Jet Hole Research Articles

Experimental investigation of heat transfer augmentation of impinging jet solar air heater with stepped transverse ribs

The current experimental investigation analyses the thermal and frictional attributes of an impinging jet solar air heater (IJSAH) with stepped transverse ribs, having varying pitch and size, affixed to the absorber plate. Two ribs of dimension 2 × 4 (R1) and 4 × 6 cm (R2) were tested. The pitch (p) between ribs was 2, 4, and 8 cm, with Reynolds number (Re) varying from 4913 to 13103. The jet hole diameter (Dj) considered were 3, 6 and 9 mm. The maximum Nusselt number (Nu) with the recommended R1 rib having p = 4 cm and Dj = 3 and 6 mm equalled 128.784 and 104.5004 at Re = 13103, respectively, which was 31.22 and 21.76 % higher than that generated by smooth IJSAH. The friction factor (f) generated by the ribbed IJSAH having Dj = 6 mm and p = 4 cm was 57.08 % lower than ribbed IJSAH with Dj = 3 mm. The peak thermohydraulic performance parameter (THPP) achieved was for R1 rib with p = 4 cm and Dj = 6 mm and equalled 1.75, which was 19.49 % higher than smooth IJSAH. The R1 rib with p = 4 cm at Re = 11465 demonstrated better thermal characteristics based on detailed investigation.

Optimal Selection of Active Jet Parameters for a Ducted Tail Wing Aimed at Improving Aerodynamic Performance

The foldable tail of the box-type launch vehicle poses a risk of mechanical jamming during the launch process, which is not conducive to the smooth completion of the flight mission. The integrated nonfolding ducted tail proposed in this article can solve the problem of storing the tail in the launch box. Moreover, traditional mechanical control surfaces have been eliminated, and active jet control has been adopted to control the pitch direction of the flight attitude, which can improve the structural reliability of the tail wing. By studying the effects of parameters such as momentum coefficient, jet hole position, jet hole height, and jet angle on improving the aerodynamic performance of ducted tail wing, relatively good jet parameters are selected. Research has found that compared with jet hole height and jet angle, momentum coefficient and jet hole position are more effective in improving the aerodynamic performance of ducted tail wings. Under a trailing edge jet, a relatively good jet condition occurs when the jet hole height is equal to0.25% of the aerodynamic chord length, and the jet angle is equal to 0°. At this time, with the increase of the jet momentum coefficient, the effect of increasing the lift of the ducted tail wing is the best. Finally, a comparative analysis is conducted on the lift and drag characteristics between the ducted tail wing and traditional tail wing, and it is found that the ducted tail wing can generate lift at a 0° attack angle and will not stall in the high attack angle range of 12°~22°, with broad application prospects.

Effect of crossflow orientations in the impinging jet flow channel on flow and heat transfer enhancement under rotations

An experimental and numerical investigation was conducted to elucidate the flow and heat transfer characteristics of a row of impinging jets within a confined, rotating channel. The study focused on a jet Reynolds number (Rej) of 9,000, examining three distinct crossflow orientations: radially outward (ROCF), radially inward (RICF), and a combined radially outward and inward (ROICF) scheme. Jet-to-impingement surface distances (h/dj) of 2, 4, and 6 (where dj represents the jet orifice diameter) were considered, along with channel rotation speeds corresponding to Rotation numbers (Ro) from 0 to 0.0046. Heat transfer on the leading and trailing sides of the impinging jets was measured using a steady thermochromic liquid crystal (TLC) technique under constant heat flux conditions. Additionally, RANS simulations were employed to investigate the flow fields associated with the impinging jets. The results reveal that in both the ROCF and RICF schemes, heat transfer, characterized by the Nusselt number, decreases from upstream to downstream for each impinging jet. Increasing the rotation number (Ro) leads to enhanced heat transfer, with the trailing side exhibiting marginally higher values than the leading side. In the ROICF scheme, at h/dj = 2, a more uniform Nusselt number distribution is observed across all jet holes compared to the ROCF and RICF schemes, and this uniformity increases with higher Ro. However, for h/dj = 4 or 6, the heat transfer becomes non-uniform and can even deteriorate below the stationary case at high Ro numbers, attributed to the combined effects of Coriolis and centrifugal forces.

Impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate

This study combines the experimental and numerical simulation methods to deeply analyze the impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate. Experiments were conducted to examine the influence of momentum flux ratio and theoretical momentum flux ratio on the discharge coefficient under various crossflow Reynolds numbers. It was found that the variation of the discharge coefficient with the theoretical momentum flux ratio clearly reflects the impact of the crossflow boundary layer velocity profile on the discharge coefficient. The rapid growth of velocity in the boundary layer near the wall in the direction normal to the wall surface, or the decrease in the thickness of the boundary layer, both enhance the shearing effect of the crossflow, leading to a decrease in the discharge coefficient. Analysis of the cavity morphology at the hole exit captured by high-speed camera revealed that the averaged profile of the gas–liquid boundary on the symmetrical plane of the jet below the hole can be approximated as a straight line within the scale of the hole diameter, and the sine of the angle between this line and the upper wall surface is roughly equivalent to the normalized discharge coefficient. This relationship was physically interpreted through the analysis of effective and equivalent flow cross-sectional shapes derived from numerical simulation at different crossflow Reynolds numbers and theoretical momentum flux ratios. Additionally, this paper introduces an innovative method for predicting jet flow rate based on image processing technology. A notable feature of this method is that it does not require the measurement of the pressure inside the gas chamber.

Research on the jet active control mechanism of gas-liquid separation in helical-axial multiphase pumps

In the field of deep-water oil and gas extraction, the intermittent gas blocking phenomenon in helical-axial multiphase pumps leads to decreased pump performance and reliability, severely limiting their large-scale application and promotion in engineering projects. To address this challenge, this study is based on the principle of jet flow field control to flow separation, utilizing external energy for active intervention to suppress the separation phenomena and improve the hydraulic efficiency within the impeller flow channel. The research reveals that the jets achieved a reconstruction of the internal flow in the helical-axial gas-liquid mixed transport pumps. Using orthogonal experimental methods, a preliminary predictive analysis of the factors influencing the effectiveness of the jet system was conducted. The study explored the impact of jet parameters on enhancing the performance of helical-axial gas-liquid mixed transport pumps from the perspective of diminishing gas aggregation at the trailing edge of the rotor cascade and curtailing backflow conditions, and established a mathematical model for the head and efficiency of helical-axial multiphase pumps under jet active control. Research indicates that the jet velocity significantly impacts the efficiency enhancement of multiphase pumps, with an optimal jet speed coefficient, Cjet = 10, identified. Beyond this speed, the benefits brought by increased jet velocity do not compensate for the costs of introducing high-speed jets, and instead, may lead to a reduction in the efficiency of the pump. Jet flow field control methods alleviate the suction side gas aggregation downstream of the jet holes and in the flow domain traversed by the jets, effectively reducing the aggregation of gas phases in the rear channel of the rotor and suppressing backflow near the trailing edge of the rotor cascade. Jet control measures strengthen the working capacity of the blade in the flow direction beyond 0.35 times the length of the streamline, expanding the working range of the blade and enhancing the work efficiency of the multiphase mixed transport pump. Higher jet velocities result in more significant enhancements of blade working power, especially under conditions of high initial gas content, where the relative increase in blade load is more pronounced.

Influence of corrugated jet plates on internal heat transfer and flow dynamics of double-wall cooling: experimental-numerical approach

In the present study, combined experimental and numerical investigations were carried out to analyze the fluid flow dynamics and heat transfer of impinging jets in a corrugated double-wall structure for exhaust nozzle cooling operating at high temperatures. The sinusoidal wavy plate, with multi-jet holes positioned at its trough, served as the jet plate, creating a staggered configuration with respect to the effusion holes. The transient thermochromic liquid crystal (TLC) method was employed to determine the local distribution of the Nusslet number on the flat effusion plate in a wind tunnel at small Reynolds numbers (ranging from 450 to 2700 based on the jet hole diameter (d)). In the numerical part of the study, the k-ω SST turbulence model verified with the TLC data was used to solve the RANS equations. The effects of jet-to-plate spacing (Have/d = 1.6–3.6), corrugated plate amplitude (A/d = 0.2–0.8), effusion hole diameter (de/d = 0.6–1.5), and Reynolds numbers were examined in detail. Our results showed that the introduction of the corrugated structure in the jet plate altered the high-velocity region pattern within the jet hole, leading to a 16 %-81 % reduction in jet core length compared to the flat jet plate. At a relatively high wave amplitude (A/d ≥ 0.5), the vortex structure underwent significant changes, inducing a higher level of turbulence kinetic energy in the near-wall region of the target chamber. This led to enhanced heat transfer near the stagnation and effusion hole regions compared to the flat double-wall cooling. The effusion hole diameter exerted a minimal effect on the overall Nusselt number of the corrugated double-wall cooling. At very low Reynolds numbers (Rej 〈900), the flow and heat transfer characteristics in corrugated double-wall cooling resembled those observed in flat double-wall cooling.

Jet array impingement heat transfer in a rectangular cavity with effusion holes

Various researchers have studied jet array impingement heat transfer in impingement/effusion cooling systems. However, there is a lack of research on impingement/effusion cooling systems installed within rectangular cavities that focus on the impact of the proximity of the jet hole to the cavity sidewalls on cooling performance. The main objective of this study is to investigate the flow and heat transfer characteristics of jet array impingement with effusion holes in a rectangular cavity, considering various spacings between the cavity sidewalls and the outermost jet hole. The design parameters in this study include the ratio of the jet hole pitch to jet hole diameter of 7.1, 10.0, and 16.7, and the ratio of the distance between the jet and impingement plates to jet hole diameter of 2, 6, and 10, with the Reynolds number based on the jet hole diameter ranging from 2500 to 15,000. Heat transfer characteristics in the stagnation region and wall jet region were examined using local Nusselt number distributions on the impingement surface, measured by liquid crystal thermography. The local Nusselt number was high in the stagnation region and decreased radially from the stagnation region as the wall jet region formed. The closer the outermost jet hole is to the sidewall, the higher the Nusselt number on the impingement surface near the sidewall. Moreover, the flow structure in the rectangular cavity was numerically investigated, and the velocity vectors and streamlines showed that primary and secondary vortices were generated in the middle of two neighboring jets and near the sidewall, respectively. This study also assessed previous average Nusselt number correlations. Based on experimentally determined average Nusselt number data with 54 center unit cells and 1296 side unit cells, new correlations to predict the average Nusselt number on the impingement surface in a rectangular cavity with effusion holes were developed.

Study on the Influence of Volute Throat Jet on Excitation Vibration Alleviation of Radial Turbine Blade

Abstract Turbine blade fracture, resulting from high-cycle fatigue (HCF), is the most commonly observed failure mode of turbochargers. In a vaneless turbine, the radial turbine blade is susceptible to HCF under excessive aerodynamic excitation due to the flow field distortion caused by the volute tongue. The present study explores a technique to mitigate blade excitation by reducing pressure disturbance in the volute tongue area. The gas with higher pressure in the inlet section of the volute is transferred to the low-static pressure area upstream of the volute tongue through a throat jet hole. The usage of high-pressure gas improved the homogeneity of the flow field near the volute tongue. The study investigates the mitigation of high-pressure gas jet on turbine blade excitation, the impact of jet hole geometry on the suppression effect of the blade vibration, and the effect of high-pressure jet on turbine performance using numerical simulation of unsteady flow fields. The results indicate that the jet flow has a substantial impact on dampening the blade vibrations. The harmonic pressure amplitude at the monitor point located within the high blade vibration amplitude region is reduced by up to 56%. Generalized pressure analysis reveals that the aerodynamic excitation of the turbine blades is significantly reduced. Experimental evidence verifies the effectiveness of the jet hole scheme in reducing blade vibration. Moreover, the jet hole has a negligible effect on turbine efficiency. However, there is a degree of increased stress in the volute tongue with a jet hole which needs to be evaluated in engineering applications.

Experimental and numerical study on the effect mechanism of geometric parameters on jet impingement cooling in a limited space

In order to meet the development needs of the internal cooling structure of gas turbine blades, this paper researches the jet impingement cooling in a limited space. Numerical simulation method is employed to obtain the flow field details and analyze the flow and heat transfer mechanism. The heat transfer coefficient distribution of the target surface is obtained by the transient liquid crystal, which verifies the accuracy of the CFD results. The effects of inlet mass flow rate m˙in, rows of jet holes N, jet hole diameter Dj, jet-to-target distance H/Dj and transverse distance between jet holes S/W are considered. The results show that: The flow and heat transfer characteristics at different m˙in are qualitatively similar. N has a significant effect on the heat transfer coefficient and total pressure difference. With the increase of N, the heat transfer coefficient and the total pressure difference decrease. Dj has obvious effect on heat transfer coefficient and total pressure difference. As Dj increases, both the heat transfer coefficient and the total pressure difference decrease. H/Dj has only a slight effect on the heat transfer coefficient and total pressure difference. When H/Dj increases from 1.2 to 2.2, the heat transfer coefficient increases and the total pressure difference decreases. When H/Dj increases from 2.2 to 3.2, the heat transfer coefficient decreases and the total pressure difference is almost unchanged. The effect of S/W on the heat transfer coefficient and total pressure difference is more obvious than that of H/Dj. The heat transfer coefficient and total pressure difference are the largest when S/W = 0.5. The structure with N = 8，Dj = 24 mm，H/Dj = 2.2，S/W = 0.5 has the best comprehensive heat transfer performance under the range of the boundary condition.

Numerical research on the flow and heat transfer characteristics in the immersion jet cooling for servers

Immersion cooling and jet impingement liquid cooling, as two of the significant emerging direct contact liquid cooling methods, have promising prospects for development and application. The two cooling methods are combined and numerical simulation is applied to study the heat transfer performance of the immersion jet-cooled server. The orthogonal method is employed to determine the optimal structural parameters of the immersion jet, and the flow and heat transfer characteristics under different inlet and outlet layouts are investigated. The study shows that the optimal heat dissipation effect and moderate pressure are achieved when the ratio of jet distance (L) to jet pipe diameter (D) is 1.2, and the ratio of jet hole spacing to jet orifice diameter is 11.1. When the inlet and outlet of the cabinet are arranged in a Z-shaped layout, the pressure on the server surface is reduced by 17.1 %–31.6 % compared to a U-shaped layout. When the inlet and outlet of the cabinet are arranged in a Z-shaped manner with the inlet at the bottom and the outlet at the top, the highest heat transfer coefficient is over 24000 W/(m2· K), which is approximately 1.5 times higher than that of other layouts. Through dimensional analysis, a quadratic function was selected to fit the relationship between heat transfer coefficient h, server pressure P and jet ratio (D/L), opening area A; In addition, the criterion relationship of Nu = f (Re, Eu) is fitted according to the simulation data, which provides a theoretical basis for energy saving and consumption reduction in data centers.

A novel compact supercritical CO2 solar receiver based on impinging jet: Heat transfer performance and thermal stress analysis

The compact solar receiver can withstand high temperature and high pressure, which provides promising solutions for direct supercritical CO2 (S-CO2) solar receiver applications. However, it still suffers from local high temperature and large thermal stress due to the non-uniform heating boundary condition. The impinging jet method can significantly enhance the local heat transfer coefficient, holding significant potential in reducing the local high temperature of the compact S-CO2 receiver. Inspired by this, a novel design for a compact S-CO2 receiver using the impinging jet was proposed in this work. The heat transfer performance and stress behavior of the jet channel within the receiver were numerically investigated. The results showed that the jet channel has a significantly higher heat transfer performance than the rectangular channel, and the shorter flow path of the jet channel also effectively reduces the pressure loss. Meanwhile, the jet pattern significantly enhances the temperature uniformity, thereby reducing the thermal stress. In addition, increasing the channel aspect ratio improves the thermo-hydraulic performance, but increase the stress at the same time. The increase in the number of jet holes and the jet hole diameters not only enhance the thermo-hydraulic performance, but also reduce the stress of the jet channel.

Transient experimental study on cooling performance of a radial turbine with impingement cooling in rotating state

Increasing the inflow temperature of a turbine is an effective approach for enhancing the thermal efficiency of devices operating in the Brayton cycle, such as micro-gas-turbines and waste heat recovery systems. However, elevated temperatures also pose a significant risk of thermal fatigue failure. This paper presents an experimental investigation of impingement cooling for radial turbines, aiming to achieve high cooling performance with a simple structure. High-frequency infrared thermal imaging technology was employed to measure temperature distribution in the turbine rotor under various operational conditions. The results indicate that jet-impingement cooling can substantially reduce the solid temperature of the radial turbine, with a maximum temperature reduction of approximately 44 K achieved by consuming the coolant with ṁre= 5%. Increasing the mass flow rate of the coolant consistently lowers the rotor temperature; however, an increase in rotational speed results in higher thermal inertia, thereby diminishing the cooling enhancement effect. The temperature distribution on the turbine surface exhibits significant periodic characteristics over time, leading to temperature fluctuations of 5 K to 30 K at the hub position. Furthermore, the cooling performance is further enhanced near the jet hole on the back-disc side of the inducer region, while the tip side closer to the exducer obtains better cooling effects.

Multi-jet impingement cooling in the leading edge of turbine blade using matrix as internal structure

Multi-jet impingement is a competitive cooling scheme for the turbine blade leading edge, due to its strong ability in suppressing thermal boundary layer and quickly releasing the thermal load. However, crossflow is always a challenge if thermal performance is expected to be further improved. This paper proposed to induce jet flow from matrix to enhance cooling capability as well as uniformity of leading edge. A dual-air-paths test rig is built to measure heat transfer distribution and to validate the computational method. The results indicated strong coupling between jet cavity and matrix, implying the potential of enhancing heat transfer on both ends. Comparisons are made between different jet hole locations, among which the “Stagnation” position yields best performance, since superior initial jet condition can be created by matrix sub-channel flow. Increasing jet hole aperture leads to elevated heat transfer of nearly 72% in jet cavity, due to more stable vortex scour on the target wall. Changing jet cavity outflow configuration has significant effect on heat transfer due to thorough reconstruction of thermal field. The most advanced performance is acquired by both-sides outflow configuration, with approximately 34% improvement in heat transfer compared to the single-side cases.

CFD for the optimization of spiral wound film assembly

In this paper, a conventional mesh shim for a spiral wound membrane assembly is structurally optimized by adding jet holes to achieve the jet function, and the effect of curvature on fluid flow is investigated. The three different gaskets are compared with each other and the performance of the optimized gaskets is investigated by using computational fluid dynamics (CFD) techniques and analyzed parametrically. This knowledge can be supplemented by the use of CFD techniques for spacers, whereby the geometry of the spacer can be optimized and the corresponding performance of the spiral wound film assembly can be improved.

Heat and Flow Characteristics of Aerofoil-Shaped Fins on a Curved Target Surface in a Confined Channel for an Impinging Jet Array

The main purpose of this investigation was to explore the heat transfer and flow characteristics of aero-foil-shaped fins combined with extended jet holes, specifically focusing on their feasibility in cooling turbine blades. In this study, a comprehensive investigation was carried out by applying impinging jet array cooling (IJAC) on a semi-circular curved surface, which was roughened using aerofoil-shaped fins. Numerical computations were conducted under three different Reynolds numbers (Re) ranging from 5000 to 25,000, while nozzle-to-target surface spacings (S/d) ranged from 0.5 to 8.0. Furthermore, an assessment was made of the impact of different fin arrangements, single-row (L1), double-row (L2), and triple-row (L3), on convective heat transfer. Detailed examinations were performed on area-averaged and local Nusselt (Nu) numbers, flow properties, and the thermal performance criterion (TPC) on finned and smooth target surfaces. The study’s results revealed that the use of aerofoil-shaped fins and the reduction in S/d, along with surface roughening, led to significant increases in the local and area-averaged Nu numbers compared to the conventional IJAC scheme. The most notable heat transfer enhancement was observed at S/d = 0.5 utilizing extended jets and the surface design incorporating aerofoil-shaped fins. Under these specific conditions, the maximum heat transfer enhancement reached 52.81%. Moreover, the investigation also demonstrated that the highest TPC on the finned surface was achieved when S/d = 2.0 for L2 at Re = 25,000, resulting in a TPC value of 1.12. Furthermore, reducing S/d and mounting aerofoil-shaped fins on the surface yielded a more uniform heat transfer distribution on the relevant surface than IJAC with a smooth surface, ensuring a relatively more uniform heat transfer distribution to minimize the risk of localized overheating.

Numerical Investigation of a Novel Heat Exchanger in a High-Temperature Thermoelectric Generator

A cylindrical thermoelectric power generator for high-temperature flue gas was designed, and a distributor was installed to enhance heat transfer by affecting the jet on the hot side. The influence of the different distributor diameters and jet hole diameters on the temperature distribution of the hot and cold sides of the thermoelectric module was studied. The corresponding temperature field, velocity field, and exhaust pressure drop of the device were also obtained. The results indicated that the temperature difference between the hot and cold ends of the thermoelectric module was increased, and the uniformity of the temperature distribution was improved with the increasing diameter of the distributor and the decreasing diameter of the jet hole. The performance of the thermoelectric power generator was further improved by the jet hole with a gradient diameter. The number and distance between jet holes were sensitive to pressure drop.

Experimental study on the internal temperature rise of a high-speed canned motor pump for liquid rocket engines

High-speed electric pumps are now gradually applied in liquid rocket engines. Compared with the pumps with dynamic seals, the canned motor pumps are more reliable, and thus suitable for delivering risky propellants. However, the partial flow diverted to the air-gap for cooling and lubrication faces the risk of overheating caused by its friction against the rotor. This paper performed an experiment on this issue with a high-speed canned motor pump for a notional rocket engine. Impellers with and without balance holes, as well as different configurations of jet holes, were adopted and their effects were analysed. Results showed that the internal temperature rise decreased by up to 78% when the balance holes were removed, and decreased by up to 40% when the jet hole configuration was modified. Both factors influenced the internal temperature rise by varying the flow rate of the cooling recirculation. The study suggested that the high-speed canned motor pump should be designed with an appropriate flow rate of the cooling recirculation, so as to control the temperature rise of the propellant and ensure safe operation of the rocket engine.

Experimental and parametric study in pool boiling enhancement with self-induced jet impingement on the microporous copper surface using R1336mzz(Z)

Enhancing pool boiling performance is of significant interest for cooling high-power electronics. This paper introduces a self-induced jet impingement device designed for practical boiling enhancement. Using R1336mzz(Z) as the working fluid, we performed an experimental and parametric study on a microporous copper surface, considering the distinct characteristics of this device. Our results demonstrate that, due to the promotion of bubble detachment and the ensuring of sustained liquid absorption, the self-induced jet impingement device augments the Critical Heat Flux (CHF) on the microporous copper surface effectively. Nonetheless, the large predominant size of nucleation sites on this surface highlights the boiling suppression effect from jet impingement, resulting in a minor decrease in the Nucleate Boiling Heat transfer coefficient (hNB). Parametric evaluations reveal that strategies promoting the circulation flow of working fluid have a positive impact on CHF enhancement. Conversely, this device might negatively influence boiling heat transfer on microporous copper surface under conditions of liquid scarcity due to the restricted total flow area of jet holes. Our study indicates CHF and hNB@CHF enhancements of up to 196.0% and 291.0%, culminating in 73.7 W/cm2 and 78.2 kW/(m2∙K), respectively, compared to the boiling performances of standard pool boiling on the non-microporous copper surface.

IMPACT OF MEASUREMENTS TECHNIQUES ON HEAT TRANSFER CHARACTERISTICS IN AIR JET ARRAYS

Air impact processes have diverse applications in engineering, including backflow welding, textile drying, and gas turbine blade and combustion liner cooling. This research examines the influence of experimental methodologies and measurement tools on convective heat transfer in adjustable air jet assemblies. The experiment involves the use of heated targets made of thin stainless steel foil with constant heat flux boundary conditions. Thermography measures target surface temperatures by analyzing how internal passage cross-flow affects convective heat transfer via outflow adjustments. The experiments involve two arrays of jet nozzles: inline and staggering, each comprising 44 impingement jet nozzles arranged in 4 rows with 11 jet holes in each row. The study presents unsteady time average local and spatial Nusselt numbers as functions of jet Reynolds number (4630-14000) and explores their dependence on the jet nozzle diameter. Cross-flow levels significantly affect spatial and local Nusselt numbers in both local and span-wise averaged values, regardless of the Reynolds number. Strong cross-flow (single configuration) distributes flow causing turbulence and uneven heat distribution, reducing Nusselt numbers. In contrast, moderate cross-flow (double configuration) improves heat transfer and increases Nusselt numbers. The study emphasizes the crucial role of experimental techniques in heat transfer evaluation and demonstrates agreement with prior studies within a standard error below 5%.

Comparative study of film cooling performance on curved walls with various hole configurations and blowing ratios

In order to increase turbine efficiency and prevent metal materials from being corroded by high temperatures, one of the great important methods for turbine blade cooling is film cooling. This work explores numerically the effects of various curvature wall on film cooling performance, and the effects of three different hole structures and four various blowing ratios (0.25,0.5,1,1.5) were discussed. Results show that the film cooling effectiveness values of the various configurations (cylindrical hole, shaped-hole, trenched shaped-hole) on the convex wall are 112%, 76%, and 50% higher than that on the concave wall respectively when the blowing ratio is 0.25, which indicates convex wall exhibits a greater potential to release the cooling effects of the jet holes compared with the concave wall and flat wall. Moreover, trenched shaped-holes provide a more uniform protection for wall, especially in terms of the coverage area in the spanwise direction. At the ends of the xs/D = 5 line, the cooling performance of trenched shaped-holes are locally 1320% and 1610% higher than cylindrical holes and shaped-holes, respectively. Additionally, when the blowing ratio is high, compared to curved walls, trenched shaped-holes have the most significant effect on improving the film cooling of flat wall surfaces.