In this paper, a turbine on-line performance calculation system is presented. The system was implemented on a 575 MW unit of the Israel Electric Corporation and has been in operation for one year. The system was developed jointly by IEC and Berman Engineering Ltd. The main feature of the described system is the precision of the turbine heat rate calculation. This increased precision of the turbine heat rate calculation was accomplished by utilizing sophisticated statistical techniques, such as parametric and nonparametric regression, robust estimation, special filtration methods, autocorrelation methods, and uncertainty estimation methods. This high precision allows using the calculated heat rate as the main input to the turbine diagnostic system. The selection of turbine heat rate as the main diagnostic input is due to its high sensitivity to efficiency deviations of each turbine subsystem (turbine internal efficiency, condenser cleanliness, regenerative heaters’ cleanliness, etc.). However, despite this high sensitivity, the turbine heat rate cannot be used directly without implementing the sophisticated statistical techniques mentioned above because: • relatively small variation of the calculated heat rate over the entire turbine load range (only about 3%); • the presence of systematic and random measurement errors; • low signal/noise ratio as a result of the above items. In order to develop the techniques mentioned above, a detailed study of the error characteristics and error propagation was carried out. This study defined the problems which had to be solved in order to achieve an acceptably high precision of the calculation results. The current results allow using turbine heat rate as a tool for the following purposes: • turbine cycle efficiency estimation for all modes of operation and for turbine cycle scheme variations; • turbine internal condition estimation; • reliability control of measuring instrumentation which is used for turbine heat rate calculations; • determination of heat rate deviation which is above a preset acceptable value (heat rate “out of range”). The structure of the developed system is presented as well as examples of results which show the calculation precision. Also, examples are presented to illustrate how the heat rate can be using for identification of various abnormal situations which may impact the turbine cycle efficiency.
A novel high flow rate gas-assist atomizer for liquid atomization was developed. The method of liquid supply in the zone of maximal air velocity is used. It is shown that it is possible to achieve fine atomization as the relative velocity between gas and liquid is very high. However actual sprays have droplets with larger size due to the rapid decrease of the difference between air and liquid velocities. So droplets disintegrate mainly due to the turbulent velocity fluctuations of the air flow. The experimental study included two stages: laboratory tests and field tests inside a full size boiler of a 220 MW power station. At the first stage, several atomizer modifications were tested using water and compressed air. Droplet size was measured by a special Laser Light Scattering method. Liquid flow rate was equal to 3500 kg/hr. The liquid atomization quality at each cross-section of the spray was estimated by measuring the liquid-droplets sizes at several stations across the spray. The tests were carried out for two distances, 30 and 40 cm, downstream of the nozzle. The tests show that for the proposed atomizer droplets SMD was reduced from 135 to 67 microns. Droplets SMD maintains constant value when liquid flow rate is reduced by 50%. The spray angle was kept as in a standard atomizer and equal to 110 degrees under all operating conditions. It was found that to obtain this angle, the pressure downstream of the nozzle core should be atmospheric. The atomizer with the best performances was selected for the field tests. It was assumed that the atomizer which shows the best results for air-water mixture would be superior also for steam-fuel mixture. Field tests of the atomizer within the burner of an actual power station in Israel (boiler by Babcock Borsig Company), demonstrated a significant reduction in NOx content, from 540 to 270 ppmv as well as better service conditions.
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