As power plant combustion turbines (CTs) are pushed towards higher thermal efficiencies, increased attention is being given to operating requirements for their fuel gas supply such as the maximum allowable rate-of-change in pressure. It is important to perform detailed analyses for multi-unit plants to ascertain whether pressure transient events, such as those caused by initial trip of one or two combustion turbines, will cause additional combustion turbines to trip off. In this paper, single and dual CT trips were postulated in a near-realistic combined cycle power plant. Predictions of the gas flow behavior, along with propagation and superposition of pressure waves, was carried out using the method of characteristics (MOC) for compressible flows. Specifically, the rate of change in fuel gas supply pressure to each CT was monitored and compared against a typical manufacturer limit of 0.8 bar/s. Instances where simulations showed this threshold exceeded were noted, since such events correspond to automatic valve closure that would shut down one more CT and thereby further reduce plant electrical output. The overall goal of fuel gas transient analyses is to improve pipeline designs, iteratively when necessary, such that those additional trips are avoided. To that end, this paper presents several simulation cases to illustrate pressure transient phenomena and to show the impact of various pipeline design alterations, some of which caused 40% reductions in the worst pressure rate-of-change during simulations.
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机译：随着发电厂的燃气轮机（CT）朝着更高的热效率方向发展，人们越来越关注其燃气供应的运行要求，例如最大允许压力变化率。对多机组工厂进行详细分析，以确定压力瞬态事件（例如由一台或两台燃气轮机的初始跳闸引起的那些）是否会导致其他燃气轮机跳闸，这一点很重要。在本文中，假设在接近现实的联合循环电厂中进行单次和两次CT跳闸。使用可压缩流的特征方法（MOC）对气体流动行为以及压力波的传播和叠加进行了预测。具体来说，监控每个CT的燃气供应压力的变化率，并将其与典型的0.8 bar / s的制造商限制进行比较。记录了仿真显示超过此阈值的情况，因为此类事件对应于自动阀门关闭，这将关闭另外一个CT，从而进一步降低工厂的电力输出。燃料气体瞬态分析的总体目标是在必要时迭代地改进管道设计，从而避免那些额外的行程。为此，本文提出了几种模拟情况，以说明压力瞬变现象并显示各种管道设计变更的影响，其中一些在模拟过程中使最坏的压力变化率降低了40％。
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