Simultaneous measurement of monocomponent droplet temperature/refractive index, size and evaporation rate with phase rainbow refractometry

We propose and experimentally demonstrate a hybrid grating, in which an excessively tilted fiber grating (Ex-TFG) and a fiber Bragg grating (FBG) were co-inscribed in a reduced-diameter fiber (RDF). The hybrid grating showed strong resonances due to coupling among core mode and a set of polarization-dependent cladding modes. This coupling showed enhanced evanescent fields by the reduced cladding size, thus allowing stronger interaction with the surrounding medium. Moreover, the FBG’s Bragg resonance confined by the thick cladding was exempt from the change of the surrounding medium’s refractive index (RI), and then the FBG can work as a temperature compensator. As a result, the Ex-TFG in RDF promised a highly sensitive RI measurement, with a sensitivity up to ~1224 nm/RIU near the RI of 1.38. Through simultaneous measurement of temperature and RI, the temperature dependence of water’s RI is then determined. Therefore, the proposed hybrid grating with a spectrum of multi-peaks embedded with a sharp Bragg resonance is a promising alternative for the simultaneous measurement of multi-parameters for many RI-based sensing applications.

Download Full-text

Influence of Refractive Index Gradients within droplets on rainbow position and implications for rainbow refractometry

Particle & Particle Systems Characterization ◽

10.1002/ppsc.19960130210 ◽

1996 ◽

Vol 13 (2) ◽

pp. 125-129 ◽

Cited By ~ 19

Author(s):

Klaus Anders ◽

Norbert Roth ◽

Arnold Frohn

Keyword(s):

Refractive Index ◽

Rainbow Refractometry

Download Full-text

Simultaneous Measurements of Droplet Size, Temperature, and Velocity Using an Integrated Phase-Doppler/Rainbow Thermometer

10.1115/imece2001/htd-24257 ◽

2001 ◽

Author(s):

Matt O’ Donnell ◽

Sumanta Acharya

Keyword(s):

Refractive Index ◽

Detailed Examination ◽

Temperature Profiles ◽

Droplet Temperature ◽

Radial Temperature ◽

Temperature Correlation ◽

Simultaneous Measurements ◽

Laser Diagnostic ◽

The Mean ◽

And Performance

Abstract This work summarizes efforts to determine the accuracy and performance characteristics of a new and novel laser diagnostic to measure instantaneous, in flight, droplet temperatures. The instrument uses the location of the rainbow peak to deduce the refractive index of the droplet, which in turn is related to the droplet temperature. Preliminary experiments were undertaken in order to understand the fundamental operating principles and limitations of the instrument. These experiments measured the temperature of an isothermal, single stream of monodisperse droplets. These measurements indicate that the mean refractive index can be measured with a standard deviation as low as 0.0001m. Once the operation of the refractometer was proved under isothermal conditions, the measurement of droplet temperatures in a swirl-stabilized combustor was performed. These measurements indicate that the strength of the rainbow signal is significantly hampered by the noise induced by the flame. Preliminary temperature measurements with the combustor equipped with 45° vanes showed relatively constant radial temperature profiles (∼55–60°C) at locations less than 2 inches from the nozzle exit. A detailed examination of the temperature correlation with velocity and diameter revealed that larger and faster moving droplets dominate the distributions. Thus, the smaller droplets that are suspected of having the highest temperatures are inadequately represented in the mean droplet temperature.

Download Full-text

Change of evaporation rate of single monocomponent droplet with temperature using time-resolved phase rainbow refractometry

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2018.09.026 ◽

2019 ◽

Vol 37 (3) ◽

pp. 3211-3218 ◽

Cited By ~ 2

Author(s):

Yingchun Wu ◽

Haipeng Li ◽

Xuecheng Wu ◽

Gérard Gréhan ◽

Lutz Mädler ◽

...

Keyword(s):

Evaporation Rate ◽

Time Resolved ◽

Rainbow Refractometry

Download Full-text

Simultaneous measurement of refractive index and temperature based on bent core-offset in-line fiber Mach-Zehnder interferometer

10.1117/12.2601197 ◽

2021 ◽

Author(s):

Bingcheng Wu ◽

Haiyang Bao ◽

Yanfei Zhou ◽

Yuan Liu ◽

Jie Zheng

Keyword(s):

Refractive Index ◽

Simultaneous Measurement ◽

Zehnder Interferometer ◽

Mach Zehnder Interferometer

Download Full-text

Simulation of Evaporating Spray and Comparison With Droplet Temperature Measurement Obtained by Rainbow Refractometer

10.1115/imece2000-2051 ◽

2000 ◽

Author(s):

Tevfik Gemci ◽

James Hom ◽

Norman Chigier

Keyword(s):

Droplet Size ◽

Three Dimensional ◽

Fluid Flows ◽

Computational Results ◽

Droplet Temperature ◽

Temperature Distributions ◽

Phase Doppler Interferometry ◽

Computational Work ◽

Evaporating Spray ◽

Rainbow Refractometry

Abstract Both experimental and computational work are important in the study of spray evaporation and combustion; therefore, it is essential that a link between the two areas be established. In this study, measurements of a full cone spray using phase-Doppler interferometry and Rainbow Refractometry are presented and compared with computational results. The computation results were acquired using a KIVA-3V code, which is specifically designed to analyze transient, two- and three-dimensional, chemically reactive fluid flows with sprays. Specifically, in this study, the droplet size, velocity and temperature distributions were measured at various locations within the full cone spray. Using the same initial and boundary conditions, computation results were obtained at corresponding locations and compared with the experimental results. The experimental and computational results agree very well and indicate similar droplet size, velocity and temperature distributions at the corresponding locations. Additionally, the cooling rates and movement of the droplets show the same trends.

Download Full-text