Friday, April 5, 2019

Engine Cooling And Lubrication System

railway locomotive Cooling And Lubrication SystemCooling System Despite the vast forward motion in the basic interior fire locomotive railway locomotives, around 70% of the zilch from the gasoline is converted to passionateness. As it is non dissipated to the melodic phrase on its own, a locomotive locomotive placiding formation establishment is employed for this purpose.Several purposes of the cooling system which it serves by cooling the engine include cooling the engine to keep it from over kindleing by transferring the mania to the communication channel. This helps avoid the prodigal arrogate and tear at high temperatures, auto-ignition collect to hot cylinder which may outlet in knocking and hence, diver/cylinder failure. It may to a fault incorporate thermal stresses which is not good for the engine itself.Figure . Cooling system and plumbing connectionWhile it serves the purpose of cooling the engine, it too helps the engine to warm up quickly du ring cold start ups and then maintaining a constant temperature. When the engine is cold, components fag out faster too and the engine is less efficient, emitting to a great extent pollution.Types of Cooling SystemThere argon two types of cooling systems found in carsAir-cooledLiquid-CooledAir-Cooled EnginesMany small and the medium-sized engines argon beam-cooled. This form includes most(prenominal) small engines the exchangeables of lawn mowers, chain saws, model airplanes etc. Using the air-cooled system allows both(prenominal) the weight and price of the engine to be kept low, a tenacious with digestd complexity of the machine.The air-cooled system is still widely utilise on most of the motor bouts in white plague these days. This system utilizes the concept of raise up transfer by means of and through fins to cool the engine. The cross-sectional bea of the fin being larger closer to the brainiac and a reduction in the bea as we move further from the engine block .The basic pattern on which the air-cooled engines rely on is the hang up of air across their external surfaces to remove the senseless heat to keep the engine from overheating. The air lessen on machines like motorcycles and aircrafts is allow ford across the surface when the vehicle moves forrad. Deflectors and ductwork is compound to direct the air coalesce to the critical locations where more cooling is required. The outer surface of the engine is do from a good conductor of heat and the surface is finned to promote maximum heat transfer, along with which an extra buffer is use to increase the air- settle rate whereas separates use the concept of free-convection. These fins argon to be veraciously designed for catch cooling effect which is required.Some automobile engines also use exposed flywheels with air-deflectors fastened to the surface. When the engine is in operation, these deflectors attain air motion which increases the heat transfer on the finned surface.Ev en after considering and applying all the measures, the like cooling of cylinders is still difficult to achieve on air-cooled engines as compared to the eloquent-cooled engines. The figure below shows that the cooling needs are not the same at all the locations.Figure . Variation of heat losings from the fins of an air-cooled aircraft engine. Seventy-one percent of the heat losses occur on the hotter side of the cylinder, containing the exhaust valve. The engine shown was utilise on a reckon of different aircrafts.Hotter areas, much(prenominal) as the ones around the exhaust valve and complicated need great cooling and hence larger finned surface area. Cooling the campaign of an air-cooled engine which faces the forward motion of the vehicle is frequently easier and efficient as compared to the confirm surface of the engine. This may result in temperature differences and thermal expansion problems.DisadvantagesDisadvantages of air-cooled engines are that theyAre less effic ient,Are noisier, with greater air flow requirements and no urine system jacket to dampen the noise,Need a directed air flow and finned surfaces.AdvantagesWhen compared with liquid-cooled engines, air-cooled engines pay off the following advantagesThey are lighter in weight,They cost less,No coolant system failures (e.g., water bosom, hoses),No engine freeze-ups, andFaster engine warmup.Liquid-Cooled EnginesIn a liquid or water-cooled engine, the engine block is surrounded by a water jacket through which the coolant flows. This allows for a better entertain of the heat removal from the engine, scarcely by hang oned weight and a more complex system.Very close to water-cooled engines use just water as the cooling fluid in the water jackets this is because the water has a freezing temperature of 0C which is unacceptable as coolant in colder regions, so additives are unremarkably used for better performance. Although water has very good heat transfer properties, nevertheless when used alone, it causes crumble and corrosion in many of the pipes of the cooling system.Ethylene glycol (C2H6O2) is the antifreeze agent which acts as a eat up inhibitor and a lubricator for the water pump. When added to water, it frowns the freezing temperature and raises the b crudeing temperature of the coolant. The properties of the mixture depend on the ratio in which water and the antifreeze agent are mixed. Pure ethylene glycol should not be used, and even at high concentrations the heat transfer properties of the water are lost as good. The properties of the ethylene glycol water mixture are shown in the table below.In addition to good thermal properties, a coolant should run into the following requirements1. Chemically stable under conditions of use2. Non-foaming3. Non-corrosive4. Low toxicity5. Non-flammable6. Low cost just about moneymaking(prenominal) antifreezes satisfy these requirements. Many of them are basically ethylene glycol with small amounts of addi tives. Some commercial engine coolants use propylene glycol as the base ingredient. It is argued that when coolant systems leak or when the coolant be seminal fluids aged and is discarded, these products are less harmful to the environment than ethylene glycol. elementary ComponentsThe basic components of a liquid-cooled system is shown below.Figure . Basic liquid-cooled systemradiatorradiator top hoseradiator undersurface hosewater pumpthermostatthermostat lodging galvanizing cooling loverthermo-time switchRadiatorThe radiator is the trigger off of the cooling system which is responsible for the heat rejection from the coolant and into the atmosphere. The radiator magnetic core is usually made up of flattened tubes with aluminum strips (fins) that zigzag among the tubes. These fins effectively transfer the heat contained in the coolant into the air stream to be lost into the atmosphere. On each end of the radiator is a store made up of plastic to cover the ends. The tubes eith er run horizontally or vertically between the two storage tanks. The aluminum-plastic system is more efficient and cost effective.On radiators with plastic end caps, there are gaskets between the aluminum core and the plastic tanks to mould the system and keep the fluid from leaking out. The tanks have a large hose connection, one mounted towards the top of the radiator to let the coolant in, the other mounted at the bottom of the radiator on the other tank to let the coolant binding out. On the top of the radiator is an additional opening that is lie off by the radiator cap.Another component in the radiator for vehicles with an automatic transmission is a separate tank mounted inside one of the tanks. Fittings connect this inner tank through steel tubes to the automatic transmission. infection fluid is piped through this tank inside a tank to be cooled by the coolant flowing historic it ahead returning to the transmission.Radiator FansOne or two electric raw siennas are mou nted on the back of the radiator close to the engine. These fans used the concept of hale convection to cool the heated coolant going through the pipes in the radiator core.If noticed, this fan starts working once the engine reaches a predefined temperature, after which the cooling by just natural convection during the forward motion of the car pratnot be achieved. In the cars with air conditioning, there is an additional radiator mounted in front of the dominion radiator. This radiator is called the air conditioner condenser, which also needs to be cooled by the air flow entering the engine compartment. As long as the air conditioning is turned on, the system will keep the fan running, even if the engine is not running hot. This is because if there is no air flow through the air conditioning condenser, the air conditioner will not be able to cool the air entering the interior. force cap reserve tankThe extort cap is simply a cap which maintains the wardrobe in the cooling sy stem up to a certain rank. If the pressure builds up higher than the set pressure point, the spring loaded valve releases the pressure.Figure . Pressure capWhen the pressure in the cooling system reaches the point when the cap needs to release this excess pressure, more or less amount of coolant is bled off. The coolant which is bled off goes into the reserve tank which is not pressurized, which causes a partial vacuum in the cooling system.The radiator cap on these closed systems has a collateral valve which allows the vacuum in the cooling system to draw the coolant back from the reserve tank into the radiator.Coolant PumpIt is a simple pump which helps in circulation of the coolant around the system. This pump is run using one of the followingA fan belt that will also be responsible for driving an additional component like an alternator or power steering pumpA serpentine belt, which also drives the alternator, power steering pump and AC compressor among other things.The timing belt that is also responsible for driving one or more camshafts.The impeller of the pump uses centrifugal force to draw the coolant in from the lower radiator hose and send it under pressure to the engine block. A gasket seals the water pump to the engine block and prevents the flowing coolant from leaking out where the pump is given to the block.ThermostatThe thermostat is simply a valve that measures the temperature of the coolant, and if the coolant is hot enough it opens to allow the coolant to flow through the radiator other than the flow to the radiator is blocked and the fluid is directed to a bypass system that returns the coolant to the engine.Figure . ThermostatThe engine is at times allowed to run at higher temperatures of 190-195C this reduces emissions, moisture condensation inside the engine is quickly burned off amend engine livelihood, and a more complete combustion improving evoke economy. anoint as a CoolantThe rock fossil embrocate when used to lubricate the engine also helps to cool the engine. The piston for example gets very itty-bitty cooling from the coolant in the water jacket or the externally finned surface, so when the back surface of the piston confidential information is subjected to the anele colour sputter or flow the piston is cooled to slightly extent. This is very necessary as the piston is one of the hottest elements in the engine. Usually, the anoint is sprayed in pressurized systems, and dot in non-pressurized systems. The cover acts as the coolant on the back face of the piston crown as it absorbs energy and then runs back into the larger beginning where it mixes with the cooler petroleum and dissipates this energy into the other engine parts. This pat cooling of the piston is highly important in small air-cooled engines as well as in automobile engines.A few other engine components other than the piston are also cooled by anele circulation, either by splash or by the pressurized flow from the oil pu mp. anele passages through internal components like the camshaft and connecting rods offer the only major cooling these parts are subjected to. As the oil cools the various components, it absorbs energy and its temperature rises. This energy is then dissipated to the rest of the engine by circulation and at last gets absorbed in the engine coolant flow. Some high-performance engines have an oil cooler in their lubri mintt circulation system. The energy absorbed by the oil as it cools the engine components is dissipated in the oil cooler, which is a heat ex tiltr cooled by either engine coolant flow or external air flow. embrocate Pump The gear-type oil pump has a pair of meshing gears. The spaces between the teeth are fill up with oil when the gears unmesh. The oil pump obtains oil from the oil pan and sends oil through the oil interpenetrate to the oil galleries and main bearings. Some oil passes from the holes in the crankshaft to the rod bearings. Main bearings and rod bearin gs are be adequately to achieve their desired objectives. In the rotor type oil pump, the inner rotor is operate and drives the outer rotor. As the rotor revolves, the gaps between the lobes are filled with oil. When the lobes of the inner rotor move into the gaps in the outer rotor, oil is forced out through the outlet of pump. An oil pump crowd out also be driven by a camshaft gear that drives the ignition distri just nowor or by the crankshaft.Oil Pan Oil also flows to the cylinder head through drilled passages that make up the oil gallery, lubricates camshaft bearings and valves, and then returns to oil pan. Some engines have grooves or holes in connecting rods, which provide extra lubrication to pistons and walls of cylinders.Oil cool Oil cooler prevents overheating of oil, by flow of engine coolant retiring(a) tubes carrying hot oil. The coolant picks excess heat and carries it to the radiator.Oil stress The oil from oil pump flows through oil percolate ahead grasp th e engine bearings. The oil filter retains the dirt particles and allows only clean filtered oil to pass.The Lubrication system and its typesThere are three basic types of oil distribution systems used in enginesSplash,Pressurized, orA combination of these.The crankcase is used as the oil sump (reservoir) in a splash system, and the crankshaft rotating at high fastness in the oil distributes it to the various moving parts by splash no oil pump is used. totally components, including the valve train and camshaft, mustiness(prenominal) be open to the crankcase. Oil is splashed into the cylinders behind the pistons and onto the back of the piston crowns, performing both as a lubricant and a coolant. Many small four-stroke cycle engines (lawn mowers, golf carts, etc.) use splash distribution of oil.An engine with a pressurized oil distribution system uses an oil pump to picture lubrication to the moving parts through passages construct into the components. A typical automobile engin e has oil passages built into the connecting rods, valve stems, push rods, rocker arms, valve seats, engine block, and many other moving components. These make up a circulation net income through which oil is distributed by the oil pump. In addition, oil is sprayed under pressure onto the cylinder walls and onto the back of the piston crowns. Most automobiles actually use three-fold distribution systems, relying on splash at bottom the crankcase in addition to the pressurized flow from the oil pump. Most large stationary engines also use this kind of dual system. Most aircraft engines and a few automobile engines use a total pressurized system with the oil reservoir located separate from the crankcase. These are often called dry sump systems (i.e., the crankcase sump is dry of excess oil). Aircraft do not always fly level, and uncontrolled oil in the crankcase may not tack on proper lubrication or oil pump input when the plane banks or turns. A diaphragm controls the oil level i n the reservoir of a dry sump system, assuring a continuous flow into the oil pump and end-to-end the engine.Figure . Lubrication of an engine consisting of a combination of a pressurized system and splash systemOil pumps can be electric or robotlikely driven off the engine. Pressure at the pump exit is typically about 300 to cd kPa. If an oil pump is driven straight out off the engine, round means should be built into the system to keep the exit pressure and flow rate from becoming excessive at high engine speeds.A time of excess wear is at engine startup before the oil pump can distribute proper lubrication. It takes a few engine cycles before the flow of oil is fully established, and during this time, many parts are not properly lubricate. Adding to the problem is the fact that often the oil is cold at engine startup. Cold oil has much higher viscosity, which further delays proper circulation. A few engines have oil preheaters which electrically heat the oil before startup. Some engines have pre-oilers that heat and circulate the oil before engine startup. An electric pump lubricates all components by distributing oil throughout the engine.It is recommended that turbocharged engines be allowed to idle for a few seconds before they are turned off. This is because of the very high speeds at which the turbocharger operates. When the engine is turned off, oil circulation stops and lubricated surfaces begin to lose oil. Stopping the oil supply to a turbocharger operating at high speed invites poor lubrication and high wear. To minimize this problem, the engine and turbocharger should be allowed to return to low speed (idle) before the lubrication supply is stopped.Lubrication system in 2-stroke enginesMany small engines and some experimental two-stroke cycle automobile engines use the crankcase as a compressor for the inlet air. Automobile engines which do this generally have the crankcase divided into some(prenominal) compartments, with each cylinder hav ing its own separate compressor. These engines cannot use the crankcase as an oil sump, and an alternate method must be used to lubricate the crankshaft and other components in the crankcase. In these engines, oil is carried into the engine with the inlet air in much the same way as the fuel. When the fuel is added to the inlet air, usually with a carburetor, oil particles as well as fuel particles are distributed into the flow. The air flow then enters the crankcase, where it is compressed. Oil particles carried with the air lubricate the surfaces they come in contact with, first in the crankcase and then in the intake runner and cylinder.In some systems (model airplane engines, marine outboard motors, etc.), the oil is premixed with the fuel in the fuel tank. In other engines (automobiles, some golf carts, etc.), there is a separate oil reservoir that feeds a metered flow of oil into the fuel supply line or directly into the inlet air flow. Fuel-to-oil ratio ranges from 301 to 400 1, depending on the engine. Some modern high-performance engines have controls which regulate the fuel-oil ratio, depending on engine speed and load. at a lower place conditions of high oil input, oil sometimes condenses in the crankcase. Up to 30% of the oil is recirculated from the crankcase in some automobile engines. It is desirable to get at least 3000 miles per liter of oil used. Most small lower cost engines have a single average oil input setting. If too much oil is supplied, deposits form on the combustion chamber walls and valves will stick (if there are valves). If too little oil is supplied, excess wear will occur and the piston can freeze in the cylinder.Engines that add oil to the inlet fuel obviously are designed to use up oil during operation. This oil also contributes to HC emissions in the exhaust due to valve overlap and poor combustion of the oil vapor in the cylinders. New oils that also burn better as fuel are being developed for two-stroke cycle engines. Some two-stroke cycle automobile engines and other medium- and large-size engines use an external supercharger to compress inlet air. These engines use pressurized/ splash lubrication systems similar to those on four-stroke cycle engines with the crankcase also serving as the oil sump.Lubricating OilThe oil used in an engine must serve as a lubricant, a coolant, and a vehicle for removing impurities. It must be able to withstand high temperatures without breaking down and must have a long working life. The development trend in engines is toward higher operating temperatures, higher speeds, closer tolerances, and smaller oil sump capacity. both of these require improved oils compared to those used just a few years ago. Certainly, the engine room of the oil industry has to continue to improve along with the technology growth of engines and fuel. Early engines and other mechanical systems were often designed to use up the lubricating oil as it was used, requiring a continuous input of r einvigorated oil. The used oil was either burned up in the combustion chamber or allowed to go past to the ground. Just a couple of decades back, the tolerances between pistons and cylinder walls was such that engines burned some oil that seeped past the pistons from the crankcase. This required a periodic need to add oil and a frequent oil change due to blowby contamination of the remaining oil. HC levels in the exhaust were high because of the oil in the combustion chamber. advanced engines run hotter, have closer tolerances which keep oil consumption down, and have smaller oil sumps due to space limitations. They generate more power with smaller engines by running faster and with higher concretion ratios. This means higher forces and a greater need for good lubrication. At the same time, many manufacturers straight off suggest changing the oil every 6000 miles. Not only must the oil last semipermanent under much more severe conditions, but new oil is not added between oil cha nges. Engines of the past that consumed some oil required periodic makeup oil to be added. This makeup oil mixed with the remaining used oil and improved the overall lubrication properties within the engine.The oils in modern engines must operate over an extreme temperature range. They must lubricate properly from the starting temperature of a cold engine to beyond the extreme steady-state temperatures that occur within the engine cylinders. They must not oxidize on the combustion chamber walls or at other hot spots such as the center crown of the piston or at the top piston ring. Oil should adhere to surfaces so that they always lubricate and provide a protective covering against corrosion. This is often called oiliness. Oil should have high film power to assure no metal-to-metal contact even under extreme loads. Oils should be non-toxic and non-explosive.Some desired qualities of Lubrication oilLubricating oil must satisfy the following needsLubrication. It must reduce friction a nd wear within the engine. It improves efficiency by reducing the friction forces between moving parts.CoolantRemoval of contaminantsEnhancement of ring seal and reduction of blowbySlow corrosionStability over a large temperature rangeLong life spanLow costHydrocarbon Components in Lubricating oilThe basic ingredients in most lubricating oils are hydrocarbon components made from crude oil. These are larger molecular weight species obtained from the distillation process.AdditivesVarious other components are added to create a lubricant that will allow for the maximum performance and life span of the engine. These additives includeAntifoam agentsThese reduce the foaming that would result when the crankshaft and other components rotate at high speed in the crankcase oil sump. oxidisation inhibitorsOxygen is trapped in the oil when foaming occurs, and this leads to possible oxidation of engine components. One such additive is zinc dithiophosphatePour-point depressantAntirust agentsDeterg entsThese are made from organic salts and metallic salts. They help keep deposits and impurities in suspension and stop reactions that form varnish and other surface deposits. They help neutralize acid form from sulfur in the fuel.Anti-wear agentsFriction reducersviscosity index improversRating of Lubricating Oils and gradesLubricating oils are generally rated using a viscosity scale established by the Society of Automotive Engineering (SAE).The higher the viscosity value, the greater is the force needed to move adjacent surfaces or to pump oil through a passage. Viscosity is highly dependent on temperature, increasing with fall temperature. In the temperature range of engine operation, the dynamic viscosity of the oil can change by more than an order of magnitude. Oil viscosity also changes with shear, decreasing with increasing shear. Shear rates within an engine range from very low values to extremely high values in the bearings and between piston and cylinder walls. The change of viscosity over these extremes can be some(prenominal) orders of magnitude. Common viscosity grades used in engines areSAE 5SAE 10SAE 20SAE 30SAE 40SAE 45SAE 50Common oils available includeSAE 5W-20 SAE 10W-40SAE 5W-30 SAE 10W-50SAE 5W-40 SAE 15W-40SAE 5W-50 SAE 15W-50SAE 10W-30 SAE 20W-50Synthetic OilsA number of synthetically made oils are available that give better performance than those made from crude oil. They are better at reducing friction and engine wear, have good detergency properties which keep the engine cleaner, offer less resistance for moving parts, and require less pumping power for distribution. With good thermal properties, they provide better engine cooling and less variation in viscosity. Because of this, they contribute to better cold-weather starting and can reduce fuel consumption by as much as 15%. These oils cost several times as much as those made from crude oil. However, they can be used bimestrial in an engine, with 24,000 km (15,000 miles) being the oil change period suggested by most manufacturers.Available on the market are various oil additives and special oils that can be added in small quantities to measuring rod oils in the engine. These claim, with some justification, to improve the viscous and wear resistance properties of normal oils. One major improvement that some of them provide is that they stick to metal surfaces and do not drain off when the engine is stopped, as most standard oils do. The surfaces are thus lubricated immediately when the engine is next started. With standard oils it takes several engine rotations before proper lubrication occurs, a major source of wear.Oil filtersIncluded in most pressurized oil systems is a filtration system to remove impurities from the engine oil. One of the duties of engine oil is to clean the engine by carrying contaminant impurities in suspension as it circulates. As the oil passes through filters that are part of the flow passage system these impurities are removed, cle aning the oil and allowing it to be used for a greater length of time. Contaminants get into an engine in the incoming air or fuel or can be generated within the combustion chamber when other than ideal stoichiometric combustion occurs. Dust and other impurities are carried by the incoming air. Some, but not all, of these are removed by an air filter.Fuels have trace amounts of impurities like sulfur, which create contaminants during the combustion process. Even pure fuel components form some contaminants, like solid carbon in some engines under some conditions. Many engine impurities are carried away with the engine exhaust, but some get into the interior of the engine, mainly in the blowby process. During blowby, fuel, air, and combustion products are forced past the pistons into the crankcase, where they mix with the engine oil. Some of the water vapor in the exhaust products condenses in the crankcase, and the resulting liquid water adds to the contaminants. The gases of blowby pass through the crankcase and are routed back into the air intake. Ideally, most of the contaminants are trapped in the oil, which then contains dust, carbon, fuel particles, sulfur, water knock offlets, and many other impurities. If these were not filtered out of the oil, they would be spread throughout the engine by the oil distribution system. Also, the oil would quickly become dirty and lose its lubricating properties, resulting in greater engine wear.Figure . Oil FilterFlow passages in a filter are not all the same size but usually exist in a normal bell-shaped size distribution. This means that most larger particles will be filtered out as the oil passes through the filter, but a few as large as the largest passages will get through. The pickaxe of filter contract size is a compromise. Better filtration will be obtained with smaller filter pores, but this requires a much greater flow pressure to push the oil through the filter. This also results in the filter becoming clog ged quicker and requiring earlier filter cartridge change. Some filter materials and/or material of too small a pore size can even remove some additives from the oil. Filters are made from cotton, paper, cellulose, and a number of different synthetic materials. Filters are usually located just downstream from the oil pump exit. As a filter is used, it slowly becomes saturated with trapped impurities. As these impurities fill the filter pores, a greater pressure differential is needed to keep the same flow rate. When this needed pressure differential gets too high, the oil pump limit is reached and oil flow through the engine is slowed. The filter cartridge should be replaced before this happens.Figure . Exploded view of an Oil FilterFigure . Pore size distribution for common filtersSometimes, when the pressure differential across a filter gets high enough, the cartridge structure will collapse and a hole will develop through the cartridge wall. Most of the oil pumped through the fil ter will then follow the room of least resistance and flow through the hole. This short circuit will reduce the pressure drop across the filter, but the oil does not get filtered.There are several ways in which the oil circulation system can be filtered1. Full-flow oil filtration. All oil flows through the filter. The filter pore size must be fairly large to avoid extreme pressures in the resulting large flow rate. This results in some larger impurities in the oil.2. Bypass oil filtration. Only part of the oil going away the pump flows through the filter, the rest bypassing it without being filtered. This system allows the use of a much finer filter, but only a percentage of the oil gets filtered during each circulation loop.3. Combination. Some systems use a combination of full-flow and bypass. All the oil first flows through a filter with large pores and then some of it flows through a second filter with small pores.4. Shunt filtration. This is a system using a full-flow filter a nd a bypass valve. All oil at first flows through the filter. As the filter cartridge dirties with age, the pressure differential across it needed to keep the oil flowing increases. When this pressure differential gets above a predetermined value, the bypass valve opens and the oil flows around the filter. The filter cartridge must then be replaced before filtering will again occur.Solid lubricants, such as powd

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