Detonation-driven Shock Tube Research Articles

Experimental investigation of non-equilibrium spectra for nitrogen behind strong shock waves

The non-equilibrium spectra of shock-heated nitrogen in the UV-visible range are investigated in a detonation driven shock tube. Spectral identification indicates that the main contributors to the spectra are molecular radiation of N2(2+) and N2+(1-). Vibrational and rotational temperatures of N2(C) and N2+(B) are determined through spectral fitting. The post-shock spectra of pure nitrogen are obtained for shock velocities ranging from 6.82–9.00 km/s and P0 = 30–200 Pa at the shock arrival time. Differences between vibrational and rotational temperatures of N2(C) and N2+(B) are observed, suggesting that nitrogen is in a non-equilibrium state at shock arrival moment. Time-resolved spectra are obtained within varying delay times of 0–2.0μs at P0 = 200 Pa and shock velocity of Vsw = 6.60 km/s. Time-resolved temperatures are determined to illustrate the time-resolved non-equilibrium characteristics of nitrogen at high temperature. It is observed that the non-equilibrium characteristics of nitrogen gradually weaken with increasing time and the thermal equilibrium was not obtained within 2.0μs. Finally, the time-resolved temperatures are compared with CEA (Chemical Equilibrium with Applications) prediction, revealing that the difference in temperature between the experiment and the CEA equilibrium calculation decreases as time increases.

Steady rotation of a Mach shock: experimental and numerical evidences

This experimental and numerical work reports on the dynamical behaviour of a shock in an inert gas at the concave wall of a hollow circular chamber. The gas in the chamber was air or He + $${\rm O}_{2}$$ + 2 Ar at initial pressures $$p_{{\rm c0}}$$ ranging from 2 to 12 kPa and initial temperature T0 =288 K. The shock was generated using a detonation driven shock tube. The shock dynamics were characterized through high-speed shadowgraph recordings and high-resolution numerical simulations. For each gas and $$p_\text {c0}$$ , the experiments evidenced the formation of a Mach reflection along the wall and identified a range of initial pressures for which this configuration rotates with constant stem heights and constant velocities larger than those at the chamber entry. The numerical simulations were capable of capturing the dynamics quantitatively. These results extend to inert gases our previous work with a reactive gas for which we reported on the possibility of a steadily rotating overdriven Mach detonation. The steadiness range is narrower with the inert gases, likely because of the smaller initial pressure ratios at the chamber entry and lower support from the subsonic flow behind the shock. The initial support in the reactive case was more efficient because the discontinuities at the chamber entry were self-sustained Chapman–Jouguet detonations. Further investigations of these Mach rotating regimes should rely only on specific experiments and numerical simulations, for example, on the effect of the chamber dimensions, because of the complex non-dimensional formulation of the problem.

Method-of-characteristics model for a low-enthalpy, detonation-driven shock tube

A reduced-order model for a detonation-driven shock tube was developed using the method of characteristics (MoC). The scope of this work was limited to calorically perfect slugs of gases. Effects of momentum and heat losses were included. The governing equations for inviscid, one-dimensional flow of a calorically perfect gas were simplified using MoC. These simplified equations represented and resolved various gasdynamic phenomena such as weak compressions, rarefactions, shocks, and contact surfaces. The momentum losses in the governing equations were estimated using established friction factors. Various empirical methods were explored to determine an appropriate heat-transfer model. Based on the expected ideal wave processes in a detonation-driven shock tube, MoC subroutines were assembled into a global algorithm representing detonation tube operation. To validate the results from the reduced-order model, experiments were carried out in a small-scale detonation tube. The experiments used nitrogen as the high-pressure driver gas, stoichiometric oxyhydrogen as the detonation driver gas, and nitrogen or helium as the driven gas. Comparison with experiments showed that the detonation tube model reasonably replicated detonation tube operation for all the experimental cases. Specifically, the decaying incident shock trajectory in the driven section was replicated well, and so was the peak pressure at the driven end wall. The quasisteady plateau pressure in the detonation driver was replicated reasonably, with experimental pressure traces showing earlier decay than MoC pressure traces. The wave system produced by the reflected shock wave–contact surface interaction in the driven section was also predicted accurately by the MoC model.

China’s Detonation-driven Shock Tube Wind Tunnels: A Case Study of Transnational Science in Aeronautics during the Cold War

From the perspective of the history of technology, this paper reviews the development of a hypersonic wind tunnel in China. The key figure is Yu Hongru 俞鸿儒, who began his research into shock tube wind tunnels in the 1950s, and proposed ways to use detonation driver technology. His insight, however, was stymied during China's “Cultural Revolution.” After China’s reform and opening-up began in the late 1970s, Yu 俞 designed a hypersonic tunnel driven by backward hydrogen-oxygen detonation utilizing a dumping section and carried out verification experiments with RWTH Aachen University. After 2000, the high-temperature gas dynamics team of the Institute of Mechanics of the Chinese Academy of Sciences built the first long test-duration detonation-driven shock tunnel. This case study draws extensively upon Chinese literature, documents, and interviews. It adds to the history exploring Cold War science and technology. While much research has focused on activities in the USA and the USSR, this article contributes to the less-explored history of scientific research and development in China after 1950, demonstrating the importance of knowledge flows within the wider concept of Cold War transnational science. In addition, this transnational emphasis contributes a non-western chapter to the western-centric history of aerospace technology development.

Four-dimensional visualization of blast loading inside a detonation-driven shock tube using improved pressure-sensitive paint and digital image correlation

Four-dimensional visualization of blast loading inside a detonation-driven shock tube using improved pressure-sensitive paint and digital image correlation

Computational and Microstructural Stability Analysis of Shock Wave Interaction with NbB2-B4C-Based Nanostructured Ceramics.

Despite extensive research on developing different transition metal boride composites for aero-thermostructural applications, the understanding of the shockwave interaction using high pressure shock testing facilities and computational simulation of such interactions are much less explored. This aspect is even more important for much less explored ceramics, like NbB2-based materials. While addressing this aspect, the present investigation reports the thermostructural stability of spark plasma sintered NbB2-(0-40) mol % B4C composites under the hypersonic aero-thermodynamic conditions using a miniature detonation-driven shock tube facility. All the ceramic discs underwent mild surface oxidation, as a consequence to impulsive load together with the thermomechanical shock. Using the in situ recorded pressure pulse data together with conjugate heat transfer analysis, spatiotemporal evolution of ceramic surface temperature was computationally analyzed for the given test conditions. Importantly, the NbB2-(0 and 20) mol % B4C composite retained structural integrity even after exposure to 10 shock pulses with maximum reflected shock temperature and pressure of 5000 K and 37.5 MPa, respectively. In contrast, NbB2-40 mol % B4C underwent structural failure by shattering to pieces. An attempt has been made to rationalize such results on the basis of thermal shock resistance parameters, estimated using the Kingery and Hasselman model. It is observed that NbB2-(0 and 20) mol % B4C shows higher crack propagation resistance, that is, 20 and 30%, respectively, under thermal shock (R″) than NbB2-40 mol % B4C. Interestingly, all the shock exposed NbB2-B4C ceramics show a measurable increase in hardness, which is attributed to transient melting and solidification of constituent phases due to interaction with shock heated gas, for a short duration of ∼5 ms. Taken together, the present study establishes the potential of NbB2-B4C composites for aero-thermostructural applications.

Detonation-to-shock wave transmission at a contact discontinuity

The one-dimensional interaction of a detonation wave with a contact discontinuity was investigated analytically and experimentally for oxyhydrogen detonations. The analytical and experimental results showed that the transmitted shock through the contact surface and into a non-combustible gas can either be amplified or attenuated depending on the reflection type at the contact surface and on the ratio of acoustic impedance across it. Experiments were performed with a detonation-driven shock tube facility to determine the transmitted shock velocity into a non-combustible He/air mixture. The oxyhydrogen equivalence ratio in the detonation section was varied from 0.5 to 1.5, and the driven section He mole fraction was varied from 0.0 to 1.0 to test a broad range of acoustic impedance ratios ranging from approximately 0.36 to 1.69. The analytical results were shown to have acceptable agreement with the measured transmitted shock wave velocity in the case of a reflected rarefaction from the contact surface. Additionally, the results indicated that the detonation wave reaction zone properties could have an important role that influences the transmitted shock properties in the case of a reflected shock from the contact surface.

Insights into the mechanism of a novel shockwave-assisted needle-free drug delivery device driven by in situ-generated oxyhydrogen mixture which provides efficient protection against mycobacterial infections

BackgroundNeedle-free, painless and localized drug delivery has been a coveted technology in the area of biomedical research. We present an innovative way of trans-dermal vaccine delivery using a miniature detonation-driven shock tube device. This device utilizes~2.5 bar of in situ generated oxyhydrogen mixture to produce a strong shockwave that accelerates liquid jets to velocities of about 94 m/s.MethodOxyhydrogen driven shock tube was optimized for efficiently delivering vaccines in the intradermal region in vivo. Efficiency of vaccination was evaluated by pathogen challenge and host immune response. Expression levels of molecular markers were checked by qRT-PCR.ResultsHigh efficiency vaccination was achieved using the device. Post pathogen challenge with Mycobacterium tuberculosis, 100% survival was observed in vaccinated animals. Immune response to vaccination was significantly higher in the animals vaccinated using the device as compared to conventional route of vaccination.ConclusionA novel device was developed and optimized for intra dermal vaccine delivery in murine model. Conventional as well in-house developed vaccine strains were used to test the system. It was found that the vaccine delivery and immune response was at par with the conventional routes of vaccination. Thus, the device reported can be used for delivering live attenuated vaccines in the future.

Mechanism of transformation in Mycobacteria using a novel shockwave assisted technique driven by in-situ generated oxyhydrogen

We present a novel method for shockwave-assisted bacterial transformation using a miniature oxyhydrogen detonation-driven shock tube. We have obtained transformation efficiencies of about 1.28 × 106, 1.7 × 106, 5 × 106, 1 × 105, 1 × 105 and 2 × 105 transformants/µg of DNA for Escherichia coli, Salmonella Typhimurum, Pseudomonas aeruginosa, Mycobacterium smegmatis, Mycobacterium tuberculosis (Mtb) and Helicobacter pylori respectively using this method which are significantly higher than those obtained using conventional methods. Mtb is the most difficult bacteria to be transformed and hence their genetic modification is hampered due to their poor transformation efficiency. Experimental results show that longer steady time duration of the shockwave results in higher transformation efficiencies. Measurements of Young’s modulus and rigidity of cell wall give a good understanding of the transformation mechanism and these results have been validated computationally. We describe the development of a novel shockwave device for efficient bacterial transformation in complex bacteria along with experimental evidence for understanding the transformation mechanism.

Development of a novel miniature detonation-driven shock tube assembly that uses in situ generated oxyhydrogen mixture.

A novel concept to generate miniature shockwaves in a safe, repeatable, and controllable manner in laboratory confinements using an in situ oxyhydrogen generator has been proposed and demonstrated. This method proves to be more advantageous than existing methods because there is flexibility to vary strength of the shockwave, there is no need for storage of high pressure gases, and there is minimal waste disposal. The required amount of oxyhydrogen mixture is generated using alkaline electrolysis that produces hydrogen and oxygen gases in stoichiometric quantity. The rate of oxyhydrogen mixture production for the newly designed oxyhydrogen generator is found to be around 8 ml/s experimentally. The oxyhydrogen generator is connected to the driver section of a specially designed 10 mm square miniature shock tube assembly. A numerical code that uses CANTERA software package is used to predict the properties of the driver gas in the miniature shock tube. This prediction along with the 1-D shock tube theory is used to calculate the properties of the generated shockwave and matches reasonably well with the experimentally obtained values for oxyhydrogen mixture fill pressures less than 2.5 bars. The miniature shock tube employs a modified tri-clover clamp assembly to facilitate quick changing of diaphragm and replaces the more cumbersome nut and bolt system of fastening components. The versatile nature of oxyhydrogen detonation-driven miniature shock tube opens up new horizons for shockwave-assisted interdisciplinary applications.

Caveats for Using Shock Tube in Blast-Induced Traumatic Brain Injury Research

Blast-induced traumatic brain injury (TBI) is currently an important and very “hot” research topic because it has been acknowledged to be a significant source of morbidity and disability during the wars in Iraq and Afghanistan, among blast victims. A total of 545 academic articles about blast TBI research have been published since 1946, of which 82% (447 articles) have been published since 2003, and 57% (312 articles) were published from 2010 to 2013. A number of experimental models are currently implemented to investigate the mechanisms of blast-induced TBI in rodents and larger animals such as rabbits and swine. As the fundamental shock wave generator, shock tubes (either compressed air-driven or detonation-driven) are generally employed in these experimental models. The compressed air-driven shock tube is a horizontally mounted, circular steel tube, in which a gas at low pressure (the driven gas) and a gas at high pressure (the driver gas) are separated using diaphragms (such as polyester Mylar membrane). After the diaphragm suddenly ruptures at predetermined pressure thresholds (e.g., 126–147 kPa), shock waves are generated and propagate through the low pressure section (the driven section) toward the mouth of the shock tube. The detonation-driven shock tube is a cylindrical metal tube that is closed at one end. The blast, causing the shock waves, is generated by detonation of an explosive charge in the closed end of the tube. Both compressed air-driven and detonation-driven shock tubes can produce blast shock waves to induce blast injuries in animals. However, because of their designs and structures, both shock tubes are not able to generate the Friedlander wave (an ideal form of a primary blast wave) that occurs when a powerful explosive detonates in a free field, without nearby surfaces that can interact with the wave. A series of complex shock waves are then generated following the lead shock wave (the original shock front), including reflected shock waves, a Mach stem, an unsteady turbulent jet, and rarefaction waves. These waves can cause sudden compression or rarefaction effects upon any object encountered in their motion path, and transfer kinetic energy to the object. Therefore, if an experimental animal is placed inside the shock tube, these complex pressure waves will cause more severe and complex injuries that are rarely observed in blast victims, thus leading to false-positive results in the studies of blast TBI mechanism.

Propagation Behavior of Combustion Wave Induced by a Shock Wave Propagated into a Premixed Gas of Oxygen and Hydrogen

In this paper, experimental results were reported to investigate a behavior of combustion wave when a shock wave was transmitted into a combustible premixed gas of oxygen and hydrogen. In general, phenomena occurring in the premixed gas would be classified into four types, i.e. (a) the shock wave was just transmitted without causing ignition for the shock wave propagated with low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave was transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave having high-propagation Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a premixed gas of oxygen and hydrogen varied with an equivalence ratio, initial pressure of premixed gas and Mach number of the shock wave. As a result, the phenomena of combustion wave were classified using a cell-size of steady-propagating detonation wave. For sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. Empirical equations to evaluate a Mach number and temperature behind shock wave were obtained, which are threshold parameters to cause detonation wave behind transmitted shock wave.

Behavior of Combustion Wave Induced by Propagation of Shock Wave into Premixed Gas of Hydrogen and Oxygen

Experiments were conducted in order to investigate a behavior of comcustion wave when a shock wave was propagated into a combustible premixed gas of hydrogen and oxygen. A phenomenon occurring in the premixed gas can be classified into four types, i.e. (a) the shock wave just transmitted into the gas without causing ignition for the shock wave of low-Mach number, (b) the gas was ignited behind the shock wave and a deflagration wave was propagated following the shock wave, (c) the deflagration wave transited to a detonation wave behind the shock wave, (d) a detonation wave was directly initiated just behind incident shock wave of high-Mach number. In this study, a shock wave produced by a detonation-driven shock tube was transmitted into a hydrogen-oxygen premixed gas varied with an equivalence ratio φ, initial pressure p1 and Mach number of the shock wave Msi. As a result, the phenomena observed in the gas was classified using a cell-size λ for steady detonation wave, since the cell-size was inversely proportional to a chemical reaction rate of the gas. For the case of sensitive gases having small cell-size, the detonation wave was directly initiated behind the shock wave even though the Mach number of the shock wave was relatively low. An empirical equation to evaluate a pressure was obtained, which is a threshold pressure to ignite the gas behind incident shock wave.

Advances in detonation driving techniques for a shock tube/tunnel

Early works on the detonation driven shock tube are reviewed briefly. High initial pressure detonable mixture can be used in backward-detonation driver when the buffer tube is attached to the end of the driver for eliminating the excessive reflected peak pressure. Experimental data showed that an improvement on attenuation of the incident shock wave generated by the forward driver can be obtained, provided the diameter of the driver is larger than that of the driven section and an abrupt reduction of cross-section area is placed just beyond the diaphragm. Also, it is clearly verified by a numerical analysis. An additional backward-detonation driver is proposed to attach to the primary detonation driver and on condition that the ratios of initial pressure in the additional driver to that in the primary driver exceed the threshold value, the Taylor wave behind detonation wave in the primary detonation driver can be eliminated completely.

Study on Performance of Detonation-Driven Shock Tube

A detonation-driven shock tube firstly designed by H.R. Yu is considered to be a useful apparatus for producing high-enthalpy flow. In this apparatus, a strong shock wave is generated by detonating an oxygen-hydrogen mixture (oxy-hydrogen) and the driver gas temperature and pressure are extremely high compared with those of a conventional shock tube. However, the structure of the detonation wave is not uniform, e.g., the detonation wave has three-dimensional cellular structures and multiple transverse waves. Furthermore, the detonation wave is followed by a Taylor expansion fan and the performance of detonation-driven shock tube is not well understood. In this preliminary study, a detonation-driven shock tube is constructed and its performance is experimentally investigated by measuring pressure histories and the profile of the ionization current behind the detonation wave

Experiments and Numerical Simulation of a Shock Wave discharged from an Open-end.

It is important to investigate a pressure profile when a diffracted shock wave interacts with a reflector from a safety point of view. Because the diffracted shock waves are often generated by the explosions of combustible gases to cause serious damages against human race and surrounding buildings. The maximum pressure behind reflected shock wave is one of the most important parameter and this report is concerned with the evaluation of maximum pressure, which might be a function of Mach number of the shock wave, distance from a source of the shock wave, initial pressure of the gas, and initial diameter of the shock wave, etc. In this study, a detonation-driven shock tube of 14 m long and 50 mm diameter is used to generate a strong shock wave of propagating Mach number MS=3.0∼5.2. The shock wave is diffracted from an open end of the shock tube of 25 mm diameter and reflected from a cylindrical reflector of 50 mm diameter. These phenomena are observed using color-schlieren optical techniques and the pressure histories at the stagnation point of the reflector are simultaneously measured. As a result, (i) The behaviors of the diffracted shock wave and complicate flow-fields behind reflected shock wave are observed. (ii) An empirical equation to calculate the maximum pressure behind reflected shock wave is estimated by the results of experimental and numerical simulation.

A Study on Performance of a Detonation-Driven Shock Tube.

A detonation-driven shock tube firstly designed by H.-R. Yu, is considered as a useful facilities capable of producing high-enthalpy flow. In this apparatus, a strong shock wave is generated by detonating oxygen-hydrogen (oxyhydrogen) mixture and has characteristics that temperature as well as pressure of driver gas is extremely high compared with conventional shock tubes. However, a structure of detonation wave is not uniform e.g., detonation wave has three-dimensional cellular structures and multiple transverse waves. Furthermore, the detonation wave is followed by a Taylor expansion fan and performance of detonation-driven shock tube is not well understood. In this preliminary study, a detonation-driven shock tube is constructed and its performance is experimentally investigated by measuring pressure histories and a profile of ionization current behind detonation wave. As a result, (i) the pressure histories of detonation wave is clarified and it shows reasonable agreement with a result obtained by KASIMIR shock tube simulation code. (ii) A propagation velocity of detonation wave is coincided well with theoretical predictions assuming Chapman-Jouguet detonation wave. (iii) An equivalence ratio of oxyhydrogen mixture to produce a highest Mach number of the shock wave is evaluated as 〓≃1.7.

Oxyhydrogen combustion and detonation driven shock tube

The performance of combustion driver ignited by multi-spark plugs distributed along axial direction has been analysed and tested. An improved ignition method with three circumferential equidistributed ignitors at main diaphragm has been presented, by which the produced incident shock waves have higher repeatability, and better steadiness in the pressure, temperature and velocity fields of flow behind the incident shock, and thus meets the requirements of aerodynamic experiment. The attachment of a damping section at the end of the driver can eliminate the high reflection pressure produced by detonation wave, and the backward detonation driver can be employed to generate high enthalpy and high density test flow. The incident shock wave produced by this method is well repeated and with weak attenuation. The reflection wave caused by the contracted section at the main diaphragm will weaken the unfavorable effect of rarefaction wave behind the detonation wave, which indicates that the forward detonation driver can be applied in the practice. For incident shock wave of identical strength, the initial pressure of the forward detonation driver is about 1 order of magnitude lower than that of backward detonation.