Effect of T56 preswirl cooling modelling on disc assembly temperature prediction

Abstract

The T56 Series III 1st stage rotor blade is cooled using moderately preswirled air from 36 preswirl injection nozzles. The amount of swirl achieved by discrete preswirl coolant jets is generally unknown, due to mixing losses. A “frozenrotor” CFD analysis was therefore performed on a sector of the NGV support plate/1st stage rotor disc cavity of the T56 turboprop engine, including a preswirl injection hole and a section of the upstream plenum. It was found for this geometry that the mean tangential velocity of the coolant in the preswirl region of the rotor-stator cavity was about half the maximum tangential velocity in the preswirl jets (C mean/C maxjet = 0.5). This value was used in ICP, a one-dimensional coolant flow network program, to model coolant flow in the disc cavities. ICP was then iterated with the disc assembly conduction code DCOOL to obtain the temperature distribution in the disc assembly. The result was compared with the resultant temperature distribution for a C mean/C maxjet value of unity. The temperature distribution in most of the 1st disc remained largely insensitive to the value of C mean/C maxjet, showing the spacer to play a greater role in heat conduction to the disc than the blade shanks