STEADY STATE STRESS ANALYSIS AND HEAT TRANSFER ANALYSIS ON AN AXIAL FLOW GAS TURBINE BLADES AND DISK

摘要

To be able to design next generation of gas turbines it is necessary to improve the knowledge about the stress values produced in the turbine. A gas turbine rotating system is loaded with time by the changes in stress levels as a result of start-up and shutdown procedures, i.e. Low-cycle fatigue (lcf), as well as by steady forces caused by rotation (centrifugal stress) and thermal gradients, as also by high-cycle fatigue(hcf) in the course of normal operating conditions. Except during the start-up and shutdown procedures, the emphasis are given on the steady state analysis because of the turbine's maximum operating period is in almost steady state. The main entity of these versatile machines is made by the blades and vanes, which are subjected during operation to very high thermal and mechanical stresses (combined effects of centrifugal force and thermal gradient), in aggressive environment. The research on gas turbine cooling systems is coupled with the flow and heat transfer associated with rotating turbine. Therefore this report has primarily focused on the heat transfer characteristics, centrifugal and the thermal stresses arising in the disk. The maximum stresses obtained from different analyses by using innovative high heat resistant material inconel 718 are found to be within the yield strength of the material. Interesting results obtained in terms of maximum operational radial stress, maximum operational hoop stress, maximum operational Vonmises stress, the temperature field etc. The values of the stresses indicate that the disk attains steady state after 450 seconds. And the disk is expected to perform well in spite of all the stringent operating conditions. The object is to provide understanding and information for designers to improve the life and efficiency of future generations of engines.