Handbook of Turbomachinery Second Edition Revised - Ventech!

Weight, cost, and complexity constraints
Considering that liner heat load is driven primarily by the flame radiation,
the calculation of the flame temperature and the heat flux through the liner
wall requires good understanding of the combustion process. A comprehensive
monograph by Lefebre [109] provides an excellent review of various
gas turbine combustor systems. It also details the calculation procedures for
the main factors that affect liner cooling.
Many early gas turbine combustors were a single- or multiple-can
design and required a transition between combustor exit and turbine inlet.
Liners for many of these combustors were assembled from a group of
cylindrical shells that formed a series of annular passages at the shell
intersection points. These passages created the louvers permitting a film of
cooling air to be injected along the hot side of the liner wall to provide a
protective thermal barrier. The annular gap heights were maintained by
simple ‘‘wiggle-strip’’ louvers (Fig. 27). Air metering was a major problem
with this technique. Application of splash-cooling devices provided control
of the cooling air entering the liner through a row of small-diameter holes
with air jets impinging on a cooling skirt, which deflected the air along the
inside of the liner wall. Annular combustors, which were introduced later,
originally also used wiggle-strip and splash-cooling configurations. Since
then, the ‘‘machined-ring’’ or ‘‘rolled-ring’’ approach, which features
accurately machined holes instead of louvers and combines accurate air-
Figure 27 Combustor liner cooling techniques.
Copyright © 2003 Marcel Dekker, Inc.