Pressure-sensitive fasteners for active disassembly

Evaporation of stagnant (zero relative velocity) as well as moving spherical droplets of n-dodecane in a zero-gravity and high pressure nitrogen environment is modeled. The non-ideal effects, solubility of ambient gas into the liquid-phase, variable thermo-physical properties, and gas- and liquid-phase transients are included in the model. The model is quantitatively validated using published experimental data. Numerical predictions show that, for stagnant droplets at sub-critical ambient temperatures, the droplet lifetime continuously increases with pressure, while at critical temperature, the lifetime initially increases and thereafter remains almost constant. At super-critical temperatures, the lifetime decreases continuously with increasing ambient pressure and the average evaporation constant shows a local maximum at a particular ambient pressure. In the case of moving droplets, at super-critical ambient temperature, the rate of increase of average evaporation constant with ambient pressure becomes significant as the initial droplet relative velocity increases. For low initial velocities (<1 m/s), the average evaporation constant gradually increases with ambient pressure and subsequently levels-off with further increase in ambient pressure. The droplet lifetime decreases with increase in ambient pressure or initial velocity. Penetration distance of the moving droplets decreases with ambient pressure and increases with initial droplet relative velocity. The mechanisms influencing the differences in evaporation under varying conditions of pressure and temperature are discussed.

This dissertation primarily focuses on a particle-based approach to modeling drop-wall interactions encompassing two disciplines: fuel spray dynamics and thermal spray coating. The first part is about the consecutive drop-wall interactions at different impingement frequencies at a wide range of wall temperatures and ambient pressure conditions. The second part is centered around the solidification of a molten droplet at the realistic thermal spray conditions and subsequent splat and substrate behaviors. A theoretical splashing criterion is presented based on the K parameter incorporating the impingement frequency. A Lagrangian-based method, Smoothed Particle Hydrodynamics (SPH), is used to simulate the impact of a droplet train on a heated wall below and above the Leidenfrost temperature at different impingement frequencies and ambient pressure conditions. The developed SPH method is validated against the experimental results on the propagation of the crown rim’s diameter as a function of the non-dimensional time. Impact regimes are identified for various impact conditions based on the study of the time evolution of the post-impingement process. Visualizations of the impact outcomes are provided to explain the interaction between the succeeding droplets and the liquid film created by the preceding droplets. Simulations were also conducted for n-heptane droplets at different impingement frequencies and droplet diameters. It was found that the K parameter provides a better prediction for the impingement outcomes, and the effect of impingement frequency is seen as the kinematic discontinuity among the spreading lamellae, film formation, and rapidness of droplet impact. To further characterize the shift in the Leidenfrost behaviors and the corresponding impact outcomes caused by the change in ambient pressure, simulations were also conducted at 5 bar and 20 bar ambient pressures. The inhibition by high ambient pressure on the crown rim propagation was also quantified. Results show that the increase in ambient pressure impedes splashing, and the film is concentrated inwards near the impingement point. The results of this study can be used to further improve spray/wall interaction models at realistic engine conditions. In the second part of this dissertation, the existing SPH model is enhanced to investigate the outcomes of droplet impacts on substrates under thermal spray conditions. Numerical results were validated by experimental data for impact outcomes and splat thickness. The threshold of deposition splat of yttria-stabilized zirconia (YSZ) droplet impact on two different substrates, including YSZ and stainless steel, was investigated. The results show that the kinematic parameters of the droplet and initial substrate temperature collectively determine the formation of the deposition splat. A regime diagram is proposed to characterize the outcomes of thermal spray impact in terms of the Sommerfeld parameter (K parameter) and substrate temperature. As the substrate temperature increases, the splashing threshold decreases slightly, resulting in an irregular splat morphology. The heat transfer effect is more pronounced at lower substrate temperatures, causing the droplet to solidify quickly. Furthermore, a comprehensive solidification model was developed to simulate the phase change of the droplet and substrate. The developed model was validated against the experimental results using tin droplets on stainless-steel and aluminum substrate and copper droplet on copper substrate. The histories of the spread factor, the substrate temperature, and the splat height at the impingement point are validated. A parametric study on the impact of the high melting point molybdenum droplets on different substrate materials (including tin, stainless steel, zinc, yttrium stabilized zirconia, and aluminum) was performed. The temporal evolution of the solidification interface and the height/thickness of the solidified splat are reported. Temperature distributions across the splat, substrate, and the corresponding melting/re-solidification are investigated. It was found that the cooling rates for the same impingement velocity were nearly the same for the same substrate regardless of the initial substrate temperatures but were higher for higher impingement velocities. A modified Biot number and thermal diffusivity were used to describe the heat transfer characteristics of the splat substrate combination. Results show that a higher modified Biot number for the splat-substrate combination indicates a faster cooling of the splat and a higher maximum substrate temperature. Furthermore, a substrate with high thermal diffusivity also causes heat at the impingement location to be dissipated quickly, resulting in a fast-cooling rate and accelerated solidification.

Juvenile Nautilus, tested in a high-pressure animal maintenance apparatus, are sensitive to increases in ambient hydrostatic pressure as small as l × 105Nm−2 (= 1 atm = 100kPa). They respond to such pressure increases in a characteristic ‘depth alarm’ behaviour pattern, which consists primarily of rapid upward swimming. These activity bursts may serve to restore them to their original depth. The animals apparently continue this behaviour until fatigued. Pressure decrease elicits no obvious response. The pressure-sensing mechanism may be located within the statocyst, or possibly in the posterior mantle or siphuncle. The operation of. the latter two mechanisms involves tensional strain induced by the hydrostatic load in the outermost septum and wall of the siphuncular tube.

Visualization studies of the spray from swirl injectors under elevated ambient pressure

The arc discharge plasma actuator (ADPA) has wide application prospects in high‐speed flow control because of its local heating effect and strong disturbance. In this paper, the influence of ambient pressure, which ranges from 3 to 20 kPa, on the performance of a two‐electrode ADPA is investigated by a schlieren system. The duration of the arc heated region, as well as its area, is extracted by image processing. As the ambient pressure increases, different flow field evolutions occur. The duration of the ADPA heated region increases with the ambient pressure. The maximum duration reaches 1185.3 µs at 20 kPa. The velocity of the discharge‐induced blast shock wave first decreases gradually and then remains at 345 m/s for all air pressures. The blast shock wave has a higher velocity at lower pressures when it is freshly produced. A maximum blast shock wave velocity of 582 m/s is observed at the pressure of 7 kPa. The arc heated region is not sensitive to ambient pressure, but the deposited energy from the arc increases when the pressure increases.

Shape memory alloy actuators for active disassembly using ‘smart’ materials of consumer electronic products

Effects of in-nozzle flow and low-pressure zone on spray targeting of multi-hole gasoline direct injection injector

Bio oil from seeds of Kemiri Sunan (reutealis trisperma (Blanco) airy shaw) plant is particularly attractive to be studied since its high potential as alternative of biodiesel. This paper describes the results of a fundamental study of the combustion characteristics of a single droplet of blended fuel of Kemiri Sunan (reutealis trisperma (Blanco) airy shaw) biodiesel and ethanol in various levels of ambient pressure. The ambient pressures of the burning chamber were varied at 1, 3, and 5 bars. The fuels were prepared by mixing the biodiesel with the ethanol at concentrations of 0%, 10%, 20%, and 30% vol/vol. The single droplets of blended fuels were suspended using micro-syringe on a tip of the thermocouple. It was ignited and combusted using an electrical heater. The ignition and combustion processes of the single droplets were recorded using a high-speed camera. It was found that the ignition delay of the droplet decrease with the increase of ambient pressure and the concentration of ethanol in blended fuels. Also, the burning rate of blended droplets increased with increasing biodiesel concentration and pressure. The maximum droplet temperature slightly increased during the combustion with the increasing ethanol concentration, but not with increasing ambient pressure.

The deep-sea environment has the characteristics of high pressure and low temperature. In addition to the extremely high requirements on the structural reliability, the ultra-high ambient pressure also has a great impact on the working characteristics of the hydraulic source. In this paper, the efficiency characteristics of a deep-sea hydraulic source are studied in the full-ocean-depth pressure range. According to the power transfer process, the efficiency of the deep-sea motor, gear pump and hydraulic circuit is analyzed. In so doing, the oil friction loss of the motor rotor, the internal leakage of the gear pump, the viscous friction loss of the hydraulic system, etc., are calculated. Then, simulating the deep-sea high-pressure environment by the pressure cylinder, the output characteristics and corresponding input power of the prototype are measured. By analyzing the experimental data, the efficiency characteristic curve of the hydraulic source prototype, changing with the ambient pressure, is obtained. The experimental and calculation results show that, with the increase of ambient pressure, the system efficiency of the hydraulic source prototype increases first and then decreases.

Effects of natural convection on high-pressure droplet combustion

Dynamics of laser-induced plasma and cavitation bubble at high pressures and the impacts on underwater LIBS signals

Ammonia, a zero carbon energy vector, is under consideration for decarbonising marine and energy storage applications due to its high mass-based energy density compared to many alternatives. In addition, there is widespread existing supply and transportation infrastructure due to ammonia’s use as a fertiliser. When injected in its liquid form, however, ammonia behaves quite differently to traditional fuels due to its high saturation pressure and enthalpy of vaporisation, amongst other things. This means that fundamental data on ammonia sprays need to be collected in order to understand ammonia spray behaviour and calibrate models of ammonia sprays needed for design in the virtual world. Previous work on ammonia sprays has mostly focused on spray morphology at a macroscopic level (such as liquid penetration length). However, there are fewer studies of ammonia sprays at a microscopic level. In this study, liquid ammonia was injected into a constant-volume chamber using a direct injector at two injection pressures (100 bar and 150 bar) and a range of ambient pressures from 3–13 bar. This range of ambient conditions spans regimes from flash-boiling to non-flash-boiling, thereby enabling systematic investigation of the transition between these regimes. A laser diffraction technique was used for measuring the droplet sizes of the spray at different locations (in a cylindrical volume with a diameter of 10 mm) within the spray plume at 10 kHz, and the nominal droplet sizes were quantified by the Sauter Mean Diameter (SMD). These SMD values provided, at a microscopic level, an insight of the atomisation of the spray as it left the nozzle and penetrated into an environment with different densities. It was found that the tested injector leads to a breakup dominant spray behaviour with liquid ammonia and hence the SMD values decrease as ambient pressure increases. In addition, the droplets are generally smaller at the outer edge of the spray plume compared to the inner part and both the injection pressure and injection duration have a strong effect on the droplet sizes.

Haemoptysis after breath-hold diving.

The Hanford Site is home to 177 large, underground nuclear waste storage tanks. This article describes a screening study carried out in the mid 1990s that used the tank waste level measurements to assess the tanks for potential flammable gas hazards. At the time of the study, 25 of the 177 tanks were on the flammable gas watch list. The use of this monitoring data provided additional insight, resulting in operational changes on the Hanford site.The waste level measurements used in this study were made primarily to monitor the tanks for leaks and intrusions. Four measurement devices are widely used in these tanks. Three of these measure the level of the waste surface. The remaining device measures from within a well embedded in the waste, thereby monitoring the liquid level even if the liquid level is below a dry waste crust. The data from each of the four measurement devices were utilized in this investigation.The analytic method used for this screening was to look for an inverse correlation between waste level measurements and ambient atmospheric pressure. If the waste level in a tank decreases with an increase in ambient atmospheric pressure, then the compressibility may be attributed to gas trapped within the waste. In this article, this methodology is not used to estimate the volume of gas trapped in the waste. Copyright © 2002 John Wiley & Sons, Ltd.

The structural phase transformations in the chalcopyrite semiconductor AgInTe2 have been studied up to 10 GPa on both pressure increase and decrease. The experiment were carried out using angle-dispersive X-ray diffraction with synchrotron radiation and an image plate. The diffraction patterns of AgInTe2 at ambient pressure reveal two coexisting phases: the first has the chalcopyrite structure while the second has a zinc blende like structure. On pressure increase both phases transformed at 3-4 GPa to a cationdisordered structure with spacegroup Cmcm, the atomic coordinates of which -v=0.75 for Ag or In and v=0.25 for Te -correspond to an NaCl-like structure. On pressure increase the Cmcm phase was stable up to at least 10.25 GPa. On pressure decrease, the chalcopyrite phase started to reappear at 0.55 GPa, and the Cmcm phase disappeared completely at ambient pressure. In addition to the experimental study, we have also performed density functional theory calculations. The calculated transition pressure from the chalcopyrite phase to the Cmcm phase is 4.08 GPa, and the calculated atomic positions in the Cmcm phase are in excellent agreement with those determined experimentally.