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Journal Article

Vehicle Level Brake Drag Target Setting for EPA Fuel Economy Certification

2016-09-18
2016-01-1925
The strong focus on reducing brake drag, driven by a historic ramp-up in global fuel economy and carbon emissions standards, has led to renewed research on brake caliper drag behaviors and how to measure them. However, with the increased knowledge of the range of drag behaviors that a caliper can exhibit comes a particularly vexing problem - how should this complex range of behaviors be represented in the overall road load of the vehicle? What conditions are encountered during coastdown and fuel economy testing, and how should brake drag be measured and represented in these conditions? With the Environmental Protection Agency (amongst other regulating agencies around the world) conducting audit testing, and the requirement that published road load values be repeatable within a specified range during these audits, the importance of answering these questions accurately is elevated. This paper studies these questions, and even offers methodology for addressing them.
Technical Paper

Least-Enthalpy Based Control of Cabin Air Recirculation

2015-04-14
2015-01-0372
The vehicle air-conditioning system has significant impact on fuel economy and range of electric vehicles. Improving the fuel economy of vehicles therefore demand for energy efficient climate control systems. Also the emissions regulations motivate the reduced use of fuel for vehicle's cabin climate control. Solar heat gain of the passenger compartment by greenhouse effect is generally treated as the peak thermal load of the climate control system. Although the use of advanced glazing is considered first to reduce solar heat gain other means such as ventilation of parked car and recirculation of cabin air also have impetus for reducing the climate control loads.
Technical Paper

Switching Roller Finger Follower Meets Lifetime Passenger Car Durability Requirements

2012-09-10
2012-01-1640
An advanced variable valve actuation (VVA) system is characterized following end-of-life testing to enable fuel economy solutions for passenger car applications. The system consists of a switching roller finger follower (SRFF) combined with a dual feed hydraulic lash adjuster and an oil control valve that are integrated into a four cylinder gasoline engine. The SRFF provides discrete valve lift capability on the intake valves. The motivation for designing this type of VVA system is targeted to improve fuel economy by reducing the air pumping losses during part load engine operation. This paper addresses the durability of a SRFF for meeting passenger car durability requirements. Extensive durability tests were conducted for high speed, low speed, switching, and cold start operation. High engine speed test results show stable valvetrain dynamics above 7000 engine rpm. System wear requirements met end-of-life criteria for the switching, sliding, rolling and torsion spring interfaces.
Journal Article

Design and Development of a Switching Roller Finger Follower for Discrete Variable Valve Lift in Gasoline Engine Applications

2012-09-10
2012-01-1639
Global environmental and economic concerns regarding increasing fuel consumption and greenhouse gas emission are driving changes to legislative regulations and consumer demand. As regulations become more stringent, advanced engine technologies must be developed and implemented to realize desired benefits. Discrete variable valve lift technology is a targeted means to achieve improved fuel economy in gasoline engines. By limiting intake air flow with an engine valve, as opposed to standard throttling, road-load pumping losses are reduced resulting in improved fuel economy. This paper focuses on the design and development of a switching roller finger follower system which enables two mode discrete variable valve lift on end pivot roller finger follower valvetrains. The system configuration presented includes a four-cylinder passenger car engine with an electro-hydraulic oil control valve, dual feed hydraulic lash adjuster, and switching roller finger follower.
Technical Paper

Thermal-Mechanical Durability of DOC and DPF After-treatment System for Light Heavy Pickup Truck Application

2009-11-02
2009-01-2707
The US Environmental Protection Agency (EPA)’s heavy duty diesel emission standard was tightened beginning from 2007 with the introduction of ultra-low-sulfur diesel fuel. Most heavy duty diesel applications were required to equip Particulate Matter (PM) after-treatment systems to meet the new tighter, emission standard. Systems utilizing Diesel Oxidation Catalyst (DOC) and Catalyzed-Diesel Particulate Filter (DPF) are a mainstream of modern diesel PM after-treatment systems. To ensure appropriate performance of the system, periodic cleaning of the PM trapped in DPF by its oxidation (a process called “regeneration”) is necessary. As a result, of this regeneration, DOC’s and DPF’s can be exposed to hundreds of thermal cycles during their lifetime. Therefore, to understand the thermo-mechanical performance of the DOC and DPF is an essential issue to evaluate the durability of the system.
Journal Article

Exhaust Valve & Valve Seat Insert – Development for an Industrial LPG Application

2009-05-13
2009-01-1602
Automotive engines are regularly utilized in the material handling market where LPG is often the primary fuel used. When compared to gasoline, the use of gaseous fuels (LPG and CNG) as well as alcohol based fuels, often result in significant increases in valve seat insert (VSI) and valve face wear. This phenomenon is widely recognized and the engine manufacturer is tasked to identify and incorporate appropriate valvetrain material and design features that can meet the ever increasing life expectations of the end-user. Alternate materials are often developed based on laboratory testing – testing that may not represent real world usage. The ultimate goal of the product engineer is to utilize accelerated lab test procedures that can be correlated to field life and field failure mechanisms, and then select appropriate materials/design features that meet the targeted life requirements.
Technical Paper

Concept and Implementation of a Robust HCCI Engine Controller

2009-04-20
2009-01-1131
General Motors recently demonstrated two driveable test vehicles powered by a Homogeneous Charge Compression Ignition (HCCI) engine. HCCI combustion has the potential of a significant fuel economy benefit with reduced after-treatment cost. However, the biggest challenge of realizing HCCI in vehicle applications is controlling the combustion process. Without a direct trigger mechanism for HCCI's flameless combustion, the in-cylinder mixture composition and temperature must be tightly controlled in order to achieve robust HCCI combustion. The control architecture and strategy that was implemented in the demo vehicles is presented in this paper. Both demo vehicles, one with automatic transmission and the other one with manual transmission, are powered by a 2.2-liter HCCI engine that features a central direct-injection system, variable valve lift on both intake and exhaust valves, dual electric camshaft phasers and individual cylinder pressure transducers.
Technical Paper

Observer Design for Fuel Reforming in HCCI Engines Using a UEGO Sensor

2009-04-20
2009-01-1132
Homogeneous Charge Compression Ignition (HCCI) combustion shows a high potential of reducing both fuel consumption and exhaust gas emissions. Many works have been devoted to extend the HCCI operation range in order to maximize its fuel economy benefit. Among them, fuel injection strategies that use fuel reforming to increase the cylinder charge temperature to facilitate HCCI combustion at low engine loads have been proposed. However, to estimate and control an optimal amount of fuel reforming in the cylinder of an HCCI engine proves to be challenging because the fuel reforming process depends on many engine variables. It is conceivable that the amount of fuel reforming can be estimated since it correlates with the combustion phasing which in turn can be measured using a cylinder pressure sensor.
Technical Paper

Opportunities and Challenges for Blended 2-Way SCR/DPF Aftertreatment Technologies

2009-04-20
2009-01-0274
Diesel engines offer better fuel economy compared to their gasoline counterpart, but simultaneous control of NOx and particulates is very challenging. The blended 2-way SCR/DPF is recently emerging as a compact and cost-effective technology to reduce NOx and particulates from diesel exhaust using a single aftertreatment device. By coating SCR catalysts on and inside the walls of the conventional wall-flow filter, the 2-way SCR/DPF eliminates the volume and mass of the conventional SCR device. Compared with the conventional diesel aftertreatment system with a SCR and a DPF, the 2-way SCR/DPF technology offers the potential of significant cost saving and packaging flexibility. In this study, an engine dynamometer test cell was set up to repeatedly load and regenerate the SCR/DPF devices to mimic catalyst aging experienced during periodic high-temperature soot regenerations in the real world.
Journal Article

Hot Surface Ignition of Gasoline-Ethanol Fuel Mixtures

2009-04-20
2009-01-0016
The purpose of this paper is to present the results of hot surface ignition (HSI) testing and American Society for Testing and Materials (ASTM) auto-ignition testing (AIT) performed on gasoline fuel mixtures containing varying levels of ethanol. With the increased consumer interest in ethanol-based fuels as a measure of reducing the United States dependence on foreign oil, the use of E85 and other ethanol/petroleum fuel blends is on the increase. While some autoignition data for summer and winter blends of gasoline on hot surfaces exist beyond the standard ASTM E659-78 test procedure [1], there is little data on ethanol-based fuels and their HSI characteristics.
Technical Paper

Compatibility Study of Fluorinated Elastomers in Automatic Transmission Fluids

2008-06-23
2008-01-1619
A compatibility study was conducted on fluorinated elastomers (FKM and FEPM) in various Automatic Transmission Fluids (ATF). Representative compounds from various FKM families were tested by three major FKM raw material producers - DuPont Performance Elastomers (DPE), Dyneon and Solvay. All involved FKM compounds were tested in a newly released fluid (ATF-A) side-by-side with conventional transmission fluids, at 150°C for various time intervals per ASTM D471. In order to evaluate the fluid compatibility limits, some FKM's were tested as long as 3024 hrs, which is beyond the normal service life of seals. Tensile strength and elongation were monitored as a function of ATF exposure time. The traditional dipolymers and terpolymers showed poor resistance to the new fluid (ATF-A). Both types demonstrated significant decreases in strength and elongation after extended fluid exposure at 150°C.
Technical Paper

Modeling Costs and Fuel Economy Benefits of Lightweighting Vehicle Closure Panels

2008-04-14
2008-01-0370
This paper illustrates a methodology in which complete material-manufacturing process cases for closure panels, reinforcements, and assembly are modeled and compared in order to identify the preferred option for a lightweight closure design. First, process-based cost models are used to predict the cost of lightweighting the closure set of a sample midsized sports utility vehicle (SUV) via material and process substitution. Weight savings are then analyzed using a powertrain simulation to understand the impact of lightweighting on fuel economy. The results are evaluated in the context of production volume and total mass change.
Journal Article

The Electrification of the Automobile: From Conventional Hybrid, to Plug-in Hybrids, to Extended-Range Electric Vehicles

2008-04-14
2008-01-0458
A key element of General Motors' Advanced Propulsion Technology Strategy is the electrification of the automobile. The objectives of this strategy are reduced fuel consumption, reduced emissions and increased energy security/diversification. The introduction of hybrid vehicles was one of the first steps as a result of this strategy. To determine future opportunities and direction, an extensive study was completed to better understand the ability of Plug-in Hybrid Electric Vehicles (PHEV) and Extended-Range Electric Vehicles (E-REV) to address societal challenges. The study evaluated real world representative driving datasets to understand actual vehicle usage. Vehicle simulations were conducted to evaluate the merits of PHEV and E-REV configurations. As derivatives of conventional full hybrids, PHEVs have the potential to deliver a significant reduction in petroleum usage.
Journal Article

Gasoline Fuel Injector Spray Measurement and Characterization - A New SAE J2715 Recommended Practice

2008-04-14
2008-01-1068
With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.
Journal Article

Late Intake Valve Closing as an Emissions Control Strategy at Tier 2 Bin 5 Engine-Out NOx Level

2008-04-14
2008-01-0637
A fully flexible valve actuation (FFVA) system was developed for a single cylinder research engine to investigate high efficiency clean combustion (HECC) in a diesel engine. The main objectives of the study were to examine the emissions, performance, and combustion characteristics of the engine using late intake valve closing (LIVC) to determine the benefits and limitations of this strategy to meet Tier 2 Bin 5 NOx requirements without after-treatment. The most significant benefit of LIVC is a reduction in particulates due to the longer ignition delay time and a subsequent reduction in local fuel rich combustion zones. More than a 95% reduction in particulates was observed at some operating conditions. Combustion noise was also reduced at low and medium loads due to slower heat release. Although it is difficult to assess the fuel economy benefits of LIVC using a single cylinder engine, LIVC shows the potential to improve the fuel economy through several approaches.
Journal Article

GREEN-MAC-LCCP®: A Tool for Assessing Life Cycle Greenhouse Emissions of Alternative Refrigerants

2008-04-14
2008-01-0828
The GREEN-MAC-LCCP© [Global Refrigerants Energy & Environmental - Mobile Air Condition - Life Cycle Climate Performance] model described here is an evolution of a previous GM model that assesses the lifecycle energy and GHG emissions associated with the production, use and disposal of alternative refrigerants and MAC components. This new model reduces the complexity of inputs and provides a consistent output analysis. This model includes Microsoft Excel Visual Basic© code to automatically make the calculations once inputs are complete.
Journal Article

Development of the Combustion System for General Motors' 3.6L DOHC 4V V6 Engine with Direct Injection

2008-04-14
2008-01-0132
General Motors' 3.6L DOHC 4V V6 engine has been upgraded to provide substantial improvements in performance, fuel economy, and emissions for the 2008 model year Cadillac CTS and STS. The fundamental change was a switch from traditional manifold-port fuel injection (MPFI) to spark ignition direct injection (SIDI). Additional modifications include enhanced cylinder head and intake manifold air flow capacities, optimized camshaft profiles, and increased compression ratio. The SIDI fuel system presented the greatest opportunities for system development and optimization in order to maximize improvements in performance, fuel economy, and emissions. In particular, the injector flow rate, orifice geometry, and spray pattern were selected to provide the optimum balance of high power and torque, low fuel consumption, stable combustion, low smoke emissions, and robust tolerance to injector plugging.
Technical Paper

Development and Control of Electro-hydraulic Fully Flexible Valve Actuation System for Diesel Combustion Research

2007-10-29
2007-01-4021
Fully flexible valve actuation (FFVA) system, often referred to as camless valvetrain, employs electronically controlled actuators to drive the intake and/or exhaust valves. This technology enables the engine controller to tailor the valve event according to the engine operating condition in real-time to improve fuel economy, emissions and performance. At GM Research and Development Center, we have developed laboratory electro-hydraulic FFVA systems for single cylinder gasoline engines. The objective of this work is to develop a FFVA system for advanced diesel combustion research. There are three major differences between gasoline and diesel engines in terms of applying the FFVA systems. First, the orientation of the diesel engine valves and the location of the fuel injection system complicate the packaging issue. Second, the clearance between the valves and the piston for diesel engines are extremely small.
Technical Paper

Tank-to-Wheels Preliminary Assessment of Advanced Powertrain and Alternative Fuel Vehicles for China

2007-04-16
2007-01-1609
Well-to-Wheels analyses are important tools that provide a rigorous examination and quantify the environmental burdens associated with fuel production and fuel consumption during the vehicle use phase. Such assessments integrate the results obtained from the Well-to-Tank (WtT) and the Tank-to-Wheels (TtW) analysis components. The purpose of this study is to provide a preliminary Tank-to-Wheels assessment of the benefits associated with the introduction of alternative powertrains and fuels in the Chinese market by the year 2015 as compared to the results obtained with conventional internal combustion engine vehicles (ICEVs). An emphasis is given on the vehicles powered by those fuels that have the potential to play a major role in the Chinese auto-sector, such as: M10, M85, E10, E85, Di-methyl Ether (DME) and Coal-to-Liquids (CTL). An important conclusion of this report is that hybridization reduces fuel consumption in all propulsion systems.
Technical Paper

Measurements of Cycle to Cycle Variability of the Inlet Flow of Fuel Injectors Using LDA

2006-10-16
2006-01-3314
The focus of this research effort was to develop a technique to measure the cyclic variability of the mass injected by fuel injectors. Successful implementation of the measurement technique introduced in this paper can be used to evaluate injectors and improve their designs. More consistent and precise fuel injectors have the potential to improve fuel efficiency, engine performance, and reduce emissions. The experiments for this study were conducted at the Michigan State University Automotive Research Experiment Station. The setup consists of a fuel supply vessel pressurized by compressed nitrogen, a Dantec laser Doppler anemometry (LDA) system to measure the centerline velocity of fuel, a quartz tube for optical access, and a Cosworth IC 5460 to control the injector. The detector on the LDA system is capable of resolving Doppler bursts as short as 6μs, depending on the level of seeding, thus giving a detailed time/velocity profile.
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