•
Line 2 is the overload limit. This is a constant MEP line from 100% power and 93.8% speed
to 110% power and 103.2% speed. 103.2% speed is the intersection point between the
nominal propeller property and 110% power.
•
Line 3 is the 104% speed limit where an engine can operate continuously. For R
X
with
decreased speed (N
CMCR
≤0.98
NMCR
) this limit can be extended to 106%, but, the torsional
vibration must not be more than the specified limits.
•
Line 4 is the overspeed limit. The overspeed range between 104% (106%) and 108% speed
is only permitted during sea trials if necessary. This is to demonstrate the speed of the ship
at CMCR power with a light running propeller in the presence of authorized representatives
of the engine builder. The torsional vibration must not be more than the specified limits.
•
Line 5 is the permitted torque limit from 95% power and speed to 45% power and 70%
speed. This shows a curve defined by the equation: P
2
÷ P
1
= (N
2
÷ N
1
)
2.45
. When the engine
speed and power is near the data in Line 5 there will be a decrease in scavenge air, which
has an effect on the engine. The area between Lines 1, 3 and 5 show the range in which
the engine must be operated. The area in the nominal propeller property, 100% power and
Line 3 is recommended for continuous operation. The area between the nominal propeller
property and Line 5 must be reserved for acceleration, shallow water and usual flexibility of
operation.
•
Line 6 gives the equation: P
2
÷ P
1
= (N
2
÷ N
1
)
2.45
through 100% power and 93.8% speed and
the maximum torque limit in transient conditions. The area above Line 1 is the overload
range. You must only operate the engine in this range for a maximum of one hour during
sea trails in the presence of authorized representatives of the engine builder. The area
between Lines 5 and 6 and the constant torque line (shown as a dark area) must only be
used for transient conditions, ie during fast acceleration. This range is known as the service
range with operational time limit.
X72-B
AA00-0000-00AAA-042B-A
Operation Manual The relation between engine and propeller
Winterthur Gas & Diesel Ltd.
- 70 - Issue 003 2021-12
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