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Rising fuel prices and more stringent requirements in the field
of exhaust emissions, such as NOx, PM and carbon dioxide are
significantly increasing the pressure on the manufacturers of
internal combustion engines of all categories to find, evaluate
and apply technologies that contribute to a reduction in these
emissions. As a result, interest in cylinder inner diameter surface
coatings has risen considerably in the last three to four years,
and particularly in the SUMEBore ® coating solution from Sulzer
Metco. Such coatings are applied by a powder-based atmospheric
plasma spray (APS) process. The APS coating process is
extremely flexible and can also process materials to which wirebased
coating processes do not have access. Particular advantages
become obvious when coatings are necessary made from high
chromium containing steels, metal matrix composites (MMCs)
or pure ceramics. The compositions of the coatings can be tailored
to the specific challenges in an engine, e.g. preventing excessive
abrasive wear, scuffing issues or corrosion attack caused
by bad quality fuels and/or high exhaust gas recirculation rates
(EGR). Cylinder liner surfaces from trucks, diesel locomotives
and marine propulsion, gas engines for power generation and
gas compression have been coated with such materials over
the past four to five years in small and large series production.
These engines have been tested successfully. Most of the tested
engines achieved significant reductions of lubrication oil consumption
(LOC), one of them in excess of 75%, reduced fuel
consumption, very low wear rates and corrosion resistance on
the liner surfaces, when compared with the currently uncoated
cylinder surface (baseline). The paper will introduce the APS
coating technology for ID cylinder surfaces and as an example
will highlight the coating of cylinder surfaces in a 4,000 hp
EMD 16-710G3 locomotive two-stroke diesel engine. Details of
the application of a corrosion resistant MMC coating will be
shown, together with results obtained with the Da Vinci DALOC
measurement technique in an engine test where the lubricant
oil consumption was accurately quantified at four steady-state
operating conditions typical of North American freight locomotive
and which clearly showed the significant contribution of the
liner ID coating to reduction of LOC. In addition, the paper will
give an example of an industrialised, fully automated SUME-
Bore coating equipment installed at a European truck OEM, for
the APS cylinder surface coating of up to 250,000 cylinder liners
for a truck engine.
Challenges for cylinder liner development
Per Ronnedal, MAN Diesel & Turbo, Denmark
Hirofumi Yamamoto, Toa Koki Co Ltd, Japan
Takayuki Goto, Mitsui, Japan
The two-stroke crosshead low-speed diesel engine has been
a preferred prime mover in the merchant marine for almost
a century. Although its basic working principle has not been
changed, the demand for even higher power, produced at the
lowest possible fuel consumption, from a machine occupying
a minimum of space, has constantly increased the demands to
its cylinder liner. This relates to both the thermal and mechanical
loading, and the tribological behaviour under ever changing
conditions. This paper gives a view on the development in
loading on the cylinder liner as one of the main engine components
to which it has developed over time. Special attention
is given to the recent development as a result of the high focus
on specific fuel oil consumption, and the thereby introduced
changes in the combustion conditions. New application of advanced
analysis method for acid attack on the running surface
of the cylinder liner is demonstrating how the new operating
conditions will affect the behaviour of the cylinder conditions,
and in consequence the cylinder liner. Countermeasures of
design and operational measures will be presented and service
examples will illustrate the validity of the conclusions and
countermeasures. As for the increased mechanical loading of
the cylinder liners, two main new designs will be demonstrated:
1) One new design relates to the mechanical design of the
cylinder liner, and how this design is able to withstand the
increased pressure from the diesel process. The cylinder liner
consists of a so-called ’strong back’ consisting of a steel bandage
shrink fitted to the upper part of the cylinder liner. The
increased strength of the steel in comparison with the cast iron
material thus results in a higher load capability. Service experience
of several years of operation is presented for reliability
confirmation.
2) The other design feature allowing an increased pressure is
based on development of a new material application: the socalled
CGI or Compacted Graphite Iron. This application has
been developed in tight cooperation with the Japanese cylinder
liner manufacturer Toa Koki. The paper describes the production
technique applied to achieve a stable yield. The merit in
terms of mechanical properties of the CGI is shown. Tribological
test data will be presented, and finally service experience
will be shown for a number of different engines. In summary,
it will be illustrated how modern diesel engine process and
application affects the cylinder liner, and how these effects are
overcome.
Development of new generation long life piston
ring coating for two-stroke large-bore marine
diesel engines
Yoshiyuki Saito, IHI Corporation, Japan
Takeshi Yamada, IHI Corporation, Japan
Yoshiyuki Umemoto, Diesel United, Ltd, Japan
Large-bore marine diesel engines equipped as main propulsion
on oceangoing large vessels like container ships and crude oil
tankers are supposed to possess very high reliability. One of the
main factors that affects the reliability of the main engines is the
stable sliding of piston rings and cylinder liners. IHI Corporation
and Diesel United have jointly conducted numerous basic
experiments and tests on wear monitoring between piston rings
and cylinder liners, and measurements of oil film thickness between
piston rings and cylinder liners of main engines on vessels
in commercial operation. The results obtained so far are
utilised in clarifying the abnormal sliding mechanism between
piston rings and cylinder liners that is hereafter referred as scuffing,
and in developing effective cylinder lubrication methods that
may be effective in preventing the scuffing. These activities have
lasted almost ten years. The findings obtained clarified the following
phenomenon. The scuffing is closely related to hard particles
contained in the fuel oil (FCC), and to changes of engine operating
conditions, typically the engine speed. Poor lubrication of
piston rings and cylinder liners to be caused by the above mentioned
effect is clarified to induce the scuffing. Research results
obtained during the period have clarified that the development
of cylinder lubrication systems is quite effective in avoiding the
poor cylinder lubrication. Furthermore, it is also important to develop
the piston ring coating that may prevent the rapid growth
of the scuffing phenomenon even when the poor cylinder lubrication
is initiated, and that make the piston rings strong enough
as to be immune to the presence of FCC on the sliding surfaces.
Meanwhile, some shipowners prefer to have longer overhauling
intervals matching with dry-dock interval due to economic reasons.
The scuffing resistance of piston rings and cylinder liners
May 2013 | Schiff&Hafen | Ship&Offshore SPECIAL 77