Tham khảo tài liệu 'operation, maintenance and repair of auxiliary generators episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | TM 5-685 NAVFAC MO-912 COOLING AIR HOLES INSERT COVER FRONT INSERT TRAILING EDGE DIMPLES TRAILING EDGE SLOTS NOSE HOLES Figure 3-26. Turbine vane cooling air flow. 4 Scavenging. Scavenging is accomplished by a multi-element lubrication and scavenge pump. One element is used for pumping. The other elements are used for forward and aft scavenging of the B-sump and C-sump. Oil in the A-sump drains by gravity into the accessory gearbox. 5 Venting. Some lubrication systems are vented. To maintain high differential pressure across the carbon seals to prevent oil leakage a high sump vent capacity is required. The A and C sumps vent through the engine output shaft and vent collector to ambient. The B-sump vents to the turbine exhaust gas stream. 3-19. Starting system. Gas turbine engine starters must be capable of rotating an engine up to a speed-at which it becomes self-sustaining. The starter must provide sufficient torque to accelerate the engine from a standstill to a self-sustaining speed within a specified time. Although it must continue to assist the engine in accelerating up to a predetermined speed. a. Electric motor. An electric starter motor is usually used for a gas turbine engine in service as an auxiliary generator prime mover. The starter rotates the engine compressor shaft via the gear train in the accessory gearbox. In most installations the starter can be energized either automatically or manually. b. Fuel. As the engine is accelerated by the starter fuel is supplied when a specified rotational speed is attained. When this speed is attained the compressor and engine-driven fuel pump will deliver sufficient air and fuel respectively to the combustion chamber to sustain satisfactory combustion. c. Ignition system. An ignition system consisting of an ignition exciter igniter plug lead assemblies and igniter plugs is required. Fuel ignition is ensured by one or two igniter plugs connected to the exciter by the separate igniter leads. The plugs are located in
