The talks are on:
Dr. Gani Issayev
Postdoctoral Fellow, supervised by Prof. Thibault Guiberti
Abstract: Chemiluminescence-based optical sensors are known to have advantages such as small optical access requirements and inexpensive hardware. However, if only conventional optics are used, the line-of-sight nature of this technique makes it difficult to achieve a sufficient spatial resolution. Different approaches can be applied to overcome this drawback such as a Cassegrain optical system, iCCD images, etc. In this work we investigated the OH* and NH* chemiluminescence characteristics of the hydrogen-ammonia-air counterflow diffusion flames. Spatially and spectrally resolved OH* and NH* profiles were obtained with the help of the Cassegrain optical system as well as from flame images with an iCCD camera. These measured spatially resolved OH* and NH* profiles can be helpful both on development and validation of a chemical kinetic data.
Bio: Dr. Gani Issayev is a postdoctoral researcher in Professor Thibault Guiberti's research group in the Clean Combustion Research Center (CCRC) at King Abdullah University of Science and Technology (KAUST). He received his Ph.D. in Mechanical Engineering from KAUST in 2021 working under the supervision of Professor Aamir Farooq. The main focus of his current research is developing optical diagnostic techniques for characterization of combustion of alternative fuels e.g. ammonia, hydrogen and its blends.
Ph.D. Student at CCRC, supervised by Prof. Hong Im
Abstract: The combustion of ammonia/hydrogen is currently gaining importance in the power generation sector as an alternative to hydrocarbon fuels, and improved fundamental insights will facilitate its application. To investigate the complex interactions between turbulence and chemistry for ammonia-hydrogen jet flames under high-pressure conditions, large eddy simulation (LES) computations are conducted using the PC-transport model, which is based on Principal Component Analysis (PCA), coupled with nonlinear regression that utilizes deep neural networks (DNN) to enhance the size-reduction potential of PCA. The LES results are compared with the recent Raman/Rayleigh scattering measurements that were obtained at KAUST. As a first approximation, the unity-Lewis transport model is used for low hydrogen-content blends. Then, to improve the predictions, the training data set is extended to include variations in the local NH3/H2 ratio due to chemical and transport effects. Furthermore, the proposed PC-DNN approach is extended to include differential diffusion based on a rotation matrix technique and utilization of the mixture-averaged transport model for the training data set. The inclusion of differential diffusion leads to improved predictions, although some discrepancies are observed in fuel-lean regions. Finally, current work on modeling ammonia/hydrogen bluff-body flames will be briefly discussed.
Bio: Suliman is a Ph.D. candidate in Mechanical Engineering under the supervision of Prof. Hong Im. He received his Bachelor’s degree from KFUPM and then joined the Internal Combustion Engine Group of Politecnico di Milano, where he got his Master’s degree in 2020. Currently, his research focuses on modeling ammonia/hydrogen combustion systems.
Dr. Liang Yu
Postdoctoral Fellow, supervised by Prof. Deanna Lacoste
Abstract: Thermoacoustic instability, also known as combustion instability, is a major challenge to the efficiency and safety of industrial combustors, especially gas turbines. Mitigating thermoacoustic instability is of utmost importance in combustion systems. Nanosecond repetitively pulsed (NRP) discharge is a kind of non-equilibrium plasma that has been used for combustion enhancement. The usage of NRP discharges for mitigating the flame response to acoustic perturbation was only carried out at atmospheric pressure before. This study aims to investigate the effect of NRP discharges on the dynamics of lean premixed methane-air swirl flames at high pressure.
This study investigated the response of premixed swirl methane-air flames to acoustic forcing with and without nanosecond repetitively pulsed discharges. Experiments were carried out at three pressures of 1.2, 2.0 and 2.5 bar, with equivalence ratios of 0.79, 0.75, and 0.73 respectively. The NRP discharges were produced in the gap between the central bluff body and a metallic ring embedded in the outlet of the injection tube. Energy deposition was measured for all conditions. The power ratio of plasma to flame is about 0.32%, with two pulse repetition frequencies of 30 kHz and 70 kHz. A loudspeaker was used to force the incoming flow, with an amplitude of 10% of the bulk flow velocity. Fluctuations of heat release rate were measured by phase-locked imaging of CH* chemiluminescence using an intensified charge-coupled device camera. The velocity fluctuations were quantified by a hot-wire anemometer located in the injection tube, upstream of the swirler. It was found that the NRP discharges affected the flame transfer function by reducing the gain, especially at the low frequencies for all the pressures. The impact mechanism of NRP discharges on flame transfer function was further analyzed.
Bio: Dr. Liang Yu is a postdoctoral researcher in Prof. Deanna Lacoste's research group in the Clean Combustion Research Center (CCRC) at King Abdullah University of Science and Technology (KAUST), Saudi Arabia. He earned his Ph.D. degree in Power Engineering and Engineering Thermophysics in 2019 from Shanghai Jiao Tong University (SJTU), China. His doctoral work was focused on low-to-medium temperature autoignition of large-molecule actual fuels. His current research interests are high-pressure plasma-assisted combustion and combustion instability.