Flow analysis of combined impingement and film cooled gas turbine nozzle guide vane
In the present study, a typical nozzle guide vane (NGV) is considered with twenty six rows of impingement holes combined with thirteen rows of film cooled rows for the flow analysis. The coolant mass flow variations in different rows of the film holes externally subjected to the hot main stream are obtained by making a three dimensional computational analysis of NGV. The analysis is performed with the help of Fluent software. Attempts were made to study the effect of two parameters: (i) inlet coolant mass flow rate and (ii) external flow Reynolds number for a typically cooled NGV. Detailed coolant flow mass flow rate, pressure drop and temperature distributions are presented with an array of multiple jets impinging on a gas turbine high pressure NGV with a staggered array of film cooled rows. Results are presented for three laboratory test cases by varying flow rates for FIT and AIT. Coolant flow rate values at each row of film hole are compared among these test cases. The each row of a film hole is noticed with coolant mass flow rate, pressure drop and temperature rise across the hole found to increase with increase of coolant supply conditions at the two plenums. Owing to the interaction between hot main stream and the coolant that effuses out of the film holes, occasional presence of hot gas ingestion is noticed for certain flow rates. This causes nonlinear distribution in mass flow, pressure drop and temperature rise. These behaviors suggest a possibility of locally optimized solutions for a combination of coolant mass flow and mainstream Reynolds number.
Heat Transfer Distribution of Semicylindrical Concave Surface Impinged by Circular Jet Rows
The impingement cooling of the leading edge of a gas turbine airfoil is modeled by considering impingement of three rows of jets on a semicylindrical concave surface. Experimental investigations are conducted to study the influence of jet-to-jet distance (s/d = 2.83, 4, and 6) and jet-to-plate distance (z/d = 2, 4, 6, and 8) on the local heat transfer of a semicylindrical concave surface impinged by three rows of multiple jets for different Reynolds numbers (12,000, 15,000, and 18,000). The local heat transfer coefficient is estimated using thermal images obtained by infrared thermal imaging technique. The local distribution of Nusselt numbers and the overall average Nusselt numbers were computed and compared. It was observed that the local heat transfer coefficients at 0 = 0° decrease with increase in z/d, whereas the heat transfer coefficients at θ = 60 and 80° increase with an increase in z/d at all Reynolds numbers. The configuration with s/d = 2.83 and z/d = 4 is observed to have the maximum heat transfer distribution with minimum coefficient of variance compared to other configurations at all Reynolds numbers covered in this study.
Substation automation based on IEC 61850 with new process-close technologies
New technologies in primary equipment like nonconventional instrument transformers require new interfaces to the substation automation system. The future standard IEC 61850 perfectly supports this requirement. With the introduction of the new technologies and the use of IEC 61850, a more decentralized architecture of the substation automation system will be possible. This provides several benefits but a careful system design is required to maintain the overall reliability of the system.