Study On Sealing Performance Of Turbine Crankcase Flanges

Aeroengine is a complex structure and power machinery with high quality requirements of its components. It plays an important role in the development of the aviation industry as it is the major source of propulsion of aircrafts. Every parts of the engine are equipped by bolted flange connection at the installation edges. Under high temperature and pressure, the internal fluid will release through the edge of the flanges. Therefore, the sealing performance of turbine crankcase flanges is an important index for aeroengine evaluation. Improving the sealing performance of the flanges is very important for the safity and efficiency of the aeroengine.The contact surfaces of the bolted flanges are the focus of the investigation where we need to get contact stress and contact gap. This article defines contact gap as the evaluation indicator of sealing performance and will do further exploration based on achievements at home and abroad. With a turbine crankcase model as the research object and based on the existing double single bolted flange connection stiffness theory, ANSYS software is used to do circumferential and longitudinal segmentation researches. This article also uses some typical test pieces to find the factors affecting the sealing performance and to make prestressed modal analysisThis paper is divided into four chapters.Chapter one introduces the development status about bolted flange connection research at home and abroad and gives the significance of this article.Chapter two briefly describes the basic theory of bolted flange connection, and gives the calculation method of bolt rigidity, and combines the theory of double single bolted flange connection stiffness with finite element solutions. Equivalent connection stiffness is used to calculate the rigidity of the three layers of single bolt flanges, and is than compared with the finite element solutions. The error is within the acceptable range. All of the above are done to verify the correctness of ANSYS software in bolted flange connection problems.Chapter three respectively studies circumferential edge and vertical edge segmentation to find the relationship between the length and the error. The conclusion is that the error is within 15%. It means that when we study the effects of some parameters on the sealing performance, a small section of the model can be used to represent the whole casing model. which omits the modified operation of the whole model and improves the design efficiency.Chapter four targets on some typical test pieces to investigate parameters such as flange thickness, space between the crankcase edge and the holes, hole space of the bolts, hole size of the bolts, pre-tightening force of the bolts, fitting materials. Measures to improve sealing performance are proposed:increasing the flange thickness, narrowing space between the crankcase edge and the holes, narrowing the hole space of the bolts, increasing the bolt size and pre-tightening force, improving the material elastic modulus. Prestressed modal analysis is done to study how the design parameters affect the vibration modes. The conclusion is:the influence parameters of the first bending mode are space between the crankcase edge and the holes, hole space of the bolts and the material elastic modulus. Finally the leakage formula is put forward.