29119_VB_PES_GT-Suite-Coference.ppt Vincenzo Bevilacqua, PE-AB Potential of Turbocharging 11.12.28 Seite 1 von 24
29119_VB_PES_GT-Suite-Coference.ppt Vincenzo Bevilacqua, PE-AB Potential of Turbocharging 11.12.28 Seite 2 von 24
GT-Suite User Conference Frankfurt, 9 November 29 Potential of turbocharging in SI Engines: a 1D CFD based analysis Vincenzo Bevilacqua (PEG-M) Gerd Grauli (PEG-G) 29119_VB_PES_GT-Suite-Coference.ppt Vincenzo Bevilacqua, PE-AB Potential of Turbocharging 11.12.28 Seite 3 von 24
Introduction Goal of the Work: Analyze the performance critical parameters and highlight the potential of turbocharging in SI Engine Evaluate the potential of alternative turbocharging concepts Methodology:. Modeling of the phenomena which limit the performances of a SI turbocharged engine Investigation of potential of single stage turbocharging Analysis of alternative turbocharging concepts Comparison of the concept under transient conditions 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 4 von 24
Single Stage Turbocharging: Modeling Modeling the performance relevant phenomena which limit the torque curve Introduction full load 1 1 Cylinder pressure knocking 5 RPM L am b d a [--],95,9,85,8,75 8 6 4 2 T3 [ C ] CADeg after TDC Torque [Nm] Knock Compressor Max. Torque Component Protection Compressor,7 1 2 3 4 5 6 Engine Speed [RPM] Engine Speed [1/min] Surging n max Choking 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 5 von 24
29119_VB_PES_GT-Suite-Coference.ppt Single Stage Turbocharging: Modeling Compressor Controller Surge limit Chock limit Maximum compressor speed Lambda Controller Exhaust temperature under the threshold value If the lambda value decreases under a prescribed limit then Boost Pressure is reduced Spark Advance Thermodynamic optimum Knock onset If the spark advance is reduced under a certain limit, then boost pressure is reduced, as in happened in the ECU Methodology based on Livingood Wu Integral and validated against experimental data P5 [ CADeg after TDC] 2 16 12 8 4 Surging 2 CADeg Choking Messung Measurament 9A1 Simulation 1 2 3 4 5 6 7 Engine Speed [RPM] 9.11.29 Potential of Turbocharging Seite 6 von 24 n max
Single Stage Turbocharging: Modeling Implement the different model it is possible to identify for a given engine and turbine/compressor pair the maximum achievable output P Power [kw] [kw] 24 16 8 6 4 2 M Torque [Nm] [Nm] The performances of turbo SI engines are limited by several phenomena: they have to be taken into account when choosing turbine compressor pair. Turbine Inlet T3 Temperature [K] [K] BSFC Be [g/kwh] 13 15 8 42 32 22 1 2 3 4 5 6 7 Engine Drehzahl Speed [1/min] [RPM] 1.5.85.65 3 15 P5 SWP [ CADeg [ KW a. n. TDC] OT] Lambda [--] Pressure Ratio [-] Turbine Power Knock Reduced Massflow [(kg/s)-k^.5/kpa] Max T3 Compr. Speed 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 7 von 24
Power Leistung Turbinen [kw] [kw] Massenstromverhältnis Flow Multiplier [-] [--] Single Stage Turbocharging: Potential A procedure has been developed to scale turbomachine maps Scaling turbine and compressor size it is possible to highlight the trade-off between high low-end torque and max power Turbomatching determines the rpm range where the engine can be used (drivability) 1.2 1.1 1. 2 175 15.9 125 1 Knock Drehmoment Torque [Nm] [Nm] 15 15 1/min RPM 21. 19. 2. 18. 175. 75 22. 15 23..8 5 24. 1.8.9 1. 1.1 1.2 25 5 Verdichter Compressor Massenstromverhältnis Flow Multiplier [--] [-] 25 Nm Low-End Torque Version Surge Limit 1 2 3 4 5 6 7 Engine Drehzahl Speed [1/min] [RPM] 4 35 3 25 2 Drehmoment Torque [Nm] [Nm] Turbinen Massenstromverhältnis Flow Multiplier [-] [--] 1.3 1.2 1.1 1. 155..9 5. 16. Leistung Power [kw] 2 165. Leistung Power [kw] [kw] 6 RPM 1/min 175 15 125 1 75 5 25 19. 1 2 3 4 5 6 7 18. Engine Drehzahl Speed [1/min] [RPM] 17. 175. 185. Maximum Power Version Compressor Speed Max. T3 19 kw.8.8.9 1. 1.1 1.2 1.3 Verdichter Compressor Massenstromverhältnis Flow Multiplier [--] [-] 4 35 3 25 2 15 1 5 Drehmoment Torque [Nm] [Nm] 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 8 von 24
Single Stage Turbocharging: Potential The diagrams show the trade-off between performance at high speed and low end torque performances According to the target, some turbine-compressor pairs represents optimal compromise Torque at 15 rpm [Nm] 27 25 23 21 19 17 15 145 155 165 175 185 195 Pow er at 6 rpm [kw] Mass Flow Multiplier =.8 Mass Flow Multiplier =.9 Mass Flow Multiplier = 1 Mass Flow Multiplier = 1.1 Mass Flow Multiplier = 1.2 Mass Flow Multiplier = 1.3 Bigger Turbine Size 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 9 von 24
Alternative Turbocharging Concepts Single Stage Turbocharging Maximum Power Set-up Power P [kw] 21 45 14 3 7 15 Torque M [Nm] Turbine Inlet T3 Temperature [K] [K] BSFC Be [g/kwh] 13 15 8 42 32 22 1 2 3 4 5 6 7 Drehzahl [1/min] Engine Speed [RPM] 1.5.85.65 3 15 P5 SWP [ CADeg [ KW n. a. TDC] OT] Lambda [--] Pressure Ratio [-] Reduced Massflow [(kg/s)-k^.5/kpa] 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 1 von 24
Alternative Turbocharging Concepts Assisted turbo charged Assistance can be electrical or mechanical Power P [kw] Turbine Inlet T3 Temperature [K] [K] BSFC Be [g/kwh] 21 14 7 13 15 8 42 32 22 1 2 3 4 5 6 7 Engine Drehzahl Speed [RPM] [1/min] 45 3 15 1.5.85.65 3 15 P5 SWP [ CADeg [ KW a. n. TDC] OT] Lambda [--] Torque M [Nm] 24 16 8 PuATL [W] Pressure Ratio [-] Wide operating range Requires high voltage net Assisted Mode Stardard Mode Reduced Massflow [(kg/s)-k^.5/kpa] M 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 11 von 24
Alternative Turbocharging Concepts Twin Parallel Turbo Two turbo with the smallest size are used Power P [kw] Turbine Inlet T3 Temperature [K] [K] BSFC Be [g/kwh] 21 14 7 13 15 8 42 32 22 1 2 3 4 5 6 7 Engine Drehzahl Speed [1/min] [RPM] 45 3 15 1.5.85.65 3 15 SWP P5 [ CADeg [ KW n. a. TDC] OT] M Torque [Nm] [Nm] Lambda [--] Limited mechanical inertia in single mode Difficult control of single to twin mode Pressure Ratio [-] Single Turbo Twin Turbo Reduced Massflow [(kg/s)-k^.5/kpa] 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 12 von 24
Alternative Turbocharging Concepts Twin Stage Turbo Small Turbo to assist low end torque Power P [kw] 21 45 14 3 7 15 Torque M [Nm] Wide Operating Range Easier control Turbine Inlet T3 Temperature [K] [K] BSFC Be [g/kwh] 13 15 8 42 32 22 1 2 3 4 5 6 7 Engine Drehzahl Speed [1/min] [RPM] 1.5.85.65 3 15 P5 SWP [ CADeg [ KW a. n. TDC] OT] Lambda [--] Pressure Ratio [-] High Pressure Low Pressure Boost Pressure Reduced Massflow [(kg/s)-k^.5/kpa] 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 13 von 24
Alternative Turbocharging Concepts Two stages turbocharging provides a relative simple solution of the trade off Introduction Torque at 15 rpm [Nm] 27 25 23 21 19 17 15 Leistung Power [kw] [kw] 2 175 15 125 1 75 5 25 HP - Stage LP -Stage 1 2 3 4 5 6 7 Engine Drehzahl Speed [1/min] [RPM] 145 155 165 175 185 195 Pow er at 6 rpm [kw] Mass Flow Multiplier =.8 Mass Flow Multiplier =.9 Mass Flow Multiplier = 1 Mass Flow Multiplier = 1.1 Mass Flow Multiplier = 1.2 Mass Flow Multiplier = 1.3 4 35 3 25 2 15 1 5 Drehmoment Torque [Nm] [Nm] Bigger Turbine Size 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 14 von 24
Torque Drehmoment [Nm] [Nm] Transient Behaviour: Load Step Volumetric Liefergrad Efficiency [--] [-] 29 21 13 5 1.5 1.1.7 Low- End- Torque Basisvariante Pmax.3-1 1 2 3 4 5 6 Time Zeit [s] 1.8 1.3.8 3 2 1 Residual Restgasgehalt Exhaust Gas [%] [%] Saugrohrdruck IM Pressure [bar] Load Steps at 15 rpm The transient response of a turbocharged engine is characterized by two phases In the first phase, the pressure in the intake manifold raise abruptly to the ambient pressure (throttle body opening) In the second phase the turbocharger accelerates up to reach its full load speed 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 15 von 24
Torque Drehmoment [Nm] [Nm] Transient Behaviour: Load Step Volumetric Liefergrad Efficiency [--] [-] 29 21 13 5 1.5 1..5 Low- End- Torque Basisvariante Pmax 2 Twin -stufig Stage. -1 1 2 3 4 5 6 Time Zeit [s] 1.8 1.3.8 6 4 2 Residual Restgasgehalt Exhaust Gas [%] [%] Saugrohrdruck IM Pressure [bar] Load Steps at 15 rpm The transient behavior of the twin stage turbo is, at a first glance, worse than the single stage concept The twin stage turbo is penalized by the higher backpressure due to the second turbine in the exhaust line 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 16 von 24
Torque Drehmoment [Nm] [Nm] Transient Behaviour: Load Step Volumetric Liefergrad Efficiency [--] [-] 29 21 13 5 1.5 1..5 Low- End- Torque Basisvariante Pmax 2 Twin -stufig Stage. -1 1 2 3 4 5 6 Time Zeit [s] 1.8 1.3.8 6 4 2 Residual Restgasgehalt Exhaust Gas [%] [%] Saugrohrdruck IM Pressure [bar] Load Steps at 15 rpm Acting on the cam timing and duration during the transient is it possible to greatly improve the transient behavior of the twin stage concept 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 17 von 24
Transient Behaviour: Tip-in maneuver Tip- in maneuver (6 1 km/h in 6. Gear) Drehmoment Torque [Nm] 35 3 25 2 15 1 5 Vmax [km/h] 275 265 255 245 235 13 12 HP - Stage 11 1 Elasticity 6-1 km/h (6. Gear) [s] Low- End- Torque Pmax Twin Stage LP -Stage Low- End- Torque Pmax Twin 2 -stufig Stage -1 1 2 3 4 5 6 7 8 9 1 Zeit Time [s] [s] 9 Geschwindigkeit Speed [km/h] [km/h] 8 15 1 95 9 85 8 75 7 65 Low- End- Torque Pmax Twin 2 -stufig Stage 6-1 1 2 3 4 5 6 7 8 9 1 Time Zeit [s] [s] With optimized cam timing it is possible to achieve good response for the twin-stage concept Comparing maximum speed with elasticity time it is possible to highlight the potential of the twin-stage concept for customer relevant performance 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 18 von 24
Introduction Single Stage Turbocharging The steady state performances of a turbo si engines are determined by different phenomena which have to be taken into account for turbomatching Using a single stage turbocharging concept, a compromise has to be chosen between maximum power and low end torque. High low end torque is coupled with a limited rev range, which penalize the sporty feeling Alternative Concept can be used to improve the compromise. Among others: Mechanical Assisted Turbocharged Electrical Assisted Turbocharged Twin Parallel Turbo Twin Stage Turbo The transient behavior is mainly determined by the turbocharged size Also for a turbocharged engine the optimization of the gas exchange process can produce significant benefit in transient. 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 19 von 24
Thanks for the Attention! 29119_VB_PES_GT-Suite-Coference.ppt Vincenzo Bevilacqua 9.11.29 Porsche Potential Engineering of Turbocharging Services GmbH Seite 2 von 24
Content Introduction Introduction Single Stage Turbocharging Alternative Turbocharging Concepts Transient analysis 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 21 von 24
Single Stage Turbocharging: Potential Introduction In order to investigate the potential of the Single Stage Turbocharging, a procedure to scale the Compressor-Turbine maps has been developed. The semi-empiric procedure is based of experimental data for different turbine compressor belonging to the same family, provided by turbocharger supplier Mass Flow Rate can be scaled, with the 2nd power of the reference diameter m& m& Verd Verd 1 2 d = d Verd Verd 1 2 2 Rotational Speed can be scaled with the inverse proportion of the reference diameter (fluidodynamic similitude of velocity triangles) n n Verd Verd 1 2 d = d Verd Verd 2 1 Maximum Compressor Blade Speed has been imposed to 52 m/s Efficiency and Pressure Drop dependency from reference diameter has been interpolated from experimental data 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 22 von 24
Transient Behaviour Introduction An automotive engine is practically always working in transient condition Response delay (Turbo Lag) is a drivability issue when turbo engines are considered There are different methods to evaluate dynamic characteristic of an engine Load Step Simulate a abrupt opening of the throttle body at fixed rpm. This method is independent from gear box and vehicle characteristisc Tip-in maneuver Simulate a abrupt opening of the throttle body and the subsequent acceleration of the vehicle. This method required to simulate (or to employ) a gear box and a vehicle characteristic 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 23 von 24
Transient Behaviour: Load Step Introduction Mass Flow [kg/ s].7.5.3.1.1 s before WOT.1 s after WOT 7 s after WOT -.1 Exhaust Auslass Intake E in lass Exhaust Auslass Intake E inlass Exhaust Auslass Intake E in lass 2.3 1.7 3 4 5 6 3 4 5 6 3 4 5 6.5 K W n. Z O T K W n. Z O T KW n. ZO T CADeg after TDC CADeg after TDC CADeg after TDC Residual Gas Back Flow Positive Pressure drop during Valve Overlap 1.1 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 24 von 24
Load Step Single Stage Turbocharger Costant Inertia Size Dependent Inertia + Verd. Massenstromfaktor [--] - + Verd. Massenstromfaktor [--] - Introduction 11 95 1 9 85 M95%/dt95% [Nm/s] 9 8 7 6 M95%/dt95% [Nm/s] 8 75 7 65 6 55 5 16 17 18 19 2 21 22 23 24 M95% [Nm] Turb. Massenstromfaktor.8 Turb. Massenstromfaktor.9 Turb. Massenstromfaktor 1 Turb. Massenstromfaktor 1.1 Turb. Massenstromfaktor 1.2 5 16 17 18 19 2 21 22 23 24 M95% [Nm] Turb. Massenstromfaktor.8 Turb. Massenstromfaktor.9 Turb. Massenstromfaktor 1 Turb. Massenstromfaktor 1.1 Turb. Massenstromfaktor 1.2 In the diagrams the 95% of the Maximum Torque at 15 rpm is compared aganinst the Average Torque Raising Velocity The most important parameter for the transient behavior of the turbocharger is his polar inertia moment With a fix maximum torque, the smaller the turbine the better the transient behavior The inertia of the compressor is much smaller than the turbine one, a bigger compressor improves transient response 29119_VB_PES_GT-Suite-Coference.ppt 9.11.29 Potential of Turbocharging Seite 25 von 24