Numerical Investigation of Single-Row Double-Jet Film Cooling of a Turbine Guide Vane under High-Temperature and High-Pressure Conditions

Abstract

Single-row double-jet film cooling (DJFC) of a turbine guide vane is numerically investigated in the present study, under a realistic aero-thermal condition. The double-jet units are positioned at specific locations, with 57% axial chord length (Cx) on the suction side or 28% Cx on the pressure side with respect to the leading edge of the guide vane. Three spanwise spacings (Z) in double-jet unit (Z = 0, 0.5d, and 1.0d, here d is the film hole diameter) and four spanwise injection angles (β = 11°, 17°, 23°, and 29°) are considered in the layout design of double jets. The results show that the layout of double jets affects the coupling of adjacent jets and thus subsequently changes the jet-in-crossflow dynamics. Relative to the spanwise injection angle, the spanwise spacing in a double-jet unit is a more important geometric parameter that affects the jet-in-crossflow dynamics in the downstream flowfield. With the increase in the spanwise injection angle and spanwise spacing in the double-jet unit, the film cooling effectiveness is generally improved. On the suction surface, DJFC does not show any benefit on film cooling improvement under smaller blowing ratios. Only under larger blowing ratios does its positive potential for film cooling enhancement start to show. Compared to the suction surface, the positive potential of the DJFC on enhancing film cooling effectiveness behaves more obviously on the pressure surface. In particular, under large blowing ratios, the DJFC plays dual roles in suppressing jet detachment and broadening the coolant jet spread in a spanwise direction. With regard to the DJFC on the suction surface, its main role in film cooling enhancement relies on the improvement of the spanwise film layer coverage on the film-cooled surface.

Numerical Investigation on Backward-Injection Film Cooling with Upstream Ramps

“…When considering the turbulence enclosure, the realizable k-ε eddy viscosity turbulent model is selected, as it has been reported by many researchers to be a proper two-equation turbulence model in the prediction of film cooling performance (e.g., Ely and Jubran [48], Foroutan and Yavuzkurt [49], Zhu et al [50], Hang et al [51]). This turbulence model is also validated in our previous works [25][26][27].…”

“…The deviations between the numerical results and the experimental results are within 5% in most areas, and the maximum deviation is about 13%. Based on the works in Refs [13,20,21,[48][49][50][51] and the present validation, the realizable k-ε turbulent model is finally selected in the current study. For the computational meshes, a mixed-grids generation strategy is adopted (Figure 4) by applying unstructured grids near the SDR and structured grids in the other regions.…”

Enhancement of Film Cooling Effectiveness in a Supersonic Nozzle

“…The formation and growth of the mixing layer in the presence of the favorable pressure gradient (as in the nozzle) and pertinent aspects of the impact of the mixing zone on cooling in nozzles have not been discussed with an adequate focus in most of the previous studies. Additionally, the majority of the studies have been reported for temperatures less than 1200 K [ 31 ]. Nozzles in rocket engines are typically exposed to temperature levels in the range of 2500–3500 K. This high-temperature level constrains experimental investigations.…”

An LBM-Based Investigation on the Mixing Mechanism of Double Rows Film Cooling with the Combination of Forward and Backward Jets

“…In order to suppress the generation of CVP and weaken the associated undesirable effects, many kinds of active and passive control [8][9][10][11][12][13][14][15][16][17][18] have been proposed. Among the active control methods, the key parameters mainly include jet flow frequency [8,9], intensity of freestream turbulence [10,11], density ratio [11,12], and blowing ratio [13].…”

“…Among the active control methods, the key parameters mainly include jet flow frequency [8,9], intensity of freestream turbulence [10,11], density ratio [11,12], and blowing ratio [13]. As for passive control, geometrical shape of film cooling hole [14][15][16] and geometrical parameters of upstream obstacle [17,18] receive lots of attention. The results indicate that the application of a shaped hole or upstream obstacle can suppress the generation of CVP, and hence, weaken the lift-off of coolant jet and its undesirable effect on film cooling performance.…”