A Global Lean NOx Trap Mechanism Including NH3 and N2O Production

• Bevan, Karen E. and William Taylor III. "Simulated Performance of a Diesel Aftertreatment System for U.S. 2010 Application." SAE Paper 2006-01-3551 (Note: this paper actually references my 2005 catalyst model paper, however the LNT model within the paper comes from this soon to be submitted paper)

Merging Undergraduate and Graduate Fluid Mechanics Through the Use of the SIMPLE Method for the Incompressible Navier-Stokes Equations

One-Dimensional Based Catalyzed Diesel Particulate Filter Model in Area Conservation Format Including the Soot and Wall Layers

Simulation and experimental data illustrate to students the effects certain parameters have on real physical phenomena. The simulation of an Internal Combustion (IC) engine is a suitable device for such illustration due to its widespread use and published experimental data. Many authors have modeled the workings of an engine and in this paper one such model is described: a single zone, pre-mixed spark-ignition heat release simulation. This simulation requires very little experimental data, yet can be used to characterize a wide variety of important physics. First the paper begins by describing the operation of an engine to those that are unfamiliar with such a device. A heat release simulation is then discussed in depth, describing how it is used to offer an understanding of thermodynamic fundamentals in an IC engine. A comprehensive study on two of the most important issues in modeling an IC engine, thermodynamic properties and heat transfer, demonstrates the need to accurately predict these properties when performing an accurate heat release analysis. This study demonstrates the power of such a simulation tool in an educational setting.

• Jacobs, Timothy J., Alexander Knafl, Stanislav V. Bohac, Dennis N. Assanis and Patrick G. Szymkowicz. “The Development of Throttled and Unthrottled PCI Combustion in a Light-Duty Diesel Engine.” SAE Paper 2006-01-0202.

ASME International Mechanical Engineering Congress & Exposition (IMECE2005-81330), November 5-11, 2005, Orlando, FL.

A large number of numerical algorithms have been reported to solve the Euler equations of motion for a variety of Mechanical and Aerospace Engineering applications. Based on a review of the past and current history of these solvers, a MUSCL-based solver that uses Hancock’s Predictor-Corrector Method incorporating Roe’s Approximate Riemann Solver was found to be the most efficient second-order accurate numerical method to solve the Euler equations. This method was subsequently extended to account for variable properties and then extensively validated for the effects of friction, heat transfer, variable area and chemical kinetics.

Graphical User Interfaces (GUIs) are being increasingly used in the classroom to provide users of computer simulations with a friendly and visual approach to specifying all input parameters and increased configuration flexibility. In this paper, the authors first describe a number of software and language options that are available to build GUIs. Subsequently, a comprehensive comparative assessment of possible alternatives is undertaken in the light of a benchmark educational program used in a course on Computational Fluid Dynamics (CFD) at the University of Michigan. For the GUIs presented, their educational value with respect to flexible data entry and post-processing of results has been demonstrated. In addition, the authors offer recommendations for pros and cons of available options in terms of platform independence, ease of programming, facilitation of interaction with students and flexibility.

As more emphasis is placed worldwide on reducing greenhouse gas emissions, automobile manufacturers have to create more efficient engines. Simultaneously, legislative agencies want these engines to produce fewer problematic emissions such as nitrogen oxides and particulate matter. In response, new technology, like homogeneous charge compression ignition and fuel cells, are being researched alongside lean-burning engines like the compression ignition or diesel engine. These newer engines present a number of benefits but still have significant challenges to overcome. As a result, renewed interest has risen in making lean-burning engines cleaner. The key to cleaning up the lean-burning engine is the placement of aftertreatment devices in the exhaust. These devices have shown great potential in reducing emission levels below regulatory levels while still allowing for increased fuel economy versus a traditional gasoline engine. However, these devices are subject to many flow control issues. While experimental evaluation of these devices helps to understand these issues better, it is impossible to solve the problem through experimentation alone because of time and cost constraints. Because of this, accurate models are needed in conjunction with the experimental work. In this dissertation, the author examines the entire exhaust system including reacting gas dynamics and aftertreatment devices, and develops a complete numerical model for it. The author begins by analyzing the current one-dimensional gas-dynamics simulation models used for internal combustion engine simulations. It appears that a more accurate and faster numerical method is available, in particular, those developed in aeronautical engineering, and the author successfully implements one for the exhaust system. The author then performs a comprehensive literature search to better understand the different aftertreatment devices. A number of these devices require a secondary injection of fuel or reductant in the exhaust stream. Accordingly, the author develops a simple post-cylinder injection model which can be easily calibrated to match experimental findings. In addition, the author creates a general catalyst model which can be used to model virtually all of the different aftertreatment devices. Extensive validation of this model with experimental data is presented along with all of the numerical algorithms needed to reproduce the model.

• Pontikakis, G. and Stamatelos, A. “Three-Dimensional Catalytic Regeneration Modeling of SiC Diesel Particulate Filters.” Journal of Engineering for Gas Turbines and Power; vol. 128 (April), pp. 421-433 (2006).
• Konstantas, G. and Stamatelos, A. M. “Computer Aided Engineering of Diesel Filter Systems.” Joint Meeting of the Greek and Italian Sections of The Combustion Institute, 17-19 June 2004, Corfu Island, Greece.

Local preconditioning for the Navier-Stokes equations may be called optimal if it equalizes all propagation and dissipation time-scales, for all combinations of Mach number and Reynolds number. Previously designed preconditioners are ineffective for certain combinations of low Reynolds number and low Mach number; in addition some of these create a growing mode, making the PDE-system unstable. (Users may regain stability through an implicit discretization.) In this paper we first review the forms and properties of all previously published N-S preconditioners on the basis of the 1-D N-S equations, then derive an optimal preconditioning matrix for these equations. We find again that it creates an unstable mode; a sensitivity analysis shows that optimal preconditioning and stability are mutually exclusive. Two possible remedies are suggested and briefly investigated: (1) to redefine the complex condition number in a way more appropriate for explicit discretizations; (2) to reformulate the N-S equations as a larger first-order system of hyperbolic-relaxation equations and base the preconditioner on this system. The latter approach appears most promising.

• Kleb, W., B. van Leer and B. Wood. “Matching Multistage Schemes to Viscous Flow.” AIAA Paper 2005-4708.
• Kleb, W. “Optimizing Runge-Kutta Schemes for Viscous Flow.” Ph.D. dissertation, Department of Aerospace Engineering, The University of Michigan, Ann Arbor, Michigan, 2004.
• Northrup, S. A. “A Parallel Adaptive-Mesh Refinement Scheme for Predicting Laminar Diffusion Flames.” Masters of Applied Science, University of Toronto, Toronto, Ontario, Canada, 2004.

In this paper, the available correlations proposed in the literature for the gas-side heat transfer in the intake and exhaust system of a spark-ignition internal combustion engine were surveyed. It was noticed that these correlations often are of the form and differ only by empirically fitted constants. This similarity provided the impetus for the authors to explore if a universal correlation could be developed. Based on a scaling approach using microscales of turbulence, the authors have fixed the exponential factor on the Reynolds number and thus reduced the number of adjustable coefficients to just one; the latter can be determined from a least squares curve-fit of available experimental data. Using intake and exhaust side data, it was shown that the universal correlation can be used for engine manifold flows. The correlation coefficient of this proposed heat transfer model with all available experimental data is 0.845 for the intake side and 0.800 for the exhaust side.

In this thesis, the search for an optimal Navier-Stokes preconditioner will be documented. This search begins by first understanding the physical characteristics of the one-dimensional Navier-Stokes equations in Chapter 2. Understanding the physics will give an insight as to how to precondition by finding the important regimes and parameters involved. In Chapter 3, a comprehensive literature search is described which documents the successes and failures of previous researchers. These results will help illustrate how to successfully precondition the 1-D Navier-Stokes equations. All previous work is expressed in the same set of variables in order to better understand where gains have been made. At the end of the chapter, the “perfect” preconditioner for the 1-D Navier-Stokes equations is given. The condition-number was found to be approximately one for all combinations of values of the parameters involved. Unfortunately, the preconditioner found has one regime in which it changes a damping mode into a growing mode. Chapter 4 concludes the thesis with a discussion of the inherent problems of the N-S equations and the generation of the growing mode. Options will be given as to how to precondition the N-S equations differently in order to avoid the growing mode. Appendix A specifies a number of important sets of variables and how to change the equations of motion between these variables. Appendices B and C will give the Euler and Navier-Stokes equations in these different variables.