Gas Expansion Research Articles

Experimental and synthetic laser-absorption-spectroscopy measurements of temperature, pressure, and CO at 1 MHz for evaluation of post-detonation fireball models

A quantum-cascade-laser-absorption-spectroscopy (QCLAS) diagnostic was used to characterize post-detonation fireballs of RP-80 detonators via measurements of temperature, pressure, and CO column pressure at a repetition rate of 1 MHz. Scanned-wavelength direct-absorption spectroscopy was used to measure CO absorbance spectra near 2008.5 cm−1 which are dominated by the P(0,31), P(2,20), and P(3,14) transitions. Line-of-sight (LOS) measurements were acquired 51 and 91 mm above the detonator surface. Three strategies were employed to facilitate interpretation of the LAS measurements in this highly nonuniform environment and to evaluate the accuracy of four post-detonation fireball models: (1) High-energy transitions were used to deliberately bias the measurements to the high-temperature outer shell, (2) a novel dual-zone absorption model was used to extract temperature, pressure, and CO measurements in two distinct regions of the fireball at times where pressure variations along the LOS were pronounced, and (3) the LAS measurements were compared with synthetic LAS measurements produced using the simulated distributions of temperature, pressure, and gas composition predicted by reactive CFD modeling. The results indicate that the QCLAS diagnostic provides high-fidelity data for evaluating post-detonation fireball models, and that assumptions regarding thermochemical equilibrium and carbon freeze-out during expansion of detonation gases have a large impact on the predicted chemical composition of the fireball.

Scaling dynamics of the ultracold Bose gas

The large-scale expansion dynamics of quantum gases is a central tool for ultracold gas experiments and poses a significant challenge for theory. In this work we provide an exact reformulation of the Gross-Pitaevskii equation for the ultracold Bose gas in a coordinate frame that adaptively scales with the system size during evolution, enabling simulations of long evolution times during expansion or similar large-scale manipulation. Our approach makes no hydrodynamic approximations, is not restricted to a scaling ansatz, harmonic potentials, or energy eigenstates, and can be generalized readily to non-contact interactions via the appropriate stress tensor of the quantum fluid. As applications, we simulate the expansion of the ideal gas, a cigar-shaped condensate in the Thomas-Fermi regime, and a linear superposition of counter propagating Gaussian wavepackets. We recover known scaling for the ideal gas and Thomas-Fermi regimes, and identify a linear regime of aspect-ratio preserving free expansion; analysis of the scaling dynamics equations shows that an exact, aspect-ratio invariant, free expansion does not exist for nonlinear evolution. Our treatment enables exploration of nonlinear effects in matter-wave dynamics over large scale-changing evolution.

Structure and generation mechanism of blue whirls

Blue whirls are newly discovered blue rotating flames transitioned from fire whirls generated on liquid fuel surfaces. Compared with the traditional fire whirls, blue whirls have a distinct flame structure and are almost soot-free. Studies of the blue whirl are expected to promote the development of clean combustion theory and technology. In this paper, we numerically and theoretically investigate the lifting process of fire whirls and blue whirls, and then discuss their structure and transition mechanisms. In contrast to the explanations in the literature, it is found that blue whirls can be created without the occurrence of bubble-type vortex breakdown in the rotating flow. The blue whirl can be considered as a special form of lifted fire whirl with a considerable liftoff distance and without being blown out. According to the simulation, both blue whirls and fire whirls have the typical triple-flame structure. The unique structure of blue whirls is closely related to the thermal expansion of gas and the restriction of the radial flow by the axis. The theoretical solution of the unified lifting curve for fire whirls and blue whirls is obtained, which is qualitatively in agreement with the numerical result. There are 4 different branches in the lifting curve, two of which are stable, respectively representing fire whirls with small liftoff distances, and blue whirls with larger liftoff distances. The unstable branches between the stable branches lead to non-continuous transitions between fire whirls and blue whirls, as observed in the experiment. The current study explains the existing physical phenomenon and makes valuable predictions that may guide future experiments and simulations.

Impact of the convergent geometric profile on boundary layer separation in the supersonic over-expanded nozzle

Abstract This article aims to conduct a numerical investigation of phenomena induced by gas expansion in chemical propulsion nozzles. A numerical simulation of full-scale flat convergent-divergent nozzle geometry using the finite volume method on structured meshes is performed to predict the change in the convergent geometry on the boundary layer separation resulting from a shock/shock and shock/boundary layer. Two turbulence models are tested, namely, the k−ε and k−ω shear-stress transport (SST) models. Three steps are considered to achieve this work. First, 10 numerical schemes are tested to select the accurate one. The findings of the first step are used to predict the boundary layer separation in a supersonic overexpanded nozzle. The available experimental data from the NASA Langley Research Center are used to validate the results. The third step concerns investigating the impact of the convergent geometric profile on the downstream flow of the nozzle. The obtained results are analyzed and compared with the experimental data. These results show that convergent geometry may cause the formation of different shock structures and different points of flow separation and modifies several parameters of the flow and nozzle performance downstream the throat. The findings indicated that the convergent profile must be considered during the design phase when focusing on the problem of boundary layer separation in the supersonic overexpanded regime nozzles.

Combined effect of tungsten inert gas welding and roller expansion processes on mechanical and metallurgical characteristics of heat exchanger tube-to-tubesheet joints

Tube-to-tubesheet joints are one of the major vulnerable locations prone to cracks in heat exchangers. The manufacturing processes of these joints have an important role in providing structural integrity to the heat exchangers. The main objective of this work is to study the impact of the combined effect of tungsten inert gas weld and expansion percentages of 3%, 5% and 7% on the structural integrity of carbon steel-based tube-to-tubesheet joints. The results show that the pull-out strength of hybrid welded and expanded using 3%, 5% and 7% expansion percentages has exceeded the tube axial strength. The minimum leak path of the welds was satisfactorily above two-thirds of the tube wall thickness. Vickers hardness was restricted at the adjacent regions of weld to below 250 HV. The microstructural studies indicate that the higher the expansion percentage, the smaller the grains at the inner tube surface and the higher the extent the fine grains formed from the inner tube surface. The effect of expansion on the grains at the inner and outer tube surfaces of the transition zone and the unexpanded zone was found negligible. The absence of grain refinement on the outer tube surface using light expansion at a 3% expansion percentage indicated that the contact pressure was inadequate on the tube-to-tubesheet interface. The hardness at the expanded zone and transition zone of the inner tube surface was higher than at the outer tube surface due to the plastic deformation caused by the intensive roller expansion pressure.

Mathematical and physical analysis of air compression waste heat dissipation used as energy storage

As part of the research in the field of pumping vacuum chambers in the Environmental Electron Microscope, research on supersonic flow through apertures is being carried out at the Department of Electrical and Electronic Technology of the Brno University of Technology in cooperation with the Institute of Scientific Instruments of the CAS. This research, which deals with gas compression and expansion, utilizes this experience in the paper that deals with the issue of gas heating during compression when filling a storage tank as an energy storage device. This heating of the gas is a loss relative to the stored energy and there is an interest in limiting this heating or using this heat in other ways. This paper deals with limiting the heating of compressed air when filling a storage tank as energy storage.

Wellbore multiphase flow behaviors of gas kick in deep water horizontal drilling

During the deepwater drilling, the complicated gas-liquid-solid multiphase flow will occur if the formation gas enters and migrates in the wellbore. Through understanding of the wellbore flow behaviors is of great importance for the blowout prevention and well control. Considering the dynamic mass and heat transfer process in wellbore caused by alternating ambient temperature field, a multiphase flow model of multicomponent fluid in wellbore is deduced and developed, including the continuity equation, momentum conservation equation and energy conservation equation. Furthermore, the corresponding initial and boundary conditions are proposed for different working conditions in deepwater drilling, and an efficient numerical solution method is established, including dynamic mesh generation method and discrete solution method of partial differential equations. Applied in a deep-water kicking well, the proposed model is used to analyze the multiphase flow rules in the wellbore. The results show that in the process of annular fluid returning from the bottomhole, the pressure generally decreases linearly, while the temperature change is nonlinear. The temperature first rises and then falls at the formation section, and first falls and then rises at the seawater section. Furthermore, the pit gain increases approximately in a quadratic polynomial relationship, caused by the rise and expansion of gas in the wellbore, and the pressure drop and gas influx rate increase at the bottomhole. In the process of kick evolution, the standpipe pressure and bottomhole pressure gradually decrease, which can be an important sign for kick detection.

Ignition of an ionic liquid dual-mode monopropellant using a microwave plasma torch

The blend of hydroxylammonium nitrate (HAN) and imidazole-based ionic liquid has shown good feasibility in chemical and electric dual-mode green space propulsion. As conventional catalyst-driven ignition faces challenges arising from long preheat delay and catalyst failure, this work designs a novel ignition actuator using a microwave plasma torch. The precise tuning of the ¼-λ resonant cavity and improvement in the quality factor (QF) of the microwave igniter make the device efficient and thus allow the propellant to be ignited at a power of approximately 100 W. In the present reduced test rig, the maximum fuel flow rate corresponds to 0.1 N chemical thrusters, and the plasma-assisted ignition is mainly attributed to thermal and kinetic effects. The temperature of the actuator and the plasma torch is investigated by infrared thermometry and spectral fitting of excited molecule nitrogen, respectively. First, the hot electrode tube helps evaporate water molecules and accelerate the liquid jet through rapid gas expansion. Then, the ionic liquid quickly decomposes to small species when the flow reaches the torch with a nitrogen vibrational temperature above 4000 K and rotational temperature above 2000 K. Meanwhile, the nonequilibrium plasma-excited species enhance the combustion of gaseous intermediates by direct impact dissociation, where the OH radical profile is visualized using the planar laser-induced fluorescence technique. In addition, the copper atoms released by plasma erosion are expected to exhibit a significant catalytic effect on ionic liquid decomposition, which is a critical step in controlling the overall reaction rate. It is also noted that such mild erosion does not affect the multi-start operations during the firing test that lasts for at least 30 min.

Investigations on vapor cloud explosion hazards and critical safe reserves of LPG tanks

To clarify vapor cloud explosion hazards in process industries and strengthen emergency treatment measures, a full-scale liquefied petroleum gas (LPG) tank model was established using computational fluid dynamics (CFD). Also, gas dispersion behavior and explosion hazards under different leakage characteristics were investigated and LPG safe reserves reasonably predicted. The results showed that heavy gas expansion near the ground mainly moved along gaps between structural congestions, while continuous large-scale congestion had significant enhancement effects on gas expansion and concentration accumulation. When an LPG cloud with nonuniform concentration ignited, the turbulent flame impacted the diluted explosive cloud at high speed, resulting in more serious consequences. When LPG leakage exceeded 300 s and the aperture greater than 10 mm, the hazard zone (Pc > 2 kPa) sharply increased and therefore considered to be the key factor in controlling explosion hazards. The LPG safe reserve varied little under low protection distance (Rp) and critical overpressure (Pc), but increased exponentially when Rp and Pc exceeded 200 m and 20 kPa, respectively. The present research conclusions provided a theoretical reference for emergency disposal, disaster assessment, and reserve safety design of LPG leakage and explosion accidents.

Free expansion of an ideal gas by kinetic gas theory

We consider the adiabatic free expansion of an ideal gas. According to classical thermodynamics, the internal energy of the gas is not affected by the expansion, but kinetic gas theory predicts an average energy difference between escaping and remaining gas. This difference is transient if the gas escapes into a finite volume, consistent with the equilibrium prediction of classical thermodynamics. For escape into an infinite volume, classical thermodynamics is not applicable. Numerical calculations of the magnitude of the predicted effect are provided.

Kinetics and Product Branching Ratio Study of the CH3O2 Self-Reaction in the Highly Instrumented Reactor for Atmospheric Chemistry.

The fluorescence assay by gas expansion (FAGE) method for the measurement of the methyl peroxy radical (CH3O2) using the conversion of CH3O2 into methoxy radicals (CH3O) by excess NO, followed by the detection of CH3O, has been used to study the kinetics of the self-reaction of CH3O2. Fourier transform infrared (FTIR) spectroscopy has been employed to determine the products methanol and formaldehyde of the self-reaction. The kinetics and product studies were performed in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) in the temperature range 268-344 K at 1000 mbar of air. The product measurements were used to determine the branching ratio of the reaction channel forming methoxy radicals, rCH3O. A value of 0.34 ± 0.05 (errors at 2σ level) was determined for rCH3O at 295 K. The temperature dependence of rCH3O can be parametrized as rCH3O = 1/{1 + [exp(600 ± 85)/T]/(3.9 ± 1.1)}. An overall rate coefficient of the self-reaction of (2.0 ± 0.9) × 10-13 cm3 molecule-1 s-1 at 295 K was obtained by the kinetic analysis of the observed second-order decays of CH3O2. The temperature dependence of the overall rate coefficient can be characterized by koverall = (9.1 ± 5.3) × 10-14 × exp((252 ± 174)/T) cm3 molecule-1 s-1. The found values of koverall in the range 268-344 K are ∼40% lower than the values calculated using the recommendations of the Jet Propulsion Laboratory and IUPAC, which are based on the previous studies, all of them utilizing time-resolved UV-absorption spectroscopy to monitor CH3O2. A modeling study using a complex chemical mechanism to describe the reaction system showed that unaccounted secondary chemistry involving Cl species increased the values of koverall in the previous studies using flash photolysis to initiate the chemistry. The overestimation of the koverall values by the kinetic studies using molecular modulation to generate CH3O2 can be rationalized by a combination of underestimated optical absorbance of CH3O2 and unaccounted CH3O2 losses to the walls of the reaction cells employed.

Principles In Practice: Impact Assessment For Wagon Creek Gas Field Activities At The Bonaparte Basin Of Australia

This paper critically and conceptually analyse the environmental impact of the Wagon Creek gas field activities at the Bonaparte Basin of Australia. The report would coherently discuss the potential impacts and review of the gas filed activities using the EIA principle and suggest mitigation actions which can bring success to the activities. Previous environmental impact assessment has shown that the natural gas plant gravely affected the natural environment profoundly, because of the natural gas spill and other related activities. This shows cumulative impacts will occur when the gas expansion project commences. The overview of potential impacts is shown in table 1 as analysed from the literature review of oil and gas projects from similar locations. The report can be useful to provide the necessary confidence to proponents, decision makers and the public about the broader context and long term environmental conditions more likely to result from the gas field activities.

Study on Efficiency of Compressed Air Emergency Power Supply System Based on MATLAB

Taking a new type of emergency power supply system with compressed air as power source and expander as engine as the analysis object, the working process analysis, and energy loss analysis of the system are made. On this basis, the system analysis model was established, and the relationship between the system efficiency and each influencing parameter was obtained through MATLAB simulation calculation of the system. According to the analysis, it was concluded that when the other parameters were certain, system efficiency with the rising of tanks of compressed gas pressure reduced gradually, the volume expansion ratio of the expander first increased and then decreased, and the increase of inlet pressure expander rose. Still, its growth rate decreased gradually with the increase of leakage coefficient and plummeted. Among various parameters that would influence each other, the pressure range of compressed air stored in the air storage tank needed to be determined according to the structural parameters of the expander. In order to achieve the highest energy utilization rate of compressed gas, according to different system parameters, it was necessary to reasonably match the parameters of the gas storage tank and expander through parametric design.

Velocity distributions in a gas-gun microparticle accelerator.

Here, we build and characterize a single-stage gas-gun microparticle accelerator, where a pressurized gas expands and launches particles on a target. The microparticles in the range of 60-250 μm are accelerated by the expansion of pressurized nitrogen. By using a high-speed camera, we study how the velocity distribution of accelerated particles is modified by particle size, pressure in the gas reservoir, valve's opening time, and diaphragm's thickness and composition. We employ this microparticle accelerator to study the impact of glass particles with diameters of (69 ± 6) μm accelerated at moderate velocities ∼ (10-25) m/s, using films of poly-dimethylsiloxane as targets.

Analysis of chaos-coherence peculiarities within the chaotic phenomena of fluid at finite temperature

In this distinctive research, I explored the influence of temperature and momentum-dependent coherence and chaos radiations on particles emanated fluid with quantum correlations. The equations are elucidated by using the interferometry technique to prevail in perspicuous aphorism for the coherence-chaotic field. Chaotic parameter examines the coherence through boson femtoscopy within an evolving boson gas model and probes significant parameters within the produced fluid characterization for the potential of harmonics oscillators. The proportion of condensate of identical bosons, densities distribution, and the correlations functions for the expansion of boson gas are investigated. The findings suggest that the particular temperatures in the relativistic smashing possess the hadronic phase and the resulting sources at that phase containing hundreds of analogous boson particles divulge the robustness of quantum coherence. The correlations are delineated to analyze the coherence and source peculiarities with certain temperature ranges, particles number, and particle pairs averaging momentum. At small pair momenta, the finite condensation reduces the correlations in pion interferometry observations and strives for an insignificant effect at high particles pair momenta. As shown in the plots the graphical interpretations of the density distribution, correlations and chaotic profile against assorted apropos parameters have been demonstrated for pertinent physical reasons. The significant results divulged that the density distributions possession enhance at higher coherent emission and lower temperature regimes. Such findings reveal the lucrativeness in the field of engineering applications.

Identification approach of acoustic cavitation via frequency spectrum of sound pressure wave signals in numerical simulation

In a sono-reactor, complex ultrasound pressure wave signal can be detected, containing multiple information related to acoustic cavitation. In this present study, acoustic cavitation in a cylinder is investigated numerically. Via Fast Fourier Transfer (FFT), the sound pressure signals from sonotrode emitting surface are separated into harmonics, sub/ultra-harmonics and cavitation white noise: (1) the appearance of harmonics proved the non-linear propagation of ultrasound, (2) at the vibratory amplitude from 5∼20μm, only harmonics exists in the frequency spectra, corresponding to expansion and compression of non-condensable gas (NCG), (3) at the vibratory amplitude range of 30∼50μm, the occurrence of sub/ultra-harmonics demonstrated gaseous cavitation occurred, and (4) at the vibratory amplitude higher than 55μm, cavitation white noise arose, pointing out the initiation of vaporous cavitation. Based on the combination of frequency spectra and cavitation zones distribution, the acoustic cavitation state in water liquid is determined.

Impact of chamber back pressure on the ignition dynamics of hydrogen enriched premixed flames

The impact of chamber back pressure and H2-enrichment on flashback of premixed CH4−H2-Air flames triggered by ignition dynamics is investigated. Different back pressures are imposed by varying the exhaust flow blockage with perforated plates of different porosities. Experiments measuring the ignition transient, from kernel formation to stable flames and flashback, with increasing levels of H2-enrichment covering a wide range of operating conditions are conducted. Time-series of pressure, velocity and heat release rate are examined to characterise the ignition process. It is shown that the final state of the flame is highly modified by the over pressure caused by the volumetric expansion of the hot gases. Three different scenarios are identified: Soft ignition with direct stabilisation, transient flashback and permanent flashback. The magnitude of the over pressure generated at ignition is significantly amplified by small increases in mean back pressure which, in turn, modifies the flowrate through the injector thereby promoting flashback. In addition to its role as a pressure amplifier, increasing the combustor back pressure also affects the time lag between the over pressure and the peak in heat release rate just after ignition. The impact of H2-enrichment on flashback is investigated by keeping both the bulk injection velocity Ub and laminar burning velocity Sl0 constant for flames with 0% to 100%H2-content. It is shown that the magnitude of the over pressure approximately scales with Ub/Sl0 and is independent of the total thermal power and H2 enrichment. Although the mean flow conditions and over pressures are kept constant, the stabilisation mode directly depends on H2-content. This shows that flashback triggered by the ignition dynamics cannot be fully described by classical kinematic arguments and a new mechanism is presented.

Entropy growth during free expansion of an ideal gas

To illustrate Boltzmann’s construction of an entropy function that is defined for a microstate of a macroscopic system, we present here the simple example of the free expansion of a one dimensional gas of non-interacting point particles. The construction requires one to define macrostates, corresponding to macroscopic variables. We define a macrostate M by specifying the fraction of particles in rectangular boxes ΔxΔv of the single particle position-velocity space {x, v}. We verify that when the number of particles is large the Boltzmann entropy, S B(t), of a typical microstate of a nonequilibrium ensemble coincides with the Gibbs entropy of the coarse-grained time-evolved one-particle distribution associated with this ensemble. S B(t) approaches its maximum possible value for the dynamical evolution of the given initial state. The rate of approach depends on the size of Δv in the definition of the macrostate, going to zero at any fixed time t when Δv → 0. Surprisingly the different curves S B(t) collapse when time is scaled with Δv as: t ∼ τ/Δv. We find an explicit expression for S B(τ) in the limit Δv → 0. We also consider a different, more hydrodynamical, definition of macrostates for which S B(t) is monotone increasing, unlike the previous one which has small decaying oscillations near its maximum value. Our system is non-ergodic, non-chaotic and non-interacting; our results thus illustrate that these concepts are not as relevant as sometimes claimed, for observing macroscopic irreversibility and entropy increase. Rather, the notions of initial conditions, typicality, large numbers and coarse-graining are the important factors. We demonstrate these ideas through extensive simulations as well as analytic results.

Relation between hydration level and quality of steamed oat cakes: from the view of batter rheological properties

SummaryThe effects of hydration level on the rheological properties of oat batters and quality of steamed oat cakes were evaluated. With the increase in hydration level, the apparent viscosity was sharply decreased from 18.47 to 7.08 Pa⋅s, and the frequency sweep results suggested an increasing fraction of uncross‐linked component in oat batter. The water fluidity was enhanced, and the cross‐linking of proteins were weakened, resulting in loose batter structure. Apparent viscosity and microstructure analysis suggested that the gas chamber size was negatively correlated with the viscosity. Large gas chamber formed by low viscosity batter was unstable, resulting in steamed oat cakes collapsed. Besides, a highly viscous batter resulted in excessive cross‐linking and restricted gas expansion. Medium viscosity of oat batter, 15.28 Pa⋅s, with 110% water addition resulted in highest specific volume, cell area fraction and minimum hardness, 2.22 mL g−1, 34.73% and 7.61 N, respectively.

Multi‐stage flexible planning of regional electricity‐HCNG‐integrated energy system considering gas pipeline retrofit and expansion

The development of hydrogen-enriched compressed natural gas (HCNG) can make full use of the existing natural gas infrastructure, thereby alleviating the economic and technical pressure on the development of pure hydrogen. This paper proposes a multi-stage flexible planning method for the regional electricity-HCNG-integrated energy system (E-HCNG-IES), which considers the medium and long-term dynamic characteristics of the E-HCNG-IES. For each sub-regional energy station, an energy-hub type model including hydrogen/HCNG-related equipment and facilities is established. Considering the influence of hydrogen blending on the energy delivery capacity and line pack of pipelines, a hydrogen-resistant retrofit model for existing natural gas pipelines between sub-regions is proposed. Meanwhile, the model for newly constructed hydrogen pipelines is also presented. Subsequently, a series of flexibility evaluation indicators are proposed to support the performance analysis of planning schemes. The lateral comparison of sub-cases in Changzhou, China demonstrates that considering the hydrogen-resistant retrofit of natural gas pipelines can reduce the construction cost of hydrogen pipelines by about 37.12%. The peak shaving capacity of underground hydrogen storage (UHS), the energy recycling ability of turbo expander (TE), and the space-time decoupling ability of hydrogen in energy supply and demand have also been confirmed.