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Design of Experiments for Effects and Interactions During Brake Emissions Testing Using High-Fidelity Computational Fluid Dynamics

University of Michigan-Jesse Capecelatro, Qingquan Wang
Link Engineering Company-Carlos Agudelo, Ravi Teja Vedula
  • Technical Paper
  • 2019-01-2139
To be published on 2019-09-15 by SAE International in United States
The investigation and measurement of particle emissions from foundation brakes require the use of a special adaptation of inertia dynamometer test systems. To have proper measurements for particle mass and particle number, the sampling system needs to minimize transport losses and reduce residence times inside the brake enclosure. Existing models and spreadsheets estimate key transport losses (diffusion, turbophoretic, contractions, gravitational, bends, and sampling isokinetics). A significant limitation of such models is the inability to assess the complex turbulent flows and associated particle dynamics inside the brake enclosure, which is anticipated to be important. This paper presents a Design of Experiments (DOE) approach using Computational Fluid Dynamics (CFD) to predict the flow within a dynamometer enclosure under relevant operating conditions. The systematic approach allows the quantification of turbulence intensity, mean velocity profiles, and residence times. The factors of the DOE include: a) airflow level, b) brake size, c) rotor style, d) caliper position, e) brake rotation, f) brake rotational speed, and g) fixture style. Numerical simulations are performed using NGA, a high-order, multi-physics large-eddy simulation code.…
 

Structural Vibration of an Elastically Supported Plate due to Excitation of a Turbulent Boundary Layer

University of Michigan-Jonmarcos Diaz, Kevin Maki, Nickolas Vlahopoulos
Published 2019-06-05 by SAE International in United States
High-Reynolds number turbulent boundary layers are an important source for inducing structural vibration. Small geometric features of a structure can generate significant turbulence that result in structural vibration. In this work we develop a new method to couple a high-fidelity fluid solver with a dynamic hybrid analytical-numerical formulation for the structure. The fluid solver uses the Large-Eddy Simulation closure for the unresolved turbulence. Specifically, a local and dynamic one-equation eddy viscosity model is employed. The fluid pressure fluctuation on the structure is mapped to the dynamic structural model. The plate where the flow excitation is applied is considered as part of a larger structure. A hybrid approach based on the Component Mode Synthesis (CMS) is used for developing the new hybrid formulation. The dynamic behavior of the plate which is excited by the flow is modeled using finite elements. However, the rest of the surrounding structure is modeled using finite elements for the static modes and an analytical solution for the dynamic modes of the CMS decomposition. The two main elements of the new work,…
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Structural-Acoustic Modeling and Optimization of a Submarine Pressure Hull

University of Michigan-James Spain, Nickolas Vlahopoulos
Michigan Engineering Services, LLC-Geng Zhang
Published 2019-06-05 by SAE International in United States
The Energy Finite Element Analysis (EFEA) has been validated in the past through comparison with test data for computing the structural vibration and the radiated noise for Naval systems in the mid to high frequency range. A main benefit of the method is that it enables fast computations for full scale models. This capability is exploited by using the EFEA for a submarine pressure hull design optimization study. A generic but representative pressure hull is considered. Design variables associated with the dimensions of the king frames, the thickness of the pressure hull in the vicinity of the excitation (the latter is considered to be applied on the king frames of the machinery room), the dimensions of the frames, and the damping applied on the hull are adjusted during the optimization process in order to minimize the radiated noise in the frequency range from 1,000Hz to 16,000Hz. Constraints on the total amount of damping that can be used are considered (resource driven constraints) and structural collapse constraints are also taken into account in order to avoid…
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Comparison between Finite Element and Hybrid Finite Element Results to Test Data for the Vibration of a Production Car Body

University of Michigan-Nickolas Vlahopoulos, Sungmin Lee
Michigan Engineering Services, LLC-Geng Zhang
Published 2019-06-05 by SAE International in United States
The Hybrid Finite Element Analysis (HFEA) method is based on combining conventional Finite Element Analysis (FEA) with analytical solutions and energy methods for mid-frequency computations. The method is appropriate for computing the vibration of structures which are comprised by stiff load bearing components and flexible panels attached to them; and for considering structure-borne loadings with the excitations applied on the load bearing members. In such situations, the difficulty in using conventional FEA at higher frequencies originates from requiring a very large number of elements in order to capture the flexible wavelength of the panel members which are present in a structure. In the HFEA the conventional FEA model is modified by de-activating the bending behavior of the flexible panels in the FEA computations and introducing instead a large number of dynamic impedance elements for representing the omitted bending behavior of the panels. The excitation is considered to be applied on the conventional FEA model and the vibration analysis is conducted using the FEA. The power flow through the dynamic impedance elements is computed, and in…
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Closed-Form Structural Stress Solutions for Spot Welds in Square Plates under Central Bending Conditions

University of Michigan-Shin-Jang Sung, Jwo Pan
Published 2019-04-02 by SAE International in United States
A new closed-form structural stress solution for a spot weld in a square thin plate under central bending conditions is derived based on the thin plate theory. The spot weld is treated as a rigid inclusion and the plate is treated as a thin plate. The boundary conditions follow those of the published solution for a rigid inclusion in a square plate under counter bending conditions. The new closed-form solution indicates that structural stress solution near the rigid inclusion on the surface of the plate along the symmetry plane is larger than those for a rigid inclusion in an infinite plate and a finite circular plate with pinned and clamped outer boundaries under central bending conditions. When the radius distance becomes large and approaches to the outer boundary, the new analytical stress solution approaches to the reference stress whereas the other analytical solutions do not. The Mode II stress intensity factor solutions based on the new structural stress solution for a rigid inclusion in a square plate under central bending conditions are improved by up…
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Evaluation of Different ADAS Features in Vehicle Displays

University of Michigan-Abhishek Mosalikanti, Pranove Bandi, Sang-Hwan Kim
Published 2019-04-02 by SAE International in United States
The current study presents the results of an experiment on driver performance including reaction time, eye-attention movement, mental workload, and subjective preference when different features of Advanced Driver Assistance Systems (ADAS) warnings (Forward Collision Warning) are displayed, including different locations (HDD (Head-Down Display) vs HUD (Head-Up Display)), modality of warning (text vs. pictographic), and a new concept that provides a dynamic bird’s eye view for warnings.Sixteen drivers drove a high-fidelity driving simulator integrated with display prototypes of the features. Independent variables were displayed as modality, location, and dynamics of the warnings with driver performance as the dependent variable including driver reaction time to the warning, EORT (Eyes-Off-Road-Time) during braking after receiving the warning, workload and subject preference. The primary results were in line with previous research, validating previous claims of the superiority of HUD over HDD in warning delivery. It was also found that the text format of the warning yielded higher response rates along with lower workload, while most participants preferred the dynamic bird’s eye view layout.
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Quantifying the Effect of Initialization Errors for Enabling Accurate Online Drivetrain Simulations

University of Michigan-Hang Yang, Narayanan Kidambi, Kon-Well Wang
Ford Motor Company-Gregory M. Pietron, Rohit Hippalgaonkar, Yuji Fujii
Published 2019-04-02 by SAE International in United States
Simulations conducted on-board in a vehicle control module can offer valuable information to control strategies. Continued improvements to on-board computing hardware make online simulations of complex dynamic systems such as drivetrains within reach. This capability enables predictions of the system response to various control actions and disturbances. Implementation of online simulations requires model initialization that is consistent with the physical drivetrain state. However, sensor signals and estimated variables are susceptible to errors, compromising the accuracy of the initialization and any future state predictions as the simulation proceeds through the numerical integration process. This paper describes a drivetrain modeling and analysis method that accounts for initialization errors, thereby enabling accurate simulations of system behaviors. First, the hybrid dynamical system paradigm is employed to develop a torsional drivetrain model that captures the dynamics during a gear shift. The model is constructed in an analytical form and linearized to enable online mathematical analysis. Then a methodology is introduced to quantify the effect of initialization errors online. Finally, a procedure to systematically account for initialization errors is discussed. The…
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Evaluation of Low Mileage GPF Filtration and Regeneration as Influenced by Soot Morphology, Reactivity, and GPF Loading

University of Michigan-Stanislav Bohac, John Hoard
FCA US LLC-Jordan Elizabeth Easter, Kiran Premchand
Published 2019-04-02 by SAE International in United States
As European and Chinese tailpipe emission regulations for gasoline light-duty vehicles impose particulate number limits, automotive manufacturers have begun equipping some vehicles with a gasoline particulate filter (GPF). Increased understanding of how soot morphology, reactivity, and GPF loading affect GPF filtration and regeneration characteristics is necessary for advancing GPF performance. This study investigates the impacts of morphology, reactivity, and filter soot loading on GPF filtration and regeneration. Soot morphology and reactivity are varied through changes in fuel injection parameters, known to affect soot formation conditions. Changes in morphology and reactivity are confirmed through analysis using a transmission electron microscope (TEM) and a thermogravimetric analyzer (TGA) respectively.Evaluations regarding the impact of these varied soots on GPF performance is accomplished through monitoring of GPF filtration efficiency as a function of soot loading and monitoring of soot oxidation rates during GPF regeneration events. Size-dependent filtration efficiency across the GPF is determined with a Scanning Mobility Particle Sizer (SMPS). Soot oxidation during regeneration events is determined using a radio frequency (RF) sensor and periodic weighing of the GPF on…
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Application of Empirical Asperity Contact Model to High Fidelity Wet Clutch System Simulations

University of Michigan-Pengchuan Wang, Nikolaos Katopodes
F.C.C. CO., LTD.-Masatoshi Miyagawa, Takahiro Tsuchiya, Shinji Nakamura, Matthew Wendel, Hiroya Miyoshi
Published 2019-04-02 by SAE International in United States
Wet clutches are complex hydrodynamic devices used in both conventional and electrified drivetrain systems. They couple or de-couple powertrain components for applications such as automatic shifting, engine disconnect and torque vectoring. Clutch engagement behaviors vary greatly, depending on design parameters and operating conditions. Because of their direct impact on vehicle drivability and fuel economy, a predictive CAE model is desired for enabling analytical design verification processes. During engagement, a wet clutch transmits torque through viscous shear and asperity contact. A conventional Coulomb’s model, which is routinely utilized in shift simulations, is inadequate to capture non-linear hydrodynamic effects for higher fidelity analysis. Extensive research has been conducted over the years to derive hydrodynamic torque transfer models based on 1D squeeze film or 3D CFD. They are typically coupled with an elastic asperity contact model for mechanical torque transfer. However, the recent advancement reveals no significant asperity deformation at the frictional surface during engagement and establishes a new empirical asperity contact model. This paper describes the integration of the empirical asperity contact model with CFD for developing…
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Optimization of a Diesel Engine with Variable Exhaust Valve Phasing for Fast SCR System Warm-Up

University of Michigan-Pavan Kumar Srinivas, Rasoul Salehi
Published 2019-04-02 by SAE International in United States
Early exhaust valve opening (eEVO) increases the exhaust gas temperature by faster termination of the power stroke and is considered as a potential warm up strategy for diesel engines aftertreatment thermal management. In this study, first, it is shown that when eEVO is applied, the engine main variables such as the boost pressure, exhaust gas recirculation (EGR) and injection (timing and quantity) must be re-calibrated to develop the required torque, avoid exceeding the exhaust temperature limits and keep the air fuel ratio sufficiently high. Then, a two-step procedure is presented to optimize the engine operation after the eEVO system is introduced, using a validated diesel engine model. In the first step, the engine variables are optimized at a constant eEVO shift. In the second step, optimal eEVO trajectories are calculated using Dynamic Programming (DP) for a transient test cycle. The optimized results indicate that with early EVO, the boost pressure should be increased to provide enough cylinder air charge and to maintain the engine torque. External EGR can be reduced due to increased internal EGR…
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