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Development of Dynamic Model for Turbo Expander Performance Assessment in Unstable State of Natural Gas Distribution Network

Rezaiee, Farzaneh | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51401 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Saboohi, Yadollah
  7. Abstract:
  8. In line with the energy policies of the country, which is based on the development of the natural gas system, the natural gas transmission sector has also had a significant expansion during this period, especially in recent years. On the other hand, the promotion of energy efficiency has been a major issue in energy policies and programs. Therefore, the necessity of expanding and developing the rational use of energy has been considered more than ever. The use of energy recovery technologies will be an effective step in this regard. Owing to the wide expansion of gas pressure regulating stations in Iran and the high potential losses in pressure relief valves, substituting an expansion turbine for a pressure relief valve at gas pressure regulating stations is one of the effective steps in this regard.Considering the mentioned points, goals of the present study have been to examine the design of an expansion turbine cycle in variable boundary conditions and to provide solutions to improve the cycle performance in order to achieve sustainable performance, that is, continuous production of the system. Initially, all components of the system, including turbine, heat exchanger, boiler and pressure gauge, were designed in detail (the effect of improving the performance of a turbine with variable nozzle angles in off-design condition points could be evaluated by providing a zero-dimensional model). Results demonstrated that application of technology of the variable nozzle angle resulted in an acceptable efficiency in the range of 0.45 to 1.2 ratio of flow rate to the design point flow rate. In the next step, by integrating these components into four combinations (basic system, parallel system, system in series, and hybrid system) and by applying multi-objective optimization of thermo-economic analysis in each combination of the considered case study (the gas pressure regulating station of Ramin-e-Ahvaz Power Plant), the optimal conditions were determined on the Pareto diagram. Accordingly, in the combination of the base system, the exergy efficiency ranged from 30% to 42% and the total cost was in the range of 4 to 6 million dollars while in a combined hybrid system, the range of exergy efficiency was reported to be in the range of 30% to 38% and a total costs were estimatedto be in the range of 4 to 22 million dollars. In each Pareto diagram, three points, primary, middle and end points, were selected to introduce main features of the system components. Then, according to the information obtained from the design section, the performance of the base cycle in variable conditions over a year was investigated. Given the range of generated power of the expansion turbine at the optimal points of the Pareto diagrams, the conditions of the off-design points would be different, so if the maximum potential of the gas pressure regulating station for power generation was selected, the effect of gas fluctuations would be significant, in return
  9. Keywords:
  10. Energy Recovery ; Expansion Turbine ; Turbo-Expander System ; Pressure Reduction ; Design and off-Design Condition

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