Rotordynamics, Design Aspects, Field and Operational Experiences of a Novel, Large Compressor String Supported by Active Magnetic Bearings

LecturesThe giant Groningen onshore gas field in the Northeastern Netherlands started production in 1963. About 35 years later, the decreasing reservoir pressure required a first stage of compression to provide sufficient capacity at the required 65 bar (940 psi) grid pressure. Now, a first pilot plant for a second stage of compression is installed in the accelerated cluster Schaapbulten (SCB) and started production end of 2013. The novel compression string installed consists of a 23- MW synchronous, high-speed motor in a double-end-drive configuration, driving two gearless driven 7- and 8-stage compressors. The approximate 16m (52ft) long train, with about 14mm (0,55inch) axial thermal elongation, is supported by six radial active magnetic bearings (AMBs) and two axial AMBs at the train’s non-driven ends. This contribution deals with the axial, radial and torsional rotordynamics of the AMB-supported string focusing on the two compressors, as well as with string design aspects and latest field / operational experiences. The design aspects touch points like the trade-off in the coupling selection process and resonance frequency optimizations. Field experiences concerning experimental torsional string analysis and run-out effects in combination with the closed loop AMB controller design are presented. Derived and presented improvements hav

Rotordynamics, Design Aspects, Field and Operational Experiences of a Novel, Large Compressor String Supported by Active Magnetic Bearings

LecturesThe giant Groningen onshore gas field in the Northeastern Netherlands started production in 1963. About 35 years later, the decreasing reservoir pressure required a first stage of compression to provide sufficient capacity at the required 65 bar (940 psi) grid pressure. Now, a first pilot plant for a second stage of compression is installed in the accelerated cluster Schaapbulten (SCB) and started production end of 2013. The novel compression string installed consists of a 23- MW synchronous, high-speed motor in a double-end-drive configuration, driving two gearless driven 7- and 8-stage compressors. The approximate 16m (52ft) long train, with about 14mm (0,55inch) axial thermal elongation, is supported by six radial active magnetic bearings (AMBs) and two axial AMBs at the train’s non-driven ends. This contribution deals with the axial, radial and torsional rotordynamics of the AMB-supported string focusing on the two compressors, as well as with string design aspects and latest field / operational experiences. The design aspects touch points like the trade-off in the coupling selection process and resonance frequency optimizations. Field experiences concerning experimental torsional string analysis and run-out effects in combination with the closed loop AMB controller design are presented. Derived and presented improvements hav

Improved identification of conserved cassette exons using Bayesian networks

<p>Abstract</p> <p>Background</p> <p>Alternative splicing is a major contributor to the diversity of eukaryotic transcriptomes and proteomes. Currently, large scale detection of alternative splicing using expressed sequence tags (ESTs) or microarrays does not capture all alternative splicing events. Moreover, for many species genomic data is being produced at a far greater rate than corresponding transcript data, hence <it>in silico </it>methods of predicting alternative splicing have to be improved.</p> <p>Results</p> <p>Here, we show that the use of Bayesian networks (BNs) allows accurate prediction of evolutionary conserved exon skipping events. At a stringent false positive rate of 0.5%, our BN achieves an improved true positive rate of 61%, compared to a previously reported 50% on the same dataset using support vector machines (SVMs). Incorporating several novel discriminative features such as intronic splicing regulatory elements leads to the improvement. Features related to mRNA secondary structure increase the prediction performance, corroborating previous findings that secondary structures are important for exon recognition. Random labelling tests rule out overfitting. Cross-validation on another dataset confirms the increased performance. When using the same dataset and the same set of features, the BN matches the performance of an SVM in earlier literature. Remarkably, we could show that about half of the exons which are labelled constitutive but receive a high probability of being alternative by the BN, are in fact alternative exons according to the latest EST data. Finally, we predict exon skipping without using conservation-based features, and achieve a true positive rate of 29% at a false positive rate of 0.5%.</p> <p>Conclusion</p> <p>BNs can be used to achieve accurate identification of alternative exons and provide clues about possible dependencies between relevant features. The near-identical performance of the BN and SVM when using the same features shows that good classification depends more on features than on the choice of classifier. Conservation based features continue to be the most informative, and hence distinguishing alternative exons from constitutive ones without using conservation based features remains a challenging problem.</p

Wie verarbeiten Schüler/innen Sachinformationen in Problem- und Entscheidungssituationen Nachhaltiger Entwicklung? Ein Beitrag zur Bewertungskompetenz. Projekt Bewertungskompetenz

Ziel des Artikels ist die Herleitung eines Rahmenkonzeptes der Bewertungskompetenz als Basis für die Modellierung der Teilkompetenz „Generieren und Reflektieren von Sachinformationen“. In diesem Artikel geht es primär um eine theoretische Fundierung und damit verbunden um einen ersten empirischen Zugang zur Erfassung dieser Teilkompetenz. Konkret zeigt der vorliegende Artikel auf, wie offene Aufgaben angelegt sein sollten, um herauszufinden, ob Schüler/innen a) die Verbindungen von Ökologie, Ökonomie und Sozialem erkennen, b) Handlungsoptionen auf dieser Basis entwickeln und c) Handlungsoptionen im Hinblick auf ihre Tragfähigkeit beurteilen. Er stellt damit ein Rahmenkonzept für die Aufgabenentwicklung und Aufgabenanalyse für eine zukünftige Modellierung und Testentwicklung für die Teilkompetenz „Generieren und Reflektieren von Sachinformationen“ bereit. (DIPF/Orig.

Investigations On The Dynamic Coefficients Of Impeller Eye Labyrinth Seals.

Lecturepg. 53-70For many application fields of turbocompressors the rotor stability has become the most important part of the rotordynamic analysis. A comprehensive knowledge of these seal forces is mandatory to ensure an adequate overall design of the compressor as early as the quotation phase. While in earlier times the focus was on the balance drum contribution as the major source of excitation, it has in the meantime become evident that the effects from the impeller eye-seals also have to be considered as a further destabilizing contribution. However, up to now the task of measurement of impeller-eye-seal dynamic coefficients has remained a major challenge. This paper presents a new approach for generation of high-quality data on a unique full-scale high-pressure test rig, in which specific attention is paid to impeller-eye seals. The applied strategy combines results from the test rig obtained from different methods with findings from computational fluid dynamic (CFD) investigations. The publication of dimensional data offers further use of these results within the turbomachinery community