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The purpose of this CRADA was for LLNL to provide the engineering, design, and component specification of the instrumentation and controls of Elmore Associate's multipoint ignition scheme for liquid gun propellant applications.
This report addresses the suitability of hydrocarbon and oxygenate functional groups for use as a diesel-like fuel blending component in an advanced, mixing-controlled, compression ignition combustion engine. The functional groups are chosen from those that could be derived from a biomass feedstock, and represent a full range of chemistries. This first systematic analysis of functional groups will be of value to all who are pursuing new bio-blendstocks for diesel-like fuels.
Ducted fuel injection (DFI) is a technique for lowering emissions (primarily soot emissions) from high-efficiency compression-ignition (CI) engines, as well as other devices employing the direct injection of fuel into a combustion chamber. The DFI concept was inspired by the cleaner burn that is created by premixing fuel and air in the tube of a Bunsen burner, which was created to reduce soot production common in burners of the period as stated by Kohn [American Chemical Society, 1949].
It is not known whether pristine (i.e. mechanically and thermally undamaged) PBX 9501 can transition from a deflagration to a detonation in realistic scenarios, with relevant charge masses and inertial and mechanical confinement. In order to place bounds on the behavior, a series of experiments was conducted in which a spherical PBX 9501 charge is center-ignited using a fiber-delivered infrared laser pulse. Charge diameter was varied from 1.5 in ch to 10 inch. Experiments were conducted in a “bare” (unconfined) configuration, and a confined configuration with 4 mm-thick stainless-steel hemispherical shells bolted together. In all eight experiments, the reaction exhibited a relatively benign pressure burst; no transition to detonation (DDT) was observed. Most of the explosive was unconsumed and recovered post-test. Confined tests demonstrated slightly greater violence than unconfined tests, as anticipated.
Eight bio-blendstock fuel candidates for boosted spark ignited engines were evaluated for their susceptibility to corrode infrastructure metals. These candidates included five alcohols (methanol, ethanol, isobutanol, n-propanol, and isopropanol), diisobutylene, mixed furans, and aromatics. Methanol was also added to the list for comparison. These molecules are not corrosive to metals since they cannot dissociate into ions and anions. However, the addition of contaminants and a separate water phase may facilitate corrosion due to phenomena associated with the formation of ions and anions (from key contaminants), differential aeration cell (due to dissolved oxygen), and microbial-induced corrosion. A literature review was conducted to determine the influence of these phenomena on corrosion for the nine fuel candidates. In addition, the oxygen solubility of each fuel type was determined to ascertain their relative influence on forming and enhancing a differential aeration cell. Of the fuel candidates, only the alcohols are water soluble, and therefore have an opportunity to cause corrosion. However, differential aeration cells, by themselves have not been shown to contribute to corrosion. Other factors, such as galvanic coupling and/or crevice regions are necessary to promote corrosion in laboratory conditions. However, differential aeration as a corrosion mechanism has not been established in the field. Likewise, microbial-induced corrosion is another known corrosion pathway that has yet to be positively identified for blends of the fuel candidates with gasoline. In summary, corrosion is not anticipated with any of the bio-blendstock candidates with infrastructure metals.
The Graphical User Interface (GUI) systems for the Controls Systems on the National Ignition Facility (NIF) are legacy technology that eventually will be obsoleted and no longer supported by the vendor. Our mission is to migrate the existing GUI systems to present-day technology.
Reactivity-Controlled Compression Ignition (RCCI) is a promising new advanced, low temperature combustion mode that offers efficiencies equal to or greater than conventional diesel combustion, but significantly lower soot and NOx emissions. Additionally, RCCI has enhanced controllability over the combustion process compared to some of the other advanced combustion modes. Therefore, RCCI combustion has the potential to be of great benefit to the public by increasing the efficiency and reducing the harmful pollutant emissions from transportation. However, RCCI combustion achieves this favorable level of performance through the use of two distinct fuels (e.g., diesel and gasoline, diesel and natural gas, or diesel and ethanol). In a vehicle application, RCCI therefore requires two different fuel tanks and fuel injection systems, which presents a significant drawback to the commercialization RCCI. This project proposed a new concept to enable RCCI combustion from a single parent fuel stored onboard the vehicle in a single fuel tank. Specifically, the parent fuel would be stored in the fuel tank and one branch of the fuel system would deliver the parent fuel, unaltered, to the cylinder, while a second branch of the fuel system would route the parent fuel through a fuel reformer to chemically react the fuel into a gaseous fuel mixture, called “reformate”, that has different properties from the original parent fuel. In this way, there can be two fuels at the engine that have different properties, but only one parent fuel needs to be stored and refilled in the vehicle. This initial, exploratory investigation into the feasibility of this promising new concept included reacting three potential parent fuels (diesel, gasoline, and natural gas) in a fuel reformer and determining the composition of the gaseous reformate fuel that exited the fuel reformer. There are different types of reformation processes, but since this project was a proof-of-concept investigation into the potential of Single-Fuel RCCI and the combustion process in the cylinder, a catalytic partial oxidation (CPOX) reformation process was selected, which is more straightforward to perform and control, and would potentially be easier to implement in a vehicle application compared to other reformation processes. Once the three parent fuels were reformed to varying degrees and their reformate compositions were determined, their autoignition tendencies were experimentally determined by comparing advanced combustion results of the reformate mixtures with known reference fuels. This showed that diesel fuel and its reformate fuel mixture exhibited the largest reactivity separation, which is necessary to enable RCCI combustion in the cylinder. Using diesel fuel as the parent fuel, experimental testing was conducted to provide a better understanding of the operational considerations, benefits, and drawbacks of Single-Fuel RCCI with onboard fuel reformation. The experimental testing was accompanied by computational fluid dynamics and system-level modeling to help complement the experiments and further expand the understanding. The main conclusions are that Single-Fuel RCCI using diesel fuel as the direct injected, high reactivity fuel and diesel’s gaseous reformate mixture as the premixed, low reactivity fuel is viable. The efficiencies were equal to, or sometimes greater than, RCCI with conventional fuel pairs, and the emissions were comparable as well. A key consideration is that gaseous reformate fuel contains a large amount of diluents in the fuel which displace air entering the cylinder and act as EGR inside the cylinder. Additionally, the reactivity separation between diesel and its reformate fuel mixture is larger than diesel-gasoline, but less than diesel-natural gas, and the combustion process therefore responded in a manner that was between the two conventional fuel pairs. Finally, although achievable in the cylinder, there are practical drawbacks or other disadvantages of Single-Fuel RCCI with onboard fuel reformation. First, this project used a CPOX reformation process which is exothermic, meaning that a portion of the fuel’s energy was released in the reformer where it could not be converted into useful work. This constituted an efficiency penalty of the system of on the order of 10% or 4 percentage points. Future research should therefore focus on alternate reforming processes including steam-methane reforming or autothermal reforming where there might not be any energy released in the reformer, or there could even be an energy gain in the reformer (through an endothermic process with waste heat recovery). Practical drawbacks that exist, but were beyond the scope of this preliminary proof-of-concept research project, are the added cost of the fuel reformer, which is a catalyst made of precious metals, transient response of the system, and the lifetime of the fuel reformer.
Radiation hydrodynamics modeling of hohlraum experiments on the National Ignition Facility has shown a chronic overprediction of hohlraum performance compared to experiment. Depending on the particular experiment, up to several hundred kilojoules of laser energy must be artificially subtracted from the simulations in order to match experimentally measured quantities like the time of peak neutron production (bang time). Fine-scale hydrodynamic mixing of the high-Z hohlraum wall with the low-Z hohlraum gas, an effect omitted in current hohlraum simulations, has long been hypothesized as possible source of some of this degradation. A preliminary computational assessment using a spherical hohlraum model has been made. It shows that the wall-gas interface is both unstable during certain phases of the experiment and has the potential for turbulent mixing of the gas and wall material, depending on the hohlraum gas fill and pulse shape. The same simulations also indicate that mixing at this interface can delay the simulated bang time by up to 140 ps with high gas fills but appears negligible for low gas fills.
Targets for magnetically-assisted ignition require specialized hohlraums that are made from an electrically non-conductive material. Such special-material hohlraums allow external magnetic fields to uniformly soak through the hohlraum and into the capsule prior to the laser drive. These requirements necessitate the development of an entirely new class of ceramic or intermetallic hohlraums since, in all previous hohlraum designs, solid-state electronic transport properties were not of interest and, hence, were not investigated. In this project, we have demonstrated the feasibility of the deposition of thick (>30 microns) and electrically-resistive (>100 micro-Ohm cm) gold-tantalum-based coatings by magnetron sputtering.
Electron-mediated nuclear-plasma interactions (NPIs) have the potential to change nuclear reaction rates in high energy density plasma (HEDP) environments, such as those found in experiments at the National Ignition Facility (NIF), in astrophysical phenomenon, or in nuclear detonations, relative to conventional laboratory measurements on room-temperature targets. Two Discovery Science shots to detect these interactions at the NIF were conducted in January and September 2017 at the conclusion of a campaign to develop the indirect-drive exploding pusher experimental platform and diagnostics. These shots were designed to measure the differential population of a high-spin isomer of 133 Xe of an inplasma versus a control sample, where a non-zero differential would indicate a measurable influence of the plasma on 134 Xe(n,2n) reactions. Preliminary observations from these shots were consistent with a small NPI effect, but improved theoretical understanding coupled with refined data analysis were needed to definitively establish the discovery or lack thereof. Achieving both of these, a statistically-credible NPI was indeed observed at a level predicted by an adapted Monte Carlo gamma-cascade model, a significant lowering by of the isomerto- ground state activity ratio in 133 Xe.
The project objectives were to develop demonstrate a high-efficiency high-output natural gas diesel micro-pilot stoichiometric engine operating with diesel pilot contribution of less than 5% on a medium duty engine. The program’s outcomes achieve in a partnership between Michigan Technological University and Westport Power Inc. were very successful. The engine platform was a 6.7L I6 engine with a compression ratio of 15:1 and achieved 24 bar BMEP and 41% brake thermal efficiency at lambda. Simulation and modeling with an improved turbocharger and combustion chamber improvements demonstrated a clear path to 43% BTE. The operational stoichiometric range was from 5 to 24 bar with minimal throttling. Diesel contribution over the cycle was 4.6%. The results achieved in this program are well above the best in-class baseline natural gas spark ignition engines of 19.5 bar BMEP and 40% BTE.
The goal of this system is to provide a universal method of capturing and integrating campaign level target requirements for experiments at the National Ignition Facility (NIF) prior to establishing a baseline schedule. The expected outcome is a more resilient schedule able to accurately incorporate long lead target requirements.
More efficient engines enabled by better fuels derived from biomass could increase the fuel economy of the light duty (LD) fleet by 10% over current technology and planned developments. This report identifies top LD boosted spark ignition (BSI) biofuel candidates for further development and commercialization identified using a fuel property basis. The BSI merit function was used to evaluate the performance of candidate bio-blendstocks in improving engine efficiency. This report is aimed at biofuel researchers looking to better understand the efficiency implications of biofuels under development, as well as engine researchers who are interested in future biofuels with properties that enable more efficient engine design and operation.
This project is focused on developing advanced combustion strategies for mixing-controlled compression ignition (MCCI, i.e., diesel-cycle) engines that are synergistic with renewable and/or unconventional fuels in a manner that enhances domestic energy security, economic competitiveness, and environmental quality. During this reporting period, the two focus areas were ducted fuel injection (DFI) and surrogate diesel fuels.
Simulations of several of the end-irradiated cylindrical photoelectron driven cavity experiments (also known as B-Dot cavities) that were fielded during the July 1 through 2, 2020 shot series at the National Ignition Facility are presented in this report with comparisons to experimental measurements. All cavity B-Dots fielded on the second, third, fourth, fifth and seventh shots were simulated using coupled Integrated Tiger Series (ITS) Monte Carlo transport codes and the Electromagnetic Plasmas in Realistic Environments (EMPIRE) electromagnetic particle-in-cell code.
We present a simple method for determining the required level of dopant into the DT gas of a National Ignition Facility capsule, in order to ensure that the products from nuclear transmutation of the dopant will be detectable at the Radiochemical Analysis of Gaseous Samples facility.
This report details the measured x-ray characteristics radiating from laser targets on 7 shots at Lawrence Livermore National Laboratory's National Ignition Facility performed June 30 - July 2, 2020. Generally, the x-ray sources were designed to serve as meaningful drivers of a variety of Radiation Effects Sciences response experiments. Specifically, on these 7 shots, the measured x-ray output characteristics and the response experiments serve as a useful data set for validating performance and informing further development of Sandia National Laboratories' EMPIRE code. We present x-ray measurements and analyses relevant to simulating the System-Generated Electro Magnetic Pulse experiments that also occurred on these shots (described elsewhere). Sufficient detail is provided so that a motivated, but novice, x-ray source user could produce some of these analysis results from raw data on similar x-ray shots.
The ControlNet industrial communications protocol and modules used in the Industrial Control System (ICS) and Safety Interlock System (SIS) at the National Ignition Facility (NIF) are no longer necessary and the ICS and SIS would be better served by migrating the communications structure to use EtherNet/Industrial Protocol (IP) and EtherNet bridge modules instead. By the admission of the vendor of ControlNet hardware, Rockwell Automation, in literature by Bill Petro [1], “Moving forward, customers will be able to optimize their asset utilization better using EtherNet/IP protocol than with ControlNet.” The NIF is one of the key elements of the Inertial Confinement Fusion (ICF) program at Lawrence Livermore National Laboratory (LLNL), a federally funded research and development center (FFRDC). The NIF contains the systems and provides the operational capacity to perform ICF, high energy density (HED), and discovery science experiments utilizing 192 individual beamlines, a host of diagnostics, and all the industrial systems required to facilitate these beamlines and diagnostics. The industrial systems are governed by the ICS and SIS, with the ICS providing control and the SIS providing monitoring and permissives. Construction on the NIF began in 1997 and was certified complete in 2009 and, as a result, the ICS and SIS were developed during this time using the tools that were available then. This includes the communications structure and protocols for these systems, much of which was, and still is, ControlNet. ControlNet, particularly during the time that the ICS and SIS were being built, has several attractive features. ControlNet hardware is exclusive to Rockwell Automation, which was the automation hardware chosen for the ICS and SIS. One feature that could be considered an advantage or a disadvantage depending on the communication needs of the system is that ControlNet also utilizes no active network components, excluding repeaters which are not always necessary. According to the architect of the ICS system at the NIF, Gordon Lau, one of the most attractive features of the ControlNet protocol during development of the ICS and SIS was that it is deterministic, providing timing of data transfer that is executed exactly as it is defined by the developer.