Lubrication System - IC Engine - Unit-III

IC Engine, Lubrication System

1. Engine Lubrication System 1 Dr. S. VIJAYA BHASKAR PROFESSOR IN MECH ENGG Sreenidhi Institute of Science and Technology Yamnampet , Ghatkesar , Hyderabad, Telangana 501301

2. Purpose o f L ubr i c a ti o n S y s t em Lubrication Reduces Friction by creating a thin film (Clearance) between moving parts Sealing The oil helps form a seal between piston rings and cylinder walls ( Reduces Blow-By) Internal oil leak (blow- by) will result in BLUE SMOKE at the tail pipe.

3. Purpose o f L ubr i c a ti o n S y s t em Cleaning As it circulates through the engine, the oil picks up metal particles and carbon, and brings them back down to the pan. Cooling Picks up heat when moving through the engine and then drops into the cooler oil pan, giving up some of this heat. Reduction of Noise Lubrication reduces the noise of the engine.

4. Purpose o f L ubr i c a ti o n S y s t em • Absorbs shock When heavy loads are imposed on the bearings, the oil helps to cushion the load. • Absorbs Contaminants The additives in oil helps in absorbing the contaminants that enter the lubrication system.

5. Lubrication Systems Mist lubrication system Wet sump lubrication system Dr y sum p lubrication system Fou r Stroke Engines 5 Two Stroke Engines Mist lubrication system is mainly employe d in two- stroke cycl e engines , whereas wet an d dr y sump systems ar e use d in four-stroke cycl e engines . The wet sum p syste m is employe d in relatively small engines , such a s automobil e engines , while the dr y sum p syste m is use d in large stationary, marine an d aircraf t engines.

6. Crankcase 6 The bottom of the Cylinder block is called Crankcase A cover fasted to crankcase acts as a sump to collect and circulate the lubricate oil It is a cylindrical vessel or space in which the piston makes a reciprocating motion. The cylinder is supported in the cylinder block The volume created in the cylinder varies based on the operations occurs to different thermodynamic processes. Cylinder

7. I n two-strok e engines , th e charg e is compresse d i n th e crankcase , an d a s suc h i t is no t suitabl e t o hav e th e lubricating oi l in the sump. P e t r o i l o r Mi s t l ub r i c a ti o n s y s t em The lubrication oil is mixed with the fuel, the usual ratio being 3% to 6%. Oil and fuel mixture is inducted through the carburetor.

8. Fuel is vaporized and the oil in the form of mist (film/fog) goes via the crankcase into the cylinder. The oil which strikes the crankcase walls lubricates the main and connecting rod bearings and the rest of oil lubricate the piston, piston rings and the cylinder . P e t r o i l o r Mi s t l ub r i c a ti o n s y s t em

9. Advantage: Simplicity and Low cost as it does not require an oil pump, filter, etc. Disadvantages: Cause heavy exhaust smoke due to burning of lubricating oil Forms deposit on piston crown and exhaust port which affect engine efficiency. Requires a thorough mixing for effective lubrication. This requires either separate mixing prior to use or use of some additive to give the oil good mixing characteristics.

10. 10 We t Sum p Lubricatio n Systems I n th e we t sum p system , th e botto m o f the crankcas e contain s a n oi l sum p (o r pan ) that serve s a s the oi l suppl y reservoir . Oi l dripping fro m th e cylinder s an d bearing s flow s by gravit y bac k into the wet sum p where it is picke d u p b y a pum p an d re-circulated throug h th e engin e lubricatin g system . The types o f wet sum p system s use d are: th e splas h lubrication system th e splas h an d pressure system th e pressure fee d system

11. Lubri c a tion S yst e m – W e t Sump

12. Lubri c a tion S yst e m – W e t Sump Oil is stored in the sump. Drawn into engine through the pickup. Forced round by a pump. Protected by a pressure relief valve. Particulates removed by a filter. Carried around in galleries.

13. Sp lash S y s t em Used in light duty, slow speed engines (<250 rpm). Lubricating oil is stored at the bottom of engine crankcase and maintained at a predetermined level . The oil is drawn by the pump and delivered through a distributing pipe into the splash trough located under the big end of all the connecting rods. These troughs are provided with overflows and oil in the trough is therefore kept at a constant level.

14. 14 Splas h an d Circulating Pum p System C a m s h a f t M a i n b e a r i n g C o n n e c t i n g r o d b e a r i n g s m a i n b e a r i n g O i l t r o u g h s L o w e r o il p a n O i l p u m p O i l S t r a i n e r

15. Sp lash S y s t em A splasher or dipper is provided under each connecting rod cap which dips into the oil in the trough at every revolution of the crankshaft and the oil is splashed all over the interior of crankcase, into the pistons and onto the exposed portion of cylinder walls . The oil dripping from the cylinder is collected in the sump where it is cooled by the air flowing around. The cooled oil is then recirculated

16. Splash Lubrication System

17. This system is shown in Fig.2, where the lubricating oil is supplied under pressure to main and camshaft bearings. Oil is also supplied under pressure to pipes which direct a stream of oil against the dippers on the big end of connecting rod bearing cup and thus the crankpin bearings are lubricated by the splash or spray of oil thrown up by the dipper. Splash and Pressure Lubrication System

18. 18 Splas h an d Pressur e System C a m s h a f t C onne c t i n g r o d b e a r i ng s M a i n b e a r i n g m a i n b e a r i n g O i l p u m p O i l S t r a i n e r

19. Splash and Pressure Lub Sys…

20. Pressure feed system is illustrated in Fig 3 in which oil is drawn in from the sump and forced to all the main bearings of the crankshaft through distributing channels . A pressure relief valve will also be fitted near the delivery point of the pump -which opens when the pressure in the system attains a predetermined value. An oil hole is drilled in the crankshaft from the centre of each crankpin to the centre of an adjacent main journal, through which oil can pass from the main bearings to the crankpin bearing. From the crankpin it reaches piston pin bearing through a hole drilled in the connecting rod. The cylinder walls, piston and piston rings are lubricated by oil spray from around the piston pins and the main and connecting rod bearings. Pressure Feed System

21. 21 Ful l Forc e Fee d System C a m s h a f t M a i n b e a r i n g H eade r m a i n li n e bea r i n g E n d l e akage fr o m r o d c o nne c t i n g r o d bea r i ng O i l pu m p O i l S t r a i ner

22. P r essu r e F eed S y s t em

23. Pressure Feed Lubrication System

24. D r y Sump It uses an additional pump as well as a remote oil tank It is used in situations when a wet sump cannot cope with the oil supply, in unusual or extreme conditions; Heavy acceleration (racing cars), Off road driving, steep hills and uneven surfaces

25. In dry sump lubricating system, the supply of oil is carried in an external tank An oil pump draws oil from the supply tank and circulates it under pressure to the various bearings of the engine Oil dripping from the cylinders and bearings into the sump is removed by a scavenging pump which in turn the oil is passed through a filter, is fed back to the supply tank. Thus, oil is prevented from accumulating in the base of the engine. Dry Sump Lubricating System

26. The capacity of the scavenging pump is always greater than the oil pump. In this system a filter with a bypass valve placed in between the scavenge pump and the supply tank. If the filter clogged, the pressure relief valve opens permitting oil to by-pass the filter and reaches the supply tank. dry sump lubricating system

27. Dry Sump Lub Sys…

28. 22 Lubr i c a ti n g S y s t em P arts O i l s u mp O i l p u mp P i c k -u p sc r een P r ess u r e r egu l at or O i l f i l t er B y-pas s v al v e O i l g al l er i es D i p s tick P r essu r e i n di cat or

29. Properties o f Lubricating Oil The duties of the lubricant in an engine are many and varied in scope. The lubricant is called upon to limit and control the following: ( i ) friction between the components and metal to metal contact (ii) overheating of the components (iii) wear of the components (iv) corrosion (v) deposits 30

30. Properties o f Lubricating Oil The Lub oi l use d in a n engin e must serve as a lubricant, a coolant and an agent for removing impurities. It must be able to withstand high temperatures without breaking down . The oil must operate over a good range of temperature. They must not oxidize o n the chamber walls, pisto n crow n o r a t the pisto n rings. 31 Oil should have high film strength to prevent metal-to-metal contact even under extreme loads.

31. 32 Properties o f Lubricating Oil Viscosity : Th e lubricatin g oil shoul d hav e the correc t viscosity s o tha t i t flow s easil y t o al l the movin g parts at ALL OPERATING TEMPERATURES. I f oi l viscosit y i s to o high , more wor k i s require d t o pum p i t and to shea r it betwee n the moving parts . Thi s result s i n greater frictio n work , redu ced brake work an d henc e reduced power output. Viscosit y i s highly dependant on temperature, increasing with decreasing temperature

32. Ratin g o f Lubricating Oil 33 Lubricating oi l is generally rated using a viscosity scale establishe d b y the SAE. Commonly use d viscosit y grade s are: The oi l with lower viscosity grade s is less viscous an d is used in cold-weathe r operation. Modern high temperature, high speed, clos e tolerance engine s us e hig h viscosit y grade s oil. SAE 5 SAE 10 SAE 20 SAE 30 SAE 40 SAE 45 SAE 50

33. 13 Ratin g o f Lubricating Oil Whe n certai n polymer s ar e adde d t o oil , the temperatur e dependenc y o f oi l viscosit y i s reduced. Thes e oil s hav e low viscosit y grade s whe n the y are col d an d highe r a s they becom e hot. As fo r example , SA E 10W-30 mean s tha t th e oi l ha s a grad e 10 whe n i t i s col d ( W stand s fo r winter) an d 3 when it is hot . Commonly use d oil s i n thi s categor y are: SAE 5W-20 SAE 10W-40 SAE 5W-30 SAE 10W-50 SAE 5W-40 SAE 15W-40 SAE 5W-50 SAE 15W-50 SAE 10W-30 SAE 20W-50

34. Flash Point and Fire Point The flash point of an oil is the minimum temperature at which sufficient flammable vapour is driven off to flash when brought into contact with flame. The fire point is the minimum temperature at which the inflammabl vapours will continue to form and steadily burn once ignited. Flash and fire points may vary with the nature of the original crude oil, the viscosity and the method of refining. Lub oils have higher flash and fire points than fuel. Properties of Lub Oil

35. Oiliness or Film Strength Film strength refers to the ability of the lubricant to resist welding and scuffing . The lubricating oil used must be of enough film strength to take care of welding and scuffing. Corrosiveness The oil should be noncorrosive and should protect against corrosion. It is probable that the absorbed film that rise to the level of oiliness is also related to the protection of the surface against corrosion. Properties of Lub Oil

36. Detergency An oil has the property of detergency if it acts to clean the engine deposits. A separate property is the dispersing ability which enables the oil to carry small particles uniformly distributed without agglomeration. In general, the term is the name for both detergent and dispersing properties. Properties of Lub Oil

37. Properties o f Lubricating Oil Specific Gravity: This propert y is o f little importance except as an indicator of weight an d volume. The specific gravit y o f oi l varies from 0.85 to 0.96 ( ratio of the density of a fluid to the density of a standard fluid) Pour Point: It indicates the temperature below which the lubricating oil loses its fluidity an d will not flow o r circulate in the system. This characteristics of the oil is important at low temperature Pour point must be at least 1 5 F lower than the operating temperature to ensur e maximum circulation. 38

38. Ratin g o f Lubricating Oil Oxidation Stability: Oxidation stability of an oi l is its resistance to oxidation. Du e to oxidation , oi l forms deposit s o n the pisto n rings, an d thereby loses its lubricating property. Som e inhibitors ar e use d to counterac t these tendencies. Acidity an d Neutralization Number: The acidity. The lubricating oil should have low neutralizatio n numbe r is a measure o f acidi c or alkaline contents of oil . 39

39. Types o f Lubricating Oil  Vegetabl e oils have bee n used in the past, especially for racing car engines. The main advantage s o f these oils ar e their high film strength, an d they have a good lubricity. 40  Later, specially formulated mineral in oils high hav e replaced their use performanc e engines . Mineral oils ar e most readily available and cost effective. Th ey readily respond to additives, and can be produce d in a wide range o f viscosities. The main disadvantage lies with its wax content that affects cold performance and ca n clo g filters.

40. Classification o f Lubricants Animal Vegetable Mineral Synthetic 41

41. 42 Animal Lubricants Lubricants with anima l origin: Tallow Tallow oil Lard oil Neat’s foot oil Sperm oil Porpoise oil These ar e highl y stable at normal temperatures Animal lubricants may no t be use d for internal combustion because they produce fatty acids.

42. Vegetabl e Lubricants Examples of vegetable lubricants are: – Castor oil, Olive oil, Cottonseed oil Animal and vegetable oils have a lower coefficient of friction than most mineral oils but they rapidly wear away steel. Mineral Lubricants These lubricants are used to a large extent in the lubrication of aircraft internal combustio n engines. There ar e three classifications o f mineral lubricants: – Solid, Semisolid, Fluid 43

43. Syntheti c Lubricants Becaus e o f the high operating temperatures o f gas-turbin e engines, it became necessary to develop lubricants which would retain their characteristics at temperatures that caus e petroleu m lubricants to evaporate and break down. Synthetic lubricants do not break down easily and do not produce cok e o r othe r deposits. 44

44. Additives Corrosion an d Rus t Inhibitors Anti-foam Agents Detergent-Dispersants Pour Point Improvers Oiliness an d Film-strength Agents 45