On the effect of inter compressor duct length on compressor performance

Compression systems of modern, civil aircraft engines consist of three components: Fan, low-pressure compressor (LPC) and high-pressure compressor (HPC). The efficiency of each component has improved over the last decades by means of rising computational power which made high level aerodynamic optimisations possible. Each component has been addressed individually and separated from the effects of upstream and downstream components. But as much time and effort has been spend to improve performance of rotating components, the stationary inter-compressor duct (ICD) has only received minor attention. With the rotating compression components being highly optimised and sophisticated their performance potential is limited. That is why more aggressive, respectively shorter, ICDs get more and more into the focus of research and engine manufacturers. The length reduction offers high weight saving and thus fuel saving potential as a shorter ICD means a reduction in aircraft engine length. This paper aims at evaluating the impact of more aggressive duct geometries on LPC and HPC performance. A multi objective 3D computational fluid dynamics (CFD) aerodynamic optimisation is performed on a preliminary design of a novel two spool compressor rig incorporating four different operating line and two near-stall (NST) conditions which ensure operability throughout the whole compressor operating range. While the ICD is free to change in length, shape and cross-section area, the blades of LPC and HPC are adjusted for changing duct aerodynamics via profile re-staggering to keep number of free parameters low. With this parametrisation length, reductions for the ICD of up to 40% are feasible while keeping the reduction in isentropic efficiency at aerodynamic design point for the compressor below 1%pt. Three geometries of the Pareto front are analysed in detail focusing on ICD secondary flow behaviour and changes of aerodynamics in LPC and HPC. In order to asses changes in stall margin, speedlines for the three geometries are analysed

Modulübergreifende aerodynamische Verdichterauslegung

Das zukünftige Wachstum des Luftverkehrs sowie die Verschärfung der Emissionsziele zum Schutz des Klimas machen die (Weiter-) Entwicklung effizienter Antriebssysteme zu einer Herausforderung. Gegenüber dem in der Entwicklung von Fluggasturbinen bisher üblichen modularen Ansatz bietet ein integratives Design der Komponenten ein erhebliches Potential zur Leistungs- bzw. Wirkungsgradsteigerung. Dies gilt insbesondere für das hinsichtlich Wirkungsgrad und Betriebsverhalten kritische Verdichtungssystem. Die vorliegende Arbeit soll einen Beitrag zum erweiterten Verständnis des Gesamtsystems Verdichter, bestehend aus den Modulen Nieder- und Hochdruckverdichter sowie dem Verdichterübergangskanal, leisten. Der Fokus liegt dabei auf dem Übergangskanal und dessen Interaktion mit den Verdichtern. In den Voruntersuchungen wird das Modul des Übergangskanals isoliert betrachtet. Eine aggressive Kanalkonfiguration, die durch Sekundärströmungseffekte und Strömungsablösungen gekennzeichnet ist, wird durch eine Endwandkonturierung und 3Dgestaltete Stützstrebe stabilisiert. Anschließend wird der Einfluss aggressiver Kanalkonfigurationen auf den Nieder- und Hochdruckverdichter anhand eines mehrwelligen, vielstufigen Verdichtungssystems untersucht. Unter Einsatz moderner Optimierungsverfahren wird der negative Einfluss von Interaktionseffekten durch eine modulübergreifende Betrachtung des Verdichtersystems minimiert. Neben der Kanallänge und -formgebung werden ebenfalls die angrenzenden Leitgitter sowie die erste Stufe des Hochdruckverdichters an die geänderten Strömungsbedingungen angepasst. Weiterhin wird eine Variation der Austrittsleitgitter des Niederdruckverdichters über den Umfang zur Minderung der Umfangsstörungen im statischen sowie im Totaldruck untersucht. Die durchgeführten Studien zeigen ein erhebliches Potential zur axialen Bauraumreduktion des Verdichtungssystems

ON THE SECONDARY FLOW SYSTEM OF AN AGGRESSIVE INTER COMPRESSOR DUCT

In the last decades much effort has been spent in optimizing the performance of the rotating components of the compression system of civil aircraft engines. While these components are highly optimized, further improvements are limited. In this light, the interfaces between these components are coming into focus of research. Especially the inter compressor duct (ICD) is offering a high potential. Due to a more aggressive design, the length of the whole engine can be reduced. Shorter and thus lighter engines are leading to further fuel savings for the next engine generation. The design of current ICDs is very conservative because of high uncertainties in design space. An extensive test campaign on two very aggressive ICD designs has been conducted at an annular cascade at German Aerospace Center (DLR) Cologne to explore these limitations and a vast amount of test data has been gathered. The test section is comprised of LPC-OGVs, struts and HPC-IGVs. To simulate the influence of the last rotor of the LPC and to vary the incidence of the OGV, a move-able swirler is placed in front of the OGV. This simplification results in differences relative to a real rotor outlet flow. Through geometrical restriction, the ability to move the swirler can only be achieved by adding partial gaps in the rear part of the swirler at hub and shroud. These gaps have a huge impact on the secondary flow structure of the swirler outflow and therefore, the inflow of the ICD. In this paper, the secondary flow system of an aggressive ICD is analyzed in detail by the means of experimentally validated CFD simulations. Attention is given to the impact of the stationary swirler on the secondary flow system. Furthermore, a recommendation for future experimental setups with respect to the described effects is concluded

Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction

[EN] New functionalized polynorbornenes have been obtained in good yields by vinylic copolymerization of norbornene with a (norbornenyl)Sn-Bu(2)Cl monomer, catalyzed by [Ni(C(6)F(5))(2)(SbPh(3))(2)]. Subsequent functionalization produces a wide variety of polymers with different -SnBu(2)R groups (R = aryl, vinyl, alkynyl). The polymers can be used as R-transfer reagents in Stille couplings, thereby providing easy workup and separation of the polymeric tin byproducts from the coupling products. Tin contents of around 0.05 wt% are found in the Stille products. The stannylated polymers can be recycled and reused with good efficiency.Financial support from the Spanish MEC (DGI, grant CT02007-67411/BQU; Consolider Ingenio 2010, grant INTECAT, CSD2006-0003; FPU fellowship to N.C.), and the Junta de Castilla y Leon (project VA117A06) is gratefully acknowledged.Carrera, N.; Gutierrez, E.; Benavente Martínez, R.; Villavieja, MM.; Albeniz, AC.; Espinet, P. (2008). Stannylated Polynorbornenes as New Reagents for a Clean Stille Reaction. Chemistry - A European Journal. 14(32):10141-10148. https://doi.org/10.1002/chem.200800558S1014110148143