Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND SYSTEM FOR IMPROVING FUEL ECONOMY
AND ENVIRONMENTAL IMPACT OPERATING A 2-STROKE
ENGINE.
FIELD OF THE INVENTION
The invention relates to a method of reducing fuel consumption, lubricant
complexity and environmental impact in the operation of a two-stroke engine.
Further, the invention relates to a system for reducing fuel consumption,
lo extended lubricant utilization and environmental impact in a two-stroke
engine.
BACKGROUND OF THE INVENTION
Two-stroke cross-head engines used in marine and/or stationary applications
are equipped with two separate lubricating oil systems. One lubricating
system comprises so-called system oil that normally is used for lubrication
and cooling of the engine's bearings and e.g. oil-cooled pistons as well as
for
activation and/or control of various valves or the like. The other lubricating
system comprises an all-loss lubricant (cylinder oil) that normally is used
for
lubrication of the engine's cylinders, piston rings and piston skirt.
In typical two-stroke cross-head engines, the cylinder oil is spent
continuously by each turn of the engine whereas the system oil in principle is
not spent (except by smaller unintentional leakages). The lubrication system
comprising the cylinder oil is also often referred to as an "all-loss"
lubrication
system as the oil is spent. The use of and various types of both system oil(s)
and cylinder oil(s) is very well known in the art.
The cylinder oil typically contains certain additives that function to reduce,
minimize or neutralise the acid level of the cylinder system.
Typical cylinder oils usually have an SAE (Society of Automotive
Engineering) viscosity equivalent to about 50 and normally have a total base
number (BN) of about 40 to 70 for the neutralisation of acid products
produced during the combustion process. Typical system oils usually have an
SAE viscosity of about 30 with a relatively low BN content, typically around 5
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and provide long-time performance. These exemplary values may vary
dependent on the actual application and the specific design of the systems
that the oils are used in.
In recent two-stroke cross-head engine designs involving electronic and/or
hydraulic control and/or activation of valves, etc., the minimum performance
requirements of the system oil has been substantially increased compared to
earlier design using traditional mechanical control/activation.
The performance level of lubricants is typically measured periodically and
may not go beyond certain limits if the oiled component's condition should
not be jeopardized. One cause of performance loss is caused by particle
contamination. These particles include combustion by-products and wear
components, which can be partially removed by oil separators. However, in
the case of two-stroke cross-head engines, one of the sources of
contamination is spent cylinder oil leakage past the stuffing box causing both
the viscosity and base number of the system oil to increase over time, a
process that cannot be reversed by separators. This causes the system oil to
gradually degrade over time so component wear increases and engine
efficiency decreases. When the system oil is approaching its condemning
limit it will have to be replenished or changed.
Patent specification US 6.074,995 discloses a friction modifier composition
comprising an oil of lubricating viscosity and containing a friction-reducing
amount of an additive.
Patent specification US 5,282,990 discloses adding a synergistic blend of
friction modifiers to a crankcase lubricating oil of an internal combustion
engine in order to improve the fuel economy. However, there is no
suggestion of how to apply this with respect to a two-stroke diesel engines.
Patent specification EP 0 573 231 discloses triglycerides as friction
modifiers
added to oil for improved fuel economy in an internal combustion engine.
Patent application US 2003/0171223 discloses lubricating oil compositions
with improved friction properties.
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OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and a
corresponding system of reducing fuel consumption and environmental
impact operating a two-stroke engine that solves the above-mentioned (and
other) shortcomings of prior art. A further object is to provide this in an
easy
and efficient way.
A further object of the present invention is to enable improvement of fuel
economy or fuel efficiency in a two-stroke diesel engine.
Another object is to reduce emissions from a two-stroke diesel engine.
Another object is to enable use of a less-complex consumable system oil yet
is providing the same performance levels as experienced with conventionally-
formulated system oils.
Yet another object is to enable extended component life of a two-stroke
diesel engine.
An additional object is to provide a more environmentally friendly operation
of
the engine.
These objects, among others, are achieved by a method (and a
corresponding system) of reducing fuel consumption in a two-stroke engine
comprising the steps of: obtaining system oil/consumable system oil from an
engine, adding at least one friction modifier to at least a part of the
obtained
system oil, where the addition of the at least one friction modifier reduces
the
friction coefficient of the obtained oil, resulting in a system oil/consumable
system oil with reduced friction, and supplying said oil with reduced friction
to
said engine.
In this way, the fuel consumption of the engine is reduced, i.e. improved fuel
economy is obtained, due to the presence of the added friction modifier(s)
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giving the system oil/consumable system oil fed back into the engine reduced
friction characteristics.
Additionally, extended component operational time is obtained since less
friction is present between the components of the engine(s) due to the
addition of the friction modifier(s). This results in less frequent
maintenance
and savings of costs.
Further, reduced emissions from the engine(s) are obtained since less fuel is
used due to the less friction between engine components obtained by the
addition of the friction modifier(s) according to the present invention.
In one embodiment, at least one of the friction modifier(s) is/are an ash-less
friction modifier.
In one embodiment, the at least one ash-less friction modifier is based on di-
,
tri- and/or tetra-esters of dimeric and/or fatty acids and/or fatty amides.
In another embodiment, the at least one ash-less friction modifier is based on
neopentylglycol, pentaerythritol, sorbitol, trimethylpropanol, glycerol and/or
triethanolamine or blends thereof.
In a preferred embodiment, the at least one friction modifier is based on one
or more selected from the group of:
= triglycerides (of animal and/or vegetable origin), such as rape seed,
soy bean, and/or castor oil,
= fatty phosphates,
= fatty acid amides,
= fatty epoxides,
= borated fatty epoxides,
= fatty amines, e.g. triethanolamine
= polyol esters, e.g. of glycerol, pentaerythritol, neopentylglycol, sorbitol,
trimethylpropanol,
= borated polyol esters alkoxylated fatty amines,
= borated alkoxylated fatty amines,
0 metal salts of fatty acids,
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= sulfurized olefins,
= fatty imidazolines, or
= mixtures thereof
5 In one embodiment, the least one friction modifier is added at a
predetermined rate so that the concentration of the added friction modifier(s)
has a concentration of 0.2 - 2.0 % of said system oil/consumable system oil
with reduced friction.
In an alternative embodiment, the at least one friction modifier is added at a
predetermined rate so that the concentration of the added friction modifier(s)
has a concentration of 0.5 - 1.5 % of said system oil/consumable system oil
with reduced friction.
In an alternative embodiment, the method involves use of a consumable
system oil, containing a simplified additive composition and/or a reduced
additive treat rate.
In one embodiment, the method is used offshore, on-site, on-board a vessel,
and/or in a land based plant.
In a preferred embodiment, the method further comprises the step of: tapping
a predetermined first amount of the system oil/consumable system oil
providing tapped oil and replenishing the remaining system oil/consumable
system oil with a predetermined second amount of fresh(er) system
oil/consumable system oil, with tapping and/or replenishing done
continuously, near-continuously or intermittently.
In another preferred embodiment, the method further comprises the steps of:
creating a cylinder oil on the basis of the tapped system oil/consumable
system oil by determining at least one critical parameter (e.g. BN, viscosity,
permitfiivity/capacifiance and/or elemental composition) of the tapped oil,
determining at least one desired parameter (e.g. BN, viscosity,
permittivity/capacitance and/or elemental composition) of the cylinder oil and
adjusting said at least one critical parameter (e.g. BN, viscosity,
permittivity/capacitance and/or elemental composition) of the tapped system
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oil/consumable system oil accordingly by blending the tapped oil with at least
one BN modifying additive resulting in a created cylinder oil, and supplying
said created cylinder oil to cylinders or part of the cylinders of said
engine.
In one embodiment, the system oil is selected from the group of:
- a traditional system oil comprising additives for long-time performance or
formulated with an additive treat-rate providing long-time performance, and
- a consumable system oil without long-time performance additives or
formulated with a reduced additive treat-rate not providing long-time
performance.
The present invention also relates to a system for reducing fuel consumption
in a two-stroke engine, which corresponds to the method of the present
invention and have the same advantages for the same reasons.
More specifically, the inVention relates to a system for reducing fuel
consumption in a two-stroke engine comprising a blending unit for adding at
least one friction modifier to at least a part of an obtained system
oil/consumable system oil, where the addition of the at least one friction
modifier reduces the friction coefficient of the obtained system
oil/consumable system oil, resulting in a system oil/consumable system oil
with reduced friction and for supplying said system oil/consumable system oil
with reduced friction to said at least one engine.
Advantageous embodiments of the system according to the present invention
are defined in the sub-claims and described in detail in the following. The
embodiments of the system correspond to the embodiments of the method
and have the same advantages for the same reasons.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the invention will be apparent from and
eiucidated with reference to the illustrative embodiments shown in the
drawing, in which:
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Figure 1 shows a schematic block diagram of one embodiment of the present
invention;
Figures 2a and 2b illustrate the effects of the present invention during a
test.
DESCRIPTION OF PREFERRED EMBODIMENTS
Figure 1 shows a schematic block diagram of one embodiment of the present
invention. Shown is a schematic representation of at least one two-stroke
cross-head diesel engine (300). The engine comprises one lubricating
system comprising so-called system oil (301) that normally is used for
lubrication and cooling of the engine's bearings and e.g. oil-cooled pistons
as
well as for activation and/or control of various valves or the like. Another
lubricating system comprises an all-loss lubricant or cylinder oil (302) that
normally is used for lubrication of the engine's cylinders, piston rings and
piston skirt.
The engine (300) corresponds to well-known prior art two-stroke engines
except as explained in the following.
Also illustrated is, according to the present invention, a friction modifying
method/system (100) reducing fuel consumption in a two-stroke engine. The
friction modifying method/system (100) obtains system oil (301') from at least
one engine (300) where a controller or blending unit (102) adds at least one
friction modifier (101) to (at least a part of) the obtained oil (301'). The
addition of the at least one friction modifier (101) reduces the friction
coefficient of the obtained system oil/consumable system oil (301'), resulting
in a system oil with reduced friction (301"), which is supplied back to the
engine(s) (300) as system oil.
This results in avoiding or minimising frictional losses caused by
contamination of the system oil/consumable system oil, which normally takes
place as the oil is used and which would otherwise cause substantial
diminished efficiency, increased fuel consumption and increased emissions.
Great economical savings are achieved by avoiding this.
The system oil is preferably selected from the group of:
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- a traditional system oil comprising additives for long-time performance or
formulated with an additive treat-rate providing long-time performance, and
- a consumable system oil without long-time performance additives or
formulated with a reduced additive treat-rate not providing long-time
performance.
Preferably, the friction modifier(s) (101) is/are ash-less friction
modifier(s),
which may be based on di-, tri- and/or tetra-esters of dimeric and/or fatty
acids and/or fatty amides.
The ash-less friction modifier(s) may also be based on neopentylglycol,
pentaerythritol, sorbitol, trimethylpropanol, glycerol and/or triethanolamine
or
blends of two or more of the above.
In a preferred embodiment, the least one friction modifier may be based on
one or more of: triglycerides, such as castor oil, fatty phosphates, fatty
acid
amides, fatty epoxides, borated fatty epoxides, fatty amines, e.g.
triethanolamine, polyol esters, e.g. of glycerol, pentaerythritol,
neopentylglycol, sorbitol, trimethylpropanol, borated polyol esters
alkoxylated
fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids,
sulfurized olefins, fatty imidazolines, or mixtures thereof
The friction modifier(s) may also be other compounds, e.g. as disclosed in
the cited prior art documents and elsewhere. See e.g. patent specification US
4,792,410 and US 5,110,488.
According to one embodiment, the friction modifier(s) (101) is/are added at a
predetermined rate so that the concentration of the added friction modifier(s)
(101) has a concentration of 0.2 - 2.0 % of the system oil/consumable
system oil with reduced friction (301"). In an alternative embodiment, the
friction modifier(s) (101) is/are added at a predetermined rate so that the
concentration of the added friction modifier(s) (101) has a concentration of
0.5 - 1.5 % of the system oil/consumable system oil with reduced friction
(301"). According to another embodiment, the controller or blending unit
(102) varies the rate of added friction modifier (101) according to a
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predetermined scheme, i.e. so not necessarily the same rate is used all the
time.
According to one embodiment, the system oil/consumable system oil is a
consumable system oil having a reduced and/or modified additive
composition reflecting its reduced oil life.
The present invention may e.g. be used offshore, on-site, on-board a vessel,
and/or in a land based plant or the like.
According to a preferred embodiment of the present invention, the
system/method further comprises a tapping and replenishing system/method
(200) where a controller (202) controls tapping a predetermined amount of
the obtained system oil/consumable system oil (301') providing tapped oil
(203) and replenishing the remaining system oil/consumable system oil (301)
with a predetermined second amount of fresh(er) system oil/consumable
system oil (201). In this way, a part of the system oil/consumable system oil
to be added with a friction modifier is replenished. Alternatively, the
tapping
and/or replenishing may be done continuously, near-continuously,
intermittently or according to other suitable schemes.
As used system oil/consumable system oil is tapped and replenished with
fresh, unspent or less spent system oil, the resulting system oil/consumable
system oil is of a more consistent quality and gradual deterioration is
minimised or avoided. In this way, enhanced and consistent performance of
the initial fluids resulting in further reduced component wear and equipment
lifecycle cost is provided.
In effect, this provides a 'consumable' system oil/consumable system oil as a
part of the spent system oil/consumable system oil is tapped and replenished
with fresh or fresher system oil. This is novel compared to prior art system
oil/consumable system oil where the system oil/consumable system oil is
kept in the engine system until about it has been degraded too much for
efficient use. After this it has to be replaced and the spent system
oil/consumable system oil would have to be handled as waste. A further
advantage of this is that the requirements for the system oil/consumable
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system oil in this system are different than prior art requirements. Standard
system oil/consumable system oil for prior art systems usually contains an
additive package to secure a long lifetime of the system oil. System
oil/consumable system oil with a prior art additive package is significantly
5 more expensive than a similar system oil/consumable system oil without the
prior art additive package or with a new additive package designed for a
"consumable" system oil. The present system can function with system
oil/consumable system oil using a reduced and/or modified additive package
ensuring sufficient oil life since it is tapped and replenished. This leads to
lo reduced expenses since cheaper oil can be used in the system. Preferably,
the tapped oil is used instead of becoming waste as described in the
following.
The tapping/replenishment system (200) may feed directly into the engine or
be part of a separate loop, instead of the one used for addition of friction
modifier(s) to the system oil/consumable system oil (301') .
In another preferred embodiment, the system/method further comprises a BN
modifying system/method (400) that converts used system oil/consumable
system oil into useable cylinder oil. See e.g. patent specifications US
Provisional 60/612,899 and European patent application number
04388064.0, both of the same applicant and both incorporated herein by
reference, for specific details of one implementation of a BN modifying
system/method (400).
In this embodiment the BN (total base number) modifying system/method
(400) comprises a controller (402) for creating a cylinder oil on the basis of
the tapped system oil/consumable system oil (203) by determining the BN of
the tapped oil (203), determining a desired BN of the cylinder oil (302) and
adjusting the BN of the tapped oil (203) accordingly by blending the tapped
oil (203) with at least one BN modifying additive (401) resulting in a
cylinder
oil (302'), where said cylinder oil (302') is supplied to cylinders or part of
the
cylinders of said engine (300).
In this way, a method and system for converting/re-cycling a (used/spent)
system oil/consumable system oil into a useable cylinder oil by adjusting BN
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is provided. This results in significant economical benefits since system
oil/consumable system oil that otherwise ultimately would have to be
disposed-of can be re-used/re-cycled as a total-loss cylinder lubricant. In
addition, a more cost-effective consumable system oil can be used.
Furthermore, cylinder oil does not have to be purchased. The system
oil/consumable system oil used to blend the cylinder oil is of more consistent
quality as it is replenished (contrary to the traditional practice) which
reduces
machinery wear, etc. Thus, the replenishment of the initial fluid(s) provides
enhanced and consistent performance of the initial fluids resulting in greatly
reduced component wear and equipment lifecycle cost. Even further, a more
environmentally friendly method/system is provided since waste, in the form
of spent oil(s) that is discarded after prolonged use, is reduced as it is
converted into cylinder oil.
The BN modifying additive may e.g. comprise at least one base. Preferably
the at least one base comprises basic salts of alkaline or earth alkaline
elements, and/or detergents and/or dispersants. The cylinder oil may be
created with a BN in response to fuel oil characteristics and/or actual engine
operating requirements. Further the BN of the cylinder oil may be chosen
based upon sulphur-content of the used system oil. The used system
oil/consumable system oil may e.g. be selected from a group of lubricants,
hydraulic fluids, gear oils, system oils, trunk piston engine oils, turbine
oils,
heavy duty diesel oils, compressor oils, etc.
The alkaline/earth alkaline elements may e.g. be K, Na, Ca, Ba, Mg or the
like. The basic salts may belong to the inorganic chemical families of e.g.
oxides, hydroxides, carbonates, sulphates or the like. The detergents may
belong to the organic chemical families of e.g. sulphonates, salicylates,
phenates, sulfophenates, Mannich-bases and the like. The dispersants may
belong to the organic chemical families of succinimides or the like.
Alternatively, the conversion of spent/used system oil/consumable system oil
into cylinder oil may be done without replenishing, i.e. the BN modifying
system (400) is connected directly into the engine or is connected to a
tapping system without replenishment.
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Figures 2a and 2b illustrate the effects of the present invention during a
test.
Shown in Figure 2a is a graph (210) illustrating the mechanical efficiency of
an engine before, during and after use of the present invention where system
oil/consumable system oil from the engine is modified by adding at least one
friction modifier to at least a part of the system oil. The graph is separated
into a first part (211) illustrating measurements in a period before
application
of the present invention, i.e. traditional efficiency, a second part (212)
illustrating measurements in a period during application of the present
lo invention and a third part (213) illustrating measurements in a period
after
application of the present invention.
As can be seen by the graph (210) the overall mechanical efficiency, i.e. the
rate between the effective power output from the engine seen in relation to
an indicated maximum power output from the engine, is increased by
modifying the system oil/consumable system oil by adding at least one
friction modifier according to the present invention. More specifically, it
can
be seen that the mechanical efficiency generally is higher in the second and
third part (212; 213) of the graph (210), i.e. during and after application of
the
present invention.
Shown in Figure 2b is a graph (210) illustrating the loss of power of an
engine before, during and after use of the present invention. The graph is
separated into a first part (211) illustrating measurements in a period before
application of the present invention, i.e. traditional efficiency, a second
part
(212) illustrating measurements in a period during application of the present
invention and a third part (213) illustrating measurements in a period after
application of the present invention. As can be seen by the graph (210) the
overall loss of power is generally reduced in the second and third part (212;
213) of the graph (210), i.e. during and after application of the present
invention.
In the claims, any reference signs placed between parentheses shall not be
constructed as limiting the claim. The word "comprising" does not exclude the
presence of elements or steps other than those listed in a claim. The word
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"a" or "an" preceding an element does not exclude the presence of a plurality
of such elements.
