Mixture Of Helium Research Articles

Separation of He/N2/CH4 ternary mixtures by a triple‐reflux pressure swing adsorption process

AbstractConventional pressure swing adsorption (PSA) processes can only produce one high purity product in a single stage, whereas the state‐of‐art dual‐reflux PSA (DR‐PSA) can produce two high purity products simultaneously. However, multicomponent gas separation is often required in the industry, targeting at recovering several valued products at the same time. In this study, we propose a novel adsorption process, namely triple‐reflux PSA (TR‐PSA), to separate three components simultaneously. A middle product outlet and a middle reflux stream were introduced to the adsorption columns of a conventional DR‐PSA process to separate ternary mixtures of nitrogen, methane, and helium. Nonisothermal dynamic models were built to investigate the impacts of operating parameters particularly the location of the middle reflux/product stream and the middle reflux flow rates. Results showed that the TR‐PSA process successfully separated ternary mixtures obtaining three enriched products simultaneously in a single stage, yielding a separation performance comparable to that of the double‐stage DR‐PSA with significantly lower capital and energy cost.

Experiment and modeling of the pulsed lasing in a diode-pumped argon metastable laser

Diode-pumped metastable rare gas lasers are showing their potential for high-energy laser systems with intensive investigations carried out to understand their lasing characteristics. Here, we demonstrated pulsed lasing of a diode-pumped argon metastable laser based on a pulsed DC glow discharge in argon and helium mixtures for different discharge voltages and pressures. A transient rate equation model was established and solved to explain the cause of the pulsed lasing in our experiment. The insufficient production rate of argon metastable atoms (1s5) and the slow transfer rate out of the 1s4 state in the plasma during the lasing process were found to be the key reasons. This work may shed some light on the future design of plasma sources that have higher metastable atom production rates to achieve highly efficient continuous wave lasing.

Properties of welded aluminum 1915T joints made by laser welding

The results of experimental studies of the mechanical properties and structure of welded joints of aluminum 1915T alloy sheets obtained under various modes of laser welding are presented. The use of a fiber laser for welding increases the efficiency of the process. The use of filler wire in laser welding allows to adjust the composition of the weld metal and it’s structure, reduce the requirements for assembling the joint for welding and increase the mechanical properties of the joints. Welded joints of 1915T alloy with a strength coefficient of 0.83 are obtained when protecting the welding pool in the welding process with a mixture of argon and helium and using filler SvAMg63 wire with a diameter of 0.8 mm. The decisive effect of the method for preparing of the surface of blanks for welding on the presence of pores in the weld metal is shown.

Experiments with rectangular supersonic jets with potential noise reduction technology.

This paper describes the aeroacoustics experiments conducted with supersonic jets, exhausting from rectangular nozzles with an aspect ratio of 2, to examine the jet noise reduction by two different methods. The first method involves the use of fluid inserts, which are produced by distributed air blowing into the diverging section of a convergent-divergent exhaust nozzle. The second method involves the integration of fluid shields in dual flow rectangular jets. In the dual flow nozzle, a single shield below the exit is augmented with fluid shields extending on both sides of the rectangular jet. The purpose of the extended bypass flow is to reduce the noise radiated to the sides of a jet aircraft. In addition to the nozzles with the two noise reduction configurations, acoustic measurements are performed with a single flow rectangular jet, referred to as the baseline. In all cases, the jets are operated as overexpanded, shock-containing jets. In some cases, the jets are operated with the core flow mixtures of helium and air to simulate high temperature jets. The far-field noise measurements are performed on an arc with the microphones approximately 70 equivalent nozzle diameters from the nozzle exit. For the purposes of assessing the noise reduction capability of the dual stream jet, comparisons are made with a baseline rectangular jet on an equal thrust per unit exit area basis. The nondimensional acoustic spectra and overall sound pressure level directivities are shown and compared.

Лечение больных с симптомами нижних мочевых путей и эректильной дисфункции после трансуретральных операций на предстательной железе

Objective: to assess the clinical utility of a comprehensive multimodal treatment including phosphodiesterase type 5 (PDE5) inhibitors + extracorporeal shockwave therapy (ESWT) + inhalations with a heated mixture of helium and oxygen (Thermogeliox technology) in patients with urination disorders and erectile dysfunction that had undergone transurethral surgery for benign prostatic hyperplasia (BPH). Patients and methods. This prospective single-blind randomized study was conducted at the Medical Research and Educational Center, M.V.Lomonosov Moscow State University and included 60 patients aged 50 to 80 years that were randomly assigned to one of the two groups matched for the main characteristics. Patients in the experimental group received basic pharmacotherapy (tamsulosin 0.4 mg and tadalafil 5 mg daily) plus courses of anti-ischemic treatment (10 procedures in each course; two procedures per week). The anti-ischemic treatment included ESWT using the Dornier MedTech ARIES device (Germany) and oxygen-helium therapy using the BreezeLite device (InertGaz medical, Russia). Arterial blood flow in the peripheral prostate was assessed using the rectal probe of the Philips EPIQ 7 ultrasound scanner (USA); peak systolic velocity (Vps, cm/sec) and the arterial resistance index (RI) were measured in the right and left prostatic arteries. The severity of the disease was evaluated by assessing both subjective (International Prostate Symptom Score (IPSS), International Index of Erectile Function (IIEF)) and objective parameters (frequency and quality of nocturnal penile tumescences using the Androscan MIT recorder and maximum urine flow at uroflowmetry). Data analysis was conducted using the Statistica 10 software; differences were considered significant at р < 0.05. Results. Patients in both groups reported a significant improvement of their condition (both IPSS and IIEF scores decreased) and maximum urine flow. Treatment also improved arterial blood flow in the peripheral prostate in both groups: in the experimental group, Vps increased from 7.95 ± 0.12 cm/sec to 14.05 ± 0.16 cm/sec; in the control group, Vps increased from 8.07 ± 0.11 cm/sec to 11.42 ± 0.17 cm/sec. Patients in the experimental group had a more pronounced treatment effect 3 months after its completion (13.01 ± 0.20 cm/sec vs 10.40 ± 0.20 cm/sec; p < 0.05). Erectile function (IIEF and androscan) was restored in 10 patients (33.3%) from the experimental group and 5 patients (16.7%) from the control group. The ratios of patients with ED of varying severity also changed: in the experimental group, the number of patients with grade I disease increased to 14 (46.7%), while the number of patients with grade II and grade III disease decreased to 5 (16.67%) and 1 (3.3%), respectively. In the control group, these numbers were 13 (43,3%), 9 (30%), and 3 (10%), respectively. Conclusion. Patients may develop prostatic ischemia in the late postoperative period due to infravesical obstruction and concomitant diseases. Further development of treatment techniques aimed to prevent the consequences of such ischemia will reduce the incidence of complications, improve the outcomes of transurethral surgeries for BPH, and significantly improve the quality of life of patients.

Double phase transition numerical modeling of superfluid helium for fixed non-uniform grids

A thermo-fluid dynamic numerical model for the simulation of the first-order and second-order phase transitions in superfluid helium (He II) is presented. The model is based on a Finite Volume Method algorithm for transient multidimensional problems. The method is also intended to simulate the conjugate heat transfer between helium and solids, which required the implementation of customized boundary conditions to replicate the Kapitza resistance and superfluid partial slip. The implemented governing equations for He II constitute an advanced version of an existing single-fluid model, which is herein newly derived with a more generalized conductive heat power law. The vapor-He I phase change is addressed through an explicit calculation of the volume fractions of the helium mixture and by introducing surface tension forces. An algorithm for fixed non-uniform orthogonal grids is conceptualized to deal with the lambda transition. The model is validated against data collected during clamped heat flux experiments in a rectangular cross-section channel of a high aspect ratio. The experiments were conducted both above and below the lambda temperature at atmospheric pressure with the channel in horizontal and vertical positions. The comparison with the data showed satisfactory agreement in the temperature profiles.

Optimization of a recompression supercritical nitrous oxide and helium Brayton cycle for space nuclear system

Long life, high energy density, high efficiency, and compact power system is necessary for space exploration to achieve a future goal. Recompression supercritical Brayton cycle has excellent potential for application of space nuclear power generation systems. However, it faces the choice of cycle working fluid which limits the cycle thermal efficiency and quality. In order to improve the thermal efficiency of the nuclear power system, a new composition of the working fluid, nitrous oxide and helium (N2O–He) mixture is used in the system. Comprehensive studies and optimization are performed for the significant parameters, including the split ratio, pressure ratio, minimum operating temperature, maximum operating temperature, and minimum operating pressure. Optimum values have been obtained at which the maximum thermal efficiency and minimum Brayton rotating unit (BRU) mass of the cycle occur. Results show that the thermal efficiency improves with an increase in the split ratio, main compressor pressure ratio, and maximum operating temperature, and decreasing minimum operating temperature and minimum operating pressure. The proposed novel working fluid cycle has superior performance compared with N2O (deviation of 5.1%) and CO2 (deviation of 6.5%). The optimized thermal efficiency and BRU mass are calculated as 42.67% and 3584.80 kg at optimum conditions.

First 3D vector tracking of helium recoils for fast neutron measurements at SuperKEKB

We present results from the first deployment of novel, high definition, compact gas Time Projection Chambers (TPCs) with pixel chip readout as part of the BEAST II beam background measurement project at SuperKEKB. The TPCs provide detailed 3D imaging of ionization from neutron-induced nuclear recoils in a helium and carbon dioxide target gas mixture at standard temperature and pressure. We present the TPC performance and the neutron backgrounds observed during the initial stage of collider commissioning. We find excellent electron background rejection, leading to background-free nuclear recoil measurements above 50 keVee, despite the extreme high-background environment. We measure an angular resolution better than 20° for recoil tracks longer than 1.7 mm, corresponding to an average ionization energy of approximately 100 keVee. We also obtain the full 3D vector direction of helium recoils by utilizing charge profile measurements along the recoil axis, with a correct head/tail assignment efficiency of approximately 80%. With this performance, we present comparisons between measured and simulated event rates, recoil energy spectra, and directional distributions originating from beam–gas and Touschek beam losses at SuperKEKB. We utilize head/tail recognition to distinguish neutron components traveling with positive radial velocity in the Belle II coordinate system from those traveling in the opposite direction. Finally, we present a novel method of discriminating beam–gas interactions from Touschek beam losses that can eliminate the need for dedicated accelerator runs for background measurements. This method is still statistics-limited. However, future studies should be able to verify this method, which in turn could lead to neutron background analysis runs symbiotic with normal Belle II operation. The capabilities demonstrated here also suggest that high definition recoil imaging in gas TPCs is applicable to low energy, low-background experiments, such as directional dark matter searches.

The effects of impurity gas seeding on the growth of fuzzy tungsten

Using the linear plasma device NAGDIS-II operating with gas mixtures of helium (He) and impurity (Ne, N 2 , Ar), fibre-form nanostructures known as “fuzz” have been grown on tungsten (W) samples. In this system, fuzzy W was grown over a range of sample temperatures and ion fluences (containing He and impurity ion mixtures), but with operator control over the impurity to helium percentage (from 5 – 10%). The ion energies were held constant at 60 eV throughout the experiments. Close inspection of the surface morphologies showed that a variation in fuzzy structure was produced on W surfaces depending on the impurity species used. Specifically, Ne impurity produced cone-like fuzz structures and Ar and N 2 caused more random tendril growth. Using a constant fluence of He and impurity ion species, the effective fuzzy layer growth rate is reduced for higher impurity atomic masses and higher concentrations. For 10 % N 2 within the He plasma, little fuzz growth was visible on the W surface. Where 7.5 – 10% of Ar was used, fuzz growth was terminated completely. From mass loss measurements the net erosion yields of W surfaces exposed to 95 % He + 5% impurity (Ne or N 2 ) discharges were measured to be lower than bulk W sputtering yields for each impurity species, decreasing sharply with increasing fuzz thickness. Under high ion fluences up to 10 27 m − 2 , steady-state thicknesses of W fuzz were attained due to the combined effect of fuzz growth and sputter erosion caused by the impurity species in the plasma. The measured steady-state thicknesses were found to be consistent with an analytical model developed for the simultaneous growth and erosion of fuzz. SEM imaging showed the presence of larger fuzzy structures, Nano-tendril bundles (NTBs), on surfaces where fuzz grew under the presence of impurity species. The formation of NTBs were characterised in terms of their surface temperature threshold ranges.

Simultaneously improving the resolving power and sensitivity for planar high-field asymmetric waveform ion mobility spectrometry using a mixed gas inlet mode at two ends.

Resolution and sensitivity are two key parameters for describing the performance of high-field asymmetric waveform ion mobility spectrometry (FAIMS). An increase in the resolving power of FAIMS has been realized by adding helium to nitrogen in planar FAIMS, but it comes at the expense of sensitivity. Here, a new hollow needle-to-ring discharge device integrated on a PCB substrate is used as the ion source for FAIMS. Helium flows from the hollow part of the hollow needle to improve the ionization effect. Nitrogen carries the sample into the ionization chamber and is mixed with helium as the carrier gas. Under a nitrogen flow rate of 1L min-1 , 1.5L min-1 , 2L min-1 , and 2.5L min-1 , adding helium at different flow rates (0.2L min-1 , 0.3L min-1 , 0.5L min-1 , and 1L min-1 ) can simultaneously improve the separation ability and sensitivity. Helium and nitrogen with flow rates of 0.2, 0.3, 0.5, and 1L min-1 were added to nitrogen (2L min-1 ). The separation ability and sensitivity of the mixed gases doped with helium are better than those of nitrogen. The larger the RF voltage amplitude is, the more obvious the improvement in the separation ability when helium is added. However, helium doping has the opposite effect on the sensitivity. This study provides a new idea and technical means for the application of helium and nitrogen gas mixtures in planar FAIMS. This method can greatly improve the performance of FAIMS.

Experimental investigations on steam-air-hydrogen condensation and corresponding component separation phenomenon

Under severe accident conditions of a pressurized water reactor, hydrogen will be released into the containment, forming a mixture of steam-air-hydrogen, and then transported to the surroundings. This process can be coupled with complex mass transfer behavior caused by wall condensation. Under the coupling effect of condensation and buoyancy introduced by hydrogen, the mixture gas will form different types of transport behaviors. This will be closely related to the stratification and flammability risk of high-concentration hydrogen. To quantitatively determine these phenomena and assess the potential causing reasons, experiments were performed with helium instead of hydrogen based on the COAST (condensation and species transport) facility. The tests cover a broad parameter range with steam concentrations of 8.4– 89%, helium concentrations of 10– 66% (XHe/XNon), and pressures of 0.4– 1.3 MPa. The phenomena of steam condensation induced component separation were firstly confirmed in the tests, and the component concentration threshold was clarified at XHe/XNon = 50%. The three flow patterns of steam-air- helium mixture gas was identified by Shapiro-Moffette ternary diagram. Moreover, the temperature inverse stratification caused by the high-concentration helium-air layer was discovered in the experiments, and its influence on heat transfer was clarified.

Molecular simulation of Rayleigh-Brillouin scattering in binary gas mixtures and extraction of the rotational relaxation numbers.

Rayleigh-Brillouin scattering (RBS) in gases has received considerable attention due to its applications in LIDAR (light detection and ranging) remote sensing and gas property measurements. In most cases, the RBS spectra in the kinetic regime are calculated based on kinetic model equations, which are difficult to be applied to complex gas mixtures. In this work, we employ two widely used molecular simulation methods, i.e., direct simulation Monte Carlo (DSMC) and molecular dynamics (MD), to calculate the spontaneous RBS spectra of binary gas mixtures. We validate these two methods by comparing the simulation results for mixtures of argon and helium with the experimental results. Then we extend the RBS calculations to gas mixtures involving polyatomic gases. The rotational relaxation numbers specific to each species pair in DSMC are determined by fitting the DSMC spectra to the MD spectra. Our results show that all the rotational relaxation numbers for air composed of N_{2} and O_{2} increase with temperature in the range of 300-750 K. We further calculate the RBS spectra for binary mixtures composed of N_{2} and one noble monatomic gas, and the simulation results show that the rotational relaxation of N_{2} is greatly affected by the mass of the noble gas atoms. This work demonstrates that RBS is a promising and alternative way to study the rotational relaxation process in gas mixtures.

Numerical Analysis of the Interactions between Plasma Jet and Powder Particles in PS-PVD Conditions

Plasma spray-physical vapor deposition (PS-PVD) refers to a very low-pressure (~100 Pa) deposition process in which a powder is injected in a high-enthalpy plasma jet, and mostly vaporized and recondensed onto a substrate to form a coating with a specific microstructure (e.g., columnar). A key issue is the selection of the powder particle size that could be evaporated under specific spray conditions. Powder evaporation takes place, first, in the plasma torch between the injection location and nozzle exit and, then, in the deposition chamber from the nozzle exit to the substrate location. This work aims to calculate the size of the particles that can be evaporated in both stages of the process. It deals with an yttria-stabilized zirconia powder and two commercial plasma torches operated at different arc powers with gas mixtures of argon and helium or argon and hydrogen. First, it used computational fluid dynamics simulations to calculate the velocity and temperature fields of the plasma jets under very low-pressure plasma conditions. Then, it estimated the evaporation of the particles injected in both plasma jets assuming an isothermal evaporation process coupled with momentum and heat transfer plasma-particle models in a rarefied plasma. The calculations showed that, for different powers of the Ar–H2 and the Ar–He operating conditions of this study, the heat flux from the plasma jet to particles inside the torch is much higher than that transferred in the deposition chamber while the specific enthalpy transferred to particles is comparable. The argon-helium mixture is more efficient than the argon-hydrogen mixture to evaporate the particles. Particles less than 2 μm in diameter could be fully evaporated in the Ar–He plasma jet while they should be less than 1 µm in diameter in the Ar–H2 plasma jet.

Physiological effects of mixed-gas deep sea dives using a closed-circuit rebreather: a field pilot study.

Deep diving using mixed gas with closed-circuit rebreathers (CCRs) is increasingly common. However, data regarding the effects of these dives are still scarce. This preliminary field study aimed at evaluating the acute effects of deep (90-120msw) mixed-gas CCR bounce dives on lung function in relation with other physiological parameters. Seven divers performed a total of sixteen open-sea CCR dives breathing gas mixture of helium, nitrogen and oxygen (trimix) within four days at 2 depths (90 and 120msw). Spirometric parameters, SpO2, body mass, hematocrit, short term heart rate variability (HRV) and critical flicker fusion frequency (CFFF) were measured at rest 60min before the dive and 120min after surfacing. The median [1st-3rd quartile] of the forced vital capacity was lower (84% [76-93] vs 91% [74-107] of predicted values; p = 0.029), whereas FEV1/FVC was higher (98% [95-99] vs 95% [89-99]; p = 0.019) after than before the dives. The other spirometry values and SpO2 were unchanged. Body mass decreased from 73.5kg (72.0-89.6) before the dives to 70.0kg (69.2-85.8) after surfacing (p = 0.001), with no change of hematocrit or CFFT. HRV was increased as indicated by the higher SDNN, RMSSD and pNN50 after than before dives. The present observation represents the first original data regarding the effects of deep repeated CCR dives. The body mass loss and decrease of FVC after bounce dives at depth of about 100msw may possibly impose an important physiological stress for the divers.

Heliox for croup in children.

Heliox for croup in children.

Ventilation heterogeneity imaged by multibreath wash-ins of hyperpolarized 3 He and 129 Xe in healthy rabbits.

Multibreath imaging to estimate regional gas mixing efficiency is superior to intensity-based single-breath ventilation markers, as it is capable of revealing minute but essential measures of ventilation heterogeneity which may be sensitive to subclinical alterations in the early stages of both obstructive and restrictive respiratory disorders. Large-scale convective stratification of ventilation in central-to-peripheral directions is the dominant feature of observed ventilation heterogeneity when imaging a heavy/less diffusive xenon gas mixture; smaller-scale patchiness, probably originating from asymmetric lung function at bronchial airway branching due to the interaction of convective and diffusive flows, is the dominant feature when imaging a lighter/more diffusive helium gas mixture. Since detecting low regional ventilation is crucial for characterizing diseased lungs, our results suggest that dilution with natural abundance helium and imaging at higher lung volumes seem advisable when imaging with hyperpolarized 129 Xe; this will allow the imaging gas to reach slow-filling and/or non-dependent lung regions, which might otherwise be impossible to distinguish from total ventilation shunt regions. The ability to differentiate these regions from those of total shunt is worse with typical single-breath imaging techniques. The mixing of freshly inhaled gas with gas already present in the lung can be directly assessed with heretofore unachievable precision via magnetic resonance imaging of signal build-up resulting from multiple wash-ins of a hyperpolarized (HP) gas. Here, we used normoxic HP 3 He and 129 Xe mixtures to study regional ventilation at different spatial scales in five healthy mechanically ventilated supine rabbits at two different inspired volumes. To decouple the respective effects of density and diffusion rates on ventilation heterogeneity, two additional studies were performed: one in which 3 He was diluted with an equal fraction of natural abundance xenon, and one in which 129 Xe was diluted with an equal fraction of 4 He. We observed systematic differences in the spatial scale of specific ventilation heterogeneity between HP 3 He and 129 Xe. We found that large-scale, central-to-peripheral convective ventilation inhomogeneity is the dominant cause of observed heterogeneity when breathing a normoxic xenon gas mixture. In contrast, small-scale ventilation heterogeneity in the form of patchiness, probably originating from asymmetric lung function at bronchial airway branching due to interactions between convective and diffusive flows, is the dominant feature when breathing a normoxic helium gas mixture, for which the critical zone occurs more proximally and at an imageable spatial scale. We also showed that the existence of particular underventilated non-dependent lung regions when breathing a heavy gas mixture is the result of the density of that mixture - rather than, for example, its diffusion rate or viscosity. Finally, we showed that gravity-dependent ventilation heterogeneity becomes substantially more uniform at higher inspired volumes for xenon gas mixtures compared to helium mixtures.

Separation of a binary gas mixture outflowing into vacuum through a micronozzle

The present paper studies the separation phenomenon for argon–helium mixture outflowing through a convergent–divergent micronozzle into a vacuum. We numerically investigate the effect of the geometrical parameters of the micronozzle and gas rarefaction (Knudsen number is varied in range ≈0.01−100). Simulations were performed using the event-driven molecular dynamics method. Performed analysis revealed several interesting and important features of the separation process. First, it was shown that separation in the present problem results mainly from a lateral component, which appears when significant curvature of gas streamlines is present. Second, it was demonstrated how the fine-tuning of micronozzle geometry can enhance separation efficiency. At the same time, the simplest microslit arrangement (a microchannel without converging and diverging parts) was shown to provide results comparable to micronozzles and may be preferable due to its manufacturing simplicity. Then, it was shown that the position of the product gas selector is crucial for effective separation and its proper placement brings more influence than the geometry of the micronozzle itself. Finally, it was shown that maximal purity of product gas can be obtained in a peripheral area in transitional and slip flow regimes inside the micronozzle. Therefore, for effective separation, there is no need to achieve high rarefaction levels inside the micronozzle.

A New Equation of State for Dense Hydrogen–Helium Mixtures. II. Taking into Account Hydrogen–Helium Interactions

Abstract In a recent paper, we derived a new equation of state (EOS) for dense hydrogen/helium mixtures that covers the temperature–density domain from solar-type stars to brown dwarfs and gaseous planets. This EOS is based on the so-called additive volume law and thus does not take into account the interactions between the hydrogen and helium species. In the present paper, we go beyond these calculations by taking into account H/He interactions, derived from quantum molecular dynamics simulations. These interactions, which eventually lead to H/He phase separation, become important at low temperature and high density, in the domain of brown dwarfs and giant planets. The tables of this new EOS are made publicly available.

Reduction of incandescent spatter with helium addition to the process gas during laser powder bed fusion of Ti-6Al-4V

The effect of the process gas during laser powder bed fusion (L-PBF) was investigated using high-speed shadowgraphy while melting Ti-6Al-4V powder under high purity argon, helium, and a mixture of both, on a laboratory-scale machine. These recordings reveal that the generation of incandescent spatters can be reduced by at least 60% using pure helium and by ∼30% using addition of helium to argon in comparison to the use of traditional argon. The quantity of colder spatters appeared unaffected by the change of process gas. Different configurations of gas flow versus laser scanning direction were investigated and revealed that fumes and spatters are less accumulated at the laser spot with helium addition. Furthermore, the use of the argon–helium mixture proved to be as efficient as pure argon in the dragging and extraction of the fumes. Shadowgraphs revealed the more rapid expansion of fumes in helium-rich atmospheres, limiting the accumulation of scattering objects close to the laser spot and thus melt pool instability. These results were correlated to process snapshots on an industrial-scale system, confirming the reduction of hot spatter generation. Finally, the findings put in evidence the more rapid cooling of spatters with helium addition to the process gas – a promising aspect to limit powder bed degradation during L-PBF. In addition, the use of mixtures of helium and argon would be economically interesting compared to pure helium, typically more expensive than the traditionally used argon.

Pulsating and cellular instabilities of hydrogen–oxygen detonations with ozone sensitization

Numerical simulations have been conducted to investigate the effects of ozone (O3) sensitization on pulsating and cellular instabilities of one- and two-dimensional (1-, 2D) detonations in hydrogen–oxygen–helium (H2/O2/He) mixture with and without O3 addition. The predictions have been analyzed to illustrate the different modes of 1D detonation in H2/O2/He mixtures and its thermal sensitivity to the varying distributions of the heat release rate due to He dilution. The results are further analyzed to gain insight about the effect of O3 addition on the induction length, propagating mode of 1D detonation and its stability. Finally, the role of O3 sensitization on cellular detonation in the 2D simulations is analyzed in terms of its effect on the detonation cell size, induction length, and detonation instabilities. The results indicate considerable potential of O3 sensitization to reduce the existence of unburnt pockets, reduce cell size, and increase detonation stability.