Browsing by Author "Wu, Yue"
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- 4D combustion and flow diagnostics based on tomographic chemiluminescence (TC) and volumetric laser-induced fluorescence (VLIF)Wu, Yue (Virginia Tech, 2016-12-02)Optical diagnostics have become indispensable tools for the study of turbulent flows and flames. However, optical diagnostics developed in the past have been primarily limited to measurements at a point, along a line, or across a two-dimensional (2D) plane; while turbulent flows and flames are inherently four-dimensional (three-dimensional in space and transient in time). As a result, diagnostic techniques which can provide 4D measurement have been long desired. The purpose of this dissertation is to investigate two of such 4D diagnostics both for the fundamental study of turbulent flow and combustion processes and also for the applied research of practical devices. These two diagnostics are respectively code named tomographic chemiluminescence (TC) and volumetric laser induced fluorescence (VLIF). For the TC technique, the emission of light as the result of combustion (i.e. chemiluminescence) is firstly recorded by multiple cameras placed at different orientations. A numerical algorithm is then applied on the data recorded to reconstruct the 4D flame structure. For the VLIF technique, a laser is used to excite a specific species in the flow or flame. The excited species then de-excite to emit light at a wavelength longer than the laser wavelength. The emitted light is then captured by optical sensors and again, the numerical algorithm is applied to reconstruct the flow or flame structure. This dissertation describes the numerical and experimental validation of these two techniques, and explores their capabilities and limitations. It is expected that the results obtained in this dissertation lay the groundwork for further development and expanded application of 4D diagnostics for the study of turbulent flows and combustion processes.
- Development and validation of a reconstruction algorithm for three-dimensional nonlinear tomography problemsLei, Qingchun; Wu, Yue; Xu, Wenjiang; Ma, Lin (Optical Society of America, 2016-07-06)This work reports the development and experimental validation of a reconstruction algorithm for three-dimensional (3D) nonlinear tomography problems. Many optical tomography problems encountered in practice are nonlinear, for example, due to significant absorption, multiple-scattering, or radiation trapping. Past research efforts have predominately focused on reconstruction algorithms for linear problems, and these algorithms are not readily extendable to nonlinear problems due to several challenges. These challenges include the computational cost caused by the nonlinearity (which was compounded by the large scale of the problems when they are 3D), the limited view angles available in many practical applications, and the measurement uncertainty. A new algorithm was therefore developed to overcome these challenges. The algorithm was validated both numerically and experimentally, and was demonstrated to be able to solve a range of nonlinear tomography problems with significantly enhanced efficiency and accuracy compared to existing algorithms.
- Two-dimensional transition metal carbides as supports for tuning the chemistry of catalytic nanoparticlesLi, Zhe; Yu, Liang; Milligan, Cory; Ma, Tao; Zhou, Lin; Cui, Yanran; Qi, Zhiyuan; Libretto, Nicole; Xu, Biao; Luo, Junwei; Shi, Enzheng; Wu, Zhenwei; Xin, Hongliang; Delgass, W. Nicholas; Miller, Jeffrey T.; Wu, Yue (2018-12-10)Supported nanoparticles are broadly employed in industrial catalytic processes, where the active sites can be tuned by metal-support interactions (MSIs). Although it is well accepted that supports can modify the chemistry of metal nanoparticles, systematic utilization of MSIs for achieving desired catalytic performance is still challenging. The developments of supports with appropriate chemical properties and identification of the resulting active sites are the main barriers. Here, we develop two-dimensional transition metal carbides (MXenes) supported platinum as efficient catalysts for light alkane dehydrogenations. Ordered Pt3Ti and surface Pt3Nb intermetallic compound nanoparticles are formed via reactive metal-support interactions on Pt/Ti3C2Tx and Pt/Nb2CTx catalysts, respectively. MXene supports modulate the nature of the active sites, making them highly selective toward C-H activation. Such exploitation of the MSIs makes MXenes promising platforms with versatile chemical reactivity and tunability for facile design of supported intermetallic nanoparticles over a wide range of compositions and structures.