A database consisting of 18 heavy-duty and aeroderivative gas turbine engine models, fired on natural gas, is evaluated for NOx exhaust emissions with and without water and steam injection. CO exhaust emissions are also considered. Engine baseload power outputs range from 2.9 to 83.5 MW, compressor pressure ratios are from 7.2 to 30.0, and turbine inlet temperatures are from 1150 to 1515K. The engine models are from the late 1970s to the current period, and all use diffusion flame combustors.

Baseload, uncontrolled NOx exhaust emissions, corrected to 15% O2 dry conditions, vary from 67 to 240 ppmv. CO exhaust emissions vary from 7 to 96 ppmv. Except for three low-NOx aero-derivative engines, the uncontrolled NOx exhaust emissions scale with engine pressure ratio and fuel-air ratio. A correlation formula is developed, and discussed relative to formulas in the literature. NOx control by water injection shows a fairly wide band; at a water-to-fuel mass ratio of 0.8, the NOx reduction varies from 58 to 82 percent. Engines with the highest uncontrolled NOx show the largest percentage reduction by water injection. On the other hand, NOx control response with steam injection exhibits less variation across the engine models. The relation of CO to NOx levels and and the response of CO to water and steam injection are examined, though quantitative correlations are not made.

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