Integrating CFD and Experiment in Aerodynamics - CFD4Aircraft

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Cs 4m Embankment Side Force Coefficient ( Cs) CFD Exp 0 20 40 60 80 100 Yaw angle(deg) Fig. 13. Side force coefficient vs. yaw angle: BMT experiment, Re=2.5*10 5 , 4m embankment. Cm 4m Embankment Rolling Moment Coefficient ( Cm) CFD Exp 0 20 40 60 80 100 Yaw angle(deg) Fig. 14. Coefficient of rolling moment about lee rail vs. yaw angle: BMT experiment, Re=2.5*10 5 , 4m embankment. CFD turbulence intensity 3%. Fig. 15. Flow over train on 4m embankment.
Investigation of Flow Turning in a Natural Blockage Thrust Reverser S. Hall, R.K. Cooper, E. Benard, S. Raghunathan School of Aeronautical Engineering, Queen's University Belfast David Keir Building, Stranmillis Rd, Belfast BT9 5AG, UK s.l.hall@qub.ac.uk, r.cooper@qub.ac.uk, e.benard@qub.ac.uk, s.raghunathan@qub.ac.uk Keywords: Thrust Reverser, Internal Flow Abstract: Experimental and computational low speed tests have been conducted on a 50% scale model of a twodimensional natural blockage fan flow cascade thrust reverser. The aim of the work is to provide a reference database for future work investigating innovative flow control in fan flow thrust reversers. Results are presented for a reverser with cascade solidity = 1.3. The experimental nozzle pressure ratio must be increased to obtain relevant quantitative data. In addition the 2D computational results highlight problems of simulating a flow with 3D effects. Introduction Virtually all modern jet transport aircraft incorporate thrust reverser systems which are primarily used to provide an extra safety margin during landings and aborted take offs 1 . Thrust reversers operate by redirecting the engine exhaust flow forwards to produce a braking force. Unlike wheel braking systems their performance is not degraded by wet/icy runway conditions. Several types of thrust reverser are in operation today however this paper considers only the natural blockage cascade type fan flow thrust reverser which is used on the CF-34-8C powerplant of the Bombardier Aerospace CRJ-700/900 Regional Jet aircraft. The nacelle fan duct of the CF-34- 8C engine is S-shaped. When the thrust reverser is deployed the rear section of the nacelle cowling translates aft to naturally block the fan duct whilst simultaneously exposing the reverser cascade opening in the side of the nacelle 2 . The fan flow is blocked and diverted outwards through the cascade opening where the cascade vanes deflect it forwards to produce the reverse thrust efflux (see figure 1). It may be possible to use partial-cascade or cascadeless flow turning to achieve similar levels of reverse thrust. In the long term it may even be possible to design a thrust reverser with no moving parts which is essentially blockerless and cascadeless. Such a design would yield advantages in terms of reduced weight, reduced activation time and reduced leakage and pressure losses in the nacelle. The removal of the cascade from the system will necessitate its replacement with innovative fluidic flow control to ensure that flow turning through the reverser is maintained. Before investigating this possibility it is important to first understand the flow in the conventional natural blockage thrust reverser. This paper presents results from recent experimental and numerical studies of flow through a conventional natural blockage thrust reverser conducted at Queen's University Belfast. These studies form the basis to ongoing research within the school into innovative flow control in thrust reversers. Methodology The wind tunnel has a constant speed fan motor and the flow velocity can be set by partially blanking the fan inlet duct. Downstream of the fan there are four gauze screens for flow smoothing and a two-dimensional contraction section of contraction ratio 0.24. Following the contraction is the test section which measures 380mm by 89mm in cross-section. The maximum velocity in the test section is approximately 20m/s. The experimental model is a 50% scale two-dimensional simplified geometry representing the CF-34-8C thrust reverser in its deployed state. The cascade vanes are of constant thickness with blunt leading and trailing edges and have a design discharge angle of 45 0 . The blocker surface is modelled as a simple flat plate (see figure 2). In a cross-sectional plane located at 125mm from the duct entrance six static pressure tappings are arranged in the duct walls with even spacing (two per wall). A total pressure rake consisting of thirteen probes is mounted in a sliding traverse in the duct roof. The rake vertically spans the duct and can be moved manually across the duct by means of the traverse. The constant cross-section duct is connected to the thrust reverser model by a set of bellows so that force measurements may be made on the reverser model at a later date. An exit pressure rake consisting of 26 probes (6 static probes, 19 total pressure probes and 1 directional alignment probe) 3 is mounted spanwise above the exit plane of the cascade. It can be manually rotated about its main centreline and using the alignment probe can be set to the local exit flow direction. The rake attachment consists of two slotted bars mounted on a
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Experimentalist’s requirements fo
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persistent discrepancy may be due t
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numbers significantly lower than th
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Heat flux measurements. Over the pa
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The measurements are made on select
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advantage that the signal is emitte
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12. Mébarki, Y. and Mérienne, M.
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castellated nozzles entrained more
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Axisymmetric Regular Convergent Div
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Figure 5: Typical instantaneous PIV
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Figure 8: Streamwise Velocity Profi
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1.25 CFD (SKW PRESTO) Experimental
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Page 83 and 84: Figure 1. Natural Blockage Thrust R
Page 85 and 86: Figure 7. Post-Exit rake Total Span
Page 87 and 88: Figure 11. Comparison of Static Pre
Page 89 and 90: 2.2 Data Aquired The Embedded Laser
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Page 97 and 98: Figure 5: Influence of the pseudo t
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