An Experimental Study of Water Injection Into a Rolls-Royce Model 250-C20B Turboshaft Gas Turbine

Abstract

Abstract : Environmental responsibility is a focus of researchers in many fields. In the field of engine and propulsion research this is manifested in a focus on minimization of emissions while maximizing efficiency and performance. Water Fog Injection (WFI) has been suggested as a method for the suppression of nitrous oxide emissions in gas turbines. WFI consists of spraying a fine mist of water into the compressor inlet of the gas turbine. Prior research on larger, higher pressure ratio engines determined the WFI can not only reduce nitrous oxide emissions but also yields increases in power output and thermodynamic efficiency. While previous research has focused on large gas turbines, the effects of water fog injection on a smaller, lower pressure ratio gas turbine, as represented by the Rolls-Royce Model 250-C20B, have yet to provide conclusive results. This investigation determined the effect of WFI on the Model 250-C20B's exhaust gas composition, power output, thermodynamic efficiency and component efficiencies. The investigation used an instrumented Model 250-C20B gas turbine and an original water spray system. Temperatures and pressures were measured for each of the gas turbine's five state points. Exhaust gas composition and output shaft torque and speed were also measured. Experiments were conducted with water fog injection water flow rates ranging from 0.1 to 1.4 gallons per minute. This represents up to a maximum of 5 percent of the maximum mass flow rate of air through the engine. The results of these tests were compared with baseline runs conducted with no water fog injection. From the experimental data it was determined that the exhaust gas composition was significantly affected by the water fog injection.