Conditionally-averaged structures in wall-bounded turbulent flows

The quadrant-splitting and the wall-shear detection techniques were used to obtain ensemble-averaged wall layer structures. The two techniques give similar results for Q4 events, but the wall-shear method leads to smearing of Q2 events. Events were found to maintain their identity for very long times. The ensemble-averaged structures scale with outer variables. Turbulence producing events were associated with one dominant vortical structure rather than a pair of counter-rotating structures. An asymmetry-preserving averaging scheme was devised that allowed a picture of the average structure which more closely resembles the instantaneous one, to be obtained

Transient Analysis and Modeling of Automotive PEM Fuel Cell System Accounting for Water Transport Dynamics

ABSTRAC

A 1-D PLANAR SOLID OXIDE FUEL CELL MODEL FOR SIMULATION OF SOFC-BASED ENERGY SYSTEMS

ABSTRACT A one-dimensional steady-state model for planar solid oxide fuel cells (SOFCs) is presented. Appropriately simplified, the model includes sufficient detail for supporting ongoing investigations involving the simulation of SOFC-based advanced energy systems. The presentation focuses on a set of nonlinear equations accounting for conservation of mass and energy along a single SOFC in a co-flow configuration. Electrochemical models also are employed, including one previously used for a zero dimensional approach. The equations are described through a phenomenological approach based on the best recent work in the field and model validation is carried out in two distinct phases using previously published information. Potential areas of application for the model presented are noted. INTRODUCTION The objective of this paper is to report on work in progress aimed at simulating advanced energy systems having a solid oxide fuel cell as a principal component. For such work it is sufficient to employ a simplified SOFC model that captures the salient physical/chemical effects. Accordingly, efforts thus far have centered on the development of a one-dimensional SOFC model resting solidly on the best recent work in the field, while being convenient and effective for achieving the larger goal of simulating SOFC-based advanced energy systems. The intent of this modeling effort is to be able to handle both the hydrogen and internal reforming cases, while representing the electrochemistry using either a grey box approach or black box approach. Specifically in this paper, a 1-D model has been developed that captures the dominant physical and electrochemical phenomena taking place in a co-flow planar SOFC, accounting for internal reforming while retaining computational simplicity and good accuracy. The objective of the model is to simulat

Lithium-ion batteries life estimation for plug-in hybrid electric vehicles

This paper deals with life estimation of lithium batteries for plug-in hybrid electric vehicles (PHEVs). An aging model, based on the concept of accumulated charge throughput, has been developed to estimate battery life under "real world" driving cycles (custom driving cycles based on driving statistics). The objective is to determine the "damage" on the life related to each driving pattern to determine equivalent miles/years. Results indicates that Lithium-ion batteries appear to be 10 year/150,000 mile capable, provided that they are not overcharged, nor consistently operated at high temperatures, nor in charge sustaining mode at a very low state of charge. ©2009 IEEE

PHEV fleet data collection and analysis

This paper deals with a project related to Plug-in Hybrid Electric Vehicles fleet studies. The project is part of a broader research consortium underway at Ohio State University's Center for Automotive Research called SMART@CAR. Main goals are to create and maintain a database containing all charging and duty cycle data collected from a growing PHEV fleet. Real-world data provided by these vehicles will be collected, archived, organized and analyzed. The availability of real world data will also help estimate the effects of PHEV penetration on the utility energy sales, generation capacity, the transmission grid, market economics, and environmental emissions. ©2009 IEEE

Statistical analysis of PHEV fleet data

The added load that a PHEV (Plug-in Hybrid Electric Vehicle) fleet imposes on the existing electrical grid is of great concern to the electric utility industry. In this paper, analysis was done for a PHEV fleet which consists of 6 PHEVs that were instrumented using data loggers for a period of approximately one year. Systematic analysis using a clustering approach was carried out for the real world velocity profiles. A driving pattern recognition algorithm was developed based on the clustering of the results and Markov-chain model was used for the stochastic velocity generation for different driving patterns. The work of this paper is a part of a larger project in which a mass simulation of a neighborhood of PHEVs will be conducted based on statistical representations of key factors such as vehicle usage patterns, vehicle characteristics, and market penetration of PHEVs

Daisie D. Boettner Gino Paganelli Proton Exchange Membrane Fuel Cell System Model for Automotive Vehicle Simulation and Control

This paper describes a proton exchange membrane (PEM