Proceedings of ASME Turbo Expo 2014 June 16
Proceedings of ASME Turbo Expo 2014, June 16 – 20, 2014, Düsseldorf, Germany, GT 2014 -26443 DEVELOPMENT & INTEGRATION OF RAIN INGESTION EFFECTS IN ENGINE PERFORMANCE SIMULATIONS I. Roumeliotis – A. Alexiou – N. Aretakis – G. Sieros – K. Mathioudakis LABORATORY OF THERMAL TURBOMACHINES National Technical University of Athens, Greece
SCOPE Develop a multi-fidelity & multi-physics engine performance model for engine level rain ingestion simulation ØDevelop appropriate physical consistent models of suitable fidelity for simulating the effects of rain ingestion on components performance ØIntegrate rain ingestion effects models in an engine performance simulation environment developing suitable components and interfaces ØUse these components to build a whole engine model and simulate rain ingestion under specific operating conditions Ø Inclusion of suitable calibration parameters for physical processes and component models if data from higher fidelity models and experiments are available GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 2
SCOPE Develop a multi-fidelity & multi-physics engine performance model for engine level rain ingestion simulation ØPreliminary analysis of rain ingestion effects on engine operability and performance during pre-design phase ØEfficient planning and running of engine tests ØCalibrated engine/component models can be used for critical point analysis & extrapolation of ground test results to altitude conditions Ø Calibrated engine model can be used for evaluating existing hardware, control & hardware modifications GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 3
CONTENTS q Introduction q Droplet Models q Modelling Rain Ingestion Effects • • • Scoop Effect Fan Effect VBVs Effect Compression Effect Combustor Effect q Engine Performance Modelling q Rain Ingestion Test Case • Critical Point Analysis q Summary-Conclusions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 4
DROPLET MODELS Droplet trajectories: Droplet trajectories (3 -D) calculated using the Lagrangian equations of motion considering gravity and drag forces. The trajectory equations are expressed using cylindrical polar coordinates solved in conjunction with a given gas flow field GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 5
DROPLET MODELS Droplet break up model: Exploiting Semi-Empirical Correlations for categorizing breakup and predicting secondary droplet diameters after break up as a function of: ØWebber Nr ØTime ØViscosity Pilch M. , Erdman C. A. , 1987, “Use of Breakup Time Data and Velocity History Data to Predict the Maximum Size of Stable Fragments for Acceleration-Induced Breakup of a Liquid Drop” Schmehl R. , Klose G. , Maier G. , Witting S. , 1998, “Efficient Numerical Calculation of Evaporating Sprays in Combustion Chamber Flows” GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 6
DROPLET MODELS Droplet impact: Exploiting Semi-Empirical Correlations for categorizing droplet-surface interaction and predicting secondary droplet diameters if splashing occurs as a function of: ØImpact Webber Nr ØSplashing Parameter ØFilm Thickness Stanton D. W. ; Rutland C. J. , 1998, “Multi-dimensional Modeling of Thin Liquid Films and Spray-wall Interactions resulting from Impinging Sprays” Schmehl R. ; Rosskamp H. ; Willmann M. ; Wittig S. , 1999, “CFD Analysis of Spray Propagation and Evaporation Including Wall Film Formation and Spray/Film Interactions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 7
DROPLET MODELS Water Film: Film thickness is calculated assuming it behaves as a single phase turbulent boundary layer with a universal velocity profile. Heat and mass transfer calculations are undertaken for specified film temperature (Tfilm=Twb, local) Whalley P. B. , 1987, “Boiling, Condensation and Gas-liquid Flow” Matz C. , Kappis W. , Cataldi G. , Mundinger G. , Bischoff S. , Helland E. , Ripken M. , 2008, “Prediction of Evaporative Effects within the Blading of an Industrial Axial Compressor” Zhluktov S. V. , Bram S. , De Ruyck J. , 2001, “Behaviour of an Axial Compressor with Water Injection” GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 8
DROPLET MODELS Droplet Evaporation: Droplet Evaporation heat and mass transfer model accounting forced convection (“velocity slip”) Evaporation rate for stationary droplets Evaporation rate for Velocity slip: Dd 0=1790μm, Rerel=116 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 9
CONTENTS q Introduction q Droplet Models q Modelling Rain Ingestion Effects • • • Scoop Effect Fan Effect VBVs Effect Compression Effect Combustor Effect q Engine Performance Modelling q Rain Ingestion Test Case • Critical Point Analysis q Summary-Conclusions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 10
Water Ingestion Effects on Engine Performance Burner Effect Scoop Effect VBVs Effect Fan Cone Effect Compression Effect Fan effect Evaporation & Impingement GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 11
MODELS for SIMULATING RAIN INGESTION EFFECTS Scoop Effect: Evaluation of water content and droplet properties at the engine inlet using a 2 -D Euler Model for air flowfield calculations and solving the appropriate droplet models (droplet trajectories and break up) SF=Ah/AC GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 12
MODELS for SIMULATING RAIN INGESTION EFFECTS Fan Effect: Evaluation of impingement and water properties (droplets diameter, velocities, position and distribution) at the fan outer utilizing meridional and blade-to-blade flow calculations for evaluating the flowfield in a 3 -D way. The flowfield is coupled with the appropriate droplet models (droplet trajectories, droplet breakup, droplet-surface interaction) GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 13
MODELS for SIMULATING RAIN INGESTION EFFECTS Fan Cone Effect GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Fan Effect Page 14
MODELS for SIMULATING RAIN INGESTION EFFECTS Variable Bleed Valve Effect: Evaluation of water properties at the ducts utilizing 1 -D duct model extended to pseudo 3 -D fully coupled with all droplet models (droplet trajectories, break-up, impact, film, evaporation). The percentage of the casing film (or total water content) removed relative to the VBVs opening position is evaluated by using a simple parametric table Effect of LPC Stability Bleed on core water content AGARD-AR-332, 1995, “Recommended Practices for the Assessment of the Effects of Atmospheric Water Ingestion on the Performance and Operability of Gas Turbine Engines” GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 15
MODELS for SIMULATING RAIN INGESTION EFFECTS Compression Modelling (1 D): ØAerodynamic Stages Performance evaluated via stages characteristics ØGaseous flowfield is transformed to pseudo 3 -D way expanding the 1 -D calculated data ØAll Droplet Models are solved for the pseudo 3 -D gas flowfield fully coupled ØFor blade to blade calculations pseudoblades with the same shape as the gas-phase streamlines are constructed ØThe water retained on rotor blades is assumed to be centrifuged to the casing GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Dd=5μm Dd=15μm Page 16
MODELS for SIMULATING RAIN INGESTION EFFECTS Evaporation Effect (Compression) GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 17
MODELS for SIMULATING RAIN INGESTION EFFECTS Burner Effect: The macroscopic effects of water ingestion are a decrease of combustor efficiency and an increase of pressure losses. The model assumes 0 -D isenthalpic evaporation using experimental published data to account for the reduction in burner efficiency and increase of pressure losses GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 18
CONTENTS q Introduction q Droplet Models q Modelling Rain Ingestion Effects • • Scoop Effect Fan Effect Compression Effect Combustor Effect q Engine Performance Modelling q Rain Ingestion Test Case • Critical Point Analysis q Summary-Conclusions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 19
MODELS INTEGRATION AT ENGINE LEVEL PROOSIS Ø Object-Oriented Ø Steady State Ø Transient Ø Mixed-Fidelity Ø Multi-Disciplinary Ø Distributed Ø Multi-point Design Ø Off-Design Ø Test Analysis Ø Diagnostics Ø Sensitivity Ø Optimisation Ø Deck Generation Ø Connection with Excel & Matlab Ø Integration of FORTRAN, C, C++ GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 20
MODELS INTEGRATION AT ENGINE LEVEL Engine Performance Model: ØIntegration of models for rain ingestion effects (developed in Fortran) in PROOSIS (as functions) ØDevelopment of two-phase flow interface (Port) for transferring water (and gas) info ØDevelopment of engine components with rain simulation capability in a new library that associates with the standard library GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 21
CONTENTS q Introduction q Droplet Models q Modelling Rain Ingestion Effects • • • Scoop Effect Fan Effect VBVs Effect Compression Effect Combustor Effect q Engine Performance Modelling q Rain Ingestion Test Case • Critical Point Analysis q Summary-Conclusions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 22
RAIN INGESTION TEST CASE Test Case Engine: ØA generic high bypass Turbofan Ø 0 -D conventional engine model for establishing design data ØPreliminary components design calculations for the higher fidelity models required data Parameter To. C BPR 4. 71 OPR 23. 7 W 1 [kg/s] 126. 5 SFC [g/(k. Ns)] 19. 0 FN [N] 22000 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 23
RAIN INGESTION TEST CASE VBVs closed Parameter GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Descent (dry) BPR 6. 83 OPR 9. 26 W 1 [kg/s] 127. 64 SFC [g/(k. Ns)] 24. 02 FN [N] 7211 Page 24
OPERATING POINT ANALYSIS GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 25
OPERATING POINT ANALYSIS GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 26
OPERATING POINT ANALYSIS VBVs closed GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 27
OPERATING POINT ANALYSIS Surge Margin Reduced by 45% GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 28
OPERATING POINT ANALYSIS Parameter Tt 31 [K] Dry Rain % Diff 550 424 -22. 8 5. 26 5. 51 4. 87 0 5. 4 Burn. Th. Eff (%) 99. 95 70. 67 -29. 5 WF [g/s] 173. 2 256. 3 48 W 4 [kg/s] 13. 38 15. 29 14. 3 1043 896 -14. 1 Pt 31 [bar] War 31(%) Tt 4 [K] GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 29
OPERATING POINT ANALYSIS Parameter Dry Rain % Diff BPR 6. 83 6. 52 -4. 54 OPR 9. 26 9. 71 4. 86 W 1 [kg/s] 127. 64 127. 3 -0. 27 Fan PR [-] 1. 218 1. 211 -0. 57 Booster PR [-] 1. 167 1. 146 -1. 79 HPC PR [-] 6. 605 7. 072 7. 07 LP Nspeed [rpm] 2974 2943 -1. 06 HP Nspeed [rpm] 11726 11172 -4. 72 Burn. Th. Eff (%) 99. 95 70. 67 -29. 3 WF [g/s] 173. 2 256. 3 48 SFC [g/(k. Ns)] 24. 02 35. 54 48 EPR [-] 0. 883 0. 895 1. 36 FN [N] 7211 - GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Surge Margin is halved Fuel Flow is Doubled Page 30
Rain Ingestion Engine Simulation Parametric Analysis of Ingested Water Content: GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 31
CONTENTS q Introduction q Droplet Models q Modelling Rain Ingestion Effects • • • Scoop Effect Fan Effect VBVs Effect Compression Effect Combustor Effect q Engine Performance Modelling q Rain Ingestion Test Case • Critical Point Analysis q Summary-Conclusions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 32
SUMMARY üDeveloped physical consistent (multi-physics) models for simulating water ingestion effects relevant to engine performance analysis üIntegrated models in a conventional engine performance simulation environment üMixed-fidelity components (0 D, 1 D, 2 D) engine model üSimulated steady-state operation of an engine under rain ingestion conditions GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 33
CONCLUSIONS ØScoop and Inlet effect result to a significant droplet break-up ØMost of the droplets will impinge on the fan and centrifuged to the bypass duct ØIntensive splashing in Fan will result to the ingestion of relatively small droplets in the core ØMore than 50% of core water is in the form of film in the swan-neck duct ØEvaporation is intense in the High Pressure Compressor ØHP Turbine-Compressor rematching and compressor evaporation effect result to the significant decrease of surge margin. ØMore than 60% of core water reaches the combustor decreasing its efficiency and increasing the fuel flow needed to maintain thrust by 50% GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 34
FUTURE WORK v. Integrate the control system responses (VBVs, VSVs schedules and fuel margin) v. Further enhance specific component models (computation of film movement on fan blades and cone) v. Examine the information that lower fidelity models can give compared with the higher fidelity models v. Perform experiments on a fan test facility for validation and calibration GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 35
ACKNOWLEDGEMENTS Collaborative & Robust Engineering using Simulation Capability Enabling Next Design Optimisation GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 36
DROPLET MODELS Droplet trajectories: Droplet trajectories (3 -D) calculated using the Lagrangian equations of motion considering gravity and drag forces. The trajectory equations are expressed using cylindrical polar coordinates solved in conjunction with a given gas flow field GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 37
DROPLET MODELS Droplet trajectories: Droplet trajectories (3 -D) calculated using the Lagrangian equations of motion considering gravity and drag forces. The trajectory equations are expressed using cylindrical polar coordinates solved in conjunction with a given gas flow field GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 38
DROPLET MODELS Droplet break up model: Exploiting Semi-Empirical Correlations for categorizing breakup and predicting secondary droplet diameters after break up Break up process Critical Webber Nr Bag Breakup 12 • (1+1. 077 On 1. 6) Transition to multimode 20 • (1+1. 20 On 1. 6) breakup Transition to shear breakup 32 • (1+1. 5 On 1. 4) GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 39
DROPLET MODELS Droplet impact: Exploiting Semi-Empirical Correlations for categorizing droplet-surface interaction and predicting secondary droplet diameters if splashing occurs Phenomenon Webber Nr Sticking Rebounding Spreading Splashing We<5 5<We<10 10<We - GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Splashing parameter (S) S<1 S<1 S>1 Page 40
DROPLET MODELS Water Film: Film thickness is calculated assuming it behaves as a single phase turbulent boundary layer with a universal velocity profile. Heat and mass transfer calculations are undertaken for specified film temperature (Tfilm=Twb, local) for tf+<5 for <tf+<30 tf+>30 laminar sub layer: buffer layer: turbulent core: for tf+<5 for <tf+<30 tf+>30 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 41
MODELS for SIMULATING RAIN INGESTION EFFECTS Scoop Effect: The calculation is based on a simplified geometry consisting of a rectangular region, where the inlet is modeled through the imposed static pressure at the engine inlet, allowing for the computation of the flow streamlines. A 2 -D Euler Method is used to model the flow before the engine. The method used is based on an explicit time-marching solution algorithm utilizing a classic 4 stage Runge-Kutta method for the time discretisation and central differences with 2 nd and 4 th order dissipation terms for the space discretisation. In order to model the presence of the inlet, a variable static pressure distribution is enforced at the grid exit, with atmospheric pressure at the outer region and the pressure corresponding to the prescribed mass flow at the central section. Giannakoglou K. C. , Simantirakis G. , Papailiou K. D. , 1991, “Turbine Cascade Calculations Through a Fractional Step Navier-Stokes Algorithm”, ASME paper No. 91 -GT -55 Papailiou K. D. Sieros G. , Vassilopoulos Ch. , Chen N. X. , Huang W. C. , 1999, “Numerical Study on the 3 -D Viscous Flow in a Centrifugal Compressor Impeller with and without Consideration of Tip Clearance”, ISABE paper No. 99 -7268 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 42
MODELS for SIMULATING RAIN INGESTION EFFECTS Scoop Effect: For the flow before the inlet a simplified geometry in order to have a generic method that does not need the exact geometry of the particular engine. This means that we can not have an accurate estimate of the losses before the inlet, but this is not important in this application. An iterative procedure is used to derive the static pressure that gives the required total mass flow. Giannakoglou K. C. , Simantirakis G. , Papailiou K. D. , 1991, “Turbine Cascade Calculations Through a Fractional Step Navier-Stokes Algorithm”, ASME paper No. 91 -GT -55 Papailiou K. D. Sieros G. , Vassilopoulos Ch. , Chen N. X. , Huang W. C. , 1999, “Numerical Study on the 3 -D Viscous Flow in a Centrifugal Compressor Impeller with and without Consideration of Tip Clearance”, ISABE paper No. 99 -7268 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 43
MODELS for SIMULATING RAIN INGESTION EFFECTS Fan Effect: For evaluating the inlet flow field in a 2 -D way a numerical method based on the peripherally averaged flow equations is used for the meridional flow calculation. Also a pitchwise expansion of the mean quantities is performed (blade to blade). In order to do that the pressure difference on the blade is calculated based on the work required for the change in momentum along a streamline. A linear variation of the pressure is assumed from pressure to suction side and the other quantities are then easy to estimate. This is a rough approximation, but results have shown that small peripheral variations in pressure/velocity have little effect on the droplet trajectory. A meridional grid is created, using an elliptic grid generator with stretching near hub and tip. Kiousis P. , Chaviaropoulos P. , Papailiou K. D. , 1992, “Meridional Flow Calculation Using Advanced CFD Techniques”, ASME paper No. 92 -GT-325 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 44
MODELS for SIMULATING RAIN INGESTION EFFECTS Fan Effect: Kiousis P. , Chaviaropoulos P. , Papailiou K. D. , 1992, “Meridional Flow Calculation Using Advanced CFD Techniques”, ASME paper No. 92 -GT-325 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 45
MODELS for SIMULATING RAIN INGESTION EFFECTS GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 46
FAN OPERATION GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 47
BOOSTER OPERATION GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 48
HPC OPERATION GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 49
COMPRESSOR – EVAPORATION EFFECT • Compressor (evaporation): The model uses a stage-stacking scheme to account for droplet-gas phase heat, mass and momentum exchange, stage characteristics shift (applying experimental data) and re-matching, droplet surfaces interaction and film creation D=5μm D=15μm GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 50
COMPRESSOR – EVAPORATION EFFECT GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 51
COMPRESSOR – EVAPORATION EFFECT GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 52
ROTOR & STATOR WATER BEHAVIOUR GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 53
ROTOR & STATOR WATER BEHAVIOUR GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 54
ROTOR & STATOR WATER BEHAVIOUR Data from: “Water Film Formation on an Axial Flow Compressor Rotor Blade”, Nikolaidis, Pilidis, ASME paper No. GT 2008 -50137 GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 55
RAIN INGESTION in AEROENGINES ØSeveral incidences where engines have lost power in rain storm or hail conditions have been reported ØThe power loss may be the result of flameout, rollback with loss of rotor speed to below idle conditions and of compressor stall ØFederal Aviation Administration published new certification standard GT 2014 -26556 Development & Integration of Rain Ingestion Effects in Engine Performance Simulations Page 56
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