The Research Of The Relation Between Pressure Rate And Flow And The Target Value Of The Thermal Parameters Under Variable Working Conditions Of Steam Turbine

At present, with the demand of the energy has become more and more tensional, the demand of the electricity is increasing, and the contribution to the electricity has also been changed, the steam turbine unit is often in non-designed condition, even more in the condition which is far away from the designed condition. Meanwhile, the issue on the saving-energy in the power industry has been paid more and more attention. Therefore, the varying condition of the steam turbine should be calculated carefully in order that the operating economy of the steam turbine is gotten in the change of the condition in order to optimizing the operation which also can save energy and lower the energy consumption. However, the lag of the theory on the varying condition of the unit has become one of the main restricting factors of affecting the economical operation of the safety of the power plant and realizing the modern management.The basis of calculation of varying behavior of steam turbine is stage varying behavior. It is impossible to calculate the varying condition of the stage with the unified analytic function. First, the relation of the nozzle pressure ratio,the stage pressure ratio and the stage flow was studied, and the stage can be dividedâ… ,â…¡and 0 type stage with that the nuzzle reached critical state first or the blade reaches critical state first in the condition of stage initial parameter remains the same and stage back pressure lowers gradually. And the relation of the type of the stage and the design geometric parameter of the stage was studied in utility varying condition range, further more, the stage critical pressure ratio and the stage group critical pressure ratio can be got, then we can judg whether there is a critical stage inside the stage group by the stage pressure ratio of the stage group.In this paper, the nozzle PENGTAIMEN coefficient was substituted by the stage PENGTAIMEN coefficient in the varying condition calculation for simplifying the calculation. That was not influence the efficiency of the steam turbine nearly, it was wholly appliance in project calculation. The correctness of the Flugle formula using the stage critical pressure ratio was verified in this paper, we can find that the formula not only can be used in the intermediate stage, but also can be used in the final stage of the steam turbine (not supercritical condition). And the calculation error was very tiny; the calculation accuracy was very high.The sequence varying condition calculation of the intermediate stage can be made with the improved Flugle formula. As for the calculation of the exhaust enthalpy, we give a sequential varying condition calculation that starts with steam extraction of the final stage or the second final stage (superheated steam condition). According to the initially assumed final stage flow, and the thermodynamic parameters before the final stage, also the backpressure, we can distinguish the flow patterns of the stage by a discriminant criteria. Then we can conduct a stage varying condition calculation of primary stage in sequence from the front final stage parameter, so the new exhaust steam enthalpy and the exhaust steam dryness can be got. So the precise exhaust enthalpy can be got easily.Finally, in this paper, the optimizing initial steam pressure of the unit can be gotten in the different operating condition, through fixing the operating target value of operating parameter of thermodynamic system in the varying condition in the power plant, and combining the thermo-economy state equation, and putting it to the sequence varying condition calculation to get the operating target value of the parameter of all levels. The calculating way mentioned above also can be applied into the performance calculation and the analysis of the energy consumption of SIS, through which the main economy indexes of thermodynamic system can be calculated on line, and the operating parameter of affecting the thermo-economy of unit can be supervised and analyzed continuously. The distribution of the loss of energy of the unit can be diagnosed on-line, and we calculate the loss of energy and analyses the cause of that, it will make the steam turbine operated economically.