Numerical investigation of the effect on leakage flow of inclined labyrinth teeth with honeycomb sealing element

Turbomachines used in power generation systems such as power plants, aircraft engines, etc. are constantly evolving to meet the demands for high working conditions. In the development process, the requirement for high pressure and high temperature for turbomachines has also increased in line with this demand. Due to factors such as material strength limits, the losses within the turbomachines have been reduced in order to increase the efficiency. In components such as turbine and compressor, high operating conditions cause more leakage problems in the regions, where there should be little leakage flow. This thesis focuses on labyrinth sealing and honeycomb sealing models commonly used in gas turbines. There is evidence in the literature that sloping the labyrinth teeth into the region where the flow is coming (high pressure) reduces leakage flow. At the same time, due to the benefits of both leakage flow reduction and damping properties in the proper use of the honeycomb seal form, this both seal are often regarded as the preferred sealing elements in literature studies and industry applications. Application of honeycomb on both sloping and opposite surface (stator surface) of labyrinth teeth is not a very common application in the literature. In the study of this thesis, firstly, the fourth case, which is the subject of this thesis, was investigated in detail after the following first three case analyzes which are common in the literature. 1)Flat stator – Straight-through tooth (90 degree) 2)Flat stator – Sloped tooth 3)Honeycomb land – Straight-through tooth 4)Honeycomb land – Sloped tooth In this thesis to be examined, the flow problem is considered in two cases as the effect of geometric factors and working conditions. The parameters investigated are widely used in literature and industry applications. As the labyrinth tooth geometry parameters, we examined 4 different parameters for Cr={0.127-0.254-0.508-├ 1.016 mm}┤ and 3 different parameters for tooth inclination angle θ ={90°-70°-├ 50° }┤. The honeycomb geometry parameter HAD analysis was performed on three widely known parameters: HCs = {0.793-1.590-3.175mm}. As working conditions parameters also, HAD analyzes were performed to determine the effects of pressure difference (Pr = {1.5-2.0-2.5-3.0}) and rotor speed (Vr = {100-200-400m/s}) on the flow. HAD analysis makes it possible to conduct a 2-dimensional analysis on a symmetrical geometry for flat stator (non-honeycomb) situations, but it requires a 3-dimensional analysis in case of using honeycomb. However, due to the high mesh density, a three-dimensional periodic flow volume analysis has been performed instead of 3D-all flow volume. For HAD analysis, ANSYS-Fluent v.16, a commercial software package program, was used. HAD analyzes were first verified with the literature data and analytical equations for the first three cases. The performance of the newly designed combined seals in this thesis is compared to that of the labyrinth seal, which is conventional flat stator - flat tooth. In the case of a flat stator, a 70 degree slope for a 0.254 mm clearance reduced the leakage flow by 5.5%, whereas a 70 degree slope angle in the case of using honeycomb showed a decrease of 8.1% in the leakage flow. When compared to 0.508 mm clearance and 50 degree tooth inclination angle, the leakage flow reduction rate was ̴ 20.1% from 8.6%. When the study is summarized, positive effects of the new design are observed in terms of leakage flow prevention. However, it is important to choose the appropriate honeycomb size for each tooth clearance (Cr) and to choose the appropriate angle of inclination. Considering the fact that most losses in turbine bearings and compressor outlets occur in labyrinth seals, such improvements in the sealing elements are observed that it will continue in terms of engine power and fuel consumption.