Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session M14: Experimental Techniques IV |
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Chair: Philippe Blanc Benon, Ecole Centrale de Lyon Room: 317 |
Tuesday, November 22, 2011 8:00AM - 8:13AM |
M14.00001: High-Temperature Surface Thermometry Technique based on Upconversion Nano-Phosphors C. Combs, N. Clemens, X. Guo, H. Song, H. Zhao, K.K. Li, Y.K. Zou, H. Jiang Downconversion thermographic phosphors have been extensively used for high-temperature surface thermometry applications (e.g., aerothermodynamics, turbine blades) where temperature-sensitive paint is not viable. In \textit{downconversion} techniques the phosphorescence is at longer wavelengths than the excitation source. We are developing a new \textit{upconversion} thermographic phosphor technique that employs rare-earth-doped ceramics whose phosphorescence exhibit a strong temperature dependence. In the upconversion technique the phosphor is excited with near-IR light and emission is at visible wavelengths; thus, it does not require expensive UV windows and does not suffer from interference from background fluorescence. In this work the upconversion phosphors have been characterized in terms of their intensity, lifetimes and spectral content over a temperature range of 300K to 1500K. The technique has been evaluated for applications of 2D surface temperature measurements by using the total integrated intensity and the ratio of emission in different visible color bands. The results indicate that upconversion phosphor thermometry is a promising technique for making non-contact high-surface temperature measurements with good accuracy. [Preview Abstract] |
Tuesday, November 22, 2011 8:13AM - 8:26AM |
M14.00002: Multi-Wavelength Optical Pyrometry Investigation for Turbine Engine Applications. Jordi Estevadeordal, Nirm Nirmalan, Guanghua Wang An investigation of optical Pyrometry using multiple wavelengths and its application to turbine engine is presented. Current turbine engine Pyrometers are typically broadband Si-detector line-of-sight (LOS) systems. They identify hot spots and spall areas in blades and bucket passages by detection of bursts of higher voltage signals. However, the single color signal can be misleading for estimating temperature and emissivity variations in these bursts. Results of the radiant temperature, multi-color temperature and apparent emissivity are presented for turbine engine applications. For example, the results indicate that spall regions can be characterized using multi-wavelength techniques by showing that the temperature typically drops and the emissivity increases and that differentiates from the emissivity of the normal regions. Burst signals are analyzed with multicolor algorithms and changes in the LOS hot-gas-path properties and in the suction side, trailing edge, pressure side, fillet and platform surfaces characterized. [Preview Abstract] |
Tuesday, November 22, 2011 8:26AM - 8:39AM |
M14.00003: Development of Dual Luminescence Imaging for Capturing the Temperature Distribution of Supercooled-Water Droplets Akihito Aoki, Shigeo Kimura, Katsuaki Morita, Hirotaka Sakaue Dual luminescent imaging technique is developed to capture the temperature field of supercooled-water droplets. This technique can be applied to obtain the temperature information for the icing in flights, power cables, architectures, and etc. It consists of two luminophores in water solution; one is sensitive to the temperature and the other is insensitive to the temperature. The former is used as a signal luminescence, and the other as a reference luminescence. Both are spectrally separated, which are captured by a hi-speed color camera. The temperature calibration in water below freezing point is shown. As a demonstration, the temperature field of a supercooled droplet on a plate with a different temperature is shown. [Preview Abstract] |
Tuesday, November 22, 2011 8:39AM - 8:52AM |
M14.00004: Development and Testing of Temperature Sensitive Particles Trenton West, Cun Zhu, Younan Xia, Gamal Khalil, Dana Dabiri Temperature sensitive particles can be used to seed a fluid flow, allowing for non-intrusive velocity and temperature field measurements. Using an avalanche photodiode (APD) with fiber optic setup, the emission intensity of luminescing samples is measured. Changes in the luminescence when subjected to a step temperature input within a shock tube lead to the determination of the time response. Furthermore, temperature and pressure sensitivity analysis is performed using a photomultiplier tube (PMT) survey apparatus. Results for various temperature sensitive particles are presented along with suggestions for application to experimental flows. [Preview Abstract] |
Tuesday, November 22, 2011 8:52AM - 9:05AM |
M14.00005: Uncertainty analysis of particle image thermometry using individual thermo-liquid crystal tracers Rodrigo Segura, Christian Cierpka, Massimiliano Rossi, Christian K\"ahler An analysis of the benefits and challenges in calibrating temperature measurements by tracking the color fluctuations of individual thermo-liquid crystals is presented. Flow thermometry using liquid crystals has long been investigated for the evaluation of temperature fields but a reliable experimental uncertainty analysis is yet to be made for individual particles. A study was performed on the temperature response of individual tracer particles. The fluctuations in color response of adjacent crystals in a constant temperature environment were evaluated as well as the aging effects due to continuous illumination. The hysteresis of the color response to temperature gradients was also evaluated, as well as overheating and overcooling effects on individual particles. Flow thermometry has been widely used in the past to evaluate average temperature fields but a more precise characterization is possible by tracking the temperature of the individual tracers. [Preview Abstract] |
Tuesday, November 22, 2011 9:05AM - 9:18AM |
M14.00006: Instantaneous Temperature Measurements using Constant-Voltage Anemometry Genevieve Comte-Bellot, Arganthael Berson, Philippe Blanc-Benon, Emmanuel Jondeau Up to now, cold wires have been operated by constant-current anemometers, with a classic thermal inertia correction based on the mean value of the cold wire time constant [Lemay, Bena\"{\i}ssa {\&} Antonia, Exp. Thermal {\&} Fluid Sci, 2003, 27,133-143] or with a new correction method making use of the instantaneous value of the cold wire thermal lag [Berson, Poignand, Blanc-Benon {\&} Comte-Bellot, Rev. Sci. Instrum. 2010, 81, 015102]. The latter correction method is applied to the constant-voltage anemometer and temperature measurements are presented for the first time with such a device. Two constant-voltage anemometers are used for the instantaneous measurement of temperature fluctuations in unsteady flows. The first one is a new prototype elaborated by Tao Systems Inc. and adapted to fine wires with a resistance between 30 and 100 ohms. It operates a cold wire whose resistance varies with the temperature of the surrounding fluid. The second anemometer is a commercial system by the same company. It operates a hot wire, from which the instantaneous effect of the thermal inertia of the cold wire is determined. Results are presented for two flows: (i) a heated turbulent jet and (ii) an acoustic standing wave inside a resonator where flow reversal occurs. [Preview Abstract] |
Tuesday, November 22, 2011 9:18AM - 9:31AM |
M14.00007: Toluene laser-induced fluorescence imaging of compressible flows in an expansion tube V.A. Miller, M. Gamba, M.G. Mungal, R.K. Hanson, K. Mohri, C. Schulz Laser-induced fluorescence (LIF) imaging using toluene as a tracer molecule has been developed for high-speed, low-to-moderate enthalpy conditions in the Stanford 6-inch Expansion Tube. The approach is demonstrated on three canonical compressible flow configurations: (i) supersonic flow over a 20\r{ } wedge, (ii) around a cylinder, and (iii) a supersonic boundary layer. Under constant-pressure conditions, toluene LIF offers unique sensitivity to temperature and can therefore be used as an accurate thermometry diagnostic for supersonic flows; on the other hand, for variable-pressure flow fields (e.g., flow around a blunt body), toluene LIF imaging is demonstrated to be an effective flow visualization tool. The three configurations selected demonstrate the diagnostic in these two capacities. For all configurations considered in the study, toluene (0.6{\%} by volume) is seeded into a nitrogen freestream at a Mach number $\sim $ 2.2, T $\sim $ 500K, and p $\sim $ 1.5 bar. A frequency-quadrupled pulsed Nd:YAG laser is used to excite the tracer, and the resulting fluorescence is captured by an ICCD camera. Synthetic fluorescence signals from CFD solutions of each case have been computed and compare favorably to measured signals. [Preview Abstract] |
Tuesday, November 22, 2011 9:31AM - 9:44AM |
M14.00008: PIVT Investigation on Film Cooling in Turbine Blade Rebecca Malish, Jordi Estevadeordal, Ron Bunker An investigation using particle image velocimetry and thermography (PIVT) on the film cooling location of turbine blades in a cascade is presented. The laser scattering from seeding particles is captured with double exposure PIV camera, and fluorescence emissions are captured with ICCD camera for ratio thermometry.~ The technique allows capturing the velocity and temperature distributions of the particles at varying blowing ratios. The seeding particles were immersed in two locations of the cascade, the first was upstream of the blade; the second was inside the blade to allow for mixing with the coolant. The combined velocity and temperature maps allow understanding the film holes cooling effectiveness and clearly identify areas and holes that are more effective at cooling. PIVT gives a two-dimensional measurement than other techniques cannot provide and it is able to map the velocity and temperature in various viewing flow areas with the seeding particles. [Preview Abstract] |
Tuesday, November 22, 2011 9:44AM - 9:57AM |
M14.00009: Glowing Droplets in Turbulence Humberto Bocanegra Evans, Thanja Lamberts, Nico Dam, Willem van de Water Preferential concentration is a process in which turbulence unmixes a dispersion of droplets. It is most prominent at the smallest length and time scales. We select droplets by phosphorescence tagging in a zero mean flow turbulence experiment. The droplets are made out of a Europium-based solution, which has a phosphorescent lifetime of approximately 1 ms. A cylinder-shaped cloud is tagged in a weakly focused laser beam. The evolution of the cloud in the turbulent flow is recorded using an intensified high-speed camera. Through this method both, the advection of the tagged region and the evolution of the droplet concentration, can be monitored. The phosphorescent cloud is subjected to a turbulent flow by means of eight synthetic jets placed on the truncated corners of a cubic chamber. The turbulent flow is highly isotropic and has Re$_\lambda$=444, with Kolmogorov length-- and timescale $\eta$=79 $\mu$m and $\tau_k$=406 $\mu$s, respectively. We will present a proof of principle of this novel technique. [Preview Abstract] |
Tuesday, November 22, 2011 9:57AM - 10:10AM |
M14.00010: Selection and Testing of Pressure and Temperature Sensitive Dyes for 2-D Flow Characterization via Synthesized Microbeads Alex Perez, Cun Zhu, Younan Xia, Gamal Khalil, Dana Dabiri Airborne temperature and pressure sensitive microbeads provide a vehicle with which to conduct two-dimensional flow characterization. An array of temperature and pressure sensitive dyes have been synthesized with microbeads (of silica, polystyrene, and polydimethylsiloxane) for this purpose. These microbeads were evaluated based on emission spectra, pressure response (0-760 torr), temperature response (5-45\r{ }C), and response time. Work will be presented showing the various combinations of dyes and microbead materials, as well as the testing process and examples of future application. [Preview Abstract] |
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