Dr.-Ing. Ayane Johchi

Kontakt

Work Otto-Berndt-Str. 3
64287 Darmstadt

Humboldt Research Fellow (Dec. 2016-Nov. 2018)

Research interest:

  • Turbulent combustion
  • Auto-ignition of turbulent flow
  • Local flame structure of turbulent premixed
  • Multi-dimensional and multi-variable laser diagnostics

Research Project Description

Novel 2D multi-scalar measurements for auto ignition studies

Combustion supplies more than 80% of the primary energy in the world and hence development of highly efficient and low-emission combustion devices are required to solve global energy and environmental issues. Understanding, modeling, and controls of turbulent combustion are necessary. In combustion research, huge attention has been given to a fully burning state of the turbulent combustion such as heat release, pollutant emission or extinction. In many combustion devices, however, auto ignition (AI) of turbulent flows plays an important role as the onset of the reactions. It must be well controlled to initiate an operation in compression ignition (CI) engines, while it must be avoided in spark ignition (SI) engines and in lean premixed prevaporized (LPP) gas turbines. In spite of its importance AI of turbulent flows is not well characterized especially under operating conditions of practical devices. Flammable mixtures above a certain temperature start to react slowly, and generate heat, which increases the temperature further, thus providing a faster heat release rate. In this way the reaction accelerates at increasing tempo, after a certain induction time, high temperature reactions followed with significant heat release. AI is this transition to the fully burning state triggered by low-temperature reactions.

Experimental data is required for better understanding of AI of turbulent flow, especially for high Re-number flows that are prohibitive for direct numerical simulation (DNS) with current computer resources. Laser and optical based diagnostics is the most suitable technique to measure scalars non-intrusively with high temporal and spatial resolution. However, the diagnostic technique to realize simultaneous temperature and state of turbulent mixing (i.e. mixture fraction) that are important parameters of AI is still an open issue to be developed.

The aim of the current research project is therefore to develop a multi-scalar laser diagnostic technique to better characterize AI under the condition at both high temperature and turbulent intensity. Simultaneous temperature/mixture fraction measurement technique based on Rayleigh scattering thermometry and quantitative planar laser induced fluorescence (PLIF) of nitric oxide is developed. The multi-scalar measurement technique is designed to achieve high accuracy and high sensitivity specifically to study AI of methane jets propagating into a turbulent hot air co-flow. The simultaneous measurement was carried out upstream of apparent AI kernels and stabilization regions of a lifted jet flame formed by a fuel jet composed of CH4/CO2, propagating into a hot air co-flow. By applying the developed technique to the auto-igniting turbulent flow field with various co-flow temperature and turbulent intensity, AI of turbulent flows such as preferred conditions promoting/retarding AI and turbulent-chemistry interaction are better understood.

CURRICULUM VITAE (wird in neuem Tab geöffnet)

List of publications (wird in neuem Tab geöffnet)