One common method of reducing the NOx emissions from industrial gas turbines is to inject water into the combustion process. The amount of water injected depends on the emissions rules that apply to a particular unit. Westinghouse W501B industrial gas turbines have been operated at water injection levels required to meet EPA NOx emissions regulations. They also have been operated at higher injection levels required to meet stricter California regulations. Operation at the lower rates of water did not affect combustor inspection and/or repair intervals. Operation on liquid fuels with high rates of water also did not result in premature distress. However, operation on gas fuel at high rates of water did cause premature distress in the combustors. To evaluate this phenomenon, a comprehensive test program was conducted; it demonstrated that the distress is the result of the temperature patterns in the combustor caused by the high rates of water. The test also indicated that there is no significant change in dynamic response levels in the combustor. This paper presents the test results, and the design features selected to substantially improve combustor wall temperature when operating on gas fuels, with the high rates of water injection required to meet California applications. Mechanical design features that improve combustor resistance to water injection-induced thermal gradients also are presented.

The field conversion of two W501D5 combustion turbines to burn medium Btu fuel gas supplied by a Dow Chemical coal gasification process at Plaquemine, LA resulted in excessive 105-Hz airborne sound and a corresponding unacceptable nonsynchronous engine vibration when burning natural gas. A joint Westinghouse and Dow Chemical corrective action program is described including field tests. Test results indicated that the combustion noise phenomenon was related to the strength of the primary air scoop recirculation pattern and its compatibility with the fuel and steam momentum vectors. A design was selected that eliminated the nonsynchronous combustion noise generated vibration and reduced the 100-Hz third-octave noise from 115 db to 97 db, an intensity reduction of 64 to 1.

The field conversion of two W501D5 combustion turbines to burn medium BTU fuel gas supplied by a DOW Chemical coal gasification process at Plaquemine, Louisiana resulted in excessive 105 Hz airborne sound and a corresponding unacceptable non-synchronous engine vibration when burning natural gas. A joint Westinghouse and DOW Chemical corrective action program is described including field tests. Test results indicated that the combustion noise phenomenon was related to the strength of the primary air scoop recirculation pattern and its compatibility with the fuel and steam momentum vectors. A design was selected that eliminated the non-synchronous combustion noise generated vibration and reduced the 100 Hz third-octave noise from 115 db to 97 db, an intensity reduction of 64 to 1.

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