Ambient Pressure Environment Research Articles

Atomic-Scale Friction and Adhesion at Ambient Pressure.

In this Perspective, we present the recent advancement and the prospects of atomic-scale friction and adhesion measurements across the pressure gap between ultrahigh vacuum and ambient pressure environments using variable-pressure atomic force microscopy (VP-AFM). We introduce the VP-AFM that enables nanotribological studies under various gas conditions with partial pressure ranging from UHV (1.0 × 10-10 mbar) to 1 bar. We highlight the frictional behaviors of ultrananocrystalline diamond surface in oxygen and water gas environments, as well as the chemical states probed with near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). The atomic scale degradation processes of MA(CH3NH3)PbBr3, which is an organic-inorganic hybrid perovskite (OHP) investigated with VP-AFM are introduced. Finally, we discuss the potential works on catalytic model systems including bimetallic Pt3Ni(111) and TiO2(110) and the future perspective of nanotribology under ambient conditions.

Effects of fuel injection pressure and quantity on low octane gasoline sprays in a simulated high-pressure ambient environment of a gasoline compression ignition engine

Gasoline Compression Ignition technology using low-octane gasoline-like fuel can lead to very low NOx and Soot emissions and enhanced thermal efficiency than conventional diesel engines. The difference in test fuel properties is a significant reason for the difference in the fuel–air mixture formation in Gasoline Compression Ignition engines offering these advantages. In this study, microscopic and macroscopic spray characterisation of baseline diesel, 50 % v/v diesel blended with 50 % v/v gasoline (G50), and 20 % v/v diesel blended with 80 % v/v gasoline (G80) are conducted in a high-pressure ambient environment relevant to Gasoline Compression Ignition engines. The study was performed in a constant volume spray chamber in non-reacting conditions using Phase Doppler Interferometry and Diffused Backlit Illumination techniques. The test fuels were injected into a 30 bar ambient pressure environment at 400, 500, and 700-bar fuel injection pressures. The liquid spray penetration length of gasoline-diesel blends was slightly shorter than baseline diesel, but their spray cone angles and entrained air mass were significantly higher. The average axial droplet velocity was higher, and the Sauter Mean Diameter was lower for gasoline-diesel blends than baseline diesel 40 mm away from the injector nozzle exit, indicating superior mixture formation for the gasoline-diesel blends. The effect of droplet collision and injected fuel quantity on droplet size distribution was assessed in all test fuels. Droplet collisions increased the Sauter mean diameter of the spray at farther distances. Smaller fuel injection quantities decreased the Sauter mean diameter of the spray, increasing the probability of unburnt hydrocarbon emission producing ultra-lean regions in the engine combustion chamber.

Solvation, Surface Propensity, and Chemical Reactions of Solutes at Atmospheric Liquid-Vapor Interfaces.

surface is covered by oceans, a large number of liquid aerosol particles fill the air, and clouds hold a tiny but critical fraction of Earth's water in the air to influence our climate and hydrology, enabling the lives of humans and ecosystems. The surfaces of these liquids provide the interface for the transfer of gases, for nucleation processes, and for catalyzing important chemical reactions. Coupling a range of spectroscopic tools to liquid microjets has become an important approach to better understanding dynamics, structure, and chemistry at liquid interfaces. Liquid microjets offer stability in vacuum and ambient pressure environments, thus also allowing X-ray photoelectron spectroscopy (XPS) with manageable efforts in terms of differential pumping. Liquid microjets are operated at speeds sufficient to allow for a locally equilibrated surface in terms of water dynamics and solute surface partitioning. XPS is based on the emission of core-level electrons, the binding energy of which is selective for the element and its chemical environment. Inelastic scattering of electrons establishes the probing depth of XPS in the nanometer range and thus its surface sensitivity.In this Account, we focus on aqueous solutions relevant to the surface of oceans, aqueous aerosols, or cloudwater. We are interested in understanding solvation and acid dissociation at the interface, interfacial aspects of reactions with gas-phase reactants, and the interplay of ions with organic molecules at the interface. The strategy is to obtain a link between the molecular-level picture and macroscopic properties and reactivity in the atmospheric context.We show consistency between surface tension and XPS for a range of surface-active organic species as an important proof for interrogating an equilibrated liquid surface. Measurements with organic acids and amines offer important insight into the question of apparent acidity or basicity at the interface. Liquid microjet XPS has settled the debate of the surface enhancement of halide ions, shown using the example of bromide and its oxidation products. Despite the absence of a strong enhancement for the bromide ion, its rate of oxidation by ozone is surface catalyzed through the stabilization of the bromide ozonide intermediate at the interface. In another reaction system, the one between Fe2+ and H2O2, a similar intermediate in the form of highly valent iron species could not be detected by XPS under the experimental conditions employed, shedding light on the abundance of this intermediate in the environment but also on the constraints within which surface species can be detected. Emphasizing the importance of electrostatic effects, we show how a cationic surfactant attracts charged bromide anions to the interface, accompanied by enhanced oxidation rates by ozone, overriding the role of surfactants as a barrier for the access of gas-phase reactants. The reactivity and structure at interfaces thus result from a subtle balance between hygroscopic and hydrophobic interactions, electrostatic effects, and the structural properties of both liquids and solutes.

CFD simulations of under-expanded hydrogen jets under high-pressure injection conditions

Large-eddy simulations (LES) of hydrogen jets under highly under-expanded conditions are carried out. Computational fluid dynamics (CFD) analysis appears extremely useful to fully understand and optimize the hydrogen injection process, like in internal combustion engines. This work aims to analyze hydrogen high-pressure injection in the near-nozzle region, investigating the formation process and the structure of the Mach disks and the transition to turbulent jets, for nozzle pressure ratios (NPR) of 5.8 and 30. A real fluid model is utilized and compared against the simpler ideal gas model, for injections into an ambient pressure environment. Furthermore, hydrogen-air mixing evolution is investigated in the far-field region. Average quantities obtained from statistical analysis on LES simulations are compared with available data. The near nozzle region, except for the initial transient part, is better captured by accurate spatial discretization methods, while properly predicting far-field effects, like turbulence and acoustic effects, seems to be mostly related to time discretization schemes.

Passive cooling in Aerogel-Based insulation systems for liquid hydrogen upper stage launch vehicle tanks

Spray-On Foam Insulation (SOFI) is typically used to protect the windward-facing side of flight tanks for space launch vehicle liquid hydrogen (LH2) stages. SOFI is an excellent insulator in ambient pressure environments, however, its performance pales in comparison to reflective-type systems such as Multi-Layer Insulation in the thermal radiation dominated vacuum environment of space. If a windward insulation system employing radiation shields could be devised to replace or supplement SOFI, the on-orbit heat load could be drastically reduced, and the residual propellants could then be used to facilitate secondary missions. Such insulation systems, utilizing aerogel blanket insulation, have been explored by the Cryogenics Test Laboratory at NASA Kennedy Space Center. Owing to its nano-porous structure, aerogel is an excellent adsorbent as well as an insulator at cryogenic temperatures and will readily uptake condensable background gasses such as air when protecting a surface near LH2 temperatures. When an adsorbed blanket is rapidly exposed to a vacuum, such as during the ascent of a rocket, it will release the background gas, producing a passive cooling effect that could potentially reduce or eliminate the heat load on the propellant tank for a time. This work discusses the setup and results of a test program carried out to determine the effectiveness and impact of this cooling effect as it pertains to LH2 upper stage tanks. A vertical-cylindrical liquid nitrogen (LN2) calorimeter test instrument acted as the upper stage analog. The cold-mass was wrapped with two layers of 10 mm thick aerogel blanket material, with and without aluminum heat shields depending on the test, and interspersed with numerous thermocouple temperature sensors. Gaseous argon was used as a stand-in for air as the condensable background gas. The test procedure mimicked vehicle cryo-loading/stabilization, and ascent phases, with the ascent phase accomplished using parallel vacuum pumps. Results show that the desorption cooling effect was enough to not only eliminate the heat load on the LN2 cold-mass entirely, but further refrigerated the liquid below its boiling point.

Copper migration and surface oxidation of in ambient pressure environments

Chemical modifications such as intercalation can be used to modify surface properties or to further functionalize the surface states of topological insulators (TIs). Using ambient pressure x-ray photoelectron spectroscopy, we report copper migration in , which occurs on a timescale of hours to days after initial surface cleaving. The increase in near-surface copper proceeds along with the oxidation of the sample surface and large changes in the selenium content. These complex changes are further modeled with core-level spectroscopy simulations, which suggest a composition gradient near the surface which develops with oxygen exposure. Our results shed light on a new phenomenon that must be considered for intercalated TIs—and intercalated materials in general—that surface chemical composition can change when specimens are exposed to ambient conditions.

Pressure Gradient Squeezing Hydrogen out of MnOOH: Thermodynamics and Electrochemistry.

Pressure of gigapascal (GPa) is a robust force for driving phase transitions and chemical reactions with negative volume change and is intensely used for promoting combination/addition reactions. Here, we find that the pressure gradient between the high-pressure region and the ambient-pressure environment in a diamond anvil cell is an even stronger force to drive decomposition/elimination reactions. A pressure difference of tens of GPa can "push" hydrogen out from its compounds in the high-pressure region to the environment. More importantly, in transition metal hydroxides such as MnOOH, the protons and electrons of hydrogen can even be separated via different conductors, pushed out by the high pressure, and recombine outside under ambient conditions, producing continuous current. A pressure-gradient-driven battery is hence proposed. Our investigation demonstrated that a pressure gradient is a special and powerful force to drive decomposition and electrochemical reactions.

Ambient pressure mapping of resonant Auger spectroscopy at BL02B01 at the Shanghai Synchrotron Radiation Facility.

During the past few decades, resonant Auger spectroscopy (RAS) has presented some advantages in elucidating the electronic structure of free molecules, liquids, and solids. To further extend the application of RAS in complex in situ environments, the ambient pressure system should be developed to characterize the gas-solid and liquid-solid interfaces. In this paper, we describe the design and performance of an ambient pressure mapping of resonant Auger spectroscopy (mRAS) system newly developed at BL02B01 at the Shanghai Synchrotron Radiation Facility. This system is unique in that the ambient pressure soft x-ray absorption spectroscopy (sXAS) can be measured in Auger electron yield with kinetic energy (KE) resolved. We can obtain a mapping of the resonant Auger spectroscopy (mRAS) in the near ambient pressure environment. This approach provides an additional dimension of information along the KE of Auger electrons to reveal details of the valence and unoccupied states at the vicinity of the absorption edge. Complementary to the photoemission spectroscopy that probes the core levels, in situ two-dimension mRAS characterization is useful in studying the electronic structure of complex interfaces of gas-solid and liquid-solid under realistic operating conditions. We herein present the in situ oxidation of Cu(111) in the ambient oxygen environment as demonstration of the mRAS capability. Specifically, resolving the Auger features gives valuable clues to the molecular level understanding of chemical bonding and the evolution of orbital hybridization. In addition, the mRAS results of spatial resolution and mbar range gas pressure are shown and discussed.

Macroflash boiloff calorimetry instrument for the measurement of heat transmission through materials

The Macroflash is a flat plate boiloff calorimeter that provides effective thermal conductivity (ke) data for a wide range of materials from thermal insulation to structural composites to ceramics. The apparatus and method provide a practical, standardized way to measure heat transmission through materials under steady-state conditions at below-ambient temperatures and under different compressive loads. Another unique feature of this device is that it can provide test data at both large and small temperature differences. Using liquid nitrogen as a method to directly measure the heat flow rate, the device is applicable to testing under an ambient pressure environment at a wide range of temperatures, from 77 K to 403 K. Test specimens may be isotropic or non-isotropic; homogeneous or non-homogeneous. The Macroflash is currently calibrated in the range from approximately 10 mW/m-K to 1,000 mW/m-K using well-characterized materials. Reference data for hundreds of test specimens including foams, powders, aerogels, plastics, composites, carbon composites, wood, glass, ceramic, metal, and multi-layered composites have been compiled from Macroflash testing. The Macroflash apparatus is described and its operation, instrumentation, and control system discussed. The calibration approach is detailed as well as analysis of key data sets of standard materials.

An Experimental Study on the Effects of Atomized Rain of a High Velocity Waterjet to Downstream Area in Low Ambient Pressure Environment

A better understanding of the atomized rain characteristics in low ambient pressure areas is beneficial in reducing the jeopardizing effect of flood discharge atomization on high-altitude hydropower stations. A random splash experiment is designed with two measurement planes to investigate the effects of low ambient pressure on downstream atomized rain under the complicated conditions of low ambient pressure (within 0.60P0~1.00P0) and high waterjet velocity (at a magnitude of 10 m/s). The results demonstrate that the atomized rain (rain intensity ≥ 2 mm/h) downstream, characterized by two-dimensional distribution, can be enhanced by decreasing the ambient pressure and by increasing the inflow discharge. When the ambient pressure decreases at the same inflow discharge, both the distance of the rain intensity lines (40 mm/h, 10 mm/h, 2 mm/h) in the horizontal plane from the constricted nozzle outlet and the average rain amount in the inclined plane within the atomized source ratio of ((0~30) × 10−3)% appear as “linear” growth. With the ambient pressure decreasing by 0.10P0, the range of those characteristic rain intensity lines is expanded by 0.68%~1.37%, and the average rain amount is enlarged by 11.06%~20.48%. When keeping the low ambient pressure unchanged, both the point average rain intensity reduction along the releasing centerline and the surface average rain amount growth with increased inflow discharge all follow an exponential function. The aeration reduction in the waterjet boundary and the resistance reduction in atomized water-droplets are contributing factors for the enhancement effect of low ambient pressure. This study can enable the establishment of a foundation to further predict flood discharge atomization in a high-altitude environment.

Reynolds number influence on the backpressure-induced shock–boundary layer interaction in an asymmetric supersonic expansion flow

In the present study, asymmetric supersonic expansion flow produced by an annular conical supersonic nozzle has been studied under static conditions. To understand the details of Reynolds number influence on the backpressure-induced shock–boundary layer interaction, a computational program has been carried out. Particular attention has been paid to the shock physics and characteristics of shock–shock and shock–boundary layer interaction change in the flow field when applied to engines operating in different ambient pressure environments. The identification of this Reynolds number correlated flow behavior changes is important for low supersonic expansion flow in engines, as it is directly attributed to the limits of off-design capability on launcher performance. The obtained results show that Reynolds number has significant influence on flow pattern at low pressure ratio, PR, conditions. When PR grows from 2.00 to 2.10, the most prominent phenomenon is that the separation point on the upper wall keeps moving downstream while the one on the lower wall keeps still. This special flow pattern results in a gradual transition from a Mach reflection to the regular reflection. However, for results at higher pressure ratios than 2.57, the comparison between the predicted shock patterns at the three ambient conditions shows a close one for these higher PR regimes. This suggests that the Reynolds number effect is going to weaken at a higher Mach number flow regime when the flow Reynolds number increases with an increase of the pressure ratio as well as the expansion flow Mach number.

Height Measurement in Seamless Indoor/Outdoor Infrastructure-Free Navigation

Using the barometer for height estimation often requires the use of external reference to correct biases in measurement. These biases are often caused by the change of the ambient pressure environment. The barometric height estimation is especially challenging in tactical and rescue applications where high temperatures or sudden large pressure shocks can change the pressure rapidly. We assess the suitability of barometers for infrastructure-free navigation in tactical applications. First, this paper investigates the effect of transition in seamless indoor/outdoor navigation. Second, we measure the effects of pressure shocks, caused by explosions or firearms, on low-cost and lightweight micro-electromechanical barometers to ensure that the sensors are capable of operating under these conditions. Finally, we investigate the use of sonar measurement to estimate the vertical speed as an alternative to the reference barometer for infrastructure-free navigation. The fusion of barometer and sonar achieved on average 0.46-m root-mean-square error (RMSE) while simple barometric height estimation had a RMSE of 0.65 m. The fusion method had no errors over 1.5 m during the test. This accuracy is generally sufficient to find the correct floor level which is crucial for tactical situational awareness. The goal of this paper is to develop the methods for seamless indoor/outdoor navigation, and therefore the most important result of this paper is that the error caused when transitioning between outdoor and indoor environments is visibly reduced.

Regolith behavior under asteroid-level gravity conditions: low-velocity impact experiments

The dusty regolith covering the surfaces of asteroids and planetary satellites differs in size, shape, and composition from terrestrial soil particles and is subject to environmental conditions very different from those found on Earth. This regolith evolves in a low ambient pressure and low-gravity environment. Its response to low-velocity impacts, such as those that may accompany human and robotic exploration activities, may be completely different than what is encountered on Earth. Experimental studies of the response of planetary regolith in the relevant environmental conditions are thus necessary to facilitate future Solar System exploration activities.We combined the results and provided new data analysis elements for a series of impact experiments into simulated planetary regolith in low-gravity conditions using two experimental setups and a range of microgravity platforms. The Physics of Regolith Impacts in Microgravity Experiment (PRIME) flew on several parabolic aircraft flights, enabling the recording of impacts into granular materials at speeds of ∼ 4–230 cm/s. The COLLisions Into Dust Experiment (COLLIDE) is conceptually close to the PRIME setup. It flew on the Space Shuttle in 1998 and 2001 and more recently on the Blue Origin New Shepard rocket, recording impacts into simulated regolith at speeds between 1 and 120 cm/s.Results of these experimental campaigns found that there is a significant change in the regolith behavior with the gravity environment. In a 10 −2g environment (with g being the gravity acceleration at the surface of the Earth), only embedding of the impactor was observed and ejecta production was produced for most impacts at > 20 cm/s. Once at microgravity levels (<10−4g), the lowest impact energies also produced impactor rebound. In these microgravity conditions, ejecta started to be produced for impacts at > 10 cm/s. The measured ejecta speeds were somewhat lower than the ones measured at reduced-gravity levels, but the ejected masses were higher. In general, the mean ejecta velocity shows a power-law dependence on the impact energy with an index of ∼ 0.5. When projectile rebound occurred, we observed that its coefficients of restitution on the bed of regolith simulant decrease by a factor of 10 with increasing impact speeds from ∼ 5 up to 100 cm/s. We could also observe an increased cohesion between the JSC-1 grains compared to the quartz sand targets.

Effects of ambient pressure on single-pulse laser processing of austenite stainless steel

The effects of ambient pressure on single-pulse laser processing of austenite stainless steel were investigated in this study. The ambient pressure environments were created by Ar gas and ranged from 0.001 bar to 45 bar. It is observed that the ejection and expansion of the metal vapor are severe under a low pressure and gradually become limited with the increase of ambient pressure. Numerous oxides remain on the molten-pool surface under a low pressure, and a shiny solidified molten-pool surface without oxides can be obtained when the pressure is higher than 10 bar. Furthermore, the ripples induced by the ejection of the metal vapor were detected on the solidified molten-pool surface, and it significantly reduced with the increase in ambient pressure. Larger aspect ratios of molten pools were obtained under higher pressures, and a tendency wherein the primary dendrite arm spacing and grain size decrease with the increase of ambient pressure was observed. When the ambient pressure changed from 0.001 bar to 45 bar, the aspect ratio increased by approximately 12%, the dendrite arm spacing decreased approximately 12% and 4% on the side and center positions, respectively, and the grain size decreased approximately 37%.

Comparison of the Propulsion Performance of Aerospike and Bell-Shaped Nozzle Using Hydrogen Peroxide Monopropellant Under Sea-Level Condition

ABSTRACTThis study investigates numerically the performance of applying aerospike nozzle in a hydrogen peroxide mono-propellant propulsion system. A set of governing equations, including continuity, momentum, energy and species conservation equations with extended k-ε turbulence equations, are solved using the finite-volume method. The hydrogen peroxide mono-propellant is assumed to be fully decomposed into water vapor and oxygen after flowing through a catalyst bed before entering the nozzle. The aerospike nozzle is expected to have high performance even in deep throttling cases due to its self-compensating characteristics in a wide range of ambient pressure environments. The results show that the thrust coefficient efficiency (Cf,η) of this work exceeds 90% of the theoretical value with a nozzle pressure ratio (PR) in the range of 20 ~ 45. Many complex gas dynamics phenomena in the aerospike nozzle are found and explained in the paper. In addition, performance of the aerospike nozzle is compared with that of the bell-shape nozzle.

Photoelectron Spectromicroscopy Through Graphene of Oxidised Ag Nanoparticles

Performing electron based spectroscopies at ambient pressure environments, for instance, to investigate catalytic reactions, when the energy of the electrons is below 1.5 keV is extremely challenging. This limitation, known as the “pressure gap”, was to some extent overcome about 15 years ago for X-ray photoelectron spectroscopy (XPS) experiments made at near ambient pressure, but only recently the first pioneering experiments at true ambient pressure with XPS have been realized. These investigations use graphene (Gr)-sealed cells to separate the ambient and vacuum environments by exploiting the properties of Gr to create a barrier for the transmission of liquids or gases and to be partially transparent to low energy photoelectrons. In such cells, the Gr membrane can be used as a bare substrate for other materials or can be an active part of a system. When nanoparticles are deposited or grown on the Gr membrane and exposed to an ambient pressure environment a raising question is if the areas of the nanoparticles directly in contact with Gr will experience the same environment conditions as the areas freely exposed to the atmospheric pressure. To answer to this question we have designed a pilot experiment where Ag nanoparticles are grown on one side of the Gr and ex-situ exposed to molecular oxygen to investigate the oxidation rate of the Ag atoms in contact with the Gr and those directly exposed to the oxygen molecules. Spatially resolved photoemission and high resolution scanning electron microscopy measurements have demonstrated that also the Ag atoms at the interface between Gr and Ag nanoparticles experiences the environment, showing, in our case, an oxidation comparable with that of the other areas of the nanoparticles.

Temporal evolution in a dissipative air-coupled spherical dielectric elastomer actuator

A viscoelastic model is developed for a dissipative Thin spherical dielectric elastomer actuator (TSDEA), with which the air-coupled effect and the ambient pressure effect are considered. The evolution equation is constructed by using the rheological model and is solved by employing the improved Euler method. The sealed air in the TSDEA is governed by the ideal gas state equation. Numerical results show that the air-coupled effect is helpful for evolving into the stable state. It also shows that the ambient pressure and the loading parameters play an important role on the temporal evolution behavior of the TSDEA. The TSDEA can evolve into a much larger size configuration in a low ambient pressure environment than that in a high ambient pressure environment. The model can be employed to analyze or predict the viscoelastic behaviors of a TSDEA.

Advances in liquid phase soft-x-ray photoemission spectroscopy: A new experimental setup at BESSY II.

A state-of-the-art experimental setup for soft X-ray photo- and Auger-electron spectroscopy from liquid phase has been built for operation at the synchrotron-light facility BESSY II, Berlin. The experimental station is named SOL3, which is derived from solid, solution, and solar, and refers to the aim of studying solid-liquid interfaces, optionally irradiated by photons in the solar spectrum. SOL3 is equipped with a high-transmission hemispherical electron analyzer for detecting electrons emitted from small molecular aggregates, nanoparticles, or biochemical molecules and their components in (aqueous) solutions, either in vacuum or in an ambient pressure environment. In addition to conventional energy-resolved electron detection, SOL3 enables detection of electron angular distributions by the combination of a ±11° acceptance angle of the electron analyzer and a rotation of the analyzer in the polarization plane of the incoming synchrotron-light beam. The present manuscript describes the technical features of SOL3, and we also report the very first measurements of soft-X-ray photoemission spectra from a liquid microjet of neat liquid water and of TiO2-nanoparticle aqueous solution obtained with this new setup, highlighting the necessity for state-of-the-art electron detection.

A discussion about the method to study the effect of ambient pressure on hydraulic jetting

Hydraulic jetting techniques are widely used to improve the rate of penetration (ROP) and enhance oil recovery (EOR) in the oil and gas field. However, a high ambient pressure could significantly weaken the performance of hydraulic jetting at the bottom of wells, especially in the case of deep (>4500m) and ultra-deep (>6000m) wells. Hence, many excellent studies have been conducted to study the effect of the ambient pressure on a hydraulic jetting. A method to generate ambient pressure by changing the diameter of the outlet valve is widely used. However, in our study, it is proved that the method cannot simulate the real ambient pressure environment for a hydraulic jetting. In our study, an outlet valve is used to maintain the pressure in the pressure vessel. Jet pressure and impact pressure with different ambient pressures at different standoff distances are measured. The jet pressure remains unchangeable until the ambient pressure exceeds a threshold and then increases linearly with the ambient pressure. The threshold is approximately equal to the product of the pressure drop of the nozzle and the square of the nozzle discharge coefficient. The hydrostatic pressure is not evenly distributed in the pressure vessel under the generated ambient pressure. According to Bernoulli's equation, the process to generate ambient pressure by this method is the conversion process between the hydrostatic pressure and the dynamic pressure. Given that the ambient pressure is evenly distributed at the bottom of oil wells, it may not have an influence on the hydraulic jetting. Performing an experiment to measure the effect of the ambient pressure on hydraulic jetting at the bottom of oil wells is strongly recommended. The results in our study are helpful for the application of hydraulic jetting in oil and gas industry.

Electron number density measurements using laser-induced breakdown spectroscopy of ionized nitrogen spectral lines

Spectrally broadened, singly ionized nitrogen emission lines are monitored to determine electron number densities in laser-induced plasma from aluminum, nano- and bulk-zinc monoxide, as well as hydrogen-rich plastic and wood targets. The optical emission spectra for N II at the average wavelength of 500.33nm are recorded in standard ambient temperature and pressure environments. For time delays of 25 to 450ns from the onset of the 1064-nm Nd:YAG radiation induced optical breakdown, the electron number densities in the range of 5.1 ±1 ×1019 to 0.22 ±0.04 ×1019cm−3 are inferred from the continuum and the nitrogen spectral line analysis. In addition, the corresponding electron temperatures of 10.1 ±0.6eV to 1 ±0.2eV are determined from the calculated absolute spectral radiance values in the near infrared region. At the early stages of plasma emission, Balmer series hydrogen lines are embedded in free electron radiation yet the broadening of the N II lines yields reliable electron number density values.