Search results

(1 - 2 of 2)
Mixer-ejector Wall Pressure and Temperature Measurements Based on Photoluminescence
Title
Mixer-ejector Wall Pressure and Temperature Measurements Based on Photoluminescence
Creator
Taghavi, R.r., Raman, G., Bencic, Tj
Date
2002-04
Publisher
American Inst Aeronaut Astronaut
Description
Ejector side-wall pressure distribution is a key indicator of supersonic jet-mixer-ejector performance. When documenting pressure patterns on...
Show moreEjector side-wall pressure distribution is a key indicator of supersonic jet-mixer-ejector performance. When documenting pressure patterns on an ejector wall using pressure-sensitive paint (PSP), one has to consider temperature variations caused by the supersonic jet flow within the ejector because these can cause significant local errors in the PSP results. If the temperature sensitivity of PSP is not corrected for in complex internal supersonic flows, large localized errors could contaminate the results. In the present work, temperature-sensitive paint maps the temperature distribution on the ejector wall and corrects PSP results point-by-point for temperature sensitivity. The experiments were conducted on multijet supersonic mixer-ejector configurations with straight, convergent (6-deg), and divergent (6-deg) side walls. A comparison of corrected and uncorrected PSP readings shows that at M-j = 1.55, the error with respect to true data from static pressure ports can be reduced from 4.98 to 2.84% for the case of a simple ejector with parallel walls. For the complex 6-deg convergent ejector at M-j = 1.39, the error reduces by almost an order of magnitude (from 20.83 to 2.66%). Our results indicate that the use of this correction technique can significantly reduce PSP errors in complex internal supersonic flow situations.
Show less
Jet-cavity Interaction Tones
Title
Jet-cavity Interaction Tones
Creator
Raman, G., Bencic, Tj, Envia, E.
Date
2002-08
Publisher
American Inst Aeronaut Astronaut
Description
A fundamental study of resonant tones produced by jet-cavity interaction over a wide range of flow conditions covering both subsonic and...
Show moreA fundamental study of resonant tones produced by jet-cavity interaction over a wide range of flow conditions covering both subsonic and supersonic speeds is described. Two significant findings emerge. For the jet-cavity configurations investigated, a suitably defined reduced frequency parameter allows for a global classification of all jet-cavity tones into two main types. For the first type, the reduced frequency depends on the jet Mach number, whereas for the second type, the reduced frequency is independent of the jet Mach number. We propose simple correlations for the frequency of both types of tones. Based on earlier research, we had expected that the traditional classifications of cavity flows into the open, transitional, or closed variety would be insensitive to small changes in Mach number and would depend primarily on the cavity's LID ratio. However, use of the novel high-resolution photoluminescent pressure sensitive paint shows that these classifications are actually quite sensitive to the jet Mach number for jet-cavity interactions. However, these classifications provide no guidance for determining tone type, amplitude, or frequency.
Show less