Joint optimization of power plant cycle parameters and gas turbine flow path parameters with blade airfoils represented by cubic splines

Normally, optimization of gas turbine unit cycle parameters and optimization of gas turbine flow path are performed separately. This reduces the quality of the obtained optimal solutions. The paper considers an original method of joint optimization of thermodynamic parameters of power plant cycle and flow path parameters. Optimization of a 250 MW gas turbine unit is used to illustrate the methodological approach. The optimization criterion is to maximize power plant energy efficiency. Pressure sides and suction sides of the base airfoils are represented by a spline defined by 70 cubic polynomials. The parameter optimization problem of gas turbine unit cycle and gas turbine flow path includes 121 independent optimized parameters and 184 inequality constraints. The optimization results can be used in the preliminary design of power plants. In this case the obtained airfoils can serve as a good initial approximation for 3D optimization. The research demonstrates that the optimal temperature at gas turbine inlet is determined by the blade alloy characteristics, a cooling method and a shape of airfoils. This confirms the validity of the joint optimization of gas turbine and flow path parameters. - Highlights: • Innovative method of joint optimization of gas turbine cycle and flow path. • Optimization based on the representation of airfoils as a linear combination. • Optimization of base airfoils according to the least maximum curvature criterion. • Presentation of a case study of the 250 MW gas turbine unit optimization. • Discussion of the impact of blade alloy and cooling system on the cycle temperature.