Systematic accuracy assessment for alternative aviation fuel evaporation models

Environmental and security of supply concerns cause an increasing demand for alternative fuels in aviation. Different fuel production pathways for alternative aviation fuels have been suggested and approved in recent years. In that respect, changes in fuel production can result in various fuel compositions and properties and thus impose a risk for the use in the aircraft and jet engine; the ASTM D4054 approval process was developed to warrant the safety of flight. Nevertheless, tests are expensive and time-consuming. Particularly for the combustion testing part, numerical simulations can be beneficially used to reduce costs and time. Furthermore, virtual prototyping and robust design methods might be essential in supporting the design of fuel flexible combustion chamber with reduced emissions. The use of simulation in the context of decision making in situations with risks related to humans and the environment raises the questions how reliable and accurate simulations results are. In this work, new methods are applied that have been developed for scientific computing. The focus of these methods is on supporting simulation informed risk-related decision making as the final recipient of validation activities. Hereby, it is of essential importance that metrics describing the accuracy of the models over the domain of application are inferred systematically. Furthermore, by reporting the influence of uncertainties in input quantities on the response quantities, the reliability of the simulation results can be increased substantially. Evaporation is an important sub-process of the fuel preparation in a combustion chamber and depends strongly on the fuel composition and properties. Conventional Jet A-1 and most alternative aviation fuels consist of several hundred of different species. Continuous Thermodynamic Models (CTM) have been successfully used in recent years to describe multicomponent-fuel droplet evaporation of real fuels. CTM capture the details of the fuel evaporation while preserving the information of the fuel composition over the evaporation process with low computational load. Up to the present, validation activities have been performed by comparing numerical simulation results with experimental data from suspended droplets experiments. These tests proved the functionality of the concepts successfully. However, the fuel composition was unknown, and the droplet suspension had a strong intrusive effect. Thus, the validations are limited to qualitative statements. In this work, a validation domain was derived from the character of actual and future alternative aviation fuels to determine quantitative metrics for alternative aviation fuel evaporation models systematically. Experiments with different fuels from the validation domain were performed in a newly designed experiment. The validation experiment enables to study the evaporation of a wide range of fuels under controlled conditions in a non-intrusive way. Global and local metrics for the evaporation models were inferred. The effect of uncertainties in the spray injection conditions on simulation results was determined by using Latin Hypercube Sampling to sample the input domain and to propagate the uncertainties through the governing equations. The resulting uncertainties in the simulation result can be interpreted as the precision of the validation approach. Validation metrics, as well as the precision, give future users (modeler, analyst and decision maker) all information required to assess the model adequacy for the intended use and, if necessary, to determine next actions to improve the model or the validation experiment.Um die langfristige Versorgungssicherheit mit flüssigen Treibstoffen in der Luftfahrt sicherzustellen und die ökologischen Auswirkungen zu minimieren, wurden in den letzten Jahren verschiedene Herstellungspfade für alternative Treibstoffe entwickelt und zugelassen. Jede Änderung im Herstellungspfad hat jedoch einen Einfluss auf die Zusammensetzung des Treibstoffes und birgt somit ein Risiko bei der Nutzung des Treibstoffes in Flugzeug und Triebwerk. Die Zuverlässigkeit der Nutzung neuartiger Treibstoffe wird durch aufwendige und kostenintensive Tests nach dem ASTM D4054 Zulassungsverfahren sichergestellt. Numerische Simulationen haben das Potential, die Zeitdauer von Verbrennungstests beim Zulassungsverfahren maßgeblich zu verkürzen und Kosten einzusparen. Darüber hinaus können der virtuelle Entwurf und Methoden der Entwicklung von robusten Designs eine wesentliche Unterstützung beim Entwurf von neuen brennstoffflexiblen und schadstoffärmeren Brennkammern sein. Hier muss jedoch die Frage gestellt werden, wie zuverlässig und belastbar die aus numerischen Simulationen gewonnenen Informationen sind und inwieweit sie als Basis für Entscheidungen mit Konsequenzen für die Sicherheit von Mensch und Umwelt dienen können. In dieser Arbeit werden neue Methoden für die Validierung von numerischen Modellen angewandt, die im Bereich des wissenschaftlichen Rechnens in den letzten Jahren entwickelt wurden. Das risiko-informierte Entscheiden, basierend auf aus Simulationen gewonnenen Daten, steht hier als Endprodukt im Fokus. Dabei ist es zum einen von wesentlicher Bedeutung, die Genauigkeit der verwendeten Modelle quantitativ und systematisch über den Anwendungsraum der Modelle zu erfassen. Zum anderen wird die Zuverlässigkeit der Modelle maßgeblich erhöht, indem die Auswirkung von Unsicherheiten in den Eingangsgrößen auf relevante Zielgrößen in die Untersuchung einbezogen wird. Die Verdunstung ist ein wichtiger Teilprozess der Treibstoffaufbereitung in der Brennkammer, der unter anderem stark von den Treibstoffeigenschaften und somit der Treibstoffzusammensetzung abhängt. Konventionell hergestelltes Jet A-1 und ebenso die meisten alternativen Luftfahrttreibstoffe bestehen aus hunderten Einzelkomponenten. Um die Mehrkomponenten-Verdunstung realer Treibstoffe abbilden zu können, wurde in den letzten Jahren die Methode der kontinuierlichen Thermodynamik erfolgreich angewandt. Diese Methode ermöglicht es, Veränderungen in der Treibstoffzusammensetzung während der Verdunstung detailliert wiederzugeben und ist dabei sehr rechenzeiteffizient. Bisherige Validierungen wurden durch den Vergleich von Simulationsergebnissen mit Daten durchgeführt, die aus Experimenten an aufgehängten Tropfen gewonnen wurden. Durch diese Tests wurde die Funktionalität der Modelle erfolgreich nachgewiesen, jedoch war die Zusammensetzung der Treibstoffe nicht bekannt und die Tropfenaufhängung hatte einen stark intrusiven Einfluss. Damit sind bisherige Validierungen des Modelles nur auf qualitative Aussagen beschränkt. In dieser Arbeit wurde, basierend auf den Charakteristika aktueller sowie potentieller alternativer Treibstoffe, eine Validierungsdomain für Luftfahrttreibstoffe abgeleitet. Diese ermöglichte es, systematisch quantitative Metriken über die Genauigkeit von Verdunstungsmodellen für alternative Luftfahrttreibstoffe zu bestimmen. In einem neu entwickelten nicht intrusiven Validierungsexperiment wurde die Verdunstung verschiedener Treibstoffe aus der Validierungsdomain unter kontrollierten Bedingungen detailliert untersucht. Anhand der gewonnenen experimentellen Daten und Simulationsergebnisse konnten globale und lokale Validierungsmetriken abgeleitet werden. Der Einfluss von Unsicherheiten in den Spraystartbedingungen auf die Simulationsergebnisse wurde mittels Latin Hypercube Sampling bestimmt. Die resultierenden Unsicherheiten in den Simulationsergebnissen können als Präzision des Validierungsexperimentes interpretiert werden. Die Validierungsmetriken sowie die Information über die Präzision des Validierungsexperimentes ermöglichen dem zukünftigen Nutzer die Adäquatheit des Modells für den Einsatzbereich zu bewerten und gegebenenfalls Maßnahmen für die Verbesserung des Modells oder des Validierungsexperimentes vorzuschlagen

Design and analysis of Bio-diesel extraction processes

The need for alternative fuel sources is an ever growing concern for the resources sector. With finite resources rapidly being consumed and pollution levels rising, alternative fuel sources are necessary to not only alleviate the demand on fossil fuels, but also decrease the amount of pollutants released into the atmosphere. This document will outline the research, design and analysis that were conducted to derive a new continuous solvent extraction process to facilitate the removal of lipids from used food sources for use in the production of biodiesel. The process of solvent extraction is a well-known process, however it is desired to research and develop a process to replace the traditional hexane solvent extraction method. The new method would employ the use of dimethyl ether (DME) as the solvent. From previous experimentation it can be seen that on an experimental scale, DME gave higher yields under similar conditions than the traditional hexane process. The major issue with the use of DME in this design is that under standard conditions it takes the form of a vapour. This means that the vapour must be cooled and compressed before it can be used as a liquid in the extraction process. The main purpose of this thesis is to determine the economic feasibility, as well as the physical viability of this process. This document outlines the ideas and concepts that were researched, concluding them in a literature review, as well as an in depth description of the simulations that were created to test the designed system. The final part of this document analyses the results that were collected from this simulation and the economic analysis of the system. The results that were collected throughout the project suggest that DME solvent extraction could be a viable alternative to the traditional hexane extraction process

Predicting physical properties of alkanes with neural networks

We train artificial neural networks to predict the physical properties of linear, single branched, and double branched alkanes. These neural networks can be trained from fragmented data, which enables us to use physical property information as inputs and exploit property-property correlations to improve the quality of our predictions. We characterize every alkane uniquely using a set of five chemical descriptors. We establish correlations between branching and the boiling point, heat capacity, and vapor pressure as a function of temperature. We establish how the symmetry affects the melting point and identify erroneous data entries in the flash point of linear alkanes. Finally, we exploit the temperature and pressure dependence of shear viscosity and density in order to model the kinematic viscosity of linear alkanes. The accuracy of the neural network models compares favorably to the accuracy of several physico-chemical/thermodynamic methods

Basic Research Needs for Geosciences: Facilitating 21st Century Energy Systems

Executive Summary Serious challenges must be faced in this century as the world seeks to meet global energy needs and at the same time reduce emissions of greenhouse gases to the atmosphere. Even with a growing energy supply from alternative sources, fossil carbon resources will remain in heavy use and will generate large volumes of carbon dioxide (CO2). To reduce the atmospheric impact of this fossil energy use, it is necessary to capture and sequester a substantial fraction of the produced CO2. Subsurface geologic formations offer a potential location for long-term storage of the requisite large volumes of CO2. Nuclear energy resources could also reduce use of carbon-based fuels and CO2 generation, especially if nuclear energy capacity is greatly increased. Nuclear power generation results in spent nuclear fuel and other radioactive materials that also must be sequestered underground. Hence, regardless of technology choices, there will be major increases in the demand to store materials underground in large quantities, for long times, and with increasing efficiency and safety margins. Rock formations are composed of complex natural materials and were not designed by nature as storage vaults. If new energy technologies are to be developed in a timely fashion while ensuring public safety, fundamental improvements are needed in our understanding of how these rock formations will perform as storage systems. This report describes the scientific challenges associated with geologic sequestration of large volumes of carbon dioxide for hundreds of years, and also addresses the geoscientific aspects of safely storing nuclear waste materials for thousands to hundreds of thousands of years. The fundamental crosscutting challenge is to understand the properties and processes associated with complex and heterogeneous subsurface mineral assemblages comprising porous rock formations, and the equally complex fluids that may reside within and flow through those formations. The relevant physical and chemical interactions occur on spatial scales that range from those of atoms, molecules, and mineral surfaces, up to tens of kilometers, and time scales that range from picoseconds to millennia and longer. To predict with confidence the transport and fate of either CO2 or the various components of stored nuclear materials, we need to learn to better describe fundamental atomic, molecular, and biological processes, and to translate those microscale descriptions into macroscopic properties of materials and fluids. We also need fundamental advances in the ability to simulate multiscale systems as they are perturbed during sequestration activities and for very long times afterward, and to monitor those systems in real time with increasing spatial and temporal resolution. The ultimate objective is to predict accurately the performance of the subsurface fluid-rock storage systems, and to verify enough of the predicted performance with direct observations to build confidence that the systems will meet their design targets as well as environmental protection goals. The report summarizes the results and conclusions of a Workshop on Basic Research Needs for Geosciences held in February 2007. Five panels met, resulting in four Panel Reports, three Grand Challenges, six Priority Research Directions, and three Crosscutting Research Issues. The Grand Challenges differ from the Priority Research Directions in that the former describe broader, long-term objectives while the latter are more focused

Energy: A continuing bibliography with indexes, issue 9, April 1976

This bibliography lists 345 reports, articles, and other documents introduced into the NASA scientific and technical information system from January 1, 1976 through March 31, 1976

List of Bureau of Mines publications and articles, January 1, 1960, to December 31, 1964 with subject and author index

The Bureau of Mines was establis4ed in the public interest to conduct inquiries and scientific and technologic investigations concerning mining and the preparation, treatment, and utilization of mineral substances; to promote health and safety in the mineral industries; to conserve mineral resources and prevent their waste; to further economic development; to increase efficiency in the mining, metallurgical, quarrying, and other mineral industries; and to inquire into the economic conditions affecting these industries. The organic act of the Bureau, as amended by Congress and approved February 25, 1913, made it the province and duty of the Bureau to "disseminate information concerning these subjects 'in such manner as will best carry out the purposes of this Act.\ue2\u20ac?In accordance with that directive, the Bureau reports the findings of its research and investigations in its own series of publications and also in articles that appear in scientific, technical, and trade journals; in proceedings of conventions and seminars; in reference books; and in other non-Bureau sources. The number of these reports, the wide range of subjects they cover, and the variety of mediums in which they appear make the kind of list and index presented in this special publication both necessary and valuable. This issue describes Bureau reports and articles published during the period January 1, 1960 to December 31, 1964. It supplements the 50-year list of Bureau publications issued from July 1, 1910, to January 1, 1960, and the 50-year list of articles by Bureau authors published outside the Bureau from July 1, 1910, to January 1, 1960. It supersedes the annual lists of Bureau publications and articles from January 1 to December 31, 1960, from January 1 to December 31, 1961, from January 1 to December 31, 1962, and from January 1 to December 31, 1963.7The leading general and technical libraries of the United States maintain files of the Bureau's publications. A list of these libraries appears immediately following this introduction

Energy Primer. Online Textbook based on Chapter 1 of the Global Energy Assessment (GEA)

This Energy Primer aims at a basic-level introduction to fundamental concepts and data that help to understand energy systems holistically and to provide a common conceptual and terminological framework before examining in greater detail the various aspects of energy systems be them technological, economic, or environmental. As such the text aims to provide a basic introductory reader suitable for the core content of any introductory-level energy class or as framing complement to more specialized energy classes. Customary energy texts usually focus on describing current energy industries through a supply side perspective, which this Energy Primer does not intend to duplicate. (In depth treatments of energy supply and industry aspects of energy systems are provided in Chapters 11 to 15 of the Global Energy Assessment, all available online