lm2500_lubesupply

Lube Supply

The LM2500 gas generator requires a supply of 18 gpm of MIL-L-23699 or MIL-L-7808 oil, or other approved lubricant shown in MID-TD-0000-6. Prior to starting the engine, the inlet to the lube pump shall have a flooded suction, but the pressure shall not exceed 3.5 psig. During starting with cold oil, the inlet pressure to the pump shall not be less than 5 psia. During normal operation with 140° to 160°F oil, the inlet pressure to the pump shall not be less than 12 psia. The oil flow varies with gas generator speed.

During starting and acceleration to idle, the temperature of the oil supply to the lube pump inlet must be above +20°F for MIL-L-23699 oil and above -20°F for MIL-L-7808 oil. This is required in order to assure an acceptable viscosity (700 cSt maximum) of the oil used to operate the compressor variable-stator control system. Subsequent transients above idle should be restricted until the oil supply temperature is at least 90°F in order to assure complete transient capability of the variable-stator control system.

The lube-supply element of the lube and scavenge pump is equipped with a pressure relief valve that has an initial cracking pressure of 100 psid and a full bypass flow set of 200 psid. The Purchaser-supplied components between the lube pump discharge port (Interface L2) and the lube supply manifold connection (L4) should therefore be rated for 200 psig minimum. The Purchaser-supplied piping and components should also be selected to ensure that the lube supply element does not operate on the relief valve except under a failure condition.

Lube and Scavenge Pump Interfaces.

Figure 1 defines the nominal lube supply pressure as measured at the pressure tap on the lube supply manifold (L5) for combinations of gas generator speed, lube supply temperature, oil type, and stator vane control configuration for MIL-L-23699 Oil. If the Purchaser plans to use MIL-L-7808, please contact GE for lube supply pressure characteristics. In addition, an allowance of 15 psid shall be made for the lube supply system check valve provided with the gas turbine.

The lube oil supply manifold is equipped with an antistatic leak check valve to prevent flooding of the

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gas turbine gearbox and sumps from an elevated lube supply system when the engine is not in operation.

The maximum static head pressure that can be applied by the Purchaser’s lube supply system to the lube supply manifold (L4) is 3.5 psig. Although the 3.5 psig maximum static head pressure is equivalent to a lube oil head of 8 feet, it is suggested that, where possible, the actual head imposed be limited to not more than 3 feet to further minimize potential for flooding the sumps in the event of malfunction or leakage through the antistatic leak check valve.

The oil supplied to the gas generator shall not contain more than 10% by volume of entrained air. The engine oil system will "gulp" approximately 4.5 gallons from the non-operating condition; therefore, the oil supply tank must be sized to accommodate this amount of oil.

A pressure tap is provided on the gas turbine, for determining the oil supply pressure to the bearings, and another in the oil scavenge line, for determining scavenge oil pressure. Sensors are provided in each of the scavenge oil lines and from the accessory gearbox for monitoring oil scavenge temperature.

During normal operation, the Purchaser’s oil temperature control system should regulate the oil supply temperature to the bearings between 140° and 160°F. The oil supplied to the bearings must be filtered to 10µ nominal. GE recommends the use of 10µ nominal filtration in both the lube supply and the scavenge system.

Figure 1. Nominal Lube Supply Pressure with MIL-L-23699 Oil.

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lm2500_lubesupply

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