Cast on-board injection nozzle with adjustable flow area

摘要

A Tangential On-Board Injection (TOBI) nozzle or a Radial On-Board Injection (ROBI) nozzle with adjustable flow area in a gas turbine engine for directing a cooling air flow into a rotor assembly of the turbine is disclosed. The TOBI or ROBI nozzle is a unitary cast structure including a plurality of tangentially angled cooling air passages, a number of the passages being cast-closed. After a flow test is conducted using the TOBI or ROBI nozzle, one or more of the cast-closed passages may be selectively machined open if the mass flow of the TOBI or ROBI nozzle does not satisfy the design point. Therefore, the structure of the TOBI or ROBI nozzle is easily fabricated using a casting process with low manufacturing costs while the optimum cooling air flow is achieved by adjusting the total flow area of the TOBI or ROBI nozzle before it is installed to the gas turbine engine. Furthermore, the TOBI or ROBI nozzle is advantageously supported in a cantilevered manner to avoid the thermal stress caused by temperature differential. The adjustable flow area feature also enables the TOBI or ROBI nozzle to be broadly used in different types of engines, the required mass flow of which are various.