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Lycoming T53-L-13B Turboshaft
The Lycoming T53-L-13 is a fairly large and powerful free turbine turboshaft engine, primarily used for helicopters. The T53 engine made its debut as the T53-L-1 in the venerable Bell UH-1 Iroquois Helicopter, aka The Huey. There have been numerous improvements of the T53, culminating in the latest version, the T53-L-703, with 1,800 shaft horsepower. The engine that will be discussed here is the prior version, the T53-L-13, because of its relative low cost, availability, and popularity among turbine enthusiasts for alternative projects such as turbine powered boats.
The T53-L-13 is a relatively compact free shaft turbine engine with a mixed flow compressor, a reverse flow combustor, and a multi-stage turbine for compressor drive, as well as a multi-stage free turbine for load. The engine contains an integral reduction gearbox on the cold end to drive the load. Power rating is 1,400 horsepower, and engine output speed is 6,640 rpm.
At the very front of the engine is the compact output reduction gearbox, which drives the load as well as the N2 governor, the N2 tach generator, and a torquemeter. Intake air flows around this gearbox, past variable geometry inlet guide vanes, and into the five stage axial, single stage centrifugal mixed flow compressor. Air is bled from the fourth and fifth compressor stages to improve acceleration, as well as to provide anti-icing and customer air. The variable inlet guide vanes also provide stall margin control to improve acceleration. The compressor discharge air is fed to a reverse flow annular burner with 22 fuel nozzles. The high pressure gas is expanded through a two stage axial high pressure turbine, to drive the compressor and the accessory gearbox, and then the gas is expanded through a two stage axial free power turbine, which drives the output reduction gearbox through a coaxial shaft, which rides through the center of the high pressure shaft towards the front of the engine. The output reduction gearbox converts the 22,500 rpm power turbine speed down to 6,640 rpm, while multiplying torque by a factor of 3 and a half. Theoretical peak torque for this engine is on the order of 2,200 lb/ft, though it is gearbox limited to around 1,700 lb/ft. The engine exhaust escapes through a large diameter diffuser at the rear of the engine. Accessories include fuel pumps, oil pumps, starter/generator, and a hydromechanical fuel controller.
Lycoming T53-L-13B Turboshaft Engine
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