Studies on Part Load Controlled Cooling Air Supplies in Stationary Gas Turbines

Abstract

The design of new stationary gas turbines and development of upgrades for existing respectively is facing challenges regarding part load operation. The demands for high overall efficiency and compliance with legal requirements depend on the design of cooling air circuits among others. The design of an optimized secondary air distribution at both base load and part load as well as the consideration of different ambient conditions requires conceptual studies and hence appropriate models. This paper introduces the holistic model of a literature based generic stationary gas turbine, which essentially couples a gas turbine performance synthesis model with a more detailed secondary air system (SAS) network model. Extended with additional models such as evaluation of blade and vane material temperatures T mat , it allows for comparative off design studies with uncontrolled and controlled turbine cooling air circuits. The presented studies here first focus on margins of T mat with base load condition as benchmark. The subsequent exploitation of these margins is limited by the fundamental requirements of hot gas ingestion at common rim seal configurations. Either way, the reduction of cooling air at part load is beneficial in terms of fuel flow reduction: vane cooling air control results in up to 0.12% of fuel flow reduction at part load operation.