Design and analysis of amulti‐stageaxial turbine for gasifiedcoal‐waterpower system

Abstract

Efficient coal gasification is critical to energy saving and environmental protection. Based on a power generation cycle of coal gasification in supercritical water, this article develops a design method for its low‐pressure turbine component. The working medium is a mixture of gasified water and carbon‐dioxide (H₂O/CO₂). Preliminary design is combined with an optimization algorithm to get the optimum design parameters. To analyze turbine off‐design performance, a quasi‐one dimensional (Q1D) analysis method is proposed, and three dimensional CFD (3D CFD) predictions are also conducted. In addition, a property table for computing thermodynamic properties of mixture fluids is adopted. It is not only employed in the preliminary design, but also utilized by Q1D and 3D CFD calculations. Based on the developed procedure, a nine‐stage H₂O/CO₂ axial turbine is finally designed. Results indicate that the designed H₂O/CO₂ turbine has an efficiency of 89.0% in the preliminary design, but 3D CFD predicts a lower value of 84%. This discrepancy is mainly due to a fact that the Q1D method ignores 3D flow effects because it uses empirical loss models to evaluate the performance. Moreover, both Q1D and 3D CFD numerical simulations prove a good off‐design performance of the turbine.