Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F1/00—Cylinders; Cylinder heads 
  • F02F1/02—Cylinders; Cylinder heads  having cooling means
  • F02F1/10—Cylinders; Cylinder heads  having cooling means for liquid cooling
  • F02F1/12—Preventing corrosion of liquid-swept surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F1/00—Cylinders; Cylinder heads 
  • F02F1/02—Cylinders; Cylinder heads  having cooling means
  • F02F1/10—Cylinders; Cylinder heads  having cooling means for liquid cooling
  • F02F1/16—Cylinder liners of wet type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F3/00—Pistons 

Definitions

• the subject invention relates to a cylinder liner for a diesel engine of the type forming a combustion chamber in cooperation with a reciprocating piston, and more particularly to a diesel cylinder liner having a surface treatment designed to overcome the destructive effects of cavitation-induced erosion.
• Cavitation is a localized low-pressure zone that forms along the outer wall of a cylinder liner. It is caused by the flexing of the cylinder wall due to the high cylinder pressures experienced in diesel engine ignition. During combustion, the cylinder wall quickly expands and then returns to its original geometry. Cylinder wall expansion is more pronounced as the demand for power increases due to increased cylinder pressures.
• these additives fall into two categories: those based upon a borade or nitrite salt, and those formulated from an organic chemistry compound (carboxcylic/fatty acids).
• the former group works on the principle of reducing the surface tension of the coolant, which lowers the peak pressure reached within the bubble and provides for a "soft" implosion.
• the coolant solutions formulated from organic chemistry compounds also reduce surface tension, and in addition coat the liner's outer surface with a sacrificial layer of compounds which are continuously renewed by the chemistry make-up of the coolant.
• a cylinder liner for a liquid- cooled internal combustion engine comprises a tubular body having a generally cylindrical bore adapted for receiving a reciprocating piston and forming a portion of the chamber in which the thermal energy of a combustion process is converted into mechanical energy.
• the cylinder liner includes an upper end and a lower end.
• An outer surface generally envelopes the tubular body and extends between the upper and lower ends. At least a portion of the outer surface is adapted for direct contact with a liquid cooling medium to transfer heat energy from the liner into the liquid cooling medium.
• At least a portion of the outer surface includes a surface texture consisting essentially of blocky particles having an average size of 2-8 ⁇ m, the particles each being faceted and surrounded by a channel network.
• the surface texture is effective to create a thin, stagnant layer of liquid which effectively adheres to the outer surface of the cylinder liner.
• This thin, stagnant layer of coolant operates as an integral, renewable shield which absorbs the implosion energy from the collapsing bubbles and then is quickly healed.
• a liquid-cooled cylinder block for an internal combustion engine comprise a crank case including a coolant flow passage.
• the cylinder liner is disposed in the crank case and has a generally tubular body defining a generally cylindrical bore extending between upper and lower ends.
• the body of the cylinder liner includes an outer surface at least partially exposed to the coolant flow passage for transferring heat energy from the liner to liquid cooling medium flowing in the coolant flow passage.
• At least a portion of the outer surface which is in the coolant flow passage includes a surface texture consisting essentially of blocky particles having an average size of 2-8 ⁇ m. The particles are each faceted and surrounded by a channel network capable of creating a thin stagnant layer of liquid adherent to the outer surface of the liner.
• the bubbles resulting from cavitation will be held away from the outer surface of the cylinder liner.
• the impinging jet from imploding cavities will have a longer path to travel and will have to overcome the tenacious film formed by the stagnant fluid layer.
• the stagnant layer forms a shield to rapidly dissipate the incoming high kinetic energy by imploding bubbles.
• the novel surface texture of the subject invention provides cavitation- induced erosion protection for a wide variety of liquid cooling medium, both common and specially formulated.
• the novel surface texture is easily created with common materials and processes.
• Figure 1 is a simplified cross-sectional view of a liquid-cooled cylinder block for an internal combustion engine including a crank case and a wet cylinder liner disposed therein;
• Figure 2 is an enlarged view of the area circumscribed at 2 in Figure 1, showing, in exaggerated fashion, the formation of cavitation bubbles on the outer surface of a cylinder liner due to flexing of the wall;
• Figure 3 is a perspective view of a cylinder liner according to the subject invention.
• Figure 4 is a micrograph representative of the appearance of the novel surface texture magnified approximately 100Ox;
• Figure 5 is an enlarged, fragmentary cross-sectional view showing a portion of the cylinder liner and surface texture according to this invention, with cavitation bubbles being held at a spaced distance from the outer surface by a stagnant layer of liquid;
• Figure 6 is a perspective view of an alternative embodiment of the invention depicting a portion of the outer surface of the cylinder liner being treated with a laser beam.
• a liquid-cooled cylinder block for an internal combustion engine is generally shown at 10 in Figure 1.
• the cylinder block 10 is largely composed of a crank case 12 typically cast from iron or aluminum.
• the crank case 12 includes a head surface 14 adapted to receive a head gasket (not shown).
• a cylinder liner, generally indicated at 16, is fitted into the crank case 12 so that, when fully assembled, a reciprocating piston (not shown) can slide within a ⁇ generally cylindrical bore 18 and form a portion of the chamber in which the thermal energy of a combustion process is converted into mechanical energy.
• the cylinder liner 16 is defined by a tubular body having an upper end 22 associated with the head surface 14, and a lower end 24 which opens toward a crank shaft (not shown) rotably carried in the crank case 12.
• the cylinder liner 16 includes an outer surface 26 which is fixed at its upper and lower ends to the crank case 12. Between these fixation points, the outer surface 26 is exposed to the coolant flow passage 20 for convective heat transfer through the flowing liquid cooling medium circulated within the coolant flow passage 20.
• a surface texture 28 is formed over either the entire outer surface 26 or at least that section of the outer surface 26 which is most susceptible to cavitation-induced erosion. Quite often, the central portion of the outer surface 26 is most susceptible to cavitation-induced erosion because it undergoes the greatest displacement due to pressure fluxuations in the bore 18. In Figure 3, the entire outer surface 26 is shown covered with the surface texture 28.
• the surface texture 28 consists essentially of blocky particles having an average breadth and normal displacement of 2-8 ⁇ m.
• the crystal-like particles are each faceted and surrounded by a channel network giving the appearance, when viewed from a scanning electron microscope image enlarged 100Ox, of a tightly packed array of aggregates, where each grain has several plane surfaces and the average grain size is between 2 and 8 ⁇ m.
• the dispersion of particles is generally random, but their tight packing results in an average maximum distance of less than 8 ⁇ m between adjacent particle grains. That is, the channel network, which is formed by the valleys between adjacent clustered crystalline particles, has an average maximum width of less than 8 ⁇ m.
• the textured surface 28 is effective to intentionally create a very thin stagnant layer of liquid adherent to the outer surface 26.
• this layer of stagnant cooling liquid measures anywhere from 2-20 ⁇ m thick, depending upon the composition and viscosity of the cooling medium.
• adhesive forces strongly bind a liquid substance to a surface, especially if the liquid substance is polar in nature like water.
• surface tension effects become very pronounced. Adhesion and surface tension effects are thus leveraged by the surface texture 28 and coupled to serve as capillary action. Thus, the cavitation bubbles are held by this stagnant layer away from the outer surface 26 of the liner 16.
• the impinging jet from imploding cavities will have a longer path to travel and have to overcome the tenacious film formed by the stagnant fluid layer.
• This shielding action rapidly dissipates the incoming high kinetic energy from the imploding bubbles. If an imploding bubble breaches the stagnant layer, it is quickly healed and reconstituted within the cycle time needed to create a new cavitation bubble.
• the specific range of average particle sizes (breadth and displacement) of 2- 8 ⁇ m, coupled with their tight spacing, enables the adhesion and surface tension effects within the liquid cooling medium to couple and act as capillary action to constitute the stagnant fluid layer about the outer surface 26.
• the surface texture 28 can be formed upon the outer surface 26 of the cylinder liner 16 by any commercially available technique.
• chemical or laser etching techniques can be used to form the surface texture 28, as well as mechanical grinding, stamping, rolling or abrasive blasting techniques.
• the surface texture 28 is formed by a coating 30 composed of a material that is dissimilar to the material of the cylinder liner 16.
• the coating 30 can be a dissimilar material.
• This coating material can include manganese phosphate components which are suitably processed to act as a labyrinth which anchors the water molecules (or engine coolant) and thus promotes formation of the stagnant fluid layer.
• one manganese phosphate based coating material may include Hureaulite, commonly described as Mn5H 2 (PO 4 ) 4 -4H 2 O. Hureaulite is a somewhat rare mineral with a chemistry that replaces one of the four oxygens in the regular phosphate ion group with a hydroxide or OH group.
• Hureaulite is a somewhat rare mineral with a chemistry that replaces one of the four oxygens in the regular phosphate ion group with a hydroxide or OH group.
• the liner 16 may be subjected first to an acid pickle stage, consisting of sulfuric acid at a concentration of 12-15% by volume and a maximum temperature of 38 0 C. Other acids can also be used, as the acid pickling is but a preferred route. Furthermore, a grain refiner stage is used at concentrations in the range of 0.3-0.8 oz/gal.
• the manganese phosphate bath should have a total acid/free acid ratio of no less than 6.5 with an iron content of 0.3% maximum.
• a warm (e.g. 50-70 0 C) oil seal stage is used, preferably with a water soluble oil at 10-15% concentration by volume, to protect the cylinder liner 16 during shelf storage time.
• manganese phosphate coatings of the type herein described have been used in industiy for a long time, they have been proven to be very robust in the sense that they are reproducible.
• the manganese phosphate coating process is a very inexpensive and environment-friendly process within the context of metal finishing processes.
• Figure 6 depicts an alternative technique for producing a cylinder liner 16' whose outer surface 26' is enhanced to better withstand the attack of cavitation- induced erosion.
• restricted local re-melting/chilling of the outer surface 26' is accomplished by a laser beam 32'.
• an industrial laser 34' strikes the non-reflective outer surface 26' and thus generates a highly controllable melt/cool that, by virtue of the metallic substrate, acts as a heat sink and cools rapidly and as cast-chilled structure.
• the chilled surface results from the transformation hardening of the substrate material, and is highly scuff and fatigue resistant.
• Such re-melted/chilled metallic surfaces perform well under high hertzian stresses, which is exactly the fundamental mechanism eroding the typical cylinder liner under cavitating conditions.
• the radial depth of this chilled layer is typically between 20 and 200 ⁇ m and is created in situ on the cavitation-prone areas of the outer surface 26' of the liner 16'. It is entirely possible to modulate the laser 34' in such a way as to create treated patches 36' in lieu of an overall covering of the outer surface 26'.
• the laser 34' is of the CO 2 or ND:YAG or diode type.
• the cylinder liner 16' is affixed to a suitable, indexible jig (not shown) which has the provision to at least rotate the liner 16', and preferably also to translate the liner 16'.
• the laser 34' irradiates the outer surface 26' and generates a melt pool which quickly solidifies due the substrate action as a heat sink.
• the chilled structure results from this.
• the rotation and transitory motions produced by the jig combine to generate re-melted bands that encompass the cavitation-prone zones, either as a continuous or patterned area 36'.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)

Priority Applications (7)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

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• 2005
  • 2005-09-13 US US11/225,523 patent/US7146939B2/en not_active Expired - Lifetime
  • 2005-09-14 BR BRPI0515180A patent/BRPI0515180B1/pt not_active IP Right Cessation
  • 2005-09-14 DE DE602005020160T patent/DE602005020160D1/de not_active Expired - Lifetime
  • 2005-09-14 WO PCT/US2005/032696 patent/WO2006031866A2/en active Application Filing
  • 2005-09-14 EP EP05798666A patent/EP1794434B1/en not_active Ceased
  • 2005-09-14 MX MX2007002995A patent/MX2007002995A/es not_active Application Discontinuation
  • 2005-09-14 JP JP2007531461A patent/JP5390097B2/ja not_active Expired - Fee Related
  • 2005-09-14 KR KR1020077007578A patent/KR101195055B1/ko not_active Expired - Fee Related
  • 2005-09-14 CA CA002580188A patent/CA2580188A1/en not_active Abandoned

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