HEAVY-DUTY GAS TURBINES AXIAL THRUST CALCULATION IN DIFFERENT OPERATING CONDITIONS

Several types of forces give a contribution to the axial thrust of gas turbines shafts: flow-path forces (due to blades, endwalls and shrouds of compressor and turbine rows), forces acting on the surfaces of rotor-stator cavities, disks forces (due to the different pressure levels in the rotating cavities inside the rotor), etc. As a rule, the estimation of the rotor thrust needs the handling of a large amount of output data, resulting from different codes. This paper presents a calculation tool to estimate the rotor axial thrust from the results of compressor, turbine and secondary air system calculations. Applications to heavy-duty gas turbines of different classes and sizes (namely two models of AEx4.3A F-class family, AE64.3A and AE94.3A, and the AE94.2 E-class gas turbines) are presented. On the basis of calculation results, in base load and part load operating conditions, guidelines to determine the rules of variation of axial bearing thrust and the relating scatter band are given. Pressure transducers were installed on the bearing pads of different gas turbines, in order to provide experimental data for the calibration of the calculation procedure. Comparison of experimental data with numerical results proves that the proposed calculation tool properly evaluates gas turbines rotor thrust and the axial bearing load.