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	Functional schematic of radial flow gas turbine (side and top views)

An auxiliary power turbine mounted on the ring gear of a planetary gearbox allows for high-efficiency variable-speed power transmission from a single-shaft gas turbine. This allows the single-shaft gas turbine to drive, with high efficiency, variable speed devices such as:

• Centrifugal compressors

• Centrifugal pumps

• Centrifugal blowers

Advantages of the Variable Speed Turbine

• Optimized variable speed shaft output from single shaft gas turbines

• Higher efficiency at low off-design speeds than conventional two-shaft gas turbines

• Mountable with small modifications on existing gas turbine designs

Description of the Variable Speed Turbine

A planetary gearbox with turbine blades mounted on the ring gear and variable guide vanes is located upstream of the turbine blades and downstream of the exhaust of a single-shaft gas turbine. The single-shaft gas turbine shaft directly drives the planetary gearbox sun gear with the majority of the gas turbine's torque transmitted directly through the sun gear to the variable speed output shaft (mounted to the planet gears).

The planetary gearbox ring speed is controlled by adjusting the flow angle through the variable guide valves onto the turbine blades, thus accelerating or decelerating the ring and planet gear speeds. Variable output speed from a fixed-speed gas turbine is achieved, minimizing the power losses at off-design speed that are typically experienced with conventional two-shaft gas turbines.

	Variable speed turbine

Function of the Variable Speed Turbine

• 75 to 90 percent of the gas turbine power is directly transmitted through the planetary gearbox.

• The remaining power from the gas turbine is employed to drive the speed control power turbine, which is mounted on the ring gear.

• The speed of the ring gear and the output shaft is controlled by adjusting the planetary gear-mounted power turbine's variable inlet guide vanes.

• The driven equipment speed, mounted on the planetary gearbox output shaft (connected to the planet gears) is adjustable through control of the variable guide vanes.

Southwest Research Institute (SwRI) can offer you a full range of capabilities and experience in gas turbine technology including becoming an extension of your engineering department. For more information about our radial flow gas turbine capabilities, or how you can contract with SwRI, please contact Klaus Brun, Ph.D., at kbrun@swri.org or (210) 522-5449.

gasturbine.swri.org

| Fluids and Machinery Engineering Department | Mechanical Engineering Division | SwRI Home |

Southwest Research Institute^® (SwRI^®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

January 03, 2013