Shock tube

About: Shock tube is a research topic. Over the lifetime, 6963 publications have been published within this topic receiving 99372 citations.

Shock Tube Study of the Influence of NOx on the Ignition Delay Times of Natural Gas at High Pressure

Abstract: The ignition delay times of diluted reference gas/O2/NO2/Ar mixtures (Φ = 0.25, 0.5, and 1.0, dilution 1:2 and 1:5, [NO2] = 20–250 ppm) were determined in a high-pressure shock tube. The temperature range was 1000 K ≤ T ≤ 1700 K at pressures of about 16 bar. The addition of NO2 leads to a significant reduction of the ignition delay times. This reduction increases with decreasing equivalence ratio. The effect of NO2 is well predicted by the NOx chemistry of different published reaction mechanisms. The differences in the predictions of the ignition delay times using a common hydrocarbon reaction mechanism and NOx subsystems of four published reaction mechanisms are negligible. Supplemental materials are available for this article. Go to the publisher's online edition of Combustion Science and Technology to view the free supplemental file.

Equation of state of beryllium at shock pressures of 0.4–1.1 TPa (4–11 Mbar)

Abstract: High-pressure shock Hugoniot data were measured for Be using strong shock waves generated by underground nuclear explosions. These data and a preliminary theoretical analysis are reported.

Characteristics of an annular vertical diaphragmless shock tube

Abstract: . This paper reports on the characteristics of a compact vertical diaphragmless shock tube, which was constructed and tested in the Shock Wave Research Center to study experimentally the behavior of toroidal shock waves. It is 1.15 m in height and has a self-sustained co-axial vertical structure consisting of a 100 mm i.d. outer tube and an 80 mm o.d. inner tube. To create a ring shaped shock wave between the inner and outer tubes, a rubber sheet is inserted to separate a high pressure driver gas from a test gas, which is bulged with auxiliary high pressure helium from the behind. When the rubber membrane is contracted by the sudden release of the auxiliary gas so as to break the seal, shock waves are formed. Special design features of the shock tube are described and their role in producing repeatable shock waves is discussed. Its special opening characteristics make possible the production of annular shaped shock waves that are unlikely met with a conventional tube that uses rupturing diaphragms. Performance of the shock tube is evaluated in terms of the shock wave Mach numbers and the measured flow properties. It eventually showed a higher degree of repeatability and the scatter in the shock wave Mach numbers Ms was found to be 0.2% for Ms ranging from 1.1 to 1.8. The shock wave Mach number so far measured agreed very well with the simple shock tube theory.

Hypersonic Boundary-Layer Transition Experiments in the Boeing/AFOSR Mach-6 Quiet Tunnel

Abstract: This paper reports progress from six different projects studying hypersonic boundarylayer transition. Efforts to measure instabilities in the wake of an isolated roughness element in the laminar nozzle-wall boundary layer of the BAM6QT are on-going. A new set of instabilities have been measured when the roughness is at a height that causes incipient transition within the measurement range. The second project tested a method of calibrating temperature-sensitive paints using Schmidt-Boelter heat transfer gauges. A 7-deg half-angle cone was tested at 0-deg angle of attack and the heat transfer compared well with theory. A forward-facing cavity was used to identify the critical depth where self-sustaining oscillations begin. This was found to be about 1.2 cavity diameters. A shock tube is being constructed at Purdue to calibrate PCB-132 sensors. The tube will create clean, weak shocks of a magnitude similar to a second-mode wave in a wind tunnel, allowing accurate calibrations for instability measurements. A flared cone was tested in the BAM6QT, and showed natural transition under fully quiet flow. The streamwise vortices visible on the surface of the cone were found to be body fixed. A blunt 3-deg half-angle cone was tested with various distributed and isolated roughness elements.

Planar laser-induced fluorescence imaging in shock tube flows

Abstract: The planar laser-induced fluorescence (PLIF) imaging method was used to perform flow visualization and quantitative planar thermometry in shock tube flow fields using toluene as a fluorescence tracer in nitrogen. Fluorescence quantum yield values needed to quantify PLIF images were measured in a static cell at low pressures (<1 bar) for various toluene partial pressures in nitrogen bath gas. Images behind incident and reflected shocks were taken in the core flow away from regions affected by boundary layers. Temperature measurements from these images were successfully compared with predicted values using ideal shock equations. Measured temperatures ranged between 296 and 800 K and pressures between 0.15 and 1.5 atm. The average temperature discrepancies between measurements and the predicted values behind the incident and reflected shocks were 1.6 and 3.6%, respectively. Statistical analyses were also conducted to calculate the temperature measurement uncertainty as a function of image resolution. The technique was also applied to the study of more complex supersonic flows, specifically the interaction of a moving shock with a wedge. Measured temperatures agreed well with the results of numerical simulations in all inviscid regions, and all pertinent features of the single Mach reflection were resolved.