Proračun prelaznih režima rada gasnih turbina

Abstract

Promena udela obnovljivih izvora energije u proizvodnji elektricne energije dovodi do promene uloge koje konvencionalna postrojenja imaju u elektroenergetskom sistemu jer se zahteva fleksibilan rad i brzo startovanje. Menja se koncept razvoja novih postrojenja i, osim stacionarnih režima, postaje bitno izucavanje prelaznih pojava kao što su startovanje, brze promene opterecenja, normalno i prinudno zaustavljanje. Veliki deo razvoja obuhvata skupa eksperimentalna ispitivanja pri kojima može doci do oštecenja mašine. Stoga se veliki trud ulaže u razvoj proracunskih modela za predvi anje ovakvih režima što je i tema ove disertacije. U radu je opisan dinamicki model za simuliranje razlicitih prelaznih režima rada gasnih turbina u celokupnom radnom opsegu, od pokretanja do zaustavljanja. Radni režimi kompresora i turbine opisani su pomocu stacionarnih karakteristika, dok je njihovo dinamicko ponašanje modelirano zakonima održanja u obliku obicnih diferencijalnih jednacina. Pored osnovnih fenomena, akumulacije mase i energije, kao i akumulacije toplote unutar konstruktivnih elemenata mašine, obuhvaceni su i efekti promene radijalnih zazora na performanse. Primenjene radne karakteristike su izracunate pomocu postojecih meridijanskih modela strujanja. Kako bi se obuhvatio uticaj promena geometrije kompresora zbog zakretanja statorskih lopatica kao i promena radijalnih zazora, implementiran je veliki broj karakteristika. Model je uparen sa osnovnim sistemom regulisanja radi kontrole brzine/opterecenja i izlazne temperature gasova iz turbine. Razvijeni model je primenjen za simulaciju rada jednovratilnih i dvovratilnih industrijskih gasnih turbina i rezultati su upore eni sa eksperimentalnim podacima. Pore enje ukljucuje veliki broj parametara za svaku komponentu postrojenja i startera koji se koristi pri startovanju. Simulirane su sekvence startovanja iz hladnog stanja, nagle promene opterecenja, zaustavljanje ali i rad mašine tokom više uzastopnih pokretanja radi analize uticaja termickog stanja na performanse mašine. Sprovedene su i analize ponašanja gasne turbine pri razlicitim brzinama promene i naglog gubitka opterecenja.

The change in the share of renewable energy sources in electricity production leads to a change in the role conventional power plants have in the power system, as flexible operation and quick start-up are required. The concept of new power plant development is changing and, apart from stationary regimes, it becomes important to study transient phenomena such as starting, rapid load changes, normal and emergency shutdown. Much of the development involves expensive experimental tests that can damage the machine. Therefore, a lot of effort is invested in the development of computational models for predicting such regimes, which is the subject of this dissertation. It describes a dynamic model for simulation of the complete transient operation of gas turbines, from start-up to shutdown. The performance of the compressor and the turbine are described using steady-state characteristics, while component dynamics are modeled with the conversation laws in the form of ordinary differential equations. In addition to basic transient phenomena, volume packing, and heat soakage, the effects of the tip clearance change on the performance are also included. The applied component characteristics are calculated using through-flow solvers. A large number of compressor maps are implemented to include adjustments of stator blades and changes in tip clearances. The model is paired with a control system for the regulation of speed/load and turbine exit temperature. The developed model was applied to simulate the operation of single-shaft and two-shaft industrial gas turbines and the results were compared with experimental data. The comparison includes a large number of parameters for each component of the power plant and the starter used during start-up. Sequences of starting from a cold state, sudden load changes, shutdown, but also the operation of the machine during several consecutive start-ups were simulated in order to analyze the influence of the thermal state on the performance of the machine. Analyzes of the behavior of the gas turbine at different loading rates and at load rejection were also carried out.