Gas Turbine Parameter Corrections

The various parameters appearing along an engine’s gas path, such as flows, pressures, temperatures, speeds, etc., vary not only with power condition but also with the ambient conditions at the engine’s inlet. Since a change in inlet temperature and/or pressure will contribute to an attendant change in a gas path parameter’s value, it would be difficult to characterize the aero-thermodynamic relationships between gas turbine engine parameters, (even at a constant engine operating point) unless the ambient conditions are somehow accounted for. This is usually accomplished through the use of corrected engine parameters. Although most of these corrections are well known by practitioners in the industry, knowledge of their origin does not appear to be as commonplace. The purpose of this paper is to fill that gap and furnish a summary of the commonly used corrections for the “major” gas path parameters that are used in performance analysis, diagnostics and control design, and to offer a derivation of these corrections. We will suggest both an analytic approach as well as an empirical approach. The latter can be used to establish the correction for parameters not directly addressed in this paper, as well as to fine tune the correction factors when actual engine data is available.