Reasons for lubrication
Even if the engine was kept clean, ther will always be small amount of dirt that find their way inside. That dirt must be removed from the oil before it can damage the bearings or small oil passageways within the engine. The oil keeps the interior of the engine clean by carrying and contaniments in suspension in the lubricant to the oil filter, where they are removed
Even if the engine was kept clean, ther will always be small amount of dirt that find their way inside. That dirt must be removed from the oil before it can damage the bearings or small oil passageways within the engine. The oil keeps the interior of the engine clean by carrying and contaniments in suspension in the lubricant to the oil filter, where they are removed
The Pressure Relief Valve Lubricating system
This is situated in parallel with the oil pressure pump and it limits the pump outlet pressure by diverting any excess volume back to the inlet of the pump, thus controlling the flow of oil to the bearing chambers. The pressure relief valve maintains a constant pressure over the whole of the engine speed and oil temperature ranges. |
- The oil is drawn to the pressure pump through a suction filler which protects the pressure pump from damage.
- The oil pressure pump is contained within an oil pump pack and it contains one pressure pump and several scavenge pumps.
- Having several scavenge pumps ensures that the lubrication system remains a dry sump system.
- From the pressure pump oil is passed through the pressure filter which removes any small particles which may block the feed jets.
- The oil then flows to the pressure relief valve which maintains the oil pressure to the feed jets in the bearing chambers constant.
- The oil is passed to the feed jets through internal drillings and external oil pipes.
- The torque meter pump is used to boost engine oil pressure to a figure which is higher than normal system pressure.
- Oil eventually falls into collecting trays or compartments from where it makes it way to scavenge pumps. The scavenge pump push the oil through an air cooled oil cooler where the heat is dissipated into the atmosphere.
- Oil mist is vented via a centrifugal breather which is fitted and driven by the accessory gearbox.
The Full Flow Lubrication System
The full flow lubrication system achieves the required oil flow to the engine by allowing the oil pressure pump to supply the oil feed jets directly, without using a pressure relief valve
The full flow lubrication system achieves the required oil flow to the engine by allowing the oil pressure pump to supply the oil feed jets directly, without using a pressure relief valve
The Oil Tank
The oil tank is normally a separate unit mounted on the side of the engine, although it can be part of the engine intake, or even an integral part of the accessory drive unit. The oil tank must incorporate provision or filling, either by gravity and a pressure source. There must be a sight glass to determine contents of the tank. A de-aerator tray removes air bubbles from the oil as it flows back into the tank.
The oil tank is normally a separate unit mounted on the side of the engine, although it can be part of the engine intake, or even an integral part of the accessory drive unit. The oil tank must incorporate provision or filling, either by gravity and a pressure source. There must be a sight glass to determine contents of the tank. A de-aerator tray removes air bubbles from the oil as it flows back into the tank.
Oil Pumps
Gear type pumps, which consist of a pair of intermeshing steel gears located within a close fitting aluminium housing, are the normal method of delivering and retrieving oil in a circulatory system. When gears are rotated, oil is drawn into the pump, carried round by the teeth and delivered at the outlet. |
Oil Coolers
It can be either air cooled or fuel cooled, and some engine use both systems.
It can be either air cooled or fuel cooled, and some engine use both systems.
Centrifugal Breather
Oil mist escaping unhindered from the engine would rapidly deplete the engine oil contents and the oil mist is vented to the accessory drive unit where it must pass through the centrifugal breather before reaching the atmosphere. The centrifugal breather is rotated at high speed and as the oil mist enters, it is thrown outwards by centrifugal force. Around the inside periphery are de-aerator segments, the oil is separated from the air and is eventually flung back into the accessory drive unit to be picked up by a scavenge pump. The air makes its way out of the center of the rotating portion of the breather to atmosphere having had all the oil removed. Therefore, it minimises oil loss in the gas turbine engine Filters
Filters positioned within the lubrication system prevent debris and foreign matter from being continuously circulated around with the oil. |