چكيده به لاتين
One of the applications of gas turbine is driving a compressor or pump to transfer fluids especially in oil and gas industry. In Iran, the majority of turbocompressors are also used to compress the gas for pipeline transportation and also to inject gas into wells. Gas turbine Performance loss in off design conditions is one of the main problems which in order to improve it the behavior of gas turbines must be identified. Although rig tests can be used to identify the behavior of gas turbines, modeling of the process saves the costs and time. Thereby, modeling is widely used todays to imitate the behavior of gas turbines for the purpose of improving or monitoring the performance. Among the available modeling techniques, thermodynamic method is quick and relatively less precise. In the present work, a ‘DU80’ turbocompressor with three shaft gas turbine and two connected gas compressors is modeled thermodynamically. In this type of modeling, every component of gas turbine is considered as a control volume and thermodynamic equations are written for them. In order to increase the accuracy, each part of the compressor or turbine with different characteristics was considered as a separate control volume. Ultimately by establishing matching equations between the control volumes at the steady state, the turbocompressor was modeled in off design conditions. The result shows less than six percent error when validated with reference data which is acceptable. As the final stage of modeling, changes in influential parameters of gas turbine such as the inlet air mass flow rate, the outlet temperature of combustion chamber and the gas turbine efficiency versus ambient temperature and power turbine rotational speed have been investigated. Result analysis shows that by increasing gas compressor flow rate or outlet pressure, gas compressor rotational speed and load would increase and inlet air flow rate, fuel flow rate and air compressor rotational speed would increase subsequently.
Key words: Thermodynamic modeling, Three shaft turbocompressor, Gas injection, DU80
