zurück zur Liste

Dr.-Ing. Jhon Alexander Pareja Restrepo

Arbeitsgebiet(e)

Reaktive Strömungen und Messtechnik

Kontakt

Understanding the phenomena involved in auto-ignition of turbulent flows is essential in the development of industrial combustion systems. Homogeneous charge compression ignition (HCCI) and diesel engines rely on auto-ignition to initiate combustion Auto-ignition also plays an important role in the flame stabilization of burners using moderate and intense low oxygen dilution (MILD) or high temperature air combustion (HiTAC) technologies. On the other hand, auto-ignition must be prevented in devices such as lean premixed prevaporized gas turbines and spark-ignition engines.

One approach is to study auto-ignition during the continuous or pulsed injection of a fuel turbulent jet into a hot co-flow in order to mimic auto-ignition conditions similar to those of practical processes. Within this approach, substantial contributions to comprehend the complex turbulence-chemistry interactions underlying auto-ignition of mixing flows have been made mainly through numerical simulations, while the available experimental data are still limited. In this context, a new test rig for auto-ignition studies was developed with a particular emphasis on the application of a variety of laser diagnostic techniques. Collected experimental data is used to develop, validate and improve predictive models, to increase the understanding on auto-ignition phenomena, and to confirm fundamental DNS findings.

This novel auto-ignition test rig allows having short heat-up times of the co-flow (from room temperature to 1300 K in ∼30 min.), reduced temperature variations (± 2 K), bulk exit velocities of up to 40 m/s with adjustable turbulence levels, and a top-hat temperature distribution in radial direction within the region of interest for auto-ignition studies. In addition, the variation of the co-flow and fuel compositions is possible.

The measurement of important boundary conditions and experimental studies on auto-ignition performed in the MWPH test rig include:

  • Simultaneous temporally-resolved planar laser-induce fluorescence (PLIF) measurements of CH2O and OH for visualizing the low- and high-temperature reaction zones and their evolution with time.
  • Simultaneous single-shot measurements of temperature and mixture fraction fields during the onset of auto-ignition using NO-PLIF and Rayleigh scattering.
  • Time-resolved (10 kHz) tomographic LIF for the study of the spatial and temporal evolution of auto-ignition kernels.
  • Velocity field measurements using stereo particle image velocimetry (S-PIV) at 10 kHz.
  • Laser absorption spectroscopy for the measurement of species concentration at the inflow boundary.

T. Li, J. Pareja, F. Fuest, M. Schütte, Y. Zhou, A. Dreizler, B. Böhm. Tomographic imaging of OH laser-induced fluorescence in laminar and turbulent jet flames. Measurement Science and Technology, in press https://doi.org/10.1088/1361-6501/aa938a

T. Li, J. Pareja, L. Becker, W. Heddrich, A. Dreizler, B. Böhm. Quasi‑4D laser diagnostics using an acousto‑optic deflector scanning system. Applied Physics B 123:78 (2017)

F. Eitel, J. Pareja, A. Johchi, B. Böhm, D. Geyer, A. Dreizler. Temporal evolution of auto-ignition of ethylene and methane jets propagating into a turbulent hot air co-flow vitiated with NOx. Combustion and Flame 117, 193-206 (2017)

O. Diemel, J. Pareja, A. Dreizler, S. Wagner. An interband cascade laser‑based in situ absorption sensor for nitric oxide in combustion exhaust gases Applied Physics B 123: 167 (2017)

F. Eitel, J. Pareja, D. Geyer, A. Johchi, F. Michel, W. Elsäßer, A. Dreizler. A novel plasma heater for auto‑ignition studies of turbulent non‑premixed flows. Experiments in Fluids 56: 186 (2015)

J. Pareja, C. Litterscheid, A. Molina, B. Albert, B. Kaiser, A. Dreizler. Effects of doping concentration and co-doping with cerium on the luminescence properties of Gd3Ga5O12:Cr3+ for thermometry applications. Optical Materials 47, 338-344 (2015)

J. Pareja, C. Litterscheid, B. Kaiser, M. Euler, N. Fuhrmann, B. Albert, A. Molina, J. Ziegler, A. Dreizler. Surface thermometry in combustion diagnostics by sputtered thin films of thermographic phosphors. Applied Physics B 117(1), 85-93 (2014)