Method for Calculating the Parameters of an Axial Microturbine at the Initial Design Steps

The paper presents a method for estimation the main parameters and structural-geometric parameters of an small scale axial turbine operating at large pressure drops at the initial design step. The proposed method is based on null-dimensional, one-dimensional and two-dimensional (axisymmetric) models of the working process of small-sized axial turbines and considers a number of their features. These include increased loading, close to zero degree of stages reactivity, reduced values of relative blade heights, partiality of fixed blade rims and small flow angles at their outlet. The proposed method includes four steps. They are united in a single sequence of actions, which allows you to justify the choice of turbine scheme, values of its energy, gas-dynamic and geometric parameters. Thus, it is possible to form the appearance of the turbine flow path in the meridional plane, to determine values of the main geometric parameters of the gratings of the blades profiles of the nozzle and guide vanes, as well as the rotor wheels of the turbine stages. The developed method is used to compare the energy efficiency of two configurations of a two-stage axial turbine flow path differing in the manufacturing technology of its blade rims. The second configuration feature is that the included blade rims are made with the same height profiles corresponding to the profiles of the average diameter. Estimation of possible efficiency reduction showed that in the second case it can be no more than 0.4%.