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  • Fluid Mechanics and Thermodynamics  (3)
  • General Chemistry  (3)
  • 1,2-Thiazetidine 1,1-dioxides, silylation of  (1)
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Keywords
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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of 4-silylcyclobut-2-enethiones and their use in cyclobutadiene generation (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 949-956 
    Details
    ISSN: 0947-6539
    Keywords: alkynyl sulfides ; cyclobutadienes ; cyclobutenethiones ; desilylation ; ynamines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkynyl silyl sulfides 2 reacted with ynamines 3 to give 1:1 adducts. The structure of 4-silylcyclobut-2-enethiones 4 was confirmed by X-ray analysis of 4a. A cyclobutadiene intermediate is probably not involved in this reaction; we think that it is initiated by a silyl transfer from 2 to 3, and that this is followed by a combination of the resulting ions to give the unsaturated thioketene 7, which undergoes an electrocyclization to give products 4. In the reaction of thiones 4 with trimethyloxonium tetrafluoroborate (Meerrwein salt) selective methylation at sulfur was observed to give cyclobutenethionium ions 16. Ions 16 underwent fluoride-induced desilylation with various fluoride sources to give cyclobutadienes 17, which could not be isolated, but trapping of 17 a-c was possible with dimethyl acetylenedicarboxylate yielding regioisomeric benzene derivatives 20-23. Similarly, 17 a and bis(methylthio)methylene malononitrile (24) led to hexatriene derivative 27 by a sequence of cycloaddition and two ring-opening reactions. In contrast, silyl-substituted cyclobutadienes 17d,e dimerized even in the presence of trapping agents to anti-tricyclo-[4.2.0.02,5]octadienes 29; this suggests that a two-step cycloaddition is taking place, rather than a concerted Diels-Alder reaction. Attempts to intercept 17d, e, generated from 16d,e with cyclopentadiene (30), gave deprotonation of 30 leading to substitution of the methylthio group in 16 and finally to formation of cyclobutenes 33 through a hydrogen shift.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020807
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Octaethylhemiporphycen: Synthese, Molekülstruktur und PhotophysikDiese Arbeit wurde von der Alexander-von-Humboldt-Stiftung (J. L. S. und S. J. W.) sowie zum Teil vom BMBF-Verbundforschungsprojekt „Photodynamische Lasertherapie“ (E. V. und K. S.) unterstützt.Professor Heinz A. Staab zum 70. Geburtstag gewidmet (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 109 (1997), S. 1725-1728 
    Details
    ISSN: 0044-8249
    Keywords: Chiralität ; Hemiporphycen ; N-Liganden ; Photophysik ; Porphyrinoide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19971091525
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  • 3
    Electronic Resource
    Electronic Resource
    Eigenschaften und Reaktionen substituierter 1,2-Thiazetidin-1,1-dioxide: 2-und/oder 4-silylierte 1,2-Thiazetidin-1,1-dioxide (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 975-983 
    Details
    ISSN: 0170-2041
    Keywords: 1,2-Thiazetidine 1,1-dioxides, silylation of ; β-Sultams ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Properties and Reactions of Substituted 1,2-Thiazetidine 1,1-Dioxides: 2-and/or 4-Silylated 1,2-Thiazetidine 1,1-DioxidesDepending on the reaction conditions and the molar ratio of the reactants, all possible N- and/or C-4 silylated β-sultams 2-11; are prepared starting with 1,2-thiazetidine 1,1-dioxide (1), The 2,3-disubstituted β-sultams 16 and 19 are silylated at C-4. Disilylation is preferred. The X-ray analysis of 2d is reported. Stability and some spectroscopic properties are briefly discussed.
    Notes: Durch Silylierung unter verschiedenen Bedingungen und in Abhängigkeit von den molaren Verhältnissen der Reaktanden können aus 1,2-Thiazetidin-1,1-dioxid (β-Sultam, 1) alle denkbaren an N- und C-4 silylierten Produkte 2-11 erhalten werden. Die 2,3-disubstituierten β-Sultame 16 und 19 werden an C-4 silyliert, wobei Disilylierung bevorzugt ist. Von 2d wird die Struktur durch eine Röntgenstrukturuntersuchung bei -130°C geklärt. Die Stabilität und einige spektroskopische Eigenschaften werden diskutiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890254
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  • 4
    Electronic Resource
    Electronic Resource
    Octaethylhemiporphycene: Synthesis, Molecular Structure and PhotophysicsThis work was funded by the Alexander von Humboldt Foundation (J. L. S. and S. J. W.), and in part by the BMBF-Verbundforschungsprojekt “Photodynamische Lasertherapie” (E. V. and K. S.) and the U. S. National Science Foundation (J. L. S.).Dedicated to Professor Heinz A. Staab on the occasion of his 70th bithday (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 36 (1997), S. 1651-1654 
    Details
    ISSN: 0570-0833
    Keywords: chirality ; N ligands ; photophysics ; porphyrinoids ; synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199716511
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  • 5
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    Study of Convective Flow Effects in Endwall Casing Treatments in Transonic Compressor Rotors (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The unsteady convective flow effects in a transonic compressor rotor with a circumferential-groove casing treatment are investigated in this paper. Experimental results show that the circumferential-groove casing treatment increases the compressor stall margin by almost 50% for the current transonic compressor rotor. Steady flow simulation of the current casing treatment, however, yields only a 15% gain in stall margin. The flow field at near-stall operation is highly unsteady due to several self-induced flow phenomena. These include shock oscillation, vortex shedding at the trailing edge, and interaction between the passage shock and the tip clearance vortex. The primary focus of the current investigation is to assess the effects of flow unsteadiness and unsteady flow convection on the circumferential-groove casing treatment. Unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) techniques were applied in addition to steady Reynolds-averaged Navier-Stokes (RANS) to simulate the flow field at near-stall operation and to determine changes in stall margin. The current investigation reveals that unsteady flow effects are as important as steady flow effects on the performance of the circumferential grooves casing treatment in extending the stall margin of the current transonic compressor rotor. The primary unsteady flow mechanism is unsteady flow injection from the grooves into the main flow near the casing. Flows moving into and out of the grooves are caused due to local pressure difference near the grooves. As the pressure field becomes transient due to self-induced flow oscillation, flow injection from the grooves also becomes unsteady. The unsteady flow simulation shows that this unsteady flow injection from the grooves is substantial and contributes significantly to extending the compressor stall margin. Unsteady flows into and out of the grooves have as large a role as steady flows in the circumferential grooves. While the circumferential-groove casing treatment seems to be a steady flow device, unsteady flow effects should be included to accurately assess its performance as the flow is transient at near-stall operation.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: GT2012-68411 , E-18398 , ASME Turbo Expo; Jun 11, 2012 - Jun 15, 2012; Copenhagen; Denmark
    Format: application/pdf
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  • 6
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    Aerodynamic Inner Workings of Circumferential Grooves in a Transonic Axial Compressor (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The current paper reports on investigations of the fundamental flow mechanisms of circumferential grooves applied to a transonic axial compressor. Experimental results show that the compressor stall margin is significantly improved with the current set of circumferential grooves. The primary focus of the current investigation is to advance understanding of basic flow mechanics behind the observed improvement of stall margin. Experimental data and numerical simulations of a circumferential groove were analyzed in detail to unlock the inner workings of the circumferential grooves in the current transonic compressor rotor. A short length scale stall inception occurs when a large flow blockage is built on the pressure side of the blade near the leading edge and incoming flow spills over to the adjacent blade passage due to this blockage. The current study reveals that a large portion of this blockage is created by the tip clearance flow originating from 20% to 50% chord of the blade from the leading edge. Tip clearance flows originating from the leading edge up to 20% chord form a tip clearance core vortex and this tip clearance core vortex travels radially inward. The tip clearance flows originating from 20% to 50% chord travels over this tip clearance core vortex and reaches to the pressure side. This part of tip clearance flow is of low momentum as it is coming from the casing boundary layer and the blade suction surface boundary layer. The circumferential grooves disturb this part of the tip clearance flow close to the casing. Consequently the buildup of the induced vortex and the blockage near the pressure side of the passage is reduced. This is the main mechanism of the circumferential grooves that delays the formation of blockage near the pressure side of the passage and delays the onset of short length scale stall inception. The primary effect of the circumferential grooves is preventing local blockage near the pressure side of the blade leading edge that directly determines flow spillage around the leading edge. The circumferential grooves do not necessarily reduce the over all blockage built up at the rotor tip section.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: IGTC2007-ABS-55 , 2007 International Gas Turbine Congress (IGTC); Dec 01, 2007; Tokyo; Japan
    Format: application/pdf
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  • 7
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    Investigation of Unsteady Flow Behavior in Transonic Compressor Rotors with LES and PIV Measurements (2009)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In the present study, unsteady flow behavior in a modern transonic axial compressor rotor is studied in detail with large eddy simulation (LES) and particle image velocimetry (PIV). The main purpose of the study is to advance the current understanding of the flow field near the blade tip in an axial transonic compressor rotor near the stall and peak-efficiency conditions. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. Casing-mounted unsteady pressure transducers have been widely applied to investigate steady and unsteady flow behavior near the casing. Although many aspects of flow have been revealed, flow structures below the casing cannot be studied with casing-mounted pressure transducers. In the present study, unsteady velocity fields are measured with a PIV system and the measured unsteady flow fields are compared with LES simulations. The currently applied PIV measurements indicate that the flow near the tip region is not steady even at the design condition. This self-induced unsteadiness increases significantly as the compressor rotor operates near the stall condition. Measured data from PIV show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics of the flow from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The present study indicates that stall inception is heavily dependent on unsteady behavior of the flow field near the leading edge of the blade tip section for the present transonic compressor rotor.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: ISABE-2009-02 , E-17156-P , 2009 ISABE Conference; Sep 07, 2009 - Sep 11, 2009; Montreal; Canada
    Format: application/pdf
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