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Vortex generators (VGs) are a passive method by which to alleviate boundary layer separation (BLS). The device-induced streamwise vortices propagate downstream. There is then lift-off from the surface and the vortex decays. The effectiveness of VGs depends on their geometrical configuration, spacing, and flow characteristics. In a high-speed flow regime, the VGs must be properly positioned upstream of the BLS region. Measurements using discrete pressure taps and pressure-sensitive paint (PSP) show that there is an increase in the upstream surface pressure and the downstream favorable pressure gradient. The effective distance for a flat plate in the presence of three VG configurations is determined, as is the height of the device (conventional and micro VGs).

The amplification factor transport transition model has been extended to include crossflow transition and applied to a rotor in hover. Validation of the crossflow model implementation has been perf...

Abstract Fast response pressure-sensitive paint (PSP) allows optical measurements of pressure fluctuations on a surface with high spatial and temporal resolution. This technique is evaluated for aeroacoustic measurements inside an aeroacoustic wind tunnel (AWT). The AWT is a test rig especially designed for investigating the excitation and propagation of sound under conditions typical for turbomachinery. The aim of this work is to compare the results of sound pressure measurements of tonal sound fields in a circular duct conducted with PSP and microphone arrays in order to assess the applicability of PSP in turbomachinery acoustics applications. A data analysis process is presented, which projects the camera image of the PSP data onto a given surface. To analyze the spatial pressure fluctuations, the PSP data are transformed in the frequency domain using pixel-wise fast Fourier transform. Measurements with a mean Mach number up to 0.109 and 5 kHz excitation frequency are conducted. An acoustic mode generator is used to excite the sound field with specific circumferential mode order. The pressure fluctuations obtained with the PSP measurement visualize the measured acoustic field well and allow early interpretation. The pressures of PSP and microphones are in good agreement; for example, the maximum detected deviation in pressure at 2700 Hz is 30 Pa. A preview on using radial mode analysis to decompose the acoustic field, measured by PSP, into acoustic modes is provided. The results are confirmed by a decomposition using conventional arrays of flush-mounted microphones. Graphical Abstract

High-resolution skin-friction fields are extracted from pressure-sensitive paint (PSP) data obtained in shock-wave/boundary-layer interaction (SWBLI). The method of extracting skin friction from su...

Effusion cooling in gas turbine combustors is complicated by swirling flows for anchoring flame, whereas miniature effusion cooling jets are highly directional. This work aims at understanding the ...

An experimental methodology was designed to study the effects of turbulent flow and shock/boundary-layer interaction (SBLI) on the postflutter response of a thin, buckled panel. The approach combin...

This paper reports on the combination of two surface measurement techniques, pressure-sensitive paints (PSPs) and photoelastic coatings (PECs), to measure full-field, dynamic pressure and strain fi...

This study experimentally investigated transonic cavity flows with different length-to-depth ( L/ h) ratios and yaw angles. Two rectangular models with L/ h = 6.14 and 21.5 were examined with yaw angles of 10°, 30°, and 45° under a flow of Mach 0.83. The flow was visualized using pressure-sensitive paint (PSP) to obtain the detailed pressure distribution inside the cavity models. The acquired PSP data were compared with experimental data measured using Kulite transducers, and these data showed favorable agreement. Gradual pressure increases inside the cavity model with L/ h = 6.14 were observed from the PSP measurements as open cavity flow. The flow impingement at the bottom of the cavity and the significant pressure rise inside the cavity model with L/ h = 21.5 were observed as closed cavity flow. The present study quantitatively visualized the evolution of the pressure distribution from symmetric to asymmetric for different yaw angles using porous PSP sensors.

Experiments were carried out to study the effects of compound angle, hole arrangement, and blowing ratio on the film cooling performance of multiple rows of holes on the suction surface of a turbine blade. The turbine worked at rotational speed of 600 rpm corresponding to the rotational Reynolds number of 5.36 × 105. Three rows of cylindrical holes arranged in line or in stagger were drilled on the rotor blade suction surface at the streamwise location of 12.4%, 17.8%, and 23.2%, respectively. Three compound angles, with the same streamwise angle of 45° but different lateral deflection angles of 45°, 0°, and −45°, were studied. The film cooling effectiveness was obtained using pressure sensitive paint (PSP) technique with average blowing ratios varied from 0.5 to 2.0. The results showed that the application of compound angle changes the jet direction in the near-hole region and makes the film spread laterally. Compared with the film cooling without compound angle, using positive and negative compound angle can improve overall average film cooling effectiveness by about 20% and 25%, respectively. The effects of the secondary flow also can be weakened. A stagger film trajectory arrangement can achieve more uniform film coverage with higher overall film cooling effectiveness. The film trajectory arrangement of a positive compound angle injection is determined by the combined effect of hole arrangement and blowing ratio. While, the film trajectory arrangement of a negative compound angle injection is almost the same as the hole arrangement and nearly does not change with the blowing ratio.

Pressure Sensitive Paint (PSP) technique has been increasingly applied to the experimental research of aerodynamics and thermodynamics due to its strengths of non-contact, high resolution results and large coverage area, etc. However, rarely has this technique been successfully used to the study of internal flow such as compressor cascade, since narrow flow passages would heavily restrict the acquisition of PSP images. In this paper, PSP technique was used to study the pressure distribution on a linear compressor cascade with large solidity of 2.3, where the view of recording camera can be heavily blocked due to adjacent blade surfaces. To help get integrated PSP images of the internal flow passage, dual camera system along with image processing tools like 3D reconstruction and image integration were adopted. The results showed that with the aid of such assistance, image results with good quality and readability could be obtained. Meanwhile, pressure data given by PSP were compared with data from traditional way of pressure taps and showed good consistency. Massive results of the entire cascade passage surface were given with different inlet Mach numbers and incidence angles. The results showed that PSP technique can integrally measure cascade tunnel of large solidity with the help of dual-camera system.

A simultaneous surface pressure and displacement measurement method that integrates pressure-sensitive paint (PSP) and binocular stereophotogrammetry is proposed. The assays were completed on the Φ4 m rotor test stand at China Aerodynamic Research and Development Center (CARDC). A single-shot lifetime approach was utilized to acquire the instantaneous pressure field on a rotor blade coated with PSP. At the same time, the PSP feature points were used to obtain the 3D coordinates of stereo cameras, which yielded the blade displacement field. The experimental results showed that the displacement measuring accuracy was better than 0.2 mm, and the pressure measurement accuracy was not affected, with Standard Deviation (STD) values below 700 Pa. The advantages of the proposed system are its simple structure, low cost, high accuracy and high test efficiency, which will offer a practical solution for the exploration of fluid–structure interplay. Hence, such a system is a prospective for the wind tunnel tests of helicopter rotor blades.

The thermal stability of sprayable fast-responding Pressure-Sensitive Paint (fast PSP) was investigated to explore the possibility for application in turbomachinery and hypersonic research with temperature above 100 °C. The first part of the study focused on a widely-used Polymer Ceramic PSP (PC-PSP). The effects of thermal degradation on its key sensing properties, including luminescent intensity, pressure sensitivity and response time, were examined for a temperature range from 60 to 100 °C. Severe degradation in intensity and pressure sensitivity was found as temperature reached 70 °C or higher, which would cause failure of PSP application in these conditions. Subsequently, a fast-responding Mesoporous-Particle PSP (MP-PSP) was developed which did not show degradation effects until 140 °C. The greatly improved thermal stability of MP-PSP was attributed to: selection of polymer with higher glass transition temperature (polystyrene) to delay the saturation effect of oxygen quenching as temperature increased; porous and hollow structure of particles for luminophore deposition that minimizes polymer–luminophore interaction. This new paint formulation has significantly raised the upper temperature limit of fast PSP and offers more opportunities for applications in harsh environment.

In this work, dual-luminophore self-referenced pressure sensitive paint (PSP) was prepared with siloxane precursors by using copolymerizable silane-functionalized carbon dots (SiCDs) as a reference probe and a newly synthesized silane-modified ruthenium complex (Ru-silane) as the sensitive probe respectively. The PSP is fully sprayable in the preparation of bi-layer thin coatings via a sol–gel process, by which a SiCD copolymerized silicone base layer was firstly constructed and subsequently covered by a Ru-silane grafted top layer. The resultant optical sensor is transparent, having a transmittance as high as 80%, besides the chemical bonding of the probes had favorably improved the stability of the luminescence properties. Based on the oxygen quenching mechanism, such transparent PSP coatings allowed efficient determination of the sudden changes of surface pressure in an inner flow channel with a time response of 1.3 ms, while the measurement can be performed from either the front side or the reverse side of the coating. Furthermore, the 2D pressure map can be quantified by calculating the intensity ratio of SiCDs to Ru-silane photoluminescence and thereby improved the accuracy of the measurement. We thus expect the transparent PSP coatings to be a useful tool in remote pressure and oxygen sensing in various fields, such as aircraft design and healthcare.

A rectangular cavity (L/D=5.67) with Mach 1.5 freestream was subjected to a large temporal variation in leading-edge blowing in order to experimentally investigate the effect on aerodynamic and aer...

Enhancement of the luminescent output of pressure-sensitive paint (PSP) has been achieved by adding silver nanostructures into a standard formulation by taking advantage of a metal-enhanced fluores...

Presence of a cavity changes the mean and fluctuating pressure distributions inside and near the cavity. For cylindrical cavity flow, the diameter-to-depth ratio is the dominant factor. In this study, flow is naturally developed along a flat plate with two different lengths, resulting in different incoming boundary layer thicknesses ahead of the cavity. The effect of Reynolds number based on incoming boundary layer thickness on characteristics of mean and fluctuating pressure distributions is addressed. Pressure sensitive paint was also used to visualize the mean surface pressure patterns. The effect of Reynolds number on the classification of compressible cylindrical cavity flow and self-sustained oscillating frequency is not significant. An increase in Reynolds number results in a reduction in the value of differential pressure or momentum flux near the rear edge. Keywords: Cavity flow, Compressible flow, Convection velocity, Open cavity, Oscillation

This work presents an experimental and numerical study of hypersonic transitional shock-wave–boundary-layer interaction, wherein transition occurs between separation and reattachment in the detache...

The characterization of pressure-sensitive paint (PSP) is affected by many physical and chemical factors, making it is difficult to analyze the relationship between characterization and influencing factors. An artificial neural network (ANN)-based method for predicting pressure sensitivity using paint thickness and roughness was proposed in this paper. The mean absolute percentage error (MAPE) for predicting pressure sensitivity is 6.5088%. The difference of paint thickness and roughness between sample and model surface may be a source of experimental error in PSP pressure measurement tests. The Stern-Volmer coefficients A and B are strongly linked. Pressure sensitivity is approximately equal to coefficient B, so coefficient A is predicted using pressure sensitivity based on the same ANN, and the MAPE of predicting A is 2.1315%. Then, we try to calculate the pressure by using the thickness and roughness on a model to predict pressure sensitivity and Stern-Volmer coefficient A. The PSP pressure measurement test was carried out at the China Aerodynamic Research and Development Center. Using the Stern-Volmer coefficient calculated by the in situ method, the method in this paper, and the sample calibration experiment, the root mean square errors (RMSE) of the pressure are 47.4431 Pa, 63.4736 Pa, and 73.0223 Pa, respectively.

We propose a markerless image alignment method for pressure-sensitive paint measurement data replacing the time-consuming conventional alignment method in which the black markers are placed on the model and are detected manually. In the proposed method, feature points are detected by a boundary detection method, in which the PSP boundary is detected using the Moore-Neighbor tracing algorithm. The performance of the proposed method is compared with the conventional method based on black markers, the difference of Gaussian (DoG) detector, and the Hessian corner detector. The results by the proposed method and the DoG detector are equivalent to each other. On the other hand, the performances of the image alignment using the black marker and the Hessian corner detector are slightly worse compared with the DoG and the proposed method. The computational cost of the proposed method is half of that of the DoG method. The proposed method is a promising for the image alignment in the PSP application in the viewpoint of the alignment precision and computational cost.

Degradation of fast response pressure-sensitive paints (PSP) above room temperature is a serious problem for PSP measurements in high-temperature environments. A standard polymer-ceramic PSP (PC-PSP) composed of platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin (PtTFPP), titania particles and poly(isobutyl methacrylate) (polyIBM) was characterized to elucidate the degradation mechanism. Applying a two-gate lifetime-based method, the PC-PSP has sufficient pressure and temperature sensitivities even at 100 °C, while the luminescence intensity significantly decreases during the test. Subsequent measurements on thermal and photostability as well as luminescence spectra reveal that the main cause of the degradation is the photodegradation of PtTFPP due to direct exposure of the dye molecules to the atmosphere. In order to suppress such degradation, a small amount of urethane resin is added to the dye solution as a simple additional step in the preparation of PC-PSP. The addition of the urethane resin significantly reduces the degradation of the PSP, although its time response is slightly slower than that of the standard PC-PSP.

Abstract This paper presents the performance of pressure-sensitive paint (PSP) for the direct measurement of species concentration on a porous surface with mass injection. It is used to measure the ability of an injected gas to reduce the mass transfer of freestream species to the surface. A porous alumina sample was sprayed with a PSP luminophore solution. The sample was installed into a flat plate model and exposed to hypersonic cross-flows in the Oxford High-Density Tunnel. Tests were conducted with no coolant injection, air injection, and nitrogen injection at increasing blowing ratios. Oxygen partial pressure maps on the transpiration-cooled surface were obtained for several conditions at unit Reynolds numbers between $$2.58{-}5.0 \times 10^7/ \mathrm{m}$$ 2.58 - 5.0 × 10 7 / m and blowing ratios between $$0.016{-}0.078\%$$ 0.016 - 0.078 % . The oxygen pressure decreases as the unit Reynolds number decreases and the blowing ratio increases. Graphic abstract

Pressure-sensitive films have been used for measurement in micro flow, but thin films have very limited intensity, resulting in poor signal-noise ratio (SNR). This paper presents a pressure-sensitive film whose emission signal is enhanced by silver nanoparticles (AgNPs) based on localized surface plasmon resonance (LSPR). Electronic beam evaporator and annealing furnace are used to fabricate silver nanotexture surface. PtTFPP and polystyrene are dissolved in toluene and then spin-coated on the silver nanotexture surface to prepare the pressure-sensitive films. Signal enhancement of film with AgNPs due to LSPR is analyzed and enhancement effect of samples with different particle sizes and spacer thickness are compared. Pressure and temperature calibrations are performed to assess the sensing performance of pressure-sensitive films. Pressure-sensitive films with AgNPs demonstrate signal enhancement due to LSPR and show promise for measurement in micro flow.

Pressure-Sensitive Paint (PSP) is a powerful measurement technique to obtain pressure distribution on a model of interest by measuring the emission intensity of the PSP coating with a camera. Since a PSP coating is prepared by applying a solution containing an organic solvent, generally, by sprayer, the properties such as the pressure- and the temperature-sensitivity depends on the skill of the person applying it. This fabrication process is one of the barriers to use of the PSP technique because of the legal restrictions on the use of organic solvents. Thus, a sticker-like PSP coating is useful because it does not require the use of organic solvent and the applying skill. In this study, we have fabricated freestanding Pressure-Sensitive Nano-Sheet (PSNS) by a sacrificial layer process using a spin-coating method. We employed Pt(II) meso-tetra(pentafluorophenyl)porphine (PtTFPP) as a pressure-sensitive dye and poly(1-trimethylsilyl-propyne) (PTMSP) and poly(L-lactic acid) (PLLA) as a polymer binder; thus, the PSNS samples based on PTMSP and PLLA were prepared. The pressure- and the temperature-sensitivity, the lifetime of the luminescence, and the quantum yield of the fabricated PSNS have been investigated. The pressure-sensitivity of PTMSP-based PSNS is higher than that of PLLA-based PSNS. Conversely, the quantum yield of PLLA-based PSNS is higher than that of PTMSP-based PSNS.

In recent years, researchers have developed a new method of measuring the pressure on the surface using sensitive paints. This is an optical technique for determining surface pressure distributions by measuring changes in the intensity, emitted by certain excited molecules. The main advantage of the method over traditional techniques is the high resolution of the information. The only limitation of the resolution of a global map generated by the PSP (pressure-sensitive paint) technique is given by the capabilities of the image capture device. This paper describes the development of a technology for obtaining pressure-sensitive paint, in laboratory conditions, as an advanced measurement technique. The method has an application in many fields such as automotive, aerospace, or even medical.

Surface pressure measurements were taken on a hemisphere-on-cylinder turret in a wind tunnel using pressure sensitive paint and fast response pressure transducers. Four different turret protrusion distances were tested to study the characteristics of the unsteady pressure field on the backside and wake of the turret. Proper orthogonal decomposition was used to identify the dominant spatial surface pressure modes acting on the turret in this parametric study. It was found that the further the turret protruded into the freestream flow, the more the surface pressure field became dominated by spanwise antisymmetric surface pressure distributions resulting from anti-symmetrical vortex shedding at a normalized frequency of approximately StD=0.2. For the case of the partial hemisphere, this anti-symmetrical vortex shedding was essentially absent, insinuating that at some protrusion distance, the surface pressure environment on the turret fundamentally changes. The normalized net force rms was calculated on the turret for each configuration. It was found that the greater the turret protrusion, the greater the net force acting in the spanwise direction.

Unsteady aerodynamic forces on large, slender aerospace structures are established in wind-tunnel tests that employ a limited number of dynamic pressure sensors and use a correlation-based approach...

Helical coil steam generators (HCSGs) are tube and shell heat exchangers under investigation due to their future in nuclear power applications. A model of an HCSG with a transverse pitch ra...

The discrete film hole is the most common form of film cooling configurations in the turbine vane and blade. To enhance the film cooling effect, the improved hole, such as expanding-shape hole, is being used to replace the traditional cylindrical hole in the vane and blade cooling design. However the slot film outflow is been seen as the best form of film cooling when compared to the discrete holes. The slot film cooling configuration is usually used in the trailing edge of turbine vane and blade, but cannot be used in the mid-body of turbine vane and blade, with be drawback of lower mechanical strength. The present paper used the slot film outflow on the laminated cooling configuration. With the ribs in the laminated cooling configuration, the novel configuration can remarkably overcome the mechanical drawback of the simple slot film cooling, and can enhance the film cooling effect of the laminated cooling configuration. To investigate the cooling effect of laminated configuration with slot film outflow, four kinds of specimens are designed, including the traditional design with discrete film hole (baseline), the rearrangement design with discrete film hole (case A), the novel design with discrete slot (case B), and the novel design with continuous slot (case C). The Conjugate heat transfer (CHT) computations and the Pressure Sensitive Paint (PSP) test methods are used to assess the overall cooling performance ( η overall ) and the adiabatic film cooling effectiveness ( η film ). The results show the two slot design cases (case B and case C) have higher film cooling effectiveness with more covered surface areas of film outflow, while performs lower flow resistance due to the lower flow velocity of the coolants in the slot. With the increase of Br, the film cooling effectiveness of two slot design cases (case B and case C) can keep increase, but the two hole design case (baseline and case A) cannot increase at area of Br > 0.55. At the blowing ratio near 0.96, for the baseline case, case A, case B, and case C, the area-averaged film cooling effectiveness is 0.26, 0.20, 0.68, and 0.50 respectively; and area-averaged the overall cooling effectiveness is 0.72, 0.81, 0.89, and 0.85 respectively; the flow frictions coefficients is 1.78, 2.15, 1.37, and 2.01 respectively.

Fluid–structure interactions were studied on a store with tunable structural natural frequencies in complex cavity flow. Different leading-edge geometries, doors, and internal inserts generated cav...

Time histories of pressure fluctuations on a generic, “hammerhead” launch vehicle model were measured using unsteady pressure-sensitive paint over a Mach number range of 0.6≤M≤1.2. The calibration ...

An endoscopic system for pressure-sensitive paint (PSP) measurement was presented in the current study, which was composed of a fiberscope, a diode laser and a color camera. The fiberscope was integrated by optical fibers (for transmitting the laser excitation) and a set of lenses (for delivering the PSP images to the camera). Here, a unique PSP with imprinted pattern was developed to address the key issue of limited viewing angle/area encountered during endoscopic measurement. This coating was based on a pressure-sensing luminophore PtTFPP and a recently developed mesoporous-particle binder, but with the addition of a pressure-insensitive reference dye (coumarin 6) forming a random dot pattern. The emission of PtTFPP and reference dye matched with the red and green channels of the color camera, respectively. The randomly distributed dots provided highly distinguishable features required for image stitching operation. This allowed the establishment of image processing algorithms that could combine a series of PSP images (scanned over the measurement field) into a full-field image. Meanwhile, the issue of spectral leakage from the emission of reference dye into the red channel was identified, and a correction method was proposed to remove the related measurement error. This PSP along with the endoscopic system was demonstrated in film cooling measurement on a blade in low-speed flow. The current method provides a practical solution for PSP applications in test environments with limited or even no optical access.

Film cooling techniques have been widely applied to gas turbine engines to protect the components from hot combustion gas. In this study, the shape of the laidback fan-shaped hole with a lateral expansion angle of 10 degrees was optimized through the Reynolds Averaged Navier-Stokes (RANS) analysis. Results by numerical analysis were validated with the corresponding experimental results obtained by the pressure sensitive paint technique (PSP). For optimal hole shape derivation, the design points were selected through the Latin Hypercube Sampling (LHS) method for three design variables: injection angle, metering length, and forward expansion angle. The overall averaged effectiveness was used as the objective function. Results showed that the overall film cooling effectiveness of the optimal holes derived by the response surface method and the Kriging method were higher than that of the reference hole by 4.5% and 7.5%, respectively. Generally, holes with a higher area ratio (AR) showed higher overall film cooling effectiveness. However, the interaction between each shape parameter should be considered to derive the optimal hole shape.

An optimization framework is developed for the film cooling hole shape design to achieve highest film cooling effectiveness with affordable cost. A key to this design method is the development and applications of a multi-fidelity model (MFM) to improve the efficiency of surrogate model construction. To construct multi-fidelity model, empirical correlations from existing literature are utilized as low-fidelity data and Reynolds-Averaged Navier-Stokes (RANS) simulations provide high-fidelity data. Compared with single-fidelity surrogate models, multi-fidelity model developed in this work combines vast existing knowledge about shaped film cooling hole and three dimensional numerical simulation. As a result, the computation cost has been substantially decreased by 64.5% while accuracy is maintained with similar level, which provides a firm basis for the optimization. Considering three geometric parameters as design variables, i.e. laidback angel, lateral angle, and hole length-diameter ratio, the shaped hole is optimized with genetic algorithm (GA) combined with sequential quadratic programming (SQP) algorithm. After the optimization, an experiment campaign is further carried out to validate the optimization result using pressure sensitive paint (PSP) technology. With current multi-fidelity model, the spatially averaged film cooling effectiveness has been improved by 39 % compared to the baseline, which is an already well-designed shaped hole and the improvement is also verified by experiment. This work verifies the effectiveness of current multi-fidelity model for the design and optimization of shaped film cooling hole for better performance.

Detailed film cooling effectiveness distribution for a gas turbine blade under the effects of unsteady wakes and oncoming free-stream turbulence intensities was obtained using pressure sensitive paint (PSP) technique. Tests were performed on a linear cascade at Reynolds number of 3.85 × 105 based on the blade chord at cascade exit. Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The test blade has three rows of compound angled cylindrical film holes at the leading edge, five rows of laid-back fan-shaped holes on the pressure surface and three rows of laid-back fan-shaped holes on the suction surface. The wake Strouhal number was varied from 0 to 0.36 and three mass flux ratios were determined. The oncoming free-stream turbulence intensities are 2.7% and 26.9%, respectively. Results show that the effect of the mass flux ratio on the film cooling effectiveness decreases under the high turbulence intensity and unsteady wake conditions. In most regions of the blade surface, the film cooling effectiveness decreases with the increase of wake Strouhal number, and the free-stream turbulence superimposed on the unsteady wake reduces the film cooling effectiveness further. The effect of the unsteady wake decreases under the high free-stream turbulence conditions.

The pressure field of plasma flow induced by surface-dielectric-barrier-discharge plasma actuators in quiescent air is difficult to measure accurately due to the very slight variations in pressure ...

The use of nonlinear, dynamic methods for the simulation of aerospace structures has increased dramatically in recent years [1]; however, very little relevant experimental data exists to properly guide these developments. An experimental campaign was initiated by the AFRL Structural Sciences Center (SSC) for three reasons: (1) to observe and measure the effect of turbulence, shock boundary-layer interactions (SBLI) and heated flow on an aircraft-like panel; (2) to explore severe structural events (dynamic instabilities and material failure); and (3) to refine full-field and non-contacting experimental measurement techniques necessary to characterize the flow environment and structural response. All of the objectives were achieved. The panel response to turbulent, heated flow and sensitivity to panel back-pressure modulation was studied, with large-deformation limit cycle behavior leading to panel failure, observed and measured. For the first time, the 3D Digital Image Correlation (DIC) technique was also used to record the panel behavior while filming through the flow and SBLI environment. Finally, fast reacting pressure sensitive paint (PSP) was used, concurrently with 3D DIC, to record the dynamic pressure across the panel surface.

A numerical study was conducted to evaluate the applicability of the heat/mass transfer analogy to leading edge film cooling on a first-stage vane. A typical showerhead configuration was taken into account, thus including four staggered rows of evenly spaced cylindrical holes, angled at 45° towards the tip. The investigation was carried out at low speed (isentropic exit Mach number of Ma2is = 0.2), inlet turbulence intensity of Tu1 = 1.6% and 13%, and three different blowing ratios (BR = 2.0, 3.0 and 4.0). Steady-state simulations were conceived to mimic the pressure sensitive paint (PSP) technique aiming to measure the adiabatic film cooling effectiveness (η) in the leading edge region, under a density ratio of DR = 1 and 1.5. With the mainstream flow assumed to be air at ambient temperature, the desired DR was obtained by injecting coolant as air at different temperature from the mainstream (namely, heat transfer approach) or as isothermal foreign gas (namely, mass transfer approach). Despite the dominant effect of the DR on η, results indicated that the heat/mass transfer properties of the coolant are to be considered when comparing film cooling performance, at matched BR conditions. At low inlet turbulence intensity, the heat/mass transfer analogy was found to be applicable only to the lowest BR of 2.0. Its validity was extended to the medium BR of 3.0, in case of DR = 1.5, provided that the leading edge is approached by high turbulence intensity flow.

Adiabatic film effectiveness and heat transfer coefficient were determined for a full-coverage effusion cooled surface which simulates a portion of a gas turbine blade. Adiabatic film effectiveness and heat transfer coefficient were measured with low thermal-conductivity plastics using pressure sensitive paint and steady liquid crystal, respectively. The blowing ratio ranged from 0.5 to 2.5 with the density ratio of DR = 1.5. Geometrical parameters investigated included wall thickness (from 1.0D to 2.5D) and jet-injection directions (forward and backward injections). Local, laterally-averaged, and area-averaged adiabatic film effectiveness and heat transfer coefficients were shown to illustrate the geometrical parameter effects. Comparison of net heat flux reduction was conducted to provide an overall heat transfer estimation. Results showed that decreasing wall thickness results in opposite impacts for forward and backward injections. Also observed was that adopting backward injection for thin full-coverage effusion plate provided the highest adiabatic film effectiveness, heat transfer coefficient, and net heat flux reduction for most blowing ratios.

Polymer/ceramic pressure sensitive paint (PC-PSP) is an optical fast-responding pressure sensor. PC-PSP consists of a polymer and particles as the material for a porous binder layer, and a pressure-sensitive luminophore. The solution of the polymer and particles, and then the solution of the luminophore are separately applied to a model surface. The response time of PSP is mainly determined by the thickness and oxygen diffusivity of the binder layer. However, we found that PC-PSP showed the significantly different response time depending on the solvents for the luminophore despite the same total thickness of the binder layer. Therefore, we investigated the effect of solvents in dissolving luminophore on the PC-PSP characteristics including response time, pressure sensitivity, and luminescence lifetime. PC-PSP’s prepared with solvents for luminophore that poorly dissolve the polymer in the binder layer achieved a faster response time of those prepared with solvents that can dissolve the polymer. Furthermore, it was also found that the solvents caused the change in the response time, luminescence intensity and luminescence lifetime of PC-PSP. We have concluded that the different solubility of the solvents may provide the different state of porous structure and the local distribution of luminophore in the binder layer, and it causes the variation of the dynamic and static characteristics of PC-PSP.

We developed and evaluated an anodized-aluminum pressure-sensitive paint (AA-PSP) with new formulations of free-base porphyrin, H2TCPP, as an optical unsteady pressure sensor. The luminophore H2TCPP has quite a short fluorescent lifetime (2.4 ns on the condition of the AA-PSP). The fluorescence spectroscopy result shows that the excitation wavelength of H2TCPP corresponds to violet-colored (425 nm) and green-colored (longer than 520 nm) lights. The pressure sensitivity is sufficiently high for the pressure sensor (0.33–0.51%/kPa) and the temperature sensitivity is very low (0.07–1.46%/K). The photodegradation of the AA-PSPs is not severe in both excitation light sources of the green LED and the Nd:YAG laser. The resonance tube experiment result shows the cut-off frequency of the AA-PSPs is over 9.0 kHz, and the results of the shock tube experiment show the 10 µs order time constant of the normal shock wave.

Gas turbine film cooling creates complicated and highly unsteady flow structures. This study seeks to examine the unsteady characteristics created by different cooling hole inlet geometries using a fast-response pressure-sensitive paint (PSP) technique able to capture time-accurate measurements at 2000 frames per second, resolving frequencies up to 1000 Hz. Time-accurate and time-averaged measurements are used to evaluate the performance of a plenum-style inlet and a crossflow-style inlet in varying turbulence environments over a flat plate. The results of this study are intended to begin the process of breaking down widely accepted time-averaged film effectiveness trends into the cumulative effects of freestream turbulence and momentum flux ratio, with emphasis on the cooling jet motions they cause. Jet behaviors observed in this study include a sweeping oscillation, unsteady attachment and separation from the plate, and time-accurate and time-averaged flow bias. Cooling hole inlet geometry and momentum flux ratio affect the core of the jet, and freestream turbulence affects the periphery of the jet. Crossflow-fed cooling holes show bias to the upstream side of the cooling hole with respect to the internal crossflow direction. Plenum-fed cooling holes outperform crossflow-fed cooling holes, and the difference grows with increasing momentum flux ratio. The frequency of both plenum- and crossflow-fed cooling jet motions is influenced by the freestream turbulent velocity fluctuations. The resulting mode shapes show dominant side-to-side sweeping for higher turbulence environments and a separation and reattachment motion for lower turbulence environments. At higher momentum flux ratio, the jets were seen to increasingly favor separation and reattachment motions. The results of this study are intended to better inform existing predictive tools. With a better understanding of the time-accurate behaviors responsible for creating the commonly accepted time-averaged coolant distributions, simple predictive tools may be better equipped to accurately model film cooling flows.

This paper describes an experimental activity carried out to investigate the potential of V-shaped holes for film cooling a high-pressure nozzle guide vane. The newly designed V-shaped scheme was compared with standard laidback fan-shaped holes. The influence of showerhead cooling was also assessed. Different injection conditions were examined under the same cascade operating condition using CO2 as a coolant. The quality of holes geometry and their discharging behavior was first characterized. Then, dual-luminophore pressure-sensitive paint (PSP) was used for measuring the adiabatic film cooling effectiveness all over the vane surface. Results of the current work showed that using a V-shaped hole configuration would give nearly the same surface protection as standard shaped holes with a reduced number of holes and, thus, at lower coolant flow consumption.

This work is an experimental study of film cooling effectiveness on a blade tip in a stationary, linear cascade. The cascade is mounted in a blowdown facility with controlled inlet and exit Mach numbers of 0.29 and 0.75, respectively. The free stream turbulence intensity is measured to be 13.5 % upstream of the blade’s leading edge. A flat tip design is studied, having a tip gap of 1.6%. The blade tip is designed to have 15 shaped film cooling holes along the near-tip pressure side (PS) surface. Fifteen vertical film cooling holes are placed on the tip near the pressure side. The cooling holes are divided into a 2-zone plenum to locally maintain the desired blowing ratios based on the external pressure field. Two coolant injection scenarios are considered by injecting coolant through the tip holes only and both tip and PS surface holes together. The blowing ratio (M) and density ratio (DR) effects are studied by testing at blowing ratios of 0.5, 1.0, and 1.5 and three density ratios of 1.0, 1.5, and 2.0. Three different foreign gases are used to create density ratio effect. Over-tip flow leakage is also studied by measuring the static pressure distributions on the blade tip using the pressure sensitive paint (PSP) measurement technique. In addition, detailed film cooling effectiveness is acquired to quantify the parametric effect of blowing ratio and density ratio on a plane tip design. Increasing the blowing ratio and density ratio resulted in increased film cooling effectiveness at all injection scenarios. Injecting coolant on the PS and the tip surface also resulted in reduced leakage over the tip. The conclusions from this study will provide the gas turbine designer with additional insight on controlling different parameters and strategically placing the holes during the design process.