Numerical Study of Film Cooling For Various Coolant Inlet Geometries (original) (raw)
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Computational analysis has been carried out to find the film cooling effectiveness (centerline and spatially averaged) over an adiabatic flat plate. Variation in film cooling effectiveness has been determined along the downstream of the cooling holes on the flat plate. The study compares film cooling effectiveness over various blowing ratios, various hole shapes and rearrangement of holes. Here three different cooling hole shapes i.e. circular, square and fan shaped holes have been used for the present study. Numerical based solver Fluent has been used for the analysis using the standard Reynolds Averaged Navier-Stokes shear stress transport turbulence model. The numerical results reveal that the film cooling effectiveness increases with increase in blowing ratios. Beyond an optimum blowing ratio, film cooling effectiveness decreases due to coolant jet lift off and intermixing of coolant and mainstream flow at higher blowing ratio. Among the different cooling hole shapes, the best film cooling effectiveness was obtained for fan-shaped holes with blowing ratio equal to unity. Spatially averaged effectiveness for fan-shaped holes was found to be higher as compared to other hole shapes.
Numerical approach to film cooling effectiveness over a plate surface with coolant impingement
Journal of Thermal Science, 2004
ABSTRACT The aim of the present study is conducting the numerical approach to a combination of internal jet impingement and external film cooling over a flat plate. A multi-block three-dimensional Navier-Stokes code, CFX 4.4, with k-ε turbulence model is used to simulate this complicated thermal-flow structure induced by the interaction of coolant jet and hot cross mainstream. By assuming the adiabatic wall boundary condition on the tested film-cooled plate, both the local and the spanwise-averaged adiabatic film cooling effectiveness are evaluated for comparison of the cooling performance at blowing ratios of B r =0.5, 1.0, and 1.5. Film flow data were obtained from a row of five cylindrical film cooling holes, inclined in angle of 35° and 0° in direction of streamwise and spanwise, respectively. The film cooling hole spacing between adjacent holes is 15 mm for all the holes. Before the coolant flow being injected through individual cooling hole then encountered with the mainstream, an impingement chamber containing an impingement plate with 43 holes is located on the path of coolant flow. Present study also focused on the effect of impingement spacing, 10mm, 20mm, and 30mm. Compare the results, we find the impingement jet has a significant effect on the adiabatic film cooling effectiveness. As the coolant impingement spacing is fixed, results indicated that higher blowing ratio would enhance the local and the spanwise-averaged adiabatic film cooling effectiveness. Moreover, neither uniform nor parabolic distribution of pressure distribution are observed within the coolant hole-pipe.
Effect Of Hole Shapes, Orientation And Hole Arrangements On Film Cooling Effectiveness
In this present work, the effect of hole shapes, orientation and hole arrangements on film cooling effectiveness has been carried out. For this work a flat plate has been considered for the computational model. Computational analysis of film cooling effectiveness using different hole shapes with no streamwise inclination has been carried out. Initially, the model with an inclination of 30° has been verified with the experimental data. The validation results are well in agreement with the results taken from literature. Five different hole shapes viz. Cylindrical, Elliptic, Triangular, Semi-Cylindrical and Semi-Elliptic have been compared and validated over a wide range of blowing ratios. The blowing ratios ranged from 0.67 to 1.67. Later, orientation of holes have also been varied along with the number of rows and hole arrangements in rows. The performance of film cooling scheme has been given in terms of centerline and laterally averaged adiabatic effectiveness. Semi-elliptic hole utilizes half of the mass flow as in other hole shapes and gives nominal values of effectiveness. The triangular hole geometry shows higher values of effectiveness than other hole geometries. But when compared on the basis of effectiveness and coolant mass consumption, Semi-elliptic hole came out to give best results. ABSTRACT In this present work, the effect of hole shapes, orientation and hole arrangements on film cooling effectiveness has been carried out. For this work a flat plate has been considered for the computational model. Computational analysis of film cooling effectiveness using different hole shapes with no streamwise inclination has been carried out. Initially, the model with an inclination of 30 ° has been verified with the experimental data. The validation results are well in agreement with the results taken from literature. Five different hole shapes viz. Cylindrical, Elliptic, Triangular, Semi-Cylindrical and Semi-Elliptic have been compared and validated over a wide range of blowing ratios. The blowing ratios ranged from 0.67 to 1.67. Later, orientation of holes have also been varied along with the number of rows and hole arrangements in rows. The performance of film cooling scheme has been given in terms of centerline and laterally averaged adiabatic effectiveness. Semi-elliptic hole utilizes half of the mass flow as in other hole shapes and gives nominal values of effectiveness. The triangular hole geometry shows higher values of effectiveness than other hole geometries. But when compared on the basis of effectiveness and coolant mass consumption, Semi-elliptic hole came out to give best results. í µí±í µí±í µí±í µí± ∞ − í µí±í µí±í µí±í µí± í µí±¤í µí±¤í µí±¤í µí±¤ í µí±í µí±í µí±í µí± ∞ − í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± M Mass flux ratio or blowing ratio (defined as ratio of mass flux of coolant to the mainstream) θ Non-dimensional Temperature, í µí±í µí±í µí±í µí± í µí°»í µí°»í µí°»í µí°» − í µí±í µí±í µí±í µí± í µí±¤í µí±¤í µí±¤í µí±¤ í µí±í µí±í µí±í µí± í µí°»í µí°»í µí°»í µí°» − í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± INTRODUCTION The thermal management and protection of the components and surfaces in rocket engine combustion chambers presents one of the most challenging problems for designers. Film cooling is an active cooling strategy, which involves the continuous injection of a thin layer of protective fluid (coolant) near a wall or boundary to insulate it from rapidly flowing hot propellant gases. Its main advantages are that it allows for the use of much lighter-weight nozzle assemblies and it is relatively simple to implement from a fabrication standpoint. M Mass flux ratio or blowing ratio (defined as ratio of mass flux of coolant to the mainstream) ABSTRACT In this present work, the effect of hole shapes, orientation and hole arrangements on film cooling effectiveness has been carried out. For this work a flat plate has been considered for the computational model. Computational analysis of film cooling effectiveness using different hole shapes with no streamwise inclination has been carried out. Initially, the model with an inclination of 30 ° has been verified with the experimental data. The validation results are well in agreement with the results taken from literature. Five different hole shapes viz. Cylindrical, Elliptic, Triangular, Semi-Cylindrical and Semi-Elliptic have been compared and validated over a wide range of blowing ratios. The blowing ratios ranged from 0.67 to 1.67. Later, orientation of holes have also been varied along with the number of rows and hole arrangements in rows. The performance of film cooling scheme has been given in terms of centerline and laterally averaged adiabatic effectiveness. Semi-elliptic hole utilizes half of the mass flow as in other hole shapes and gives nominal values of effectiveness. The triangular hole geometry shows higher values of effectiveness than other hole geometries. But when compared on the basis of effectiveness and coolant mass consumption, Semi-elliptic hole came out to give best results. í µí±í µí±í µí±í µí± ∞ − í µí±í µí±í µí±í µí± í µí±¤í µí±¤í µí±¤í µí±¤ í µí±í µí±í µí±í µí± ∞ − í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± M Mass flux ratio or blowing ratio (defined as ratio of mass flux of coolant to the mainstream) θ Non-dimensional Temperature, í µí±í µí±í µí±í µí± í µí°»í µí°»í µí°»í µí°» − í µí±í µí±í µí±í µí± í µí±¤í µí±¤í µí±¤í µí±¤ í µí±í µí±í µí±í µí± í µí°»í µí°»í µí°»í µí°» − í µí±í µí±í µí±í µí± í µí±í µí±í µí±í µí± INTRODUCTION The thermal management and protection of the components and surfaces in rocket engine combustion chambers presents one of the most challenging problems for designers. Film cooling is an active cooling strategy, which involves the continuous injection of a thin layer of protective fluid (coolant) near a wall or boundary to insulate it from rapidly flowing hot propellant gases. Its main advantages are that it allows for the use of much lighter-weight nozzle assemblies and it is relatively simple to implement from a fabrication standpoint.
Development of a novel film cooling hole geometry
2001
This thesis presents the design, development and testing of a new film cooling hole geometry, the converging slot-hole or console. Both the thermal and aerodynamic performance were measured, using the adiabatic effectiveness and heat transfer coefficient, and aerodynamic loss respectively, to quantify performance. Comparative measurements were made, by testing conventional film cooling hole shapes in parallel with the console experiments. The CFD code, Fluent, was used to predict the performance of the initial design concept before it was manufactured. Initial performance measurements in incompressible flow were performed in a low speed wind tunnel at an engine representative Reynolds number based on mainstream flow and hole diameter. For these experiments, the coolant to mainstream density ratio was approximately unity, and the cooling performance was measured over a flat plate. The console was tested in parallel with cylindrical holes, a slot and fan-shaped holes, all of which had...
Numerical Simulation of Film Cooling Over Flat Plate
New Approaches in Engineering Research Vol. 12, 2021
The effect of film cooling over flat plate is investigated using the commercial CD code; Fluent 6.3. The computational domain includes the coolant supply tube as well as the main mixing region. A tube L/D of 4 and injection angles of (30 o , 60 o , and 90 o) were employed for blowing ratio of (0.33, 0.5, and 1.67), and a density ratio of 1.14. Adiabatic film cooling effectiveness distributions were also determined for inline and staggered arrangements. The main observation from this study that the 30 o hole gave larger effectiveness values than 60 o and 90 o at the blowing ratio of 0.33 with the same length-to-diameter ratio. The maximum effectiveness was achieved with a blowing ratio of 0.5. The results show that the increase of blowing ratio negatively affects film cooling, such that for the blowing ratio of 1.67 the injected coolant tends to lift off from the wall due to the increase of the wall normal momentum. The comparisons for numerical results with experimental data are presented.
EFFECT OF COOLANT JET HOLES ARRANGEMENT ON FILM COOLING PERFORMANCE
The film cooling effectiveness and local heat transfer coefficient for coolant jet holes, arrangement, orientation, and inclination angle have been investigated. The tests were carried out using a single test transient IR thermography technique. Evaluation of the cooling performance is obtained by estimated both film cooling effectiveness and heat flux ratios. Two arrangements of coolant jet holes were tested; one is inline holes and the other is staggered holes. Three blowing ratios of (BR= 0.5, 1.0, and 1.5) were used. In order to predict the flow behavior at the holes region, numerical solutions were introduced. It was found that the interaction and diffusion of the coolant air with hot stream present moderate film temperature beyond the downstream row; this flow is mixed with the coming counter vortex pair from downstream row improved the film cooling effectiveness. Experimentally, staggered arrangement gives better coolant performance than that of inline arrangement. The investigation also showed that using the upstream staggered oriented jet over conventional single jet enhanced the average cooling performance by 20.7%, 28.9%, and 37.8% for BR= 0.5, 1.0, and 1.5, respectively.
Film Cooling Effectiveness for Different Hole Shapes and Blowing Ratios
2016
Film cooling can be used as an effective method of cooling the thrust chamber wall of a liquid rocket engine. A coolant fluid, typically the propellant, is then pushed through the shaped holes until it ultimately reaches the thrust chamber wall. The thermal properties, most notably the effective conductivity, of the coolant and geometrical parameters provide an efficient cooling mechanism for the thrust chamber wall. Film cooling effectiveness (η) is used to express the film cooling phenomena quantitatively. Concluding from the literatures, film cooling effectiveness mainly depends on certain factors such as blowing ratio, injection angle, compound angle/orientation, L/D ratio etc. The present study is related to the numerical investigation of different hole shapes for film cooling performance, which is widely used for cooling of high temperature in the thrust chamber walls, nozzle walls and gas turbines. The adiabatic film cooling effectiveness values are determined computationally...
A Review of Hole Geometry and Coolant Density Effect on Film Cooling
Frontiers in Heat and Mass Transfer, 2015
Improved film cooling hole geometries and effect of coolant density on film cooling have been a focus since the 1970s. One of the first studies on modifying hole exit to improve film cooling effectiveness and quantifying coolant density effect was from Prof. Goldstein's group. This paper provides an overview of the development and implementation of hole exit geometries as well as coolant density study over the past few decades and the impact on future studies of advanced hole geometries under realistic engine-like coolant-to-mainstream density ratio conditions. This work is not intended to be a comprehensive review of the literature.
Numerical simulation of film cooling effectiveness on a flat plate
International Journal for Numerical Methods in Fluids, 2008
Numerical simulation has been conducted to study film cooling effectiveness on a flat plate. Three-dimensional geometry was generated and the effects of blowing ratio and geometrical shape were studied. A cylindrical round, simple angle (CYSA) and laterally diffused, simple angle (LDSA) hole with a streamwise angle of 30° and spanwise angle of 0° were used. Hole length to diameter ratio (L/D=4) is constant for all geometries. Also the diameter of film cooling hole for different cooling holes at the entrance surface (D=10 mm) is constant. The blowing ratio ranges from 0.5 to 1.67, and the mainstream Reynolds number based on the mainstream velocity and hole diameter (ReD) was 8563. Both local and lateral averaged values are presented. Results have a good correspondence with experimental data obtained by Yuen and Martinez-Botas (Int. J. Heat Mass Transfer 2003; 46:221–235). The simulation results show that cooling hole shape affects film cooling effectiveness significantly. The LDSA hole decreases the momentum of jet flow at the exit area of the hole and avoids lift-off phenomenon. Counter-rotating vortex formed downstream of the hole is weaker for the LDSA hole and secondary flow is not powerful enough to disturb the jet flow structure next to the wall. Also the results show that the LDSA hole has a better lateral coverage due to the diffused shape of the hole and has a higher effectiveness value in a wider region on the wall. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of Multi-hole Configuration on Film Cooling Effectiveness
2019
A numerical study is performed to investigate the effects of shaped multi-hole on film cooling effectiveness over a flat plate. Hence a single cylindrical film cooling hole with 11.1 mm diameter is replaced with the shaped multi-hole (14 holes with 2.97 mm diameter) while maintaining constant blowing ratio. Numerical simulations are performed at a fixed density ratio of 1.6, length-to-diameter of 4 and an inclined angle of 35o. Two configurations of hook and fan shapes are considered for multi-hole. The control-volume method with a semi-implicit method for pressure linked equations-consistent algorithm has been used to solve the steady-state Reynolds-averaged Navier–Stokes equations. The k-ε model is applied for modeling the turbulent flow and heat transfer field. It is found that replacing a single hole with the shaped multi-hole leads to a considerable increase in the film cooling effectiveness in both axial and lateral directions. Results of the present study show that for blowing ratio of 0.6, the hook shape and fan shape configurations of multi-hole, provide a higher area-averaged film cooling effectiveness by 48% and 58.2% more than the single hole respectively.