Your Selections

General Motors LLC
Show Only

Collections

File Formats

Content Types

Dates

Sectors

Topics

Authors

Publishers

Affiliations

Events

 

Benefits and Application Limits of Phenolic Piston Material in Opposed Piston Calipers

General Motors LLC-David B. Antanaitis, Mark Riefe
SBHPP-Chris Ciechoski
  • Technical Paper
  • 2019-01-2123
To be published on 2019-09-15 by SAE International in United States
The use of reinforced phenolic composite material in application to hydraulic pistons for brake calipers has been well established in the industry – for sliding calipers. For decades, customers have enjoyed lower brake fluid temperatures, mass savings, improved corrosion resistance, and smoother brake operation (less judder). However, some persistent concerns remain about the use of phenolic materials for opposed piston calipers. The present work explores two key questions about phenolic piston application in opposed piston calipers. Firstly, do opposed piston calipers see similar benefits? Do high performance aluminum bodied calipers, where the piston may no longer be a dominant heat flow path into the fluid (due to a large amount of conduction and cooling enabled by the housing), still enjoy fluid temperature reductions? Are there still benefits for judder with the much shorter length to diameter ratio the pistons have in these applications? Secondly – it is clear that the much shorter lengthy to diameter ratio of the piston in opposed piston calipers will result in significant increases in contact stress on the piston material…
 

Braking with a Trailer and Mountain Pass Descent

General Motors LLC-David B. Antanaitis, Brent Lowe
  • Technical Paper
  • 2019-01-2116
To be published on 2019-09-15 by SAE International in United States
A truly strange – but very interesting – juxtaposition of thought occurs when considering the “Voice Of Customer” deceleration needs for towing heavy trailers in mountainous regions, and the seemingly very different area of sizing brakes for Battery Electric Vehicles (BEV) and other regenerative braking-intensive vehicle applications. The common threads between these two very different categories of vehicles include (a) heavy dependence on the powertrain and other non-brake sources of energy loss to control the speed of the vehicle on the grade and ensure adequate capacity of the brake system, (b) a need to consider descent conditions where towing a heavy trailer is feasible (in the case of heavy trailer towing) or initiating a descent with a full state of charge is realistic (in the case of BEVs), which forces consideration of different descents versus the typical (for brake engineers) mountain peak descent. In this paper, a “Voice of Customer” based requirement is derived that integrates engine (or motor), transmission (or gearbox), driveline, brake system, brake cooling, trailer brakes, and for BEVs, battery and regenerative…
 

Combustion-Timing Control of Low-Temperature Gasoline Combustion (LTGC) Engines by Using Double Direct-Injections to Control Kinetic Rates

General Motors LLC-Jeremie Dernotte
Sandia National Laboratories-Gerald Gentz, Chunsheng Ji, Dario Lopez Pintor, John Dec
Published 2019-04-02 by SAE International in United States
Low-temperature gasoline combustion (LTGC) engines can provide high efficiencies and extremely low NOx and particulate emissions, but controlling the combustion timing remains a challenge. This paper explores the potential of Partial Fuel Stratification (PFS) to provide fast control of CA50 in an LTGC engine. Two different compression ratios are used (CR=16:1 and 14:1) that provide high efficiencies and are compatible with mixed-mode SI-LTGC engines. The fuel used is a research grade E10 gasoline (RON 92, MON 85) representative of a regular-grade market gasoline found in the United States. The fuel was supplied with a gasoline-type direct injector (GDI) mounted centrally in the cylinder. To create the PFS, the GDI injector was pulsed twice each engine cycle. First, an injection early in the intake stroke delivered the majority of the fuel (70 - 80%), establishing the minimum equivalence ratio in the charge. Then, a second injection supplied the remainder of the fuel (20 - 30%) at a variable timing during the compression stroke, from 200° to 330°CA (0°CA = TDC-intake, 360°CA = TDC-compression) to provide controlled…
Datasets icon
Annotation icon
 

An Efficient Trivial Principal Component Regression (TPCR)

General Motors LLC-Balakrishna Chinta
Published 2019-04-02 by SAE International in United States
Understanding a system behavior involves developing an accurate relationship between the explanatory (predictive) variables and the output response. When the observed data is ill-conditioned with potential collinear correlations among the measured variables, some of the statistical methods such as least squared method (LSM) fail to generate good predictive models. In those situations, other methods like Principal Component Regression (PCR) are generally applicable. Additionally, the PCR reduces the dimensionality of the system by making use of covariance relationship among the variables. In this paper, an improved regression method over PCR is proposed, which is based on the Trivial Principal Components (TPC). The TPC regression (TPCR) makes use of the covariance of the output response and predictive variables while extracting principal components. A new method of selecting potential principal components for variable reduction in TPCR is also proposed and validated. Two example problems, which are highly collinear, were considered for illustration. Results are also compared with the Partial Least Squares Regression (PLS1), which is another widely used statistical method, for ill-conditioned data analysis. From these results, it…
Datasets icon
Annotation icon
 

Strain Rate Effect on Martensitic Transformation in a TRIP Steel Containing Carbide-Free Bainite

General Motors LLC-Charles Enloe, Vesna Savic, Whitney Poling, Louis Hector
Clemson University-Rakan Alturk
Published 2019-04-02 by SAE International in United States
Adiabatic heating during plastic straining can slow the diffusionless shear transformation of austenite to martensite in steels that exhibit transformation induced plasticity (TRIP). However, the extent to which the transformation is affected over a strain rate range of relevance to automotive stamping and vehicle impact events is unclear for most third-generation advanced high strength TRIP steels. In this study, an 1180MPa minimum tensile strength TRIP steel with carbide-free bainite is evaluated by measuring the variation of retained austenite volume fraction (RAVF) in fractured tensile specimens with position and strain. This requires a combination of servo-hydraulic load frame instrumented with high speed stereo digital image correlation for measurement of strains and ex-situ synchrotron x-ray diffraction for determination of RAVF in fractured tensile specimens. Specifically, the potentially competing effects of strain rate on austenite transformation to martensite were investigated to determine which predominate at nominal strain rates of 0.5 s-1, 5 s-1, 50 s-1 and 500 s-1. A corresponding decrease in austenite volume fraction at a fixed true strain with strain rate suggests that austenite transformation to…
Datasets icon
Annotation icon
 

Determining the Greenhouse Gas Emissions Benefit of an Adaptive Cruise Control System Using Real-World Driving Data

General Motors LLC-William Dvorkin, Joshua King, Marc Gray, Shyhyeu Jao
Published 2019-04-02 by SAE International in United States
Adaptive cruise control is an advanced vehicle technology that is unique in its ability to govern vehicle behavior for extended periods of distance and time. As opposed to standard cruise control, adaptive cruise control can remain active through moderate to heavy traffic congestion, and can more effectively reduce greenhouse gas emissions. Its ability to reduce greenhouse gas emissions is derived primarily from two physical phenomena: platooning and controlled acceleration. Platooning refers to reductions in aerodynamic drag resulting from opportunistic following distances from the vehicle ahead, and controlled acceleration refers to the ability of adaptive cruise control to accelerate the vehicle in an energy efficient manner. This research calculates the measured greenhouse gas emissions benefit of adaptive cruise control on a fleet of 51 vehicles over 62 days and 199,300 miles. To our knowledge, the greenhouse gas emissions benefit of an advanced vehicle technology has never been demonstrated in this manner, and no automaker has published such extensive data pertaining to adaptive cruise control. These results highlight the opportunity to further reduce consumer fuel use and…
Annotation icon
 

Development of an Alternative Predictive Model for Gasoline Vehicle Particulate Matter and Particulate Number

General Motors LLC-Elana Chapman, Mark Winston-Galant, Pat Geng
University of Michigan-Sophia Pryor
Published 2019-04-02 by SAE International in United States
The Particulate Matter Index (PMI) is a helpful tool which provides an indication of a fuel’s sooting tendency. Currently, the index is being used by various laboratories and OEMs as a metric to understand the gasoline fuels impact on both sooting found on engine hardware and vehicle out emissions. This paper will explore a new method that could be used to give indication of the sooting tendency of the gasoline range fuels, called the Particulate Evaluation Index (PEI), and provide the detailed equation in its initial form. In addition, the PEI will be shown to have a good correlation agreement to PMI. The paper will then give a detailed explanation of the data used to develop it. Initial vehicle PM/PN data will also be presented that shows correlations of the indices to the vehicle response.
Annotation icon
 

A System Safety Perspective into Chevy Bolt’s One Pedal Driving

General Motors LLC-Richard A. Kulas
General Motors Proving Ground-Helen Rieland, Jenna Pechauer
Published 2019-04-02 by SAE International in United States
The Chevy Bolt’s One Pedal Driving feature is a new electrification propulsion enhancement that allows the driver to accelerate, decelerate and hold their vehicle stationary by just using the accelerator pedal. With this new feature, the driver is relieved of having to switch between pressing the accelerator pedal and brake pedal to slow, stop and hold the vehicle stationary. While this feature provides a convenience to the driver, it also presents a paradigm shift in driver engagement and control system responsibility for executing certain functions that the driver was traditionally responsible to perform. Various system safety techniques were involved in the development of such a feature both from a traditional functional safety perspective as well as a Safety of the Intended Functionality (SOTIF) perspective. The safety considerations for this feature included not only the traditional failure scenarios of the sensors, actuators, controllers, serial data, etc. involved with the feature and its functions, but also the anticipated driver behavior that may potentially result from using the feature. For instance, when the driver releases the accelerator pedal…
Annotation icon
 

Limitations of Sector Mesh Geometry and Initial Conditions to Model Flow and Mixture Formation in Direct-Injection Diesel Engines

Richard C. Peterson
General Motors LLC-Alok Warey
Published 2019-04-02 by SAE International in United States
Sector mesh modeling is the dominant computational approach for combustion system design optimization. The aim of this work is to quantify the errors descending from the sector mesh approach through three geometric modeling approaches to an optical diesel engine. A full engine geometry mesh is created, including valves and intake and exhaust ports and runners, and a full-cycle flow simulation is performed until fired TDC. Next, an axisymmetric sector cylinder mesh is initialized with homogeneous bulk in-cylinder initial conditions initialized from the full-cycle simulation. Finally, a 360-degree azimuthal mesh of the cylinder is initialized with flow and thermodynamics fields at IVC mapped from the full engine geometry using a conservative interpolation approach. A study of the in-cylinder flow features until TDC showed that the geometric features on the cylinder head (valve tilt and protrusion into the combustion chamber, valve recesses) have a large impact on flow complexity. As a result, errors in near-TDC swirl ratio, vortex structure and turbulence availability were seen when employing sector meshing, even if a 360-degree sector, with direct IVC flow…
Datasets icon
Annotation icon
 

Efficiency Evaluation of Lower Viscosity ATF in a Planetary Automatic Transmission for Improved Fuel Economy

General Motors LLC-Khaled Zreik
FCA US LLC-Haiying Tang
Published 2019-04-02 by SAE International in United States
With continued industry focus on reducing parasitic transmission and driveline losses, detailed studies are required to quantify potential enablers to improve vehicle fuel economy. Investigations were undertaken to understand the influence of lower viscosity Automatic Transmission Fluids (ATF) on transmission efficiency as compared with conventional fluids. The objectives of this study were to quantify the losses of lower viscosity ATF as compared with conventional ATF, and to understand the influence of ATF properties including viscosities, base oil types, and additive packages on fuel efficiency.The transmission efficiency investigations were conducted on a test bench following a vehicle-based break-in of the transmission using a prescribed drive cycle on a chassis dynamometer. At low temperature, the lower viscosity ATF showed a clear advantage over the conventional ATF in both spin loss and loaded efficiency evaluations. At high temperature, mixed results were obtained; it appeared the chemistry of ATF influenced the results.Overall, using the low viscosity fluid tends to improve loss behavior, but the benefits can be offset if the transmission hardware employed is not specifically designed for low…
Datasets icon
Annotation icon