Turbulent interactions with normal shocks and their effects on aluminum particle burn time

aluminum;shock tube;shock wave;burn time;nano;micron;turbulence;particle image velocimetry (PIV);energetics

Guo, Shuyue ; Glumac ; Nick

关键词: aluminum;    shock tube;    shock wave;    burn time;    nano;    micron;    turbulence;    particle image velocimetry (PIV);    energetics;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/72837/Shuyue_Guo.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Interactions between turbulence and shock waves have been proposed to decrease the burn time of fuel particles due to various mechanisms such as enhanced mixing, entropyproduction, and transport. In order to demonstrate this e ffect, burn time measurements were obtained for laminar and turbulent conditions at similar test conditions. The amountof turbulence present was also studied using PIV methods to verify that it represents a signi cant di fference between the two conditions.The experiments were conducted in the UIUC heterogeneous shock tube facility. The test conditions were 10atm and 2500K after the refl ected shock for both the turbulent andlaminar cases. Turbulence conditions were produced by placing a perforated plate directly upstream of the optical section installed at the end of the shock tube; the plate design has been previously documented in multiple papers to produce an area of isotropic and homogeneous turbulence. The test particles were 40-60nm Al, 110 nm Al, 4 um Al, and 7.5 um Al in order to allow for a representative range of Al particles typically used in energetics research. High speed cameras and a 532 nm green laser were used to obtain both the burntime data and PIV turbulence images. Burn time results showed a 10-25% reduction in burn times for the turbulent case compared to the laminar case. The amount of reduction seems to decrease by increasing particle size. Due to a lack of standard burn time evaluation procedure and thermal noise in the data, e fforts were necessary to address repeatability and error issues. Therefore, 3 tests were conducted at each condition for each particle size, and variation between the tests were accounted for in the error to show that despite the errorpresent, we can be reasonably con fident that there exists a notable burn time reduction.Finally, PIV was employed to study the quality and quantity of the turbulence present in the test conditions. The turbulent case PIV data indicated an average turbulence intensity of approximately 3%, which may be qualifi ed as medium turbulence. Laminar PIV data was less indicative due to poor seeding capabilities andflow disruption when the seeded particleswere swept othe loading plate in the shock tube. An estimated 1% turbulence intensity was still observed in the laminar case, although it is clear from the velocity profi les that thefl ow is significantly more uniform and data less precise and therefore less reliable.