WO2011034537A1

WO2011034537A1 - Power generating system and method of use

Info

Publication number: WO2011034537A1
Application number: PCT/US2009/057420
Authority: WO
Inventors: Richard Leahy; Klaus-Werner Damm; Keith P. Saddler; Mark Stephen Wells
Original assignee: A.P. Moller-Maersk A/S
Priority date: 2009-09-18
Filing date: 2009-09-18
Publication date: 2011-03-24

Abstract

A power generation system has an oil tank containing a universal system oil. A first lubricant recycling loop recycles used universal system oil from a crankcase section of a two-stroke engine. A blending apparatus is coupled to the first lubricant recycling loop, a cylinder oil supply loop, and a blended oil conduit. The blending apparatus blends at least one additive package with the used universal system oil producing a blended cylinder oil and a blended trunk piston engine oil. The cylinder oil supply loop connects the blending apparatus with a cylinder section of the two-stroke crosshead engine to direct the blended cylinder oil to the cylinder section of the two-stroke crosshead engine. The blended oil conduit connects the blending apparatus with a four-stroke trunk piston engine and directs the blended trunk piston engine oil to an oil pan of the four-stroke trunk piston engine.

Description

TITLE OF THE INVENTION

[0001] POWER GENERATING SYSTEM AND METHOD OF USE

BACKGROUND OF THE INVENTION

[0002] The present invention generally relates to a power generating system and method of use, and more particularly, to power generating system having a two-stroke crosshead diesel engine and at least one four-stroke trunk piston diesel engine.

[0003] Diesel engines are generally classified as slow-speed, medium-speed or highspeed engines, with the slow-speed engines typically being used for the largest, deep draft marine vessels and in certain land based industrial applications. Slow speed diesel engines are typically direct coupled, direct reversing, two-stroke crosshead engines operating in the range of about 55 to 250 rpm. Two-stroke crosshead diesel engines have long been favored in the main propulsive power unit for most types of merchant marine vessels. As the price of oil rose over the years, developments in the design of two-stroke crosshead engines permitted the use of cheaper residual fuels. Use of residual fuels combined with major improvements in turbocharger design and waste heat recovery, raised the efficiency of two-stroke crosshead and power output allowing the two-stroke crosshead diesel engine to supersede the steam turbine plants which operated at much lower efficiencies.

[0004] Medium-speed engines typically operate in the range of 250 to about 1 100 rpm and may operate on the four or two-stroke cycle. Such engines are trunk piston design and may also operate on residual fuels. Four-stroke trunk piston diesel engines can be found on most medium to large merchant marine vessels even if the main engine is either a steam turbine or a two-stroke crosshead engine. On deep-see vessels, one or more two-stroke trunk piston engines may be used for propulsion, ancillary applications or both.

[0005] Each type of diesel engine employs lubricating oils to minimize component wear, remove heat, neutralize and disperse combustion products, prevent rust and corrosion and prevent sludge formation or deposits. Multiple lubricants with different formulations are required because no single lubricant formulation has been able to provide optimum protection against all of the various deleterious conditions and various fuel types to which an engine may be exposed.

[0006] Power generating systems, such as described in U.S. Patent No. 7,316,992, have been developed to add an additive to used system oil to create a blended cylinder oil that minimizes or neutralizes the acid level of the cylinder system and prolongs the life of the system oil. [0007] However, there remains a need to replenish the trunk piston engine oil in an efficient and effective manner.

BRIEF SUMMARY OF THE INVENTION

[0008] In one embodiment there is a system for generating power having an oil tank containing a universal system oil, a two-stroke crosshead engine having a crankcase section, a cylinder section and a first lubricant recycling loop coupled to the two-stroke crosshead engine and the oil tank, the first lubricant recycling loop configured to recycle used universal system oil through the crankcase section, a blending apparatus coupled to: the first lubricant recycling loop; a cylinder oil supply loop; and a blended oil conduit, the blending apparatus configured to blend at least one additive package with the used universal system oil to produce a blended cylinder oil and a blended trunk piston engine oil, the cylinder oil supply loop being further coupled to the cylinder section of the two-stroke crosshead engine and the blending apparatus and configured to provide the blended cylinder oil to the cylinder section of the two-stroke crosshead engine, and a four-stroke trunk piston engine having an oil pan coupled to the blended oil conduit, the blended oil conduit configured to provide the blended trunk piston engine oil to the oil pan of the four-stroke trunk piston engine.

[0009] In another embodiment, the invention is directed to a method of operating a power generating system comprising a two-stroke crosshead engine having a crankcase section and a cylinder section and a four-stroke trunk piston engine having an oil pan, the method including the steps of: providing a universal system oil to the crankcase section of the two- stroke crosshead engine; withdrawing used universal system oil from the crankcase section of the two-stroke crosshead engine; creating a blended cylinder oil by mixing the used universal system oil with a first additive; creating a blended trunk piston engine oil by mixing the used universal system oil with a second additive; supplying the blended cylinder oil to the cylinder section of two-stroke crosshead engine; and supplying the blended trunk piston engine oil to the oil pan of the four-stroke trunk piston engine.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] The foregoing summary, as well as the following detailed description of various embodiments, will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0011] In the drawings:

[0012] Fig. 1 is a schematic block diagram of a power generating system in accordance with a first exemplary embodiment of the present invention; and [0013] Fig. 2 is a schematic block diagram of a power generating system in accordance with a second exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring to the drawings in detail, wherein like reference numerals indicate like elements throughout, there is shown in Fig. 1 a first exemplary embodiment of a power generating system, generally designated 10, in accordance with the present invention. The power generating system 10 may be used on a marine vessel (not shown) to propel and/or provide ancillary power to the vessel. However, the power generating system 10 may be used in any suitable application such as a land based industrial facility.

[0015] As illustrated in Fig. 1, the power generating system 10 includes a two-stroke crosshead diesel engine 14 and at least one four-stroke trunk piston diesel engine 16. A blending apparatus 42 is coupled between the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16 and is configured to provide a blended cylinder oil to the two-stroke crosshead diesel engine 14 by mixing a portion of used universal system oil 36 and a first additive and a blended trunk piston oil to the four-stroke trunk piston diesel engine 16 by mixing the used universal system oil 36 with a second additive. The blending apparatus 42 includes at least one mixer 44 for mixing in the first and second additives. Any suitable mixer may be used for the mixer 44. The first and second additive may be from a single additive tank 46 as described further below.

[0016] In one embodiment, the two-stroke crosshead diesel engine 14 powers a propulsion device 18 of the vessel and the four-stroke trunk piston diesel engine 16 powers an auxiliary device 20 on the vessel such as an electricity generator. However the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16 may power any suitable device or combination of devices thereof. For example, both the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16 may be used to power the propulsion device 18. The two-stroke crosshead diesel engine 14 includes a crankcase section 22, a cylinder section 24 and a combustion chamber 26. The four-stroke trunk piston diesel engine 16 includes an oil pan 28 and a combustion chamber 30.

[0017] The power generating system 10 includes an oil tank 32 that contains the universal system oil 34 that is used to replenish the system oil of the two-stroke crosshead diesel engine 14. A first recycling lubricating supply loop 40 may be coupled to a blending apparatus 42. The first lubricant recycling loop 40 is coupled to the two-stroke crosshead diesel engine 14 and the oil tank 32. The first lubricant recycling loop 40 is configured to recycle used universal system oil 36 through the crankcase section 22. Used universal system oil 36 which is withdrawn from the crankcase section 22, is then used in lubricating the cylinder section 24 of the two-stroke crosshead diesel engine 14 and also in replenishing the trunk piston engine oil in the four-stroke trunk piston diesel engine 16 as discussed further below. The used universal system oil 36 may be used as the base lubricant for all of the combustion engines on the vessel 12 and may be modified using one or more additives to, for example, meet the requirements, i.e. total base number, of the particular engine. Because the universal system oil 34, 36 in the two-stroke crosshead diesel engine 14 may be replenished, either continuously or periodically, the universal system oil 34 in the two-stroke crosshead diesel engine 14 may have a lower total base number (TBN), also referred to as a "light" system oil. The TBN value of the universal system oil 34 may range from a TBN of less than 20; a TBN of less than 5; a TBN range from 2 and 5; and a TBN range from 2 and 3. In the embodiment shown, the universal system oil 34 is directly supplied into the crankcase section 22 of the two-stroke crosshead diesel engine 14 via a fresh system oil conduit 38. However, the universal system oil 34 may be indirectly supplied to the two-stroke crosshead diesel engine 14 such as through the first recycling lubricating supply loop 40.

[0018] The universal system oil 34 may include a natural or synthetic oil or mixture thereof. Natural oils include mineral oils, vegetable oils, solvent treated mineral oils and the like. Synthetic oils include polyalpha olefins, polyol esters, poly internal olefins, polyethylenes, propylenes, polybutenes, polyethyleneglycols, polypropyleneglycols, polyalkyleneglycols, their mixtures and the like, other functional fluids, such as alkylated aromatics, perfluoroalkylpolyethers, polyphenyl ethers, cycloaliphatics, phosphate esters, dialkyl carbonates, silicones, silahydrocarbons, phosphazenes, etc. In general the viscosity of the base oil blend of the primary lubricant herein is in the range of about 5 to about 30 cSt at 100 degrees C.

[0019] As illustrated in Fig. 1, an additive tank 46, containing at least one additive, is coupled to the blending apparatus 42. In one embodiment, the first and second additives are identical in composition, i.e. come from a single additive tank 46, but differ in volume or differ in the ratio of amount of additive as compared to amount of used universal system oil 36 with which the additive is mixed. In one embodiment, the mixer 44 may adjust the ratio of the used universal system oil 36 and additive for each of the blended cylinder oil and blended trunk piston engine oil. Any remaining used universal system oil 36 may be returned to the crankcase section 22 of the two-stroke crosshead diesel engine 14 via the first recycling lubricant supply loop 40. [0020] Though use of a single additive tank 46 is shown in Fig. 1, separate additive packages from two or more tanks (see Fig. 2) may be used to create the blended cylinder oil and the blended trunk piston engine oil as described below. In one embodiment, the additive includes a base fluid to raise and control the TBN of the blended cylinder oil and the blended trunk piston engine oil based on the sulfur content of first and second fuels 48, 50 used in the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16, respectively. The additive may be used with the used system oil 36 at a weight ratio ranging from 90: 10 to 10:90 additive to used system oil 36. In one embodiment, the blended cylinder oil and the blended trunk piston engine oil are substantially identical in composition.

Alternatively, the blended cylinder oil and the blended trunk piston engine oil may have different compositions based on different additives and/or ratios of additive to used system oil 36. The additive may contain one or more additives or additive packages such as, but not limited to, basic salts of alkaline or earth alkaline elements, detergents, dispersants, antioxidants and or friction modifiers. The alkaline/earth alkaline elements may be for example, K, Na, Ca, Ba, Mg or the like. The basic salts may belong to the inorganic chemical families for example oxides, hydroxides, carbonates, sulfates or the like. The detergents may belong to the organic chemical families of for example sulfonates, salicylates, phenates,

sulfophenates, Mannich-bases and the like. The dispersants may belong to the organic chemical families of succinimides or the like. The additive additional may include a mixture of at least two of a calcium phenate, a calcium sulphonate and a calcium salicylate for particular use in the blended trunk piston engine oil.

[0021] The blended cylinder oil may be supplied to the cylinder section 24 of the two- stroke crosshead diesel engine 14 via a cylinder oil supply loop 68. U.S. Patent No.

7,316,992 discloses a system for modifying a used system oil to create a blended cylinder oil and is hereby incorporated by reference in its entirety.

[0022] In one embodiment, the TBN of the blended cylinder oil and the blended trunk piston engine oil is adjusted or controlled based on one or more parameters of the actual engine operating requirements and/or parameters of the first and second fuels 48, 50 used to fuel the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16, respectively. In one such embodiment, the blended cylinder oil and the blended trunk piston engine oil each have a target TBN that is calculated by a calculating device 72 based on the sulfur levels of the first or second fuel 48, 50 measured by a measuring device 70. In one such embodiment, a controller 74 is operatively coupled to the blending apparatus 42, the measuring device 70 and the calculating device 72 and is configured to execute a machine readable programmable code to blend the used universal system oil 36 with the calculated amount of the at least one additive to thereby create at least one of the blended cylinder oil and the blended trunk piston oil each having a target total base number. For example, if the first fuel 48 is measured by the measuring device 70 to have a sulfur level of 3% weight, the target TBN is calculated by the calculating device 72 to be within the range of 40-70 and the controller 74 executes the machine readable programmable code to the blend the appropriate amount of used universal system oil 36 with the calculated amount of the additive to the meet the first target total base number. Alternatively, the desired ratio or target total base number may be manually inputted into the blending apparatus 42. U.S. Patent Application

Publication No. 2008/0153726 discloses a method for operating two and four-stroke engines using low sulfur fuels and is hereby incorporated by reference in its entirety. Though the additive or additive package may adjust the TBN of the blended cylinder oil and/or the blended trunk piston engine oil, the additive or additive package may also, or alternatively, adjust the viscosity, detergency, oxidative stability, load carrying, anti-wear, and/or dispersancy of both the blended cylinder oil and the blended trunk piston engine oil based on one or more parameters of the fuel and/or engine operating requirements.

[0023] In one embodiment, the use of a universal system oil 34 allows for prolonged operation regardless of the fuel type, such as zero sulfur biofuels, low sulfur distillate fuels, low sulfur heavy fuel, standard heavy fuel having an up to 3% by weight sulfur content, and without the need to change the universal system oil 34 that is used and may be modified for use with various sections utilizing a single additive package.

[0024] In one embodiment, the blended trunk piston oil is provided to the oil pan 28 of the four-stroke trunk piston diesel engine 16 from the blending apparatus 42 via a blended oil conduit 62 to replenish the trunk piston oil. The blended oil conduit 62 may be coupled to the four-stroke trunk piston diesel engine 16 by a second lubricant recycling loop 54. The amount of blended trunk piston oil provided to the oil pan 28 is determined by oil consumption during routine operation (amount required to top-up) of the four-stroke trunk piston diesel engine 16, by the physical and chemical properties (TBN, viscosity, Insolubles, water, wear metals) of the trunk piston oil already residing in the four-stroke trunk piston diesel engine 16, properties of the second fuel 50 being used (particularly the fuel sulfur level) and the TBN requirements for the second fuel 50. The second lubricant recycling loop 54 may include a plurality of filters 56. The separate oil container 52 may alternatively be omitted. [0025] In the embodiment shown in Fig. 1, both the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16 include waste tanks 58 that hold waste oil that is filtered out of the used universal system oil 36 and the used blended trunk piston oil. Replenishing the trunk piston engine oil with a blended trunk piston engine oil may reduce the size of the oil container 52, allows the four-stroke trunk piston engine 16 to be operated for a longer period of time, allows for a lower quality base oil to be used than the oil typically required by conventional four-stroke trunk piston engines and results in less waste oil.

[0026] In one embodiment, the exemplary system of Fig. 1 is used to perform methods to blend used universal system oil 36 with additives for use in the two-stroke crosshead diesel engine 14 and the four-stroke trunk piston diesel engine 16. In one embodiment, the universal system oil 34 is provided to the crankcase section 22 of the two-stroke crosshead engine 14. Used universal system oil 36 is withdrawn from the crankcase section 22 of the crosshead diesel engine 14 to create a blended cylinder oil by mixing the used universal system oil 36 with a first additive and blended trunk piston engine oil by mixing the used universal system oil 36 with a second additive. The blended cylinder oil is supplied to the cylinder section 24 of the two-stroke crosshead diesel engine 14 and the blended trunk piston engine oil is supplied to the oil pan 28 of the four-stroke trunk piston engine 16. In one embodiment, a single additive composition is used to create both the blended cylinder oil and the blended trunk piston engine oil.

[0027] Referring to Fig. 2, there is shown a second exemplary embodiment of the power generating system, generally designated 210. The power generating system 210 is similar to the first exemplary embodiment of the power generating system 10 except that the blending apparatus 242 of the second exemplary embodiment includes two mixers 244a and 244b and corresponding additive tanks 246a and 246b such that separate additive packages and mixers are used to create the blended cylinder oil and the blended trunk piston engine oil, respectively.

[0028] Additionally, an embodiment of the four-stroke trunk piston diesel engine 216 of Fig. 2 differs from the power generating system 10 of the first example shown in Fig. 1 in that the second example of the power generating system 210 includes a fuel blending system 260. The fuel blending system 260 takes used blended trunk piston engine oil to mix with a heavy fuel oil 264 and a third additive 266 to create a modified fuel 250. Alternatively, the blended trunk piston engine oil may be taken directly from the blended apparatus 242 for use in the fuel blending system 260. The modified fuel 250 may also be used to lubricate the entire trunk piston engine 216, such as the valve train and cylinder (not shown), as a partial- loss lubricating system. U.S. Patent Application Publication No. 2007/01 13819 discloses a system for reducing fuel consumption in a four-stroke trunk piston engine by blending used trunk piston engine oil with a heavy fuel oil and is hereby incorporated by reference in its entirety.

[0029] In one embodiment, the exemplary system of Fig. 2 is used to perform methods to blend used universal system oil 236 with additives for use in the two-stroke crosshead diesel engine 214 and the four-stroke trunk piston diesel engine 216. In one embodiment, used universal system oil 236 is withdrawn from the crankcase section 222 of the crosshead diesel engine 214 to create a blended trunk piston engine oil by mixing the used universal system oil with a second additive. The blended cylinder oil is supplied to the cylinder section 224 of the two-stroke crosshead diesel engine 214 and the blended trunk piston engine oil is supplied to the oil pan 228 of the four-stroke trunk piston engine. In one embodiment, a single additive composition is used to create both the blended cylinder oil and the blended trunk piston engine oil. Further, the four-stroke piston engine 216 may be fueled by supplying a modified fuel 250 to the combustion chambers 230 of the four-stroke engine 216. The modified fuel may be comprised of the blended trunk piston engine oil and a fuel oil 264. In one embodiment, a third additive 226 is added to the modified fuel 250 using the blending system 260.

[0030] It will be appreciated by those skilled in the art that changes could be made to the examples and various embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular examples and embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. Unless specifically set forth herein, the terms "a", "an" and "the" are not limited to one element but instead should be read as meaning "at least one".

[0031] Further, to the extent that the method does not rely on the particular order of steps set forth herein, the particular order of the steps should not be construed as limitation on the claims. The claims directed to the method of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the steps may be varied and still remain within the spirit and scope of the present invention.

Claims

CLAIMS We claim:

1. A method of operating a power generating system comprising a two-stroke crosshead engine having a crankcase section and a cylinder section and a four-stroke trunk piston engine having an oil pan, the method comprising the steps of:

providing a universal system oil to the crankcase section of the two-stroke crosshead engine;

withdrawing used universal system oil from the crankcase section of the two-stroke crosshead engine;

creating a blended cylinder oil by mixing the used universal system oil with a first additive;

creating a blended trunk piston engine oil by mixing the used universal system oil with a second additive;

supplying the blended cylinder oil to the cylinder section of two-stroke crosshead engine; and

supplying the blended trunk piston engine oil to the oil pan of the four-stroke trunk piston engine.

2. The method of claim 1 further comprising:

fueling the four-stroke trunk piston engine by supplying a modified fuel to a combustion chamber of the four-stroke engine, the modified fuel comprising the blended trunk piston engine oil and a fuel oil.

3. The method of claim 2 further comprising:

adding an additive to the modified fuel.

4. The method of claim 1, wherein the blended cylinder oil has a first target total base number met by the addition of the first additive and calculated based on a first parameter of a first fuel used to fuel the two-stroke engine.

5. The method of claim 4, wherein the first parameter is a sulfur level.

6. The method of claim I, wherein the blended trunk piston engine oil has a second target total base number met by the addition of the second additive and is calculated based on a second parameter of a second fuel used to fuel the four-stroke engine.

7. The method of claim 6, wherein the second parameter is a sulfur level.

8. The method of claim I, wherein the two and four-stroke engines are used to power a marine vessel.

9. The method of claim 8, wherein the two-stroke engine is used to power a propelling mechanism of the marine vessel and the four-stroke engine is used to generate auxiliary power on the marine vessel.

10. The method of claim 1, wherein the first additive is mixed with the used universal system oil at a first additive: used universal system oil weight ratio ranging from 90: 10 to 10:90.

1 1. The method of claim 1, wherein the second additive is mixed with the used universal system oil at a second additive: used universal system oil weight ratio ranging from 90: 10 to 10:90.

12. The method of claim 1, wherein the universal system oil has a total base number value of less than 5.

13. The method of claim 1, wherein the first additive includes a base composition to create the blended cylinder oil having a total base number greater than the total base number of the used universal system oil.

14. The method of claim 1, wherein the second additive includes a base composition to create the blended trunk piston engine oil having a total base number greater than the total base number of the used universal system oil.

15. The method of claim 1, wherein the first and second additives are identical in composition.

16. The method of claim 1, wherein the blended cylinder oil and the blended trunk piston engine oil are substantially identical in composition.

17. The method of claim 1 , wherein at least one of the first and second additives includes at least one of detergents, anti-oxidants, and friction modifiers.

18. A system for generating power, the system comprising:

an oil tank containing a universal system oil;

a two-stroke crosshead engine having a crankcase section, a cylinder section and a first lubricant recycling loop coupled to the two-stroke crosshead engine and the oil tank, the first lubricant recycling loop configured to recycle used universal system oil through the crankcase section;

a blending apparatus coupled to: the first lubricant recycling loop; a cylinder oil supply loop; and a blended oil conduit, the blending apparatus configured to blend at least one additive package with the used universal system oil to produce a blended cylinder oil and a blended trunk piston engine oil, the cylinder oil supply loop being further coupled to the cylinder section of the two-stroke crosshead engine and the blending apparatus and configured to provide the blended cylinder oil to the cylinder section of the two-stroke crosshead engine; and a four-stroke trunk piston engine having an oil pan coupled to the blended oil conduit, the blended oil conduit configured to provide the blended trunk piston engine oil to the oil pan of the four-stroke trunk piston engine.

19. The system of claim 18 further comprising:

a fuel tank coupled to the two-stroke engine and containing a fuel having a first sulfur content;

a calculating device to determine an amount of the at least one additive package to blend with the used universal system oil based on the first sulfur content of the fuel.

20. The system of claim 18 further comprising:

a measuring device to determine the first sulfur content of the fuel;

a controller operatively coupled to the blending apparatus, the measuring device and the calculating device and configured to execute a machine readable programmable code to blend the used universal system oil with the calculated amount of the at least one additive package to thereby create the blended cylinder oil having a target total base number.

21. The system of claim 18 further comprising:

a fuel tank coupled to the four-stroke engine and containing a fuel having a second sulfur content; and

a calculating device to determine an amount of the at least one additive package to blend with the used universal system oil based on the second sulfur content of the fuel.

22. The system of claim 21 further comprising:

a measuring device to determine the second sulfur content of the fuel;

a controller operatively coupled to the blending apparatus, the measuring device and the calculating device and configured to execute a machine readable programmable code to blend the used universal system oil with the calculated amount of the at least one additive package to thereby create the blended trunk piston oil having a target total base number.

23. The system of claim 18 further comprising:

a fuel blending system coupled to the combustion chamber of the four-stroke crosshead engine and the blending apparatus to provide at least a portion of the blended trunk piston engine oil to the combustion chamber of the four-stroke trunk piston engine.

24. The system of claim 18, wherein the universal system oil has a total base number of less than 5.

25. The system of claim 18 further comprising:

a second lubricant recycling loop coupled between the blended oil conduit and the oil pan of the four-stroke trunk piston engine, the second lubricant recycling loop configured to recycle used blended trunk piston engine oil through the oil pan of the four-stroke trunk piston engine..