Recent advances in the MEMS fabrication technologies have led to strong research interest in micro-power generation devices as an alternative power source for numerous applications. The research program consists of the development of advanced computational methods validated with experimental measurements, and parametric studies specifically targeted at small-scale combustion systems. The parametric studies will address the issues regarding various combustion regimes, the modified ignition and extinction limits due to catalytic reaction, and the overall combustion performance. The study will also provide valuable guidance to many design specifications for the practical micro-combustor development, where low-temperature ignition and control of sustained combustion at desired thermodynamic conditions is the ultimate goal.

This is a novel fundamental study to uncover the physical mechanism and behavior of the viscosity-induced intrinsic instability mode of premixed flames.  A two dimensional computational simulation of the flame propagation under various parametric conditions reveals the effect of the instability mechanism on the overall turbulent burning velocity.  The project has strong relevance to the emerging technology of micro-scale combustor development.

Direct numerical simulation (DNS) is a mature and productive research tool in combustion science that is used to provide high-fidelity computer-based observations of the micro-physics found in turbulent reacting flows. Sponsored by DOE's program of "Scientific Discovery through Advanced Computing (SciDAC)," the scope of this project is to enhance the current DNS capability to the next level with new numerical and physical modeling capabilities.  The capabilities of the new DNS code will be demonstrated by the simulation of compression-ignition of hydrocarbon fuels in a turbulent inhomogeneous mixture, and the simulation of NOx emissions from hydrocarbon-air turbulent jet diffusion flames.  As a member of the multi-university teams (with Professors A. Trouve (University of Maryland) and C. Rutland (University of Wisconsin) along with Pittsburgh Supercomputing Center and Sandia National Laboratories), Professor Im's UM team is developing the physical modeling of soot formation and radiation processes in a state-of-the-art software architecture for tera-scale computing platform

The scientific goal of the program is to develop a fundamental understanding of the interaction between flame radiation and flame chemistry that is responsible for extinction of diffusion flames.  This NASA Microgravity project (co-PI with A. Atreya) involves extensive experimental measurements using NASA Glenn's drop tower facility, and the development of a high-fidelity computational tool to describe the transient behavior during the extinction of spherical diffusion flames, with full consideration of detailed chemical, transport, and radiation submodels. 

HCCI has high promises to dramatically reduce NOx and particulate emissions from IC engines, while simultaneously achieving high thermal efficiencies. However, significant scientific and practical challenges remain in order to control and implement the HCCI process in engines.  The UM team (Professors Assanis (PI), Atreya, Filipi, Im, Sick, Wooldridge) has led and have formed a Multi-University Research Consortium with MIT, Stanford, Berkeley, and Texas A&M, sponsored by DOE.  This team of experts have launched a three-year research effort combining computational and experimental approaches, and striking the appropriate balance between fundamental and applied research tasks, in order to deliver the understanding and technology necessary to enable practical HCCI control methodologies for engine applications.  Professor Im's role in the UM team is to develop the modeling tools and undertake the simulation of the HCCI engines and a rapid compression facility (RCF), which provides an optimal laboratory configuration to measure the ignition and combustion under high pressure conditions.

The objectives of the project led by Professor Levi Thompson (Chemical Engineering) with a number of co-PI's (E. Gulari, P. Savage, J. Schwank, R. Yang, W. Dahm, K. Powell, D. Assanis, H. Im) are to design and demonstrate high-performance desulfurizer, micro-reactor, and micro-combustor/micro-vaporizer that can deliver a 1kW gasoline fuel processor for PEM (proton-exchange membrane) fuel cells application.  Professor Im's group is currently developing a FLUENT-based CFD program to simulate the flow and chemical reaction processes within the micro-reactors, with full consideration of complex geometry and chemical kinetic models for the catalytic reactions.