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Physical Model of a Twin Scroll Turbine in GT-SUITE
Zak Z., Macek J., Vitek O., Emrich M., Takats M., Hatschbach P., Vavra J.
2015 European GT Conference, Frankfurt am Main
Czech Technical University in Prague Faculty of Mechanical Engineering
Josef Bozek Vehicle Centre of Sustainable Mobility
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Physical Model of a Twin Scroll Turbine in GT-SUITE Introduction Unsteady Flow Model Experimental Research Engine + Twin Scroll Turbine – preliminary results Conclusions
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Introduction
Physical Based Approach (1-D)
Full 1-D Modelling of Radial Turbine
Mixing after pressure decrease / flow acceleration
Classical Map Based Approach (0-D) Map Fraction for Section A / B Map Fraction for Section A / B Orifice Connection at pressures, which do not govern mixing flows Correction of orifice connection for different mass flow rates A / B needed
B
A
B
A
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Introduction
Presentation of 1-D physical model at GT-SUITE Conference 2008 and SAE 2008-01-0295, 2009-01-0303, 2011-01-1146 and 2015-01-1718 Map based approach - Lumped parameters turbine map model - too many measurements needed - problematic extrapolation despite the use of normalized and non-dimensional parameters - simple 0-D "virtual twin scroll" model - virtual joining of manifold branches at unrealistic pressures Full 1-D approach in GT-SUITE - Physical twin scroll turbine model takes into account - conditions for mixing of flows of different momentums at real static pressure inside a scroll - asymmetry of flow admission - asymmetry of turbine design (exhaust manifold or turbine scroll including WG) - existing dimensions of a turbine or dimensions close to them (found during calibration), proper calibration of 1-D turbine model is needful Generalized parameters of twin scroll turbine - fundamental independent variables for map based approach but used with 1-D approach for presentation of features only (without impact on model) - possible application for additive values - mass flow rates, enthalpy, power - pressure ratio cannot be averaged in a general way simultaneously from the point of view of mass flow rate, power, enthalpy and Mach number - blade speed ratio (BSR), discharge coefficient or reduced mass flow rate can be calculated using different averaging of pressure ratio - no general values Results of 1-D turbine simulation - mass flow rates via sections and turbine power in dependence on pressures and temperatures => replacement of classical turbine map => generalized parameters are not needed
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Physical Model of a Twin Scroll Turbine in GT-SUITE Introduction Unsteady Flow Model Experimental Research Engine + Twin Scroll Turbine – preliminary results Conclusions
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Unsteady Flow Model
p12
ct1
cIt12 cIr12
cIIr12
αI12
cIr12 cIIr12
ct2
wt3
r2 r12
r1
bI12
bII12
b2
Vaneless mixing zone
cIIt12
p2N
(Twin) scroll
Separated vaneless or bladed nozzle rings
Impeller Turbine inlet Scroll Momentum exchange
Impeller
Impeller leakage Flow Split
Amendments to 1-D single scroll physical model New module developed by Gamma Technologies (procedure of total states transformation between stator and impeller)
Stator – Impeller
P3
Turbine Impeller RP 4 Aout=Aref/cosβ3 press. loss C PI
Flow Connection
CI,=Ksep
Impeller –
Stator P4
Impeller Leakages
Unsteady Flow Pipe P1 Flow
Connection CD =1
Turbine Nozzle P2 Aout=Aref/cosα2 press. loss C PN
Flow Connection
CD=1
Flow Connection
CD=1
Single Scroll
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Unsteady Flow Model
Main Features Full 1-D approach GT-SUITE 1-D modules (pipes with external acceleration, orifices/nozzles, flow splits/joints) Modularity and versatility - twin / single scroll housings, VGT, WG, EGR Calibration procedure - best fit of experimental data and simulation with optimized input parameters (non-linear regression) Direct coupling with any model in GT-SUITE Library of 1-D / lumped parameter turbine templates User models and external (encrypted) subassemblies may be created Turbine design features may be investigated and tailored to current requirements Higher requirements of computational power
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Unsteady Flow Model - Turbine "Test Bed" Results - Testing of Qualitative Features Single Scroll
Twin Scroll - Uniform Admission
Twin Scroll - Partial Admission
𝑃𝑃 = 1 −𝑐𝑆 𝐴2 �̇�𝐴 + 𝑐𝑆 𝐵
2 �̇�𝐵
2𝑐𝑝𝑇0 𝐴𝐵 �̇�𝐴 + �̇�𝐵
𝜅1−𝜅
�̇�𝐴 + �̇�𝐵 𝑐𝑆 𝐴𝐵2 = �̇�𝐴𝑐𝑆 𝐴
2 + �̇�𝐵𝑐𝑆 𝐵2
𝑃𝑇𝑆 = �̇�𝐴𝑐𝑆 𝐴2
2 + �̇�𝐵𝑐𝑆 𝐵2
2
Twin Scroll - Partial Admission => pressure difference at turbine inlet 1.5 bar between sections A / B
c s used for representation of pressure ratio, nozzle mass flow rate (discharge coefficient) and BSR
Pressure ratio Perfect turbine power
𝑐𝑠 𝐴 = 2 𝑐𝑝𝐴𝑇𝐼𝐼 𝐴 𝑡𝑡𝑡𝑡𝑡 1 −1𝑃𝑃𝐴
𝜅𝐴−1𝜅𝐴
Averaged Pressure Ratio = 2.2
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Unsteady Flow Model - Turbine "Test Bed" Results - Testing of Qualitative Features
Twin Scroll - Partial Admission - different mass flow rates via sections A / B Turbine RPM and temperature upstream = constant Forced mass flow rate via turbine
Twin Scroll Mass Flow Rate Section A = 10% Section B = 90 %
Twin Scroll Mass Flow Rate Section A = 50% Section B = 50 %
Single Scroll Single Scroll Flow Split Included
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Physical Model of a Twin Scroll Turbine in GT-SUITE Introduction Unsteady Flow Model Experimental Research Engine + Twin Scroll Turbine – preliminary results Conclusions
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Experimental Research - Twin Scroll Turbine Test Bed for Model Calibration
Methodology - Turbocharger Test Bed Simulation (GT-SUITE) - 1-D / 0-D turbine model used for - prediction of turbine parameters (blade speed ratio - BSR; mass flow rates - sections A / B) - specification of real-world experiments - design of measuring section - measuring orifice diameter / required pressure sensor range Compressor measurement - compressor driven by - cold air turbine (no heat transfer to compressor casing) - hot gas turbine (with possibility to correct efficiency) Turbine measurement - different pressures and temperatures turbine upstream (impact on BSR) - throttling of mass flow rate in sections A / B (different level of partial admission) - backflow via single turbine section - influence of built-in EGR valve or WG position - influence of turbine internal wastegate Measured data evaluation - specific corrections (e.g., to heat transfer) Calibration procedure (GT-SUITE) - 1-D turbine model combined with optimization of input parameters
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Experimental Research - Constant Pressure Twin Scroll Turbine Test Bed
Uniform Admission
Partial Admission (Throttling)
Closed Section
Backflow
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Experimental Research - Constant Pressure Twin Scroll Turbine Test Bed 1) Simulation of a testbed in GT-SUITE - Open Loop Gas Stand + Burner 2) Development of Specific Twin Scroll Turbine Test Bed 3) Simulation Prediction - Turbine/Compressor steady operating points 4) Real-world experimental work
Cold Air
Temperature Turbine upstream
Larger Compressor Wheel
Throttling in Section
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Experimental Research - Engine tests - John Deere 6068 + Twin Scroll Turbine
John Deere 6068 Diesel + Twin Scroll Turbine
Cylinders: 6 In-Line Ignition Order: 1-5-3-6-2-4 Bore: 106 mm Stroke: 127 mm Displacement: 6.8 litres
Turbocharger: CZ Turbo
Fuel Pump: Bosch Open ECU: NI CompactRIO SW - Josef Bozek Research Centre
Pressure Sensors for Indication in Turbine Sections A / B
Turbocharger Speed Nonuniformity Sensor - Micro-Epsilon
Pressure Sensor for Indication
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Physical Model of a Twin Scroll Turbine in GT-SUITE Introduction Unsteady Flow Model Experimental Research Engine + Twin Scroll Turbine – preliminary results Conclusions
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Engine + Twin Scroll Turbine - preliminary results 6 Cylinder Diesel; BMEP 12 bar; 1600 RPM 120 - degree ignition order (1-5-3-6-2-4); pulse exhaust system
Experiment Turbine OUT
0-D Turbine OUT
Experiment Section B
0-D Twin B 0-D Twin A
Experiment Section A
Experiment vs. Uncalibrated Simulation, 0-D Turbine (model without cross-valve connection)
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Engine + Twin Scroll Turbine - preliminary results 6 Cylinder Diesel; BMEP 12 bar; 1600 RPM
1-D Twin A
Experiment Section A
1-D Turbine OUT
Experiment Section B
Experiment Turbine OUT
1-D Twin B
Experiment vs. Uncalibrated Simulation, 1-D Turbine
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Engine + Twin Scroll Turbine - preliminary results
4 Cylinder Diesel; Boost Pressure 2.8 bar; BMEP 12 bar; 2000 RPM Model of an engine with 4 (single) or 2 (twin) pulse exhaust systems
2.25
2.75
3.25
3.75
4.25
4.75
-180 -90 0 90 180 270 360 450 540
Pres
sure
[bar
]
Crank Angle [deg]
14000
16000
18000
20000
22000
24000
26000
-180 -90 0 90 180 270 360 450 540
Pow
er [W
]
Crank Angle [deg]
1-D Twin B
1-D Twin Scroll 1-D Single Scroll
1-D Single Scroll
4 cylinder ICE + Twin Scroll Turbine - higher and more fluctuating power from cylinder to turbine - better engine response to transient load - pumping work increases - fuel consumption increases => ICE efficiency decreases Turbine efficiency discrepancy => Mass and energy accumulation inside a turbine avoids real instantaneous efficiency assessment
Turbine Efficiency Measurement
Turbine Efficiency 0-D Simulation
BSR
Experiment - 4 cylinder ICE
1-D Twin A
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Physical Model of a Twin Scroll Turbine in GT-SUITE Introduction Unsteady Flow Model Experimental Research Engine + Twin Scroll Turbine – preliminary results Conclusions
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Josef Bozek Vehicle Centre of Sustainable Mobility cvum.eu / bozek.cvut.cz
Conclusions 1-D Twin / Single Scroll Turbine in GT-SUITE - comprehensive description of interactions between ICE - Turbocharger and inside a turbocharger - satisfying results of current qualitative simulation studies - expected reasonable extrapolation of turbine parameters based on physical description of phenomena inside a turbocharger turbine Utilization of 1-D Unsteady flow turbine model - modelling of downsized highly boosted engines with pulse exhaust systems for turbocharger matching and optimization especially in early stages of development => feedback and guidelines for design changes and CFD detailed simulation at a turbocharger manufacturer - predictive capability for newly designed turbines - transient response of a turbocharged engine - especially estimation of turbocharger speed as initial conditions Replacement of standard turbine maps by direct usage of full 1-D turbine model for both single and twin scroll turbines with different boost controls Turbine map (SAE, Look-up tables, regression etc.) may be created using virtual test bed and calibrated 1-D turbine model - if necessary Further development - experimental research - currently in-process - 1-D turbine model - WG, EGR, aftertreatment parts etc. - calibration procedure - library of calibrated 1-D turbine models
Acknowledgments: Development of a 1-D Model of a Radial Turbocharger Turbine Supported by the Financial Donation of Dr. Thomas Morel, Zvonicek`s Foundation, Czech Republic Technological Agency, Czech Republic, programme Centre of Competence, project #TE01020020 Josef Bozek Competence Centre for Automotive Industry EU Regional Development Fund in OP R&D for Innovations (OP VaVpI) and Ministry of Education, Czech Republic, project #CZ.1.05/2.1.00/03.0125 Acquisition of Technology for Vehicle Center of Sustainable Mobility