Optimizing the clearance dimensions of the gas turbine combustion chambers using the Taguchi method

Temperature management in turbomachines is a critical factor for improving power plant efficiency and service life. Air gap clearances between combustion chamber rings assist its installation and expansion while partially modifying the inlet air path to stave off mixing in the flame tube of the combustion chamber. Changes in clearance dimensions can cause geometric asymmetry and result in asymmetric flow and temperature distribution imbalances in the combustion chambers creating hot spots at the outlet of the combustion chamber. Hence, in this paper, the effects of four clearance dimensions with four values on temperature distribution in two combustion chambers attached to the compressor have been numerically studied using Ansys Fluent 17. Taguchi method is applied for optimization and decreasing the outlet semi-circles temperature difference using Minitab software. The optimization results illustrate that the radial clearance between the flame tube and the mixing chamber is the most significant variable in controlling the air flow rate and producing symmetrical temperature distribution in the two chambers. So, one-millimeter radial clearance between two chambers leads to an increase of the temperature distribution by 15oC and 100oC in average and point mode, respectively. Also, results show that as the average clearance of the combustion chamber decreases by 5 millimeters, the point mode temperature of its corresponding outlet semi-circle decreases around 100°C.