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Cimac Congress | Shanghai 2013
Jenbacher customer fleet over hundreds of thousands of engine
operating hours combined with the broad variety of customer operating
conditions have been at the core of developing accurate reliability
models down to the component level. This data has been
further analysed through the use of Design for Reliability (DFR)
tools and processes to allow clear failure mode identification and
determination of key failure mode accelerating factors. This is key
in predicting the response of current components placed under
new boundary conditions, i.e. higher pressures and temperatures.
Single cylinder testing has been used to gather the detailed component
operational data to allow this correlation to occur. These
factors have then been used as assessment criteria within the design
and analysis of the new cylinder head. The new cylinder head
assembly is a design that incorporates both a different material,
a new head structure and with a new water jacket design that includes
cooled exhaust valve seats. The new cylinder head assembly
has been subjected to an extensive design and analysis optimisation
process involving multiple iterative FEA and CFD loops, full
conjugate heat transfer analysis and a number of breakout studies
to examine the detail of certain components within the assembly.
Confidence in the analysis methodologies has been further increased
by extensive single cylinder testing of the current production
cylinder head. This allowed a closed loop correlation process
to be established in order to increase accuracy of the analytical
approach and thereby allow the design of the new cylinder head to
progress with high confidence. Specific accelerated tests were developed
for the full-sized development engines in order to confirm
reliability predictions on both the baseline and newly developed
cylinder head. These tests incorporated the key accelerating factors
identified from the previous SCE work, and were successful in initiating
predicted failures on the original head. The same tests were
then used to demonstrate the robustness of the new cylinder head
when placed under the same test conditions.
Low vibration design of large diesel and gas engines
by predictive simulation
Martin Wyzgala, MAN Diesel & Turbo SE, Germany
Peter Boehm, MAN Diesel &Turbo SE, Germany
Dietmar Pinkernell, MAN Diesel & Turbo SE, Germany
Diesel and gas engines are considerably excited to structural vibrations
by enormous forces caused primarily by fuel combustion and
moved crank drive masses. Customers and classification societies
demand low vibration engines. At MAN Diesel & Turbo (MDT),
the engine vibration is limited to an acceptable level by purposive
measures regarding the engine design already during concept and
detail design phase – long before the first engine test and measurements
are possible. Front loading by virtual engineering plays an
essential role in the development process of diesel and gas engines.
By combining engineering tools for analysis, simulation and optimisation,
virtual engineering facilitates a multi-disciplinary and
resultoriented product development. It supports classical design
approaches as well as traditional experimental testing and validation.
Virtual engineering assists the development process from the
very first design idea to the final validation of the product. MDT
demonstrates successful frontloading by means of the exemplary
resiliently mounted 20V 35/44G engine, its latest four-stroke
medium-speed gas engine for power plant applications. MDT designs
a low-vibration engine, even though facing new, challenging
boundary conditions such as high mechanical efficiency, higher
firing pressures, and light-weight design. In addition to topology
optimisation of the crankcase and an investigation of different firing
sequences, an essential element in vibration optimisation is
a highly advanced vibration analysis and simulation process delivering
accurate, reliable and predictive results. The vibrations of
entire engines are investigated by means of FE simulations and
appropriate shell models. Because of its comparably small size
and their parametric properties, an evaluation of a high number
of design variants within an admissibly short time is feasible. The
simplification of the complex solid geometries to a mid face design
of a shell model inevitably implicates deviations. However an
optimum quality of the simulation model is indispensible. Therefore
an updating procedure on numerical basis is introduced,
which is already performed by standard long before any engine
part is available in hardware for an experimental modal analysis.
Moreover, the numerical method offers equivalent results, that a
late and expensive test of core assemblies is not required. Each
derived model of a core part e.g. the crankcase, base frame and
turbo charger attachment is updated with respect to its original
structural properties. The updating is carried out once firstly by
correlating modal results like eigenfrequencies and mode shapes
of reference solid FE models and their corresponding shell models
and finally by adjusting parameters such as material properties,
element thickness or mesh density. More detailed information
about the model updating procedure will be given by the paper.
Due to certain tolerances of boundary conditions, such as damping,
non-linearity and fabrication tolerances, local inaccuracies
will always exist. Local systems can react not exactly as predicted.
Nevertheless MDT is conscious of these remaining, local inaccuracies
and is taking them into account already during the concept
and detail design phase. Local design alternatives are determined
by help of the vibration simulation and hold available for testing.
If necessary, the appropriate solution is chosen and verified by
measurement. High costs and long-testing periods for the product
validation are avoided. Finally, the comparison of simulation and
measurement results received later from the test bed illustrates,
that the simulation has an excellent quality and accuracy. Having
established the presented simulation process, MDT possesses the
proper methods and tools respectively know-how, in order to cope
with the ambitious engine design demands. This ends up in a low
vibration design of new medium-speed engines taking care of customer
needs and assuring a safe long-term operation without the
necessity of spacious, costly and less reliable external equipment
increasing damping respectively decreasing vibration.
Structural optimisation method and low vibration
design of HiMSEN engine’s genset
Kun-Hwa Jung, Hyundai Heavy Industries Co, Ltd, South Korea
Jun-Ho Lee, Hyundai Heavy Industries Co, Ltd, South Korea
Jung-Ho Son, Hyundai Heavy Industries Co, Ltd, South Korea
Young-Seok Ryoo, Hyundai Heavy Industries Co, Ltd, South Korea
Recently, a diesel engine that has more specific power output and
compact feature was developed to cope with customer’s needs.
From a vibration point of view, high power output results in increasing
the excitation force and compact design reduces the structural
rigidity. Antivibration design of a diesel engine is necessary
to prevent high vibration and durability problem. Since the beginning
of HiMSEN engine’s production in the year 2000, HHI has
made a remarkable effort to reduce the vibration level of engine.
HHI has provided suitable solutions for various characteristics of
excitation force and genset’s configuration using the measurement
and FE-based simulation technique. Vibration response prediction
is made by two FE-solving schemes that are a frequency-domain
and time-domain analysis technique. These days, the flexible
multibody dynamic (MBD) simulation based on the timedomain
analysis technique is more popularly used because the nonlinear
characteristics of mount, journal bearing and interactions between
shaft and engine body can be considered. The MBD-based realistic
simulation was applied to newly developed HiMSEN engines,
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Schiff&Hafen | Ship&Offshore | May 2013