CIMAC Congress - Schiff & Hafen

Monday, 14 June
Tuesday, 15 June
Wednesday, 16 June
Thursday, 17 June
predicted by the torsional vibration calculation was considered
during one cycle. The whole time step was divided by 72 steps and a
combined stress in every step was calculated. Fatigue safety was
calculated at the crank pin fillet, journal fillet and oil hole and a
critical damaged plane at each location was found by the FE analysis
using the stress gradient method. In case of analysis for the conrod,
the bearing force with more realistic oil film pressure was applied to
FE model. Based on the multistep analysis that the assembly
procedure is taken into consideration, the effective force and stress of
several weak points on fatigue damage were identified and fatigue
strength was evaluated.
Vibration characteristics of a V20 medium
speed gas engine – simulation and
measurement
R. Nordrik, H. Solbakken, Rolls-Royce Marine AS,
Norway
The paper describes the strategy for selection of ignition sequence for
a multicylinder V20 engine. The optimum choice is a compromise
between several parameters, among these are: free mass forces and
moments, inner bending moments, guide force and main bearing
force distribution. Torsional, axial and bending behaviour of the
driveline system is important as well as the vibration response of the
engine structure. Modern tools like Multi Body Simulation give
valuable insight into the dynamic behaviour of an engine. To make
proper use of this tool it is however necessaryto correlate the results
with measurements. The MBS model is an assembly of individual
FE-models coupled together with bolts, elastic elements, bearings,
couplings etc. The characteristics of these couplings have large
influence on the dynamic behaviour of the total system. In order to
get good simulation results the model need to be tuned by measured
values from an actual engine test. The paper discusses results from a
fullscale test of a V20 engine genset and how this influence the MBS
model setup and vibration results. It is demonstrated how the
vibration level can be changed by introducing a number of different
measures.
A single-phase flow model based on void
fraction for boiling heat transfer calculation
in cylinder head
Xincai Li, Shanghai Jiaotong University, Z. Chen,
Shanghai Marine Diesel Engine Research Institute,
P.R. China
Aiming at the heat-transfer phenomenon of sub-cooled boiling in
cooling water jacket of engine, a new computational model of boiling
heat transfer which is based on single-phase flow is presented
and established by means of the concept of void fraction (the percentage
of vapor in unit volume). The model is based on the assumption
that vapor and liquid are homogeneously mixed in the
boiling liquid. Therefore, the fluid is considered as a single-phase
flow in which gas and fluid are mixed homogeneously, and it can be
solved by the single-phase equation and model. With respect to the
boiling portion, where the two-phase flow can be reflected vividly by
the distribution of void fraction, the heat flux during the boiling heat
transfer is the sum of convection heat flux and the boil-off heat flux
of void fraction. The control equation with the variable of void fraction
is established by analyzing the micro-unit hexahedron of the
assumed homogeneous-phase fluid. This equation is calculated by
commercial computational software with some requisite subroutine.
And the calculated result of this single-phase boiling model is validated
with the third-party experimental results. Aiming at the application
of this computational model which is applied to the design of
cylinder head, the selected arrange of the void fraction is presented
and recommended, namely, the mean value of void fraction which
is located from the wall to the height of 5 mm is between 0.40 and
0.87. As a calculation instance, the numerical simulation on boiling
heat transfer process of cooling water jacket and temperature field in
cylinder head of the diesel engine is carried out. Compared with the
data measured on engine test bench, the calculated result indicates
that this method can reflect the boiling heat transfer in water jacket
rather accurately. So, this method benefits to improve the computational
precision in temperature field computation of cylinder head.
8:30 June 17th Room Klokkeklang
(5–4) Component & Maintenance Technology –
Piston Engines – Injection
Second generation of HFO injection system
for medium speed engines to fulfil future
requirements
C. Senghaas, H. Schneider, S. Reinhard, L’Orange
GmbH, Germany,
D. Jay, K. Ehrstroem, Wärtsilä Corp., Finland
Electrically-controlled common-rail fuel injection system can flexibly
manage to control fuel injection parameters (injection advanced
angle, injection pressure, injection duration and multi-injection)
within one working cycle of diesel engine, which helps to compromise
the optimal point of the engine power characteristics, economic
characteristics and emission performance. While, how to obtain a
set of optimum fuel injection parameters suiting to all working
condition and different operation environment of an engine is a big
burden. Because the process of obtaining optimum fuel injection
parameters, which is generally called of fuel injection system
calibration, mainly depends nowadays on experiment calibration by
bench testing experiments. The experiment calibration not only is
consumption a lot of labour, time and money but also can not be
performed for designing engine. A numerical calibration method is
presented in this paper. From the method a set of optimum fuel
injection parameters may be calculated by 1D simulation of whole
diesel engine working process and parameters comparison of
different calculation working condition. A 1D simulation model of a
4 cylinders diesel engine with turbocharger and inter cooler was set
up, which was installed an electrically-controlled commonrail fuel
injection system and its MAP of injection parameters was unknown.
From simulation calculations of the model, the power characteristics
like indicated power and torque moment, economic characteristics
like indicated specific fuel consumption and indicated thermal
efficiency, and emission performance like NOx and soot exhaust
quantities of this engine were calculated with different fuel injection
parameters. The simulation results of 25 operation conditions and
surveying results of bench testing experiment in the same operation
conditions of this engine were compared. With the fuel injection
parameters adjusted in simulation, a change pattern of performances
on power, economic and emission of the engine were calculated out.
When an optimum compromise performance parameter was selected
out from the change pattern of performance in a calculation working
condition of the engine, the optimum performance parameter is
approximately identical with experiment result at the same working
condition. It is indirectly proved that the optimum fuel injection
parameters calculated from simulation analysis is the optimum one
of meeting the engine optimizing performances requirement. Based
on the simulation model of this engine, optimum fuel injection
parameters were also obtained as the engine running in extreme
hard environment conditions (extreme high/low temperature and
high level altitude). The simulation result shows that the power,
No. 3 | 2010 | Ship & Offshore
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