Influence of aspect ratio on aerodynamic and mechanical design of compressor inlet stage in heavy-duty gas turbines

Abstract

There are significant design challenges for the compressor inlet transonic stage of heavy-duty gas turbine with higher mass flow rate and power output. Aspect ratio is a critical parameter for the compressor inlet stage. The low aspect ratio design concept has been established in aero-engines, but few studies on the concept for heavy-duty gas turbines are reported. In this paper, the low aspect ratio design concept is investigated and validated in the compressor of a heavy-duty gas turbine. The effects of aspect ratio on both the aerodynamic performance and mechanical integrity of the compressor inlet transonic stage were investigated. It is shown that lower aspect ratio is better for efficiency and surge margin compared to higher aspect ratio in the range of 1.3 to 2.0. A lower aspect ratio compressor blade has higher first-order natural frequency, allowing for higher resonant avoidance rate and lower flutter risk. The low aspect ratio design concept was applied in the compressor inlet transonic stage of a heavy-duty gas turbine to meet the multi-disciplinary design requirements, including aerodynamic, vibration and flutter. The design was validated based on the inlet three-stage rig test. Both the aerodynamic parameters measurement and the non-contact blade vibration measurement are conducted. The experimental data shows that the compressor inlet transonic stage using low aspect ratio concept has good aerodynamic performance and vibration characteristics.