LDA-measurements of jets in crossflow for effusion cooling applications

Abstract

There is a need for better cooling of hot parts in gas turbines. Film cooling and effusion cooling are often used in parts where there is a great heat load. However, modern numerical methods cannot predict heat transfer on film-cooled walls, where there are many rows of holes. There is thus a great need for better understanding of the topology of the flow field, the way in which different vortices interact in multiple row film cooling (effusion cooling) and how fluid packages with different densities affect the flow. Laser-Doppler anemometry was used here to examine the flow field of an oblique jet in a crossflow. The jet was located in the third row of holes. The operational parameters used in this investigation were Re _d = 6000, U _jet / U ₀ = 0.8, T _jet / T _O = 1 and ρ _jet /ρ ₀ = 1, and the injection hole was slanted at an angle of 30°. One major finding in LDA measurements in the wake was the two counter-rotating foci close to the wall. In the foci shown in figure 1, the mean velocity field changed dramatically from 0 m/s to 10 m/s in only 0.4 mm This is of the same magnitude as the wall gradient in a flat-plate boundary layer with the same free stream velocity. All Reynolds stresses are presented in several planes for the global flow field of the jet.