Discussion of Some Myths/Features Associated With Gas Turbine Inlet Fogging and Wet Compression

Abstract

Gas turbine inlet fogging and overspray (high-fogging) have been considered the most cost-effective means of boosting a gas turbine's total power output, especially under hot or dry weather conditions. The result of employing fogging or overspray is indisputably clear − total power output is increased; however, development of the theory and explanation of the phenomena associated with fogging and overspray are not always consistent and are sometimes misleading and incorrect. This paper focuses on reviewing several interesting features and commonly discussed topics, including (a) entropy production of water evaporation, (b) the effect of centrifugal force on water droplets, and (c) whether water droplets can survive the journey in the compressor and enter the combustor. Furthermore, three turbine myths: that fogging/overspray increases the air density in the compressor, reduces the compressor power consumption, and noticeably enhances the gas turbine efficiency, are examined and discussed.Some common mistakes in describing the compressor work are identified and corrected. A newly constructed multiphase T-S diagram is used to explain the physics of water droplet evaporation process and corresponding entropy production during wet compression.

Influence of wet compression on aerodynamic performance and stability boundary of transonic compressor

“…However, maybe due to the ambiguous description of the comparative conditions or incorrect concepts, there are misleading views on part of the theoretical description and physical explanation of the wet compression phenomenon. 24 For example, many documents mentioned that “wet compression can reduce compressor power consumption,” but, through further theoretical analysis, Wang et al 24 pointed out that this conclusion was not always valid under different comparison conditions of dry and wet compression. Therefore, a more in-depth and clear understanding of the influence of wet compression on the compressor performance, especially the power consumption, is needed.…”