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research-article

INVESTIGATION ON THE EFFECT OF SURFACE WETTABILITY ON A TWO-PHASE FLOW IN A COMPRESSOR CASCADE

[+] Author and Article Information
Niklas Neupert

Laboratory for Tubomachinery, Helmut Schmidt University, D-22043 Hamburg, Germany
niklas.neupert@gmx.de

Janneck Christopher Harbeck

Laboratory for Tubomachinery, Helmut Schmidt University, D-22043 Hamburg, Germany
harbeck@hsu-hh.de

Franz Joos

Laboratory for Tubomachinery, Helmut Schmidt University, D-22043 Hamburg, Germany
joos@hsu-hh.de

1Corresponding author.

ASME doi:10.1115/1.4040180 History: Received September 14, 2017; Revised October 22, 2017

Abstract

In recent years overspray fogging has become a powerful means for power augmentation of industrial gas turbines. Despite the positive thermodynamic effect on the cycle droplets entering the compressor increase the risk of erosion and lead to a higher fouling sensitivity. Therefore erosion resistant hydrophobic coatings are applied to the first stages of compressors. Although some patents claim the use of such coatings the aerodynamic impact of a different wettability is not regarded so far. In this study the issue of a different blade surface wettability in a linear transonic compressor cascade is addressed. Different coatings are applied resulting in contact angles of 51-95?. The inflow Mach number was fixed at design inflow Mach number and the inflow angle was varied over a broad range. The effect on the water film pattern is analyzed in terms of position of film breakup, rivulet width and totally wetted surface. The performance of the cascade under two-phase flow was analyzed using LDA/PDA measurement technique in terms of loss coefficient based on wake momentum thickness and flow turning. It is shown that the wettability of the surface has significant effects on the water structure leading to a lower fraction of wetted surface with increasing contact angle. The influence on performance is limited to effects in the proximity of the surface and is dependent on operation point. While in design conditions hydrophilic coating show lower losses the trend is vice-versa for off-design conditions.

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