeding the purge and VTE flows with two different tracer gases. Experimental results show the presence of VTE flow in the rim seal throughout all purge flowrates evaluated. Circumferential variation of VTE flow was also studied both experimentally and computationally using a computational fluid dynamics model. Results showed that ingested VTE flow can reduce the detrimental effect of hot gas ingestion particularly at higher purge flowrates.

Engineering↗
DOE OSTI2023

Assessing the vulnerability of solar inverters to EMPs: Port testing, PCI modeling, and protection strategies

Renewable energy sources are becoming an ever-larger contributor to the power grid. These renewable energy sources depend upon the power electronic devices, specifically inverters, being essential for connecting Photovoltaic (PV) generation to the grid. However, the Electromagnetic Pulses (EMPs) caused by the high-altitude nuclear explosions can generate fast broad-band pulses with nanosecond rise time, potentially causing damage or destruction to electronic components. To assess the vulnerability of PV inverters to high-altitude EMPs, the port testing and Pulsed Current Injection (PCI) modeling schemes are proposed based on the port impedance analysis. Wide-band frequency measurements are achieved by fusing impedance results from three vector network analyzers. Then, a PCI model is used to simulate the induced response to EMP, with two typical immunity levels of EC5 and EC8 tested. Here, the experiment successfully excites the induced voltage and current under EMP, where the voltage and current can reach 1500V/40A and 8000V/150Aunder EC5 andEC8, respectively. The port vulnerability analysis results demonstrate that only some ports can survive under EC5. To defend against the impact of EMP, three protection strategies are discussed.

42 ENGINEERING↗