Refine Your Search




Search Results

Technical Paper

The Development and Implementation of an Engine Off Natural Vacuum Test for Diagnosing Small Leaks in Evaporative Emissions Systems

This paper discusses an approach to detecting small leaks in an automobile's evaporative emissions systems that is a technique based upon ideal gas laws. It does this by monitoring pressure in the system while the vehicle's engine is off. This low cost solution can be easily implemented on General Motors vehicles using existing components. The topics covered in this paper include details on the background of the problem and the technique, the underlying thermodynamics of the technique, a description of the algorithm, testing and data collection considerations.
Technical Paper

Vehicle System Impacts of Fuel Cell System Power Response Capability

The impacts of fuel cell system power response capability on optimal hybrid and neat fuel cell vehicle configurations have been explored. Vehicle system optimization was performed with the goal of maximizing fuel economy over a drive cycle. Optimal hybrid vehicle design scenarios were derived for fuel cell systems with 10 to 90% power transient response times of 0, 2, 5, 10, 20, and 40 seconds. Optimal neat fuel cell vehicles where generated for responses times of 0, 2, 5, and 7 seconds. DIRECT, a derivative-free optimization algorithm, was used in conjunction with ADVISOR, a vehicle systems analysis tool, to systematically change both powertrain component sizes and the vehicle energy management strategy parameters to provide optimal vehicle system configurations for the range of response capabilities.
Technical Paper

Adaptive Energy Management Strategy for Fuel Cell Hybrid Vehicles

Fuel cell hybrid vehicles (FCHVs) use an energy management strategy to partition the power supplied by the fuel cell and energy storage system (ESS). This paper presents an adaptive energy management strategy, created in the ADVISOR™ software, for a series FCHV. The strategy uses a local or “real-time” optimization approach, which aims to reduce total energy consumption at each instantaneous time interval by dynamically adjusting the amount of power supplied by the fuel cell and ESS. Compared with a static control strategy, the adaptive strategy improved the simulated FCHV's fuel economy by 1.4%-8.5%, depending on the drive cycle.
Technical Paper

Design and Transient Simulation of Vehicle Air Conditioning Systems

This paper describes the need for dynamic (transient) simulation of automotive air conditioning systems, the reasons why such simulations are challenging, and the applicability of a general purpose off-the-shelf thermohydraulic analyzer to answer such challenges. An overview of modeling methods for the basic components are presented, along with relevant approximations and their effect on speed and accuracy of the results.
Technical Paper

Rapid Spherical Near-Field Antenna Measurements for Vehicle Applications

As more wireless services such as satellite radio (SDARS), navigation systems, OnStar, and mobile telephones are installed on GM vehicles, there is a need to make quick and accurate vehicle antenna pattern measurements. The interaction between vehicle and antenna must be included to ensure accurate vehicle antenna measurements. This implies that the size of the effective antenna should include both the antenna and vehicle interaction dimensions. For the frequency range of 500 MHz to 6 GHz, one solution is to use a spherical near-field system. The Satimo rapid probe array technology was selected to develop a vehicle antenna test system (ATS), which minimizes test time and maintains data accuracy. The ATS was designed to operate inside of an existing GM electromagnetic compatibility (EMC) anechoic chamber equipped with a nine-meter turntable.
Technical Paper

Infotainment System Immunity Characterization Via Bulk Current Injection

The proliferation of entertainment and communication systems in vehicles has led to increased concern as to the performance of these systems in an electromagnetic environment. One methodology used to assess radiated immunity performance on a component level is bulk current injection (BCI). In BCI a current probe is used to inject lower frequency radio waves (RF) onto the harness of an automotive device under test. This is an indirect methodology given that on a vehicle level a direct radiated field is impinged on the vehicle rather than a coupled current such as in BCI. Because of that, important considerations need to be taken into account to replicate the vehicle coupling phenomena on a component test. This paper examines setup issues and assesses the effectiveness of the BCI methodology for immunity testing of infotainment systems.
Technical Paper

Development of a Desulfurization Strategy for a NOx Adsorber Catalyst System

The aggressive reduction of future diesel engine NOx emission limits forces the heavy- and light-duty diesel engine manufacturers to develop means to comply with stringent legislation. As a result, different exhaust emission control technologies applicable to NOx have been the subject of many investigations. One of these systems is the NOx adsorber catalyst, which has shown high NOx conversion rates during previous investigations with acceptable fuel consumption penalties. In addition, the NOx adsorber catalyst does not require a secondary on-board reductant. However, the NOx adsorber catalyst also represents the most sulfur sensitive emissions control device currently under investigation for advanced NOx control. To remove the sulfur introduced into the system through the diesel fuel and stored on the catalyst sites during operation, specific regeneration strategies and boundary conditions were investigated and developed.
Technical Paper

Effect of Biodiesel Blends on Diesel Particulate Filter Performance

Tests of ultra-low sulfur diesel blended with soy-biodiesel at 5% and 20% were conducted using a 2002 model year Cummins ISB engine (with exhaust gas recirculation) that had been retrofitted with a passively regenerated catalyzed diesel particulate filter (DPF). Results show that on average, the DPF balance point temperature (BPT) is 45°C and 112°C lower for B20 blends and neat biodiesel, respectively, than for 2007 certification diesel fuel. Biodiesel causes a measurable increase in regeneration rate at a fixed steady-state condition, even at the 5% blending level. The data show no significant differences in NOx emissions for these fuels at the steady-state regeneration conditions, suggesting that differences in soot reactivity are responsible for the observed differences in BPT and regeneration rate.
Technical Paper

Impact of Ultra Thinwall Catalyst Substrates for TIER2 Emission Standards

The impact of ultra thinwall catalysts on TIER2 emission performance, packaging and total system cost was evaluated. The primary focus was to compare ultra-thinwall and thinwall cell configurations (400/3, 400/4, 600/2, 600/3, 600/3 hex, 900/2, and 1200/2) with a baseline 600/4 at constant substrate volume, washcoat and PGM loading. Other areas investigated included the evaluation of decreasing catalyst volume while maintaining constant or increased mass transfer capabilities while holding washcoat and PGM loadings constant. The emissions impact of varying washcoat and PGM loading was measured on specific substrates, including a comparison of square to hex cell. Backpressure for each configuration was calculated with the Corning substrate pressure drop modeling tool. Converters were rapid aged on dynamometers reflecting approximately a 50,000 mile aged performance. Emission testing was completed using the FTP test cycle.
Technical Paper

Driver Performance Research Regarding Systems for Use While Backing

General Motors has pursued research to develop systems intended to assist drivers in recognizing people or objects behind them when they are backing, and this paper summarizes results from this research. We are currently working with ultrasonic rear parking assist systems, rear radar backing warning systems, and rear camera systems, which are briefly described and their utility for assisting drivers in recognizing people or objects behind them discussed. Our research on driver performance with a prototype long range backing warning system found that audible and visual warning combinations may not be effective in warning distracted drivers about unexpected objects. Driver expectancy is thought to play a significant role in this result. However, further research found drivers were more likely to notice an unexpected obstacle behind their vehicle with a prototype rear view video camera system compared to ultrasonic rear parking assist and trials that had no system.