A joint computational and experimental study to evaluate Inconel-sheathed thermocouple performance in flames.

Brundage, Aaron Leon.; Nicolette, V.F.; Donaldson, A.B.; Kearney, Sean P.; Gill, Walter

doi:10.2172/923075

Cited by 9 publications

(18 citation statements)

References 4 publications

(3 reference statements)

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“…In this manner, the flow field, the local convection coefficient to the thermocouple, an estimate of the soot volume fraction, the path length for radiation, all can be taken into account so that the thermocouple reading can be interpreted. A presentation of such an effort is discussed extensively in [4]. Although there is still some unresolved uncertainty, this study found that such a fire code can account for more than 90% of the 800 °C discrepancy noted above.…”

Section: Introductionmentioning

confidence: 77%

“…For both the sheathed 10 mil thermocouple and the bare thermocouple used in the present experiments, the time constant was found from the Omega Temperature Handbook [8] to be on order of 0.5 seconds in a particular flowing hot air stream. While there will be some physical differences between combustion gases and air, from [4], the time constant for a 62 mil, sheathed thermocouple inserted into clean flame gases was 5 seconds; the corresponding value from [8] was 6 seconds.…”

Section: Thermocouple Modelmentioning

confidence: 99%

“…Such corrections have been addressed by various researchers in flame temperature measurements [2-3]. More specifically, in clean premixed laboratory burner scale flames, the indicated temperature measurement may be as much as 800 °C or more below the combustion gas temperature (calculated from adiabatic equilibrium and confirmed experimentally by CARS [4]). This is due to the thermocouple energy balance that includes input from combustion gas convection and surface heat loss to the surroundings outside the flame by radiation from the thermocouple; this factor becoming very large when the thermocouple surface reaches temperatures of 1,200-1,500 K. In clean laboratory flames, the participation by gas band emission or absorption from carbon dioxide and water vapor are negligible and soot is not present in abundance.…”

Section: Introductionmentioning

confidence: 99%

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Problems Encountered in Fluctuating Flame Temperature Measurements by Thermocouple

Yılmaz

Gill

Donaldson

et al. 2008

Sensors

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Some thermocouple experiments were carried out in order to obtain sensitivity of thermocouple readings to fluctuations in flames and to determine if the average thermocouple reading was representative of the local volume temperature for fluctuating flames. The thermocouples considered were an exposed junction thermocouple and a fully sheathed thermocouple with comparable time constants. Either the voltage signal or indicated temperature for each test was recorded at sampling rates between 300-4,096 Hz. The trace was then plotted with respect to time or sample number so that time variation in voltage or temperature could be visualized and the average indicated temperature could be determined. For experiments where high sampling rates were used, the signal was analyzed using Fast Fourier Transforms (FFT) to determine the frequencies present in the thermocouple signal. This provided a basic observable as to whether or not the probe was able to follow flame oscillations. To enhance oscillations, for some experiments, the flame was forced. An analysis based on thermocouple time constant, coupled with the transfer function for a sinusoidal input was tested against the experimental results.

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Section: Introductionmentioning

confidence: 77%

Section: Thermocouple Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Problems Encountered in Fluctuating Flame Temperature Measurements by Thermocouple

Yılmaz

Gill

Donaldson

et al. 2008

Sensors

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“…The equilibrium tube is 53 cm and it can safely be assumed that the particles investigated in this study are at flow conditions by the time they exit the equilibrium tube. [38] for oxidized Inconel was digitized and a fourth order polynomial was used to reconstruct the curve for this calculation. Inconel is a nickel alloy similar to that used for the test fixture and it is assumed that the two materials have the same emissivity.…”

Section: Figure 5: Dust Feed Boxmentioning

confidence: 99%

The Effect of Particle Size on Deposition in an Effusion Cooling Geometry

Wolff

Bowen

Bons

2018

2018 AIAA Aerospace Sciences Meeting

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The effect of particle size on particle accumulation within an effusion cooling geometry common to gas turbines was investigated experimentally and computationally.A flat plate with an effusion cooling hole array based on a gas turbine combustor liner was subjected to particulate laden flow in an accelerated deposition facility. The tests were conducted at an engine relevant plate temperature of 1118 K, coolant temperature of 950 K, and held at a constant pressure ratio of 1.03 (cavity to ambient). To elucidate the effect of particle size, six unique size distributions of Arizona Road Dust (ARD) smaller than 20 micron were introduced to the flow independently. Experiments were also conducted in which two different dust size distributions were sequentially delivered to the test article. These experiments clearly indicate that the smallest particles within the range tested accumulate within the hole creating deposit structures and blocking the effusion holes. They also indicate that larger particles within this range can have an erosive effect on the deposit structures as they build, changing the structure's morphology and blockage behavior.Computational fluid domains were developed to replicate the test article geometry before and after a test to investigate the effect that deposit structures have on deposition.Particles were introduced to these domains after reaching a steady solution and were tracked through the solution with a Lagrangian trajectory solver. The impact locations of iv the particles were recorded and a particle sticking model was employed to determine if the particles stick or rebound. The domain with the clean hole showed that the smallest particles impact and were prone to sticking in the area where deposits form experimentally. As the particles increase in size, the number of impacts and likelihood of sticking decreased. The domain with scoop deposit structures showed that these structures can change the particle impact trajectories influencing the buildup process.Overall, this body of work shows that particle size distribution has a first order effect on the blockage caused by particle deposition in effusion cooling geometries. The observation that 0.5-3 μm particles are primarily responsible for blockage while large particles can reduce deposit structure size highlights the complexity of particle deposition. This has significant implications for future work, particularly high fidelity modeling.v

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“…The benefits of these diagnostics are that the probes are robust, inexpensive and simple to implement. However, these probes are intrusive, which disturbs the environment being investigated, and suffer from bias errors resulting from thermal lag as well as radiative and conductive heat transfer with the surroundings [6]. The high resolution demanded by the models coupled with the above mentioned bias errors have resulted in the recent adaptation by the Sandia fire community toward laser or optically based diagnostics, which include imaging techniques such as planar laser-induced fluorescence for scalar imaging and particleimage velocimetry [4,7], emission spectroscopy [8], tunable-diode-laser absorption spectroscopy (TDLAS) for species, soot and temperature determinations [9] and in situ pyrometric probes [10].…”

Section: Introductionmentioning

confidence: 99%

Diagnostic development for determining the joint temperature/soot statistics in hydrocarbon-fueled pool fires : LDRD final report.

Casteneda¹,

Frederickson²,

Grasser³

et al. 2009

Self Cite

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A joint temperature/soot laser-based optical diagnostic was developed for the determination of the joint temperature/soot probability density function (PDF) for hydrocarbon-fueled meter-scale turbulent pool fires. This Laboratory Directed Research and Development (LDRD) effort was in support of the Advanced Simulation and Computing (ASC) program which seeks to produce computational models for the simulation of fire environments for risk assessment and analysis. The development of this laser-based optical diagnostic is motivated by the need for highly-resolved spatiotemporal information for which traditional diagnostic probes, such as thermocouples, are ill-suited. The in-flame gas temperature is determined from the shape of the nitrogen Coherent Anti-Stokes Raman Scattering (CARS) signature and the soot volume fraction is extracted from the intensity of the Laser-Induced Incandescence (LII) image of the CARS probed region. The current state of the diagnostic will be discussed including the uncertainty and physical limits of the measurements as well as the future applications of this probe.4

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A joint computational and experimental study to evaluate Inconel-sheathed thermocouple performance in flames.

Cited by 9 publications

References 4 publications

Problems Encountered in Fluctuating Flame Temperature Measurements by Thermocouple

Problems Encountered in Fluctuating Flame Temperature Measurements by Thermocouple

The Effect of Particle Size on Deposition in an Effusion Cooling Geometry

Diagnostic development for determining the joint temperature/soot statistics in hydrocarbon-fueled pool fires : LDRD final report.

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