Cummins Diesel Generator Set Original Parts Sales

Cummins Diesel Generator SetOriginal Parts SalesFirst, thebasic composition of the cylinder block1. Cylinder blockThe cylinder block is the main body of thecylinder. Usually made ofaluminum alloy or cast iron. Generally, the cylinder block of multi-cylinderair-cooled diesel engine is cast in a single piece, on which manyfins are cast. The cylinderblock of water-cooled diesel engine is integrally cast.As shown in Figure 1, it is an in-linecylinder block, and as shown, it is a W12 cylinder block.The upper part of the cylinder blockis provided with a cylinder head and a cylinder gasket, and thelower part is a crankcase with a bearing seat and a cover forinstalling a crankshaft, and an oil basin is fixed at the lowerpart of the crankcase. Thefront end of the engine body is the timing gear chamber, the rearend is the flywheel housing, and the left side is the valvechamber. Inside the cylinderblock is a cylinder with a valve seat on its side and a waterjacket around it.The cylinderarrangement forms of multi-cylinder diesel engines are single-rowvertical, V-shaped, single-row horizontal and horizontallyopposed. Water-cooled dieselengines with less than six cylinders are mostly in-line, as shownin Figure 3. Because thevertical type is not conducive to air-cooled heat dissipation,air-cooled diesel engines with more than two cylinders are mostlyarranged horizontally and in V form, as shown in Figure4.The engine block is the mainsupporting structure for fixing all other engine parts.The cylinder block is a large castiron or aluminum casting. Thereare two main parts: cylinder block part and crankcasepart.Take the cylinder block ofan 8-cylinder engine as an example. The function of the cylinder body is to make thepiston move up and down in the working process, and its surface ismachined to reduce the wear and friction of thepiston.Crankcase part is usedto carry crankshaft, oil pump, oil pan and oil. The coolant channel is embedded in the cylinderbody. These channels, alsoknown as water jackets, surround the cylinder. The coolant channel circulates the coolant aroundthe cylinder, thus keeping the engine cool. Some cylinders also have holes for coolingcamshafts. Many oil holes arealso drilled in the cylinder body to ensure that the engine partsare fully lubricated. Someother holes are drilled in the cylinder block to fix otherparts.2.CylinderThe cylinder is acylindrical hollow cylinder. Its function is to contain the combustible mixtureentering the engine and guide the piston to make reciprocatinglinear motion. In a two-strokegasoline engine, there are also air intake holes, gas exchangeholes and exhaust holes on the cylinder. The work of the cylinder is very heavy, and theworking conditions are as follows:(1) It is in direct contact with combustion gasand works under high temperature and high pressure: at the sametime, it is chemically corroded by high temperaturegas.(2) In the process ofworking, it constantly rubs against the piston, and the lubricationcondition is not good, and the mechanical wear islarge.(3) The cylinder needs todissipate heat in time, so there is a great temperature differencebetween the inner and outer layers and the upper and lower ends ofthe cylinder, resulting in thermal stress, especially watercooling.Therefore, the cylindermaterial must have sufficient strength, corrosion resistance andwear resistance. Ordinarycylinders are mostly cast iron, and cylinders of high-speed dieselengines are often cast with alloy cast iron. In order to improve the wear resistance ofcylinder, porous chromium plating is generally carried out on thesurface of cylinder. Inaddition to wear resistance and corrosion resistance, chromium canalso form many pores on the surface, which can store somelubricating oil and form an oil film to improve lubrication andreduce engine wear. In order toimprove the tightness of the cylinder, the machining of thecylinder wall surface must have high precision andsmoothness.3. CylinderlinerSome engines use cylinderliners. The cylinder liner isnot directly cast in the cylinder body, but embedded in a machinedbushing. After machining, thecylinder block is inserted into the bushing. The purpose of cylinder liner is that if thecylinder is damaged, it can be easily disassembled andupdated. Cylinder block withoutcylinder liner must be bored to repair the damaged part.After boring the cylinder, it isnecessary to use an enlarged piston formatching.(1) Classification ofcylinder linerThe shape ofcylinder varies with the type and working conditions of dieselengine. Some are cast togetherwith the cylinder and processed, and some are made into bushings(cylinder liners) first, and then pressed into the cylinderbody. The cylinder liner is indirect contact with cooling water after being pressed into thecylinder block, which is called wet cylinder liner as shown inFigure 5(a). A cylinder linerthat is not in direct contact with cooling water is called a drycylinder liner as shown in Figure 5(b). The former has a good cooling effect, but when thecylinder liner and cylinder block are poorly sealed, water willleak into the crankcase. Forthe cylinder with cylinder liner, the cylinder liner can be made ofhigh-quality materials, while the cylinder body can be made ofgeneral materials, which can improve the quality of the enginecylinder and reduce the cost. At the same time, the cylinder liner is easy todisassemble and repair.(2)Insertion of cylinder linerWetcylinder liner and dry cylinder liner are both pressed into thehole of cylinder block. Becausethe cylinder liner is supported on the cast iron cylinder from topto bottom, it can be machined very thin.The wet cylinder liner is also pressed into thecylinder block. The coolanttouches the middle of the cylinder liner, which is why it is calleda wet cylinder liner, as shown in Figure 6. Because it is only supported at the upper andlower parts, it must be made thicker than the dry cylinderliner. The top and bottom ofthe wet cylinder liner must be sealed to prevent water from seepingout of the cooling system. Wetcylinder liners are used in some large dieselengines.4. CylinderheadThe cylinder head, alsoknown as the cylinder head, is installed at the upper part of thecylinder block and fastened to the cylinder block withbolts. Its function is to forma combustion chamber together with the cylinder and pistontop. A cooling fin is cast onthe cylinder cover of an air-cooled diesel engine, and a waterjacket is arranged on the cylinder cover of a water-cooled dieselengine, which is communicated with a water jacket hole in thecylinder body. Gasoline engineshave spark plug holes in the cylinder head. There are injector holes on the cylinder head ofdiesel engine. The cylinderhead of overhead valve mechanism of four-stroke diesel engine isalso cast with intake and exhaust valve seat, intake and exhaustvalve rod guide hole and intake and exhaustpassage.The work task of thecylinder head is also very heavy. The bottom of the cylinder headis in contact with gas and bears high temperature and pressure.Because of the large temperature difference between the inside andoutside of the cylinder head and the complex shape, uneven thermalstress is easy to occur. At thesame time, it also bears the mechanical stress caused by fasteningbolts. Therefore, the cylinderhead is required to have sufficient strength and rigidity, and thecontact surface with the cylinder should besmooth.The cylinder head ismade of cast iron and aluminum alloy. Diesel engines generally usecast iron cylinder heads. Somegasoline engines use aluminum alloy cylinder heads.The cast iron cylinder head has highmechanical strength, good castability and heat resistance.Aluminum alloy cylinder head has goodthermal conductivity, which is beneficial to improve compressionratio, but its stiffness is poor and it is easy to deform.The single cast cylinder head isconvenient to install and repair, and it is easy to dissipate heatif it is air-cooled. Water-cooled type increases the outlet branch, butit is more complicated in manufacture and installation than theformer.When disassembling thecylinder head, we must pay attention to the symmetrical torque fromthe middle to the periphery, and gradually loosen or tighten thebolts to prevent damage to the cylinder head and air and waterleakage.5. cylindergasketWhen the combustiblemixture expands in the combustion chamber, it will produce high gaspressure, and there is a water jacket between the water-cooledcylinder head and the cylinder block. In order to prevent airleakage and water leakage, a cylinder gasket must be installedbetween the cylinder head and the cylinder block.Cylinder gasket should have sufficientstrength, heat resistance, corrosion resistance, good sealing, easydisassembly and long service life.At present, the commonly used cylinder gasket ismade of copper wallet wrapped with asbestos, as shown in Figure7. Around each hole in cylindergasket, there are burrs with large thickness to increase thereliability of sealing. Thereare also gaskets made of copper or aluminum alloy;This kind of gasket has small strengthand plastic deformation when pressed, which can improve the sealingeffect, but it cannot be used many times. Some air-cooled diesel generators with high enginetemperature also use this gasket, because the gasket has goodthermal conductivity, which can make the temperature differencebetween the cylinder head and the cylinder block smaller and isbeneficial to the heat dissipation of the cylinder head.In recent years, some engines began touse special sealant, which completely changed the traditionalcylinder gasket structure.6.Oil basinThe oil pan is alsocalled crankcase and oil pan, and its installation position isshown in Figure 8. Its mainfunction is to collect and store lubricating oil for lubricationsystem. At the same time, it isused to seal the lower part of the cylinder block and form acrankcase with it.The oil panof diesel engine is mostly made of cast iron. The oil pan containsengine oil, and an oil gauge is set beside it to measure the oillevel. There are two scribedlines on the oil gauge. The upper one indicates the high positionof the oil level. If the oil level is too high, it will increasethe oil consumption. The lower one indicates the low position ofthe oil level. If it is lower than the current line, oil should beadded. The lower part of theoil basin is provided with an oil drain plug for dischargingdeteriorated oil and dirt. Someoil drain plugs are magnetic and can absorb iron and abrasiveparticles in engine oil.The oilbasin is fixed on the cylinder block by bolts. In order to preventthe oil in the basin from leaking out, paper or cork gaskets areinstalled on the joint surface.Second, the cylinder block processingparts1. Processing of cylinderblockThe engine number isusually on the outer surface of the engine cylinder block, and thecylinder block has a small plane, which is generally a rectangularshape. This is where the engine number is located, as shown inFigure 9. When processing, wemust be careful not to destroy or smooth the numbers on it, so asnot to affect the method of verifying the authenticity of theproducts in the later stage.Thestep of making a cylinder block is to design a model, and then makea sand core with sand around the model. After the model is dismantled, the sand core isleft in the hole of the model. These sand cores will eventually become coolantchannels and cylinders. Pourmolten metal into holes made of sand. After the metal cools, remove the sand, break thesand core and take it out. Thisstructure is called a cast cylinder block. The metal used is usually gray cast iron withseveral special metals added. The added metal increases the strength and wearresistance of the cylinder block. The remaining metal also helps to reduce shrinkageand warpage caused by heat generated bycombustion.After casting, thecylinder block should be cooled and hardened, and its surfaceshould be machined so that other parts can be installed on thecylinder block. These surfacesinclude cylinder, upper plane (table) of cylinder block, camshaftseat hole, crankshaft shaft hole, and oil pan surface.The front and rear end faces of thecylinder block and the support of the engine should also bemachined, so that the parts can be fixed and sealed correctly, asshown in Figure 10.Some smallengines can also be die-cast. It is to press liquid metal into a metal moldinstead of pouring it into the sand core. The surface of this casting is smoother and theshape is more jingque. Themachining amount of this cylinder block is alsoless.2. Core holeplugAll cast iron cylindershave core hole plugs (aluminum cylinders have no core hole plugs),which are also called freeze protection plugs or expansionplugs. Sand core is used in theprocessing of cylinder block. When hot metal is poured into the sand mold, thesesand cores are partially destroyed and melted. However, some holes must be left in the cylinderbody so that the sand in the internal hole can be taken out.These holes are called coreholes. After the core hole ismachined, plug the core hole into it.The core plug is made of soft metal.In some cases, the core hole plug canalso prevent cracks in the cylinder block. For example, if there is not enough antifreeze inthe cooling liquid in winter, the cooling liquid may freeze, andthe liquid will expand when it freezes, which may lead to therupture of the cylinder block. However, if the expansion occurs near the coreplug, the core plug will pop up, so the cylinder block can beprotected from expansion and cracking.3. Comparison between aluminum cylinder block andcast iron cylinder blockThecylinder block can be made of cast iron or aluminum.In the past, most cylinder blocks weremade of cast iron. Cast ironimproves strength and can adjust the deformation caused byheating. However, with theincreasing demand for engine fuel economy, engine manufacturers aretrying their best to reduce engine weight. One of the ways to reduce the engine weight is toreduce the weight of the cylinder block. Therefore, aluminum has been applied.Aluminum is a very light metal.Before pouring aluminum metal into themold, some materials should be added to aluminum metal in order toincrease the strength of aluminum and reduce the possibility ofwarping when it is heated during combustion. The aluminum cylinder block must also have acylinder liner or a steel bushing embedded in the cylinderblock. Steel bushings should beplaced in the mold before aluminum metal is poured into themold. After pouring aluminummetal, the steel bushing cannot be removed.Silicon should also be added to aluminummetal. Through a specialprocess, silicon is concentrated on the cylinder wall.This process reduces the need forsteel bushings. This design iscalled the wall of the silicon-impregnated cylinder.One problem with this design is theneed to use high-quality engine oil. If the user neglects to use low-quality engineoil, this kind of engine usually cannot reach its expected servicelife.4. Piston thrustsurfaceWhen the piston moves upand down in the cylinder, there are two kinds of thrust on the sideof the piston: larger and smaller. When the piston is viewed from the back of theengine, the smaller thrust is the pressure acting on the right sideof the piston. Less thrust isgenerated in the compression stroke, when the engine rotatesclockwise. On the contrary,when viewed from the back and the engine rotates clockwise, thelarger thrust is the pressure acting on the left side of thepiston. When the piston is inthe power stroke, it produces a large thrust. When the crankshaft rotates around TDC, the pistonswitches between larger and smaller thrust, which means that thepiston collides with the cylinder wall. When the gap between the piston and the cylinderwall is too large, there will be excessive impact, which will leadto noise and wear on the piston and cylinder wall.Excessive piston impact is usuallyeliminated by replacing the piston ring or installing an enlargedpiston and piston ring after boring thecylinder.5. CylinderwearThe movement of piston andpiston ring makes the cylinder wear evenly and gradually becomesconical. Fig. 11(a) illustrateshow a typical cylinder is worn. The cone shape only occurs where the piston ringcontacts the cylinder wall. Alarge degree of wear occurs at the top of the cylinder and a smalldegree of wear occurs at the bottom of the cylinder.This wear has formed a bulge in theupper part of the cylinder bore. During overhaul, the piston must be removed afterthe bulge is removed. If the bulge is not removed, the piston willbe damaged once it is removed. After the new piston ring is installed, the bottomof the bump may also be damaged. The manufacturer's specifications listed in thegenerator set maintenance manual only allow a certain amount oftaper of the cylinder wall. Excessive taper will affect the end clearance ofpiston ring, as shown in Figure 11(b). Excessive end clearance, as shown at the top ofthe cylinder wall, will produce a great piston ring end clearance,which will produce excessive blowby.6. Cylinder running-inWhen a new piston ring is placed on the piston,the piston ring and the cylinder wall are not completely sealed,and the difference is shown in Figure 12. The part where the piston ring contacts thecylinder is only a slight protrusion on the piston ring.This makes the seal between the fineparts on the piston ring and the cylinder wall poor.As a result, the piston ring andcylinder wall surfaces are designed to be slightly convex andconcave, and then as the piston ring and cylinder wall begin towear, the protruding part on the surface will wear first, and thenthe two objects will tend to be close. This process is called running-in in theengine.Some manufacturersrecommend running for a certain distance, that is, the running-inperiod. During the running-inperiod, the piston ring and cylinder are properly worn, so that thepiston ring is effectively sealed.Honing is the operation of producing a net patternon the cylinder surface. Honingalso helps to keep some lubricating oil on the cylinderwall. These remaininglubricating oils help to lubricate new piston rings and facilitatethe running-in process. Finegrinding is another process to improve the cylinder wall.Fine grinding is different fromhoning. Honing is used to roughen the cylinder wall and removeglossy surface, while fine grinding is used to round the cylinderwall. Although pistons of thesame size can be used, fine grinding will remove more material thanhoning. Fine grindstones arevery hard tools, usually with four grindstones, while honingmachines only have three grindstones.