Paul A. Erickson

Prediction of the First Modal Frequency of Compliant Mechanisms Using the Pseudo-Rigid-Body Model

The pseudo-rigid-body modeling technique is used to simplify the nonlinear analysis of compliant mechanisms. This paper presents the first work that investigates the possibility of using the pseudo-rigid-body model to predict the first modal response of compliant mechanisms. Four different configurations of the parallel-guiding mechanism are modeled and tested, as well as two configurations of compliant straight-line mechanisms. The model predictions of the first natural frequencies were compared with experimental results for all six mechanism configurations. The model predictions are within 9 percent of the experimental results for all cases.

Heat Transfer Enhancement of Steam Reformation by Passive Flow Disturbance Inside the Catalyst Bed

Because of the potential for high efficiency and low emissions, hydrogen powered systems are considered to be the next generation power source for both stationary and transportation applications. Providing a hydrogen source is a critical challenge. Steam reforming processes are demonstrated for producing hydrogen for fuel cell and other applications. Generating hydrogen via steam reformation requires that heat energy be transferred to the reactants to support the endothermic reaction. For a cylindrical steam-reforming reactor, large thermal gradients between the heat source (reactor wall) and reactor centerline create a nonideal condition for complete conversion. This gradient is caused by insufficient heat transfer inside the catalyst bed. Passive flow disturbance inside the catalyst bed is a potential method to enhance the heat and mass transfer in the steam-reforming process. This paper presents experimental research that investigates the effect of changing the flow pathway inside the reactor to improve the heat and mass transfer and thus enhance fuel conversion. Based on the experimental results, a 14% increase of methanol fuel conversion was achieved via the passive flow disturbance enhancement. The tradeoff was an extra pressure drop of 2.5 kPa across the reactor. A 30 h experimental run does not show a significant change in degradation rate for the passive flow disturbance. The results of this study contribute to the improvement of reformer design for better fuel processing system performance.

Theoretical analyses of autothermal reforming methanol for use in fuel cell

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

Design Improvements on a Vee Belt CVT and Application to a New In-line CVT Concept

Researchers at the UC Davis HEV Center have developed a new design of a continuously variable transmission for use in all vehicle sizes. They have implemented this design by modifying a conventional pulley-type CVT both significantly increasing the efficiency and allowing for implementation in hybrid powertrains. The CVT is a pulley-type transmission in which a chain or belt is used to transmit torque from the input shaft to the output drive shaft. The hydraulically controlled pulleys allow for an infinite number of transmission ratios in a specified range, eliminating the need for discrete shifts. With drivability characteristics better than that of an automatic transmission and higher efficiency, the CVT is a considerable alternative.

Enhancing hydrogen production for fuel cell vehicles by superposition of acoustic fields on the reformer: a preliminary study

Because of recent interest in energy efficiency and environmental issues, fuel cell vehicles are seen by many to be the way of the future. As near term fuel cell vehicles will likely use the existing liquid fuel infrastructure, the efficient reformation of hydrocarbon fuels is one technological hurdle that must addressed. An investigation has been made into the possibility of enhancing reformation processes through superposition of an acoustic field on the catalyst bed of a methanol steam reformer. As part of this study, background is given outlining the difficulties and liabilities of steam-reformation for transportation applications. Proven acoustic enhancement of various processes is reviewed and theory of acoustic enhancement of the steam-reforming process is developed. The facility studied includes a steam-reforming reactor that has been modified to accept an acoustic field. Relevant parameters of the acoustic field are quantified and discussed. The effect of the acoustic field has been investigated with relation to the reactor output parameters. Although the facility used has not been optimized for utilizing acoustic waves, significant acoustic enhancement of the steam-reformation process is demonstrated by the study and such enhancement has shown a positive effect on the reformation process. Potential benefits insulting from acoustic enhancement of steam reforming as shown by this study are: an increased reactor capacity for a given size and mass, smoothing of the temperature profile and better control of the temperatures in the catalyst bed. It is expected that for different fuels and/or reforming methods, similar results would be obtained for comparable process constraints.

Design and Development of a Parallel Hybrid Powertrain for a High Performance Sport Utility Vehicle

A plug-in, charge-depleting, parallel hybrid powertrain has been developed for a high performance sport utility vehicle. Based on the Ford U152 Explorer platform, implementation of the hybrid powertrain has resulted in an efficient, high performance vehicle with a 0-60 mph acceleration time of 7.5 seconds. A dual drive system allows for four-wheel drive capability while optimizing regenerative braking and minimizing electric motor cogging losses. Design of the system focused on reducing petroleum use, lowering greenhouse gas emissions, and reducing criteria tailpipe emissions. Additionally, this vehicle has been designed as a partial zero emissions vehicle (PZEV), allowing the driver to travel up to 50 miles in a zero emission all-electric mode. High-energy traction battery packs can be charged from the grid, yielding higher efficiencies and lower critical emissions, or maintained through the internal combustion engine (ICE) as with a traditional hybrid vehicle. The ICE is primarily used to provide average power and maintain state of charge (SOC). The ability to use the electric energy from the grid allows the most inexpensive way of driving the vehicle and reduces the dependence on petroleum. Electric power created at a large-scale power plant is produced more efficiently than by an ICE. However, to allow a long range and the option (rather than requirement) for using the plug, one has the capability to utilize liquid fuel through the ICE as well. Fuel consumption is reduced by more than 80% over the stock vehicle, resulting in average city usage of roughly 29 mpg (gasoline equivalent). Full functionality of the stock vehicle has been maintained, including four wheel drive, tow, and acceleration capabilities, as well as driver comfort, with no loss in cabin space and a small increase in vehicle weight. Analysis shows a final cost lower than comparable performance competitors. This paper details the design and implementation of this powertrain, and compares the hybrid vehicle response to that of the stock vehicle.

Hydrogen from Coal-Derived Methanol: Experimental Results

*† This study investigates hydrogen production via steam reformation of coal-derived methanol. The use of coal-derived methanol in fuel cell applications has recently been introduced as a potential energy pathway. However, prior to this study it was unknown if coal-derived methanol obtained from coal gasification is a pure enough feedstock to produce hydrogen for fuel cell applications. As a baseline, a study of fuel cell grade methanol has also been completed. Metrics for comparison are fuel conversion to hydrogen and catalyst degradation. The degradation of the catalyst is evidenced by the decrease in fuel conversion over time at a constant space velocity. The two types of methanol (fuel cell grade and coal-derived) contain different concentrations and types of impurities with different effects on catalyst degradation as evidenced by the performance of the fuel processor. Because of these considerations, different deactivation rates between fuel cell grade and coal-derived methanol were expected. This study shows the practicality of a new hydrogen pathway.

Heat Transfer Enhancement of Steam-Reformation by Passive Flow Disturbance Inside the Catalyst Bed

Because of the potential for high efficiency and low emissions, hydrogen powered fuel cell systems are considered to be the next generation power source for both stationary and transportation applications. Providing a hydrogen source to feed a fuel cell is a critical challenge. Steam reforming processes are demonstrated for producing hydrogen for fuel cell and other applications. Generating hydrogen via steam reformation requires that heat energy be transferred to the reactants to support the endothermic reaction. For a cylindrical steam-reforming reactor, large thermal gradients between the heat source (reactor wall) and reactor centerline create a non-ideal condition for complete conversion. This gradient is caused by insufficient heat transfer inside the catalyst bed. Passive flow disturbance inside the catalyst bed provides a potential to enhance the heat and mass transfer in the steam reforming process. This paper presents experimental research that investigates the effect of changing the flow pathway inside the reactor to improve the heat and mass transfer and thus enhance fuel conversion. The results of this study contribute to the improvement of reformer design for better fuel processing system performance.Copyright

Coal Based Methanol for Use in Fuel Cells: Research Needed

Recent interest in hydrogen fuel cells and fuel cell vehicles as well as interest in the energy independence of the United States has prompted investigation into the question of using methanol derived from domestic coal as a primary source for hydrogen production. Since 1983 Eastman Chemical Company has been utilizing methanol from high sulfur coal feedstock in the production of acetic anhydride and acetic acid at their Chemicals from Coal Facility in Kingsport, TN. The Chemicals from Coal Facility was the first use of a commercial Texaco coal gasifier to provide clean syngas for the production of acetyl chemicals. Methanol is produced as an intermediate step in the process in a Lurgi fixed catalyst bed gas phase reactor and in a newer “Liquid Phase” slurry process, which was built in 1997 as a joint venture between Eastman, Air Products and Chemicals Inc., and the Department of Energy. Initial testing has indicated that hydrogen can be derived from this coal-based fuel but impurities were seen as problematic, especially for utilization in fuel cells. The coal-derived methanol has since been further refined and distilled, yet no full analysis of the hydrogen produced from this refined product for fuel cell applications has taken place. This paper will discuss the fuel pathway from coal to hydrogen, including a description of the Eastman’s Coal Gasification Process and methanol production facilities as well as the research underway to quantify production of hydrogen from this coal-based methanol utilizing the latest reforming technologies for use in a Polymer Electrolyte (PEM) fuel cell.© 2004 ASME

Preliminary Modeling and Design of an Autothermal Reformer

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels (i.e., methanol, gasoline, natural gas). Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. This paper discusses the preliminary modeling and design of an experimental autothermal reformer that will be used in several research projects at the University of California at Davis. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.Copyright