The method of averaging the gas flow parameters in turbomachines to evaluate their efficiency considering the velocity-field helicity
N.N. Kortikov
Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia
Keywords: осреднение, спиральность поля скорости, энтропия, завихренность, вторичные течения, турбинная ступень, коэффициент полезного действия, полная температура, энтальпия торможения, коэффициенты неравномерности, averaging, helicity of the velocity field, entropy, vorticity, secondary flows, turbine stage, efficiency, total temperature, stagnation enthalpy, coefficient of non-uniformity
Abstract
The methodology of averaging the nonuniform swirling flow in turbomachines has been developed. It is based on preserving the mass flow rate, the fluxes of total enthalpy and momentum (or entropy) with the addition of new invariant into the algorithm, i.e., the integral of the gas flow helicity. The dependence has been obtained and validated to specify the turbine stage efficiency calculation and to take into account the presence of large-scale vortex structures in the inter-blade channel of the turbomachine (the uncertainty of the influence of secondary flows on the value of losses does not exceed 0.2 %). The methods of averaging the gas flow parameters, taking into account the contribution of secondary flows to the kinetic energy loss are presented. They show a 2.4 % lower efficiency compared to the calculation previously used for the turbine stage of the Leningrad Polytechnic Institute.
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