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Numerical Investigation of the Combination of Effusion and Film Cooling Effects on Gas Turbine Cooling

Sheikhlari, Sepehr | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50512 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Javadi, Khodayar
  7. Abstract:
  8. Increasing the efficiency of gas turbines is directly related to the increase in the inlet gas temperature. There exist, however, limitations on increasing the temperature of the inlet gas, such as materials and metallurgy restrictions. There have been numerous methods to overcome and lessen these restrictions. In fact, two conventional ways proposed so far, are film cooling and effusion cooling. In fact, film cooling is used in many applications to reduce convective heat transfer to a turbine blade surface. In addition, Effusion-cooling is the next logical step in gas turbine blade cooling in which the flow through effusion-cooling holes is, due to their small size and the lesser amount of coolant, normally laminar which as a result plummet the temperature of the blades. The current study aims to investigate the cooling performance by combined jets of film cooling and effusion cooling by numerical simulation. In this study a new type of cooling jet, called the Horseshoe jet, has been introduced and investigated in hot sections of a gas turbine. It is worth mentioning that these types of jets are developed based on triple jet combinations and are first considered numerically. In this project, five combined effusion and film cooling jets (CEF U Type, CEF + Type, CEF 24, CEF 18, CEF 32) in three blowing ratios of 0.25, 0.5 and 1 and a film cooling jet (Horseshoe) in three blowing ratios of 0.5 1 and 1.5 have been simulated. Additionally, the cross-flow velocity in the base state was 11 m/s and the jet outlet velocity was 5.5 m/s. ANSYS Fluent software package was used to simulate the jet of interests. The results of this study indicate that the use of film cooling and effusion cooling jets compared to combined triple jets, in two blowing ratios of 0.25 and 0.5, generally improves the cooling efficiency and also elevates the uniformity of cooling. It was also observed that the abovementioned jets were unstable in the blowing ratio of 1; and thus, they were swirled and conveyed spirally downward, and the result of the cooling efficiency in this blowing ratio was inappropriate. In the study of the Horseshoe jet, it was also found that compared to other jets designed, these jets had the best cooling effectiveness in two blowing ratios of 0.5 and 1
  9. Keywords:
  10. Film Cooling ; Gas Turbines ; Effusion Cooling ; Cooling Effectiveness Coefficient ; Cooling Uniformity Coefficient

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