Due to enormous material losses in the case of emergency, it is vital to ensure the operation reliability of the natural gas pipeline compressor stations (CS). The risk of breakdown is rather high for gas turbines (GT) with total operation time approaching the design-estimated life and particularly for those in which the actual period of operation exceeds this value. Over 25% of turbine drives working on natural gas transportation net in Russia have exceeded their design life [1]. For instance, around 600 gas turbines of the GTC-10-4 type (10MW power) are still in service despite their 120,000–160,000 hours of operation (more than 1,000 gas turbines GTC-10 type have been made and installed at natural gas pumping stations in the seventies in Russia). These gas turbines contain several critical components. Most of them are related to the high temperature parts, including inner high-temperature turbine casing (ITC). This ITC is a kind of a collector (duct) connecting a combustion chamber outlet and the turbine’s entry. Combined with an insulation layer, it serves as a protective shield for outer (main) turbine casing against the effect of hot gases. Notwithstanding the fact that the GTC-10-4 turbine has a modest inlet gas temperature (TIT∼800°C), there are various problems with the ITC shape and state during the turbine’s operation. The ITC operates under conditions of dramatic temperature changes, pressure drops, extended periods of high temperature. All these factors can cause the ITC shell deformations, which results in poor turbine performances. Regular maintenance inspections including opening a turbine do not permit to establish reasons for dramatic changes in the ITC shape. A detailed numerical analysis has been performed to better understand the ITC dynamics over its service period of operation. Moreover, it should be observed that ITC forms a flow prior to entering a turbine. Then, gas flow is directed to the first stage nozzles of the turbine. Advanced numerical flow investigation methods were applied to improve hot gas distribution in front of the turbine. A considerable decrease in velocity nonuniformity was achieved both radially and circumferentially through the ITC shape optimization. Great need in this component stimulated introduction of a new manufacturing technology aimed at production of new ITCs and replacement of numerous defective ones still used at natural gas pumping stations across Russia. Results of thermo-deformation analysis and numerical flow investigation for various ITC configurations are presented in the paper. It also contains proposals for improving the state of the ITC and outer turbine casing (OTC) in the result of the fixing unit development and applying a new insulation material.
