Gland Seal Erosion in a Geothermal Turbine

Excessive erosion of the low-pressure shaft end gland seal of a 25 MW geothermal turbine has been investigated. Due to excessive erosion of the gland seal rotor surface the turbine vacuum was partially destroyed and the efficiency of the cycle degraded. This study uses computational fluid dynamics (CFD) to identify the causes of erosion and the optimal steam seal system flow conditions for reducing the erosion problem. The predictions were based upon a numerical calculation using a CFD model of the rotor end gland seal with a steam flow containing hard solid particles and solved with the commercial CFD code: Adapco STAR-CD. The results confirmed the existence of flow conditions that play a major role in the rotor gland seal erosion. Afterwards, the flow was simulated changing seal steam flow conditions (flow pressure). It was confirmed that there exists threshold seal flow conditions below which erosion does not occur. The recommendations for adjusting shaft end gland seal system are provided to avoid erosion problem.