Advanced Gas Turbine cycles for high efficiency and sustainable future conventional generation

燃气轮机（GT）将在补充可再生能源产生的间歇性电力方面发挥重要作用，而到2050年，各种燃料来源可能包括生物燃料（前者是甲烷，碳一氧化物和二氧化物以及氮的混合物-基本上是低热值燃料），也许还有页岩气和氢气。在实现二氧化碳排放目标方面，将对（i）具有最高燃料转化效率和（ii）与碳捕获和储存相结合的设计给予奖励。这种设计包括湿空气涡轮机（HAT）或具有大量废气或烟道气再循环以及使用富氧空气的方案。对这些设计进行了广泛的技术经济评价，没有首选的“赢家”，很可能每一种设计都将得到广泛的应用。因此，将需要设计燃烧室以燃烧低热气体，其中“氧化剂”流包括高达30%（w/w）的蒸汽、纯氧或用二氧化碳严重稀释的氧气。这种变化给火焰的稳定和熄灭带来了巨大的困难。低NOx燃烧室的设计已经显示出计算流体动力学（CFD）在开发商业上可行的设计中的价值，并且这一趋势将得到加强。最后，合适的传感器在开发过程中的价值已经证明了它的价值。这项研究确定了现有的物理理解，CFD和光学传感器的差距，需要通过“基础研究”来解决，这些差距需要填补，以便行业可以开发阶跃变化GT技术。（i）在线的、接近真实的时间的光学传感器，用于测量进入燃气涡轮机的燃料的“沃泊”指数，因为快速了解高度可变的生物燃料的热值对于控制未来的GT是重要的。(ii)火焰稳定性和熄灭与存在临界“拉伸率”和火焰由于燃烧室的空气动力学流场而可能经历的最大层流火焰速度有关。设计人员使用计算流体力学预测燃烧室中的流动，需要知道这些临界值的范围内的燃料和氧化剂，这将在使用到2050年。因此，该提案将获得这些值的测量值在预混和非预混火焰作为预热和压力的函数，并分析在实验室和试验规模的模型燃烧室中使用，除其他仪器，检测CO和甲醛平面激光诱导荧光的火焰熄灭的过程。(iii)低NOx排放要求燃料充分预混合，并且开发工程师可以使用可以在试验台上测量局部燃料/空气比的仪器。在以前成功开发的基于火焰自然发光发射的仪器的基础上，将对其作为压力和湿度函数的校准进行评估，后者在HAT燃气涡轮机设计的背景下进行。(iv)热声不稳定性是一种破坏性的高强度“极限环”，它要么在操作上避免，要么在很大程度上通过尝试和尝试的方法改进设计。直到最近，过渡到这个极限环和极限环本身的特点是频率和相位谱分析。我们最近的工作表明，非线性时间序列分析表明，过渡到高振幅振荡保留了混沌理论所确定的结构。我们将使用这种形式的分析，以确定负责这种行为的流体机械结构，目的是设计方法，至少警告即将发生的热声不稳定的气体涡轮机运营商。(v)最好的大涡模拟计算流体动力学方法将使用逆流和模型燃烧室几何形状的测量值进行评估。通过测量，还将直接评估LES方法对计算的“子网格”贡献

Gas Turbines (GTs) will figure prominently in complimenting the intermittent power generated by renewables, while varied fuel sources by 2050 are likely to include biofuels (the former a mixture of methane, carbon mono- and di-oxide and nitrogen - essentially low calorific value fuel) and perhaps shale gas and hydrogen. In meeting CO2 emissions targets, there will be a premium on designs that (i) have the highest fuel conversion efficiency and (ii) integrate with carbon capture and storage. Such designs include either humid air turbines (HAT) or schemes with extensive exhaust, or flue, gas recirculation together with the use of oxygen-enriched air. There is extensive techno-economic evaluation of these designs with no preferred 'winner' and it is likely that each will find extensive application. Thus, there will be a need to design combustion chambers to burn low calorific gases, with "oxidant" streams including up to 30% (w/w) of steam, pure oxygen or oxygen heavily diluted with Carbon dioxide. Such changes present formidable difficulties to flame stability and extinction. The design of low NOx combustion chambers has shown the value of computational fluid dynamics (CFD) in developing commercially viable designs and this trend will strengthen. Finally, the value of suitable sensors during development has proved its worth. This research identifies the gaps in existing physical understanding, CFD and optical sensors, to be addressed by "fundamental research", that need to be filled so that step change GT technologies can be developed by industry. This proposal will develop tools and understanding as follows:(i) On-line, near real time optical sensor to measure the 'Wobbe' index of fuel entering the gas turbine, since fast knowledge of the calorific value of highly variable bio- fuels is important for control of future GTs.(ii) Flame stability and extinction is associated with the existence of a critical 'rate of stretch' and the largest laminar flame speed that the flame can experience due to the aerodynamic flow field of the combustors. Designers, using CFD for flow prediction in combustion chambers, need to know these critical values for the range of fuels and oxidants, which will be in use up to 2050. Thus, this proposal will obtain measurements of these values in premixed and non-premixed flames as a function of preheat and pressure and analyse the process of flame extinction in laboratory and pilot scale model combustors using, amongst other instruments, detection of CO and formaldehyde by planar laser induced fluorescence.(iii) Low NOx emissions require the fuel to be well premixed and it is useful for development engineers to have access to an instrument, which can measure local fuel/air ratio on test stands. Building on previous successful development of an instrument based on natural chemiluminescent emissions from a flame, there will be an evaluation of its calibration as a function of pressure and humidity, the latter in the context of a HAT gas turbine design.(iv) Thermoacoustic instability is a destructive high intensity 'limit cycle', which is either avoided operationally or designs are improved largely by cut and try methods. Until recently, the transition to this limit cycle and the limit cycle itself were characterised by frequency and phase spectral analysis. Our recent work has shown that non-linear time series analysis reveals that transition to high amplitude oscillations retains a structure as determined by chaos theory. We will use this form of analysis to identify the fluid mechanical structures responsible for this behaviour, with the aim of devising methods to at least warn gas turbine operators of impending thermoacoustic instability.(v) The best available LES CFD methods will be evaluated using the measurements in the counterflow and model combustor geometries. There will also be direct assessment, through the measurements, of the 'sub-grid' contribution of LES methodology to calculations