8.3
Surge Tests
For two-stroke applications in particular, the operating curve shifts toward
the surge line by closing the VTA – see Fig.
engine with VTA closing towards part load
Therefore, attention is to be paid that surge tests, as far as possible, are car-
ried out in closed condition according to the later movement program.
Therefore, the following procedure is required for the load shedding test of
the two-stroke engine:
1. Load reduction from 75% to 25% within 10 seconds for checking the
surge stability in closed condition of the VTA, whereby the maximal igni-
tion pressure must not be exceeded.
2. Load reduction from 100% to 50% according to standard procedure,
yet with activated movement program. Here, the result strongly
depends on the control algorithm and the adjustment speed of the VTA.
Compressor pressure ratio
Volumetric flow rate
Figure 19: Operating curve, two-stroke engine with VTA closing toward part load
2013-12-04 - de
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8.3 Surge Tests
MAN Diesel & Turbo
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