Effect Of Gas Content Research Articles

Effect of gas content on cavitation nuclei

Cavitation inception originates from nuclei in a liquid. This paper proposes a Gibbs free energy approach that provides a smooth transition from homogeneous to heterogeneous nucleation when gas is present. The impact of gas content on nucleation is explored. It is found that the gas content stabilises nuclei, a phenomenon not present in pure liquid–vapour systems. This reduces the energy barrier over that required to nucleate a vapour bubble. Different gas saturation levels are studied. Gas content can significantly reduce the energy barrier required for nucleation, and under certain circumstances eliminate it. An analytic solution for the critical radius and activation energy is obtained that accounts for gas content. The classical Blake radius is recovered as a limiting case. The hysteresis between incipience and desinence is explained using the asymmetry observed in the critical radii. The solution is used to obtain the initial bubble radius, given a critical pressure condition in cavitation susceptibility meter experiments. The relationship between initial bubble diameter and critical pressure is described by an analytic solution that accounts for gas content. A model for the derivative of the cumulative nuclei histogram with respect to bubble diameter is proposed. An analytic expression is obtained that shows good agreement with decades worth of experimental data compiled by Khoo et al. (Exp. Fluids, vol. 61, issue 2, 2020, pp. 1–20) from ocean to water tunnels. The expression recovers the $-4$ power law that is observed experimentally.

Effect of Gas Content on Mechanical behavior of Case Hardened Boron Steel

Boron containing steels are widely used in gear and shaft application. Addition of Boron to case hardened steel enhances hardenability resulting in good impact strength and wear resistant properties. In this present study, the influence of 100 and 150 PPM Nitrogen gas on Boron steel has been analyzed. The microstructure, hardenability, hardness, and impact strength has been evaluated. The Impact test was carried out as per standard and Fractography analysis has been done. Fine grain structure was observed in the higher Nitrogen content samples indicates better mechanical properties. The impact strength has been improved nearly 9% in the higher Nitrogen containing samples because of fine grain structure. Combination of intergranular with dimple mode of fracture was observed in the high Nitrogen containing samples.

Gas content of a liquid in threaded roughness recesses and its effect on heat and mass exchange

This paper proposes a mechanism of gas bubble formation in a down-flowing liquid film as a result of reduced pressure in circulation zones of threaded roughness recesses. Simulation modelling on the Comsol Multiphysics software was used to calculate circulation loops, liquid velocities, and pressure. Thus, the accepted of gas bubble formation was justifying. We experimentally determined gas content along film thickness and its average value, and proposed an equation for calculating gas content along liquid layer thickness. The effect of gas content on the average thickness of a liquid film, as well as its heat and mass transfer, was confirmed.

Effects of gas content and ambient temperature on combustion characteristics of methane hydrate spheres

Methane hydrate has the potential to become a high quality medium for gas storage and a special fuel because of its high efficiency for gas storage and its combustibility. It is important to study the factors that affect the combustion characteristics of methane hydrate. In this paper, the effects of gas content and ambient temperature on the combustion of methane hydrate spheres are investigated experimentally. The combustion flame of methane hydrate spheres with high gas content is bright yellow, whereas the combustion flame of methane hydrate spheres with low gas content is dim blue. With an increase in gas content, the methane hydrate sphere is easier to ignite and the combustion rate, residual gas content, flame height, flame oscillation frequency, and flame brightness all increase. However, the flame temperature at a height of 3 cm from the center of the sphere decreases. This is mainly because of the combustion of hydrate spheres with high gas content in a severe fuel excess state. The combustion characteristics of methane hydrate spheres in the ambient temperature range of 293 K–303 K are very similar. Also, the flame is bright yellow with insufficient combustion. With an increase in the ambient temperature, there are no differences in the residual gas content of methane hydrate spheres; the combustion rate, flame height, flame oscillation frequency, and flame brightness decrease slightly, and this is related to the self-preservation process. However, the flame temperature at a height of 6 cm from the center of the sphere increases. The increase in ambient temperature may have a similar effect with a decrease in gas content, and the root cause of this is that the slower release of methane is beneficial for mixing with the air in a better proportion. In addition, the combustion is more sufficient. The slower emission of combustion products also reduces the flow velocity, weakens the oscillation of the flame, and improves the stability of the flame.

Effect of gas content in the pumped liquid on the characteristics of a torque flow pump

The article considers one of the ways to increase the ability of a dynamic pump to pump gas-liquid mixtures - the application of the vortex principle of energy transfer. This scheme is embodied in a torque flow pump, which is able to pump mixtures with a gas content of up to 0,40 - 0,45 without additional devices for preparing the mixture. Experimental researches the influence the value of the volumetric gas content on the performance characteristics of the torque flow pump of the "Turo" type are given. The analysis of influence of structure of a stream of gas-liquid mixture on the value of the critical gas content in the interblade channels of the impeller is represented and developed a physical model of decrease the parameters of the torque flow pump.

Effect of gas content in macropores on hydraulic fracturing in rocks using a fully coupled DEM/CFD approach

AbstractThe paper focuses on the effect of the gas content in rock macropores on a hydraulic fracturing process. The process was simulated by combining the discrete element method (DEM) with computational fluid dynamics (CFD) under two‐dimensional (2D) isothermal conditions. The mechanical behavior of the rock matrix was simulated with DEM, and CFD was used for describing the behavior of laminar two‐phase fracturing fluid (liquid and gas) flow in pre‐existing and newly developed fractures. Geometry changes of pores and fractures in the rock matrix were precisely reproduced. Fully coupled hydro‐mechanical simulation tests were carried out with a rock segment of simplified particulate mesostructure under plane strain compression. The rock segment contained one or two injection slots. The effect of the initial gas‐phase content in macropores on the propagation of hydraulic fractures was estimated in numbers for different initial rock porosities. In addition, the influence of different pre‐existing discontinuities in the rock segment was studied. The main characteristics of a fractured rock segment due to a high‐pressure fluid injection were realistically reproduced with a proposed approach. The initial gas‐phase fraction in macropores and pre‐existing discontinuities were found to be strongly influential in the course of hydraulic fracturing.

The calculation of multiphase flows in flowing parts of centrifugal pump

The effect of gas content on the changing of head of a centrifugal pump is researched. The method of numerical hydrodynamic modeling is used for solving this problem. The using mathematical models are described and compared. The results of the simulation of fluid flow, which are depended on the air content, are presented. The data on the changing of head and the termination of its work are obtained.

Experimental study on a swirl-vane separator for gas–liquid separation

Experimental research on a swirl-vane gas–liquid separator has been conducted with the aim to explore its application in downhole gas–water separation systems. With the help of a high-speed camera, the effect of gas content, Reynolds number and flow conditioning elements on the separation performance were investigated. The change of flow pattern will lead to the oscillation of air core inside the separator, which has significant influence on the separation performance. Experimental results show that both the increase of Reynolds number and the arranging of flow conditioning elements can only restrain the oscillation of air core to a certain degree. In addition, according to the evolution of air core, the flow pattern can be divided into: rod air core flow, tadpole-shaped air core flow, oscillating air core flow and swirling annular flow. Compared with the gas–liquid flow pattern map in vertical tube with the same inner diameter, it can be found that the flow pattern of gas–liquid mixture before entering the separator has significant influence on the state of the air core. In the end, the operational envelope limits of the separator were determined experimentally. Due to the effect of flow pattern, the separator is more suitable to be operated at low gas content. This research leads to a better understanding of hydraulic characteristics in this kind of separator.

Analysis of Reverse Currents Parameters and Gas Content in Liquid behind the Roughness Ridge

Based on experimental studies, the effect of gas content in the liquid behind the ridges of artificial helical roughness on film thickness and the value of the heat transfer coefficient is shown. The numerical results for the reverse currents velocity distribution and pressure difference along the ridge height and the cavity length, as well as experimental values of gas content in the liquid separation zone, arising from the flow over a regular roughness, are presented. The scale of reverse currents, their location behind the roughness ridge, and gas content depend on the height and shape of the ridge, the irrigation density, and the physical properties of the liquid. It was concluded that the gas bubbles in the liquid form in reverse current zones in the cavities of the artificial roughness due to reduced pressure compared to gas pressure at the interface and, therefore, gas suction from the interface zone. The dependence for calculating gas content via the thickness of the liquid layer in the roughness cavity is proposed.

Still Need to Study Cavitation

Cavitation is a well-known phase change phenomenon which causes various problems in hydraulic machinery such as performance deterioration, unsteady flow phenomena, erosion and so on. Many studies have been devoted for deeper understanding of this phenomenon, but the accurate prediction of the phenomenon in complex flow field of actual hydraulic machines is still very difficult. The effect of dissolved gas in working liquid is not well understood yet, which is one of the reasons for this difficulty. In this report, recent research activities of our research group on the effect of gas content on various types of cavitation will be briefly introduced.

Effect of Gas Content and Treatment Temperature on the Characteristic of Surface Layers of Low Temperature Plasma Nitrided 316L Austenitic Stainless Steel

The effect of gas content and treatment temperature on the surface characteristics of hardened layers of low temperature plasma nitrided 316L Austenitic Stainless Steel was investigated. The process was performed at fixed processing time at 15Hr and changing the N2 content from 10% to 25%, changing the treatment temperature from 370 °C to 430 °C. The surface hardness and the thickness of expanded austenite (S-Phase) layer increase with increasing both temperature and nitrogen content. At 430°C processing temperature and 25% N2 content, the S-phase layer thickness increased up to 13 μm and surface hardness increased about 3.5 times of that of untreated sample which is 880 HV0.1 (before treatment 250HV0.1 hardness). However, the XRD pattern of the this sample shows the presence of γ'-(Fe,Cr)4N precipitation on the surface which is the reason for the increased corrosion current density that results in increased corrosion rate. Thus the corrosion resistance degrades and presents even worst behavior comparing that of before treatment. Therefore, for increasing the corrosion behavior, further research was conducted by fixing the N2 content at 10% with changing the CH4 content from 0% to 5%. The best results were found when treated at 430°C with 5% CH4 content. At this condition the S-phase thickness increase to around 17μm and surface hardness (980 HV0.1) is improved about 3.9 times of the hardness of untreated one. This sample also showed superior corrosion resistance than the other treated samples and the untreated one due to much higher pitting potential.

Effects of Gas Content and Heat Input on Welding Strength between Aluminum Alloy Die Casting and Aluminum Alloy Sheet

Effects of Gas Content and Heat Input on Welding Strength between Aluminum Alloy Die Casting and Aluminum Alloy Sheet

Analysis of rock physics response of gas-bearing volcanic reservoir based on three-phase poroelastic theory

Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fluids in saturated porous media. Considering reservoir reference pressure and coupling drag of two fluids in pores, the effects of frequency, porosity, and gas saturation on the phase velocities of the P- and S-waves are discussed in detail under field conditions. The effects of porosity and gas saturation on Vp/Vs are also provided. The data for our numerical experiments are from a sample of deep volcanic rock from Daqing. The numerical results show that the frequency dispersion effect can be ignored for deep volcanic rocks with low porosity and low permeability. It is concluded that for deep volcanic rocks the effect of gas content in pores on Vp/Vs is negligible but the effect of porosity is significant when there is a certain amount of water contained in the pores. The accurate estimate of lithology and porosity in this case is relatively more important.

EFFECT OF GAS CONTENT ON THE OSCILLATION OF A LASER-INDUCED CAVITATION BUBBLE

The oscillation of a cavitation bubble and the effect of gas content inside a cavity on the bubble motion are investigated by theory and experiment. Based on the cavitation model, the numerical study yields the gas content dependence of the amplitude and duration of the bubble oscillation in liquids. In experiment, the temporal oscillation of a single laser-induced cavitation bubble is obtained by means of a sensitive fiber-optic sensor based on optical beam deflection. The characteristic bubble parameters are determined, including the maximum (minimum) radii, oscillation duration and bubble energy, which all decrease with the oscillation. Besides, combining the cavitation theory with experimental data, the variation of gas content within the bubble during each oscillation is estimated, which increases with the oscillation cycle. Our results reveal the competitive interplay of the bubble energy and gas content during the bubble motion and the bubble energy in effect outweighs the latter.

Ultrasonic inactivation of Bacillus α-amylase. I. effect of gas content and emitting face of probe

Sonoinactivation of α-amylase from Bacillus amyloliquefacience was studied at a constant frequency of 30 kHz. The effect of sonotrode emitting face and gas content of medium on the efficiency of enzyme inactivation were investigated at different time–temperature combinations and generation of OH free radicals was also monitored. The results showed that ultrasound effectively inactivated α-amylase with a minimum overall inactivation rate at 50 °C. The tip diameter of the sonotrode and the gas content of the medium both significantly affected the rate of enzyme inactivation. The increase of tip diameter increased the effect of ultrasound on the enzyme, while the removal of dissolved gas adversely influenced the cavitational events and reduced the rate of enzyme inactivation. Calculation of the kinetic and activation parameters revealed that ultrasound decreased the activation energy, E a, activation enthalpy, Δ H #, and the activation Gibbs free energy, Δ G #, and strongly reduced the activation entropy, Δ S #, down to negative values. This huge reduction in activation entropy was attributed to the different mechanisms of inactivation induced by heat and ultrasound. It is proved in this study that ultrasonically generated OH free radicals and shear forces, which arise from pulsation- or collapse of bubbles, both can destabilize the enzyme, although their contribution to the overall inactivation varies depending on the temperature and the tip diameter of the sonotrode.

Effects of Gas Content in Fluid on Oscillating Frequencies of Self-Excited Oscillation Water Jets

Effects of Gas Content in Fluid on Oscillating Frequencies of Self-Excited Oscillation Water Jets

The Effect of Oil and Gas Content on the Controllability and Separation in a De-Oiling Hydrocyclone

The effect of free gas on cyclonic oil–water separation was examined using a geometry which sought to minimize problems with gas. Tests were carried out using the purpose built oil–water separation facility at Bradford University where pre-choke conditions could be partially simulated. Firstly, tests were carried out with water and gas–water to look at flow behaviour and control parameters, then comparative separation tests carried out with gas–oil–water. Comparisons were also made with test data from a conventional de-oiling hydrocyclone. The effects of gas content, feed drop size distribution, overflow size diameter and feed pressure were all investigated. A threshold effect of free gas on flow stability and separation efficiency was observed. The see-through hydrocyclone allowed the collection of semiquantitative data on gas core diameter and behaviour and on gas slip velocity at inlet.

Supercritical antisolvent fractionation: measurements in the systems monodisperse and bidisperse polystyrene [sbnd]cyclohexane [sbnd]carbon dioxide

As a model system for new polymer-separation processes utilizing compressed gases the system polystyrenecyclohexanecarbon dioxide with monodisperse polymers (Mw/Mn = 1.09) was investigated experimentally at temperatures up to 250°C and pressures up to 160 bar. Small amounts of carbon dioxide shift the lower critical solution temperature (LCST) to dramatically lower temperatures. When looking at the pressure-concentration representation there is a striking similarity between the effect of temperature and the effect of gas content on the shape of the two-phase region. Pressure has a pronounced effect on the chain partitioning of polystyrenes of different molecular weights in the two liquid phases as determined by gel permeation chromatography. The results are discussed in the context of industrial application.

Etude de la formation des cavités dans le cuivre irradie aux ions cuivre de 500 keV

We have studied the formation of voids in thin foils of copper irradiated by 500 keV Cu + ions, as a function of temperature, irradiation intensity and the dissolved gas content of the samples. A theoretical examination of the phenomena gives a good account of the effects of temperature, the rate of defect creation and the foil thickness, but it fails to account for the fact that at 400° C voids are formed for a dose of 3 × 10 −4 dpa/s but not for 3 × 10 −3 dpa/s. This is tentatively explained in terms of the influence of the gas content. The effect of gas content on the formation of voids and dislocation loops has moreover been demonstrated by degassing thin foils by annealing in ultrahigh vacuum, or by implanting helium before irradiation.

Effects of gas content upon cavitation inception, performance, and damage (Summary Report for Working Group No. 1 of Section for Hydraulic Machinery, Equipment and Cavitation of IAHR)

Effects of gas content upon cavitation inception, performance, and damage (Summary Report for Working Group No. 1 of Section for Hydraulic Machinery, Equipment and Cavitation of IAHR)