Etude de la combustion de gaz de synthèse issus d'un processus de ...
Etude de la combustion de gaz de synthèse issus d'un processus de ... 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). 142
Chapter 5 30 Piston position (mm) 20 10 0 92 93 94 95 96 97 98 99 100 Time (ms) Figure 5.4 – Peak detection filter. 5.1.1.3 Spark time tel-00623090, version 1 - 13 Sep 2011 Spark time is defined by the diagnostic system of the RCM in a time scale. Thus, this signal is independent of the piston displacement. In order to analyze the jitter of the spark time, figure 5.5 shows the three signals for the case of ignition at TDC and in addition the TDC position in a time scale. 6 Voltage (V) Piston position 5 4 3 2 1 Spark 0 135 136 137 138 139 140 141 142 143 144 145 Time (ms) Figure 5.5 – Spark time at TDC and TDC position signals. Analysing the figure 5.5 it is observed that the spark signal varies slightly (
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Chapter 5<br />
30<br />
Piston position (mm)<br />
20<br />
10<br />
0<br />
92 93 94 95 96 97 98 99 100<br />
Time (ms)<br />
Figure 5.4 – Peak <strong>de</strong>tection filter.<br />
5.1.1.3 Spark time<br />
tel-00623090, version 1 - 13 Sep 2011<br />
Spark time is <strong>de</strong>fined by the diagnostic system of the RCM in a time scale. Thus, this<br />
signal is in<strong>de</strong>pen<strong>de</strong>nt of the piston disp<strong>la</strong>cement. In or<strong>de</strong>r to analyze the jitter of the<br />
spark time, figure 5.5 shows the three signals for the case of ignition at TDC and in<br />
addition the TDC position in a time scale.<br />
6<br />
Voltage (V)<br />
Piston position<br />
5<br />
4<br />
3<br />
2<br />
1<br />
Spark<br />
0<br />
135 136 137 138 139 140 141 142 143 144 145<br />
Time (ms)<br />
Figure 5.5 – Spark time at TDC and TDC position signals.<br />
Analysing the figure 5.5 it is observed that the spark signal varies slightly (
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