Reciprocating Engine Lubrication Systems PDF

RECIPROCATING ENGINE Intro 1 Reciprocating Engine Lubrication Systems Oil Pump Oil entering the engine is pressurized, filtered, and regulated by units within th...

RECIPROCATING ENGINE Intro 1 Reciprocating Engine Lubrication Systems Oil Pump Oil entering the engine is pressurized, filtered, and regulated by units within the engine. They are discussed along with the external oil system to provide a concept of the complete oil system. https://youtu.be/eFe43SnBl MI 2 Reciprocating Engine Lubrication Systems Oil Pump As oil enters the engine, it is pressurized by a gear- type pump [Figure 6-6] 3 Reciprocating Engine Oil Pump This pump is a positive displacement pump that consists Lubrication Systems of two meshed gears that revolve inside the housing The clearance between the teeth and housing is small The pump inlet is located on the left and the discharge port is connected to the engine’s system pressure line One gear is attached to a splined drive shaft that extends from the pump housing to an accessory drive shaft on the engine Seals are used to prevent leakage around the drive shaft As the lower gear is rotated 4 counterclockwise, the driven idler gear turns clockwise  Oil Pump As oil enters the gear chamber, it is picked up by the gear teeth, trapped between them and the sides of the gear chamber, is carried around the outside of the gears, and discharged from the pressure port into the oil screen passage The pressurized oil flows to the oil filter, where any solid particles suspended in the oil are separated from it, preventing possible damage to moving parts Reciprocating Engine of the engine Lubrication Systems 5 Reciprocating Engine Oil Pump Lubrication Systems Oil under pressure then opens the oil filter check valve mounted in the top of the filter. This valve is used mostly with dry sump radial engines and is closed by a light spring loading of 1 to 3 pounds per square inch (psi) when the engine is not operating to prevent gravity-fed oil from entering the engine and settling in the lower cylinders or sump area of the engine If oil were allowed to gradually seep by the rings of the piston and fill the combustion chamber, it could cause a liquid lock This could happen if the valves on the cylinder were both closed and the engine was cranked for start Damage could occur to the engine 6 Reciprocating Engine Oil Pump Lubrication Systems The oil filter bypass valve, located between the pressure side of the oil pump and the oil filter, permits unfiltered oil to bypass the filter and enter the engine if the oil filter is clogged or during cold weather if congealed oil is blocking the filter during engine start The spring loading on the bypass valve allows the valve to open before the oil pressure collapses the filter; in the case of cold, congealed oil, it provides a low- resistance path around the filter. Dirty oil in an engine is better than no lubrication 7 Reciprocating Engine Lubrication Systems Oil Filters The oil filter used on an aircraft engine is usually one of four types: – Screen – Canister – spin-on – Cuno 8 Reciprocating Engine Lubrication Systems Oil Filters A screen-type filter with its double-walled construction provides a large filtering area in a compact unit. [Figure 6-6] 9 Reciprocating Engine Oil Filters Lubrication Systems As oil passes through the fine-mesh screen, dirt, sediment, and other foreign matter are removed and settle to the bottom of the housing At regular intervals, the cover is removed and the screen and housing cleaned with a solvent Oil screen filters are used mostly as suction filters on the inlet of the oil pump 10 Reciprocating Engine Oil Filters A canister housing filter Lubrication has a replaceable filter element Systems that is replaced with rest of the components other than seals and gaskets being reused [Figure 6-7] 11 Reciprocating Engine Oil Filters Lubrication Systems The filter element is designed with a corrugated, strong steel center tube supporting each convoluted pleat of the filter media, resulting in a higher collapse pressure rating. The filter provides excellent filtration, because the oil flows through many layers of locked-in-fibers 12 Reciprocating Engine Lubrication Systems Oil Filters Full flow spin-on filters are the most widely used oil filters for reciprocating engines. [Figure 6-8] 13 Reciprocating Engine Lubrication Systems Oil Filters Full flow spin-on filters 14 Reciprocating Engine Oil Filters Lubrication Systems Full flow means all the oil is normally passed through the filter the filter is positioned between the oil pump and the engine bearings filters the oil of any contaminants before they pass through the engine bearing surfaces also contains an – anti-drain back valve – pressure relief valve – all sealed in a disposable housing 15 Reciprocating Engine Lubrication Systems Oil Filters relief valve is used in case the filter becomes clogged The relief valve opens to allow the oil to bypass, preventing the engine components from oil starvation 16 Reciprocating Engine Lubrication Systems Oil Filters A cutaway of the micronic filter element shows the resin- impregnated cellulosic full-pleat media that is used to trap harmful particles, keeping them from entering the engine. [Figure 6-9] 17 Reciprocating Engine Lubrication Systems 18 Reciprocating Engine https://www.youtube.com/watch?v=Rt_AWy4tsN0&t=130s Lubrication Systems 19 Reciprocating Engine Lubrication Systems Oil Pressure Regulating Valve An oil pressure regulating valve limits oil pressure to a predetermined value, depending on the installation. [Figure 6-6] 20 Reciprocating Engine 21 Lubrication Systems Oil Pressure Regulating Valve This valve is sometimes referred to as a relief valve but its real function is to regulate the oil pressure at a preset pressure level The oil pressure must be sufficiently high to ensure adequate lubrication of the engine and its accessories at high speeds and powers This pressure helps ensure that the oil film between the crankshaft journal and bearing is maintained However, the pressure must not be too high, as leakage and damage to the oil system may result Reciprocating Engines BREAK! RETURN AT 2 22 Reciprocating Engine Lubrication Systems Oil Pressure Regulating Valve The oil pressure is generally adjusted by loosening the locknut and turning the adjusting screw. [Figure 6-10] 23  Oil Pressure Regulating Valve On most aircraft engines, turning the screw clockwise increases the tension of the Reciprocating Engine spring that holds the relief valve on its seat and increases the oil pressure; turning the adjusting screw counterclockwise decreases the spring tension and lowers the pressure Lubrication Systems Some engines use washers under the spring that are either removed or added to adjust the regulating valve and pressure 24 Reciprocating Engine Lubrication Systems Oil Pressure Regulating Valve The oil pressure should be adjusted only after the engine’s oil is at operating temperature and the correct viscosity is verified The exact procedure for adjusting the oil pressure and the factors that vary an oil pressure setting are included in applicable manufacturer’s instructions 25 Reciprocating Engine Oil Pressure Gauge Usually, the oil pressure Lubrication Systems gauge indicates the pressure that oil enters the engine from the pump This gauge warns of possible engine failure caused by an exhausted oil supply, failure of the oil pump, burned-out bearings, ruptured oil lines, or other causes that may be indicated by a loss of oil pressure 26  Oil Pressure Gauge Reciprocating Engine One type of oil pressure gauge uses a Bourdon-tube Lubrication Systems mechanism that measures the difference between oil pressure and cabin, or atmospheric, pressure This gauge is constructed similarly to other Bourdon-type gauges, except that it has a small restriction built into the instrument case, or into the nipple connection leading to the Bourdon tube This restriction prevents the surging action of the oil pump from damaging the gauge or causing the pointer to oscillate 27 too violently with each pressure pulsation Reciprocating Engine Lubrication Systems Oil Pressure Gauge The oil pressure gauge has a scale ranging from 0–200 psi, or from 0– 300 psi Operation range markings are placed on the cover glass, or the face of the gauge, to indicate the safe range of oil pressure for a given installation 28  Oil Pressure Gauge A dual-type oil pressure gauge is available for use on multiengine aircraft The dual indicator contains two Bourdon tubes, housed in a standard instrument case; one tube being used for each engine The connections extend from the back of the case to each engine There is one common movement assembly, but the moving parts function independently In some installations, the line leading from the engine to the pressure gauge is filled with light Reciprocating Engine oil Lubrication Systems 29 Reciprocating Engine Oil Pressure Gauge Lubrication Systems Since the viscosity of this oil does not vary much with changes in temperature, the gauge responds better to changes in oil pressure In time, engine oil mixes with some of the light oil in the line to the transmitter; during cold weather, the thicker mixture causes sluggish instrument readings To correct this condition, the gauge line must be disconnected, drained, and refilled with light oil 30 Reciprocating Engine Lubrication Systems Oil Pressure Gauge The current trend is toward electrical transmitters and indicators for oil and fuel pressure-indicating systems in all aircraft In this type of indicating system, the oil pressure being measured is applied to the inlet port of the electrical transmitter where it is conducted to a diaphragm assembly by a capillary tube 31  Oil Pressure Gauge The motion produced by the diaphragm’s expansion and contraction is amplified through Reciprocating Engine a lever and gear arrangement. The gear varies the electrical value of the indicating circuit, which in turn, is reflected on Lubrication Systems the indicator in the cockpit. This type of indicating system replaces long fluid filled tubing lines with an almost weightless piece of wire 32 Reciprocating Engine Oil Temperature Indicator Lubrication Systems In dry-sump lubricating systems, the oil temperature bulb may be anywhere in the oil inlet line between the supply tank and the engine. Oil systems for wet-sump engines have the temperature bulb located where it senses oil temperature after the oil passes through the oil cooler. 33 Reciprocating Engine Oil Temperature Indicator Lubrication Systems In either system, the bulb is located so that it measures the temperature of the oil before it enters the engine’s hot sections. An oil temperature gauge in the cockpit is connected to the oil temperature bulb by electrical leads. The oil temperature is indicated on the gauge. Any malfunction of the oil cooling system appears as an abnormal reading. 34 Reciprocating Engine Lubrication Systems Oil Cooler The cooler consists of a core enclosed in a double- walled shell The core is built of copper or aluminum tubes with the tube ends formed to a hexagonal shape and joined together in the honeycomb effect. [Figure 6-11] 35 Reciprocating Engine Oil Cooler Lubrication Systems The ends of the copper tubes of the core are soldered, whereas aluminum tubes are brazed or mechanically joined The tubes touch only at the ends so that a space exists 36 between them along most of their lengths This allows oil to flow through the spaces between the tubes while the cooling air passes through the tubes. Oil Change-Cessna 172 Reciprocating Engine 37 Lubrication Systems Oil Cooler The space between the inner and outer shells is known as the annular or bypass jacket Two paths are open to the flow of oil through a cooler From the inlet, it can flow halfway around the bypass jacket, enter the core from the bottom, and then pass through the spaces between the tubes and out to the oil tank This is the path the oil follows when it is hot enough to require cooling As the oil flows through the core, it is guided by baffles that force the oil to travel back and forth several times before it reaches the core outlet. Reciprocating Engines BREAK! RETURN AT 3 38  Oil Cooler The oil can also pass from the inlet completely around the bypass jacket to the outlet without passing through the core Oil follows this bypass route when the oil is cold or when the core is blocked with thick, congealed oil. Reciprocating Engine Lubrication Systems 39  Oil Cooler Flow Control Valve The viscosity of the oil varies with its temperature Since the viscosity affects its lubricating properties, the temperature at which the oil enters an engine must be held within close limits Generally, the oil leaving an engine must be cooled before it is recirculated Obviously, the amount of cooling must be controlled if the oil is to return to the engine at the correct temperature The oil cooler flow control valve determines which of the two Reciprocating Engine possible paths the oil takes through the oil cooler Lubrication Systems 40  Oil Cooler Flow Control Valve [Figure 6-12] Reciprocating Engine Lubrication Systems 41  Oil Cooler Flow Control Valve There are two openings in a flow control valve that fit over the corresponding outlets at the top of the cooler When the oil is cold, a bellows within the flow control contracts and lifts a valve from its seat Under this condition, oil entering the cooler has a choice of two outlets and two paths Following the path of least resistance, the oil flows around the jacket and out past the thermostatic valve to the tank Reciprocating Engine Lubrication Systems 42  Oil Cooler Flow Control Valve This allows the oil to warm up quickly and, at the same time, heats the oil in the core As the oil warms up and reaches its operating temperature, the bellows of the thermostat expand and closes the outlet from the bypass jacket The oil cooler flow control valve, located on the oil cooler, must now flow oil through the core of the oil cooler Reciprocating Engine Lubrication Systems 43  Oil Cooler Flow Control Valve No matter which path it takes through the cooler, the oil always flows over the bellows of the thermostatic valve As the name implies, this unit regulates the temperature by either cooling the oil or passing it on to the tank without cooling, depending on the temperature at which it leaves the engine Reciprocating Engine Lubrication Systems 44  Surge Protection Valves When oil in the system is congealed, the scavenger pump may build up a very high pressure in the oil return line To prevent this high pressure from bursting the oil cooler or blowing off the hose connections, some aircraft have surge protection valves in the engine lubrication systems One type of surge valve is incorporated in the oil cooler flow control valve; another type is a separate unit in the oil Reciprocating Engine return line Lubrication Systems 45 Reciprocating Engine Lubrication Systems Surge Protection Valves [Figure 6-12] surge protection valve 46 Reciprocating Engine Lubrication Systems Surge Protection Valves incorporated in a flow control valve is the more common type Although this flow control valve differs from the one just described, it is essentially the same except for the surge protection feature The high pressure operation condition is shown in Figure 6-12, in which the high oil pressure at the control valve inlet has forced the surge valve (C) upward Note how this movement has opened the surge valve and, at the same time, seated the poppet valve (E). 47 Reciprocating Engine Surge Protection Valves Lubrication Systems The closed poppet valve prevents oil from entering the cooler proper; therefore, the scavenge oil passes directly to the tank through outlet (A) without passing through either the cooler bypass jacket or the core. When the pressure drops to a safe value, the spring forces the surge and poppet valves downward, closing the surge valve (C) and opening the poppet valve (E). Oil then passes from the control valve inlet (D), through the open poppet valve, and into the bypass jacket (F). 48  Surge Protection Valves The thermostatic valve, according to oil temperature, determines oil flow either through the bypass jacket to port (H) or through the core to port (G). The check valve (B) opens to allow the oil to reach the tank return line Reciprocating Engine Lubrication Systems 49 Reciprocating Airflow Controls By regulating the airflow through the cooler, the temperature Engine of the oil can be controlled to fit various operating conditions For example, the oil reaches operating temperature more Lubrication quickly if the airflow is cut off during engine warm-up Systems There are two methods in general use: shutters installed on the rear of the oil cooler, and a flap on the air-exit duct In some cases, the oil cooler air-exit flap is opened manually and closed by a linkage attached to a cockpit lever. More often, the flap is opened and closed by an electric motor https://youtu.be/XgssShifyS8 https://www.youtube.com/watch?v=cWDCXFwPLIs https://www.youtube.com/watch?v=vOU6RvNhBeM 50  Dry Sump Lubrication System Operation The following lubrication system is typical of those on small, single-engine aircraft The oil system and components are those used to lubricate a 225 horsepower (hp) six- cylinder, horizontally opposed, air-cooled engine In a typical dry sump pressure-lubrication system, a mechanical pump supplies oil under pressure to the bearings throughout the Reciprocating Engine engine Lubrication Systems 51 Reciprocating Engine Lubrication Systems Dry Sump Lubrication System Operation [Figure 6-4] The oil flows into the inlet or suction side of the oil pump through a suction screen and a line connected to the external tank at a point higher than the bottom of the oil sump This prevents sediment that falls into the sump from being drawn into the pump The tank outlet is higher than the pump inlet, so gravity can assist the flow into the pump 52 Reciprocating Engine Lubrication Systems Dry Sump Lubrication System Operation The engine-driven, positive- displacement, gear-type pump forces the oil into the full flow filter [Figure 6-6] 53 Reciprocating Engine Dry Sump Lubrication System Lubrication Systems Operation The oil either passes through the filter under normal conditions or, if the filter were to become clogged, the filter bypass valve would open as mentioned earlier In the bypass position, the oil would not be filtered As seen in Figure 6-6, the regulating (relief) valve senses when system pressure is reached and opens enough to bypass oil to the inlet side of the oil pump. 54 Reciprocating Engine 55 Lubrication Systems Dry Sump Lubrication System Operation Then, the oil flows into a manifold that distributes the oil through drilled passages to the crankshaft bearings and other bearings throughout the engine. Oil flows from the main bearings through holes drilled in the crankshaft to the lower connecting rod bearings. [Figure 6-15] Reciprocating Engine Lubrication Systems Dry Sump Lubrication System Operation Oil reaches a hollow camshaft (in an inline or opposed engine), or a cam plate or cam drum (in a radial engine), 56 through a connection with the end bearing or the main oil manifold; it then flows out to the various camshaft, cam drum, or cam plate bearings and the cams. Reciprocating Engine 57 Lubrication Systems Dry Sump Lubrication System Operation The engine cylinder surfaces receive oil sprayed from the crankshaft and also from the crankpin bearings Since oil seeps slowly through the small crankpin clearances before it is sprayed on the cylinder walls, considerable time is required for enough oil to reach the cylinder walls, especially on a cold day when the oil flow is more sluggish This is one of the chief reasons for using modern multiviscosity oils that flow well at low temperatures Reciprocating Engine 58 Lubrication Systems Dry Sump Lubrication System Operation When the circulating oil has performed its function of lubricating and cooling the moving parts of the engine, it drains into the sumps in the lowest parts of the engine Oil collected in these sumps is picked up by gear or gerotor- type scavenger pumps as quickly as it accumulates These pumps have a greater capacity than the pressure pump. This is needed because the volume of the oil has generally increased due to foaming (mixing with air) On dry sump engines, this oil leaves the engine, passes through the oil cooler, and returns to the supply tank https://www.youtube.com/watch?v=Rt_AWy4tsN0 Reciprocating Engine Lubrication Systems gerotor-type scavenger pump 59  Dry Sump Lubrication System Operation Reciprocating Engine A thermostat attached to the oil cooler controls oil Lubrication Systems temperature by allowing part of the oil to flow through the cooler and part to flow directly into the oil supply tank This arrangement allows hot engine oil with a temperature still below 65 °C (150 °F) to mix with the cold uncirculated oil in the tank This raises the complete engine oil supply to operating temperature in a 60 shorter period of time Reciprocating Engine Lubrication Systems Wet-Sump Lubrication System Operation A simple form of a wet- sump system is shown in Figure 6-16 61 Reciprocating Engine Lubrication Systems Wet-Sump Lubrication System Operation The system consists of a sump or pan in which the oil supply is contained The oil supply is limited by the sump (oil pan) capacity The level (quantity) of oil is indicated or measured by a vertical rod that protrudes into the oil from an elevated hole on top of the crankcase In the bottom of the sump (oil pan) is a screen strainer having a suitable mesh, or series of openings, to strain undesirable particles from the oil and yet pass sufficient quantity to the inlet or (suction) side of the oil pressure pump 62 Reciprocating Engine Lubrication Systems Wet-Sump Lubrication System Operation Figure 6-17 shows a typical oil sump that has the intake tube running through it This preheats the fuel-air mixture before it enters the cylinders 63  Wet-Sump Lubrication System Operation Reciprocating The parts oiled by pressure throw a lubricating Engine spray into the cylinder and piston assemblies Lubrication After lubricating the various units it sprays, the Systems oil drains back into the sump and the cycle is repeated The system is not readily adaptable to inverted flying since the entire oil supply floods the engine https://www.youtube.com/watch?v=cWDCXFwPLIs 64 The End 65