Variable-pitch nozzle for a radial turbine, in particular for an auxiliary power source turbine

Abstract

A radial turbine nozzle of a turbine engine rotating about a central axis includes a first annular array of fixed blades and a second annular array with a same number of variable-pitch blades. The blades have pressure and suction surfaces. Each variable-pitch blade is connected to cups and is configured to be rotated by a controller about a geometric axis connecting centers of the cups. Each variable-pitch blade is mounted at a distance from the axis of the cups such that this axis of rotation is positioned facing the suction surface of the blade and substantially closer to a trailing edge than to a leading edge of that blade. The nozzle can modify the reduced flow admitted by a radial turbine in accordance with requirements of a thermodynamic cycle and produce a seal in an area of maximum load of the nozzle blades.

Description

TECHNICAL FIELD[0001]The invention relates to a variable-pitch radial turbine nozzle and particularly, but not exclusively, a nozzle for a turboshaft engine or auxiliary power source turbine.[0002]The field of the invention is that of gas distribution in the turbines of turbine engines and, particularly, adapting fluid flow to reduce fuel consumption, particularly specific fuel consumption (abbreviated to Cs) under partial load, and improving the operability of engines, particularly turboshaft engines or auxiliary power units (abbreviated to APUs). The term turbine engine refers to turboshaft engines, APU-type units and turbochargers.[0003]An APU is an energy source that makes it possible, for instance, to start the main engines of aircraft and provide non-propulsive power (cabin pressurisation power, electrical and / or hydraulic power). Some secure APUs can also act while in flight, in the case of engine failure, to attempt to restart the engine and / or to provide power to equipment....

AI Technical Summary

Benefits of technology

The invention proposes to improve the mechanical strength and overall efficiency of a turboshaft engine by using a nozzle with variable-pitch blades to regulate gas flow rate and control air incidence. A seal is produced between the nozzle blades and their spacing system to limit unwanted gap flows in the area where they would be most intense. The blade pitch control means matches the airflow demanded by the operating point with the flow passing into the turbine. Flexible fixed-pitch blades are also used to ensure the passage of structural loads and reduce play and misalignment between the cups and the casings, thereby improving performance.

Problems solved by technology

Adaptation such as this undoubtedly leads to a loss of efficiency and performance of the turbine taken in isolation—because of the reduction brought about by the matching process—but it does optimise the thermodynamic cycle of the turbine engine.

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