Renewable energy sources (RES) have become a favoured alternative to fossil fuel energy generation that has been driven by environmental concerns. Their intermittent nature has meant that gas turbines have remained relevant to support them as a backup. Current grid operation requires gas turbines to operate at as low power as possible when their demand drops, and also ramp-up quickly when power generation from renewables declines. Air extraction from a gas turbine compressor can address the first requirement, as this mechanism reduces the load or power of the engine while storing the air for further pressurised reinjection, related to ramp-up rate improvements. This study demonstrates the aerodynamic implications and the limits to air extraction behind the last stage of the compressor, to achieve further minimum load reduction. To achieve this, a zero-dimensional (0D) analytical model of an engine at design and off-design conditions (air extraction) has been used to determine the boundary conditions for a 3D compressor Computational Fluid Dynamics (CFD) model. The multi-stage CFD model shows the aerodynamic implications of low to high air extractions that are limited by choke, high flow separation, and loss in the pressure at the hub region of OGV and last stage stator. As such, the back of the compressor was more affected than the earlier stages. Based on these, the limit of flow extraction is 18% (of the compressor discharge). The compressor of the analytical engine model showed similarity in trends for comparable conditions with the stand-alone 3D compressor, however, more optimistic than the latter. The work has shown that the compressor is capable of high airflow extractions to reduce the minimum load further.

可再生能源（RES）已成为受环境问题驱动的化石燃料能源生产的替代方案。它们的间歇性意味着燃气轮机一直很重要，可以作为后备设备来支持它们。当前的电网运行要求燃气轮机在需求下降时以尽可能低的功率运行，并且在可再生能源发电量下降时也要迅速增加。从燃气轮机压缩机抽气可以满足第一个要求，因为这种机制减少了发动机的负载或功率，同时存储了用于进一步增压再喷射的空气，这与提高升温速率有关。这项研究表明了空气动力学的影响以及在压缩机最后一级后面进行抽气的限制，以实现进一步的最小负荷降低。为了达成这个，在设计和非设计条件（抽气）下，发动机的零维（0D）分析模型已用于确定3D压缩机计算流体动力学（CFD）模型的边界条件。多级CFD模型显示了从低到高抽气的空气动力学含义，这些空气受阻流，高流量分离以及OGV和最后一级定子的轮毂区域压力损失的限制。这样，压缩机的后部比早期受到的影响更大。基于这些，抽气极限为（压缩机排气量的）18％。分析型发动机模型的压缩机在可比较的条件下与独立的3D压缩机在趋势上具有相似性，但是比后者更为乐观。