Christopher Depcik

Graphical user interfaces in an engineering educational environment

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 study, 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.

Instructional Use of a Single-Zone, Premixed Charge, Spark-Ignition Engine Heat Release Simulation

Modeling and computer simulation of an internal combustion engines operating processes offers a valuable tool for enhancing our understanding of real physical phenomena and contributes significantly to optimizing and controlling the engines operation to meet different objectives. This paper illustrates the use of engine modeling in the educational setting through the development and use of a single-zone, premixed charge, spark-ignition engine heat release simulation. The paper begins by describing the operation of an engine. A heat release simulation is then discussed in depth, and a description is given of how it can be used to offer an understanding of thermodynamic fundamentals in an internal combustion engine. In particular, a comprehensive examination of the thermodynamic properties of the engine working fluid and in-cylinder gas-to-wall heat transfer demonstrates the need for accurate physical—chemical sub-models when performing a high-fidelity heat release analysis. Overall, this study demonstrates the power of such an engine simulation tool in an educational setting.

Catalyzed diesel particulate filter modeling

Abstract An increasing environmental concern for diesel particulate emissions has led to the development of efficient and robust diesel particulate filters (DPF). Although the main function of a DPF is to filter solid particles, the beneficial effects of applying catalytic coatings in the filter walls have been recognized. The catalyzed DPF technology is a unique type of chemical reactor in which a multitude of physicochemical processes simultaneously take place, thus complicating the tasks of design and optimization. To this end, modeling has contributed considerably in reducing the development effort by offering a better understanding of the underlying phenomena and reducing the excessive experimental efforts associated with experimental testing. A comprehensive review of the evolution and the most recent developments in DPF modeling, covering phenomena such as transport, fluid mechanics, filtration, catalysis, and thermal stresses, is presented in this article. A thorough presentation on the mathematical model formulation is given based on literature references and the differences between modeling approaches are discussed. Selected examples of model application and validation versus the experimental data are presented.

A Universal Heat Transfer Correlation for Intake and Exhaust Flows in an Spark-Ignition Internal Combustion Engine

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 b Re a Nu = 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 4 3 Re 07 . 0 Nu = 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.

Simulating Area Conservation and the Gas-Wall Interface for One-Dimensional Based Diesel Particulate Filter Models

Researchers have been using one-dimensional based models of diesel particulate filters (DPFs) for over two decades with good success in comparison to measured experimental data. Recent efforts in literature have expanded the classical model to account for the effects of varying soot layer thickness on the flow area of the gases. However, some discrepancies exist with respect to this formulation and the physical phenomena modeled in the channel equations. In addition, there is still some discussion regarding the calculation of the gas temperature within the soot and wall layers. As a result, this paper presents a model to discuss these different phenomena to remove or validate previous assumptions. In specific, formulation of the flow equations in area-conserved format (or quasi-one-dimensional) allows the model to account for the changes in the gaseous area as a function of soot loading. In addition, imposing thermodynamic equilibrium at the interface of the channels and wall layers allows the model to capture the thermal entrance lengths. These tasks were undertaken to illustrate whether or not the results justify the effort is worthwhile and this additional complexity needs to be incorporated within the model. By utilizing linear density interpolation in the wall to increase the computational efficiency of the code, it was determined that the classical model assumptions of neglecting soot thickness and gas temperature in the wall are valid within the range of typical DPF applications.

Review of Chemical Reactions in the NO Reduction by CO on Rhodium/Alumina Catalysts

The emissions of nitric oxide and carbon monoxide from internal combustion engines are of primary concern due to their impact on the environment and peoples health. Since rhodium has proven to be an important catalyst for the reduction of nitric oxide by carbon monoxide, its accurate modeling is of significant value to industry. This paper reviews the literature with respect to this interaction in order to explain the history of the detailed reactions occurring on the surface. This review was accomplished in the absence of other species in order to focus the efforts and reduce the complexity of the task. In addition, this work presents an appropriate global reaction expression based on these detailed reactions for use in one-dimensional aftertreatment catalyst models.

THE NUMERICAL SIMULATION OF VARIABLE-PROPERTY REACTING-GAS DYNAMICS: NEW INSIGHTS AND VALIDATION

ABSTRACT 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 Hancocks predictor-corrector method incorporating Roes 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.

A one-dimensional lean NOx trap model with a global kinetic mechanism that includes NH3 and N2O

Abstract Eaton has developed an aftertreatment system for medium- and heavy-duty diesel engines in response to the US 2010 regulations. This system consists of a fuel reformer, a lean NO x trap (LNT), and an ammonia selective catalytic reduction (SCR) catalyst in series. A transient, one-dimensional model of the system was developed to improve system performance, reduce experimental testing, and optimize system design. In this paper, the LNT portion of this model is presented. The model simulates flow, heat transfer, and chemical reactions in the LNT catalyst. A global LNT chemical kinetic mechanism was developed to simulate the key catalytic processes with the minimum number of reactions. The model can be used to predict LNT catalyst performance over a range of operating conditions and driving cycles. Simulated species concentrations and gas temperatures at the LNT outlet were compared with experimental data at three steady state engine conditions over a 13-mode test. The conditions were chosen to develop and test the model over a range of gas temperatures, space velocities, and species concentrations. The LNT model predicts species trends and magnitudes with reasonable accuracy in comparison with experimental data. The simulated LNT NO x conversion efficiency over the 13-mode test was 67 per cent, compared with 63 per cent for the experiment.

Influence of Density Variation on One-Dimensional Modeling of Exhaust Assisted Catalytic Fuel Reforming

Exhaust gas recirculation has become commonplace within the automobile industry to reduce nitrogen oxide emissions because of its ability to lower the combustion temperature. However, it leads to an increase of particulate matter and degradation in fuel economy. One possible avenue for recovering this efficiency is to use exhaust assisted fuel reforming (EAFR) to generate hydrogen by catalytic means using injected fuel and exhaust and add it to the inlet mixture. Adding hydrogen in this manner has shown an increase in combustion stability and efficiency of the engine while reducing particulate matter production. Many classical works use incompressible fluid flow models in order to simulate the reactive flow in monolithic catalyst. However, such models are not appropriate in the case of EAFR, where exothermic reactions cause a large increase in the temperature and consequently in density. To simulate a catalyst undergoing EAFR reactions, a compressible flow solver was used in order to take into account the changes in density. The presented results show the importance of using proper gas dynamics and heat transfer for modeling a flow with catalytic reactions of high exothermicity.

Waste Cooking Oil Biodiesel Use in Two Off-Road Diesel Engines

This study examines the composition and combustion performance of biodiesel produced from waste cooking oil. Six fuel batches produced from waste oil used in dining-hall fryers were examined to determine their physical and chemical properties, including their elemental and fatty acid methyl ester composition. Oleic and linoleic methyl esters accounted for more than 70% of the fuel composition, while the oxygen content averaged 10.2% by weight. Exhaust emissions were monitored for 5–100% biodiesel blends using two off-road engines: a 2007 Yanmar diesel generator and a 1993 John Deere front mower. Increasing biodiesel content resulted in reduced emissions of partial combustion products from the diesel generator but a rise in NOx, with the greatest changes occurring between 5 and 20% biodiesel content. For the riding mower, biodiesel content up to 50% had little effect on emissions, while NOx and total hydrocarbon emissions decreased with 100% biodiesel. The difference in NOx emissions is attributed to the two different fuel injection control designs used in the two engines. These results indicate that the effects of biodiesel use on nonroad engine exhaust emissions may be substantially lower in older engines optimized for performance over emissions control.