Carbon Deposits in Gas Turbine Injectors

Abstract

The formation of carbon deposits in gas turbines is a recurring problem to which a lot of important work has been dedicated. These deposits cause a lot of problems and have a direct impact on the performance of gas turbines both from an environmental point of view and on the energetic efficiency and on hot parts life. In the combustion chambers of gas turbines, two different types of deposits may appear, one inside the fuel injectors and the other in the flame tube. The understanding of the formation of these deposits as well as their characterization is of up most importance for the design of the combustion chambers of gas turbines. The study presented in this paper summarizes the recent work carried out in IFP (Institut Français du Pétrole) on the formation of these deposits on the materials currently used in the design of the combustion chambers and injectors of gas turbines. A micro-pilot thermogravimetric unit operating at cracking temperatures to the order of 900°C allows us to define the parameters influencing the formation of these deposits. Thus, the influence of the nature of the material, of the composition of the charge and of the operating conditions (temperature, flow rate,…) on the formation of the deposits and their morphology was shown. This work was carried out by testing a turbine injector during several hours on a test bench reproducing the working conditions of medium power industrial gas turbine. Different physico-chemical characteristics of common turbine fuels have been tested in an inert atmosphere. The characterization of the deposits (obtained with an electronic microscope), shows their morphology, as well as their elementary composition. For different fuels and various operating conditions, this work allows also to compare different types of materials used in the construction of gas turbines.