The main focus of the Collaborative Research Centre 606 is
non-stationary combustion in internal combustion engines, combustion chambers
or gas turbines. Non-stationary combustion within the mentioned combustion
devices inevitably is connected with flame propagation under turbulent
conditions. For a comprehensive understanding of turbulent flame propagation
detailed experimental investigations are necessary and, particularly, research
is still necessary for the determination of the Markstein number during the
turbulent unsteady flame propagation as discussed in the review article
„Turbulent premixed combustion: Flamelet structure and its effect on turbulent
flame velocity” by Driscoll [1]. Motivated by this, the actual research
activities during the last period were focussed on the points mentioned in [1].
• The flame
surface during the non-stationary dispersion under turbulent conditions by
means of a newly developed measuring technique has been recorded and quantified
applying an adequate evaluation method.
• By this data on
the flame wrinkling as well as the laminar burning velocity of the stretched
flamelets were determined for the first time.
• On the basis of
this data resulting Markstein numbers were evaluated.
Encouraged by the results it is planned to extend the
research work on these topics during the next research period with the main
goals:
• Investigation of
operating conditions existing in internal combustion engines and
• Quantifying the
stretching of the flamelets.
In order to realise internal combustion engine conditions
the ignition has to be performed under elevated pressure and temperature. So,
the existing testing facility has to be upgraded. Using the above mentioned new
measuring technique the Markstein number during the unsteady flame propagation
under elevated pressure and temperature will be determined. Another aspect of
implementing the experimental conditions of an Otto engine concerns the proper
choice of the fuel. As a further step, in addition to gaseous fuels, it is
planned to extend the investigations using liquid fuels as well.
The stretching of the flamelets will be quantified by
measuring the flame structure as well as the velocity field using Particle Imaging Velocimetry (PIV). This
will bring about useful information concerning the verification of existing
models leading to the explanation of the influence of the turbulence on the
non-stationary flame propagation. The method will be applied to the evaluation
of isochoric combustion in an explosion vessel.
The increase in knowledge obtained by the described investigations is of
fundamental relevance for the projects B2, A5, B9(N) and B10(N). The
experimental results achieved by project A9 are necessary for the development
as well as the validation of models for turbulent burning velocity in
subproject B8 and of the combustion models developed within the mentioned
projects. Therefore, a close co-operation is already taking place or will be
arranged.
[1] J. F. Driscoll, Turbulent premixed combustion:
Flamelet structure and its effect on turbulent burning velocities, Progress in
energy and Combustion Science 43 (2008) pp. 91-134.
