Pressure Sensitive Paint Technique Research Articles

An investigation on film cooling and aerodynamic performance of squealer blade tip with inclined cavity bottom

The gas turbine blade tip poses as one of the most challenging areas for blade cooling, primarily due to its intricate three-dimensional flow characteristics, which make it one of the primary contributors to aerodynamic loss within the turbine stage. In this paper, the adiabatic film cooling effectiveness (η) distributions at five squealer tip structures (Original, PS7.5, PS15, SS7.5, SS15) with varying inclined angles of cavity bottom surface were obtained using pressure sensitive paint technique (PSP) under five coolant blowing ratios (BR = 0.4, 0.8, 1.2, 1.6, 2.0). Combined with the numerical simulations verified by the experimental data, the tip flow field details were described to reveal the cooling characteristics of the tip region. The results indicate that, at low BRs, the film hole downstream exhibits apparent cooling traces, which are most pronounced at the SS15 tip. With the increase of BR, the cooling traces gradually fade, and the area-averaged film cooling effectiveness (ηΑ-avg) rises. At low BRs (BR = 0.4, 0.8), the ηΑ-avg of the SS15 tip is 12.8 %, and 8.4 % higher than that of the Original tip, respectively. At BR = 1.6, the ηΑ-avg of the PS15 tip is the highest, 3.9 % higher than that of the Original tip. The ηΑ-avg of SS7.5 is the lowest at all BRs. In addition, the pitch-averaged η (ηavg) of PS7.5 at some BRs is higher in the front part of the tip, compared to the Original tip. At BR = 1.2, the area-averaged total pressure loss coefficient (Cpt¯)of the PS7.5 and PS15 is 1.46 % and 1.58 % higher than that of the Original tip, respectively. However, the Cpt¯ of the SS7.5 and SS15 is 1.77 % and 10.28 % lower than that of the Original tip, respectively.

Experimental and Numerical Evaluation of the Film Cooling Characteristics of the Multi-cavity Tip with Inclined Film Holes

Abstract Due to the complex flow field and the considerable heat load on the turbine blade tip, film cooling is essential to protect the tip from being overheated. In this paper, an experimental work was conducted to compare the film cooling distributions of four tip structures (cavity numbers are one, two, three, and four) with two film hole configurations (perpendicular and 45 degrees inclined to the cavity floor) under three coolant blowing ratios. By using pressure sensitive paint technique, the distributions of film cooling effectiveness were measured. Moreover, a computation with careful validation was executed to obtain the cooling traces in the tip region and compare the aerodynamic performance of these multi-cavity tips. The results showed that the value and uniformity of film cooling effectiveness were improved by the inclined configuration. The tip film cooling was enhanced when using the multi-cavity tips. The aerodynamic loss of the tested tips was compared as well.

Evaluation of Wavy-Trailing-Edge Film Cooling Versus Pressure Side Cutback Cooling

This study measures the film cooling effectiveness along the trailing edge (TE) of a turbine blade in a linear cascade. The film cooling effectiveness is measured and analyzed using the pressure-sensitive paint (PSP) technique. Two different TE designs are investigated: the standard pressure side cutback and the new alternating discharge design (referred to as a wavy-TE design). The alternating discharge design is a new design with a wavy structure between the pressure and suction surfaces at the TE. The new wavy structure allows the coolant to discharge from the TE so that it alternates between the pressure and suction surfaces. Testing is carried out in a five-blade, linear, steady-state cascade with inlet and exit Mach numbers of 0.20 and 0.30, respectively. The freestream turbulence intensity is measured to be 10.5% upstream of the blade leading edge. Coolant-to-mainstream mass flow ratios (MFRs) vary from 0.30 to 1.25% and coolant-to-mainstream density ratios (DRs) of 1.0, 1.5, and 2.0 are examined. A positive MFR and DR effect is witnessed. The results demonstrate the potential of the alternating discharge as a promising TE design and provide gas turbine designers with an improved TE cooling scheme.

Pressure Sensitive Paint and Large Eddy Simulation Investigation on the Impact of Trench Depth on Flat Plate Film Cooling Through Shaped Holes

Abstract To increase film cooling effectiveness levels downstream of film cooling holes, trenches manufactured in the thermal barrier coating can be adopted. The performance of this solution depends on the trench geometrical characteristics, namely its depth and width. A large eddy simulation (LES)-based numerical study has been performed at Korea University to investigate the effects of trench configuration on thermal protection, resulting in a 22% increase in cooling performance compared to the reference case without a trench. The present paper reports the results of an experimental investigation carried out at Bergamo University on a Plexiglass flat plate model with a set of three fan-shaped holes incorporated into an existing wind tunnel, replicating the numerical setup. Pressure-sensitive paint (PSP) technique was used to measure the adiabatic film cooling effectiveness. Besides the standard shaped hole case, the best and worst trench configurations coming from a DoE approach have been examined at various coolant to mainstream blowing ratios M in the range between 0.5 and 3. Cases at M = 1.5 were used to cross-check the prediction capability of the LES numerical simulation for the selected trenched cases. PSP and LES results are in good agreement, also with the literature data. The high depth/low width trench was shown to give an improved performance for M larger than 1.

Improved Spatiotemporal Distributions of Sweeping Jet Film Cooling With a Shaped Exit Design

Abstract Sweeping jet (SJ) is a self-excited flow control device that can generate continuous and periodic flow, which makes it a promising geometry for film cooling. However, the cooling performance of current SJ configurations is not significantly better than that of 777-shaped holes. This paper presents two modified SJ configurations, named shaped SJ1 and shaped SJ2, which possess distinct shaped exit geometries. The spatiotemporal coolant distributions were comprehensively quantified for the 777-shaped hole, the compact SJ (with compact geometry), the shaped SJ1, and the shaped SJ2. The instantaneous cooling effectiveness distributions of the four configurations at blowing ratios (M) ranging from 0.5 to 3.0 were measured using the fast pressure-sensitive paint technique. The shaped SJ2 integrated the cooling characteristics of the 777-shaped hole and SJ. It maintained stability at a relatively low M, while began to oscillate when M was increased above 1.5. The shaped SJ design exhibited superior cooling effectiveness at both low and high M of 0.5 to 3.0. A proper orthogonal decomposition analysis and simulations illustrated the oscillation processes and flow structures within the SJ configuration. The shaped SJ2 showed a reduced outlet momentum and a more even distribution of film coverage than the 777-shaped hole, resulting in considerably improved cooling performance.

Experimental and Numerical Investigations into the Effects of Rim Seal Structure on Endwall Film Cooling and Flow Field Characteristics

During the practical operation of gas turbines, relatively cooled air from the compressor and the rim seal is applied in order to prevent mainstream ingestion into the space between the rotor and stator disc cavities, which can prolong the service life of hot components. On the one hand, the purge flow from the rim seal will inevitably interact with the mainstream and result in secondary flow on the endwall. On the other hand, it can also provide an additional cooling effect. In this paper, four rim seal structures, including an original single-tooth seal (ORI), a double-tooth seal (DS), a single-tooth seal with an adverse direction of the coolant purge flow and mainstream (AS) and a double-tooth seal with an adverse direction of the coolant purge flow and mainstream (ASDS), are experimentally and numerically investigated with mass flow ratios of 0.5%, 1.0% and 1.5%. The flow orientation of the coolant from the rim seal is considered as one of the main factors. The pressure-sensitive paint technique is used to experimentally measure the film cooling effectiveness on the endwall, and flow field analysis is conducted via numerical simulations. The results show that the cooling effect decreases in the cases of DS and ASDS. AS and ASDS can achieve a better film cooling performance, especially under a higher mass flow ratio. Furthermore, the structural changes in the rim seal have little impact on the aerodynamic performance. AS and ASDS can both achieve a better aerodynamic and film cooling performance.

Dynamic stall characteristics of unswept pitching wing

An experimental investigation of dynamic stall on upswept pitching wing was conducted using Particle Image Velocimetry (PIV) and Pressure Sensitive Paint (PSP) techniques. The wing had an aspect ratio AR = 4 and a NACA 0012 airfoil section profile assembled with a round-tip. The wing motion of interest in this study is pitching at a certain angle of attack range and the wing was robustly designed and machined out of Aluminum to minimize elasticity and tip flapping motions. The freestream Mach number, M∞ = 0.1, and the Reynolds number based on chord length, Rec = 2 × 105, were considered as flow parameters for observing dynamic stall phenomena and for comparison with available numerical simulations from literature. The pitching motion of the wing is sinusoidal with a reduced frequency k = πfc/U∞ = 0.1, and the minimum and maximum angle of attack of the pitching motion were 4° and 22°, respectively. Details of flow structures during pitching at various phase angles were captured using planar two-dimensional (2D) PIV at three spans, x/c = 0.5, 0.75, and 1.0 and the pressure imprint on the surface of the wing was captured by a single shot lifetime method using fast porous pressure-sensitive paint. The initial results show the formation of a separation bubble at a small incident angle and the emergence of a dynamic stall vortex (DSV) after the bursting of the separation bubble. The DSV propagates towards the trailing edge of the wing with its integral scale varying across the three spans of the wing revealing three-dimensionality. The PSP results show a uniform build of suction pressure at low angle of attack which later intensifies in a non-uniform manner due to a circulatory motion of the flow during pitching. After the end of the upstroke phase, the flow starts to reattach to the surface of the wing while the DSV grows and moves away from the surface as it travels downstream along the chord until sheds beyond the trailing edge. The PSP results also capture the tip unloading period during the pitching motion.

Experimental Study on the Improvement of Film Cooling Effectiveness of Various Modified Configurations Based on a Fan-Shaped Film Cooling Hole on an Endwall

Several studies have previously been conducted to improve the cooling performance of film cooling. However, most of the research has conducted experiments with film cooling holes on flat plates, and thus, the results of these studies do not encompass the influence of the complex mainstream behavior within the turbine passage on film cooling. In this study, three different film cooling hole configurations were installed on the endwall of a turbine linear cascade to measure adiabatic film cooling effectiveness and evaluate cooling performance. The film cooling holes compared in the experiment for film cooling effectiveness were a 7-7-7 fan-shaped hole (Baseline), a Baseline with a double-step structure at the hole exit (Staircase), and a Baseline with an additional expanded passage at the hole leading edge (Compound Expansion). A total of nine holes were manufactured on the turbine endwall to assess film cooling performance, as various factors, such as mainstream acceleration, secondary flow within the turbine passage, and so on, can influence film cooling. Adiabatic film cooling effectiveness was measured using the pressure-sensitive paint (PSP) technique. Mass flow ratios ranging from 0.25% to 1.25% of the mass flow rate of a single turbine passage were supplied to the plenum chamber within the test rig. As a result, all experimental results confirmed the impact of secondary flow within the turbine passage on film cooling. In the case of the Staircase, it exhibits an overall cooling trend similar to the Baseline. It shows small cooling performance degradation compared with Baseline due to lift-off, and its double-step structure laterally expanding results in better cooling performance at high mass flow ratio (MFR) conditions. For the Compound Expansion, at low MFR, the momentum of the coolant is lower compared with other configurations, leading to lower cooling performance due to the influence of secondary flow. However, at high MFR, the Compound Expansion provides wider protection compared with other hole geometries and shows high cooling performance.

A comprehensive heat transfer investigation for impingement/effusion cooling under crossflow conditions

Impingement/effusion cooling is regarded as a highly efficient cooling structure and has been widely adopted in various energy-dependent scenarios. It often exhibits crossflow phenomena due to design or concurrent factors. However, quantifying the individual heat transfer contributions of each cooling structure in impingement/effusion cooling under crossflow conditions remains unclear. In this study, the pressure-sensitive paint and temperature-sensitive paint techniques were adopted to separately evaluate the performance of effusion and impingement cooling under crossflow conditions for a comprehensive heat transfer investigation. Different coolant flow rate (normalized as Rejet = 10,000 to 25,000) and crossflow flow rates (normalized as CMR = 0 to 0.3) were examined. In effusion cooling, cooling effectiveness generally decreased with higher Rejet but improved with increased CMR, except for Rejet = 10,000 and 15,000 with CMR ≥ 0.25, where excessive crossflow coolant negatively affected cooling effectiveness. When comparing cooling effectiveness at the same blowing ratio, higher Rejet with crossflow consistently outperformed, with the maximum improvement reaching 11.55 %. In impingement cooling, the Nusselt number (Nu) increased with Rejet due to enhanced impingement momentum. Crossflow had a detrimental effect at Rejet = 10,000 but showed improvements at Rejet = 15,000 to 25,000. With increasing Rejet, heat transfer performance became less sensitive to varying CMR. Compared to cases without crossflow, the Nu increments at CMR = 0.25 were -5.01 %, 4.03 %, 3.53 %, and 2.64 % for Rejet = 10,000 to 25,000, respectively. It was revealed that crossflow was influential on the impingement cooling, meanwhile, highly influential on the effusion cooling. This study intended to provide a more comprehensive understanding of impingement/effusion cooling and assistance in designing more efficient and tailored cooling strategies for high-performance energy systems.

Study on Additive Effect of Film Cooling Effectiveness in Two Rows of Fan-Shaped Holes

Abstract The coolant jet interaction has a great influence on the superposition prediction of multirow film cooling. Although there have been many efforts to reveal the mechanics of additive effect in multirow film cooling, the available knowledge about developing the superposition method is still limited. The present work examines the film cooling effectiveness in two rows of fan-shaped holes by pressure sensitive paint technique, at the blowing ratios of 0.5–2.0 and the density ratio of 1.0. It is found that the impact of upstream flow on the downstream cooling film is reflected in the variation of turbulence intensity. The enhanced turbulence intensity is detrimental to the downstream film cooling effectiveness especially at the far away region. The mixing of upstream flow and coolant ejection starts at the leading edge of the hole exit. Thus, the streamwise width of the hole exit should be taken into consideration for better predicting the film cooling effectiveness around the holes. The cause of additive effect is that the coolant ejection at the second row affects the local mainstream entrainment. Then, a new correction factor, which characterizes the influence of coolant ejection on the mainstream entrainment of the upper row, is proposed for improving the classical Sellers method. The final result shows a good agreement with experimental data.

A comparative study of purge slot exit shape on the film cooling effectiveness of a gas turbine shroud

To achieve higher efficiency and performance, a modern gas turbine withstands the extremely high thermal environment. In the turbine endwall passage, a high and non-uniform heat transfer appears due to various secondary flow. The purge flow injected through the upstream slot between the stationary and rotating pars can thermally protect the endwall surface by forming air film layer on it. However, since an excessive amount of purge flow reduce the system efficiency, it is needed to effectively inject the purge flow with a limited amount. Accordingly, in the present study, the effect of purge slot exit shape on the film cooling effectiveness (hereby FCE) of a shroud surface was discussed. As nondimensional design parameters of the purge slot, L/Ws, RW/Ws, and RL/Ws were defined, representing the geometric features: the slot width (Ws), the fillet radius at the windward side (RW) and fillet radius at the leeward side (RL) of slot exit, respectively. The measurement of the FCE was performed in a five-blade linear cascade rig using the PSP (Pressure sensitive paint) technique. The results showed that the FCE increased for wider slot width at a given blowing ratio condition. In addition, the fillet radius at the windward side (RW) has a negative effect on the FCE regardless of blowing ratio condition since the purge flow was easily disturbed by the accelerated mainstream injection. On the other hand, the Case 7 with the RW/Ws = 0.9 showed 5.1 % of the improvement of FCE at a higher blowing ratio M = 0.25 compared with the Case 2 with RW/Ws = 0, which represents the sharp edge at the windward side of the slot exit.

Experimental investigation of full-coverage film cooling characteristic of single/double-wall cooling vane

This paper employed the pressure sensitive paint (PSP) technique to measure the adiabatic film cooling effectiveness distributions of both the single-wall cooling vane (SCV) and the double-wall cooling vane (DCV). The experiments were implemented in an annual cascade under a Reynolds number of 3.0 × 105 condition. Furthermore, the effects of mass flow ratio (MFRs include 4.99 %, 6.65 %, 8.32 %, 9.98 %, and 11.65 %) and density ratio (DRs include 1.0, 1.5, and 2.0) on the adiabatic effectiveness distribution were also investigated. The results reveal that the DCV improves dramatically the film cooling effectiveness of the pressure side and the suction side compared with the SCV, and the effectiveness is elevated by 12 % and 25 %, respectively. As the MFR increases, the lateral average film cooling effectiveness of the SCV initially increases and then decreases, while that of the DCV enhances monotonously. Additionally, when the DR is raised from 1.0 to 1.5, the lateral average film cooling effectiveness of the pressure side of the SCV is increased by 50 % at the MFR = 6.65 %. Also, the DCV presents both high and even film cooling effectiveness contour distribution at high density ratio conditions, and the surface average film cooling effectiveness of the DCV is greater than 0.4 when the MFR ≥ 8.32 %.

Experimental and numerical investigation on the metering and diffuser length effects of a laidback fan-shaped film cooling hole

In this study, the metering and diffuser length effects of a laidback fan-shaped (LBF) hole on the film cooling effectiveness (FCE) were investigated. The FCE was measured using the pressure sensitive paint (PSP) technique, with a density ratio (DR) of 2.0 and five blowing ratios (BR). The experimental results indicated that the FCE increased as the diffuser length increased. However, when the metering length ratio increased beyond the critical length, the coolant was shifted to a specific side of the diffusion section, resulting in a lower FCE. A computational analysis was performed to investigate the coolant shift at longer metering lengths. Numerical results indicate that the center velocity of the cylinder section is higher for the longer metering length cases, which leads to a large separation bubble in the diffusion section, these resulted in the increase of the flow unsteadiness and instability at the hole exit.

Effects of structural parameters of laidback fan-shaped hole on film cooling effectiveness on convex surface

To burden higher turbine inlet temperature, shaped holes are introduced to the film cooling of turbine blade. The structural parameters of shaped holes are the key variables for the cooling design. Relevant literatures conduct studies mainly on the flat surface, which excludes the influence of blade curvature. And their conclusions are inconsistent, appealing for further mechanism study. In this paper, the effects of structural parameters of laidback fan-shaped hole are experimentally investigated on a convex surface. Pressure sensitive paint technique is used to measure the adiabatic effectiveness. Three parameters, including forward expansion angle (0–12 deg), lateral expansion angle (2–20 deg) and length of the diffuser (2–14 mm), at five blowing ratios (0.5, 0.8, 1.0, 1.3 and 1.5) are tested. Numerical simulation is also employed to present the mechanism of jet-mainstream interaction. It is shown that, at the blowing ratio over 0.8, the optimal forward and lateral expansion angle lies in the medium range. Cooling effectiveness increases before the optimal value due to better film attachment but deteriorates after then due to coolant separation within the hole. In contrast, at the blowing ratio of 0.5, the results become different because the coolant attaches well enough that the change of the coolant dissipation rate appears more dominant. The competition of two factors, weaker kidney vortex entrainment and larger shear surface, leads to an unpredictable trend. Finally, suggestions are provided for the parameter selection on the blade suction surface. As a comparison, the same studies are numerically conducted on a flat surface. Distinctly, at high blowing ratio, the effectiveness increases monotonously without a drop at too large expansion because the absence of radial pressure gradient worsens jet attachment and magnifies the effect of promoting jet attachment.

Effect of Upstream Leakage Flow on Film Cooling Characteristic of a Turbine Convex Endwall

Abstract This paper investigates the effect of upstream leakage coolant flow on the film cooling performance of the convex endwall. The experiment is conducted in an annular passage with four vanes, and the endwall film cooling effectiveness distribution is measured by the pressure-sensitive paint technique. The near-wall flow field distribution predicted by computational fluid dynamics is employed to gain a deeper understanding of the influence of the passage secondary flow on the film cooling characteristic of the endwall. Furthermore, the effect of mass flow ratios (MFR = 0.75%, 1.0%, 1.25%, and 1.5%), leakage slot inclination angles (α = 30 deg, 45 deg, and 60 deg), density ratios (DR = 1.0, 1.5, and 2.0), as well as Reynolds number (Re = 2.0 × 105, 3.0 × 105, and 4.0 × 105) on the endwall film cooling is also investigated. Results indicate that the mass flow ratio has a great influence on the endwall film cooling effectiveness distribution, and a larger uncooled region can be observed when MFR is less than 1.25% due to the cooling air more easily being entrained by the secondary flow near the endwall. Reducing the inclination angle of the leakage slot enhances the axial velocity component of the coolant flow, thereby weakening the secondary flow near the endwall and improving the film cooling effectiveness distribution of the endwall. As the density ratio increases, the jet momentum of the leakage flow is reduced, particularly for higher MFR cases, which results in a significant reduction in the film cooling performance of the endwall. Besides, thinning the incoming boundary layer of the passage reduces the strength and size of the secondary flow in the passage and improves the endwall adiabatic effectiveness distribution when the Reynolds number is increased.

Investigation of aerothermal performance of blade tip with conical holes in transonic flow

The blade tip with conical holes is proposed in the current paper to improve the film cooling performance on the turbine blade tip. The film cooling performance of the blade tip with cylindrical holes is studied as a reference case. The pressure sensitive paint technique is adapted to obtain the tip film cooling effectiveness in transonic flow. The numerical simulation is used to obtain the tip flow field and aerodynamic loss. The cascade exit Mach number and inlet Reynolds number are 1.05 and 370000, respectively. The experiment and calculation are carried out at two tip clearance gaps of 0.7% and 1.5% and four mass-flow-ratios. The results show that at low mass flow ratios, the film cooling effectiveness of the blade tip with conical holes is significantly higher than that of the blade tip with cylindrical holes at the tip mid-chord region. Increasing the tip clearance gap from 0.7% to 1.5% shows a negative effect on the film cooling performance of the blade tip with conical holes in the tip mid-chord region, particularly for the low mass flow ratio. The pitch-wise averaged aerodynamic loss coefficient of the blade tip with cylindrical holes is lower than that of the blade tip with conical holes near the shroud.

Large Eddy simulation in optimizing trench configuration to improve cooling effectiveness of a laidback fan-shaped hole

In modern gas turbines, a thermal barrier coating (TBC) is used to protect the components of the turbine from the hot flow coming from the combustor, which results in the cooling holes on the blade surfaces being embedded in a 2D trench slot. In this study, large eddy simulations (LES) were carried out to investigate the effects of trench geometry on the film-cooling effectiveness of a shaped cooling hole. The shaped cooling hole is located on a flat surface with an injection angle of 30 degrees, and the blowing and density ratios are fixed at 1.5. Thirteen different designed cases were sampled using Box-Behnken method based on three different geometry parameters of the trench slot, trench height and upstream and downstream trench lengths. A genetic aggregation algorithm was applied to achieve the optimal trench configuration that maximizes the overall cooling effectiveness. The film-cooling performance computed by the LES method was validated for a reference case without a trench and three different trenched cases with the experiments using the PSP (pressure sensitive paint) technique. The cooling effectiveness of the trench cavity and flat plate was found to be significantly enhanced in cases of trenches with relatively greater trench height and less downstream trench length. The optimal trench configuration demonstrated less turbulent fluctuations in the mixing region, and the overall area-averaged adiabatic film-cooling effectiveness was improved by 23% in comparison with a reference hole without a trench.

Experimental and unsteady numerical investigations on cooling characteristics of trailing-edge cutback with effect of upstream film holes

This paper investigates the influence of film cooling characteristics of pressure-side film hole on trailing-edge cutback in the high-pressure vane of gas turbines. This paper employs the Pressure Sensitive Paint (PSP) technique and Particle Image Velocimetry (PIV) technique to obtain the time-averaged adiabatic film cooling effectiveness and details of the mixing region, respectively. Numerical simulations with the DDES turbulence model are also used to predict the flowfields. Two configurations are examined: one with a cutback without pressure-side film holes (Config A) and another with a cutback that includes pressure-side film holes (Config B). This paper investigates eight blowing ratios (Mslot = 0.3–1.2) of slot coolant in cutback for Config A and a suitable blowing ratio (Mhole = 0.4) of film holes for Config B, using both experimental and numerical methods. The results of both experiments and simulations for Config A and B show good agreement and reveal a non-monotonic trend of film cooling effectiveness with increasing blowing ratio. The non-monotonic trend observed in Config A is attributed to an increase in the velocity gradient in the boundary layer on the coolant side with increasing blowing ratio, which leads to a different shedding vortex structure. The results for Config B show that the coolant from the pressure-side film holes changes the mixing structure downstream of the lip by rebuilding the mainstream's shear layer on the mainstream side. Adiabatic film cooling effectiveness increases significantly under low and moderate slot blowing ratios, but non-monotonicity is maintained. The Fast Fourier Transform method is used to investigate the impact of the jet stream, which affects only the area downstream of the film holes, while other regions along the pitch-wise direction are less affected. This paper also attempts to combine the effectiveness empirical correlations of 2D slot and film holes using the superposition model to quantitatively analyze the deterioration of cooling effectiveness resulting from the mixing of coolant and mainstream.

Three-dimensional pressure field measurement on turbine guide vanes using a dynamic distortion correction endoscopic pressure-sensitive paint technique

Three-dimensional pressure field measurement on turbine guide vanes using a dynamic distortion correction endoscopic pressure-sensitive paint technique

Coupling of Volumetric Flowfield and Surface Effectiveness Measurements for Flat-Plate Film Cooling With Cylindrical Holes Using Tomographic Particle Image Velocimetry and Pressure-Sensitive Paint

AbstractIn this study, a series of time-averaged tomographic particle image velocimetry (TPIV) measurements are completed for simple angle, cylindrical film cooling holes on a flat plate with an inclination angle of 30 deg and a diameter of 4 mm. The flat plate is installed in a low-speed wind tunnel with a mainstream turbulence intensity of Tu=8% and an average velocity of 21.6 m/s. The blowing ratios of the jet range from M = 0.3 to M = 1.5, and the density ratio of the jet is fixed at DR = 1. The Reynolds number of the cooling jet varies from 1700 to 8400. The repeatability and accuracy of the tomographic particle imaging velocimetry (TPIV) measurements are compared against the results obtained by other flowfield measurement techniques. The results of the TPIV measurements are presented in velocity and vorticity iso-surface distributions in 3D, as well as 2D planar slices of velocity, vorticity, turbulence intensity, and Reynolds Stress distributions within the measurement volume. The characteristics of the flowfield are coupled with the detailed film cooling effectiveness distribution obtained using the pressure-sensitive paint (PSP) technique. An inverse relation among volumetric turbulence accumulation (TA) and surface film effectiveness, η, can be correlated.