Investigating the effect of cooling channel roughness and coolant humidity on the creep life of gas turbine blades

ARTICLE INFORMATION ABSTRACT Original Research Paper Received 20 September 2015 Accepted 22 November 2015 Available Online 19 December 2015 Gas turbine blades operate at high temperature under mechanical loads; hence creep failure is the major concern in their design. To increase blade creep lifetime, it is necessary to reduce the blade temperature. For this purpose, cooling flow passes through the inner channels of the blade. In this paper, coolant heat transfer along the channels has been modeled and the effects of wall roughness and coolant’s specific humidity have been investigated. The blade body and cooling channels are regarded as a heat exchanger with thermal barrier coating and convective film cooling. A computer code has been developed to calculate the physical properties of the coolant as a function of temperature and humidity. Then, by taking into account the effect of wall roughness, convection coefficient and temperature distribution on the blade have been obtained using an analytical solution method. The results show that in the rough channels, coolant receives more heat from the blade body and consequently its temperature decreases especially in the critical section. It has been shown that with increasing humidity; the coolant temperature decreases along the blade span and consequently, the blade metal temperature reduces with about 2.5 percent. Also the result show that by increasing coolant’s humidity and roughness of the channels within a reasonable range, blade’s creep lifetime can be increased by up to 3.18 times.