Abstract: A turbine blade having a labyrinth of internal channels for circulation of coolant received through an inlet formed in a terminal portion of a blade root. A labyrinth geometry includes: (i) the inlet arranged on an axially upstream face of the terminal portion leading to an upstream duct portion having a first section adjacent the inlet and a second section having a reduced cross-section compared to the first section, (ii) a leading edge passage intersecting with the first section and extending through a blade body towards a tip of the blade, where a proximal end of the leading edge passage is angled towards a direction of incoming air flow, (iii) a main blade passage intersecting with a downstream duct portion arranged in axial alignment with, and separate from, the upstream duct portion, and (iv) a restrictor passage intersecting with a mid-blade passage and extending towards a mid-blade duct portion.

Abstract: A turbine blade has a labyrinth of internal channels for circulation of coolant received through inlet integrally formed in terminal portion of blade root, novel labyrinth geometry includes; inlet arranged on axially upstream face of terminal portion leading to upstream duct portion having a first section adjacent the inlet and second section, second section having reduced cross section compared to first section; leading edge passage intersecting first section and extending through blade body towards tip of blade, proximal end of leading edge passage being angled, in use, towards direction of incoming air flow; main blade passage intersecting downstream duct portion, downstream duct portion arranged in axial alignment with upstream duct portion but separate from upstream duct portion; and restrictor passage intersecting with mid-blade passage and extending towards mid-blade duct portion, mid-blade duct portion in axial alignment with upstream and downstream duct portions and in fluid communication with upstre