Vibrational Temperature Measurements in a Shock Layer Using Laser Induced Predissociation Fluorescence

Sutton, D. J.; Houwing, A. F. P.; Palma, P. C.; Sandeman, R. J.

doi:10.1007/978-3-642-78832-1_4

Cited by 2 publications

(3 citation statements)

References 12 publications

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“…One of the first applications of fluorescence thermometry to a free-piston shock tunnel flow (93) used the laser-induced pre-dissociation fluorescence (LIPF) to avoid the effects of collisional quenching and to measure vibrational temperature in a bow shock layer. Pre-dissociation fluorescence does not have a strong quenching dependence because the pre-dissociation rate of the laserpopulated level is much faster than the collisional quenching rate.…”

Section: Thermometrymentioning

confidence: 99%

Optical imaging techniques for hypersonic impulse facilities

2007

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The application of optical imaging techniques to hypersonic facilities is discussed and examples of experimental measurements are provided. Traditional Schlieren and shadowgraph techniques still remain as inexpensive and easy to use flow visualisation techniques. With the advent of faster cameras, these methods are becoming increasingly important for time-resolved high-speed imaging. Interferometry’s quantitative nature is regularly used to obtain density information about hypersonic flows. Recent developments have seen an extension of the types of flows that can be imaged and the measurement of other flow parameters such as ionisation level. Planar laser induced fluorescence has been used to visualise complex flows and to measure such quantities as temperature and velocity. Future directions for optical imaging are discussed.

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Section: Thermometrymentioning

confidence: 99%

Optical imaging techniques for hypersonic impulse facilities

2007

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“…Laser-induced fluorescence 8 compared to single-point fluorescence measurements (LIF), lies in the ability to visualize relative species distributions over an entire planar cross section of the flow field, making it thus also a more complex technique. PLIF has been used for hypersonic flow visualisation (Fox et al, 2001a,b;Gaston et al, 2002), visualisation of a scramjet combustor (McIntyre et al, 1997), thermometry (Palma et al, 2003(Palma et al, , 1998Sutton et al, 1993) and velocimetry (Danehy et al, 2001.…”

Section: Laser-induced Fluorescencementioning

confidence: 99%

“…It has been demonstrated by several researches (Palma et al, 2003(Palma et al, , 1998Sutton et al, 1993) that laserinduced fluorescence can be used for thermometry in free-piston shock tunnels. However, due to the strong time-dependent nature of such experimental flows and of turbulent combustion generated in scramjet engines, the methods that are able to yield temperatures in a single facility/laser run, avoiding thus errors based on shot-to-shot flow fluctuations, are especially appealing thermometry techniques.…”

Section: Lif Thermometrymentioning

confidence: 99%

Temperature measurements in hypervelocity flows using thermally-assisted laser-induced fluorescence

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Scramjet engines with their very high specific impulse have the potential to outperform rocket motors as a means of propelling hypersonic vehicles. The scope of this project is to determine temperatures in the scramjet combustor using an advanced optical diagnostic technique, namely laser-induced fluorescence. Presently, direct temperature measurements are not readily available for scramjets, due to three reasons. Firstly, commonly-used gauges for temperature measurements, such as thermocouples and heat transfer gauges would not survive or would be damaged at the extreme temperatures typically occurring in scramjets (around T = 1100 -2500 K), and therefore these gauges would not give accurate readings. Secondly, measurements with any gauges would be intrusive, and their presence in the flow might cause large disturbances. Thirdly, these gauges can only provide discrete, point measurements. Laser-induced fluorescence measurements present an optical non-intrusive technique to resolve temperatures in the combustor. Additionally, LIF measurements allow the temperatures in the combustor to be resolved at a higher spatial resolution than regular gauges. The new contribution made by this PhD project is the application of a sophisticated optical diagnostic technique, thermally-assisted laserinduced fluorescence, to the temperature measurements in the combustor of a supersonic combustion engine. The issues with the technique and the way it should be used for application to scramjet flows were explored. This required the development of the new knowledge and understanding of the spectroscopy that underpins the technique. The project is significant because, to the author's knowledge, this is the first time thermally-assisted LIF has been used for scramjet flows in a test facility. Currently available thermometry methods usually require averaged repeated experiments, thus causing high cost of experiments. This study represents successful single-shot scramjet temperature measurements. The project was approached theoretically (synthetic spectra), experimentally and numerically (CFD and LIF modelling).Radiation simulation programs providing synthetic OH spectra represent the theoretical part of this study, as they employ theoretical expressions for spectral calculations. The OH radical is an intermediate species in the combustion, created in high quantities, therefore allowing direct fluorescence measurements. In this work, three numerical codes were used -LIFBASE, SPARTAN and Photaura. SPARTAN and Photaura were modified in order to include the OH molecule. The results presented here show that OH spectra produced using these programs show very good agreement. All three programs give correct and reliable representation of the physical phenomena in the wavelength range studied.Experimental data was obtained through laser-induced fluorescence with a laser beam focused into the combustor exciting an OH molecule transition. The experiments were conducted in the T4 shock tunnel using a scramjet model. LIF measurements were performed t...

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Vibrational Temperature Measurements in a Shock Layer Using Laser Induced Predissociation Fluorescence

Cited by 2 publications

References 12 publications

Optical imaging techniques for hypersonic impulse facilities

Optical imaging techniques for hypersonic impulse facilities

Temperature measurements in hypervelocity flows using thermally-assisted laser-induced fluorescence

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