A data processing technique for steam turbines
The author describes an application of state estimation techniques to the power plant steam turbines as an alternative to computers. The steam turbine state estimator is applied to a 250 MW, double flow, single-reheat cross-compound steam turbine with seven feedwater heaters. The turbine system has 18 state variables. The state estimator is tested under a wide range of measurement noises and measurement redundancy ratio (measurement redundancy ratio is defined as the ratio of the number of measurements to that of the number of state variables). Results show the state estimator significantly improves the measurement accuracy. A data processing technique for steam turbines
Based on this model, a calculation method for the safe operation of the steam driven draft fan is proposed. Taking a 600 MW steam driven induced draft fan system as the research object, the optimal static blade opening of the induced draft fan under different loads is calculated in detail, and its control strategy was optimized. A coordinated control of open-loop control of blade opening and closed-loop control of rotation speed is proposed. It is calculated that under the new control strategy, the operational safety of the induced draft fan system has been significantly improved.
The induced draft fan is an important auxiliary machine in the coal-fired power unit, and it is also a large consumer of plant power. The steam driven induced draft fan adopts a small turbine instead of a high-power motor as the drive mechanism, which can greatly reduce the electricity consumption rate of the plant [1], furtherly reduce the impact on the plant service power system during the start-up process of the induced draft fan, and improve the security and stability of the plant service power system [2]. As the induced draft fan is driven by a steam turbine, variable speed control can be used during variable operating conditions which can reduce fan energy loss.
The key to the problem of overspeeding of small turbines is to determine the limit opening of the induced draft fan for the overspeed limit of the small turbine. The overspeed regulating boundary can be demarcated at a rotational speed of 1 001 rpm on the operating characteristic curve of the steam induced draft fan, and the corresponding static blade opening is the theoretical minimum opening degree of the single machine flow, as shown in formula
Due to the high risk of blower surge, the fan surge is not allowed during the actual operation of the unit. Therefore, it is necessary to provide early warning information when the fan operating point is close to the surge boundary to ensure the safe operation of the fan. As shown in Figure 4-1, in order to ensure the safe and stable operation of the fan, a warning line can be obtained by moving the surge boundary line to the lower right by a certain distance, which can be called the surging warning
line.
The overspeed risk of small turbine and fan surge are two types of typical safety problems faced by the operation of the steam driven induced draft fan system. In order to effectively solve the safety problems faced by the steam induced draft fan system, this paper establishes the safety evaluation model of the steam driven induced draft fan system based on the characteristics of induced draft fan. Based on this model, a calculation method for the safe operation of the steam driven draft fan is proposed. Taking a 600 MW steam driven induced draft fan system as the research object, the optimal static blade opening of the induced draft fan under different loads was calculated in detail, and its control strategy was optimized. A closed-loop speed control strategy for stationary blades was
proposed.