Réduction des émissions d'oxydes d'azote d'une turbine à gaz aérodérivée

Nowadays, aeroderivative gas turbines are commonly used for land-based applications such as electrical power generation and mechanical drive. As opposed to jet engines, they are subject to more stringent regulations regarding pollutant emissions. Hence, the original equipment manufacturers (OEM) are challenged to develop pollutant control strategies to deal with these unprecedentedly low emission limit values while trying to maintain, or even improve, current gas turbines performance. This work aimed to reduce the nitrogen oxides (NOx) emissions from an aeroderivative gas turbine developed by Siemens. Such a goal required the homogenization of the air and fuel mixture prior to its combustion which is achieved through optimization of the burner configuration. More specifically, the hole pattern of a perforated plate located in the combustion chamber had to be improved. Therefore, a simplified model of a section of the actual combustor was designed and built to accommodate for a measurement technique called planar laser-induced fluorescence (PLIF). The test rig was sized in function of theoretical calculations, computational fluid dynamics analysis and practical reasons. It has been decided to replace the air and fuel that compose the mixture of interest by water in order to perform nonreacting tests. Furthermore, to achieve optimal similarity between the experimental and real mixing conditions, the test rig must be operated at the engine velocity ratio and at Reynolds numbers above 10,000. A physical access to the interior of the prototype was needed to change the removable parts in between the different experiments. The construction techniques that were used to build the prototype and its support include machining, 3D printing, computer numerical control machining and welding. A hydraulic system was also designed and installed in the experimental facility to feed the test rig. Finally, theoretical recommendations based on a literature review of the topic were made concerning the optimal hole pattern of the perforated plate. It is suggested to use a perforated plate with a solidity of 35%, a thickness of 6 mm, and 41° tapered holes to provide the highest degree of turbulence intensity, and thus the most uniform mixture of air and fuel in terms of homogeneity.

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