The Universal Calculation Model Research About Optimal Initial Pressure Of Steam Turbine Sliding Pressure Operation

The paper takes the unified physical model and mathematical model about thermo-economics analysis for thermal power generating units as basic theory and takes large condensing steam turbine generator units as the research object. On the precondition of fully analyze each thermodynamic parameters’ change regularity when the units are in sliding pressure operation, with the help of matrix partial differential theory, the initial pressure optimizing objective function which is also called calculation formula for relative change rate δq of heat consumption rate is established after strict mathematical derivation. This objective function has not only can be widely used in initial pressure optimizing question for all kinds of condensing steam turbine units, but also can comprehensively calculating the influences of each thermodynamic parameters multiple disturbance on units’ heat consumption rate, and these thermodynamic parameters include main steam pressure p0, main steam temperature t0, reheat steam temperature tzr, upper terminal temperature difference△t1under terminal temperature difference, auxiliary steam water, steam extraction steam pressure loss, etc. In order to testing the exactness of this objective function this paper take a660MW steam turbine generator unit as example, the influences of its steam admission parameters, including p0, t0and tzr, multiple disturbance to the unit’s heat consumption rate, and then the upper calculating results are compared to the heat consumption rate performance curves which are provided by steam turbine manufacturer. The comparative results prove the high-accuracy of this objective function which can contents the need of engineering applications. On the base of above, by combining the objective function’s minimizing calculation with initial pressure optimization’s constraint conditions which include the reasonable change areas of unit’s power generation loads and initial pressures, the universal calculation model about the optimal initial pressure of steam turbine sliding pressure operation is obtained. Afterwards, combining the universal calculation model about the optimal initial pressure and unit’s real operating data, the initial pressure optimizing computer program is compiled by taking heat consumption relative change rate8q’s minimum when unit is under different power generation loads as calculating target, then the minimum heat consumption rate qmin and its corresponding optimal initial pressure p0are both obtained. By adopting method above, this660MW unit’s optimal operation initial pressures and their corresponding optimal sliding pressure operation curves when this unit is under different power generating loads and the environment temperatures are in20℃and in33℃. And meanwhile, a new analysis method and application concept is presented which includes the optimal load cut-off points mapping of units’fixed pressure operation and sliding pressure operation and the optimal slopes mapping when the units are sliding pressure operation, all of these above provide a new method for guiding the optimizing operation of various thermal power generating units.