Etude de la combustion de gaz de synthèse issus d'un processus de ...

Experimental study of engine-like turbulent combustion
single compression experiments performed enables to define a typical scattering on
less than 4.0 mm (from -13 mm to -17 mm).
The TDC position has also some scattering but only of 1 mm (from 419 mm to 420 mm)
which could be endorsed to some mechanical deformation imposed by elevated incylinder
pressures. Considering a piston stroke of 419 mm, the overall uncertainty of
the piston initial position is lower than 1.0%. This jitter on the initial position can be
converted to time scale by considering the average piston speed of 9.5 m/s. This
conversion gives a maximum value of 0.42 ms.
Considering that the volume inside the chamber is obtained from the piston position,
the influence of this jitter on the piston position from one experiment to another is then
analyzed in figure 5.3 for the case of updraft syngas without combustion in order to
tel-00623090, version 1 - 13 Sep 2011
avoid the effect of the spark time scattering. The choice of the same fuel also avoids
differences in the polytropic coefficient of the mixture being compressed.
In the case shown in the figure 5.3, the difference in the initial piston position is 1.75
mm. It is observed that there is no significant difference on the piston position along
time.
450
Piston position (mm)
360
270
180
90
0
90 100 110 120 130 140
Time (ms)
Figure 5.3- Piston displacement during single compression of updraft syngas-air.
From figure 5.3 it is also observed the evolution in a “stair” mode of the laser piston
position signal. As the in-cylinder volume variation is obtained from this signal,
therefore a peak detection filter was applied to this signal (figure 5.4).
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