Abstract:Aero-thermal optimization on multi-rows of film cooling over a flat plate has
been performed to optimize the inclination angles. Hence three cylindrical
holes with injection angles of ?, ?, and ? have been considered. The cooling
hole has a 3 mm diameter and an inclined angle between 25 to 35 degrees.
Numerical simulations were performed at a fixed density ratio of 1.25 and
blowing ratio of 0.5. The control-volume method with a SIMPLEC algorithm has
been used to solve the steady-state RANS eq… Show more
“…On the other hand, some researchers in the field of film cooling have used the symmetry boundary condition to model a hole and its surrounding area. 24–27 Figure 6.Domain of numerical solution, boundary conditions of problem, and grids near the film holes.…”
Section: Numerical Simulationmentioning
confidence: 99%
“…On the other hand, some researchers in the field of film cooling have used the symmetry boundary condition to model a hole and its surrounding area. [24][25][26][27] For the mainstream, velocity was considered to be 5.9 m/ s and mass flow rate of the injection cooling air is varied with blowing ratios of M = 0.5, 1, 1.5, 2.4, and 3, and frequencies of f=2, 10, 50, and 100 Hz, corresponding to…”
In this paper, the influence of pulsating air on film cooling of a flat plate at different frequencies and blowing ratios are experimentally and numerically investigated. Square wave pulsed flow is generated at four frequencies of 2, 10, 50, and 100 Hz corresponding to Strouhal numbers of 0.00254, 0.0127, 0.0636, and 0.1271, respectively, and at five blowing ratios of 0.5, 1, 1.5, 2.4, and 3. Reynolds-averaged Navier−Stokes equations are resolved to analyze the coolant film effectiveness based on parameters set in the experiments. The [Formula: see text] model used for turbulent modeling. The obtained results showed that the performance of pulsating cooling decreases with increasing of blowing ratio at the same flow as steady state conditions. The difference between numerical and experimental values for the centerline film effectiveness shows good adaptation at the distances of the injection hole downstream. The lift-off of the local jet increased under pulsation. Increasing the pulse frequency increases the overall efficiency of film cooling. The maximum mean centerline pulsating film cooling effectiveness is obtained at Strouhal number of 0.0636 and a blowing ratio of 0.5, and the minimum value is for Strouhal number of 0.00254 and a blowing ratio of 3. For pulsed flow, the maximum discrepancy of the mean centerline film effectiveness between experimental and numerical results was 17.82%.
“…On the other hand, some researchers in the field of film cooling have used the symmetry boundary condition to model a hole and its surrounding area. 24–27 Figure 6.Domain of numerical solution, boundary conditions of problem, and grids near the film holes.…”
Section: Numerical Simulationmentioning
confidence: 99%
“…On the other hand, some researchers in the field of film cooling have used the symmetry boundary condition to model a hole and its surrounding area. [24][25][26][27] For the mainstream, velocity was considered to be 5.9 m/ s and mass flow rate of the injection cooling air is varied with blowing ratios of M = 0.5, 1, 1.5, 2.4, and 3, and frequencies of f=2, 10, 50, and 100 Hz, corresponding to…”
In this paper, the influence of pulsating air on film cooling of a flat plate at different frequencies and blowing ratios are experimentally and numerically investigated. Square wave pulsed flow is generated at four frequencies of 2, 10, 50, and 100 Hz corresponding to Strouhal numbers of 0.00254, 0.0127, 0.0636, and 0.1271, respectively, and at five blowing ratios of 0.5, 1, 1.5, 2.4, and 3. Reynolds-averaged Navier−Stokes equations are resolved to analyze the coolant film effectiveness based on parameters set in the experiments. The [Formula: see text] model used for turbulent modeling. The obtained results showed that the performance of pulsating cooling decreases with increasing of blowing ratio at the same flow as steady state conditions. The difference between numerical and experimental values for the centerline film effectiveness shows good adaptation at the distances of the injection hole downstream. The lift-off of the local jet increased under pulsation. Increasing the pulse frequency increases the overall efficiency of film cooling. The maximum mean centerline pulsating film cooling effectiveness is obtained at Strouhal number of 0.0636 and a blowing ratio of 0.5, and the minimum value is for Strouhal number of 0.00254 and a blowing ratio of 3. For pulsed flow, the maximum discrepancy of the mean centerline film effectiveness between experimental and numerical results was 17.82%.
The cratered film-cooling hole is regarded as one of the potential
applications with high cooling performance and low cost. This study focuses
on the influence of the protrusion shape for the contoured crater embedded
in the cylindrical hole. Four protrusion shapes, i.e., arc, rectangle,
trapezoid, and triangle, are considered. The cooling effectiveness, flow
structure, and aerodynamic loss for the cratered holes at blowing ratios of
0.5-2.5 are obtained using the numerical method with the Shear Stress
turbulence model. The numerical results indicate that the arc and triangle
protrusion models provide better lateral coolant coverage and higher
area-averaged cooling effectiveness at higher blowing ratios, attributed to
the ascendant anti-kidney-shaped vortex pair. The rectangle protrusion model
provides the lowest area-averaged cooling effectiveness because the
kidney-shaped vortex pair dominates the downstream flow field. For the
aerodynamic loss, the largest total pressure loss coefficient occurs for the
rectangle protrusion model and nearly equivalent values for the other three
protrusion models. The contoured cratered holes with arc and triangle
protrusions are generally recommended.
“…There has been a constant effort in enhancing film cooling performance through novel film hole shapes such as coanda bump [6], vortex generator shapes [7], film holes embedded inside a trench [8]. Recently a study showed that the geometrical parameters involved in different hole shapes can be optimized to achieve a highest cooling performance [9].…”
The Present paper discusses film cooling behavior through numerical
simulation in the presence of a twisted tape insert inside the film hole.
The twisted tape insert imparts a swirl to the coolant flow. Coolant swirl
intensity is controlled by varying the pitch of the twisted tape resulting
in swirl numbers (S) of 0.0289, 0.116 and 0.168. The film cooling
performance is evaluated using area-averaged effectiveness and heat transfer
coefficient for blowing ratios of 0.5, 1.0, 1.5 and 2.0. Results revealed a
significant amount of improvement in averaged effectiveness with the
addition of swirl. Coolant swirl predominantly modifies the jet trajectory
resulting in a reduced jet penetration and increased lateral expansion.
Further investigation on the effect of twisted tape thickness on the coolant
distribution has been found to be negligible. Pressure losses occurring due
to the insertion of twisted tape inside the film hole is evaluated through
the coefficient of discharge which indicated the necessity of higher pumping
power than the film cooling case with no-swirl.
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