Effervescent Atomizer for Atomization of Suspensions Containing Large Particles (original) (raw)
Related papers
2008
A single-hole effervescent atomizer spraying light heating oil (LHO) with air as atomizing medium in "outside-in" gas injection configuration was studied using PIV-PLIF. Influence of operation conditions and atomizer internal design on 2D droplet velocity field, liquid phase concentration and liquid flux in the spray was investigated. Inlet pressure and gas-to-liquidratio (GLR) were varied. Several design parameters were modified: size and number of aeration holes, their location, diameter of mixing chamber and discharge orifice shape. Increase of GLR in examined range 2-10 % leads to increase of the droplet velocity in entire radial profile but particularly near the spray axis and to decrease of spray cone half-angle for all atomizer configurations. Increase in atomization pressure in the range 0.1-0.5 MPa causes increase of velocity through all radial profile and indistinctive expansion or reduction of the halfangle depending on atomizer design. The spray cone half-angle ranges 8.8° to 14.6° for all measured configurations and operation conditions. The half-angle increases with: reduction of exit orifice length/diameter ratio, enlargement of aeration area, decrease of aeration hole size and decrease in mixing chamber length. Influence of aeration chamber diameter is not consistent. Influence of atomizer geometry on droplet velocity distribution is reasonable.
Study of cold spray and combustion stability of effervescent atomizer
IOP Conference Series: Materials Science and Engineering
In the present work, an effervescent atomization spray system has been built with plain-orifice atomizer powered by (water / diesel fuel) and air as atomizing gas in the "insideout" gas injection configuration. The investigation shows the influence of operation and design parameters on the spray cone angle, liquid mass distribution throughout the spray, flame blowoff and flame length. The gas to liquid mass ratio (GLR) varies from 0.3% to 15%, the liquid mass flow rate varies from 0.5 to 10 g/s and the operating pressure varies from 1 to 6 bar. The results show that spray cone angles lie in the range of 15-22º for all gas to liquid ratios, length to diameter ratios and operating pressures. Liquid mass distribution at different axial distances downstream of the atomizer becomes more uniform at lower (L/D) ratio and higher gas to liquid ratio. Increasing (A/F) ratio leads to decreasing flame length. Moreover, an empirical correlation of cone angle with operating and design parameters has been developed.
Applied Thermal Engineering, 2016
The present paper provides an experimental study and optimization of multi-hole effervescent atomizers for industrial burners using oil-based fossil, bio-or waste fuels with prospects of emission reduction. Several multihole nozzles were designed based on our previous work. We probed the spray quality by Phase-Doppler anemometry. 3-D plots of Sauter mean diameter and mean droplet velocity demonstrate their spatial distribution within the spray. The effect of geometrical and operational factors on the spray is discussed. Droplet sizevelocity correlations as well as the size and velocity distributions are presented, and differences are found against other investigations. A spray macrostructure is photographically observed and spray cone angles of the multihole nozzles are analysed. An internal two-phase flow is estimated using the Baker's map for horizontal twophase flow. Our previous two-phase flow visualizations suggested a liquid-gas gravitational separation when the multi-hole atomizer operated horizontally. This issue is addressed here; the results of spray heterogeneity measurements document that fuel flow rates through individual exit holes differ significantly. This difference spans between 0 and 70% depending on the nozzle design and flow regime. Effervescent sprays are unsteady under some operating conditions; spray unsteadiness was detected at low pressure and low gas-to-liquid-ratios.
Characteristics of spray angle for effervescent-swirl atomizers
Chemical Engineering and Processing: Process Intensification, 2015
This paper draws a link between the liquid viscosity and the spray angle for effervescent and effervescent-swirl atomizers. The spray angle determines the dispersion and coverage area of the resultant sprays. The swirling the gas-liquid mixture in atomizer led to a significant increase of the spray cone angle at low gas to liquid ratio by mass. Additionally, the orifice shape plays an important role in obtaining the spray angle. The highest values of spray angle has occurred during atomization using profiled orifice. Mathematical analysis shows that spray angle depends on the liquid viscosity, the gas and liquid flow rates and the construction of the atomizer. The data obtained are very important from point of view of the design of atomizers and coverage area of spray. 2015 Elsevier B.V. All rights reserved.
Experimental Investigations on Spray Characteristics in Twin-Fluid Atomizer
Procedia Engineering, 2011
A twin-fluid atomizer was designed and developed for fuel atomization. The droplet characteristic in the spray which was produced with the atomizer was investigated experimentally. Air flow induced in the atomizer causes a pressure reduction, hence the fuel is sucked into the atomizer. The mixture flow of air and liquid caused the atomization downstream due to the turbulence. In the twin-fluid atomizer, atomization is attained by injecting an air stream at tip of the liquid inlet port. In this research, the test liquid supply pressure was kept constant and the air flow rate through the atomizer was varied over a range of air supply pressure to obtain the variation in air liquid mass flow ratio (ALR) from 0.2 to 2.7. The results revealed that the air assisted atomizer had a capability to inject the test liquid in the range of the rates of 0.0019-0.00426 kg/s, with the use of air pressure supplied from 68.9 to 689 kPa. The images of the spray were obtained with a shadowgraph technique and analyzed to obtain the particle size and its distribution. Droplet size from twin-fluid atomizer had various sizes in the range of about 17-200 m. The atomizer can be applied for aerosol and combustion purposes.
In this work an advanced atomizer concept to control the spray formation for heterogeneous spray combustion is investigated. The objective is to address the spray structure that preserves the flame height and modifies the width of the flame. The atomizer concept for formation of a modified spray combines a swirling liquid film generation that is atomized by an external swirling gas flow. To investigate the main characteristics of the combined atomizer, experiments and numerical simulations of the flow operation with different geometric nozzle parameters (number of gas holes) and process parameters (flow rate of liquid and gas) as well as liquid properties are carried out to produce a modified, enlarged and steady spray of small droplets. In this work, three different liquids (water without and with 40% and 60% weight of glycerol) are used as the liquid phase and air as the gas phase. In the simulations, the multiphase flow is modeled by an Eulerian-Lagrangian approach with two-way c...
Spray structure of a pressure-swirl atomizer for combustion applications
EPJ Web of Conferences, 2012
In the present work, global as well as spatially resolved parameters of a spray produced by a pressure-swirl atomizer are obtained. Small pressure-swirl atomizer for aircraft combustion chambers was run on a newly designed test bench with Jet A-1 kerosene type aviation fuel. The atomizer was tested in four regimes based on typical operation conditions of the engine. Spray characteristics were studied using two optical measurement systems, Particle Image velocimetry (PIV) and Phase-Doppler Particle Analyzer (P/DPA). The results obtained with P/DPA include information about Sauter Mean Diameter of droplets and spray velocity profiles in one plane perpendicular to the spray axis. Velocity magnitudes of droplets in an axial section of the spray were obtained using PIV. The experimental outputs also show a good confirmation of velocity profiles obtained with both instruments in the test plane. These data together will elucidate impact of the spray quality on the whole combustion process, its efficiency and exhaust gas emissions. Pressure-swirl atomizers as relatively old type of atomizing devices are nowadays often being replaced in many applications by twin-fluid atomizers. But they are still very common parts of present combustion systems mainly for low power demands. Their popularity is based on simple design and operation without additional expensive devices that could lead to unwanted increase of weight in mobile applications and also to reduction of reliability, which are important factors not only in aircraft industry. Research works focused on improvement of atomization characteristics of the pressure-swirl atomizers are persistent despite long-lasting history of their development and utilization in many industrial sectors. Today research effort stems from changes in the legislative, reflects more frequent usage of less refined fuels and answers requirements for more efficient combustion devices. In general, a swirl-flow of the liquid in a pressure-swirl atomizer is induced by feeding the liquid into a swirl chamber through one or several tangential ports, that give it high angular velocity, thereby creating an air-cored vortex. In this manner, the air-core blocks a part of the nozzle outlet orifice. Under both axial and radial forces emerges the fuel through this orifice in the form of a hollow conical sheet. As the sheet expands, its thickness decreases and it soon becomes unstable and disintegrates into ligaments and then drops in the form of a well-defined hollow-cone spray. Disintegration of the sheet depends mainly on the liquid discharge velocity and thus on the liquid injection pressure. Description of the spray development with increasing injection pressure is presented, for
A visual study on the spray of gas-liquid atomizer
2014
A Visual investigation of spray cone angle for different air-blast atomizers and flow conditions is described. Liquid jets are exposed to high gas stream with specific relative angle. Using high speed camera, spray cone angle over a range of Reynolds number 4×10 to 9×10 and Weber number 1 to 140 is studied, followed by laser-based diagnosis of particle distribution and Sauter mean diameter. The results show that for high Reynolds and Weber number, the cone angle is independent of flow condition, and is only dependent on geometry of atomizer, including orifice diameter with significant effect on cone angle, Sauter mean diameter and particle distribution.
Surface and Coatings Technology, 2016
This work presents the nanostructured coating formation using suspension thermal spraying through the HVOF torch. The nanostructured coating formation requires nanosize powder particles to be injected inside a thermal spray torch using liquid feedstock. The liquid feedstock needs to be atomized when injected into the high-velocity oxygen fuel (HVOF) torch. This paper presents the effects of angular injection and effervescent atomization of the liquid feedstock on gas and droplet dynamics, vaporization rate, and secondary breakup in the high-velocity suspension flame spray (HVSFS) process. Different angular injections are tested to obtain the optimum value of the angle of injection. Moreover, effervescent atomization technique based on twin-fluid injection has been studied to increase the efficiency of the HVSFS process. Different solid nanoparticle concentrations in suspension droplets are considered. In angular injection the droplets are injected into the core of the combustion zone; this immediately evaporates the droplets, and evaporation is completed within the torch. The value of 10°-15°i s selected as the optimal angle of injection to improve the gas and droplet dynamics inside the torch, and to avoid the collision with the torch's wall. The efficiency of the effervescent atomization can be enhanced by using high gas-to-liquid mass flow rate ratio, to increase the spray cone angle for injecting the suspension liquid directly into the combustion flame. It is also found that the increment in the nanoparticle concentration has no considerable effects on the droplet disintegration process. However, the location of evaporation is significantly different for homogeneous and non-homogeneous droplets.
Applied Sciences
The thermal usage of liquid fuels implies their combustion, which is a process strongly influenced by the performance of the atomizer, which disrupts the fuel into drops of the required sizes. The spray quality of the twin-fluid atomizers with internal mixing (IM-TFA) is primarily influenced by the two-phase flow pattern inside the mixing chamber. We studied the performance of the four types of the IM-TFA nozzles by the optical diffraction system (Malvern Spraytec) to answer the question of how the mixing chamber design influences the spray quality at low atomizing gas consumption. We tested the effervescent atomizer in outside-in-liquid (OIL) and outside-in-gas (OIG) configurations, the Y-jet nozzle and new nozzle design, and the CFT atomizer when spraying model liquids with the viscosities comparable to the common fuels (μ=60and143 mPa· s). We found that the effervescent atomizer performance was strongly influenced by the configuration of the inlet ports. Although the OIL configur...