My Research Interests


Pollution Control - Modeling of Catalyst-based After-treatment Devices Devices
(Funded by NSF, Oak Ridge National Laboratory, Ford Scientific Research Laboratory, University of Michigan)

In response to the growing environmental issues concerning air pollution, this research program is directed to developing effective emission control technologies for gasoline and diesel engines. The primary focus of the program is on the modeling of after-treatment devices, which are employed to remove pollutants from engine exhaust gases. I am currently working on the following three projects in this area:

  • Modeling and performance analysis of catalytic converters for gasoline engines
  • Modeling of NOx traps and selective catalytic reduction systems for diesel and lean burn engines
  • Modeling of diesel particulate filters for diesel engines

    These projects are in different stages of progress. The work on these projects involves theoretical and numerical studies to develop a quantitative predictive understanding of various physiochemical processes that take place in engine after-treatment systems. In addition to its fundamental contributions, this research program will provide virtual testing grounds for the development and testing of novel catalyst technologies for engines. The simulation capabilities developed during this work will also have important applications beyond after-treatment and the transportation sector. Specifically, the fundamental models and computational tools developed can also be applied to catalytic combustion and fuel cells.

    Modeling of Fuel Cells
    (Funded by the CEEP)

    A technical challenge for fuel cell systems in automotive applications is the capacity to reject waste heat from a combination of stack inefficiencies, water management and other inefficiencies in the balance of plant. The development of a compact, lightweight water management subsystem with minimal parasitic power consumption is, therefore, critical to attaining targeted overall system power densities and specific power. The objective of this project is to investigate the physicochemical and electrochemical processes and develop a quantitative predictive understanding of the water and thermal management of the PEM fuel cells.

    Fundamental Investigation of Diffusion and Partially Premixed Flames
    (Funded by the NSF and the University of Michigan)

    A fundamental understanding of the thermochemical and physical processes of turbulent combustion is essential to designing and improving the performance of combustion devices and the chemical propulsion systems. The interaction between turbulence and combustion kinetics needs to be clearly understood in order to enhance our ability to predict the progress of turbulent combustion processes. This work was motivated by recognizing such a need.

    The present work involves theoretical and computational investigation and employs a systematic approach of studying the influence of the interaction of several coupled parameters including radiation, chemistry, unsteadiness, thermo-diffusion and preferential diffusion on several flame characteristics. The study is conducted on an axisymmetric counterflow diffusion flame configuration. Numerical simulations are performed by using detailed chemical kinetics and transport properties. The major outcome of the project will be a fundamental contribution to the turbulent flame modeling. The work will also contribute to the development of emission control methodologies for burners and furnaces.

    Development of Simulation Tools for High Velocity Oxygen Fuel Thermal Spraying
    (Funded by the US Department of Defense)

    The quality of high velocity oxygen fuel (HVOF) thermal spray coating depends greatly on the flame characteristics including its temperature, location, shape and emissions generated. For the best coating quality, the combustion chamber of the spray gun system must burn a stoichiometric mixture generating a predefined temperature. The quality of coating is also influenced by the flame location and shape. This can be controlled by accurately monitoring the flow rate and ensuring flow uniformity through all nozzles. In addition to a deteriorating coating quality, the partial blocking of some nozzles will also result in localized high temperatures which may eventually cause the meltdown of combustion chamber of the spray gun. To avoid such a catastrophe and poor coating quality requires the continuous monitoring and control of the physical and chemical processes occurring in the HVOF system. This in turn requires good fundamental understanding of these processes. The objective of this project is to develop simulation tools for design optimization of HVOF thermal spray system.

    Development of a Burn Model for Diesel Combustion
    (Funded by Ford Motor Company)

    Single-zone thermodynamic models, which assume the cylinder charge to be uniform in both composition and temperature, are widely used to model engine combustion process. These models can be used to analyze the heat release rate if experimentally determined pressure diagrams are specified in the first law of thermodynamics. Alternatively, single-zone models can be used as predictive tools if the heat release rate or the fuel mass burning rate is specified. The objective of this work was to develop a burn model that can simulate the diesel combustion process of the modern diesel engines running at high speed and high load conditions. In particular, the model should be able to capture the slow late burning (referred to as tail burning) mode, which is observed at high speed and high load conditions. The consideration of this combustion regime is important in better predicting the exhaust emissions. I developed the burn model based on a triple-Wiebe function. The model is based on several physical parameters and can capture all three modes of diesel combustion: premixed burning, diffusive burning, and tail burning.