VAF instruments 667 - 7.7 METHOD OF CALCULATIONS; Power, Energy, and Flow Calculations

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7.7 METHOD OF CALCULATIONS
Shaft power
Shaft power is calculated from the measured torque and the revolutions of the shaft.
𝑷 = 𝑴 ∙ 𝒏 ∙
𝟐∙𝝅
𝟔𝟎
(F1)
P
= Shaft power
[kW]
M
= Torque
[kNm]
n
= Rotations per minute
[rpm]
Total energy
Total energy is calculated from the integrating shaft power over time
𝑬 =
∑
𝑷
𝒕𝒕
∙ ∆𝒕 (F2)
E
= Total energy
[kWh]
P
t
= Power at time t
[kW]
Dt
= Sample rate
[sec]
Specific gravity
The fuel oil specific gravity is a fixed or measured (ViscoSense
®
3D) value in the PEM4 + SPU3 system.
The reference temperature (15.6⁰C default) can be set per fuel type.

T
= Specific gravity at T temperature
[kg/l]

15.6
= Specific gravity at reference temperature
[kg/l]
Fuel oil consumption
Fuel oil volume flow measured by our VAF Series PT2 flowmeter is giving a fixed number of pulses per
litre to the SPU3. Volume flow calculation is as follows:
∆V =
∆𝒑
𝑲_𝒇𝒂𝒄𝒕𝒐𝒓
(F3)
DV
= Volume from one measurement
[litres]
Dp
= Number of pulses
[p]
K_factor
= Pulses per litre from flowmeter
[p/l]