Parametric Analysis of Aero-Derivative Gas Turbine: Effect of Radiative Heat Transfer on Blade Coolant Requirement

Air-film cooled gas turbine is widely used in aero-derivative gas turbines. The present paper reviews previously developed air-film blade cooling models. The article further proposes a new blade cooling model for estimating blade coolant mass fraction which takes into account the effect of radiative heat transfer from hot flue gases to aero-derivative gas turbine blade surface. Various possibilities to achieve enhanced performance from aero-derivative gas turbine have been enumerated namely effect of advanced design philosophies, thermal barrier coatings, advancement in blade material. Also adoption of advanced design philosophies such as 3-D CFD would lead to improved component design. Further use of advanced blade material specifically for gas turbine blade application including single-crystal blade, directionally solidified blade material being nickel-chrome-molybdenum alloys may be explored. Adoption of advanced thermal barrier coating material and latest technique for application of TBCs on blade surface so as to achieve longer TBC life may be adopted. From thermodynamics it is known that thermal efficiency of an energy conversion system increases with a rise in temperature at which heat is added to the cycle. This is possible by increase in TIT for a fixed blade material temperature. The proposed model is expected to offer an enhanced coolant mass fraction which is supposed to increase the accuracy of prediction of actual coolant requirement while analyzing aero-derivative aviation gas turbine cycle which may lead to extension of blade life. Aero-derivative gas turbine cycle performance has been evaluated based on proposed blade cooling model to compute blade coolant flow mass fraction, gas turbine plant specific work which are the function of both compressor pressure ratio and turbine inlet temperature.