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Etracker-Calculation Module™
The same calculation module and Etracker-Model is used by Etracker-PE, Etracker-OLM, and Etracker-Remote.
The turbine evaluation is performed by a stage-by-stage, velocity diagram type of analysis that determines the stage response to the specific conditions of flow, pressure and temperature presented to it.
Pressure drop across the stationary blading (nozzle) determines the velocity V1. Subtracting the wheel speed W vectorially gives the relative velocity to the rotating blade V2. The velocity leaving the rotating blade V3 is determined from the entering velocity V2 and any increase in velocity resulting from pressure drop (sometimes referred to as reaction) across the rotating blade. The final velocity leaving the stage is V4
The stage-by-stage analysis, and the ability to change individual stage areas and velocity coefficients, makes possible the unique capability of Etracker programs to simulate, and determine the characteristics of, the various types of degradation that occur to steam turbines in practice.
This analysis thus can deal with user defined conditions of leakage control clearances, steam path surface finish, possible mechanical damage, deposits, erosion, etc.; and then defines the energy converted to useful power, as well as the steam conditions that are made available to the following stage, or casing exit.
The first and last turbine stages each present unique calculation challenges. Turbine throttle flow in the program is controlled by opening and closing control valves, as is the case for the real unit. For either sequential admission, or full throttling type of control, calculations are performed separately for each active portion of the first stage arc. Steam conditions leaving each portion of the arc are averaged and then sent on to the second stage.
Calculations for the last stage are similar to the other turbine stages except that the final energy in the steam going to the condenser includes any residual whirl from the stage, the axial velocity energy to get the steam away from the stage and, a user adjustable allowance for pressure drop losses in the exhaust hood. This final total exhaust energy is usually identified as the Used Energy End Point (UEEP).
Condenser calculations are performed using the heat transfer characteristics defined in PTC 12.2. Feedwater heater calculations are performed using the NTU method as described in a technical paper by John Tsou, with Electric Power Research Institute.
Pumps, and other plant equipment are evaluated using basic physics, heat transfer, and fluid flow characteristics that are significant to the component being evaluated.