Pressure-sensitive paint diagnostic to measure species concentration on transpiration-cooled walls

The design of a transpiration cooled system requires detailed local heat transfer information on and in the vicinity of the porous injector; however, limited spatially resolved experimental studies exist, particularly in hypersonic flows. In this work experiments were conducted in the Oxford High Density Tunnel at Mach 6.1 in both laminar and turbulent regimes. Spatially resolved 2D surface heat transfer measurements were acquired by imaging directly on and downstream of two micro-porous transpiration cooled injectors (METAPOR CE170 and Zirconia) using high-speed infra-thermography. Whilst injection in the laminar regime results in a steady, monotonic reduction in heat transfer from the start of the injector, a flatter profile is present for the turbulent cases where turbulent mixing inhibits surface heat transfer reduction.

show abstract

“…Experimental testing was conducted on a flat plate model used in previous studies [18][19][20][21] at 0 • angle of attack.…”

Section: A Experimental Modelmentioning

confidence: 99%

Transpiration-Cooling Heat Transfer Experiments in Laminar and Turbulent Hypersonic Flows

Naved¹,

Hermann²,

Hambidge³

et al. 2023

Journal of Thermophysics and Heat Transfer

Self Cite

View full text Add to dashboard Cite

show abstract

“…8. As the channels are small and the mass flux high, there still exists a pressure gradient during injection [12]. The numerically derived correlation, which is represented by the black line in Fig.…”

Section: Resultsmentioning

confidence: 98%

“…Then, a pressure sensitive paint solution consisting of 0.1 mmol Ru dpp 3 2+ luminophores suspended in 200 ml Dichloromethane, was applied with an air brush. More details on the PSP and the application method can be found in [12]. The rest of the hemisphere was also spray painted with PSP, after being primed with an ISSI fast response porous underlayer.…”

Section: Methodsmentioning

confidence: 99%

“…Alumina particles with a diameter of 6.45 𝜇m were sintered for 3 hours at 1700 • C. More details and images of the surface microstructure can be found in [12], where the same material is used. The geometry consisted of a 2 mm thick, 14 mm diameter disk on top of a 3 mm thick, 20 mm diameter disk.…”

Section: Methodsmentioning

confidence: 99%

“…This is due to the temperature limitations imposed by the experimental facilities and diagnostics. The concentration of molecular oxygen at the wall is measured directly using a novel pressure sensitive paint diagnostic [12] on a flat faced hemispherical probe in the Oxford High Density Tunnel. A range of freestream conditions, coolant gases and blowing ratios are explored and compared to the analytical solution described in the next section.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Measuring the Concentration of Freestream Species on a Hypersonic Transpiration-Cooled Stagnation Point

Rocher¹,

Hermann²,

McGilvray³

et al. 2022

Journal of Spacecraft and Rockets

Self Cite

View full text Add to dashboard Cite

This paper presents direct surface concentration measurements of a transpiration cooled stagnation point in hypersonic flow. Pressure sensitive paint (PSP) is employed on a porous alumina sample to measure the concentration of freestream species and thus how well the coolant mitigates mass diffusion from the freestream to the surface. Experiments are conducted at Mach 6.9 at three different Pitot pressures: 10 kPa, 20 kPa and 30 kPa. Porous alumina is chosen due to its ability to bond PSP and its similar microstructure to porous Ultra-High-Temperature Ceramics. Nitrogen, Argon and Krypton are used as injection gases at mass flow rates ranging

show abstract

Laminar transpiration cooling experiments in hypersonic flow

et al. 2022

Self Cite

View full text Add to dashboard Cite

The mixing between the coolant and the boundary-layer gas downstream of an injector—for transpiration/film cooling—has been extensively studied for turbulent flows; however, only a handful of studies concerning laminar mixing exist, particularly in hypersonic flows. In this paper, the concentration of the coolant gas at the wall and the heat flux reduction downstream of a transpiring injector in a hypersonic laminar flow are experimentally measured and examined. Experiments are performed in the Oxford High Density Tunnel at Mach 7. A flat-plate model is coated with pressure-sensitive paint (PSP) to spatially resolve the film and obtain a film effectiveness based on coolant concentration. Thin-film arrays are installed to measure the heat flux reduction. Six different cases are studied featuring nitrogen and helium as the coolant gas, where the blowing ratio is varied from 0.0406% to $$0.295\%$$ 0.295 % . The unit Reynolds number of the flow is $$12.9\times 10^6\;\mathrm {m^{-1}}$$ 12.9 × 10 6 m - 1 . A coolant concentration of up to $$95\%$$ 95 % is achieved immediately (2 mm) downstream of the injector. The film concentration drops in a monotonic fashion farther downstream; however, a constant film coverage of 5–20 mm immediately downstream of the injector is observed in cases with a higher blowing ratio. A film coverage above 15% over three injector lengths is present even for the lowest blowing ratio. Heat flux reduction is achieved in all cases. The concentration effectiveness obtained from PSP is compared with the thermal film effectiveness calculated from the heat flux reduction. The latter is found to be higher than the former for all data points. Finally, a collapse of the thermal effectiveness is achieved and a modified analytical correlation is proposed. Graphical abstract

show abstract

Pressure-sensitive paint diagnostic to measure species concentration on transpiration-cooled walls

Cited by 7 publications

References 12 publications

Transpiration-Cooling Heat Transfer Experiments in Laminar and Turbulent Hypersonic Flows

Transpiration-Cooling Heat Transfer Experiments in Laminar and Turbulent Hypersonic Flows

Measuring the Concentration of Freestream Species on a Hypersonic Transpiration-Cooled Stagnation Point

Laminar transpiration cooling experiments in hypersonic flow

Contact Info

Product

Resources

About