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Dr. Lulin Jiang leads the combustion research taking place in the Mechanical Engineering Department. Dr. Lulin Jiang’s research interests are in design and application of fuel-flexible clean combustion systems and discovery of fundamental fuel injection and combustion characteristics of alternative fuels.   Her research projects integrate fundamental science of fluid mechanics, heat transfer, thermodynamics and combustion, with advanced flow measuring techniques.  In the area of combustion, Dr. Jiang experimentally studies combustion performance, involving emission and thermal features, of various fuels from waste sources using a dual-fuel burner equipped with a novel fuel injection system.  Conventional air blast injectors cannot achieve efficient and clean combustion for viscous fuels because of the limited atomization capability.  In contrast, with a simple geometry and a two-phase flow concept, the innovated twin-fluid fuel atomizer effectively generates fine sprays for fuels with a wide range of viscosity, without fuel preheating or hardware modification, and thus, results in ultra-low emission and high-efficiency combustion regardless of the distinct fuel properties, shown in Fig. 1.  Dr. Jiang is currently working on discovery of the relationship between burner design, including the injector geometry, and the combustion performance to optimize design and enable application of efficient combustors with high fuel flexibility and low-emission performance for both conventional and alternative fuels.  In the combustion field, Dr. Jiang is also performing on design and test of a volatile burner to develop a semi/self-sustained torrefaction system in the UL Energy Institute.

Another of Dr. Jiang’s research topics is investigation of fundamental fuel atomization mechanism using advanced flow measuring techniques including high speed shadowgraph and time-resolved laser diagnostics.  High speed visualization and time-resolved Particle Image Velocimetry (PIV) at high laser repetition rate are used to probe sprays in the injector near region, spatially and temporally revealing droplet breakup patterns by different aerodynamic mechanisms for the novel twin-fluid fuel injector, shown in Figs. 2 and 3.  Current research centers on investigation of unknown injector internal flow behavior and spray dynamics responding to varying fuel property and atomizer designs.  The experimental characterization enables optimization and modeling of the novel fuel injection system to further predict on-field atomization behavior in combustion environment.

Fig. 1 Clean blue flames of different fuels including viscous vegetable oil (VO) and glycerol using the novel clean burner. (Jiang and Agrawal, 2014).

Fig. 2 PIV image pair for the highly viscous glycerol spray captured at 15 kHz and 16.83 µm/pixel, and the corresponding instantaneous droplet velocity field.  ALR =2 (Jiang and Agrawal, 2015).

Fig. 3 High speed spray visualization (100 kHz) for water atomized by bubble bursting (circled) in the injector near field at exposure time of 1 µs.  Droplet size (A-C) ranges from around 20 µm to 100 µm (Jiang and Agrawal, 2015).