Infrared Borescopic Evaluation of High-Energy and Long-Duration Ignition Systems for Lean/Dilute Combustion in Heavy-Duty Natural-Gas Engines

Natural gas (NG) is attractive for heavy-duty (HD) engines for reasons of cost stability, emissions, and fuel security. NG cannot be reliably compression-ignited, but conventional gasoline ignition systems are not optimized for NG and are challenged to ignite mixtures that are lean or diluted with exhaust-gas recirculation (EGR). NG ignition is particularly challenging in large-bore engines, where completing combustion in the available time is more difficult. Using two high-speed infrared (IR) cameras with borescopic access to one cylinder of an HD NG engine, the effect of ignition system on the early flame-kernel development and cycle-to-cycle variability (CCV) was investigated. Imaging in the IR yielded strong signals from water emission lines, which located the flame front and burned-gas regions and obviated image intensifiers. A 9.7-liter, six-cylinder engine was modified to enable exhaust-gas recirculation and to provide optical access. Three ignition technologies were studied: a conventional system delivering 65 mJ of energy to each spark, a high-energy conventional system delivering 140 mJ, and a Bosch Controlled Electronic Ignition (CEI) system. CEI uses electronics to extend the ignition event, yielding sparks up to 5 ms in duration with up to 300 mJ of energy. Air/fuel equivalence ratios, λ, as high as 1.6 (with minimum EGR) and EGR fractions as high as 23% (stoichiometric) were tested; ignition delay, engine-out emissions, fuel consumption and image-derived parameters were compared. In most lean or dilute cases, the 140-mJ system yielded the lowest CCV. The imagery provided information about the early stages of ignition and combustion, where pressure measurements are not reliable. Image-based metrics also revealed that early flame kernels located further from the head yielded better combustion, showing that borescopic IR imaging can provide guidance for future engine design.The information, data, or work presented herein was funded in part by the Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy, under Award Number DE-EE0007307. We also thank Dr. Hao Chen and Angela Wu for their help with software and James Elkins for engine-head modifications.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143838/1/2018-01-1149.pd

Determinanten der Einstellung zur Besteuerung von hohen Erbschaften: Ergebnisse einer Vignettenstudie

Erbschaftssteuern könnten der in den letzten Jahren stetig steigenden Vermögenskonzentration entgegenwirken und eine Durchsetzung der durchaus anerkannten Gerechtigkeitsprinzipien „Gleichheit“ und „Bedarf“ befördern. Vor diesem Hintergrund erscheint die mehrheitliche Ablehnung der Erbschaftssteuer in der deutschen Bevölkerung als paradox. Zur Aufklärung dieses Paradox beizutragen ist das Ziel dieses Artikels. Dazu wurde eine Vignettenstudie, d.h. eine Methode mit einem indirekten Befragungsmodus, angewendet. Die Ergebnisse zeigen, dass Gleichheits- und Bedarfsprinzip insofern zur Geltung kommen, als die Besteuerung hoher zu vererbender Vermögen durchaus unterstützt wird, allerdings nur zu eher geringen Steuersätzen. Aufgrund der aktuellen Debatte zur Begünstigung von Firmenkapital im Erbschaftssteuerrecht wurde besonderes Augenmerk auf die Frage gelegt, hinsichtlich welcher möglichen Gemeinwohlaspekte von Firmenkapital entsprechende Ausnahmeregelungen als gerecht erachtet werden. Hier zeigt sich, dass Firmenkapital häufiger von der Erbschaftssteuer verschont werden soll. Damit ist nicht geklärt, ob höhere Erbschaftssteuern tatsächlich die Funktion der Gemeinwohlproduktion durch Firmen gefährden würden. Allerdings scheint durch zahlreiche öffentliche Statements im Zuge politischer Debatten zur Erbschaftsteuer dieses Argument bei weiten Teilen der Bevölkerung „angekommen“ zu sein und als Steuerverschonungsgrund akzeptiert zu werden. Weiterhin zeigt sich, dass sich politische und normative Orientierungen auf Gerechtigkeitsbewertungen zur Besteuerung von hohen Erbschaften auswirken

Common garden versus common practice – Phenotypic changes in Trifolium pratense L. in response to repeated mowing

Plants react to various biotic and abiotic factors by adjusting their growth pattern. This process, called phenotypic plasticity, can also be observed in the agronomical important fodder plant Trifolium pratense L. (red clover) which is grown worldwide for its high pro-tein content and soil improving ability. After cutting it changes its growth pattern due to phenotypic plasticity and initiates a second growth phase. Here, we analyze the regrowth dynamics of red clover in response to grazing or mowing by recording the plant’s architecture, leaf morphology, and growth performance in different cutting experiments. As previous studies were limited in the number of individuals and carried out via common garden experiments, we analyzed the regrowth reaction of T. pratense under standard agricul-tural field conditions. T. pratense forms smaller and rounder leaflets after repeated cutting, compensated by the production of more bio-mass. Nitrogen contents were subjected to seasonal changes, rather than by changes through cutting. As middle to late cut plants had higher regrowth capacities and regrew more biomass than early cut plants, an optimal time point for biomass harvest can be suggested to maximize the total yield of red clover biomass

Time-resolved infrared imaging and spectroscopy for engine diagnostics

Molecular emissions in the infrared spectral region can provide access to a range of quantities that are of interest in internal- combustion engine research and development. Molecules; such as water, carbon dioxide, carbon monoxide, and hydrocarbons; provide the strongest signals in the range from 1.0 to 5.5 μm. We describe several imaging experiments that employed high-frame-rate infrared cameras to capture spectrally resolved and spectrally integrated signals from both optical and production engines. Spectrally resolved infrared emissions that were recorded at kHz rates (i.e., crank-angle steps) in an optically accessible, propane-fueled, single-cylinder engine are used to guide the development and validation of a radiative-emission model that is integrated into large-eddy simulations (not discussed in this paper). The emissions were dispersed with a spectrometer, and the spectra were recorded with an InSb camera. Clear spectral signatures from water and carbon dioxide were recorded, and the spectra reveal the evolution of combustion through each of 100 consecutive cycles for each engine run. Furthermore, at any wavelength of these spectra, cycle-to-cycle variation can be extracted readily. Cycle- to-cycle variation was of particular interest in a study of a production heavy-duty engine fueled by natural gas.The addition of two borescopes outfitted with high-frame-rate In- GaAs cameras enabled spectrally integrated measurements from 1.0-1.7 μm. The images allow cycle-resolved observations of ignition and flame growth. The intent of this work was to identify and quantify the impact of a range of ignition systems on lean and/or dilute operation limits from a combustion development and stability point of view.The information, data, or work presented herein was funded in part by the Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy, under Award Numbers DE-EE0007278 and DE-EE0007307. The University of Michigan provided Mr. Henrion with partial tuition and stipend support through the Rackham Merit Fellowship. Electro Optical Industries provided the integrating sphere and the blackbody source on loan. Mohammad Alzuabi supported experiments with the optical engine, while Justin Kern supported experiments with the production engine.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149140/1/Sick_AVL_2018.pd

Characterization of radiative heat transfer in a spark-ignition engine through high-speed experiments and simulations

International audienceA combined experimental and Large-Eddy Simulation (LES) study of molecular radiation is presented for combustion in a homogeneous pre-mixed spark-ignition engine. Molecular radiation can account for ~10% of the engine heat loss and could have a noticeable impact on the local conditions within the combustion chamber. The Transparent Combustion Chamber (TCC) engine, a single-cylinder two-valve research engine with a transparent liner and piston for optical access, was used for this study. High-speed infrared emission spectroscopy and radiative post-processing of LES calculations have been performed to gain insight into the timescales and magnitude of radiative emissions of molecular gases during the combustion process. Both the measurements and simulations show significant Cycle-to-Cycle Variations (CCV) of radiative emission. There is agreement in the instantaneous radiative spectrum of experiment and simulation, but the crank-angle development of the radiative spectrum shows disagreement. The strengths and limitations of the optical experiments and radiative simulations are seen in the results and suggest pathways for future efforts in characterizing the influence of molecular radiation. In particular, focusing on the relative changes of the spectral features will be important as they contain information about the thermochemical properties of the gas mixture

On the temperature dependence of correlation functions in the space like direction in hot QCD

We study the temperature dependence of quark antiquark correlations in the space like direction. In particular, we predict the temperature dependence of space like Bethe-Salpeter amplitudes using recent Lattice gauge data for the space like string potential. We also investigate the effect of the space like string potential on the screening mass and discuss possible corrections which may arise when working with point sources.Comment: 15 pages 8 figures (not included, will be sent on request), (SUNY-NTG-94-3

Optical and microphysical properties of smoke over Cape Verde inferred from multiwavelength lidar measurements

Lidar measurements of mixed dust/smoke plumes over the tropical Atlantic ocean were carried out during the winter campaign of SAMUM-2 at Cape Verde. Profiles of backscatter and extinction coefficients, lidar ratios, and Ångstr¨om exponents related to pure biomass-burning aerosol from southern West Africa were extracted from these observations. Furthermore, these findings were used as input for an inversion algorithm to retrieve microphysical properties of pure smoke. Seven measurement days were found suitable for the procedure of aerosol-type separation and successive inversion of optical data that describe biomass-burning smoke. We inferred high smoke lidar ratios of 87 ± 17 sr at 355 nm and 79 ± 17 sr at 532 nm. Smoke lidar ratios and Ångstr¨om exponents are higher compared to the ones for the dust/smoke mixture. These numbers indicate higher absorption and smaller sizes for pure smoke particles compared to the dust/smoke mixture. Inversion of the smoke data set results in mean effective radii of 0.22 ± 0.08 μm with individual results varying between 0.10 and 0.36 μm. The single-scattering albedo for pure biomass-burning smoke was found to vary between 0.63 and 0.89 with a very low mean value of 0.75 ± 0.07. This is in good agreement with findings of airborne in situ measurements which showed values of 0.77 ± 0.03. Effective radii from the inversion were similar to the ones found for the fine mode of the in situ size distributions

Twins in YAl_3(BO_3)_4 and K_2Al_2B_2O_7 Crystals as Revealed by Changes in Optical Activity

Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl_3(BO_3)_4 (YAB) and K_2 Al_2 B_2 O_7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens

Nachweis der Betriebstauglichkeit von gasisolierten HVDC Systemen unter betriebsnahen Bedingungen – Resümee einer Langzeituntersuchung in Griesheim

Im Rahmen der Präsentation wurde das GIL Testfeld in Griesheim vorgestellt. Direkt erdverlegte DC-GIL hat sich grundsätzlich als realisierbar erwiesen, thermomechanisch wie auch dielektrisch; ebenso wurde die neu entwickelte Versuchstechnik qualifiziert. Die Gesamterfahrung mit dem „Prototype Installation Test“ hat gezeigt, dass Langzeittests von neu entwickelten HGÜ-Prototypen wichtige Erkenntnisse für die spätere Netzinstallation liefern, die mit Typprüfungen und üblichen FAT- und SAT-Tests allein nicht gefunden worden wären. Die während der Inbetriebnahme gesammelten Erfahrungen haben gezeigt, wie durch ein erweitertes Inbetriebnahmeverfahren alle typischen HGÜ-Fehler erkannt werden können. Ereignisse während der Inbetriebnahme zeigen Potenziale für zukünftige Optimierungen am DC-GILPrototyp, z. B. weitere Partikelfallenmaßnahmen