(57) A method of operating a "rich burn" combustion chamber (42) comprises supplying 10%
of the air through an inlet (52) in an upstream wall (48), supplying 64% to 80% of
the air for mixing and supplying 10% to 26% of the air for cooling at least one double
skin wall (44, 46) and the upstream wall (48). The method further comprises supplying
a first portion of the 64% to 80% of the air for mixing through mixing ports (58A,
58B, 62A, 62B) into the combustion chamber (42) and supplying a second portion of
the 64% to 80% of the air for mixing to provide convective cooling of the at least
one double skin wall (44, 46) before being supplied through additional mixing ports
(74A, 74B, 76A, 76B) into the combustion chamber (42) and supplying the 10% to 26%
of the air for cooling the at least one double skin wall (44, 46) and the upstream
wall (48) to provide convective cooling and/or effusion cooling of the at least one
double skin wall (44, 46) and the upstream wall (48). The amount of air available
for mixing is increased and engine emissions are reduced.
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