Engineering Transactions, 61, 2, pp. 99–117, 2013

Failure Analysis (Experimental and Numerical Approach) of Gas Turbine Generator Cooling Fan in Comparison between using 2types (14◦ and 19◦ Angle of Attack) of Blades

Semnan University, Faculty of Mechanical Engineering

Seyed Ebrahim Moussavi TORSHIZI
NRI – Niroo Research Institute

Seyed Majid Yadavar NIKRAVESH
Power & Water University of Technology

In gas turbine power plants, a fan is used as a cooling system to dissipate generated heat
in coils (copper conductors) and generator electric circuits at the end sides of its rotor. In
some cases, fracture of blades causes a short circuit between rotor and stator and consequently
generator explosion and financial problems. The fracture of cooling fan blades has occurred
five times at the turbine side of the generator in our case of study, just 100hr after resuming
operations after an overhaul.
Using numerical analysis as well as laboratory investigation – including visual inspections,
metallography and SEM – can help better find failure problems that cause blade failures.
A series of numerical analysis was performed to diagnose the possible cause of failure. CFD
analysis is used to study the airflow distribution in order to observe probable separation phe-
nomenon and pressure forces as they are imposed on fan blades due to operation. A finite
element method was utilized to determine the stresses and dynamic characteristics of the fan
blade (natural frequencies, stresses and vibrations).
Key words: fatigue failure, dimple rupture, fan blade, scanning electron microscope (SEM),
resonance, fan blade angle of attack, computational fluid dynamic (CFD), finite elements.
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