Simplified Mathematical Representations of Single Shaft Gas Turbines in Mechanical Drive Service

Abstract

There have been several recent applications of large single shaft, heavy duty gas turbines in mechanical drive service, powering high horsepower, multi-casing compressors. This variable speed application of a traditional constant speed driver, with a more limited operating speed range, has created a need for simplified but accurate mathematical representations that can be incorporated into overall process simulations to allow interactive dynamic evaluation of the complete system. This paper presents simplified mathematical representations of four gas turbines covering the horsepower range from 26,000 HP to 108,000 HP. The models incorporate both the control and fuel system characteristics as well as those of the turbomachinery. Although gas fuel is assumed, listed references can be used to accomodate liquid fuel. The models are suitable for a wide range of ambient temperatures, and the influence of axial flow compressor variable inlet guide vanes is included in the models as appropriate to the actual machinery configuration.