Conferences, Lectures, & Seminars
Events for February
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Utilizing the Ignition Quality Tester (IQT) to determine the impact of fuel physicochemical propert
Wed, Feb 03, 2010 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Greg Bogin,Assistant Research Professor,Department of Chemical Engineering,Colorado School of Mines,Golden, COABSTRACT:The goal of increased combustion efficiency with reduced emissions has sparked increased interest in new technologies for advanced combustion engines such as Low Temperature Combustion (LTC). LTC involves the combustion of thoroughly premixed fuel and air, utilizing high compression ratios and lean equivalence ratios which produce relatively long ignition delay times (compared to typical diesel engines). LTC utilization produces two desirable characteristics: i) high engine efficiency due to high compression ratio and unthrottling, and ii) low NOx and PM emissions due to minimization of traditional high-temperature flame fronts and locally fuel-rich zones. LTC engines, however, present significant challenges as traditional engine control strategies (ignition coil control for Spark Ignition or start-of-injection timing for Compression Ignition) are not employed. Fuel mixture autoignition kinetics dictate ignition timing, resulting in significant control system decoupling. Attaining LTC using petroleum-based fuels (and eventually biofuels) is achievable through the optimal coupling of the fuel injection process with in-cylinder fluid mechanics, and an improved understanding of kinetic pathways to auto-ignition. This requires a concerted approach of experiments and numerical modeling to quantify the effects of fuel chemistry and physical properties on combustion timing, combustion efficiency, and emissions.
A comprehensive understanding of fuel effects on combustion efficiency and emissions is essential for predictive models used to design advanced combustion engines utilizing the LTC regime. It is also essential as non-petroleum based fuels, which can vary widely in fuel chemistry, are adopted. Accomplishing this task requires a research device capable of studying realistic fuels (e.g. low volatility) which are difficult to study using traditional research apparatus such as shock tubes and rapid compression machines. The Ignition Quality Tester (IQT) is a constant volume, spray combustion device designed solely to measure ignition delay, from which a Derived Cetane Number (DCN) is calculated using ASTM method D6890-09. The experimental capabilities of the IQT have been expanded to allow investigation of fuel effects on combustion timing and emissions. In parallel, a computational fluid dynamics (CFD) model was developed using KIVA-3V and linked with CHEMKIN to provide the first significant insights into the coupling of fuel spray physics and chemical kinetics for the IQT. The coupling of experiments and modeling enables fundamental research on the physical and chemical fuel effects on combustion, with the benefit of maintaining the link to the ASTM method for DCN. The CFD model accurately and efficiently reproduces ignition behavior of n-heptane; predicting that the combustion event is governed by autoignition and that dispersed ignition events occur throughout the combustion chamber. 2-methyl-hexane (an isomer of n-heptane having similar physical properties) produces longer ignition delay (ID) times compared to n-heptane, in agreement with rapid compression machines studies. The longer ID of 2-methyl-hexane verifies that chemical kinetics dominate over the physical effects of the fuels. The longer ID also results in higher NOx emissions. Thus, the IQT can bridge the gap between fundamental fuel research and actual internal combustion engine research.
Location: Seaver Science Library (SSL) Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Tuning the Properties of Materials Through Nanostructure: Processing of Large Sized Nanocomposites f
Wed, Feb 10, 2010 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Javier E. Garay Assistant ProfessorDepartment of Mechanical EngineeringMaterials Science and Engineering ProgramUniversity of California, Riverside Improved performance of devices such as high power lasers often hinge on the development of materials with a precise blend of properties. Nanocrystalline materials display significantly different properties and functionalities than their microcrystalline counterparts, yet their direct application in products has been hindered by the difficulty in producing them reliably and efficiently. One reason is that consolidation of nanocrystalline powders usually results in large grain size increase and therefore loss of enhanced nanocrystalline properties. Recently, the versatile material processing technique of current activated pressure assisted densification has proven effective in overcoming the grain growth challengeit is now possible to efficiently produce materials large enough to be viable nanocrystalline parts. The method draws its effectiveness from large electric current densities that serve to heat the materials and also alter the processing kinetics. After an overview of our processing techniques, I will present results on large-sized, fully dense materials with grain sizes much less that 100 nm. The materials have very different properties than traditional materials including improved visible light transmittance, tailorable heat conductivity, and magnetic coupling and can be used as laser host ceramics, magnetic sensors etc. The results will be discussed in terms of crystal length scale effects and proximity of nanoscale phases.
Location: Seaver Science Library, (SSL) Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Turbulence in the Stratified Ocean
Wed, Feb 17, 2010 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Sutanu Sarkar Professor Mechanical and Aerospace Engineering DepartmentUniversity of California at San DiegoLa Jolla, CAABSTRACT:Background fluid stratification, often prevalent in the environment, inhibits vertical turbulent motion, allows wave-like motion, and promotes the formation of coherent structures. Quantification of the dynamical pathways that lead to mixing in spite of stable stratification is of critical interest to environmental modeling including local and regional impact of climate change. Our work utilizes high-resolution numerical resolution to understand links between turbulence, internal waves and coherent vortices. We will discuss the following examples from our recent work on turbulent flows in the ocean: a jet with non-uniform stratification as a model for vertical mixing in Equatorial Under Currents, a boundary layer on a sloping bottom as a model for mixing on a continental slope and finally the wake of a self-propelled submersible.
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Location: Seaver Science Library (SSL) Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Self-Assembly of Hierarchical Materials for Medicine and Energy
Wed, Feb 24, 2010 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Samuel Stupp SOUTHERN CALIFORNIA LECTURE SERIESWinter Quarter 2010JOINTLY SPONSORED BY USC, UCSD, UCLA AND CALTECHBoard of Trustees Professor of Materials Science, Chemistry, and Medicine and Director, Institute for BioNantechnology in Medicine (IBNAM)Department of Materials Science and Engineering, Department of Chemistry, Department of Medicine and Institute for BioNanotechnology in Medicine Northwestern University Evanston, Il 60208 One of the grand challenges in materials science is the development of self-assembly pathways to highly functional structures across scales. Based on biological systems, soft matter and hybrid materials are natural targets in this context. Highly designed small molecules, polymers, biomacromolecules, ionic solutions, and nanoparticles are all potential building blocks for the development of these self-assembling functional materials. In addition to materials with useful combinations of physical properties and controllable shapes, it is also interesting to develop structures that have adaptable and self-repair capabilities. In this lecture I will review self-assembly pathways developed in our laboratory for supramolecular materials using designed molecules. One of the pathways to be described generates a large diversity of bioactive one-dimensional nanostructures and networks that can signal cells to create new materials for regenerative medicine. The driving force for self-assembly in these systems includes hydrogen bond formation, hydrophobic collapse of molecular segments in aqueous environments, and both attractive and repulsive electrostatic forces. A second system to be described involves the self-assembly of polymers and small molecules into membranes or cell-like capsules with hierarchical structures that may find biomedical and energy applications. In these systems, self-repair of large defects occurs readily by re-exposure to building blocks and diffusion barriers can form by contact of two liquids in millisecond time scales. Other systems to be described include the formation of oriented structures with minimal mechanical force, and the formation of hierarchical hybrid materials with electronic properties of interest in energy targets.
Location: Seaver Science Library, (SSL) Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy