Effects of Fluid Properties on Spray Characteristics of a Flow-Blurring Atomizer

In order to understand the reasons for the apparent benefits of using a flow-blurring (FB) atomizer in a combustion system, it is necessary to first examine fundamental spray characteristics under non-reacting conditions. Previous work on FB atomizers, however, has mostly involved only water and a relatively narrow range of parameters. In this study, a phase Doppler anemometry instrument was used to characterize FB atomizer sprays and determine the effects of varying surface tension and viscosity of the liquid. Operating at room pressure and temperature (i.e., a “cold spray”), droplet sizes and velocities were measured for water, a water/surfactant mixture (lower surface tension), a water/glycerol mixture (higher viscosity), and glycerol (much higher viscosity). For all of the tested fluids, with the exception of pure glycerol, the FB atomizer produced small droplets (below 50 μm) whose size did not vary significantly in the radial or axial direction, particularly above a characteristic distance from the atomizer exit. Results show that the spray is essentially unaffected by a 4.5x decrease in surface tension or a 7x increase in viscosity, and that Sauter mean diameter (SMD) only increased by approximately a factor of three when substituting glycerol (750x higher viscosity) for water. The results suggest that the FB atomizer can effectively atomize a wide range of liquids, making it a useful fuel-flexible atomizer for combustion applications.

Download Full-text

Comparison of Gas-Oil and Bio-Oil Spray Performance for Use in a Gas Turbine

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Education; Electric Power; Manufacturing Materials and Metallurgy ◽

10.1115/gt2010-23485 ◽

2010 ◽

Cited By ~ 2

Author(s):

Andrew P. Crayford ◽

Philip J. Bowen ◽

Peter J. Kay ◽

Hannes Laget

Keyword(s):

Gas Turbine ◽

Full Scale ◽

Operating Conditions ◽

Gas Oil ◽

Spray Characteristics ◽

Spray Structure ◽

Fuel Delivery ◽

Bio Oil ◽

Fluid Properties ◽

Droplet Sizes

This study forms part of an ongoing program to investigate the feasibility of substituting a bio-oil for gas-oil in gas turbine applications. In this paper, the influence of the change of fluid properties on spray characteristics is presented and analyzed. It was not feasible to characterize the spray at full-scale operating conditions, and so a scaling methodology was adopted using published correlations. The study was conducted in three stages; a scaled nozzle was selected utilizing a published correlation to ensure the spray characteristics match the critical characteristics of the full-scale nozzle. The scaled nozzle was then characterized with a gas-oil as a benchmark for comparison with the bio-oil tests. Finally bio-oil tests were conducted at elevated fuel preheat temperatures and the spray characteristics compared to the benchmark case. The objective of the program was to provide an insight into the effect of fuel preheat on spray characteristics. The results of this program helped determine scaled operating conditions for a subsequent atmospheric combustion program, not presented in this paper. The spray characterization was conducted in the atmospheric spray rig (ASR) located at Cardiff University’s GTRC, at Port Talbot, UK. The experiments presented were conducted using bio-oil at elevated fuel preheat temperatures. The spray structure and mean droplet sizes are measured for a bio-oil at various initial pre-heat temperatures and compared with the benchmark gas-oil case. Operating conditions were chosen to maintain an equivalent thermal load of approximately 1.5 MW. Good quality PDA data were recorded for all cases and demonstrated that primary spray characteristics for bio-oil could be optimized and matched to those of gas-oil utilizing the same fuel delivery system. This was achieved by implementing a fuel pre-heat of 80 °C, thereby changing the delivery conditions of the bio-oil.

Download Full-text

Development of Glycerin/Chitosan-Based Fluids for Stationary and Mobile Hydraulic Drives

10.1115/fpmc2021-68089 ◽

2021 ◽

Author(s):

Malte Otten ◽

Deniz Bulutcu ◽

Ludger Frerichs

Keyword(s):

Laboratory Tests ◽

Test Bench ◽

Hydraulic Fluid ◽

Hydraulic Systems ◽

Hydraulic Test ◽

Wide Range ◽

Fluid Properties ◽

Endurance Tests ◽

Water Glycerol ◽

Further Development

Abstract A hydraulic fluid based on water, glycerol and the thickener chitosan was developed in preliminary tests at Technische Universität Braunschweig. In terms of fluid properties, the fluid is comparable to those of conventional fluids. Due to the promising properties of the fluid, further development of the fluid is now being worked on. The focus is on further development for practical use in mobile hydraulic systems, e.g. in agricultural and forestry machinery. The aim here is to optimize various fluid variants for different applications and to define the possible range of uses in general. This paper presents interim results from the development of the fluids and the investigations of the fluids in a wide range of laboratory tests and endurance tests in a hydraulic test bench.

Download Full-text

Enhancing Water and Oil Repellency of Teflon Surface By Imparting Micro-Rough Structures Using Simple One-Step

Science Journal of University of Zakho ◽

10.25271/2017.5.3.386 ◽

2017 ◽

Vol 5 (3) ◽

pp. 266

Author(s):

Khedir R. Khedir

Keyword(s):

Surface Tension ◽

Work Of Adhesion ◽

Organic Liquids ◽

Particle Sizes ◽

Sliding Angle ◽

Wide Range ◽

Water Glycerol ◽

One Step ◽

Micro Structures ◽

Inexpensive Technique

In this work, an easy one-step and inexpensive technique of mechanical wet sanding was used to impart micro structures into the Teflon surface that promotes super repellent properties toward water and the two moderate low surface tension organic liquids. Sandpapers with a wide range of grit sizes 60-1000, with associated particle sizes of 256-10 µm, were used to obtain physical modification of the Teflon surface. The roughened Teflon surface with the sandpaper of 400 grit size showed super repellency toward water, glycerol, and ethylene glycol with CAs as high as 158°, 150°, and 142°, respectively, as well as the low sliding angle of less than 2°, 5°, and 15°, respectively. The obtained results and the effect of roughness were explained in terms of both fundamental wetting models of Wenzel and Cassie-Baxter. The effect of a decrease in liquid surface tension on the length scale of imparted geometries and consequent wetting state was also concluded. Finally, the work of adhesion for the tested liquids while on the roughened Teflon surfaces were also determined using both Young-Dupre relation and the liquid’s SAs.

Download Full-text

Some Experiments on Packed-Bed Drying

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1973_187_136_02 ◽

1973 ◽

Vol 187 (1) ◽

pp. 515-521 ◽

Cited By ~ 2

Author(s):

D. R. Oliver ◽

D. L. Clarke

Keyword(s):

Surface Tension ◽

Packed Bed ◽

Lower Surface ◽

Major Effect ◽

Spherical Particles ◽

Drying Rate ◽

Experimental Conditions ◽

Wide Range ◽

Drying Rates ◽

Thermal Conductivities

Drying equipment is described in which streams of air of accurately-controlled temperature and humidity may be passed over the surface of a packed bed. The materials used in the beds are sieved spherical particles of copper, glass and polystyrene whilst the liquids are water, methanol and a series of organic solvents. Experiments are described in which the effect of physical variables on drying rate is measured. Surface tension is shown to have a major effect on the shape of drying rate curves; under the experimental conditions water is the only liquid for which the rate of drying during the constant-rate period is equal to that from a free liquid surface. The equivalent period for liquids of lower surface tension corresponds to a distinctly lower drying rate. Possible reasons for this behaviour are discussed. An increase in liquid viscosity causes reduction in drying rate, but only when the rate of drying is itself high. The effect of using solids of differing thermal conductivities is investigated. At high drying rates, increasing thermal conductivity produces increasing drying rate. Surprisingly a mixed bed (e.g. of copper and glass) often dries faster than beds of the constituent materials alone. Split beds are also used (beds of which the halves are of different materials). For these beds it is possible to observe the growth of dry patches on the surface of the beds and the manner in which liquid appears to migrate across the interface between the particles of the two halves. The temperature distribution across the interface is shown to be abnormal in part of the drying cycle. A conclusion which may be drawn from the work is that it is often an advantage, from the drying standpoint, to have particles that have either a wide range of thermal conductivities or a wide range of particle sizes.

Download Full-text

Some Experiments on Packed-Bed Drying

Proceedings of the Institution of Mechanical Engineers ◽

10.1243/pime_proc_1973_187_043_02 ◽

1973 ◽

Vol 187 (1) ◽

pp. 515-521

Author(s):

D. R. Oliver ◽

D. L. Clarke

Keyword(s):

Surface Tension ◽

Packed Bed ◽

Lower Surface ◽

Major Effect ◽

Spherical Particles ◽

Drying Rate ◽

Experimental Conditions ◽

Wide Range ◽

Drying Rates ◽

Thermal Conductivities

Drying equipment is described in which streams of air of accurately-controlled temperature and humidity may be passed over the surface of a packed bed. The materials used in the beds are sieved spherical particles of copper, glass and polystyrene whilst the liquids are water, methanol and a series of organic solvents. Experiments are described in which the effect of physical variables on drying rate is measured. Surface tension is shown to have a major effect on the shape of drying rate curves; under the experimental conditions water is the only liquid for which the rate of drying during the constant-rate period is equal to that from a free liquid surface. The equivalent period for liquids of lower surface tension corresponds to a distinctly lower drying rate. Possible reasons for this behaviour are discussed. An increase in liquid viscosity causes reduction in drying rate, but only when the rate of drying is itself high. The effect of using solids of differing thermal conductivities is investigated. At high drying rates, increasing thermal conductivity produces increasing drying rate. Surprisingly a mixed bed (e.g. of copper and glass) often dries faster than beds of the constituent materials alone. Split beds are also used (beds of which the halves are of different materials). For these beds it is possible to observe the growth of dry patches on the surface of the beds and the manner in which liquid appears to migrate across the interface between the particles of the two halves. The temperature distribution across the interface is shown to be abnormal in part of the drying cycle. A conclusion which may be drawn from the work is that it is often an advantage, from the drying standpoint, to have particles that have either a wide range of thermal conductivities or a wide range of particle sizes.

Download Full-text

DECOUPLING THE EFFECT OF SURFACE TENSION AND VISCOSITY ON SPRAY CHARACTERISTICS UNDER DIFFERENT AMBIENT PRESSURES: NEAR-NOZZLE BEHAVIOR AND MACROSCOPIC CHARACTERISTICS

Atomization and Sprays ◽

10.1615/atomizspr.2019030936 ◽

2019 ◽

Vol 29 (7) ◽

pp. 629-654

Author(s):

Zehao Feng ◽

Shangqing Tong ◽

Chenglong Tang ◽

Cheng Zhan ◽

Keiya Nishida ◽

...

Keyword(s):

Surface Tension ◽

Spray Characteristics ◽

Effect Of Surface

Download Full-text

Towards a methodology for the characterisation of the fabric of wet clays using X-ray scattering

E3S Web of Conferences ◽

10.1051/e3sconf/20199201005 ◽

2019 ◽

Vol 92 ◽

pp. 01005

Author(s):

Georgios Birmpilis ◽

Reza Ahmadi-Naghadeh ◽

Jelke Dijkstra

Keyword(s):

Materials Science ◽

Measurement Techniques ◽

Invasive Technique ◽

Colloidal Systems ◽

Characteristic Distance ◽

X Ray ◽

Hydrophobic Coating ◽

X Ray Scattering ◽

Wide Range ◽

Ray Scattering

X-ray scattering is a promising non-invasive technique to study evolving nano- and micromechanics in clays. This study discusses the experimental considerations and a successful method to enable X-ray scattering to study clay samples at two extreme stages of consolidation. It is shown that the proposed sample environment comprising flat capillaries with a hydrophobic coating can be used for a wide range of voids ratios ranging from a clay suspension to consolidated clay samples, that are cut from larger specimens of reconstituted or natural clay. The initial X-ray scattering results using a laboratory instrument indicate that valuable information on, in principal evolving, clay fabric can be measured. Features such as characteristic distance between structural units and particle orientations are obtained for a slurry and a consolidated sample of kaolinite. Combined with other promising measurement techniques from Materials Science the proposed method will help advance the contemporary understanding on the behaviour of dense colloidal systems of clay, as it does not require detrimental sample preparation

Download Full-text

Understanding Micro-Droplet Interface Bilayers for Developing Bioinspired Sensors

Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting ◽

10.1115/smasis2013-3134 ◽

2013 ◽

Author(s):

Guru Venkatesan ◽

Andy Sarles

Keyword(s):

Water Droplet ◽

Morphological Changes ◽

High Surface ◽

High Surface Area ◽

Material System ◽

Modes Of Operation ◽

New Class ◽

Wide Range ◽

Droplet Sizes ◽

The Stability

Droplet-based biomolecular arrays form the basis for a new class of bioinspired material system, whereby decreasing the sizes of the droplets and increasing the number of droplets can lead to higher functional density for the array. In this paper, we report on a non-microfluidic approach to form and connect nanoliter-to-femtoliter, lipid-coated aqueous droplets in oil to form micro-droplet interface bilayers (μDIBs). Two different modes of operation are reported for dispensing a wide range of droplet sizes (2–200μm radius). Due to the high surface-area-to-volume ratios of microdroplets at these length scales, droplet shrinking is prominent, which affects the stability and lifetime of the bilayer. To better quantify these effects, we measure the shrinkage rates for 8 different water droplet/oil compositions and study the effect of lipid placement and lipid type on morphological changes to μDIBs.

Download Full-text