联合循环热电联产机组变工况性能分析

Study on Off-Design Characteristics of Combined Heat and Power Based on Combined Cycle Gas Turbine Units

随着天然气在中国能源结构中的比例不断上升,以燃气轮机为基础的联合循环热电联产技术将获广泛应用。以压气机的逐级叠加法和透平的分段冷却模型为基础,结合传统三压余热锅炉模型,提出了从中压缸排汽抽汽供热的方式,建立了联合循环热电联产系统。研究了不同抽汽系数下,系统各种效率和指标,如发电功率、总能利用系数和热电比等,随燃气轮机负荷的变化情况;不同进气可调导叶(inlet guide vane,IGV)开度下,上述效率和指标随抽汽系数变化情况;并提出了最大和最小抽汽限制曲线,得出了机组可运行区间。以MPCP1-M701F机组为对象,研究表明:随燃气轮机负荷的减小,各效率值逐渐减小,且速度逐渐加快,联合循环功率和供热量逐渐变小,基本呈线性关系,热电比逐渐变大,且速度逐渐加快;随着抽汽系数的增大,各效率值逐渐增大,除了电效率速度逐渐加快,其他基本呈线性关系,联合循环功率逐渐变小,供热量逐渐变大,两者基本呈线性关系,热电比逐渐变大,且速度逐渐加快。

As the rising proportion of natural gas in China energy structure, combined heat and power （CHP） systems based on combined cycle gas turbine （GTCC） are expected to have wide applications. A CHP system based on GTCC, which combines triple-pressure heat recovery steam generator （HRSG） and extracts steam from the intermediate pressure turbine exhaust, was proposed. A stage-stacking method was used for compressor, and a stage-by-stage model including blade cooling was adopted for the turbine. Off-design characteristics of different efficiencies and indictors, such as electrical power, total energy utilization efficiency and heat to power ratio, at various steam extraction ratio values, were studied. Besides, the effect of steam extraction ratio, at different inlet guide vane （IGV） degree, on those efficiencies and indictors was discussed. Maximum and minimum steam extraction ratio values at different IGV degree were calculated. For the MPCP1-M701F units, the results show that, as gas turbine load decreases, all efficiencies decrease and the variation rates increase, electrical power and heat load decrease linearly, heat to power ratio increases and its rate increases too; as steam extraction ratio increases, all efficiencies increase linearly, electrical power decreases whereas heat load increases linearly, heat to power ratio increases and its rate increases.