Compressors, pumps, and pipeline fittings

Abstract

Based on thermodynamic calculations it is shown that it is possible to reduce unit cost and metal content and raise generating capacity of power plants by using advanced steam-gas plants having steam-turbine compressor drive mechanically separated from the gas turbine.Presently, many power plant equipments require updating. There are well-known designs usable for raising thermodynamic efficiency of power plants. These designs are based, in particular, on multi-loop systems and broadening of temperature range of operating cycle [1]. Furthermore, preliminary analysis shows that it is possible to reduce unit cost and metal consumption and raise generating capacity of power plants by employing steam-gas plants (SGP) having steam-turbine compressor drive mechanically separated from the gas turbine [2].The basic distinction of conventional gas-turbine plants (GTP) from SGP consists in low performance factor (efficiency) defined as the ratio of the useful work of the GTP to the useful work of the SGP since as much as 60% of the SGP power is expended for driving the compressor. The total net power of the SGP energy complex is 30% higher than that of the GTP [3], which favors efficiency growth.Thermodynamic calculations of a conventional SGP give an idea about power redistribution between a gas turbine, a compressor, and a steam turbine (Table 1) [3]. In this plant, the compressor, gas turbine, and power generator are mechanically interconnected. The calculation was performed for a basic system having a single-loop waste-heat boiler at the fixed mass gas flow G = 500 kg/sec through the gas turbine and at various gas temperatures before the gas turbine t 3 .The degree of air compression ε in the compressor and the effective (net) efficiency η rise as the temperature t 3 rises. With rise in the temperature t 3 from 900 to 1500°C, the power of the steam turbine t ST rises more than twofold, the reason for which is the rise in temperature of the gases flowing from the gas turbine into the waste-heat boiler from 436 to 640°C. Simultaneously, the ratio N c /N GT falls from 0.59 to 0.51, the ratio N ST /N SGP remains practically unchanged, and the ratio N GT /N SGP diminishes by 25.7%. The excess of the power N SGP over the power N GT was calculated by the formula ΔN GT = N SGP -N GT .When a two-loop waste-heat boiler is used in a conventional SGP system, the correlations of the parameters given in Table 1 do not change materially: the power N ST and the efficiency η rise a little, and with temperature rise the difference between the efficiencies of the compared plants diminishes and at t 3 = 1500°C comprises only 0.72%. As a result of increase in the power N ST , the difference ΔN GT also diminishes a little.Let us examine an SGP having a separate steam-turbine compressor drive, which is schematically shown in Fig. 1 (t 0 -t 6 are the temperatures of the heat carrier in respective sections of the system).The gas-turbine section of the plant operates in an open loop where atmospheric air flows into the compressor 3 for compressi...