Investigation of Compressor Blade Roughness Increment Effect on Micro Turbine Performance

Because of challenging operating conditions, gas turbine is exposed to fouling, erosion and other damaging factors. Compressor fouling is the main reason of gas turbine performance deterioration and its most important effect is the increase in the roughness of blade surface. Compressor fouling leads to gas turbine performance deterioration and increasing of operating cost. Gas path analysis is one of the methods used to detect components’ damages of gas turbine. In this method detection of each damage is made possible by monitoring related sensitive parameters. The superiority of this method over the visual inspection method is monitoring implementation without shutting unit down which deletes costs of unit shut down and removal from circuit. Moreover continuous health monitoring of gas turbine is possible. This paper aims to study effect of roughness increase in the compressor blade on a micro gas turbine performance in part and full load and determination of parameters which are sensitive to fouling. To achieve this goal, characteristic of a radial compressor in clean state and three different surface roughnesses has been used. Characteristic is utilized to simulate off-Design performance of a micro turbine in part and full load. Results of off-Design performance simulation in clean state are validated against experimental data. Effects of roughness increment have been calculated and sensitivity of performance parameters in different loads have been analyzed. The simulation’s results show that blade roughness increment induces new condition which improves recuperator performance and micro turbine thermal efficiency in constant speed. But in this condition turbine inlet temperature is raised and exceeds the maximum allowed temperature. So the maximum allowable output power is decreased. Results show that net output power, combustion chamber inlet temperature and turbine exhaust temperature are the most sensitive parameters to roughness changes while compressor discharge temperature shows insignificant sensitivity to roughness increment.