Temperature variations in a free piston compression wind tunnel

Widodo, Agung Sugeng (2012) Temperature variations in a free piston compression wind tunnel. [Thesis (PhD/Research)]

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This dissertation presents an investigation of the free stream stagnation temperature variations in the University of Southern Queensland (USQ) hypersonic wind tunnel (designated TUSQ), a short duration wind tunnel operated as a Ludwieg Tube with free piston compression heating. Because the facility is relatively new and because strong disturbances have previously been observed in similar facilities, a study to investigate the thermal characteristics of the hypersonic flow generated by TUSQ was needed.
This study investigates the temporal and spatial thermal characteristics of the hypersonic flow produced in the TUSQ facility and relates these characteristics to the compression and flow discharge processes within the barrel. Quantification of the flow conditions produced in wind tunnels is important. Without such information, it is di�cult to relate wind tunnel results to flight conditions or to perform meaningful computational simulations on the tested configuration. Three different versions of an aspirating thermocouple probe were developed for this work and a thin film heat flux gauge was also tested. Results with the Mach 6 nozzle show that the flow stagnation temperature decreases with time and thermodynamic simulations accurately reflect the majority of the observed
temporal variations when flat plate boundary layer cooling is used to model the heat transfer in the barrel of the facility. Because the flat plate boundary layer
cooling model provides a good match to the measured temperature on the nozzle centre line for the majority of the flow duration, it is concluded that signi�cant mixing must have occurred across the diameter of barrel prior to
ow discharge through the nozzle. Measurements in other facilities have indicated the existence of discrete, large scale thermal disturbance which propagated ahead of the piston and potentially compromised the test flow quality, but no such disturbance were detected at the centre line of the nozzle exit in the present work. The stagnation temperature measurements indicated a core flow region with a
radius of almost 80mm near the start of the test flow. The maximum average spatial gradient of stagnation temperature was registered at about 150 ms after the start of the test
flow and had a value of approximately -0:45K/mm within
the core flow region, indicating an average drop in stagnation temperature of about 20K over the core flow region at this time. Complementary pitot pressure
measurements indicate core flow uniformity to within 2% and a core flow radius of at least 80mm for the majority of the test flow duration of around 200ms.
Mach number profiles deduced from the pitot pressure measurements are likewise uniform with a Mach number of 5.81 � 0.05 for the majority of the test flow duration.
A fully-developed turbulent pipe flow model was developed and stagnation temperature fluctuations in the TUSQ facility were estimated to be around 20 K. Although this value is large compared to results from previous experiments in a gun tunnel facility, the value obtained is consistent with the magnitude of the spatial variation in stagnation temperature within the core region of the nozzle
exit flow at about 150 ms from the start of the flow. Relatively low frequency fluctuations in the stagnation point heat flux were observed and these appeared to correlate with the stagnation pressure fluctuations, but further effort in this area is required in order to resolve stagnation temperature fluctuations due to the turbulent mixing in the barrel.

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Item Type: Thesis (PhD/Research)
Item Status: Live Archive
Additional Information: Doctor of Philosophy (PhD) thesis.
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering
Supervisors: Buttsworth, David; Apan, Armando
Date Deposited: 02 May 2013 04:19
Last Modified: 22 Aug 2016 01:47
Uncontrolled Keywords: temperature fluctuations; hypersonic flow, stagnation temperature; free piston compression
Fields of Research : 09 Engineering > 0913 Mechanical Engineering > 091305 Energy Generation, Conversion and Storage Engineering
09 Engineering > 0913 Mechanical Engineering > 091399 Mechanical Engineering not elsewhere classified
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering
URI: http://eprints.usq.edu.au/id/eprint/23430

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