Sealing of gas turbine disk cavities operating in the presence of mainstream external flow

Abstract

Abstract Improvements in internal air sealing systems lead to increases in the overall efficiency of gas turbines, by reducing the flow rate of high-pressure coolant required. This paper describes an experimental determination of mainstream external flow ingestion in gas turbine rotor–stator disk cavities. The performance of two geometries operating in the presence of a mainstream external flow field has been investigated: a simple rotor–stator geometry equipped with an axial rim seal, and a realistic rotor–stator geometry equipped with a double-toothed-rim (DTR) seal. Tests were conducted up to an external flow Reynolds number of 6×10 5 and a rotational Reynolds number of 1.5×10 6 . The sealing flow necessary to prevent ingress of external fluid into the disk cavity was determined using static pressure and gas concentration measurements. For the simple rotor–stator geometry, the values of minimum sealing flow rates necessary to prevent ingress are primarily governed by mainstream flow rate except at very low flow rates, where rotational speed effects are equally important. The sealing performance of the realistic rotor–stator geometry far exceeds that of the simple rotor–stator geometry in terms of both a minimum sealing flow rate needed to prevent ingress, and a sealing effectiveness parameter defined in this paper. This observation is consistent with the results formerly presented by the present authors for the same disk cavity and rim seal geometries but in the absence of mainstream external flow.