Abstract The two-by-one (2 × 1) combined-cycle gas turbine (CCGT) unit with condensation-extraction-backpressure (C-E-B) steam turbine has become the major means of peak regulation in China because of its flexible operating mode. However, mode switching of the unit often causes drastic fluctuation of the water level of heating network thermos-exchanger and jeopardizes unit safety. In order to study the suppression mechanism of the water level fluctuation in the transient mode of switching, first a dynamic mathematical model of the thermal-supply system of the C-E-B steam turbine is developed based on a mixed approach of theory and identification. Then field data is used to verify model accuracy. Through step response analysis on the heat-supply system, the relationship between the extraction flow to the thermos-exchanger and its water level is identified along with the major influential factors. On the heat-demand system, the circulating water flow through heating network influences the heat transfer of thermos-exchanger, the exhaust steam pressure of turbine, the extraction flow and the water level in sequel. Combining the factors from the two systems arrives at the conclusion that the circulating water flow stabilizes the water level during mode switching process and provides theoretical basis for water-level controller design.

中文翻译：

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二乘一联合循环汽轮机机组供热系统动态建模

摘要 凝汽-抽-背压（CEB）汽轮机二乘一（2×1）联合循环燃气轮机（CCGT）机组因其运行方式灵活，已成为我国调峰的主要手段。然而，机组的模式切换往往会造成热网热水器水位剧烈波动，危及机组安全。为了研究瞬态切换模式下水位波动的抑制机制，首先基于理论与辨识的混合方法建立了CEB汽轮机供热系统的动态数学模型。然后使用现场数据来验证模型的准确性。通过对供热系统的阶跃响应分析，确定了热水器的抽气流量与其水位之间的关系以及主要影响因素。在供热系统中，循环水流经热网，影响换热器的传热、汽轮机的排汽压力、抽汽流量和水位。结合两个系统的因素，得出循环水流量在模式切换过程中稳定水位的结论，为水位控制器设计提供了理论依据。