Charles Raymond Matz

Influence of High Fogging Systems on Gas Turbine Engine Operation and Performance

High fogging is a power augmentation device where water is sprayed upstream of the compressor inlet with higher mass flow than that which would be needed to saturate the intake air. The main focus of this paper is on applications of high fogging on the ALSTOM gas turbine engines of the family GT24/GT26. Engine operation and performance are illustrated based on test results obtained from four different engines that have meanwhile accumulated more than 12,000 operating hours (OH) in commercial operation with ALSTOMs ALFog® high fogging system. The effect of internal cooling (water evaporation inside the compressor) is investigated considering actual compressor boundaries matched within the complete engine. Changes in the secondary air system (SAS) and corresponding movement of the engine operating line have been taken into account. Power output gain as high as 7.1% was experimentally demonstrated for injected water mass fraction (f=m H2O /m air ) equal to 1% and considering internal cooling effects only. Higher figures can be obtained for operation at low ambient relative humidity and partial evaporation upstream of the compressor inlet.

Prediction of Evaporative Effects Within the Blading of an Industrial Axial Compressor

The results of a compressor flow-analysis code calibration study for estimating the effects of water evaporation within the blade rows of industrial axial compressors are presented. In this study, a mean-line code was chosen for the calibration tool due to its accepted use during preliminary design studies, at which time during the compressor design process one would logically consider power augmentation through wet compression. The calibrated code features a nonequilibrium thermodynamic single-droplet evaporation model augmented with an empirical splashing model, which, as input, uses measurements of droplet spectra data taken on water injection nozzles in an intake rig configured with realistic length scales. In addition, a wetted-airfoil-surface flow-angle deviation model is applied to predict changes in compressor stage characteristics, which, in turn, affect the inlet mass flow of the compressor. The test vehicle for calibration was a 50 Hz Alstom industrial gas turbine. Once calibrated, the code was successfully utilized to predict wet-compression effects for three additional like-family Alstom gas turbines operating at constant speed while under full load. The effects modeled by the code include bleed supply pressure suck-down and bleed temperature cool-down effects, as well as compressor inlet mass flow and power consumption effects.