Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

Abstract

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

On the effect of geometry of w-wave trenches on film cooling performance of gas turbine blades

“…As mentioned earlier, the boundary conditions also followed the work by Zhang et al. 32 The inlet boundary condition of mainstream is appointed velocity inlet of 20 m/s, and its temperature is maintained constant at 300 K. The mainstream outlet is defined as a pressure outlet equal to 1 atmosphere, and the coolant stream coming from plenum is set as mass flow inlet, with a temperature of 320 K. The turbulence intensity for both velocity and mass flow inlet is specified by 3%. Three different blowing ratios are considered with a range of M = 0.5, 1.0, and 2.0.…”

“…The computational domain parameters and boundary conditions for validation and novel trenches in the current paper are based on the information provided by Zhang et al. 32 The w-wave trench with amplitude 5 configuration is shown in Figure 1, and the plotted graphs used in the design of the trenches are illustrated in Figure 2. The computational domain consisted of three parts, labeled mainstream , film cooling hole , and coolant plenum , as portrayed in Figure 3.…”

“…The hole pitch (P) is 3 D, and the distance between the trailing and leading edges of the trench with each edge of the hole is 0.05 D. The w-wave trench configurations comprised the simple w-wave trench, variable radius fillet (VRF) and the traditional trench, as conducted in the work by Zhang et al. 32 Moreover, the research made use of simulated framework for surveying validation of result with experimental data conducted by. 11,31 The width of w-wave trench in all amplitudes is constant at 2.1 D. The trench depth (H) is 0.75 D, and the trench amplitude curves are 0.5 D, 1 D, and 1.5 D.…”

“…Their efforts led to improved cooling performance due to the broader spreading of coolant based on an anti-counter-rotating vortex pair (anti-CRVP), caused by their specific design of trench. The double-wave trench was tested by Zhang et al., 32 who studied three different trench widths at several blowing ratio conditions, compared with a conventional trench. The results indicated that the tested trenches enormously enhanced the film cooling effectiveness at a high blowing ratio, and the uniformity of jet at trench downstream was improved due to the favorable effect of anti-counter-rotating vortices that caused better jet attachment.…”

Parametric Studies of Laminated Cooling Configurations: Overall Cooling Effectiveness

“…The results [1,2] show that the improvement of film cooling effectiveness is mainly to restrain the development of the kidney vortex and reduce the normal penetration ability of cooling jet to the mainstream. In the novel film cooling schemes, researchers have designed combined-hole [3,4], antivortex hole [5,6], trench [7,8], and ridge-shaped tabs [9,10] to suppress the strength of the kidney vortex. However, with the development trend of gas turbines, the combustor outlet temperature continues to increase for higher recycling efficiency, and the single cooling method cannot fulfill the requirements.…”