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The operational optimisation of coal-fired power units is important for saving energy and reducing losses in the electric power industry. One of the key issues is how to determine the benchmark values of the energy efficiency indexes of the units. Therefore, a new framework for determining these benchmark values is proposed, based on data mining methods. First, the energy efficiency key performance indicators (KPIs) associated with the net coal consumption rate (NCCR) were selected based on the domain knowledge. Second, the decision-making samples with minimal NCCR were acquired with the fuzzy C-means (FCM) clustering algorithm, and the corresponding clustering centres were employed as the benchmark values. Finally, based on the support vector regression (SVR) algorithm, the target values of the NCCR were obtained with the KPIs as input, and the energy saving potential was evaluated by comparing the target values with the historical values of the NCCR. An actual on-duty 1000 MW unit was taken as study unit, and the results show that the energy saving potential is remarkable when the operators adjust the KPIs based on the calculated benchmark values. [ABSTRACT FROM AUTHOR]

With the development of new-power generation sources, the difference between maximum and minimum power requirements from a power grid is growing. However, the peaking power installed capacity, such as pumped-hydro energy storage and gas-fired power, is too small to meet the peaking regulation requirements. Chinese coal-based energy resources structure determines coal-fired power plants to be the main source of power. This means that coal-fired power units will need to undertake more peak shaving tasks for a long period of time. In this paper, we provide an overall review of China׳s coal-fired power units׳ peak regulation with a detailed presentation of the installed capacity, peak shaving operation modes and support policies. High energy-consumption problems, environmental pollutants and safety barriers when coal-fired power units run in low-load operation are noted from the power generation perspective. Some policy recommendations are given to solve the peak shaving problem to some extent and to ensure the sustainable development of the power energy system. [ABSTRACT FROM AUTHOR]

The seal aerodynamic characteristics of supercritical carbon dioxide (SCO 2) are significant. The whirl model of two-control equation was established by splitting the original one-control equation to adapt to the mesh deformation of SCO 2 seal. The NIST REFPROP SCO 2 (real gas properties) was used as the working fluid to simulate the seal dynamic characteristics of SCO 2 turbine accurately. The effects of different fluids, rotational speeds, pressure ratios and whirl types on seal dynamic characteristics were compared and analyzed. The results show that the UDF of two-control equation can improve the simulation accuracy of seal. The pressure ratio, rotational speed and conical whirl motion all affect seal dynamics, in which the conical whirl motion is significant and makes seal dynamic stability poor. • An improved whirl model of two-control equation was developed. • The NIST REFPROP SCO 2 (real gas properties) was used as the working fluid. • The effects of multiple factors on seal dynamics were compared and analyzed. [ABSTRACT FROM AUTHOR]

A multi-frequency conical whirl model was established to investigate the influence of different rotor whirling motion on seal steam flow excited vibration and dynamic characteristics. The simulation method of rotor motion was improved to adapt the ultra-supercritical steam turbine, in which the whirling motion and rotational motion were decomposed by user-defined function (UDF). The seal steam flow excited vibration and dynamic characteristics of parallel whirl motion, semi and full conical whirl motion were present. The influences of different rotor motion were analyzed via pressure waveform. The dynamic coefficients have the obvious variation in semi and full conical whirl motion. The expansion profile of seal cavity caused by conical whirl motion makes the fluctuation range of circumferential pressure great. • A multi-frequency conical whirl model was established by user-defined function. • Seal dynamic characteristics of different rotor whirl motion were presented. • Characteristics of pressure fluctuation in conical whirl motion were analyzed. [ABSTRACT FROM AUTHOR]