Two-color, toluene based, planar laser induced fluorescence (PLIF) is utilized to characterize the thermal structure of a turbulent, free jet. The PLIF technique has been used to measure concentration gradients for combustion applications, but its use to quantify thermal gradients is limited. To validate the method, compressed air is seeded with toluene particles. The seeded airflow is heated to temperatures varying from 300 – 375 K, and the heated jet exits a 1.27-cm diameter orifice into quiescent, room temperature air. The jet Reynolds number is varied from 5,000 to 15,000. As the jet exits the orifice, the toluene particles fluorescence across a 266 nm laser light sheet which ultimately provides a two-dimensional temperature distribution of the free jet. The rigorous calibration procedure for the PLIF technique is described along with the seeding nuisances needed to quantify the thermal structure of the jets. The PLIF technique has been demonstrated for this fundamental flow field, and it has proven to be applicable to more complex heat transfer and cooling applications. Furthermore, the time averaged temperature distributions obtained in this investigation can be used in the validation of turbulent CFD solvers.
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Thermal Development of an Impinging Jet Using Planar Laser Induced Fluorescence (PLIF)
Planar Laser Induced Fluorescence (PLIF) has been demonstrated to investigate a round jet impinging on a flat surface. Detailed thermal field distributions have been obtained near the flat target surface to characterize the wall jet development ensuing from the stagnation point. While PLIF has been demonstrated for combustion applications to measure concentration gradients within a mixture, its application for temperature field measurements is less established. Therefore, the technique was applied to a simple, cylindrical impinging jet. The jet Reynolds number varied with Rejet = 5,000 – 15,000 while the jet – to – target surface spacing varied from H / D = 4 – 10. The cooling jet (Tjet ~ 300 K) impinged on a flat, heated surface. The PLIF technique was able to capture the free jet structure and jet development along the target surface. With a short impingement length (H / D = 4), the potential core of the jet strikes the target surface. The thermal gradients captured during the experiments demonstrate the fully turbulent nature of the impinging jet with H / D = 10. The thermal boundary development along the target surface is clearly captured using this fluorescence method. The near wall temperature gradients acquired with the PLIF method have been used to calculate heat transfer coefficients on the heated surface, and these values compare favorably to those measured using a well-established steady state, heat transfer method. The PLIF technique has been demonstrated for this fundamental impingement setup, and it has proven to be applicable to more complex heat transfer and cooling applications.
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- Award ID(s):
- 1126371
- NSF-PAR ID:
- 10089700
- Date Published:
- Journal Name:
- ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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