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Evaluating the Effect of Two-Stage Turbocharger Configurations on the Perceived Vehicle Acceleration Using Numerical Simulation

Hyundai Motor Company-Jinsuk Kang
University of Michigan-Dearborn-Byungchan Lee, Dohoy Jung
Published 2016-04-05 by SAE International in United States
Charge boosting strategy plays an essential role in improving the power density of diesel engines while meeting stringent emissions regulations. In downsized two-stage turbocharged engines, turbocharger matching is critical to achieve desired boost pressure while maintaining sufficiently fast transient response. A numerical simulation model is developed to evaluate the effect of two-stage turbocharger configurations on the perceived vehicle acceleration. The simulation model developed in GT-SUITE consists of engine, drivetrain, and vehicle dynamics sub-models. A model-based turbocharger control logic is developed in MATLAB using an analytical compressor model and a mean-value engine model.The components of the two-stage turbocharging system evaluated in this study include a variable geometry turbine in the high-pressure stage, a compressor bypass valve in the low-pressure stage and an electrically assisted turbocharger in the low-pressure stage. Simulation results show excellent agreements with the test data. The results also indicate that the maximum acceleration and the time needed to reach the maximum can be improved by more than 25%, and more desirable linear acceleration profile can be achieved if a variable geometry turbine and…
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Fuel Economy Improvement During Cold Start Using Recycled Exhaust Heat and Electrical Energy for Engine Oil and ATF Warm-Up

Hyundai-Kia America Technical Center Inc.-John Myers, Jae-Hoon Kang
Hyundai-Kia Motors-Young-Ho Jung, Kwang-Yeon Kim
Published 2014-04-01 by SAE International in United States
A numerical study is conducted to investigate the effect of changing engine oil and automatic transmission fluid (ATF) temperatures on the fuel economy during warm-up period. The study also evaluates several fuel economy improving devices that reduce the warm-up period by utilizing recycled exhaust heat or an electric heater. A computer simulation model has been developed using a multi-domain 1-D commercial software and calibrated using test data from a passenger vehicle equipped with a 2.4 / 4-cylinder engine and a 6-speed automatic transmission. The model consists of sub-models for driver, vehicle, engine, automatic transmission, cooling system, engine oil circuit, ATF circuit, and electrical system.The model has demonstrated sufficient sensitivity to the changing engine oil and ATF temperatures during the cold start portion of the Federal Test Procedure (FTP) driving cycle that is used for the fuel economy evaluation. The results from the study indicate that the potential fuel economy improvement during the driving cycle is 7.3 % at 24°C ambient temperature, and 20.1 % at −6.7°C. An electric ATF heater and two heat exchangers that…
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Active Thermal Management with a Dual Mode Coolant Pump

SAE International Journal of Passenger Cars - Mechanical Systems

BorgWarner Inc.-Varun Negandhi, John Shutty
University of Michigan-Dearborn-Dohoy Jung
  • Journal Article
  • 2013-01-0849
Published 2013-04-08 by SAE International in United States
A GT-suite commercial code was used to develop a fully integrated model of a light duty commercial vehicle with a V6 diesel engine, to study the use of a BorgWarner dual mode coolant pump (DMCP) in active thermal management of the vehicle. An Urban Dynamometer Driving Schedule (UDDS) was used to validate the simulation results with the experimental data. The conventional mechanical pump from the validated model was then replaced with the dual mode coolant pump. The control algorithm for the pump was based on controlling the coolant temperature with pump speed. Maximum electrical speed of the pump and the efficiency of the pump were used to determine whether the pump should run in mechanical or electrical mode. The model with the dual mode coolant pump was simulated for the UDDS cycle to demonstrate the effectiveness of control strategy. Benefits of using the dual mode coolant pump in reducing auxiliary power, reducing friction losses and increasing fuel economy of the vehicle was investigated in this study. Lastly, a hot start UDDS cycle was used to…
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Simulation-based Assessment of Various Dual-Stage Boosting Systems in Terms of Performance and Fuel Economy Improvements

SAE International Journal of Engines

The University of Michigan – Ann Arbor-Byungchan Lee, Zoran Filipi, Dennis N. Assanis
The University of Michigan – Dearborn-Dohoy Jung
  • Journal Article
  • 2009-01-1471
Published 2009-04-20 by SAE International in United States
Diesel engines have been used in large vehicles, locomotives and ships as more efficient alternatives to the gasoline engines. They have also been used in small passenger vehicle applications, but have not been as popular as in other applications until recently. The two main factors that kept them from becoming the major contender in the small passenger vehicle applications were the low power outputs and the noise levels.A combination of improved mechanical technologies such as multiple injection, higher injection pressure, and advanced electronic control has mostly mitigated the problems associated with the noise level and changed the public notion of the Diesel engine technology in the latest generation of common-rail designs. The power output of the Diesel engines has also been improved substantially through the use of variable geometry turbines combined with the advanced fuel injection technology. However, recent trend in automotive industry suggests that the dual-stage boosting is also essential to further improve the power output of the Diesel engine to the level comparable to that of the other engine technologies. The advantage of…
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Development of an In-Cylinder Heat Transfer Model with Compressibility Effects on Turbulent Prandtl Number, Eddy Viscosity Ratio and Kinematic Viscosity Variation

University of Michigan - Ann Arbor-Hee Jun Park, Dennis N. Assanis
University of Michigan - Dearborn-Dohoy Jung
Published 2009-04-20 by SAE International in United States
In-cylinder heat transfer has strong effects on engine performance and emissions and heat transfer modeling is closely related to the physics of the thermal boundary layer, especially the effects of conductivity and Prandtl number inside the thermal boundary layer. Compressibility effects on the thermal boundary layer are important issues in multi-dimensional in-cylinder heat transfer modeling. Nevertheless, the compressibility effects on kinematic viscosity and the variation of turbulent Prandtl number and eddy viscosity ratio have not been thoroughly investigated. In this study, an in-cylinder heat transfer model is developed by introducing compressibility effects on turbulent Prandtl number, eddy viscosity ratio and kinematic viscosity variation with a power-law approximation. This new heat transfer model is implemented to a spark-ignition engine with a coherent flamelet turbulent combustion model and the RNG k- turbulence model. The model constant of the new heat transfer model which can yield the accurate match with experimental data for various operating conditions is found. The new heat transfer model with the model constant of 1.12 is suggested as an improved heat transfer model.
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Numerical Modeling and Simulation of the Vehicle Cooling System for a Heavy Duty Series Hybrid Electric Vehicle

University of Michigan-Sungjin Park, Dohoy Jung
Published 2008-10-06 by SAE International in United States
The cooling system of Series Hybrid Electric Vehicles (SHEVs) is more complicated than that of conventional vehicles due to additional components and various cooling requirements of different components. In this study, a numerical model of the cooling system for a SHEV is developed to investigate the thermal responses and power consumptions of the cooling system. The model is created for a virtual heavy duty tracked SHEV. The powertrain system of the vehicle is also modeled with Vehicle-Engine SIMulation (VESIM) previously developed by the Automotive Research Center at the University of Michigan. VESIM is used for the simulation of powertrain system behaviors under three severe driving conditions and during a realistic driving cycle. The output data from VESIM are fed into the cooling system simulation to provide the operating conditions of powertrain components. The cooling system model includes various component models for three main fluid circuits of coolant, cooling air, and engine oil. The model predicts the thermal responses of all cooling system components and the temperatures of the engine and electric components. Using the cooling…
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Engine-in-the-Loop Testing for Evaluating Hybrid Propulsion Concepts and Transient Emissions - HMMWV Case Study

Automotive Research Center, University of Michigan-Zoran Filipi, Hosam Fathy, Jonathan Hagena, Alexander Knafl, Rahul Ahlawat, Jinming Liu, Dohoy Jung, Dennis N. Assanis, Huei Peng, Jeffrey Stein
Published 2006-04-03 by SAE International in United States
This paper describes a test cell setup for concurrent running of a real engine and a vehicle system simulation, and its use for evaluating engine performance when integrated with a conventional and a hybrid electric driveline/vehicle. This engine-in-the-loop (EIL) system uses fast instruments and emission analyzers to investigate how critical in-vehicle transients affect engine system response and transient emissions. Main enablers of the work include the highly dynamic AC electric dynamometer with the accompanying computerized control system and the computationally efficient simulation of the driveline/vehicle system. The latter is developed through systematic energy-based proper modeling that tailors the virtual model to capture critical powertrain transients while running in real time. Coupling the real engine with the virtual driveline/vehicle offers a chance to easily modify vehicle parameters, and even study two different powertrain configurations. In particular, the paper describes the engine-in-the-loop study of a V8, 6L engine coupled to a virtual 4×4 High-Mobility Multipurpose Wheeled Vehicle (HMMWV). The results shed light on critical transients in a conventional powertrain and their effect on NOx and soot emissions.…
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Numerical Modeling of Cross Flow Compact Heat Exchanger with Louvered Fins using Thermal Resistance Concept

The University of Michigan-Dohoy Jung, Dennis N. Assanis
Published 2006-04-03 by SAE International in United States
Compact heat exchangers have been widely used in various applications in thermal fluid systems including automotive thermal management systems. Radiators for engine cooling systems, evaporators and condensers for HVAC systems, oil coolers, and intercoolers are typical examples of the compact heat exchangers that can be found in ground vehicles. Among the different types of heat exchangers for engine cooling applications, cross flow compact heat exchangers with louvered fins are of special interest because of their higher heat rejection capability with the lower flow resistance.In this study, a predictive numerical model for the cross flow type heat exchanger with louvered fins has been developed based on the thermal resistance concept and the finite difference method in order to provide a design and development tool for the heat exchanger. The model was validated with the experimental data from an engine cooling radiator. As a case study, the effect of the geometric changes of the heat exchanger on the heat rejection performance was explored. The results suggested that a predictive heat exchanger model is advised for the investigation…
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Pressure Reactive Piston Technology Investigation and Development for Spark Ignition Engines

Federal Mogul Corporation-Bruce Inwood
Ford Motor Company-John Brevick
Published 2005-04-11 by SAE International in United States
Variable Compression Ratio (VCR) technology has long been recognized as a method of improving Spark Ignition (SI) engine fuel economy. The Pressure Reactive Piston (PRP) assembly features a two-piece piston, with a piston crown and separate piston skirt which enclose a spring set between them. The unique feature is that the upper piston reacts to the cylinder pressure, accommodating rapid engine load changes passively. This mechanism effectively limits the peak pressures at high loads without an additional control device, while allowing the engine to operate at high compression ratio during low load conditions.Dynamometer engine testing showed that Brake Specific Fuel Consumption (BSFC) improvement of the PRP over the conventional piston ranged from 8 to 18 % up to 70% load. Knock free full load operation was also achieved. The PRP equipped engine combustion is characterized by reverse motion of the piston crown near top dead center and higher thermal efficiency.The cycle simulation was modified to investigate the effect of the spring set of PRP engine over a wide range of operation. In addition, the spherical…
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An Optimization Study of Manufacturing Variation Effects on Diesel Injector Design with Emphasis on Emissions

University of Michigan-Zhijun Li, Michael Kokkolaras, Dohoy Jung, Panos Y. Papalambros, Dennis N. Assanis
Published 2004-03-08 by SAE International in United States
This paper investigates the effects of manufacturing variations in fuel injectors on the engine performance with emphasis on emissions. The variations are taken into consideration within a Reliability-Based Design Optimization (RBDO) framework. A reduced version of Multi-Zone Diesel engine Simulation (MZDS), MZDS-lite, is used to enable the optimization study. The numerical noise of MZDS-lite prohibits the use of gradient-based optimization methods. Therefore, surrogate models are developed to filter out the noise and to reduce computational cost. Three multi-objective optimization problems are formulated, solved and compared: deterministic optimization using MZDS-lite, deterministic optimization using surrogate models and RBDO using surrogate models. The obtained results confirm that manufacturing variation effects must be taken into account in the early product development stages.
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