André Vouillarmet

Analysis of the Interrow Flow Field Within a Transonic Axial Compressor: Part 1—Experimental Investigation

This paper relates to two-dimensional laser two-focus (L2F) anemometry measurements, conducted in a transonic research high-pressure compressor. Curved glass, which conforms to the shroud contour, was used. The resulting optical distortions of the control volume were corrected using an original and inexpensive optical assembly. Synchronized measurements were performed on two surfaces of the IGV-rotor interrow region. Particular care was taken in evaluating the capabilities of our L2F technique to accurately describe a flow field with strong gradient. The results presented show that the flow field is dominated by the moving oblique shock and its interaction with the IGV wake.

Analysis of the interrow flow field within a transonic axial compressor : Part 2-unsteady flow analysis

An analysis of the experimental data, obtained by laser two-focus anemometry in the IGV-rotor interrow region of a transonic axial compressor, is presented with the aim of improving the understanding of the unsteady flow phenomena. A study of the IGV wakes and of the shock waves emanating from the leading edge of the rotor blades is proposed. Their interaction reveals the increase in magnitude of the wake passing through the moving shock. This result is highlighted by the streamwise evolution of the wake vorticity. Moreover, the results are analyzed in terms of a time-averaging procedure and the purely time-dependent velocity fluctuations that occur are quantified. It may be concluded that they are of the same order of magnitude as the spatial terms for the inlet rotor flow field. That shows that the temporal fluctuations should be considered for the three-dimensional rotor time-averaged simulations.

Analysis of the Inter-Row Flow Field Within a Transonic Axial Compressor: Part 2 — Unsteady Flow Analysis

An analysis of the experimental data, obtained by laser two-focus anemometry in the IGV-rotor inter-row region of a transonic axial compressor, is presented with the aim of improving the understanding of the unsteady flow phenomena. A study of the IGV wakes and of the shock waves emanating from the leading edge of the rotor blades is proposed. Their interaction reveals the increase in magnitude of the wake passing through the moving shock. This result is highlighted by the streamwise evolution of the wake vorticity. Moreover, the results are analyzed in terms of a time averaging procedure and the purely time-dependent velocity fluctuations which occur are quantified. It may be concluded that they are of the same order of magnitude as the spatial terms for the inlet rotor flow field. That shows that the temporal fluctuations should be considered for the 3D rotor time-averaged simulations.Copyright

Experimental Investigation of the Rotor-Stator Interactions Within a High Speed, Multi-Stage, Axial Compressor: Part 1 — Experimental Facilities and Results

This paper relates to laser anemometry measurements (LDA) conducted in a high speed, three-stage, axial compressor. Particular attention has been paid to the estimation of the measurement accuracy. Three different synchronization procedures have been implemented in order to enhance the exactness of the location in the rotating frame for each situation. Small flat windows mainly provide the optical accesses. But, large curved glasses could also be used, the optical distortions resulting from the surface curvature being corrected with the help of an optical assembly developed for the L2F technique and extended to the LDA technique. Furthermore, in order to avoid interpolation processes when changing the frame of reference, the spatial and time discretizations have been defined in accordance with the numbers of rotor and stator blades. The presented measurements have been performed, at 50% blade height, in the first three inter row sections, the azimuthal exploration covering machine periodicity.© 2004 ASME

Experimental Investigation of the Rotor-Stator Interactions Within a High-Speed, Multi-Stage, Axial Compressor: Part 2 — Modal Analysis of the Interactions

The second part of this paper deals with the analysis of the 2D LDA measurements carried out within the high-speed multistage axial compressor CREATE. First the interactions correlations are quantified using the deterministic stresses introduced by Adamczyk. Secondly, a modal decomposition shows that the interactions are characterized by the presence of spatial harmonics (spinning lobes) given by a linear combination of the blades numbers. An original measurement of the rotating speed of the spinning lobes has been carried out allowing to identify almost all the spinning lobes in the first inter row region resulting from the R1-S1 interactions. For the first stage, where the influence of the downstream rows is low, the measured flow field is well reproduced by the model of Tyler and Sofrin. Spatial DFT of the flow field calculated for each time of the compressor time period show that there is a pulsation of the spatial harmonics with the period associated to the minimum elapsed time to recover the same relative positions of the rotor and stator rows.© 2004 ASME

Treatment of L2F anemometer measurement volume distortions created by curved windows for turbomachinery applications

In turbomachinery applications, optical access needed for laser anemometry (L2F) measurements must be provided by curved glass windows to avoid introducing disturbances into the flow. However, the curvatures lead to optical distortions of the laser beams which prevent the creation of acceptable foci. These distortions can be eliminated by inserting a simple and inexpensive corrective window between the frontal lens of the anemometer assembly and the shroud window. First, a simplified analytical method is presented to determine the geometric characteristics and the position of this corrective window. Then, a more sophisticated numerical method is described and applied to the case of an axial transonic compressor currently under investigation.

A Multi-Component and Multi-Disciplinary Student Design Project Within an International Academic and Industrial Collaboration

The design of modern aircraft engines increasingly involves highly sophisticated methodologies to match the current development pace. International company relations affect the collaboration between design offices all around the world. An important part of academic mission of modern engineering education is to produce graduates with skills compatible with industrial needs. Education may readjust accordingly to meet the higher requirements. However, a realistic scenario of the design process of an aircraft engine cannot possibly be transferred one-to-one into the student education process. A unique attempt to overcome this discrepancy was the International Gas Turbine Project. Within this project, undergraduate students have designed the cooling system of the HPT blades for a 30,000 lb thrust two-spool turbofan aeroengine. This project was collaboration between the Jet Propulsion Laboratory of TU Berlin, the Turbomachinery Group of EC Lyon and the Turbomachinery Laboratory of ETH Zurich. It also involved mentoring industry professionals from Rolls-Royce Deutschland, MTU, SNECMA and Alstom Power. Similar to modern aeroengine company structures, the design tasks included multi-component, multi-disciplinary and international interfaces of different educational systems. The student teams considered various aerothermodynamic and mechanical integrity aspects of the design. Particular attention was paid to design of the compressor, the secondary air system and the HP turbine including blade cooling. The three Universities integrated the project differently into their education curriculum and approached the tasks with different levels of software involvement. In this paper, the technical details of the design process, and the different approaches adopted are presented. Besides the application of turbomachinery-related knowledge, the impact of student interactions on the technical aspects of the project is discussed. The interfaces, including information management and the involvement of industrial partners are also addressed. Team spirit developed between the students from an initial competitive behavior to a final feeling of sitting in the same boat. It was observed that increased effort was required from academic staff in comparison to the conventional academic instruction. Nevertheless, students greatly benefited from the social interaction and an early training-on-the-job tuned to current industrial needs.Copyright

Improvements in L2F Anemometry Technique for Inter-Blade Investigations in High-Speed Turbomachinery

This paper presents some problems inherent in the application of a laser two-focus anemometry technique to measurement in high-speed small-scale compressors. Improvements in data processing are described, in relation to reducing the acquisition time. Measurement uncertainties and their possible estimation are discussed. An optimized blade pitch partition during synchronized measurements within rotating blade passages is presented using a prediction of shadow zones. Two examples highlight the resulting benefits both in terms of reduction of the acquisition time and improvement of the azimuthal resolution.Copyright

Laser Two-Focus Anemometry Investigation of the Flow Field Within a Supersonic Axial Compressor Rotor

Laser anemometer measurements have been performed within and downstream of a supersonic single-stage high-pressure compressor. At design point and with standard upstream conditions the maximum relative Mach number varies from 1.3 at the tip to 1.1 at the hub. The stage total pressure ratio is 1.84 and the specific mass flow 180 kg/s/m2. The laser two-focus anemometer has been completely designed in the Laboratory; its originality being the use of a counting technique instead of the classical multichannel analyzer one. The data acquisition and reduction procedures are presented here.A comprehensive evaluation of the global flow-field is in the scope of this paper. For that, the intra-blade flow field is described and the shock pattern is discussed. Furthermore, the experimental results are compared with both inviscid and viscous three-dimensional numerical simulations. The viscous computation is based on the Navier-Stokes solution using a mixing length turbulence model. The good agreement observed in this last case shows off the necessity of taking into account the viscous effects in a supersonic compressor flow calculation.Copyright

Analysis of the Inter-Row Flow Field Within a Transonic Axial Compressor: Part 1 — Experimental Investigation

This paper relates to 2D-laser two-focus anemometry measurements, conducted in a transonic research high pressure compressor. Curved glass, which conforms to the shroud contour, was used. The resulting optical distortions of the control volume were corrected using an original and inexpensive optical assembly. Synchronized measurements were performed on two surfaces of the IGV-rotor inter-row region. Particular care was taken in evaluating the capabilities of our L2F technique to accurately describe a flow field with strong gradient. The results presented show that the flow field is dominated by the moving oblique shock and its interaction with the IGV wake.Copyright