lm2500_lubevent

Lube System Vent

The gas generator is equipped with a sump vent system that collects the air/oil mixture from the bearing sumps and routes it to the accessory-gearbox-driven air/oil separator. The separated oil is scavenged from the air/oil separator while the air is discharged to the Purchaser-supplied vent piping at A12. The maximum oil consumption of the gas generator is 2.0 lb/hr; the average is 0.2 LB/hr.

Air/oil separator discharge from A12 is 0.25 pps of air/oil mixture at 350°F maximum at maximum power. The estimated flow at idle is 0.1 pps. Maximum allowable back pressure is 2.0 inches of water at core idle speed, increasing to a maximum of 36 inches of water at maximum power, as shown here.

The average air/oil mixture contains 3.8 × 106 to 1 air to oil vapor by volume. Piping from the air/oil separator must allow continuous drainage of any fluids that may collect in the line and must include a cleanable flame arrestor if discharged into the exhaust duct. The maximum allowable loads on the Air/oil separator connecting flange are: 300 LB shear, ±300 LB axial, and 345 in-LB bending moment.

Page 1 of 4Lubrication

19/11/2005http://inside-aep.ps.ge.com/insideaep/aep/iad/engine_prod_delv/idms/lm2500/09lubevent....

When negative pressure package ventilation system is utilized, the gas generator bearing sump oil seal pressure level is reduced because the aspiratorinlet pressure is reduced. The compressor rear frame vent pressure is also resuced. The sump vent pressure is not reduced, as it ultimately discharges to ambient through the exhaust or other systems. The differential pressure across the oil seals is therefore compromised; causing potential oil leakage at idle, and possible pressure reversal during engine load rejections and trips from high power. This pressure reversal can cause sudden oil vapor discharge from the compressor rear frame vents. The pressure reversal can be prevented by installing a Sump Evacuation System (SES) in the air/oil separator discharge line. The SES can reduce the internal sump pressure by 0.8 to 1.3 psi and thereby increase the seal pressure differential.

The SES consists of an electric motor driven pump installed in the air/oil separator discharge line, and is operated during low gas generator speed operation and during drop load transients. During normal operation above 9000 rpm gas generator speed the pump is turned off and the vent air simply flows through the pump.



The design requirements for such a system and pump are as follows:

z Temperature Capability = 350°F z Air / oil ratio = 3.8 × 106 to 1 z Maintain a flow rate of 100 cfm through gas generator speed range z Reduce its inlet pressure by 0.8 to 1.3 psi when operating z Maximum pressure drop when not operating not to exceed 0.3 psi z Electric motor driven

The pump should be operated during gas generator speeds of 1600 - 9000 rpm, whether motoring or operating, and during rapid deceleration as load rejections or emergency shutdowns. A recommended operating sequence for such a pump is shown below.





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lm2500_lubevent