Use Of Computational Fluid Dynamics And Scale Model Component Testing For A Large FCC Prototype Air Compressor

LecturePg. 69-76The purpose of this paper is to describe the use of computational fluid dynamics (CFD) and scale model testing techniques that were used accurately predict and confirm the performance of a large centrifugal air compressor. Compressor performance was later verified by a field performance test

Estimation of the Aerodynamic Force Induced by Vaneless Diffuser Rotating Stall in Centrifugal Compressor Stages

Abstract Rotating stall in centrifugal compressors not only adversely affects the performance before surge, but also can generate high subsynchronous vibrations, marking the minimum flow limit of a machine. Recent works presented an experimental approach to estimate the stall force induced by the unbalanced pressure field in a vaneless diffuser using dynamic pressure measurements. In this study, the results of a 3D-unsteady simulation of a radial stage model were used to estimate the stall force and to compare it with the approximation obtained with an "experimental-like" approach. Results showed that: a) the experimental approach, using an ensemble average approach for transposing data between time and space domains provides sufficiently accurate results; b) the momentum contribution, neglected in experiments, gives negligible contribution to the final intensity of the stall force

Development of a Research Test Rig for Advanced Analyses in Centrifugal Compressors

Abstract In this study, the design process of a new research test rig for centrifugal compressor stages is presented. The rig has been specifically conceived for advanced analyses, with particular focus on rotating stall and in general on the operating conditions close to the minimum flow limit, which represent the research frontier in view of an extension of the stages rangeability. The new rig will be able to test industrial impellers at peripheral Mach numbers up to 0.7, operating in open-loop with ambient inlet conditions. A modular design will allow to test different stage configurations and then to carry out systematic optimization campaigns on a single specific component. The conceptual design of the rig is here described and explained, including the selection of the best architecture and layout, the drivetrain assessment and the rotordynamic analysis

STALL INDUCED AERODYNAMIC FORCING AND ROTOR VIBRATIONS IN A MULTISTAGE CENTRIFUGAL COMPRESSOR

LectureThe Oil & Gas industry is looking with increased interest at solutions for improving operating flexibility of centrifugal compressors. The stable operation of a compressor stage or machine is generally limited at the left of operating range by the occurrence of a local aerodynamic unsteady phenomenon, the rotating stall, which usually precedes the surge. Rotating stall could cause, depending on the actual operating conditions, severe sub-synchronous vibrations to the rotor which may compromise rotordynamic behavior, preventing the machine from operating at very low flow rates. An accurate characterization of rotating stall phenomena, and their impact on rotordynamic stability, may represent an important step forward in centrifugal compressor design and performance predictability, insofar as it allows to correctly predict the real operating range of the machine. In recently published works the authors presented a procedure which allows reconstructing the pressure unbalance due to the diffuser rotating stall, to estimate the rotating force acting on the shaft and, by means of a rotordynamic model, the vibration at the bearings. In addition to this, a criterion to scale the rotating force coming from model test conditions up to fullscale machine conditions has been developed and successfully validated. In this framework a thorough work has been performed to apply the aforementioned procedure to an LNG multistage compressor. Firstly, the stages which equip the machine were tested as single scaled-down stages in a model test rig, in order to fully characterize their dynamic behavior while approaching the left limit and operating in stall condition. Then, the full scale machine has been equipped with dynamic pressure probes in different locations along the gas flow path, and has been tested according to ASME PTC-10 standard; this allowed to capture the stall inception and its evolution and finally to get the rotating pressure pattern acting on the rotor. A noticeable agreement was obtained between the force resulting from the pressure field integration and the one obtained through a proper scaling of the test data. Finally, the calculated stall force has been used as an input in a rotordynamic model of the whole compressor: the predicted Subsynchronous Vibration (SSV) estimated at the displacement probe location has been compared with the measured value showing some differences which can be related to the proximity of the first rotor mode

L-Lactide polymerization by calix[4]arene-titanium (IV) complex using conventional heating and microwave irradiation

AbstractSince the first contributions by Gedye and Giguere in 1986, growing attention has been registered on the use of microwave heating in organic synthesis. However still many aspects need to be clarified especially about the so called "microwave effect" and the possible degradation phenomena that may be recognized during polymer synthesis. In this work the complex cone-25,27- dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been tested for the ring opening polymerization of L-lactide, comparing the effect of conventional heating with a possible microwave assisted strategy. The polymers obtained were fully characterized (NMR, IR, HPLC-SEC, DSC, MALDI-TOF and WAXD analysis). As expected the use of microwave irradiation induced an increase of the polymerization rate. On the other side the use of microwaves resulted in a slight loss of the control over molecular weight and molecular weight distribution if compared with a conventional thermal treatment

An easily recoverable and recyclable homogeneous polyester-based Pd catalytic system for the hydrogenation of alpha,beta-unsaturated carbonyl compounds

Abstract Homogeneous catalysis is an efficient tool to carry out hydrogenation processes but the major drawback is represented by the separation of the expensive catalyst from the product mixture. In this view we prepared a polyester-based Pd catalytic system that offers the advantages of both homogenous and heterogeneous catalyses: efficacy, selectivity and recyclability. Here its application in the hydrogenation of selected α,β-unsaturated carbonyl compounds is described.Homogeneous catalysis is an efficient tool to carry out hydrogenation processes but the major drawback is represented by the separation of the expensive catalyst from the product mixture. In this view we prepared a polyester-based Pd catalytic system that offers the advantages of both homogenous and heterogeneous catalyses: efficacy, selectivity and recyclability. Here its application in the hydrogenation of selected alpha,beta-unsaturated carbonyl compounds is described. (C) 2015 Elsevier B.V. All rights reserved

First finds of Prunus domestica L. in Italy from the Phoenician and Punic periods (6th-2nd centuries BC)

Abstract During the archaeological excavations in the Phoenician and Punic settlement of Santa Giusta (Oristano, Sardinia, Italy), dating back to the 6th–2nd centuries bc, several Prunus fruitstones (endocarps) inside amphorae were recovered. The exceptional state of preservation of the waterlogged remains allowed morphometric measurements to be done by image analysis and statistical comparisons made with modern cultivated and wild Prunus samples collected in Sardinia. Digital images of modern and archaeological Prunus fruitstones were acquired with a flatbed scanner and analysed by applying image analysis techniques to measure 26 morphometric features. By applying stepwise linear discriminant analysis, a morphometric comparison was made between the archaeological fruitstones of Prunus and the modern ones collected in Sardinia. These analyses allowed identification of 53 archaeological fruitstones as P. spinosa and 11 as P. domestica. Moreover, the archaeological samples of P. spinosa showed morphometric similarities in 92.5% of the cases with the modern P. spinosa samples currently growing near the Phoenician and Punic site. Likewise, the archaeological fruitstones identified as P. domestica showed similarities with the modern variety of P. domestica called Sanguigna di Bosa which is currently cultivated near the village of Bosa. Currently, these findings represent the first evidence of P. domestica in Italy during the Phoenician and Punic periods. Keywords Archaeobotany · Image analysis · Morphometric features · Prunus · Sardini