1.3.6
Calculations for Brake Mean Effective Pressure (BMEP)
Calculation shall verify that the diesel engine meets the specified maximum
BMEP as follows:
a.
kW: Minimum power rating of engine-generator set as defined in the
paragraph entitled "Engine-Generator Set Ratings and Performance."
b.
rpm:
Engine revolutions per minute.
c.
liters cu. in.:
Total engine piston displacement in liters cubic inches.
d.
GEN.EFF.:
Generator efficiency.
e.
x:
Multiplication sign.
f.
bkW' bhp': Brake kW horsepower required from diesel engine by
generator loaded to full power rating.
g.
bkW' bhp':
kW/GEN.EFF. kW/(GEN.EFF. x 0.746).
h.
bkW" bhp": Brake kW horsepower required by diesel engine driven fan
for cooling radiator or motor driven fan for cooling radiator.
i.
bkW bhp:
bkW' + bkW" bhp' + bhp".
j.
BMEP kPa psi: (120,000 x bkW) (792,000 x bhp)
/(rpm x liters cu. in.).
1.3.7
Torsional Vibration Stress Analysis Computations
Torsional vibrational stresses in the crankshaft and generator shaft of
assembled diesel engine and driven generator shall not exceed 34,450 kPa
5000 psi when engine is driving generator at rated speed while assembled
unit is loaded to rated engine-generator set power. Computations shall be
based on a mathematical model of the assembled generator set provided or
based on calculations using measured values from tests on a unit identical
to the one provided. Calculations based on models of, or measured data
from, the unassembled engine and generator will not be acceptable.
Calculations shall include:
a.
A description of the system relating information pertinent to analysis
such as operating speed range and identification plate data.
b.
A mass elastic assembly drawing, showing the arrangement of the units
in the generator set and dimensions of shafting, including minimum
diameters (or section moduli) of shafting in the system.
c.
A labeled line diagram of the mass elastic system indicating values of
masses, stiffness, equivalent lengths, and equivalent diameters
including basic assumptions and definition of terms.
d.
Sample computations showing procedures used to obtain resulting stress
values.
e.
Computations indicating assembled engine-generator speed of 1800 rpm
with assembly loaded to rated generator power and the resulting
computed critical torsional stress values in the assembled engine
crankshaft and generator shaft.
SECTION 16237N
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