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.
Visualization of heat transfer from arrays of impinging jets
Abstract A visualization technique is used to measure the heat transfer coefficient distribution on a flat plate on which either a single jet or an array of jets impinges. Liquid crystals coated on a mylar sheet are used to locate isotherms on a heated surface. By adjusting the surface heat flux, contours of constant heat transfer coefficient are obtained.
Investigation of scatter radiation of non-circular X-ray scan trajectories
Modern interventional X-ray devices are highly maneuverable and allow complex 3D imaging trajectories. New scan trajectories enable not only optimized object sampling but also introduce new approaches for dynamic 3D imaging. In this paper, we investigated the scatter radiation of two different scan trajectories. The scatter radiation was sampled by a rail setup with dosimeters at defined positions. After data analysis, contour maps were generated which show for four exemplary heights the scatter radiation distribution. The alternative scan trajectory showed smaller dose exposures at heights correlated to upper torso and head areas of a model physician. Keywords—Image acquisition, alternative scan trajectory, circular tomosynthesis, scatter radiation distribution