Turbine Design Optimized for Wet Operation

University of California System: University of California, Berkeley
posted on 05/23/2010

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Operation of axial or radial turbines under wet conditions is generally avoided because of three performance disadvantages: (1) droplets are unlikely to strike the turbine blades in a way that efficiently converts their momentum to rotor torque; (2) the liquid film that forms on the turbine blades alters the aerodynamics of the flow and makes it challenging to optimize the design for performance; and (3) droplet impingement in conventional turbines can cause the rotor blades to erode, and thereby shorten the life of the turbine. To address this problem, UC Berkeley researchers have developed a turbine design that is optimized for wet operation (i.e. operation with internal flow of liquid and vapor fluid phases). As the replacement for the expansion valve in vapor compression refrigeration and air-conditioning systems, this  innovation can significantly enhance the energy efficiency of vapor compression systems by extracting additional power output and increasing the heat absorbing capacity of the refrigerant in the evaporator. Another version of the innovation can be used as the work output turbine in a Rankine cycle power generation system designed for wet turbine operation. This wet expansion cycle design has significantly higher heat input heat exchanger effectiveness, and higher energy efficiency than conventional Rankine cycles with superheat. 

This turbine design has numerous possible applications with the most immediate widespread, and therefore biggest impact being the replacement for the expansion valve in vapor compression refrigeration and air-conditioning systems. Other applications include Rankine systems for solar, geothermal and fossil fuel power generation.

Improved performance of wet operating turbines