Cooling and Sealing Air System in Industrial Gas Turbine Engines
Siemens heavy duty Gas Turbines have been well known for their high power output combined with high efficiency and reliability for more than 3 decades. Offering state of the art technology at all times, the requirements concerning the cooling and sealing air system have increased with technological development over the years. In particular the increase of the turbine inlet temperature and reduced NOx requirements demand a highly efficient cooling and sealing air system. The new Vx4.3A family of Siemens gas turbines with ISO turbine inlet temperatures of 1190°C in the power range of 70 to 240 MW uses an effective film cooling technique for the turbine stages 1 and 2 to ensure the minimum cooling air requirement possible. In addition, the application of film cooling enables the cooling system to be simplified. For example, in the new gas turbine family no intercooler and no cooling air booster for the first turbine vane are needed. This paper deals with the internal air system of Siemens gas turbines which supplies cooling and sealing air. A general overview is given and some problems and their technical solutions are discussed. Furthermore a state of the art calculation system for the prediction of the thermodynamic states of the cooling and sealing air is introduced. The calculation system is based on the flow calculation package Flowmaster (Flowmaster International Ltd.), which has been modified for the requirements of the internal air system. The comparison of computational results with measurements give a good impression of the high accuracy of the calculation method used.