The oil should fall below a critical mark. Before starting a vehicle particularly for a long journey. The oil level must be checked. An oil pressure gauge is mounted on the instrument panel of all cars equipped with a pressure lubricating system to tell the driver what the oil pressure is in the engine.
The oil pressure gauges are of the following types:. Fig shows pressure expansion type oil pressure gauge. It contains hollow bourdon curved tube, that is fastened at one end and free at the other. The oil pressure is applied to the curved tube through an oil line from the engine which causes the tube to straightened out. This movement is transmitted to a needle by linkage and gears from the end of the tube. The needle moves across the face of the dial indicating the oil pressure.
The engine unit consists of a moving contact that moves over a resistance according to the varying oil pressure against a diaphragm. As the pressure increases, the diaphragm moves inward by which the contact moves along the resistance so that more resistance is placed in the circuit between the engine and indicating unit.
This reduces the amount of current flowing in the circuit. The indicating unit consists of two coils that balance the movement of the pointer on a scale, in a manner similar to the electrically operated fuel gauge.
The metal thermostat type oil pressure indicator is similar to the bimetal thermostat furl gauge. It consists of an engine unit and a dash unit. The oil pressure on a diaphragm distorts the engine unit thermostat blade, and this distortion produces a similar distortion in the dash unit thermostat blade, causing the oil pressure to indicate on the dial. In many motor vehicles, the engine oil pressure is indicated by a warning light.
The light comes when the ignition switch is turned on and the oil pressure is low. The circuit user four-stage diaphragm switch which operates a warning a lamp according to the oil pressure required for different engine feeds. Fig shows an oil pressure warning lamp with a four-stage diaphragm operated switch. When the oil exerts pressure on the diaphragm the projection attached to it presses the uppermost contact bar, breaking the contact between the two projection further movement of the diaphragm deflects the second bar, and so on up to the fourth stage.
Each of these four stages is brought into a circuit with the warning lamp by a selector switch operated in conjunction with the speed-o-meter. In this way, the warning lights up only when the oil pressure falls below the value corresponding to the minimum engine speed. Email Address. Saif M. He completed his engineering studies in and is currently working in a large firm as Mechanical Engineer.
He is also an author and editor at www. Notify me of follow-up comments by email. Notify me of new posts by email. This site uses Akismet to reduce spam. Learn how your comment data is processed. Contents show. Parts of Lubrication System. Oil Sump. Oil Pump 3. Gear Pump. Rotor Pump. Plunger Pump. Vane Pump. Oil Filter 4. By-pass system. Full flow system. Cartridge type oil filter. Edge type oil filter. Some incorporate a pressurized oil tank. This ensures a constant head pressure to the pressure-lubrication pump to prevent pump cavitation at high altitude.
Oil consumption in a gas turbine engine is low compared to that in a reciprocating engine of equal power. Oil consumption on the turbine engine is affected by the efficiency of the seals. However, oil can be lost through internal leakage and on some engines by malfunction of the pressurizing or venting system.
Oil scaling is very important in a jet engine. Any wetting of the blades or vanes by oil vapor will encourage the accumulation of dust and dirt. A dirty blade or vane represents high friction-to-airflow. This decreases engine efficiency, and results in a noticeable decrease in thrust or increase in fuel consumption. Since oil consumption is so low, oil tanks can be made relatively small.
This causes a decrease in weight and storage problems. System pressures may vary from 15 psig at idle to psig during cold starts.
Normal operating pressures and bulk temperatures are about 50 to psig and oF, respectively. GENERAL In general, the parts to be lubricated and cooled include the main bearings and accessory drive gears and the propeller gearing in the turboprop. This represents again in gas turbine engine lubrication simplicity over the complex oil system of the reciprocating engine.
The main rotating unit can be carried by only a few bearings. In a piston power plant there are hundreds more moving parts to be lubricated. Because each bearing in the engine receives its oil from a metered or calibrated orifice, the system is generally known as the calibrated type. With a few exceptions the lubricating system used on the modem turbine engine is of the dry-sump variety.
However, some turbine engines are equipped with a combination dry- and wet-type lubrication system. Wet-sump engines store the lubricating oil in the engine proper. Although this chapter addresses dry-sump systems, an example of the wet-sump design can be seen in the Solar International T engine. In this engine the oil reservoir is an integral part of the accessory-drive gear case.
An example of a combination dry-and wet-sump lubrication can be found in the Lycoming Tseries engines. With this type of system, a larger oil supply can be carried and the oil temperature can be controlled An oil cooler usually is included in a dry-sump oil system Figure 5-l.
This cooler may be air-cooled or fuel-cooled. The dry-sump oil system allows the axial-flow engines to retain their comparatively small diameter.
This is done by designing the oil tank and the oil cooler to conform to the design of the engine. The following component descriptions include most of those found in the various turbine lubrication systems.
However, not all of these components will be found in any one system. The dry-sump systems use an oil tank which contains most of the oil supply. However, a small sump usually is included on the engine to hold a supply of oil for an emergency system. A typical oil tank is shown in Figure It is designed to furnish a constant supply of oil to the engine. This is done by a swivel outlet assembly mounted inside -the tank a horizontal baffle mounted in the center of the tank, two flapper check valves mounted on the baffle, and a positive-vent system.
The swivel outlet fitting is controlled by a weighted end, which is free to swing below the baffle. The flapper valves in the baffle are normally open. They close only when the oil in the bottom of the tank rushes to the top of the tank during deceleration.
This traps the oil in the bottom of the tank where it is picked up by the swivel fitting A sump drain is located in the bottom of the tank. The airspace is vented at all times. All oil tanks have expansion space. This allows for oil expansion after heat is absorbed from the bearings and gears and after the oil foams after circulating through the system.
Some tanks also incorporate a deaerator tray. The tray separates air from the oil returned to the top of the tank by the scavenger system. The air released is carried out through the vent system in the top of the tank. Inmost oil tanks a pressure buildup is desired within the tank. This assures a positive flow of oil to the oil pump inlet. This pressure buildup is made possible by running the vent line through an adjustable check-relief valve. The check-relief valve normally is set to relieve at about 4 psi pressure on the oil pump inlet.
There is little need for an oil-dilution system. If the air temperature is abnorrnally low, the oil may be changed to a lighter grade. Some engines may provide for the installation of an immersion-type oil heater. Because only a few models of centrifugal-flow engines are in operation, there are few engines using a wet-sump type of oil system.
The components of a wet-sump system are similar to many of a dry-sump system. The oil reservoir location is the major difference. The reservoir for the wet-sump oil system may be the accessory gear case, which consists of the accessory gear casing and the front compressor bearing support casing. Or it may be a sump mounted on the bottom of the accessory case. Regardless of configuration reservoirs for wet-sump systems are an integral part of the engine and contain the bulk of the engine oil supply.
These strainers aid the main oil strainer. This plug should always be examined closely during inspections. The presence of metal particles may indicate gear or bearing failure. This system is typical of all engines using a wet-sump lubrication system. The bearing and drive gears in the accessory drive casing are lubricated by a splash system. The oil for the remaining points of lubrication leaves the pump under pressure.
It passes through a filter to jet nozzles that direct the oil into the rotor bearings and couplings. Most wet-sump pressure systems are variable-pressure systems in which the pump outlet pressure depends on the engine RPM. The scavenged oil is returned to the reservoir sump by gravity and pump suction.
Oil from the turbine coupling and the remaining rotor shaft bearings drains into a sump. The oil is then pumped by the scavenge element through a finger screen into the reservoir. Not all of the units will be found in the oil system of any one engine. But a majority of the parts listed will be found in most engines.
Oil Tanks Tanks can be either an airframe or engine-manufacturer-supplied unit. Usually constructed of welded sheet aluminum or steel, it provides a storage place for the oil. In most engines the tank is pressurized to ensure a constant supply of oil to the pressure pump.
Pressure Pumps Both gear- and Gerotor-type pumps are used in the lubricating system of the turbine engine. The gear-type pump consists of a driving and a driven gear. The engine-accessory section drives the rotation of the pump. Rotation causes the oil to pass around the outside of the gears in pockets formed by the gear teeth and the pump casing. The pressure developed is proportional to engine RPM up to the time the relief valve opens.
The relief valve may be located in the pump housing or elsewhere in the pressure system for both types of pumps. The Gerotor pump has two moving parts: an inner-toothed element meshing with an outer- toothed element. The inner element has one less tooth than the outer. The missing tooth provides a chamber to move the fluid from the intake to the discharge port. Both elements are mounted eccentrically to one another on the same shaft. Scavenger Pumps These pumps are similar to the pressure pumps but have a much larger total capacity.
An engine is generally provided with several scavenger pumps to drain oil from various parts of the engine. Often one or two of the scavenger elements are incorporated in the same housing as the pressure pump Figure Different capacities can be provided for each system despite the common driving shaft speed.
This is accomplished by varying the diameter or thickness of the gears to vary the volume of the tooth chamber. A vane-type pump may sometimes be used. Oil Filters and Screens or Strainers To prevent foreign matter from reaching internal parts of the engine, filters and screens or stainers are provided in the engine lubricating system. The three basic types of oil filters for the jet engine are the cartridge screen-disc and screen Figures , and The cartridge filter is most commonly used and must be replaced periodically.
The other two can be cleaned and reused. Each filter is comprised of two layers of mesh forming a chamber between mesh layers. The filters are mounted on a common tube and arranged to provide a space between each circular element. Lube oil passes through the circular mesh elements and into the chamber between the two layers of mesh. This chamber is ported to the center of a common tube which directs oil out of the filter. Screens or strainers are placed at pressure oil inlets to bearings in the engine.
This aids in preventing foreign matter from reaching the bearings. To allow for oil flow in the event of filter blockage, all filters incorporate a bypass or relief valve as part of the filter or in the oil passages. When the pressure differential reaches a specified value about 15 to 20 psi , the valve opens and allows oil to bypass the filter.
Some filters incorporate a check valve. This prevents reverse flow or flow through the system when the engine is stopped Filtering characteristics vary, but most filters will stop particles of approximately 50 microns.
Magnetic Chip Detector One or more magnetic chip detectors are installed on gas turbine engines. They are used to detect and attract ferrous material metal with iron as its basic element which may come from inside the engine. This ferrous material builds up until it bridges a gap. Whenever there is a requirement, the chip detectors may be collected and analyzed to determine the condition of the engine.
Most engines utilize an electrical chip detector, located in the scavenger pump housing or in the accessory gearbox. Should the engine oil become contaminated with metal particles, the detector will catch some of them.
This causes the warning light on the caution panel to come on. Tubing, Hose, and Fittings Tubing, hose, and fittings are used throughout the lubricating system.
Their purpose is to connect apart into a system or to connect one part to another to complete a system. Oil-Pressure-Low Caution Light Most gas turbine engine lubricating systems incorporate an engine oil-pressure-low caution light warning device into the system for safety purposes. The light is connected to a low- pressure switch.
When pressure drops below a safe limit, the switch closes an electrical circuit causing the caution light to burn. Power is supplied by the volt DC system. Oil Temperature Indicating System In a typical engine oil temperature indicating system, the indicator is connected to and receives temperature indications from an electrical resistance-type thermocouple or thermobulb.
These are located in the pressure pump oil inlet side to the engine. Power to operate this circuit is supplied by the volt DC system. Oil Coolers The oil cooler is used to reduce oil temperature by transmitting heat from the oil to another fluid usually fuel.
Since the fuel flow through the cooler is much greater than the oil flow, the fuel is able to absorb a considerable amount of heat. This reduces the size and weight of the cooler. Thermostatic or pressure-sensitive valves control the oil temperature by determining whether the oil passes through or bypasses the cooler. The piston and piston rings cylinder walls, tappet rollers lubricated by oil spray from around the piston pins, and the main and connecting rod bearings.
A dry sump lubricating system is used for the supply of oil and is carried out in an external tank. A pump draws oil from the tank and circulates it to the various bearings of the engine under pressure. Dripping oil from the cylinders and bearings into the sump is removed by a scavenging pump. So, oil is prevented from accumulating from the base of the engine.
The capacity of the oil pump is always less than the scavenging pump. A filter with a bypass valve is placed in between the supply tank and scavenge pump in this system. The pressure relief valve opens permitting oil to by-pass the filter and reaches the supply tank when the filter is clogged.
To remove heat from the oil, separate oil cooler with either water or air as the cooling medium is provided in the dry-sump system. I hope you liked the article of Lubrication System If so do read another article I have covered. Till then Thank you so much we will meet in other articles. Overview: Google Patent Lubrication. Amardeep will share information related to Mechanical Engineering in this platform.
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