This article focuses on the work done at GE from 1960s to the early 1980s. GE funded the project of developing a full pressure/full temperature model of the same size. Test facilities were also built and run to gather data on potential problems such as: long term effects of partial channel water cooling on erosion, corrosion, and deposition; water supply, distribution and collection in the outer casing; materials testing with contaminated fuels. The results of the Electric Power Research Institute (EPRI) program were sufficiently encouraging that GE and EPRI decided to advocate a bigger project to the US Department of Energy to demonstrate the concept in utility size components. GE dropped work on water cooling in the early 1980s. Part of the reason was concern of instabilities in the boiling water.
Development of water-cooled gas turbines has had a long history starting in 1903, which is summarized in reference 1. The present article focuses on the work done at GE from the 1960s to the early 1980s.
The Beginnings of GE's Work
During World War II the Schmidt Turbine was an attempt by Germany to use water cooling to enable high temperatures in the turbine section of an aircraft engine, as materials and air cooling technology were not very effective at that time. Cooling the nozzles (stationary airfoils) with water was not a problem, but cooling the buckets (rotating airfoils) proved to be an insurmountable problem because the cooling was closed circuit which created problems getting the liquid in and out of the moving part and distributing it effectively in the presence of a very high centrifugal field, resulting in cracked buckets, so the concept was abandoned.
By the early 1960s there was interest in the gas turbine industry in accommodating low cost and dirty fuels (e.g. coal gas and residual oil like bunker C), but a problem was hot corrosion from the contaminants in the fuels. A possible solution to this problem was water cooling: If you don’t have hot airfoil surface temperatures, you won’t have hot corrosion.
Dr. Paul H. Kydd, a researcher at GE's Corporate R&D Center in Schenectady, NY thought of a different approach vs. the Schmidt Turbine: Let the water go outside the tip of the bucket, metered so it used about 2/3 of the latent heat of evaporation and expelled the rest. This would keep the bucket surface cool enough to eliminate hot corrosion and keep the pressure low enough to prevent cracking. He demonstrated the concept in a 12 inch diameter rotor using flattened 347 stainless steel tubing for the buckets at atmospheric pressure and 2800̊ F. This convinced GE's Gas Turbine Division to fund the project of developing a full pressure / full temperature model of the same size. See reference 2 for details.
The Energy Crisis of 1973 and EPRI Program
With the 1973 Arab Oil Embargo and sharply increasing prices for gas turbine fuel the industrial gas turbine industry went into a sharp decline, as did the entire US power generation business. The Edison Electric Institute enabled the founding of the Electric Power Research Institute, partly because they feared that the federal government would start to dictate R&D in the power generation industry, and they wanted to have some control of that. At that point the electric utilities were mostly regulated monopolies, and EPRI worked with the US regulated utilities to add a charge on consumers’ electric bills to fund EPRI. GE won a contract from EPRI to demonstrate the water-cooled turbine concept at full pressure and temperature with realistically shaped airfoils. This was done successfully, at a turbine inlet temperature of 2850̊ F and 16 atmospheres with metal temperature of less than 1000̊ F (Reference 3). Test facilities were also built and run to gather data on potential problems such as 1) Long term effects of partial channel water cooling on erosion, corrosion and deposition, 2) Water supply, distribution and collection in the outer casing, 3) Materials testing with contaminated fuels. See reference 3 for details.
The HTTT Program
The results of the EPRI program were sufficiently encouraging that GE and EPRI decided to advocate a bigger project to the US Department of Energy (then known as the Energy Research and Development Administration or ERDA) to demonstrate the concept in utility size components. The result of that advocacy was the US Department of Energy's High Temperature Technology Turbine (HTTT) Program, which was a major effort to develop advanced turbine cooling technology, including water-cooled turbines. GE was a winner of the 4-way competition for funding on large gas turbines, and the HTTT program was launched in 1977 to carry on the work of the EPRI program, to full scale utility size components.
GE dropped work on water cooling in the early 1980s. The following is speculation by the author, who led the water cooled turbine effort at GE from the late 1960s through 1978 and left GE to join United Technologies in January 1979.
Part of the reason (reference 1) was concern of instabilities in the boiling water. But there were other major forces at work in the gas turbine industry which were arguably more important in GE's decision to drop water cooling:
By the 1980s the fuel of choice in the gas turbine industry was natural gas, which had become widely available enough for utilities to use it. So coal gas and residual oil were not as important for fuel sources.
Emissions regulations were becoming stricter, so it was not permissible to simply burn a contaminated fuel; you had to make the fuel clean before it got to the combustor or spend the capital cost of exhaust cleanup. Thus there was less need for a turbine that could burn contaminated fuels.
Air cooling technology had developed so far, so fast (thanks to military and commercial aircraft engine development) that water cooling was not necessary for industrial GTs to become the most efficient and lowest cost per kW option in electric power generation.
So it seems that water cooling died a natural death as one technology supplanted another.