APPLICATION OF STEAM TURBINES SIMULATION MODELS IN POWER GENERATION SYSTEMS

The goal of this work is to simulate partial load operation of steam turbines indifferent controlling modes. An isentropic efficiency function is associated to aspecific steam turbine. The Schegliáiev and the Stodola's Ellipse Law, relatinglevels of pressure with mass flow, are compared. The proposed operational modes are: a) sliding pressure; b) throttling valve; c) nozzle valve. As a conclusion, Schegliáiev and Stodola's models leads to very similar results and the operational modes by valves establishes theoretical limits of operation for steam turbines. The sliding pressure control is more efficient considering design operation

Guardiões de sementes crioulas: construção do conhecimento para a preservação da agrobiodiversidade pelos agricultores familiares de Ibarama, RS.

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Dry matter production and nitrogen use efficiency of giant missionary grass in response to pig slurry application

This study assessed the effect of successive applications of pig slurry on the dry matter (DM) production and the nitrogen use efficiency of giant missionary grass along two years. A total of 55, 110, 165, 220 and 275 m³ of pig slurry/ha/year were applied in order to supply 100, 200, 300, 400 and 500 kg of total N/ha/year, respectively. These treatments were compared with the ammonium nitrate (200 kg of N/ha/year) source of N and with a control (no nitrogen application). Annually, nitrogen was applied in four divided doses, after the cutting of forage grasses, which takes place five times a year. The total DM yield did not differ between years and increased linearly as a function of pig slurry application, ranging from 2,698 kg of DM/ha/year (control) to 11,371 kg of DM/ha/year (275 m³ of pig slurry/ha/year). There was an increment of 32.3 kg of DM/m³ of pig slurry/ha or 17.7 kg of DM/kg of N/ha. The highest average daily DM accumulation rate (66.8 kg of DM/ha/day) was achieved with the highest pig slurry rate, from February/2007 to April/2008. Nitrogen use efficiency did not differ across pig slurry rates (19.0 kg of DM/kg of N), but it was lower than that obtained with ammonium nitrate (30.3 kg of DM/kg of N). The efficiency index of pig slurry ranged from 0.52 to 0.72