Pumping Machinery 2001 ASME Fluids Engineering Division Summer Meeting Dr. Adiel Guinzburg What is Turbomachinery? Using working fluids to Boost output, either increase or decrease pressure by using Machinery Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 High Pressure Fuel Turbopump Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 High Pressure Oxygen Turbopump Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Turbomachine Classification • Turbines. Pumps and Compressors • Incompressible. Compressible • Axial-flow, Mixed-flow, Radial-flow geometry • Single stage. Multi-stage • Turbo-pump. Turbo-compressor. Torque-converter • Impulse. Reaction Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 From Customer Requirements to Final Product • Specification • Preliminary Design, Conceptual design, ... • Component Design • Component Test, Analysis • Acceptance Test • ..... Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Design Trade-offs • Performance • Weight • Cost •Life • Reliability • Structural Strength • Maintainability • Envelope Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Design Process • In-house design database - scale • Detail design – (2D, Quasi 3D, CFD <=> stress analysis • Test Data Evaluation Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Turbomachine v2 v2 Ps = m& [(h + + gz)out − (h + + gz)in ] 2 2 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Turbines • Impart Kinetic Energy to rotor as Mechanical Energy of rotation •Impulse – high Pressure, low Flow • Reaction – low Pressure, high Flow Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Pump Classification Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Centrifugal Pump • rotor, stator – accelerate flow by imparting kinetic energy – decelerate (diffuse) in stator – results in increase in fluid pressure Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Elements of a Centrifugal Flow Pump • From Huzel, D. K. and Huang, D. H. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Rotor • Inducer • Impeller • Bearings •Shaft Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Inducer • Axial flow • Increase total pressure • permits non cavitating operation in impeller • used as boost pump, permits main pump to operate at higher speeds • e.g. LPOTP is only inducer Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Inducer Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Stator •Casing • Diffuser vanes • Volute • Seals Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Vane Island Diffuser (shown without shroud) Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Impeller Profiles From BWIP pump pocket book • Radial Flow Mixed Flow Axial Flow Ns Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Pump Configurations • From Huzel, D. K. and Huang, D. H. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Velocity Triangle • From Huzel, D. K. and Huang, D. H. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Velocity Triangle • From Huzel, D. K. and Huang, D. H. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Impeller Loss Components • Skin Friction • Blade Loading • Incidence • Wake Mixing • Impeller-shroud Clearance Leakage • Disk Friction • Recirculation Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Flow Variables 1 2 PT = P + 2 ρv 1 P = P + ρ (v 2 +v 2) T 2 θ m 1 h = h + ρv2 + gz T 2 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Dimensionless Quantities • Head coefficient gH Ψ = Ω2R 2 • Flow Coefficient Q Φ = AΩR Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Head rise u H = (v − v ) g θ 2 θ1 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Isentropic Enthalpy Rise ∆H=144.∆p/ρ ∆P (psi) ∆H (ft) ρ(lb/ft3) Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Affinity Laws •Q ~ ΩD3 •H ~ Ω2D2 •T ~ ρΩ2D5 •P ~ ρΩ3D5 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Engine System Resistance and Pump Characteristics • From Huzel, D. K. and Huang, D. H. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Specific speed 1 ΩQ 2 • Consistent units Ωs = 3 (gH) 4 – Ω (rad/s) –Q (m3/s) –H (m) 1 RPM.(GPM) 2 Ns •US Ns = Ωs = 3 2734.6 (ft.) 4 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Impeller Profiles From BWIP pump pocket book • Radial Flow Mixed Flow Axial Flow Ns Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Effect of Ns on H-Q curve • From Cameron Hydraulic Data Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Profiles and Efficiencies Based on Specific Speed Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Issues • H-Q instability • Stall • Cavitation induced dynamic pressure • Radial loads • Discharge and suction recirculation Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Separation and Stall Jet and wake observed in each impeller passage. The eddying wake is seen on the suction side of the channel from Fischer and Thoma, 1932 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Recirculation Secondary flows in a centrifugal pump from Brennen (1994) Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Recirculation Sudden increase in pressure pulsation from Fraser (1981) Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Stator Effect on Head Characteristics (steepens H-Q curve) • reduce impeller inlet Cu at low flow • increase impeller inlet Cu at high flow • provide stability over wide operating range • increase stator and impeller incidence angle at off design • reduces inception of stall with negative incidence Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Vaned Diffuser Effect on Head Characteristics (flattens H-Q curve) • convert kinetic energy of fluid leaving the impeller into static pressure rise • flow incidence sensitive • leading edge stall phenomenon believed to be cause of loss of diffuser performance • rapid head falloff at low flow Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Stall Characteristics 1.4 1.2 s de d Diffuser stall a 1 e Impeller stall Stator stall H p 0.8 m /Pu WFR d 0.6 a e no stall H p 0.4 m no diffuser stall Pu 0.2 no stator stall 0 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 Flow/Flow des Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Two-Dimensional Diffuser Map Flow Regimes in Straight Wall, Two-Dimensional Diffusers from Moore and Kline, 1955. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Slot Optimization Slot geometry configuration optimization from Gostelow and Watson, 1972. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Blade Loading From Guinzburg et al. (1997) Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 CFD as a Tool • Before using a particular CFD code in a rotating machinery component design process, it is important to bracket the accuracy of the code results for that particular type of component. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Interpretation of CFD • Another important issue is how accurately the component inlet flow boundary conditions have to be known (pre- computation) to get results that are consistent with test data. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 CFD Process • Validate a computational fluid dynamic code for integration into the impeller design process. • The validation process consists of computing the impeller flow for a range of inlet conditions. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Accuracy of the CFD Results • number of nodes used to discretize the flow domain • accuracy of the numerical discretization scheme • type of turbulence model used. Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 CFD Capabilities • Transient Analysis • Two Phase Flow • Heat Transfer • Temperature Dependent Properties • Moving Mesh • Non-inertial Reference Frames • Selection of Turbulence Models • Wall Function Models Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Diffusion The diffusion factor D, can be adapted for pumps from Lieblein (1965) as follows: r1 Vθ 2 − Vθ1 W2 r2 D = 1- + W1 2σW1 Duncombe (1964) explicitly examined the diffusion on both the suction (s) and pressure (p) sides of the blade and expressed the result as follows: W W 2 p,min D = 1- + 1- Ws,max W1 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Cavitation Typical cavity configuration within an impeller. Flowrate is half that of BEP; so, the cavity is broken up by recirculating flow. From Sloteman et al (1995). Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Cavitation • Thoma number, cavitation number p - p σ = v 1 2 2 ρv Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Suction Specific speed 1 ΩQ 2 • Consistent units Ωss = 3 (gNPSH) 4 – Ω (rad/s) –Q (m3/s) –NPSH (m) 1 RPM.(GPM) 2 Nss •US Nss = Ωss = 3 2734.6 (ft.) 4 Fluids Engineering Division Annual Summer Meeting, New Orleans, LA, 29 May 2001 Pump Suction Performance • From Huzel, D. K. and Huang, D. H.