Fundamental and Applied Computational Studies of Turbulent Flows, Sprays, and Combustion

Professor John Abraham of the Department of Mechanical Engineering uses supercomputer resources in his work on fundamental and applied computational studies of turbulent flows, sprays, and combustion in Diesel and spark ignition engines. The applied work is directed towards the three- dimensional modeling and transient computations of flows, sprays, combustion, and emissions. The closely related fundamental studies include computations of droplet vaporization and combustion, the direct numerical simulation of turbulent mixing layers with chemical reactions, flamelet modeling of turbulent combustion, and studies of gas jets and sprays.

This research is driven by the fact that engine designers are faced with the need to meet increasingly stringent emissions regulations while maintaining high efficiency and reliability. For example, Diesel engine designers are faced with increasingly stringent regulations on particulate and NO emissions. Several means are being explored in order to meet these standards. These include the use of increased injection pressures, retarded timings, use of increased manifold pressures, and exhaust after-treatment devices. However, it is difficult to decrease NO and soot simultaneously without sacrificing efficiency. Maintaining performance while reducing emissions is a challenge. Supercomputing research and the application of multidimensional models play a pivotal role in the development of innovative strategies with which to control emissions while maintaining efficiency and performance.

There are many complex and interdependent variables in Diesel engine combustion. The injection process, intake part/valve geometry, the geometry of the combustion chamber, and the location of the injectors/spark plugs are just a few. Analysis is further complicated by the lack of fundamental understanding of the fuel atomization process and by the complex turbulent nature of the transient flow field in engines. Sub-models are incorporated into the governing equations in order to adequately describe the dynamics involved. The fundamental studies are aimed at developing better sub-models through comparisons with both experimental and direct simulations methods.

There is great interest in Professor Abraham's research on the part of engine designers and manufacturers because of its direct applicability to the production of more efficient and environmentally sound internal combustion engines.