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[en] Although compressor blades have long been shrouded for aerodynamic and structural reasons, the importance of the leakage flow in the shrouded axial compressor has been investigated recently. However, the effects of the leakage tangential velocity variation on the blade passage flow are unknown. Therefore, this paper reports on an experimental investigation of the loss and flow turning in the blade passage in shrouded axial compressor cascades subject to the variation of the leakage tangential velocity. The newly found results are as follows. First, increasing the leakage tangential velocity reduces overall loss up to 32.6% compared to the reference case. Second, increasing the leakage tangential velocity spreads loss core in the pitch-wise direction. Thus, loss core becomes more two-dimensional. Third, increasing the leakage tangential velocity makes the near hub passage flow more radially uniform
[en] In this study, the axial-compressor-design and performance/flow analysis program is developed. A mean-line analysis was used to determine optimum arrangement of overall geometry and its off-design performance is predicted by stage-stacking method. Three dimensional blade shape is generated using radial equilibrium equation and vortex methods. Various blade shape is generated and their performance is compared. Finally the quasi-three dimensional flow analysis is applied to investigate the detailed flow phenomena
[en] In the present work the results of analytical models of performance are compared with experimental data acquired in the multi flux axial compressor test facility, built in The Pilcaniyeu Technological Complex for the SIGMA project.We describe the experimental circuit and the data of the dispersion inside the axial compressor obtained using a tracer gas through one of the annular inlets.The attained results can be used to validate the design code for the multi flux axial compressors and SIGMA industrial plant
[en] The shock wave boundary layer interaction on the suction side of transonic compressor blade is one of main objectives of TFAST project (Transition Location Effect on Shock Wave Boundary Layer Interaction). In order to look more closely into the flow structure on the suction side of a blade, a design of a generic test section in linear transonic wind tunnel was proposed. The test section which could reproduce flow structure, shock wave location, pressure distribution and boundary layer development similar to the obtained on a cascade profile is the main objective of the presented here design. The design of the proposed test section is very challenging, because of shock wave existence, its interaction with boundary layer and its influence on the 3-D flow structure in the test section.
[en] A self-recirculating casing treatment is designed for a transonic compressor stage and its performance at 100% rotational speed is numerically investigated. The casing treatment consists of 9 segments within every rotor blade pitch and each segment is built by one bleed port, one injection port and one bridge channel connecting the bleed and the injection ports. The coupled unsteady flow through the compressor blade passages and the casing treatment is simulated with a state-of-the-art CFD solver TRACE. At the stator-rotor and the treatment-rotor interfaces a conservative zonal approach and a conservative mixed-cell approach are applied, respectively, both of which are in second-order accuracy. The calculated results show that the self-recirculating casing treatment herein is able to effectively extend the stall margin by improving the flow conditions near the casing and by weakening the tip leakage flow. The casing treatment is also found to be able to reduce the incidence to the downstream stator blade near the casing thereby delaying the separation over the stator blade suction surface. (author)
[en] The article presents one optimization method for improving of the working process of an axial compressor of gas turbine engine. Developed method allows to perform search for the best geometry of compressor blades automatically by using optimization software IOSO and CFD software NUMECA Fine/Turbo. Optimization was performed by changing the form of the middle line in the three sections of each blade and shifts of three sections of the guide vanes in the circumferential and axial directions. The calculation of the compressor parameters was performed for work and stall point of its performance map on each optimization step. Study was carried out for seven-stage high-pressure compressor and three-stage low-pressure compressors. As a result of optimization, improvement of efficiency was achieved for all investigated compressors. (paper)
[en] This-paper presents analysis of the flows through three different types of radial compressor by using quasi-three-dimensional analysis method. The method obtains two-dimensional solution for velocity distribution on meridional plane, and then calculates approximately the static pressure distributions on blade surfaces. Finite difference method is used for the solutions of governing equations. The compressors have low level compression-ratio and 12 straight radial blades with no sweepback. The results are compared with experimental data and the results of inviscid analysis with finite element method. It can be concluded that the agreement is good for the cases where viscous effects are not dominant
[en] Complete text of publication follows. The Advanced Radiographic Capability (ARC) on the National Ignition Facility (NIF) is designed to produce energetic x-rays in the range of 10-100 keV for backlighting NIF targets. ARC will convert 4 of the 192 NIF beamlines into 8 split beams, delivering laser pulses with adjustable pulse durations from 1 ps to 50 ps at the kilo-Joule level. Adjustable time delays between the 8 beams enable X-ray 'motion-picture' capture with tens-of-picosecond resolution during the critical phases of an ICF shot. The precise alignment of stretcher-compressor pairs in energetic chirped pulse amplification (CPA) systems is tedious and requires several iterations using advanced temporal diagnostics until the shortest pulse durations and highest peak intensities are achieved. For large, energetic Petawatt laser systems with beam sizes up to 40 cm, diffraction gratings in the compressor reach meter-scale size and are difficult to precisely align. We developed a group delay diagnostic which enables accurate, offline measurements of highly dispersive components such as stretchers or compressors with sub-picosecond accuracy. This diagnostic tool enables us to simply measure each dispersive component offline, and balance the dispersion in each beamline. Furthermore it allows exactly matching the dispersion of ARC's eight, independent four-grating compressors, which is critical for producing eight identical pulses. ARC utilizes a unique, folded compressor design for maximum compactness; two 5.5 m long vacuum vessels house 8 compressors with 91 cm x 45 cm multilayer, dielectric gratings. The group delay diagnostic utilizes the phase-shift technique for measuring the dispersion characteristics of each individual element, e.g. grating stretcher, chirped fiber Bragg grating, grating compressor, material dispersion, or an entire laser system. The system uses an amplitude modulated, highly-stable, single-frequency laser, which is scanned over the spectral bandpass of the system under test. The amplitude modulation generates sidebands at fm = 1-6 GHz, which is detected with a fast photodiode. Using a network analyzer, we measure the phase difference of the modulation-signal, Δθ(vm) between the input and the output detectors as we scan the laser over the spectral pass band of the dispersive system under evaluation. The group-delay can then be derived from the phase difference divided by the modulation frequency. Using the Treacy formalism we can calculate the angle of incidence and slant distance from the group delay curve at a higher precision than what physically can be measured. We have achieved a group delay measurement precision of better than 100 fs, exceeding the ARC requirement of ± 0.5 ps, and which is currently limited by the network analyzer precision and the maximum modulation frequency. In this talk we will describe the dispersion management strategy non ARC, and present the results obtained on the ARC injection laser system test-bed, which utilizes the ARC architecture up to the Joule level. Using this technique we achieved 1.3 J, 1.02 Terawatt with only one iteration-step, equivalent to 78% temporal Strehl ratio. Acknowledgement: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
[en] A three-dimensional computation was conducted to make a study about effects of the inlet boundary layer thickness on the total pressure loss in a low-speed compressor operating at the design condition(φ=85%) and near stall condition(φ=65%). Differences of the tip leakage flow and hub corner-stall induced by the inlet boundary layer thickness enable the loss distribution of total pressure along the span to be altered. At design condition, total pressure losses for two different inlet boundary layers are almost alike in the core flow region but the larger loss is generated at both hub and tip when the inlet boundary layer is thin. At the near stall condition, however, total pressure loss for the thick inlet boundary layer is found to be greater than that for the thin inlet boundary layer on most of the span except the region near hub and casing. Total pressure loss is scrutinized through three major loss categories in a subsonic axial compressor such as profile loss, tip leakage loss and endwall loss using Denton's loss model, and effects of the inlet boundary layer thickness on the loss structure are analyzed in detail
[en] This paper is concerned with the viscous interaction between rotor and stator. The viscous interaction is caused by wakes from upstream blades. The rotor cascade in the experiment was composed with five blades, and cylinders were placed to make the stator wakes and their locations were about 50 percent upstream of blade chord. The locations of cylinders were varied in the direction of cascade axis with 0, 12.5, 25, 50 and 75 percent of pitch length. The static pressure distributions on the blade surfaces and the velocity distributions in the cascade flow were measured. From the experimental result it was found that the value of velocity defect by a cylinder wake might vary depending on the wake position within the cascade but the value at the cascade exit approached to some constant value regardless of the difference of wake locus. The momentum defect at the downstream from the cascade and the pressure distribution on the blade surfaces showed that the wake flowing near the blade surfaces caused the decrease of lift and the increase of drag regardless of the disappearance of flow separation