The 4T50ME-GI Test Engine at MAN Diesel & Turbo's ... - Sae.org

7 Potential Applications for ME-GI
Engines
As previously mentioned, the ME-GI
engines – originally designated MC-GI
– were developed for LNG carrier pro-
pulsion. In the project phase, the ME-GI
was recommended for the now-famous
45-strong Qatargas fleet of Q-Flex and
Q-Max LNG carriers built for the mas-
sive expansion of gas exportation from
Qatar in the Persian Gulf.
However, the shipowner selected
the heavy fuel variant and, accord-
ingly, each of these vessels has 2 × 6
7S70ME-C HFO engines installed. In
the meantime, the relative pricing of gas
and fuel has changed in some parts of
the world and a retrofit project is now in
the shaping, with some of these vessels
as candidates for retrofit to 2 x 6 type
7S70ME-GI.
These vessels already have a relique-
faction plant on board so therefore the
gas-supply train to the engines features
a cryogenic pump/evaporator. It is es-
timated that such a retrofit installation
would take about one year to prepare,
followed by 4 - 6 weeks re-building,
which typically would take place during
a regular survey docking. Fig. 16 shows
a Gant diagram for such a conversion.
The ME-GI engine can also be seen as
a way of simultaneously meeting Tier-III
emission limits and fuel-sulphur con-
tents/SO x emission limits. With natural
gas being sulphur free, SO x emissions
from an ME-GI engine are limited to that
emitted by the burning of pilot oil.
The extremely low SO x emissions from
an ME-GI engine also facilitate the nec-
MAN B&W Diesel
essary Tier-III NO x control abatement
methods for two-stroke engines, SCR
( Selective Catalytic Reduction ) and
EGR (Exhaust Gas Recirculation ). For
SCR, the SO x in the exhaust limits the
temperature regime in which the reac-
tion can take place while for EGR, the
exhaust gas to be recirculated needs to
be cleaned and cooled before returning
to the engine. This is obviously much
cleaner when derived from an ME-GI
combustion. Therefore, an ME-GI en-
gine with SCR or EGR could constitute
a Tier-III, low-speed engine as an alter-
native to an ME-type HFO engine with
SCR or EGR and SO X scrubber.
The fact that natural gas is generally
cheaper than HFO on a calorific input
basis, while low-sulphur or even sul-
phur-free fuels are significantly more ex-
pensive than HFO, supports the use of
ME-GI engines.
The regulatory environment is practical-
ly in order already and the logistics for
running on gas will come with demand.
Accordingly, advanced shipbuilders –
particularly in Japan and Korea – are
already marketing containerships, tank-
ers and bulk carriers powered by ME-
GI engines. Bringing development one
step further, MAN Diesel &Turbo has
recently also decided to advocate the
use of LPG and other VOCs (Volatile
Organic Compounds) in a variant of the
ME-GI engine. This will be designated
ME-LGI (for Liquid Gas Injection). While
the ME-GI probably will be used mostly
in larger vessels on longer routes, the
ME-LGI will be used more predomi-
nantly in short-sea shipping due to the
easier logistics offered by LPG/VOC.
Conclusion
There is plenty of gas available in the
world, with some sources evaluating its
reserves as even greater than oil. The
main drivers for using gas at sea are
first and foremost environmental con-
siderations – including a great reduction
in CO2 emissions – but the cost of the
various fuel types are also an important
factor. MAN Diesel & Turbo sees great
potential in the use of gas aboard ships
and is allocating substantial research
efforts towards developing suitable
technologies to this end.
The 4T50ME-GI Test Engine at MAN Diesel & Turbo’s Copenhagen Test Centre
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