The method of considering the efficiency of flow compartments of multi-stage turbines when calculating energy characteristics

Abstract

BACKGROUND: Modern methods of calculating energy characteristics of steam turbine units (STU) are based on development of digital models. Considering this, the main components of the STU’s model is a model of a multistage turbine.
 AIMS: Improvement of existing methods of calculating energy characteristics taking into account influence of efficiency of flow compartments.
 METHODS: Results of the studies dealing with new methods of development of energy characteristics of multi-stage turbines are presented in the article. In particular, the new method of considering the influence of changing the efficiency of flow compartments of multi-stage turbines depending on working body flow rate is proposed. The method of calculation of turbine energy characteristics is given. The proposed method is based on development of the model of a turbine unit taking into account changing of technical and economic performance of its specific elements depending on the load.
 RESULTS: Results of theoretical justification of a non-linear dependency of turbine flow compartments’ power on working body flow rate based on changing internal efficiency of stages at variable modes described with the Stodola-Fluegel equation are given in the article.
 Based on the solution of the Stodola-Fluegel equation, the equation for vane efficiency and the equation of isentropic heat drop, the dependence of flow compartment’s operation efficiency on relative working body flow rate is obtained. The advice for using it when modelling turbines is given.
 The analysis of the experimental data obtained at the testing of the PT-60-130/13 steam turbine was carried out. Experimental dependency of the stages’ efficiency on steam flow rate are presented. It is established that the proposed dependency of internal efficiency of turbines’ flow compartments complies with the theoretical and experimental data in a good quality and can be used in calculation of energy characteristics and modelling.
 As a practical value of the study, the model of the PT-60-130/13 turbine unit was developed. The mode diagram built with the use of the model and complying with the heat testing results is given.
 CONCLUSIONS: The developed model of the turbine unit helps to simulate any operation mode depending on electric and heat loads. In addition, with the use of the model, it is possible to take into account the influence of deviation of external factors from nominal values at development of the system of correction or estimation of fuel consumption increase related to these deviations.