Computational Aeroelastic Analysis of Ares Crew Launch Vehicle Bi-Modal Loading

A Reynolds averaged Navier-Stokes analysis, with and without dynamic aeroelastic effects, is presented for the Ares I-X launch vehicle at transonic Mach numbers and flight Reynolds numbers for two grid resolutions and two angles of attack. The purpose of the study is to quantify the force and moment increment imparted by the sudden transition from fully separated flow around the crew module - service module junction to that of the bi-modal flow state in which only part of the flow reattaches. The bi-modal flow phenomenon is of interest to the guidance, navigation and control community because it causes a discontinuous jump in forces and moments. Computations with a rigid structure at zero zero angle of attack indicate significant increases in normal force and pitching moment. Dynamic aeroelastic computations indicate the bi-modal flow state is insensitive to vehicle flexibility due to the resulting deflections imparting only very small changes in local angle of attack. At an angle of attack of 2.5deg, the magnitude of the pitching moment increment resulting from the bi-modal state nearly triples, while occurring at a slightly lower Mach number. Significant grid induced variations between the solutions indicate that further grid refinement is warranted

Assessment of Cavitation-Erosion Resistance of Potential Pump Impeller Materials for Mercury Service at the Spallation Neutron Source

Using a standard vibratory horn apparatus, the relative cavitation-erosion resistance of a number of cast alloys in mercury was evaluated to facilitate material selection decisions for Hg pumps. The performance of nine different alloys - in the as-cast condition as well as following a case-hardening treatment intended to increase surface hardness - was compared in terms of weight loss and surface profile development as a function of sonication time in Hg at ambient temperature. The results indicated that among several potentially suitable alloys, CD3MWCuN perhaps exhibited the best overall resistance to cavitation in both the as-cast and surface treated conditions while the cast irons examined were found unsuitable for service of this type. However, other factors, including cost, availability, and vendor schedules may influence a material selection among the suitable alloys for Hg pumps

Assessment of End-of-Life Behavior of the Surface Modification to Improve Cavitation-Erosion Resistance in the Mercury Target at the Spallation Neutron Source

The cavitation-erosion resistance of the Kolsterised{reg_sign} layer on annealed or cold-worked substrates of 316LN stainless steel has been examined in mercury using a vibratory horn technique and extended exposure periods intended to expose 'end-of-life' performance characteristics. The Kolsterised{reg_sign} layer tends to remain protective--as evidenced by modest steady-state weight loss and surface roughness increases, only isolated pitting, and limited wetting by mercury--until the protective layer has been thinned by general erosion to about 15-20 {micro}m. Prior to that amount of erosion, the cavitation-erosion resistance of both types of specimens appears defined by the properties of the protective layer. However, after thinning to such a degree, initial breakdown of the protective layer is characterized by increases in both the surface roughness and the number/depth of individual pits across the surface at a rate that is strongly dependent on the substrate condition, with annealed substrates significantly more prone to damage. However, even as the protective properties of the Kolsterised{reg_sign} layer decrease, both weight change and profile development as a function of sonication time suggest a gradual reversion to cavitation-erosion behavior similar to that of untreated substrates

Comparison of Cavitation-Erosion Resistance of Carburized and Carburized-Plus-Nitrided 316LN Stainless Steel in Mercury

Annealed type 316LN stainless steel in the (1) carburized and the (2) carburized plus nitrided conditions was evaluated for cavitation-erosion resistance in ambient temperature mercury using a vibratory horn method. The results indicated that, relative to the specimens receiving only the carburizing treatment, the specimens that received both surface treatments exhibited substantially greater weight loss, general thinning, and profile development as a function of sonication time - with all observed degradation limited to the nitrided layer. Further, the nitride layer was observed to be susceptible to extensive cracking (occasionally leading to spallation), but the cracking was never observed to penetrate into the carburized layer. These screening test results suggest there is no improvement in cavitation-erosion resistance associated with augmentation of the carburizing treatment with plasma nitriding

Evaluation of Cavitation-Erosion Resistance of 316LN Stainless Steel in Mercury Containing Metallic Solutes

Room temperature cavitation tests of vacuum annealed type 316LN stainless steel were performed in pure Hg and in Hg with various amounts of metallic solute to evaluate potential mitigation of erosion/wastage. Tests were performed using an ultrasonic vibratory horn with specimens attached at the tip. All of the solutes examined, which included 5 wt% In, 10 wt% In, 4.4 wt% Cd, 2 wt% Ga, and a mixture that included 1 wt% each of Pb, Sn, and Zn, were found to increase cavitation-erosion as measured by increased weight loss and/or surface profile development compared to exposures for the same conditions in pure Hg. Qualitatively, each solute appeared to increase the post-test wetting tenacity of the Hg solutions and render the Hg mixture susceptible to manipulation of droplet shape

NHI Component Technical Readiness Evaluation System

A decision process for evaluating the technical readiness or maturity of components (i.e., heat exchangers, chemical reactors, valves, etc.) for use by the U.S. DOE Nuclear Hydrogen Initiative is described. This system is used by the DOE NHI to assess individual components in relation to their readiness for pilot-scale and larger-scale deployment and to drive the research and development work needed to attain technical maturity. A description of the evaluation system is provided, and examples are given to illustrate how it is used to assist in component R&D decisions

Optimal Thinning of MCMC Output

The use of heuristics to assess the convergence and compress the output of Markov chain Monte Carlo can be sub-optimal in terms of the empirical approximations that are produced. Typically a number of the initial states are attributed to "burn in" and removed, whilst the remainder of the chain is "thinned" if compression is also required. In this paper we consider the problem of retrospectively selecting a subset of states, of fixed cardinality, from the sample path such that the approximation provided by their empirical distribution is close to optimal. A novel method is proposed, based on greedy minimisation of a kernel Stein discrepancy, that is suitable for problems where heavy compression is required. Theoretical results guarantee consistency of the method and its effectiveness is demonstrated in the challenging context of parameter inference for ordinary differential equations. Software is available in the Stein Thinning package in Python, R and MATLAB.Comment: To appear in the Journal of the Royal Statistical Society, Series B, 2021

Engine Materials Compatibility with Alternate Fuels

The compatibility of aluminum and aluminum alloys with synthetic fuel blends comprised of ethanol and reference fuel C (a 50/50 mix of toluene and iso-octane) was examined as a function of water content and temperature. Commercially pure wrought aluminum and several cast aluminum alloys were observed to be similarly susceptible to substantial corrosion in dry (< 50 ppm water) ethanol. Corrosion rates of all the aluminum materials examined were accelerated by increased temperature and ethanol content in the fuel mixture, but inhibited by increased water content. Pretreatments designed to stabilize passive films on aluminum increased the incubation time for onset of corrosion, suggesting film stability is a significant factor in the mechanism of corrosion

Computational Aeroelastic Analysis of the Ares Launch Vehicle During Ascent

This paper presents the static and dynamic computational aeroelastic (CAE) analyses of the Ares crew launch vehicle (CLV) during atmospheric ascent. The influence of launch vehicle flexibility on the static aerodynamic loading and integrated aerodynamic force and moment coefficients is discussed. The ultimate purpose of this analysis is to assess the aeroelastic stability of the launch vehicle along the ascent trajectory. A comparison of analysis results for several versions of the Ares CLV will be made. Flexible static and dynamic analyses based on rigid computational fluid dynamic (CFD) data are compared with a fully coupled aeroelastic time marching CFD analysis of the launch vehicle

Analysis of Underground Storage Tanks System Materials to Increased Leak Potential Associated with E15 Fuel

The Energy Independence and Security Act (EISA) of 2007 was enacted by Congress to move the nation toward increased energy independence by increasing the production of renewable fuels to meet its transportation energy needs. The law establishes a new renewable fuel standard (RFS) that requires the nation to use 36 billion gallons annually (2.3 million barrels per day) of renewable fuel in its vehicles by 2022. Ethanol is the most widely used renewable fuel in the US, and its production has grown dramatically over the past decade. According to EISA and RFS, ethanol (produced from corn as well as cellulosic feedstocks) will make up the vast majority of the new renewable fuel requirements. However, ethanol use limited to E10 and E85 (in the case of flex fuel vehicles or FFVs) will not meet this target. Even if all of the E0 gasoline dispensers in the country were converted to E10, such sales would represent only about 15 billion gallons per year. If 15% ethanol, rather than 10% were used, the potential would be up to 22 billion gallons. The vast majority of ethanol used in the United States is blended with gasoline to create E10, that is, gasoline with up to 10% ethanol. The remaining ethanol is sold in the form of E85, a gasoline blend with as much as 85% ethanol that can only be used in FFVs. Although DOE remains committed to expanding the E85 infrastructure, that market will not be able to absorb projected volumes of ethanol in the near term. Given this reality, DOE and others have begun assessing the viability of using intermediate ethanol blends as one way to transition to higher volumes of ethanol. In October of 2010, the EPA granted a partial waiver to the Clean Air Act allowing the use of fuel that contains up to 15% ethanol for the model year 2007 and newer light-duty motor vehicles. This waiver represents the first of a number of actions that are needed to move toward the commercialization of E15 gasoline blends. On January 2011, this waiver was expanded to include model year 2001 light-duty vehicles, but specifically prohibited use in motorcycles and off-road vehicles and equipment. UST stakeholders generally consider fueling infrastructure materials designed for use with E0 to be adequate for use with E10, and there are no known instances of major leaks or failures directly attributable to ethanol use. It is conceivable that many compatibility issues, including accelerated corrosion, do arise and are corrected onsite and, therefore do not lead to a release. However, there is some concern that higher ethanol concentrations, such as E15 or E20, may be incompatible with current materials used in standard gasoline fueling hardware. In the summer of 2008, DOE recognized the need to assess the impact of intermediate blends of ethanol on the fueling infrastructure, specifically located at the fueling station. This includes the dispenser and hanging hardware, the underground storage tank, and associated piping. The DOE program has been co-led and funded by the Office of the Biomass Program and Vehicle Technologies Program with technical expertise from the Oak Ridge National Laboratory (ORNL) and the National Renewable Energy Laboratory (NREL). The infrastructure material compatibility work has been supported through strong collaborations and testing at Underwriters Laboratories (UL). ORNL performed a compatibility study investigating the compatibility of fuel infrastructure materials to gasoline containing intermediate levels of ethanol. These results can be found in the ORNL report entitled Intermediate Ethanol Blends Infrastructure Materials Compatibility Study: Elastomers, Metals and Sealants (hereafter referred to as the ORNL intermediate blends material compatibility study). These materials included elastomers, plastics, metals and sealants typically found in fuel dispenser infrastructure. The test fuels evaluated in the ORNL study were SAE standard test fuel formulations used to assess material-fuel compatibility within a relatively short timeframe. Initially, these material studies included test fuels of Fuel C, CE10a, CE17a, and CE25a. The CE17a test fuel was selected to represent E15 since surveys have shown that the actual ethanol upper limit can be as high as 17%. Later, CE50a and CE85a test fuels were added to the investigation and these results are being compiled for a follow-on report to be published in 2012. Fuel C was used as the baseline reference and is a 50:50 blend of isooctane and toluene. This particular composition was used to represent premium-grade gasoline and was also used as the base fuel for the ethanol blends, where it is denoted by 'C' in the fuel name. The level of ethanol is represented by the number following the letter E. Therefore a 10% blend of ethanol in Fuel C is written as CE10a, where 'a' represents an aggressive formulation of the ethanol that contains water, NaCl, acetic and sulfuric acids per the SAE J1681 protocol