The effect of turbulence intensity on film cooling of gas turbine blade from trenched shaped holes

Abstract

This paper reports a computational investigation on the effects of mainstream turbulence intensity on film cooling effectiveness from trenched holes over a symmetrical blade. Computational solutions of the steady, ReynoldsAveraged Navier-Stokes equations are obtained using a finite volume method with k -e Turbulence model. Whenever possible, computational results are compared with experimental ones from data found in the open literature. Computational results are presented for a row of 25°forward-diffused film hole within transverse slot injected at 35°to AGTB symmetrical blade. Four blowing ratios, M = 0.3, 0.5, 0.9 and 1.3 are studied together with four mainstream turbulence intensities of Tu = 0.5, 2, 4 and 10%. Results indicate that the trenched shaped holes tend to give better film cooling effectiveness than that obtained from discrete shaped holes for all blowing ratios and all turbulence intensities. The trenching of shaped holes has changed the optimum blowing ratio and also the location of re-attachment of separated jet at high blowing ratios. Moreover, it has been found that the effect of mainstream turbulence intensity for trenched shaped holes is similar to that obtained for discrete shaped holes with the exception that the sensitivity of film cooling effectiveness to turbulence intensity has decreased for trenched shaped holes. List of symbols DDiameter of coolant channel cross section at throat k Turbulent kinetic energy L/D Length-to-diameter ratio of film hole M Blowing ratio = ðqUÞ c =ðqUÞ 1

The Effect of Blowing Ratio on Film Cooling Effectiveness Using Cylindrical and Row Trenched Cooling Holes with Alignment Angle of 90 Degrees

“…They also concluded that the adiabatic effectiveness with the narrow trench was relatively constant across this range of blowing ratios. However, these results were inconsistent with Harrison et al [15], Shuping [16], Baheri Islami and Jurban [17], and Lu and Ekkad [18], which stated that when the blowing ratio increased from 0.6 to 1.4, the performance of the trench was three times greater than that for baseline cylindrical holes. Recently, Ai et al [19] proved that trenching reduced the coolant momentum ratio and impaired the effectiveness while traditional cooling holes performance was better at low blowing ratios.…”

Numerical study of film cooling effectiveness of a gas turbine blade under variable blowing ratio and turbulence intensity

“…Most research has been done by the RANS approach with the k –$$\varepsilon $$ turbulence method to simulate the film cooling of the typical blades 12 . The main parameters involved in the film cooling phenomena (blowing ratio, turbulence intensity, hole angle, hole geometry, in stagger and in‐line hole arrangement, hole to hole distance, coolant velocity, and temperature) are examined in various studies 13–25 …”

“…Saumweber et al 23 experimentally studied the film cooling effectiveness by applying two different turbulence intensities on shaped holes. Baheri Islami et al 24 conducted the influence of four different turbulence intensities (0.5%, 2%, 4%, 10%) and blowing ratios ( M = 0.3, 0.5, 0.9, 1.3) on film cooling performance of trenched holes' shape on AGTB blade. Their results showed that trenched‐shaped holes for all ranges of blowing ratios have better film cooling performance.…”

Vortex identification and evolution of a jet in cross flow based on Rortex

“…In the downstream of a single row of film cooling holes, the cooling effectiveness drops due to the mixing of mainstream and coolant flow. Meanwhile, most of the film cooling correlations in published literatures were mostly focus on the blowing ratio (BR), inclined angel, the shape of the hole and so on (Goldstein et al, 1974;Gritsch et al, 1998;Hasan et al, 2003;Heidmann & Ekkad, 2008;Islami & Jubran, 2012;Islami et al, 2010;Khajehhasani & Jubran, 2016;Ming Li & Hassan, 2015;Yuen & Martinez-Botas, 2003). In the film cooling process, abundant vortex structures are generated and transported owing to the interaction between the jet flow and the cross flow (Kelso et al, 1996).…”