| الوصف: |
This work presents an experimental investigation for the effect s of three - dimensional flow phenomena, which unfold at boundary layer ingestion (BLI) aero - engine intakes of S - shaped geometry, on the performance of a one - stage multi fan compressor unit. The experimental setup consists of two groups of fans: the first one simulates the cruise velocity, while the second one constitutes the compressor unit. Three cases are examined: a straight duct intake as the baseline case and two S - shaped cases. The variable parameter which alters through an inherent mechanism is the length over height ratio (L/H) that characterizes the intake geometry. Oil and dye visualization method is used at the suction area upstream of the compressor unit array for the various intake shapes. Total and static pressure measurements are also performed at the aerodynamic interface plane (AIP) and cross section areas across the intake. This is achieved with a pneumatic five - hole probe which is built and calibrated at the Laboratory of Fluid Mechanics and Turbomachinery of Aristotle University of Thessaloniki (AUTH). The results of the flow visualization, show that the transition of intake geometry from a straight duct towards S - shaped aggressive geometries of decreasing L/H ratios, causes a movement of the saddle points upstream and an enlargement of corner vortices. Pneumatic measurements at various cross - section areas across the S - duct focusing on the central fan, reveal increasing energy losses and verify the existence of counter rotating vortices, especially when the more aggressive intake is used (lower L/H). Additionally, the maximum flow angles are achieved at the most aggressive geometry. The isolation of the suction area of the fan from the flow above it, is the most intense. Furthermore, although distortion effects, are maximized upstream of the compressor array for geometries of higher offset, compression ability of the fan at proximate cross section areas, is not affected as compared to the straight duct. Finally, the significant drop in mass flow rate for the side fans which is associated to the counter rotating vortices, has a major impact on the engine performance. Comparing the performance of the corner fans to that of the central fan, indicates a reduction of more than 20%, for the former.
{"references":["[1] Efstathiadis T., Magkoutas K. I., Ntalianis P. & Kalfas A. I., (2017). 'Geometry Curvature Effect on Boundary Layer Ingestion and Aeroengine Intake Performance', Proceedings of 23rd ISABE Conference, ISABE - 2017 - 22502","[2] European Commission, (2011). 'Flightpath2050 – Europe's Vision for Aviation', Report on the High Level Group on Aviation Research, ISBN 978-92-79-19724-6","[3] Ferrar, A. M. and O'Brien, W. F., (2012). 'Fan Response to Total Pressure Distortions Produced by Boundary Layer Ingesting Serpentine Inlets', 48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and E xhibit and 10th International Energy Conversion Engineering Conference, AIAA, Atlanta, doi: 10.2514/6.2012-3996","[4] Ko, A., Schetz, J. A. and Mason, W. H., (2003). 'Assessment of the Potential Advantages of Distributed - Propulsion for Aircraft', ISABE - 2003 - 1094, Cleveland","[5] Leifsson, L., Andy Ko, William H. Mason, Joseph A. Schetz, B. Grossman, and R. T. Haftka, (2013). 'Multidisciplinary design optimization of blended - wing - body transport aircr aft with distributed propulsion', Aerospace Science and Technology 25, no. 1, 16 - 28, doi: 10.1016/j.ast.2011.12.004","[6] Liebeck R. H., (2004). 'Design of the Blended Wing Body Subsonic Transport, Journal of Aircraft', Vol. 41, No. 1, doi: 10.2514/1.9084","[7] Magkoutas, K. I., Efstathiadis, T. G. & Kalfas, A. I., (2016) . 'EXPERIMENTAL INVESTIGATION OF GEOMETRY EFFECTS AND PERFORMANCE OF FIVE - HOLE PROBE IN MEASURING JETS IN CROSSFLOW', XXII Biannual Symposium on Measuring Techniques in Turbomachinery Transonic and Supersonic Flow in Cascades and Turbomachines","[8] Magkoutas, K. I., Efstathiad is T. G. & Kalfas A. I., (2017). 'Experimental investigation of novel fuel - air premixing device for low NOx combustion', International Journal of Terraspace Science and Engineering 9(2)2017 69 - 77,","[9] NASA Glenn Research Center, (2017). 'Boundary Layer Ingestion Propulsion', https://www1.grc.nasa.gov/aeronautics/bliTest","[10] Sharma, A., (2015). 'Design of Inlet for Boundary Layer Ingestion in a Blended Wing Body Aircraft', Tech. rep., Master Thesis, Faculty of Aerospace Engineering, Delft University of Technology","[11] Terzis, A., Zachos, P., Charnley, B., Pachidis, V., & Kalfas, A. I., (2011). 'On the applicability of oil and dye flow visualization technique during the design phase and operation of experimental rigs', Journal of Flow Visualization and Image Processing, 18, 3, 199 - 214","[12] Treaster A. L., Yocum A. (1978). 'The calibration and application of five - hole probes', ISA Transactions 18 (3)","[13] Welborn, S. R., Reichert, B. A. and Okiishi, T. H., (1992). 'An Experimental Investigation of the Flow in a Diffusing S - Duct', AIAA - 92 - 3622, Nashville"]} |
