Application Of Pressure Sensitive Paint Research Articles

Application of pressure-sensitive paint for explosive blast measurements

This study demonstrates the application of fast response pressure-sensitive paint (PSP) to explosively driven blast wave testing. A sprayable polymer ceramic fast response PSP was applied to an aluminium disc before being coated with platinum porphyrin compound as the active luminophore. The disc was then exposed to a blast wave and the response was measured using a high-speed video camera. The PSP measured the transit of the incident shock wave clearly, albeit with a slight response delay following the instantaneous change in pressure. A time domain-based method for improving temporal response, whilst considering both spatial and temporal effects, is described. This study clearly demonstrates that the spatial distribution of a blast wave on a surface may be captured by PSP technology. Integrated parameters such as impulse can correctly be characterised using this method. This technology offers an enhanced and more efficient way of characterising blast.

A comprehensive deviation analysis of film cooling effectiveness measurements using pressure sensitive paint under various conditions

The application of pressure-sensitive paint (PSP) has been extensively utilized to measure the effectiveness of film cooling. During the experiment, the pressure fields for the air-jet case and the foreign-gas-jet case are usually assumed to be identical. However, when there is a disparity in density between the foreign gas and the air, the difference in pressure distributions cannot be disregarded in high-speed or complex flow conditions. The film cooling effectiveness deviation caused by pressure variation was analyzed by formula derivation. The deviation distribution was obtained through the numerical simulation of the experimental process. The results indicated that the deviation is universal under various conditions. For the film cooling on a flat plate, there is a butterfly-shaped negative deviation region and a narrow symmetrical positive deviation zone. The presence of the compound angle significantly increases the deviation and results in a positive deviation region upstream of the hole. The measurement deviation is widely distributed and exhibits significant magnitudes on the blade tip. The deviation range on the suction side is primarily concentrated near the hole. Specifically, the deviation on the pressure side can be almost neglected. A correction method is proposed, involving the use of an oxygen mixture with the same density as the foreign gas and the same oxygen mole fraction as air. This method proves effective in significantly reducing the deviation in all cases.

Application of pressure-sensitive paint for the characterization of mixing with various gases in T-type micromixers

In this study, the mixing of various gases in T-type micromixers was investigated using the pressure-sensitive paint technique. Three gases, namely nitrogen, argon, and helium, were mixed with oxygen at various flow speeds between 3 and 50 m/s. These three gases were selected because of their differences in terms of density, viscosity, and diffusion coefficients. Symmetric flow in the laminar flow regime and bifurcation flow in the engulfment flow regime were visualized through experimentation. Numerical simulation was also performed, and the numerical data were compared with the experimental data. A favorable agreement was obtained between the experimental and numerical results for the laminar flow regime. The effects of the properties of the mixed gases as well as the evolution of the mixing quality along the mixing channel in the T-type micromixer are discussed.

Pressure-sensitive paint with imprinted pattern for full-field endoscopic measurement using a color camera

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.

Data mining of a clean signal from highly noisy data based on compressed data fusion: A fast-responding pressure-sensitive paint application

A data mining approach based on compressed data fusion is developed to extract a clean signal from highly noisy data and it has been successfully applied to flow measurement using fast-responding pressure-sensitive paint (fast PSP). In this approach, spatially resolved but noisy full-field data are fused with clean but scattered data to reconstruct full-field clean data. The fusion process is accomplished based on a compressed sensing algorithm, which has shown significantly improved performance compared with low-dimensional analysis. This is because, in low-dimensional analysis such as proper orthogonal decomposition (POD), the selection criteria of proper POD modes for reconstruction are usually based on subjective observation and the mode coefficients can be severely distorted by noise, which restricts the applications of this method to complicated flow phenomena and leads to a low-quality reconstruction. The solutions to these two problems can be expressed via mathematical optimization by determining the optimal coefficients to reconstruct clean data using the most relevant POD modes. Here, compressed sensing is used as a suitable solution to explore the sparse representation of scattered clean data based on the POD modes obtained from noisy full-field data. A high-quality reconstruction can be obtained using the optimized coefficients. The new method is first demonstrated by using fabricated patterns, demonstrating a reduction of 75% in the reconstruction error compared with POD analysis. It is thereafter successfully applied to recover the unsteady pressure field induced by a cylinder wake flow at low speed. Fast PSP measurement and microphones are used to obtain full-field but noisy pressure field data and scattered but clean data, respectively. In the cases of single and step cylinders, the reconstruction errors are approximately 5% and 25%, respectively, and the accuracy of reconstruction depends on the low dimensionality of the flow phenomena and the total number of microphone sensors. The current technique provides a reliable method to recover clean signals from strong noise, with significant potential for applications to flow measurement, control, and monitoring.

경화방법, 실험시간, 카메라 및 조명 조사 각도가 압력감응페인트의 보정 결과에 미치는 영향

Pressure Sensitive Paint (PSP) has been widely applied to measure the aerodynamic performance in the wind tunnel tests. Recently, researchers also have tried to apply the PSP in gas turbine film cooling study. Those PSP applications require proper PSP calibration curve in order to obtain accurate results. In this study, some factors which may affect the PSP calibration and test results, including the PSP curing method, the time exposed to photoluminescence condition, and the angle between the PSP coated surface and camera, were investigated experimentally. Results showed that the PSP calibration curves were significantly affected by the thickness of the PSP coating and the relative angle of camera and light to the PSP coated surface. However, the PSP curing method was not dominant factor affecting the PSP calibration result.

Pressure-Sensitive Paint Application to an Oscillating Shock Wave in a Transonic Flow

This paper presents an application of the pressure-sensitive paint technique to investigate two-dimensional unsteady flow in a transonic channel. This work is a contribution to the study of the transonic interaction between an oscillating shock wave and a separated boundary layer in a channel flow. The shock-wave oscillation is forced by the periodic variation of the section of a second throat by means of a rotating elliptical shaft located in its section. The channel’s lower wall is equipped with a contour profile, or bump, allowing for flow separation. To achieve a reduced response time for surface pressure measurements, we use anodized-aluminum coating as pressure-sensitive paint instead of usual paint. An aluminum insert including the bump was manufactured and coated with anodized-aluminum pressure-sensitive paint. Images were acquired by using a high-speed camera, and pressure-sensitive paint results were compared with pressure tap and Kulite sensor measurements implemented in the insert. Spectral analysis was carried out to assess the ability of anodized-aluminum pressure-sensitive paint for understanding unsteady aspects of such a complex channel flow.

GS32 ポリマー型感圧塗料を用いた低速流れ場における非定常圧力計測技術

Pressure sensitive paint (PSP) is a useful noncontact measurement technique to obtain continuous pressure distribution on solid surfaces. The application of PSP to low speed flows in mechanical engineering fields, including unsteady flow measurement related to analysis of aerodynamic noise, is highly demanded. Polymer-based PSP has high pressure sensitivity for low-speed flow field, but the unsteady response of the polymer-based PSP is not examined enough. In this study, we investigate the unsteady response of the polymer-based PSP, to evaluate the feasibility of the polymer-based PSP as a measurement tool for unsteady low-speed flows. We have applied the polymer-based PSP in low-speed flow to measurement of unsteady pressure distribution around a circular cylinder, and compared the amplitude spectra of PSP and that of pressure probe, which are obtained by FFT analysis. Furthermore we have visualized the distribution of the integrated intensity of the PSP amplitude spectrum around the peak, to visualize the area with large pressure fluctuation on the cylinder.

Application of pressure-sensitive paint to low-speed flow around a U-bend of strong curvature

Pressure measurements are traditionally made using pressure taps connected to a transducer. These measurements are labor-intensive, expensive and only yield discrete values. Pressure-sensitive paint is a method of optically measuring the pressure across an entire model. Originally designed for use in transonic flow, pressure-sensitive paints are absolute pressure sensors. Therefore, application of pressure-sensitive paint to low-speed flow represents a significant challenge to researchers. This study investigates the surface pressure distribution around a U-bend of sharp curvature with three different inlet velocities: 29.7, 21.5 and 12.0ms−1. The absolute accuracy of the paint has been measured and compared with previously published literature and empirical relations. The paint was excited using two LED lamps, and full-field pressure maps have been gathered using a CCD camera. The absolute accuracy of the pressure measurements is ultimately limited by CCD shot noise, but is more commonly limited by the temperature-induced error and the microheterogeneity of the painted surface.

微小流路壁面における圧力分布の可視化

In micro gas flows, some interesting phenomena at/near a wall, velocity slip, temperature jump, and thermal transpiration, play an important role; thus, the development of a measurement technique, which measure a physical quantity at a wall, is very important. The pressure-sensitive paint (PSP) technique has potential as a diagnostic tool for pressure measurement of a solid surface. However, the application of PSP to micro gas flow measurement is very difficult, because the conventional PSP is too thick and does not have sufficient spatial resolution. Pressure-sensitive molecular film (PSMF) with ordered molecular assemblies has been developed. PSMF is fabricated by the Langmuir-Blodgett method. We also developed a micro channel by the PDMS micro-molding technique with mixing a pressure-sensitive dye into PDMS: i.e., a micro channel fabricated by PSP, which is named PSCC. In this paper, we show the PSMF/PSCC fabrication procedure and the applicability of them to micro gas flow measurement.

Blade Tip Pressure Measurements Using Pressure-Sensitive Paint

This paper discusses the application of pressure sensitive paint using laser-based excitation for measurement of the upper surface pressure distribution on the tips of rotor blades in hover and simulated forward flight. The testing was conducted in the Rotor Test Cell and the 14- by 22-ft Subsonic Tunnel at the NASA Langley Research Center on the General Rotor Model System (GRMS) test stand. The Mach-scaled rotor contained three chordwise rows of dynamic pressure transducers for comparison with PSP measurements. The rotor had an 11 ft 1 in. diameter, 5.45 in. main chord and a swept, tapered tip. Three thrust conditions were examined in hover, C(sub T) = 0.004, 0.006 and 0.008. In forward flight, an additional thrust condition, C(sub T) = 0.010 was also examined. All four thrust conditions in forward flight were conducted at an advance ratio of 0.35.

G403 感圧塗料を用いた低速流れ場における非定常計測技術(GS4-1 計測技術,一般セッション)

Pressure sensitive paint (PSP) is a useful noncontact measurement technique to obtain continuous pressure distribution on solid surfaces. The application of PSP to low speed flows in mechanical engineering fields, including unsteady flow measurement related to analysis of aerodynamic noise, is highly demanded. In this study, we clarify the feasibility of PSP as a measurement tool for unsteady low-speed flow fields. Because the response time depends on the square of the thickness of the PSP layer, we have developed the thinner-layer PSP to improve its time response, and the dependence of the thickness of PSP layer on pressure sensitivity and time response was verified. Furthermore we have applied the PSP to measurement of pressure distribution around the circular cylinder in steady flow, to clarify the problems when PSP is applied to measurement of unsteady pressure distribution in low speed flows.

Surface Pressure Measurements on Supercritical Airfoil Employing Pressure -Sensitive Paint

Pressure-sensitive paint (PSP) technique has been broadly employed for qualitative and quantitative purposes in engineering and laboratory because of its prominent advantages of time-saving, cost-efficient and continuous pressure distribution since late 1980s, despite of its potential for more precise accuracy. Preliminary tests on supercritical airfoil have een conducted with in-house, single-component fluorescent PSP in 0.6×0.6 m transonic wind tunnel by self-established measurement system. The tunnel was operated at Mach number from0.6 to 0.9 and angles of attack from zero to 2 degree. Traditional pressure scanning method, PSI, was employed simultaneously during tests. The fact that PSP results are qualitatively consistent with that of PSI displays potential perspective of national PSP applications for more details about flow field.

Pressure-sensitive channel chip for visualization measurement of micro gas flows

We have developed a new pressure sensing tool named pressure-sensitive channel chip (PSCC) by combining the pressure-sensitive paint (PSP) technique with the poly(dimethylsiloxane) (PDMS) micro-molding technique. The PSP technique based on the oxygen quenching of luminescence is a potential diagnostic tool for pressure measurement of micro gas flows. However, the application of PSP to micro scale measurement is very difficult, because the thickness and the surface roughness of conventional PSPs cannot be neglected compared with the characteristic length of micro channels, and the spatial resolution is not enough for micro scale measurements due to the aggregations of luminophore. PSCC is fabricated with PDMS containing a pressure-sensitive luminophore; thus PSCC is a micro channel which itself works as a pressure “distribution” sensor. A micro converging-diverging nozzle with the throat width of 120 μm was demonstrated. The pressure distribution on the nozzle surface was successfully obtained by PSCC without the shortcomings of conventional PSPs.

마이크로 유동에서 PtOEP/PS 박막을 이용한 용존 산소 농도장의 정량적 가시화

It is highly needed to measure the dissolved oxygen (DO) concentration field in water for a variety of purposes such as biological, industrial, environmental monitoring and medical application. Application of PSP (Pressure Sensitive Paint) which is sensitive to oxygen concentration has been carried out to measure DO concentration field using PtOEP/PS film and intensity based method under the UV-LEDs illumination. A micro round water jet having 100% of DO was obliquely impinged on to a PtOEP/PS film coated plate placed in a 0% of DO water container. DO concentration fields on the impinging plate were quantitatively visualized with a <TEX>$2.94\;{\mu}m$</TEX> of spatial resolution. Through pixel-by-pixel calibration, uncertainty of each pixel by different sensitivity, different dye concentration and non-uniformity of illumination was removed. It is demonstrated that the high DO concentration region was coincided with the impingement area. The DO concentration gradient due to DO diffusion was affected by Reynolds number.

Extension and characterization of pressure-sensitive molecular film

Pressure-sensitive paint (PSP) has the potential as a diagnostic tool for pressure measurement in high Knudsen number regime because it works as a so-called “molecular sensor”. However, there are few reports concerning application of PSP to micro-devices, because conventional PSPs are too thick owing to polymer binders. In our previous work, we adopted the Langmuir–Blodgett (LB) technique to fabricate the pressure-sensitive molecular film (PSMF) using Pd(II) Mesoporphyrin IX (PdMP), which has pressure sensitivity only in the low pressure range (below 130 Pa). In this study, aiming for pressure measurement under an atmospheric pressure condition, we have constructed four samples of PSMFs composed of Pt(II) Mesoporphyrin IX (PtMP), Pt(II) Mesoporphyrin IX dimethylester (PtMPDME), Pt(II) Protoporphyrin IX (PtPP) and Cu(II) Mesoporphyrin IX dimethylester (CuMPDME) as luminescent molecules. The pressure sensitivity of those PSMFs was measured, and it was clarified that the pressure sensitivity of PSMF-PtMP is the highest among the four samples. Moreover, the temperature dependency of PSMF-PtMP was investigated, and we found that the temperature dependency of PSMF is dominated not by the oxygen diffusion in the layer, but by non-radiative deactivation process of excited luminescent molecules.

A review of pressure-sensitive paint for high-speed and unsteady aerodynamics

The current paper describes the development of pressure-sensitive paint (PSP) technology as an advanced measurement technique for unsteady flow fields and short-duration wind tunnels. Newly developed paint formulations have step response times approaching 1 μs, making them suitable for a wide range of unsteady testing. Developments in binder technology are discussed, which have resulted in new binder formulations such as anodized aluminium, thin-layer chromatography plate, polymer/ceramic, and poly(TMSP) PSP. The current paper also details modeling work done to describe the gas diffusion properties within the paint binder and understand the limitations of the paint response characteristics. Various dynamic calibration techniques for PSP are discussed, along with summaries of typical response times. A review of unsteady and high-speed PSP applications is presented, including experiments with shock tubes, hypersonic tunnels, unsteady delta wing aerodynamics, fluidic oscillator flows, Hartmann tube oscillations, acoustics, and turbomachinery. Flowfields with fundamental frequencies as high as 21 kHz have been successfully measured with porous PSP formulations.

Combined application of pressure sensitive paint and particle image velocimetry to the flow above a delta wing

The pressure sensitive paint (PSP) and particle image velocimetry (PIV) techniques are applied to the flow around a delta wing. These investigations are a contribution to the International Vortex Flow Experiment 2 (VFE-2). The delta wing is equipped with rounded as well as with sharp leading edges. To demonstrate the advantages of a combined application of PSP and PIV for flow investigation the results of a specific case are discussed, where an inner and outer primary vortex above the delta wing with rounded leading edges develop.

Development of pressure sensitive molecular film applicable to pressure measurement for high Knudsen number flows

Experimental analyses of thermo-fluid phenomena of micro- and nano-flows with high Knudsen number need the measurement techniques based on interaction of atoms or molecules with photons. The pressure-sensitive paint (PSP) technique has potential as a diagnostic tool for pressure measurement in the high Knudsen number regime because it works as a so-called “molecular sensor”. However, application of PSP to micro devices is very difficult because the conventional PSP is too thick owing to the use of polymer binder and does not have sufficient spatial resolution for pressure measurement of micro-flows. In this study, we have adopted the Langmuir-Blodgett (LB) technique to fabricate pressure sensitive molecular films (PSMFs) using Pd(II) Octaethylporphine (PdOEP) and Pd(II) Mesoporphyrin IX (PdMP) to resolve ordinary PSPs problems, and have tested these PSMFs to evaluate the feasibility of the pressure measurement around micro-devices. It is clarified that the PSMF composed of PdMP has higher sensitivity than that of PdOEP. Since it is also considered that the sensitivity of PSMFs can be increased by introducing arachidic acid (AA) as spacer molecules of LB films to prevent the aggregation of luminescent molecules, we have produced PSMFs with several molar ratio of PdMP to AA. At the most suitable ratio, the PSMF has high sensitivity in the low pressure region with high Knudsen number, even if the amount of the luminescent molecules in the PSMF layer is smaller than that in conventional PSPs. This result indicates that the PSMF is feasible to measure the pressure in high Knudsen number flows such as micro-flows.

Molecular number flux detection using oxygen sensitive luminophore

Experimental analyses of thermofluid phenomena with a high Knudsen number, related to low-density gas flows or nanotechnologies, need the measurement techniques based on atoms or molecules, such as emission and absorption of photons. Because the principle of the pressure sensitive paint (PSP) technique is based on oxygen quenching of luminescence, the technique has the capability to be applied to high Knudsen number flows such as microflows and low-density gas flows. In this study, to inspect the feasibility of PSP for measurement of pressure on a solid surface in high Knudsen number flows, fundamental properties of three types of PSP [palladium tetrakis (pentafluorophenyl) porphyrin, palladium octaethylporphyrin (PdOEP), and platinum tetrakis (pentafluorophenyl) porphyrin bound by poly[1–(trimethylsilyl)-1–propyne] (poly(TMSP))] are examined especially in the range of pressure below 130 Pa (about 1 Torr). As an application of PSP to high Knudsen number flows, we measure the pressure distribution on a jet-impinging solid surface using PdOEP∕poly(TMSP) with very high sensitivity. Moreover, the “pressure” distribution obtained by the PSP is compared with the distribution of the molecular number flux onto the solid surface to investigate the feasibility of number flux measurement by PSP.