چكيده به لاتين
Abstract:
An appropriate and accurate control system is essential for optimum and safe performance of a gas turbine engine. However, for efficient design of a control system, various performance parameters of the gas turbine engine are required. Since experimental tests on real engines are too expensive, a reliable and accurate engine model can be quite effective. On the other hand, some instabilities like surge and stall phenomena may be occurred during turbine engine operation. So, it is important to study these phenomena to avoid their occurrance. One of the most important and known methods for this purpose is to use variable bleed valves (VBVs) in some compressor stages. Hence, compressor stage-by-stage modeling is necessary for studying the possibility of these instabilities occurance and the effect of using bleed valves on the turbofan engine performance.
In this thesis, turbofan engine modeling using stage-by-stage compressor characteristics is performed. Firstly, a thermodynamic modeling of an unmixed two-spool high-bypass ratio turbofan engine is done based on a global approach without considering stage-by-stage compressor specifications. High pressure (HP) and low pressure (LP) compressors are then divided into the number of their stages and a stage-by-stage turbofan engine model is developed. The results of the stage-by-stage simulation show the occurrence of instability in HP compressor operational range. In addition, the outcomes indicate the necessity of using control systems like VBVs in this turbofan engine to prevent surge and stall phenomena. Finally, the effect of air bleeding from one of the HP compressor stages on compressor and engine performance is discussed where the compressor move away from the surge region.
Keywords: Gas Turbine, Turbofan Engine, Thermodynamic Modeling, Stage by Stage Model
