Abstract
The presence of injectors with strongly swirled flows, used to promote flame stability in the combustion chambers of gas turbines, influences the behaviour of the effusion cooling jets and consequently of the liner’s cooling capabilities. For this reason, unsteady behaviour of the jets in the presence of swirling flow requires a characterization by means of experimental flow field analyses. The experimental setup of this work consists of a non-reactive single-sector linear combustor test rig, scaled up with respect to the real engine geometry to increase spatial resolution and to reduce the frequencies of the unsteadiness. It is equipped with a radial swirler and multi-perforated effusion plates to simulate the liner cooling system. Two effusion plates were tested and compared: with cylindrical and with laid-back fan-shaped 7-7-7 holes in staggered arrangement. Time resolved Particle Image Velocimetry has been carried out: the unsteady characteristics of the jets, promoted by the intermittent interactions with the turbulent mainstream, have been investigated as their vortex structures and turbulent decay. The results demonstrate how an unsteady analysis is necessary to provide a complete characterization of the coolant behaviour and of its turbulent mixing with mainflow, which affect, in turn, the film cooling capability and liner’s lifetime.
Highlights
In modern gas turbine combustors, highly swirling flow structures are used to promote the fuel-air mixing and to provide stable flames
The image in the top refers to the flow field on the meridian plane while the bottom one to the plane parallel to the dome
The zy plane, that is placed at the leading edge of the first row of holes, give information of the flow field immediately upstream of the coolant injection
Summary
In modern gas turbine combustors, highly swirling flow structures are used to promote the fuel-air mixing and to provide stable flames. As a direct consequence of this, understanding the effects of the swirling flow on near-wall flow field is fundamental in order to support the development better effective cooling schemes and improve combustors durability. One of the most promising cooling technology for liners is the so-called effusion technique that allows high cooling effectiveness, due to both the formation of a cold air layer between walls and hot gases and the production of a strong heat sink effect. Fundamental experimental studies on cylindrical and shaped holes were proposed by several authors [2,3,4,5] with the final aim of measuring flow field with non intrusive laser diagnostics, typically developing test rigs with axial and uniform main flow. With the aim of reproducing similar conditions to those present in the combustion chambers, several authors proposed
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