M.Sc. Tao Li

Contact

work +49 6151 16-28754
fax +49 6151 16-28900

Work L1|08 113
Otto-Berndt-Str. 3
64287 Darmstadt

a) In the perspective of combustion

Worldwide and especially in developing countries thus as China and India, the reliable and flexible electricity supply still relies on coal-fired power plants. Facing climate change, the reduction of greenhouse gases, in particular, CO2, has gained great focus in the discussions regarding global warming. For this purpose, various possible technologies have been proposed and investigated, enabling the so-called Carbon Capture and Storage (CCS) for power plants. Oxyfuel combustion has been proven to be one of the most energy and cost efficient CCS technologies for CO2 capture, which is archived by removing nitrogen from combustion medium and involving recycled flue gas. Oxyfuel combustion results in a CO2-rich flue gas and enables efficient CO2 separation. However, by substituting CO2 and H2O for nitrogen, the combustion chemistry and thus the entire combustion processes will be changed. In order to obtain a clear understanding and a correct description of the combustion behavior for Oxyfuel combustion, physical and chemical models and experimental investigations are required. This is the goal of the SFB/Transregio 129 Oxyflame (www.oxyflame.de), which is supported by the German Research Foundation (DFG) (www.dfg.de). To be specific, the research activities take place within the framework of the sub-project B7 focusing on experimental investigations of particle-turbulence-chemistry interaction under Oxyfuel conditions.

b) In the perspective of advanced laser diagnostics

Laser-based techniques play a vital role in non-intrusive scalar and velocity measurements for investigating flame-turbulence interactions. Although two-dimensional laser measure-ments such as particle image velocimetry (PIV) and laser-induced fluorescence (LIF) are extensively employed in combustion diagnostics, they lack the out-of-plane information and the transient evolutions are often not captured, which could lead to ambiguities in data in-terpretations. For a better understanding of the inherent multi-dimensional transient phe-nomena in combustion, the extension of planar single-shot measurements to high-speed vol-umetric measurement is desired. In general, two approaches for laser-based volumetric measurements, namely volumetric laser illumination approach and multiple laser sheets approach, urgently need further developments and adaptions.

a) Experimental investigation of solid fuel combustion using multi-parameter diagnostics

The work mainly focuses on the fundamental investigations of ignition and volatile combus-tion processes of coal and biomass, which are altered due to N2 replacement by CO2 as com-bustion atmosphere. For this purpose, a specially developed laminar flow reactor, shown schematically in Figure 1 (a), has been employed which could be operated for various gas composition [1]. By involving a pre-mixed laminar flat flame and a central seeding jet, the boundary conditions for both particle and gas phase are well characterized, which is for the convenience of experimental and numerical investigations. Other than atmosphere variations, the particle number density has a vital impact on the ignition and combustion due to the chemical and physical interaction of single solid fuel particles. As a major emphasis, the particle-particle interaction will be evaluated for different particle number density, exem-plarily shown in Figure 1 (b). In addition, to address the complex coupled processes of solid fuel devolatilization and conversion, multi-parameter and multi-dimensional laser diagnos-tics are implemented, as shown in Figure 1 (c), for simultaneous detection of particle veloci-ty, temperature, shape, size, ignition, combustion duration and etc.

Figure.1 (a) Sketch of the laminar flow reactor. (b) Photos of single particle and particle clouds. (c) Experimental setup.

b) Improvement of advanced laser diagnostics

Several experimental investigations on laminar and turbulent flames were demonstrated using laser scanning imaging and tomographic imaging of scalar and velocity field, briefly introduced as follows:

  • 10 kHz tomographic OH-LIF imaging measurement for detection of auto-ignition ker-nels was performed on a methane jet propagating in a high-turbulent and high-temperature co-flow [2]. The size and location of the detected kernels were evaluated for operating conditions with different Reynolds numbers of the fuel jet.
  • Volumetric reconstruction of reaction zone on laminar and turbulent flames using sin-gle-shot tomographic OH-LIF imaging [3]. The capability and feasibility of tomograph-ic OH-LIF were comprehensively evaluated in terms of illumination volume, number and orientation of detection views.
  • First quasi-4D laser scanning imaging measurement was performed by using acousto-optic deflector (AOD). Flame topology visualization and velocity field measurements were demonstrated on a non-premixed turbulent lifted CH4 jet [4].
  • Simultaneous species visualization and flow field measurements on a lifted DME jet flame using laser scanning CH2O LIF and tomographic PIV at 10 kHz.

[1] J. Köser, T. Li, N. Vorobiev, A. Dreizler, M. Schiemann, B. Böhm, Multi-parameter di-agnostics for high-resolution in-situ measurements of single coal particle combustion, Pro-ceedings of the Combustion Institute, Vol. 37, Issue. 3, pp 2893-2900, 2019, in press https://doi.org/ 10.1016/j.proci.2018.05.116

[2] J. Pareja , A. Johchi, T. Li, A. Dreizler, B. Böhm, A study of the spatial and temporal evolution of auto-ignition kernels using time-resolved tomographic OH-LIF, Proceedings of the Combustion Institute, Vol.37, Issue 2, pp 1321–1328, 2019, in press https://doi.org/10.1016/j.proci.2018.06.028

[3] T. Li, J. Pareja, F. Fuest, M. Schütte, Y. Zhou, A. Dreizler, B. Böhm. Tomographic imag-ing of OH laser-induced fluorescence in laminar and turbulent jet flames. Measurement Sci-ence and Technology, Vol.29, Issue 1, 015206, 2018, in press https://doi.org/10.1088/1361-6501/aa938a

[4] T. Li, J. Pareja, L. Becker, W. Heddrich, A. Dreizler, B. Böhm. Quasi‑4D laser diagnos-tics using an acousto‑optic deflector scanning system. Applied Physics B Vol. 123, Issue 3, 78, 2017, in press https://doi.org/10.1007/s00340-017-6663-5

[5] T. Li, J. Köser, A. Dreizler, M. Schiemann, B. Böhm, Time-resolved volumetric meas-urement of OH radicals on single particle and particle group combustion, The 14th. Confer-ence of Sustainable Development of Energy, Water and Environment Systems (SDEWES), Dubrovnik, Croatia, 2019 (submitted)