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How engine works

We will begin our explanation of basic engine operation by looking at the four-stroke working cycle of the engine

These four strokes are usually called

1< The intake stroke 

2< The compression stroke 

3< The combustion（expansion）stroke 

4< The exhaust stroke

Piston ring sets

Piston rings form a ring pack, which usually consists of 2-5 rings, including at least one
compression ring. The number of rings in the ring pack depends on the engine type, but
usually comprises 2-4 compression rings and 0-3 oil control rings. For example, fast
speed four-stroke diesel engines have 2 or 3 compression rings and a single oil control
ring. The oil control rings used in diesel engines are two-piece assemblies and spark-
ignited engine oil control rings may be three-piece assemblies as well. In addition to the
general compression rings and oil control rings there are scraper rings, which have the
tasks of both sealing and scraping off the oil from the liner wall. Scraper rings have a
beak intended for scraping off the oil

Top Ring→This is referred to as the “upper compression ring”. The upper compression ring is the piston ring that operates under the harshest conditions with respect to thermal and mechanical loading. Its job is to form a gas-tight barrier between the piston and cylinder wall in order to seal the combustion chamber

Second Ring→This is referred to as the “lower compressing ring”. One of its jobs is to work together with the top ring in order to “seal” the combustion chamber.

Oil Ring→As its name” oil control ring” implies, this ring scrapes excess lubricating oil off the cylinder wall, maintaining proper lubrication while keeping oil consumption within proper limits.

 Main functions of piston ring

1.1    to seal off the combustion pressure,

The top ring provides a gas seal and the second ring below it assists in the sealing and adjusts the action of the oil film. This means that the combustion chamber must be made as gas-tight. As possible ,so that the pressure generated by the quickly burning combustion gases will move the piston in the cylinder causing the crankshaft. To turn, making power available. Not only important for the combustion expansion stroke, gas-tightness is also very important for the intake, compression and exhaust strokes as well. This general function can be simply called “gas sealing”

1.2  to distribute and control the oil

The piston rings require some oil for lubrication, however it is desirable to keep this amount to a minimum. The rings act in a scraping manner keeping excess oil out of the combustion chamber, in this way, oil consumption is held at an acceptable level and harmful emissions are reduced.

The oil scraped off by the oil ring flows from the drainage into the piston.

1.3  to transfer heat,

The piston rings act to carry heat away from the hot piston into the cooled cylinder wall block of the engine. Heal energy flows from the piston groove into the piston and then into the cylinder wall, where it eventually will be transfer function is very important to maintaining acceptable temperatures and stability in the piston and piston rings, so that sealing abilities not.

1.4  to stabilise the piston

Structure Of The Piston Ring

 Piston Ring Types: According to their function, it is made between compression rings and oil control rings. There are the following main groups, each having a particular application

1.) R Plain Compression Ring This is a compression ring with a rectangular cross section and with its geometrically simply from provides an adequate seal under normal operating condition.

2.) ET This is a compression ring with one side tapered   

3.) T This is a compression ring with both sides tapered and is used in those cases when ring sticking can be expected. Due to its wedge shape, any radial movement of the ring will alter its axial clearance and thus minimise the build up of combustion residues.

1.)M This compression ring has a tapered running surface which is intended to shorten its running-in period. At the start, the ring and cylinder are n line contact only but with high unit pressure. The gas pressure which also acts at the running surface of the ring provides however some slight relief .Due to their oil scraping action, these rings are often used as an aid in controlling the oil consumption of an engine.

2.)N Napier Ring This ring can be considered as a compression ring with an oil scraping property. The recess in the ring causes it to twist in a manner similar to the compression rings. The lower edge of the running surface makes contact with the cylinder

NM  Taper-face scraper ring (Stepped)

 LP   Compression rings with an L-shaped cross section commonly installed in small 2-stroke engines in order to improve control of the gas flow through the cylinder ports. Due to its resistance to flutter.

S  Slotted oil control ring  This is a slotted oil control ring with parallel sides and tow contact land. Due to the narrow lands of this type of ring, a high a unit pressure is achieved

G  Double-bevelled oil control ring Similar to the type Bevel-Edged oil Control Ring but by chamfering the edges of both lands in same direction, the oil scraping effect is even further improved

D  In order to achieve a further increase in unit pressure and thereby a better oil scraping effect the outside edge of both lands are cham-fered

SSF  Oil control ring with spiral Expander

Surface Treatments 

Surface treatment serve to improve the running-in of piston rings and within limits to inhibit corrosion. This latter feature is only relevant in the case of prolonged storage

We have developed piston rings with  36 kind of engines applications as follows:

Phosphating and Ferroxiding

These two processes ensure that running-in occurs Rapidly and without scuffing. By chemical and thermal means the surface of a ring is converted respectively to crystalline phosphates and black iron oxide

The phosphate layer wears away more easily than the base material of the ring thus achieving a more rapid running-in. The rubbed off particles of iron oxide are so hard that during the running-in process they serve as a first class abrasive. Both layers have a limited resistance to scuffing and in this respect are similar to a nitrided layer. They are therefore fitted with success to engines in which the level of scuffing is not too high.

 Peripheral Coatings

Chrome Plating 

        An electrodeposited chromium coating has excellence resistance. In addition , its good resistance without question superior to both uncoated and treated ring. The      greatest wear occurs generally at the top ring at T.D.C. This is due to the inferior running that are present.

As diesel engines have to reach an extremely long life they are usually equipped with more than or plated piston ring. Even the oil control rings use engines are chrome plated over their running surface.

 Molybdenum Coating   The best method to avoid scuffing is to inlay the Running surface or to coat if completely wit molybdenum. This can be accomplished by a flame as flame as well as a plasma spraying process.

This high resistance to scuffing of the molybdenum coating can be related to its high melting melting point .to its porosity ,and to the lubricating effectiveness of the oxidized molybdenum layer that can be formed during the breakdown of the oil film.  Resulting from metal spraying acts effectively as an oil reservoir ,and will improve lubrication under critical running conditions. The face that porosity influences the strength of a small contacting areas, e,g. oil control rings.

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Material Specifications

Piston:   K1   Standard≤Ø200mm

K2   Standard > Ø200至400mm

K3   F11    ≦Ø200mm

K4   IKA

K5   标准型> Ø400至600mm

K6   F12

K9   KV1    ≦Ø200mm

K12   IKA3

K13   KV     > Ø200mm

 Steel Piston Ring And Spring Steels

 For Piston Rings    

KS3  3X90CrMo  V18

KS5  58Cr V4

KS6  Spring Steel similar to C67

KS7  7 Oil Hardened and Tempered

      Spring steel

KS11  Spring Steel similar to X 10 Cr

       Mn Ni 177

KS12   Spring steel similar to Cf 70

KS15   Spring Steel S

Material Specification—K1—

(Grey Cast Iron, Not Heat Treated)

Material:   Standard

Application:piston rings up to 200mm nominal diameter

Chemical Composition(%):

          C: 3.6-4.0      Si: 2.4-3.0

Mn: 0.5-0.8     P:  0.4-0.6

S:  ≦0.12      Cr: ≦0.3

Cu: ≦0.3

Microstructure:

           Graphite: preferably lamellar and

Uniformly distributed.

           Matrix  : pearlite, ferrite not exceeding 5%

           Phosphide Eutectic : Preferably continuous network

Mechanical Properties:

           Hardness: HRB 96-106 210-280HB

           Bending strength:   ≧350 N/mm²

           Modulus of Elasticity:85000-115000N/mm²

Coefficient of Thermal Expanslon （10^-6mm/mm^。C）

         20--100^。C  11.1

           20--200^。C  11.4

           20--300^。C  11.6

           20--400^。C  11.9

           20--500^。C  12.2

           20--600^。C  12.5

Density:

          7．3g/cm³

^{Material Specification—K2—}

^{(Grey Cast Iron, Not Heat Treated)}

^{Material:   Standard}

^{Application: Ø200mm--- Ø400}

^{Chemical Composition(%):}

          ^{C: 3.3-3.8      Si: 2.3-2.8}

^{Mn: 0.5-0.9     P:  0.4-0.6}

^{S:  ≦0.12      Cr: ≦0.5}

^{Cu: ≦0.5}

^{Microstructure:}

           ^{Graphite: preferably lamellar and}

^{Uniformly distributed.}

           ^{Matrix  : pearlite, ferrite not exceeding 5%}

           ^{Phosphide Eutectic : Preferably continuous network}

^{Mechanical Properties:}

           ^{Hardness: HRB 94-104 200-260HB}

           ^{Bending strength:   ≧300 N/mm2}

           ^{Modulus of Elasticity:75000-105000N/mm2}

^{Coefficient of Thermal Expanslon （10-6mm/mm。C）}

         ^{20--100。C  11.1}

           ^{20--200。C  11.4}

           ^{20--300。C  11.6}

           ^{20--400。C  11.9}

           ^{20--500。C  12.2}

           ^{20--600。C  12.5}

^Density:

          ^7．35g/cm3

^{Material Specification—K3—}

^{Material: X90 Cr Mo V 18,Mat –No 1.4112}

^{Application: Steel Piston Rings}

^{Chemical Composition( %):}

            ^{C: 0.8-0.95      Si: 0.35-0.50}

^{Mn: 0.25-0.40    P:  ≦0.04}

^{S:  ≦0.04       Cr: 17.0-18.5}

^{V:  0.08-0.15    P:  ≦0.04}

^{Mo: 1.0-1.25}

^{Microstructure:}

^{Tempered martensite with uniformly}

^{Dispersed carbides.}

^{Mechanical Properties:}

^{Hardness: HRC38—44}

^{Modulus of Elasticity:≈210000 N/mm2}

^{Coefficient of Thermal Expansion:}

           ^{20--100。C  10.5}

           ^{20--200。C  11.0}

           ^{20--300。C  11.0}

           ^{20--400。C  11.5}

           ^{20--500。C  12.0}

^{Density:    7.7g/cm3}

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