Finite Element Method for Turbomachinery Flows

Transcription

1 SOCRATES Teaching Staff Mobility Program DMA-URLS Finite Element Method for Turbomachinery Flows Numerical studies on axial flow fan rotor aerodynamics Alessandro Corsini Dipartimento di Meccanica e Aeronautica, University of Rome "La Sapienza" BUDAPEST University of Technology and Economics - 28 November 2000

2 HOW CFD IMPLEMENTS TURBOMACHINERY DESIGN CFD INFLUENCE ON TURBOMACHINERY DESIGN Preliminary design 2D or Q3D concepts Design specifications Turbomachine Numerical model Turbomachine modified geometry NS 3D verification Numerical campaign Numerical investigation CONCERTED EXPERIMENTAL AND NUMERICAL ANALYSIS prototype design objectives UPSTREAM/DOWNSTREAM LDA DATA COMPLEMENTED BY CFD INTERBLADE PREDICTION GUIDELINES FOR IMPROVEMENT OF DESIGN METHOD CFD BASED

3 TEST FAN AND EXPERIMENTAL METHOD (1) NON FREE VORTEX DESIGN BENEFITS HIGH TOTAL HEAD RISE Ψ t = 0.7 AT Φ D = 0.5 DRAWBACKS STRONGER SECONDARY FLOWS root tip r/rc chord (mm) ( l t) D camber radius (mm) TEST FAN ROTOR BLADING CHARACTERISTICS UNTAPERED CIRCULAR ARC CAMBERED PLATE γ D (deg)

4 TEST FAN AND EXPERIMENTAL METHOD (2) EXPERIMENTAL FACILITY LDA SYSTEM (Vad and Bencze, 1996) SINGLE COMPONENT EQUIPMENT MEASUREMENT CELLS DIMENSION UPSTREAM LDA MEASUREMENT PLANE CASING WALL INLET FLOW ROTOR "BUP-29" CASCADE MIDPLANE DOWNSTREAM LDA MEASUREMENT PLANE 3 mm 5 mm 1 NOSE CONE LEADING EDGE TRAILING EDGE a r p 100 COLLECTED DATA CELL ROTOR HUB DISTANCE OF LDA MEASUREMENT PLANES FROM LEADING AND TRAILING EDGES (BASED ON CHORD LENGTH): UPSTREAM DOWNSTREAM AT BLADE ROOT AT BLADE TIP 4.7% BEFORE 10.5% BEFORE 4.7% AFT 10.5% AFT DUCT AXIS

5 NUMERICAL MODELLING OF AXIAL FLOW FAN ROTOR (1) FAN GEOMETRICAL MODELS, H-GRID TOPOLOGIES PINCHED TIP APPROXIMATION COARSE GRID ( ), nodes FINE GRID ( ), nodes EMBEDDED H-GRID COARSE GRID ( ), nodes FINE GRID ( ), nodes casing χ CFD χ blade tip χ CFD = 2.2 mm, modeled clearance χ = 3 mm, rotor clearance (Vad and Bencze, 1996) 3 H-grid topologies: inlet, bladed passage and outlet regions leading and trailing edges tip clearance region

6 NUMERICAL MODELLING OF AXIAL FLOW FAN ROTOR (2) BOUNDARY CONDITIONS INFLOW DIRICHELET CONDITIONS VELOCITY, k AND ε PITCH-WISE AVERAGED LDA VELOCITY DISTRIBUTION TURBULENCE INTENSITY AXY-SIMMETRIC PROFILE (Lakshminarayana, 1982), (Vad, 1999) OUTFLOW NEUMANN CONDITIONS HOMOGENEUS (k AND ε) AND NON HOMOGENEUS p SOLID BOUNDS WALL FUNCTION (WALL SHEAR STRESS, k AND ε ) first grid node 30 <δ+< 200 PERIODIC BOUNDS DEGREES OF FREEDOM EQUALITY

7 Vad and Bencze non free vortex rotor BUP29 LDA measurements "29dbeel.asc" ϕ x0 (R) = Vx/Uc "29dbeel.asc" ϕ r0 (R) = Vr/Uc Upstream pitch-averaged axial and radial flow coefficient distributions

8 U c R T P W S PV ST a) (deg) R P T W S PV ST b) (deg) Axial flow coefficient (ϕ x ) distributions behind the rotor (a: computations, b: experiments (Vad and Bencze, 1996))

9 R T U c P W S PV ST a) (deg) R P T W S PV ST b) (deg) Ideal total head rise coefficient (ψ) distributions behind the rotor (a: computations, b: experiments (Vad and Bencze, 1996))

10 R T U c P W S PV ST a) R T (deg) P W S PV ST b) (deg) Radial flow coefficient (ϕ r ) distributions behind the rotor (a: computations, b: experiments (Vad and Bencze, 1996))

11 Corsini and Rispoli Navier-Stokes prediction obtained with XENIOS finite element code - grid predicted at x = 0.05 l c downstream of rotor hub Vad and Bencze non free vortex rotor BUP29 LDA measurements ϕ 3a ψ 3 ϕ 3r R R R Pitchwise-averaged outlet axial flow and local ideal total head rise coefficient distributions

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