physical model of a twin scroll turbine in gt-suite · pdf filephysical model of a twin scroll...

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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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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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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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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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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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

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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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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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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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Experimental Research - Constant Pressure Twin Scroll Turbine Test Bed

Uniform Admission

Partial Admission (Throttling)

Closed Section

Backflow

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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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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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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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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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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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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

physical model of a twin scroll turbine in gt-suite · pdf filephysical model of a twin scroll...

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