The Method of Determining Total Losses in the Nozzle Cascades of Turbomachines

Abstract

To assess the level of aerodynamic efficiency of the nozzle cascades of steam and gas turbines, the method was suggested to determine the total loss coefficient instead of kinetic energy loss coefficient that takes into account both kinetic energy losses and kinematic losses. This method allows us to transform the original non-uniform spatial flow behind the cascade into an axisymmetric cylindrical flow. In the tested annular cascade with cylindrical meridional boundaries, the total loss coefficient is approximately 0.02 higher than the kinetic energy loss coefficient. By taking into account kinematic losses when performing thermal calculations for the turbines we eliminate the need for an unjustified correction of the kinetic energy loss coefficient of the nozzle cascade by 0.01–0.03, increasing thus the accuracy of calculations. To analyze the operation of individual sections of the nozzle cascade and to determine the relationship between kinetic energy losses and kinematic losses, it is advisable to use the averaging method proposed in 2021 that enables the transformation of the initial non-uniform spatial flow behind the cascade into an axisymmetric conical flow. The aerodynamic characteristics of this flow are the widely used kinetic energy loss factor and two averaged flow angles.