Ghasem G. Nasr

A new fine spray, low flowrate, spill-return swirl atomizer

A novel high liquid pressure fine spray swirl atomizer has been developed, which incorporates a spill-return orifice into the rear face of the swirl chamber with the aim of giving a significant reduction in flowrate while maintaining the droplet size. The initial work modified a commercial atomizer to add spill return. However, drop sizes were considered to be too large and a new design was constructed based on an earlier work on efficient high-pressure (up to 120 bar) swirl atomization. The resulting fine sprays can be used for various applications such as humidification, cleaning, coating, cooling, and decontamination. The atomizer has been characterized for different geometries, supply pressures, and spill-return orifice sizes using a Laser Particle Sizer and Phase Doppler Anemometry. For an exit orifice of 0.3mm diameter and spill orifice 0.5mm diameter, the drop size (Sauter mean diameter) is less than 20m for flowrates as low as 0.1litre/min and with a mean axial drop velocity of approximately 12m/s. An average liquid volume flux of 0.014(cm3/s)/cm2 is obtained in the spray at 150mm downstream.

The utilisation of fine sprays for Chemical, Biological, and Radiological or Nuclear (CBRN) Decontamination

The risk of exposure to hazardous materials, in many industrial environments and in everyday life due to the possibility of terrorist attacks, is widely recognised. It is therefore pertinent to have robust decontamination equipment to limit the effects of hazardous materials and in turn protect human life and assets. This can be done by the application of neutralisation (coverage) and rinsing techniques to the hazardous materials. The overall aim of this paper is to describe an investigation utilising fine sprays for coverage/deposition on the human body, in conjunction with standard safety showers for rinsing of a victim during decontamination of CBRN materials. As a novel feature miniature high pressure spill-return atomiser are used. It was found that fine sprays decrease the consumption of decontamination liquid that is normally used in practice which has many advantages in practice.

Novel metered aerosol valve

The design and performance of a new valving mechanism for portable pressurized spraying devices is described, where the propellant in the device is a safe gas (so-called compressed gas) propellant rather than the current liquefied gases all of which are either volatile organic compounds or greenhouse gases. The valve sprays a fixed volume of liquid when the spraying actuator is depressed, as is essential used medical sprays, such as pressurized metered dose inhalers and nasal sprays, and also for automatic (wall-mounted) aerosol delivery systems for air-fresheners, insecticides and disinfectants. For ‘compressed gas’ aerosol formats, there is no flash vaporization of propellant so that pumping liquid from a metering chamber and atomization to form a spray must be achieved entirely by designing some means of using the pumping action of the gas in the container to act upon the liquid in the metering chamber. The new design utilizes a loosely fitting spherical piston element and a simple arrangement of a concentric housing and a moveable valve stem, such that liquid flow paths between the different elements are automatically closed and opened in the correct time sequence when the valve stem is depressed and released. Spraying data show excellent repeatability of liquid sprayed per pulse throughout the lifetime of device and drop sizes that are acceptable for devices such as air-fresheners and nasal sprays. The valve has only one additional component compared with liquefied gas metered valves and can be straightforwardly injection moulded. As will be explained, previous attempts failed due to expense, complexity and unreliability.

Next generation of consumer aerosol valve design using inert gases

The current global consumer aerosol products such as deodorants, hairsprays, air-fresheners, polish, insecticide, disinfectant are primarily utilised unfriendly environmental propellant of liquefied petroleum gas (LPG) for over three decades. The advantages of the new innovative technology described in this paper are: (i) no butane or other liquefied hydrocarbon gas; (ii) compressed air, nitrogen or other safe gas propellant; (iii) customer acceptable spray quality and consistency during can lifetime; (iv) conventional cans and filling technology. Volatile organic compounds and greenhouse gases must be avoided but there are no flashing propellants replacements that would provide the good atomisation and spray reach. On the basis of the energy source for atomising, the only feasible source is inert gas (i.e. compressed air), which improves atomisation by gas bubbles and turbulence inside the atomiser insert of the actuator. This research concentrates on using ‘bubbly flow’ in the valve stem, with injection of compressed gas into the passing flow, thus also generating turbulence. Using a vapour phase tap in conventional aerosol valves allows the propellant gas into the liquid flow upstream of the valve. However, forcing bubbly flow through a valve is not ideal. The novel valves designed here, using compressed gas, thus achieved the following objectives when the correct combination of gas and liquid inlets to the valve, and the type and size of atomiser ‘insert’ were derived: Produced a consistent flow rate and drop size of spray throughout the life of the can, compatible with the current conventional aerosols that use LPG: a new ‘constancy’ parameter is defined and used to this end. Obtained a discharge flow rate suited to the product to be sprayed; typically between 0.4 g/s and 2.5 g/s. Attained the spray droplets size suited to the product to be sprayed; typically between 40 µm and 120 µm.

Enhanced Gas Recovery by CO2 Injection and Sequestration: Effect of Connate Water Salinity on Displacement Efficiency

As natural gas continues to gain widespread usage as a source of cleaner and efficient fossil fuel, while greenhouse gas emission is attracting environmental consequences, the need for a viable method to enhance gas recovery and curtail greenhouse gas emissions, is paramount. The technique of injecting CO2 for Enhanced Gas Recovery (EGR) is deemed one of the efficient methods for simultaneously storing man-made CO2 emissions and improving additional natural gas recovery from depleted gas fields, provided that the gas miscibility in situ (mixing) can be reduced. This can be achieved by a better understanding of the mechanisms of displacement and the factors that affect them, hence providing vital information for further studies aimed at a wider and robust field scale application and establish the economic viability of the process. Connate water saturation and salinities are vital properties of the reservoir and their influence on the displacement efficiency cannot be overemphasised. This experimental study determines the effect of connate water salinity, in sandstone samples, on the displacement efficiency during EGR. This study presents the first novel experimental measurement of dispersion of CO2 in CH4 as a function of salinity in consolidated porous media. A laboratory experiment depicting the detailed process of the CO2-CH4 displacement in sandstone core samples at a temperature range of 30-70°C and at a pressure range of 500-2000 psig, was carried in the investigation, at a CO2 injection rate of 0.25 ml/min to evaluate the displacement efficiency. The findings indicated that salinity of the connate water tends to decrease the dispersion of CO2 in CH4 at the stated conditions. This can be attributed to the increase in density of the connate water with increase in salinity, which occupies smaller pore channels within the porous medium. Also, grain diameter measurements were carried out from Scanning Electron Microscopy (SEM) images of the porous media using equivalent circle diameters to establish the characteristic length of mixing of the medium.

Proactive control of cresting in homogeneous oil reservoirs : an experimental study

This paper sets out to investigate experimentally the use of electromagnetic valves in controlling production of water during cresting from homogeneous non-fractured thick-oil and thin-oil reservoirs, based on the principle of capillarity and breakthrough time. A time half the initial breakthrough times was preset for the electromagnetic valve to close. The valve closed almost immediately at the set time thereby shutting oil production temporarily, causing the water and gas height levels to recede by gravity and capillarity with receding reservoir pressure. The efficiency of this technique was compared with an uncontrolled simulation case, in terms of cumulative oil, oil recovery and water produced at the same overall production time. From the results obtained, higher percentages in oil produced and water reduction were observed in the cases controlled proactively, with a 3.6% increase in oil produced and water reduction of 10.0% for thick-oil rim reservoirs, whereas only a small increment in oil produced (0.7%) and a lower water reduction of 1.03% were observed for the thin-oil rim reservoirs. Hence, the effectiveness of the cresting control procedure depends on the oil column height of the reservoir.

Impact pressure distribution in flat fan nozzles for descaling oil wells

The suitability of High pressure nozzles in terms of impact upon targeted surfaces has indicated its effectiveness for the cleaning of oil production tubing scale, which has recently attract wider industrial applications considering its efficiency, ease of operation and cost benefit[1]. In the Oil and gas production, these nozzles are now used for cleaning the scale deposits along the production tubing resulted mainly from salt crystallization due to pressure and temperature drop. Detailed characterizations of flat-fan nozzle in terms of droplet sizes and mean velocities will benefit momentum computations for the axial and radial distribution along the spray width, with the view of finding the best stand-off distance between the target scale and the spray nozzle. While the droplet sizes and the velocities determine the momentum at impact, although measuring droplet sizes has been known to be difficult especially in the high density spray region [2], still laboratory characterization of nozzles provide a reliable data especially avoiding uncontrollable parameters[3].While several research consider break up insensitive to the cleaning performance, this research investigate the experimental data obtained using Phase Doppler Anemometry (PDA) which led to established variation in momentum across the spray width thus, non-uniformity of impact distribution. Validation model was then developed using Fluent which verify the eroded surfaces of material using the flat-fan atomizer to have shown variability in the extent of impact actions due to kinetic energy difference between the center and edge droplets. The study’s findings could be useful in establishing the effect of droplet kinetic energies based on the spray penetration, and will also add significant understanding to the effect of the ligaments and droplets effects along the spray penetration in order to ascertain their momentum impact distribution along the targeted surface.

Fire and Explosion

Compliance with new UK and EU gas safety legislation for chemical processing plants is today a major factor influencing its design and operation. The activities of exploration and production of natural gas are associated with gas transportation, distribution and storage. In industrial, commercial and domestic markets, there are innumerable combusting flows as gas is burned as an end product by customers. In all these activities, accurate assessment of what would happen in the event of an operational or accidental release of gas, particularly where gas dispersion, fire or explosion might be involved, is an essential part of ensuring safe operations.

Estimation of hydraulic anisotropy of unconsolidated granular packs using finite element methods

The effect of particle shape and heterogeneity on hydraulic anisotropy of unconsolidated granular packs is hereby investigated. Direct simulation was carried out on synthetically generated spherical, aspherical, ellipsoidal (aspect ratio of 2 and 3) and lenticular samples. Single phase Stokes equation was solved on models discretised on finite element geometries and hydraulic permeability computed in the horizontal and vertical directions to estimate the degree of anisotropy.The spherical and aspherical packs with varying degrees of particle shapes and heterogeneities are virtually isotropic. Ellipses with aspect ratios 2 and 3 have higher anisotropy ratios compared to the spherical and aspherical geometries while the lenticular geometry is the most anisotropic. This is attributable to the preferential alignment of the grains in the horizontal flow direction during random dynamic settling under gravity.

Fine Sprays for Disinfection within Healthcare

Problems exist worldwide with Hospital Acquired Infections (HAIs). The Spray Research Group (SRG) have been working with relevant industries in developing a product which can provide a delivery system for treatment chemicals for surfaces, including the design and testing of a novel Spill-Return Atomiser (SRA) for this purpose. A comprehensive description of this atomiser has already been given. This paper reports on a new application of this atomiser and discusses the problem of spray coating for disinfection that has been considered very little in previous work. The related spray coating performance tests in developing the product are thus provided. The experimental work includes determining the required spray duration and the coverage area produced by different sprays, including the analysis of the effects of atomiser positions, configurations, and the required number of atomisers. Comparison is made with the efficacy of an ultrasonic gas atomiser that is currently used for this purpose. The investigat...